WorldWideScience

Sample records for early earth evolution

  1. The Earth's early evolution.

    Science.gov (United States)

    Bowring, S A; Housh, T

    1995-09-15

    The Archean crust contains direct geochemical information of the Earth's early planetary differentiation. A major outstanding question in the Earth sciences is whether the volume of continental crust today represents nearly all that formed over Earth's history or whether its rates of creation and destruction have been approximately balanced since the Archean. Analysis of neodymium isotopic data from the oldest remnants of Archean crust suggests that crustal recycling is important and that preserved continental crust comprises fragments of crust that escaped recycling. Furthermore, the data suggest that the isotopic evolution of Earth's mantle reflects progressive eradication of primordial heterogeneities related to early differentiation.

  2. Accretion and early evolution of Earth

    DEFF Research Database (Denmark)

    Saji, Nikitha Susan

    -stage impacts had to play in determining the bulk composition as well as pace of the chemical dierentiation and internal dynamics of terrestrial planets - is preserved in the form of isotopic signatures in some of the oldest terrestrial and extraterrestrial samples available to us. A potential means to unravel...... this is by the application of Nd-isotope systematics as the coupled 146;147Sm - 143;142Nd decay system enables the study of chronology of planetary silicate mantles while the stable Nd-isotopes help track the origin and early transport of material. Deciphering this information, however, requires the analytical capability...... in solar system materials is found to be related to selective thermal processing of dust in the early nebula given the correlation observed for these eects with Fe-peak neutron-rich isotope anomalies, whose origin is attributed to distinct nucleosnythetic sites other than classical s-, r- or p...

  3. Hydrogenation of iron in the early stage of Earth's evolution

    Science.gov (United States)

    Iizuka-Oku, Riko; Yagi, Takehiko; Gotou, Hirotada; Okuchi, Takuo; Hattori, Takanori; Sano-Furukawa, Asami

    2017-01-01

    Density of the Earth's core is lower than that of pure iron and the light element(s) in the core is a long-standing problem. Hydrogen is the most abundant element in the solar system and thus one of the important candidates. However, the dissolution process of hydrogen into iron remained unclear. Here we carry out high-pressure and high-temperature in situ neutron diffraction experiments and clarify that when the mixture of iron and hydrous minerals are heated, iron is hydrogenized soon after the hydrous mineral is dehydrated. This implies that early in the Earth's evolution, as the accumulated primordial material became hotter, the dissolution of hydrogen into iron occurred before any other materials melted. This suggests that hydrogen is likely the first light element dissolved into iron during the Earth's evolution and it may affect the behaviour of the other light elements in the later processes.

  4. A Hot Climate on Early Earth: Implications to Biospheric Evolution

    Science.gov (United States)

    Schwartzman, D. W.; Knauth, L. P.

    2009-12-01

    There is now robust evidence for a much warmer climate on the early Earth than now. Both oxygen and silicon isotopes in sedimentary chert and the compelling case for a near constant isotopic oxygen composition of seawater over geologic time support thermophilic surface temperatures until about 1.5-2 billion years ago, aside from a glacial episode in the early Proterozoic. This temperature scenario has important implications to biospheric evolution, including a temperature constraint that held back the emergence of major organismal groups, starting with phototrophs. A geophysiology of biospheric evolution raises the potential of similar coevolutionary relationships of life and its environment on Earth-like planets around Sun-like stars.

  5. The origin and early evolution of life on earth

    Science.gov (United States)

    Oro, J.; Miller, Stanley L.; Lazcano, Antonio

    1990-01-01

    Results of the studies that have provided insights into the cosmic and primitive earth environments are reviewed with emphasis on those environments in which life is thought to have originated. The evidence bearing on the antiquity of life on the earth and the prebiotic significance of organic compounds found in interstellar clouds and in primitive solar-system bodies such as comets, dark asteroids, and carbonaceous chondrites are assessed. The environmental models of the Hadean and early Archean earth are discussed, as well as the prebiotic formation of organic monomers and polymers essential to life. The processes that may have led to the appearance in the Archean of the first cells are considered, and possible effects of these processes on the early steps of biological evolution are analyzed. The significance of these results to the study of the distribution of life in the universe is evaluated.

  6. Teaching about the Early Earth: Evolution of Tectonics, Life, and the Early Atmosphere

    Science.gov (United States)

    Mogk, D. W.; Manduca, C. A.; Kirk, K.; Williams, M. L.

    2007-12-01

    The early history of the Earth is the subject of some of the most exciting and innovative research in the geosciences, drawing evidence from virtually all fields of geoscience and using a variety of approaches that include field, analytical, experimental, and modeling studies. At the same time, the early Earth presents unique opportunities and challenges in geoscience education: how can we best teach "uncertain science" where the evidence is either incomplete or ambiguous? Teaching about early Earth provides a great opportunity to help students understand the nature of scientific evidence, testing, and understanding. To explore the intersection of research and teaching about this enigmatic period of Earth history, a national workshop was convened for experts in early Earth research and undergraduate geoscience education. The workshop was held in April, 2007 at the University of Massachusetts at Amherst as part of the On the Cutting Edge faculty professional development program. The workshop was organized around three scientific themes: evolution of global tectonics, life, and the early atmosphere. The "big scientific questions" at the forefront of current research about the early Earth were explored by keynote speakers and follow-up discussion groups: How did plate tectonics as we know it today evolve? Were there plates in the Hadean Eon? Was the early Earth molten? How rapidly did it cool? When and how did the atmosphere and hydrosphere evolve? How did life originate and evolve? How did all these components interact at the beginning of Earth's history and evolve toward the Earth system we know today? Similar "big questions" in geoscience education were addressed: how to best teach about "deep time;" how to help students make appropriate inferences when geologic evidence is incomplete; how to engage systems thinking and integrate multiple lines of evidence, across many scales of observation (temporal and spatial), and among many disciplines. Workshop participants

  7. Evolution of the Early Earth and Its Biosphere

    Science.gov (United States)

    DesMarais, David J.

    1996-01-01

    The history of life on Earth is a rich tapestry of adaptation and innovation which was shaped, at least in part, by the changing surface environment of our planet. To the extent that all rocky planets have followed similar evolutionary paths, studies of our own biosphere can guide us in our search for extraterrestrial life. Understanding the nature, timing, and causes of long-term changes in the global environment is a key objective.

  8. The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

    Science.gov (United States)

    Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

    2015-01-01

    We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

  9. Os isotopes in SNC meteorites and their implications to the early evolution of Mars and Earth

    Science.gov (United States)

    Jagoutz, E.; Luck, J. M.; Othman, D. Ben; Wanke, H.

    1993-01-01

    A new development on the measurement of the Os isotopic composition by mass spectrometry using negative ions opened a new field of applications. The Re-Os systematic provides time information on the differentiation of the nobel metals. The nobel metals are strongly partitioned into metal and sulphide phases, but also the generation of silicate melts might fractionate the Re-Os system. Compared to the other isotopic systems which are mainly dating the fractionation of the alkalis and alkali-earth elements, the Re-Os system is expected to disclose entirely new information about the geochemistry. Especially the differentiation and early evolution of the planets such as the formation of the core will be elucidated with this method.

  10. A model for the evolution of the Earth's mantle structure since the Early Paleozoic

    Science.gov (United States)

    Zhang, Nan; Zhong, Shijie; Leng, Wei; Li, Zheng-Xiang

    2010-06-01

    Seismic tomography studies indicate that the Earth's mantle structure is characterized by African and Pacific seismically slow velocity anomalies (i.e., superplumes) and circum-Pacific seismically fast anomalies (i.e., a globally spherical harmonic degree 2 structure). However, the cause for and time evolution of the African and Pacific superplumes and the degree 2 mantle structure remain poorly understood with two competing proposals. First, the African and Pacific superplumes have remained largely unchanged for at least the last 300 Myr and possibly much longer. Second, the African superplume is formed sometime after the formation of Pangea (i.e., at 330 Ma) and the mantle in the African hemisphere is predominated by cold downwelling structures before and during the assembly of Pangea, while the Pacific superplume has been stable for the Pangea supercontinent cycle (i.e., globally a degree 1 structure before the Pangea formation). Here, we construct a proxy model of plate motions for the African hemisphere for the last 450 Myr since the Early Paleozoic using the paleogeographic reconstruction of continents constrained by paleomagnetic and geological observations. Coupled with assumed oceanic plate motions for the Pacific hemisphere, this proxy model for the plate motion history is used as time-dependent surface boundary condition in three-dimensional spherical models of thermochemical mantle convection to study the evolution of mantle structure, particularly the African mantle structure, since the Early Paleozoic. Our model calculations reproduce well the present-day mantle structure including the African and Pacific superplumes and generally support the second proposal with a dynamic cause for the superplume structure. Our results suggest that while the mantle in the African hemisphere before the assembly of Pangea is predominated by the cold downwelling structure resulting from plate convergence between Gondwana and Laurussia, it is unlikely that the bulk of

  11. Early evolution and dynamics of Earth from a molten initial stage

    Science.gov (United States)

    Louro Lourenço, Diogo; Tackley, Paul J.

    2016-04-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moon-forming impact, together with other sources of heat, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet. Considerable research has been done on magma oceans using simple 1-D models (e.g.: Abe, PEPI 1997; Solomatov, Treat. Geophys. 2007; Elkins-Tanton EPSL 2008). However, some aspects of the dynamics may not be adequately addressed in 1-D and require the use of 2-D or 3-D models. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures (e.g.: de Koker et al., EPSL 2013) can have very important impacts on the classical views of the solidification of magma oceans (Labrosse et al., Nature 2007). The goal of our study is to understand and characterize the influence of melting on the long-term thermo-chemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to model viscous creep of the solid mantle, while parameterizing processes that involve melt as previously done in 1-D models, including melt-solid separation at all melt fractions, the use of an effective diffusivity to parameterize turbulent mixing, coupling to a parameterized core heat balance and a radiative surface boundary condition. These enhancements have been made to the numerical code StagYY (Tackley, PEPI 2008). We present results for the evolution of an Earth-like planet from a molten initial state to present day, while testing the effect of uncertainties in parameters such as melt-solid density differences, surface heat loss and efficiency of turbulent mixing. Our results show rapid cooling and crystallization until the rheological transition then much slower

  12. Coupled orbital-thermal evolution of the early Earth-Moon system with a fast-spinning Earth

    Science.gov (United States)

    Tian, ZhenLiang; Wisdom, Jack; Elkins-Tanton, Linda

    2017-01-01

    Several new scenarios of the Moon-forming giant impact have been proposed to reconcile the giant impact theory with the recent recognition of the volatile and refractory isotopic similarities between Moon and Earth. Two scenarios leave the post-impact Earth spinning much faster than what is inferred from the present Earth-Moon system's angular momentum. The evection resonance has been proposed to drain the excess angular momentum, but the lunar orbit stays at high orbital eccentricities for long periods in the resonance, which would cause large tidal heating in the Moon. A limit cycle related to the evection resonance has also been suggested as an alternative mechanism to reduce the angular momentum, which keeps the lunar orbit at much lower eccentricities, and operates in a wider range of parameters. In this study we use a coupled thermal-orbital model to determine the effect of the change of the Moon's thermal state on the Earth-Moon system's dynamical history. The evection resonance no longer drains angular momentum from the Earth-Moon system since the system rapidly exits the resonance. Whereas the limit cycle works robustly to drain as much angular momentum as in the non-thermally-coupled model, though the Moon's tidal properties change throughout the evolution.

  13. Tidal dissipation in the lunar magma ocean and its effect on the early evolution of the Earth-Moon system

    Science.gov (United States)

    Chen, Erinna M. A.; Nimmo, Francis

    2016-09-01

    The present-day inclination of the Moon reflects the entire history of its thermal and orbital evolution. The Moon likely possessed a global magma ocean following the Moon-forming impact. In this work, we develop a coupled thermal-orbital evolution model that takes into account obliquity tidal heating in the lunar magma ocean. Dissipation in the magma ocean is so effective that it results in rapid inclination damping at semi-major axes beyond about 20 Earth radii (RE), because of the increase in lunar obliquity as the so-called Cassini state transition at ≈30 RE is approached. There is thus a "speed limit" on how fast the Moon can evolve outwards while maintaining its inclination: if it reaches 20 RE before the magma ocean solidifies, any early lunar inclination cannot be maintained. We find that for magma ocean lifetimes of 10 Myr or more, the Earth's tidal quality factor Q must have been >300 to maintain primordial inclination, implying an early Earth 1-2 orders of magnitude less dissipative than at present. On the other hand, if tidal dissipation on the early Earth was stronger, our model implies rapid damping of the lunar inclination and requires subsequent late excitation of the lunar orbit after the crystallization of the lunar magma ocean.

  14. Microbes, Mineral Evolution, and the Rise of Microcontinents-Origin and Coevolution of Life with Early Earth.

    Science.gov (United States)

    Grosch, Eugene G; Hazen, Robert M

    2015-10-01

    Earth is the most mineralogically diverse planet in our solar system, the direct consequence of a coevolving geosphere and biosphere. We consider the possibility that a microbial biosphere originated and thrived in the early Hadean-Archean Earth subseafloor environment, with fundamental consequences for the complex evolution and habitability of our planet. In this hypothesis paper, we explore possible venues for the origin of life and the direct consequences of microbially mediated, low-temperature hydrothermal alteration of the early oceanic lithosphere. We hypothesize that subsurface fluid-rock-microbe interactions resulted in more efficient hydration of the early oceanic crust, which in turn promoted bulk melting to produce the first evolved fragments of felsic crust. These evolved magmas most likely included sialic or tonalitic sheets, felsic volcaniclastics, and minor rhyolitic intrusions emplaced in an Iceland-type extensional setting as the earliest microcontinents. With the further development of proto-tectonic processes, these buoyant felsic crustal fragments formed the nucleus of intra-oceanic tonalite-trondhjemite-granitoid (TTG) island arcs. Thus microbes, by facilitating extensive hydrothermal alteration of the earliest oceanic crust through bioalteration, promoted mineral diversification and may have been early architects of surface environments and microcontinents on young Earth. We explore how the possible onset of subseafloor fluid-rock-microbe interactions on early Earth accelerated metavolcanic clay mineral formation, crustal melting, and subsequent metamorphic mineral evolution. We also consider environmental factors supporting this earliest step in geosphere-biosphere coevolution and the implications for habitability and mineral evolution on other rocky planets, such as Mars.

  15. Evolution of Earth-like Extrasolar Planetary Atmospheres: Assessing the Atmospheres and Biospheres of Early Earth Analog Planets with a Coupled Atmosphere Biogeochemical Model

    Science.gov (United States)

    Gebauer, S.; Grenfell, J. L.; Stock, J. W.; Lehmann, R.; Godolt, M.; von Paris, P.; Rauer, H.

    2017-01-01

    Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O2 concentrations are fixed to values inferred by geological evidence. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles that governed O2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O2, whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis. The O2 bistability found by Goldblatt et al. (2006) is not observed in our calculations likely due to our detailed CH4 oxidation scheme. We calculate increased CH4 with increasing O2 during the Great Oxidation Event. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity of the biosphere that produces O2 is unique. Mixing, CH4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O2 fluxes. Regarding exoplanets, different "states" of O2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases remove O2 that

  16. Evolution of Earth-like Extrasolar Planetary Atmospheres: Assessing the Atmospheres and Biospheres of Early Earth Analog Planets with a Coupled Atmosphere Biogeochemical Model.

    Science.gov (United States)

    Gebauer, S; Grenfell, J L; Stock, J W; Lehmann, R; Godolt, M; von Paris, P; Rauer, H

    2017-01-01

    Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O2 concentrations are fixed to values inferred by geological evidence. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles that governed O2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O2, whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis. The O2 bistability found by Goldblatt et al. ( 2006 ) is not observed in our calculations likely due to our detailed CH4 oxidation scheme. We calculate increased CH4 with increasing O2 during the Great Oxidation Event. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity of the biosphere that produces O2 is unique. Mixing, CH4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O2 fluxes. Regarding exoplanets, different "states" of O2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases remove O2 that

  17. Symbiosis in cell evolution: Life and its environment on the early earth

    Science.gov (United States)

    Margulis, L.

    1981-01-01

    The book treats cell evolution from the viewpoint of the serial endosymbiosis theory of the origin of organelles. Following a brief outline of the symbiotic theory, which holds that eukaryotes evolved by the association of free-living bacteria with a host prokaryote, the diversity of life is considered, and five kingdoms of organisms are distinguished: the prokaryotic Monera and the eukaryotic Protoctista, Animalia, Fungi and Plantae. Symbiotic and traditional direct filiation theories of cell evolution are compared. Recent observations of cell structure and biochemistry are reviewed in relation to early cell evolution, with attention given to the geological context for the origin of eukaryotic cells, the origin of major bacterial anaerobic pathways, the relationship between aerobic metabolism and atmospheric oxygen, criteria for distinguishing symbiotic organelles from those that originated by differentiation, and the major classes of eukaryotic organelles: mitochondria, cilia, microtubules, the mitotic and meiotic apparatuses, and pastids. Cell evolution during the Phanerozoic is also discussed with emphasis on the effects of life on the biosphere

  18. Evolution of Electron Transport Chains During the Anaerobic to Aerobic Transition on Early Earth

    Science.gov (United States)

    Sepúlveda, R.; Ortiz, R.; Holmes, D. S.

    2015-12-01

    Sepulveda, R., Ortiz R. and Holmes DS. Center for Bioinformatics and Genome Biology, Fundacion Ciencia y Vida, and Facultad de Ciencias Biologicas, Universidad Andres Bello, Santiago, Chile.According to several models, life emerged on earth in an anoxic environment where oxygen was not available as a terminal electron acceptor for energy generating reactions. After the Great Oxidation Event (GOE) about 2.4 billion years ago, or perhaps even before the GOE, oxygen became the most widespread and efficient terminal electron acceptor and was accompanied by the evolution of a number of redox proteins that could deliver electrons to reduce oxygen to water. Where did these proteins come from? One hypothesis is that they evolved by the neofunctionalization of previously existing redox proteins that had been used in anaerobic conditions as terminal electron donors to reduce compounds such as perchlorate, nitric oxide or iron. We have used a number of bioinformatic tools to explore a large number of genomes looking for discernable signals of such redeployment of function. A Perl pipeline was designed to detect sequence similarity, conserved gene context, remote homology detection, identification of domains and functional evolution of electron carrier proteins from extreme acidophiles, including the small blue copper protein rusticyanin (involved in FeII oxidation), cytochrome oxidase subunit II and quinol-dependent nitric oxide reductase (qNOR). The protein folds and copper binding sites of rusticyanin are conserved in cytochrome oxidase aa3 subunit II, a protein complex that is responsible for the final passage of electrons to reduce oxygen. Therefore, we hypothesize that rusticyanin, cytochrome oxidase II and qNOR are evolutionarily related. Acknowledgments: Fondecyt 1130683.

  19. Hybrid Differential Evolution Optimisation for Earth Observation Satellite Scheduling with Time-Dependent Earliness-Tardiness Penalties

    Directory of Open Access Journals (Sweden)

    Guoliang Li

    2017-01-01

    Full Text Available We study the order acceptance and scheduling (OAS problem with time-dependent earliness-tardiness penalties in a single agile earth observation satellite environment where orders are defined by their release dates, available processing time windows ranging from earliest start date to deadline, processing times, due dates, sequence-dependent setup times, and revenues. The objective is to maximise total revenue, where the revenue from an order is a piecewise linear function of its earliness and tardiness with reference to its due date. We formulate this problem as a mixed integer linear programming model and develop a novel hybrid differential evolution (DE algorithm under self-adaptation framework to solve this problem. Compared with classical DE, hybrid DE employs two mutation operations, scaling factor adaptation and crossover probability adaptation. Computational tests indicate that the proposed algorithm outperforms classical DE in addition to two other variants of DE.

  20. Earth's early biosphere

    Science.gov (United States)

    Des Marais, D. J.

    1998-01-01

    Understanding our own early biosphere is essential to our search for life elsewhere, because life arose on Earth very early and rocky planets shared similar early histories. The biosphere arose before 3.8 Ga ago, was exclusively unicellular and was dominated by hyperthermophiles that utilized chemical sources of energy and employed a range of metabolic pathways for CO2 assimilation. Photosynthesis also arose very early. Oxygenic photosynthesis arose later but still prior to 2.7 Ga. The transition toward the modern global environment was paced by a decline in volcanic and hydrothermal activity. These developments allowed atmospheric O2 levels to increase. The O2 increase created new niches for aerobic life, most notably the more advanced Eukarya that eventually spawned the megascopic fauna and flora of our modern biosphere.

  1. Life and the evolution of Earth's atmosphere.

    Science.gov (United States)

    Kasting, James F; Siefert, Janet L

    2002-05-10

    Harvesting light to produce energy and oxygen (photosynthesis) is the signature of all land plants. This ability was co-opted from a precocious and ancient form of life known as cyanobacteria. Today these bacteria, as well as microscopic algae, supply oxygen to the atmosphere and churn out fixed nitrogen in Earth's vast oceans. Microorganisms may also have played a major role in atmosphere evolution before the rise of oxygen. Under the more dim light of a young sun cooler than today's, certain groups of anaerobic bacteria may have been pumping out large amounts of methane, thereby keeping the early climate warm and inviting. The evolution of Earth's atmosphere is linked tightly to the evolution of its biota.

  2. Toward understanding early Earth evolution: Prescription for approach from terrestrial noble gas and light element records in lunar soils

    OpenAIRE

    Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.

    2008-01-01

    Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset ...

  3. Earth System Oxygenation: Toward an Integrated Theory of Earth Evolution

    Science.gov (United States)

    Anbar, A. D.

    2015-12-01

    The cause of the progressive oxygenation of Earth's biosphere remains poorly understood. The problem is bounded by the interplay of three irreversible, secular changes: the escape of H to space, which makes the planet more oxidized; the evolution of photoautotrophy - which converts solar energy into redox disequilbrium - and related metabolisms; and the cooling of the planet, which affects the exchange of material between Earth's reduced interior and relatively oxidized surface through a variety of processes. The first of these changes is quantitatively considered elsewhere, and is connected to the other two because H escape depends on atmospheric H2 and CH4 contents. The second of these changes is an area of vigorous research, particularly over the past decade. Important work included efforts to constrain the timing of key evolutionary events using organic geochemical and genomic records, and to understand the timing and tempo of environmental oxidation, particularly preceding the "Great Oxidation Event" (GOE) at ~2.4 Ga. As the community sorts through various debates, evidence is accumulating that the pre-GOE period was a dynamic era of transient "whiffs" of oxidation, most likely due to small amounts of biogenic O2 that appeared as early as ~3.0 Ga. The implication is that O2 sinks generally overwhelmed substantial O2 sources through the first half of Earth history, and that a decrease in sink strength and/or increase in source strength could have resulted in increasing instability of trace pO2 in the runup to the GOE. The most likely sinks are coupled to reductants in Earth's interior, which leads us to the third major change—secular cooling of the planet. It is almost certain that this cooling led to changes in mantle dynamics, rates of plate motion, and melting behaviors, which in turn affected volcanism, crust composition, hydrothermal and metamorphic alteration, ocean nutrient budgets, and recycling at subduction zones. These factors have all been

  4. Helium in Earth's early core

    Science.gov (United States)

    Bouhifd, M. A.; Jephcoat, Andrew P.; Heber, Veronika S.; Kelley, Simon P.

    2013-11-01

    The observed escape of the primordial helium isotope, 3He, from the Earth's interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth's interior have been invoked to account for variations in the 3He/4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth's iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16GPa and 3,000K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal-silicate helium partition coefficients that range between 4.7×10-3 and 1.7×10-2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium, we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.

  5. Evolution of Earth Like Planets

    Science.gov (United States)

    Monroy-Rodríguez, M. A.; Vega, K. M.

    2017-07-01

    In order to study and explain the evolution of our own planet we have done a review of works related to the evolution of Earth-like planets. From the stage of proto-planet to the loss of its atmosphere. The planetary formation from the gas and dust of the proto-planetary disk, considering the accretion by the process of migration, implies that the material on the proto-planet is very mixed. The newborn planet is hot and compact, it begins its process of stratification by gravity separation forming a super dense nucleus, an intermediate layer of convective mantle and an upper mantle that is less dense, with material that emerges from zones at very high pressure The surface with low pressure, in this process the planet expands and cools. This process also releases gas to the surface, forming the atmosphere, with the gas gravitationally bounded. The most important thing for the life of the planet is the layer of convective mantle, which produces the magnetic field, when it stops the magnetic field disappears, as well as the rings of van allen and the solar wind evaporates the atmosphere, accelerating the evolution and cooling of the planet. In a natural cycle of cataclysms and mass extinctions, the solar system crosses the galactic disk every 30 million years or so, the increase in the meteorite fall triggers the volcanic activity and the increase in the release of CO2 into the atmosphere reaching critical levels (4000 billion tons) leads us to an extinction by overheating that last 100 000 years, the time it takes CO2 to sediment to the ocean floor. Human activity will lead us to reach critical levels of CO2 in approximately 300 years.

  6. Mission to Very Early Earth

    Energy Technology Data Exchange (ETDEWEB)

    Hutcheon, I D; Weber, P K; Fallon, S J; Smith, J B; Aleon, J; Ryerson, F J; Harrison, T M; Cavosie, A J; Valley, J W

    2007-03-13

    The Hadean Earth is often viewed as an inhospitable and, perhaps, unlikely setting for the rise of primordial life. However, carbonaceous materials supplied by accreting meteorites and sources of chemical energy similar to those fueling life around modern deep-sea volcanic vents would have been present in abundance. More questionable are two other essential ingredients for life - liquid water and clement temperatures. Did the Hadean Earth possess a hydrosphere and temperate climate compatible with the initiation of biologic activity? If so, the popular model of an excessively hot planetary surface characterized by a basaltic crust, devoid of continental material is invalid. Similarly, establishment of an Hadean hydrosphere prior to the cessation of heavy asteroid bombardment may mean that primitive life could have evolved and then been extinguished, only to rise again. The most effective means of determining the environmental conditions on this young planet is through geochemical analysis of samples retrieved from the Early Earth. While rocks older than 4 billion years (4 Ga) have not been found, individual zircon grains, the detritus of rocks long since eroded away, have been identified with ages as old as 4.4 Ga - only {approx}160 million years younger than the Earth itself. If we can use the geochemical information contained in these unique samples to infer the nature of their source rocks and the processes that formed them, we can place constraints on the conditions prevailing at the Earth's surface shortly after formation. This project utilizes a combined analytical and experimental approach to gather the necessary geochemical data to determine the parameters required to relate the zircons to their parent materials. Mission to Early Earth involves dating, isotopic and chemical analyses of mineral and melt inclusions within zircons and of the zircons themselves. The major experimental activity at LLNL focused on the partitioning of trace elements between

  7. Interplay between solid Earth and biological evolution

    Science.gov (United States)

    Höning, Dennis; Spohn, Tilman

    2017-04-01

    Major shifts in Earth's evolution led to progressive adaptations of the biosphere. Particularly the emergence of continents permitted efficient use of solar energy. However, the widespread evolution of the biosphere fed back to the Earth system, often argued as a cause for the great oxidation event or as an important component in stabilizing Earth's climate. Furthermore, biologically enhanced weathering rates alter the flux of sediments in subduction zones, establishing a potential link to the deep interior. Stably bound water within subducting sediments not only enhances partial melting but further affects the mantle rheology. The mantle responds by enhancing its rates of convection, water outgassing, and subduction. How crucial is the emergence and evolution of life on Earth to these processes, and how would Earth have been evolved without the emergence of life? We here discuss concepts and present models addressing these questions and discuss the biosphere as a major component in evolving Earth system feedback cycles.

  8. Virtual Exploration of Earth's Evolution

    Science.gov (United States)

    Anbar, A. D.; Bruce, G.; Semken, S. C.; Summons, R. E.; Buxner, S.; Horodyskyj, L.; Kotrc, B.; Swann, J.; Klug Boonstra, S. L.; Oliver, C.

    2014-12-01

    Traditional introductory STEM courses often reinforce misconceptions because the large scale of many classes forces a structured, lecture-centric model of teaching that emphasizes delivery of facts rather than exploration, inquiry, and scientific reasoning. This problem is especially acute in teaching about the co-evolution of Earth and life, where classroom learning and textbook teaching are far removed from the immersive and affective aspects of field-based science, and where the challenges of taking large numbers of students into the field make it difficult to expose them to the complex context of the geologic record. We are exploring the potential of digital technologies and online delivery to address this challenge, using immersive and engaging virtual environments that are more like games than like lectures, grounded in active learning, and deliverable at scale via the internet. The goal is to invert the traditional lecture-centric paradigm by placing lectures at the periphery and inquiry-driven, integrative virtual investigations at the center, and to do so at scale. To this end, we are applying a technology platform we devised, supported by NASA and the NSF, that integrates a variety of digital media in a format that we call an immersive virtual field trip (iVFT). In iVFTs, students engage directly with virtual representations of real field sites, with which they interact non-linearly at a variety of scales via game-like exploration while guided by an adaptive tutoring system. This platform has already been used to develop pilot iVFTs useful in teaching anthropology, archeology, ecology, and geoscience. With support the Howard Hughes Medical Institute, we are now developing and evaluating a coherent suite of ~ 12 iVFTs that span the sweep of life's history on Earth, from the 3.8 Ga metasediments of West Greenland to ancient hominid sites in East Africa. These iVFTs will teach fundamental principles of geology and practices of scientific inquiry, and expose

  9. Early bioenergetic evolution

    Science.gov (United States)

    Sousa, Filipa L.; Thiergart, Thorsten; Landan, Giddy; Nelson-Sathi, Shijulal; Pereira, Inês A. C.; Allen, John F.; Lane, Nick; Martin, William F.

    2013-01-01

    Life is the harnessing of chemical energy in such a way that the energy-harnessing device makes a copy of itself. This paper outlines an energetically feasible path from a particular inorganic setting for the origin of life to the first free-living cells. The sources of energy available to early organic synthesis, early evolving systems and early cells stand in the foreground, as do the possible mechanisms of their conversion into harnessable chemical energy for synthetic reactions. With regard to the possible temporal sequence of events, we focus on: (i) alkaline hydrothermal vents as the far-from-equilibrium setting, (ii) the Wood–Ljungdahl (acetyl-CoA) pathway as the route that could have underpinned carbon assimilation for these processes, (iii) biochemical divergence, within the naturally formed inorganic compartments at a hydrothermal mound, of geochemically confined replicating entities with a complexity below that of free-living prokaryotes, and (iv) acetogenesis and methanogenesis as the ancestral forms of carbon and energy metabolism in the first free-living ancestors of the eubacteria and archaebacteria, respectively. In terms of the main evolutionary transitions in early bioenergetic evolution, we focus on: (i) thioester-dependent substrate-level phosphorylations, (ii) harnessing of naturally existing proton gradients at the vent–ocean interface via the ATP synthase, (iii) harnessing of Na+ gradients generated by H+/Na+ antiporters, (iv) flavin-based bifurcation-dependent gradient generation, and finally (v) quinone-based (and Q-cycle-dependent) proton gradient generation. Of those five transitions, the first four are posited to have taken place at the vent. Ultimately, all of these bioenergetic processes depend, even today, upon CO2 reduction with low-potential ferredoxin (Fd), generated either chemosynthetically or photosynthetically, suggesting a reaction of the type ‘reduced iron → reduced carbon’ at the beginning of bioenergetic evolution

  10. Theia's Collision With The Early Earth - Dry Or Wet Moon?

    Science.gov (United States)

    Dvorak, R.; Loibnegger, B.; Burger, C.; Maindl, T. I.; Schäfer, C.

    2016-04-01

    Our study exist of three separated parts concerning the formation of the Moon due to a catastrophic collision of a Mars-sized body - often referred to as Theia - with the early Earth. The first one deals with planet-formation in the early Solar System, the second one with the dynamical evolution of the planets Venus, Earth, Mars, Jupiter, and Saturn and an additional planet (Theia) between Earth and Mars, and the third one with the proposed giant collision itself and its outcome concerning masses and water contents of the resulting bodies (or fragments), computed via Smoothed Particle Hydrodynamics (SPH) simulations.

  11. Evolution of the Earth-Moon system

    Science.gov (United States)

    Touma, Jihad; Wisdom, Jack

    1994-01-01

    The tidal evolution of the Earth-Moon system is reexamined. Several models of tidal friction are first compared in an averaged Hamiltonian formulation of the dynamics. With one of these models, full integrations of the tidally evolving Earth-Moon system are carried out in the complete, fully interacting, and chaotically evolving planetary system. Classic results on the history of the lunar orbit are confirmed by our more general model. A detailed history of the obliquity of the Earth which takes into account the evolving lunar orbit is presented.

  12. Factors Influencing the Earth's Magnetic Field Evolution

    CERN Document Server

    Kurazhkovskii, A Yu; Klain, B I

    2008-01-01

    The relationship between the behavior of an ancient geomagnetic field characteristics (paleointensity and frequency of inversions) and cyclic recurrence of endogenic and cosmogeneous processes which are conceivably connected with radial mantle heat transmission and the Earth rotation speed has been studied. It is shown that endogenic processes affect the behavior of the paleointensity and frequency of inversions. Large basalt effusions identified with plumes are accompanied by the changes in paleointensity (by 30-40)% and the frequency of inversions. Characteristic time intervals of paleointensity variations caused by the formation of plumes makes up 10-20 Ma. The paleointensity varies (by 15-30)% according to phases of the riftogenesis activization and tension - compression cycles. The dependence of geomagnetic field behavior on changes of the Earth rotation speed which occurred as a result of the Earth - Moon - Sun system evolution has been analyzed. Thus, in accordance with phases of the Earth - Moon dista...

  13. Early cellular evolution.

    Science.gov (United States)

    Margulis, L.

    1972-01-01

    Study of the evolutionary developments that occurred subsequent to the origin of ancestral cells. Microbial physiology and ecology are potential sharp tools for shaping concepts of microbial evolution. Some popular unjustified assumptions are discussed. It is considered that certain principles derived mainly from the advances of molecular biology can be used to order the natural groups (genera) of extant prokaryotes and their patterns phylogenetically.

  14. Organic chemistry in the ionosphere of the Early Earth

    Science.gov (United States)

    Carrasco, N.; Fleury, B.; Vettier, L.

    2015-10-01

    The emergence of life on the Early Earth during the Archean has required a prior complex organic chemistry providing the prerequisite bricks of life. The origin of the organic matter and its evolution on the early Earth is far from being understood. Several hypotheses are investigated, possibly complementary, which can be divided in two main categories: the endogenous and the exogenous sources. In this work we have been interested in the contribution of a specific endogenous source: the organic chemistry occurring in the ionosphere of the early Earth. At these high altitudes, the VUV contribution of the young sun was important, involving an efficient production of reactive species. Here we address the issue whether this chemistry can lead to the production of larger molecules with a prebiotic interest in spite of the competitive lysing effect of the harsh irradiation at these altitudes.

  15. Earth's oxygen cycle and the evolution of animal life.

    Science.gov (United States)

    Reinhard, Christopher T; Planavsky, Noah J; Olson, Stephanie L; Lyons, Timothy W; Erwin, Douglas H

    2016-08-09

    The emergence and expansion of complex eukaryotic life on Earth is linked at a basic level to the secular evolution of surface oxygen levels. However, the role that planetary redox evolution has played in controlling the timing of metazoan (animal) emergence and diversification, if any, has been intensely debated. Discussion has gravitated toward threshold levels of environmental free oxygen (O2) necessary for early evolving animals to survive under controlled conditions. However, defining such thresholds in practice is not straightforward, and environmental O2 levels can potentially constrain animal life in ways distinct from threshold O2 tolerance. Herein, we quantitatively explore one aspect of the evolutionary coupling between animal life and Earth's oxygen cycle-the influence of spatial and temporal variability in surface ocean O2 levels on the ecology of early metazoan organisms. Through the application of a series of quantitative biogeochemical models, we find that large spatiotemporal variations in surface ocean O2 levels and pervasive benthic anoxia are expected in a world with much lower atmospheric pO2 than at present, resulting in severe ecological constraints and a challenging evolutionary landscape for early metazoan life. We argue that these effects, when considered in the light of synergistic interactions with other environmental parameters and variable O2 demand throughout an organism's life history, would have resulted in long-term evolutionary and ecological inhibition of animal life on Earth for much of Middle Proterozoic time (∼1.8-0.8 billion years ago).

  16. Early Earth(s) Across Time and Space

    Science.gov (United States)

    Mojzsis, S.

    2014-04-01

    The geochemical and cosmochemical record of our solar system is the baseline for exploring the question: "when could life appear on a world similar to our own?" Data arising from direct analysis of the oldest terrestrial rocks and minerals from the first 500 Myr of Earth history - termed the Hadean Eon - inform us about the timing for the establishment of a habitable silicate world. Liquid water is the key medium for life. The origin of water, and its interaction with the crust as revealed in the geologic record, guides our exploration for a cosmochemically Earth-like planets. From the time of primary planetary accretion to the start of the continuous rock record on Earth at ca. 3850 million years ago, our planet experienced a waning bolide flux that partially or entirely wiped out surface rocks, vaporized oceans, and created transient serpentinizing atmospheres. Arguably, "Early Earths" across the galaxy may start off as ice planets due to feeble insolation from their young stars, occasionally punctuated by steam atmospheres generated by cataclysmic impacts. Alternatively, early global environments conducive to life spanned from a benign surface zone to deep into crustal rocks and sediments. In some scenarios, nascent biospheres benefit from the exogenous delivery of essential bio-elements via leftovers of accretion, and the subsequent establishment of planetary-scale hydrothermal systems. If what is now known about the early dynamical regime of the Earth serves as any measure of the potential habitability of worlds across space and time, several key boundary conditions emerge. These are: (i) availability and long-term stability of liquid water; (ii) presence of energy resources; (iii) accessibility of organic raw materials; (iv) adequate inventory of radioisotopes to drive internal heating; (v) gross compositional parameters such as mantle/core mass ratio, and (vi) P-T conditions at or near the surface suitable for sustaining biological activity. Life could

  17. Magma Oceans on Exoplanets and Early Earth

    Science.gov (United States)

    Elkins-Tanton, Linda

    2009-09-01

    Late, giant accretionary impacts likely form multiple magma oceans of some depth in young rocky planets. Models of magma ocean solidification that incorporate water, carbon, and other incompatible volatile elements in small amounts predict a range of first-order outcomes important to planetary evolution. First, initial planetary bulk composition and size determine the composition of the earliest degassed atmosphere. This early atmosphere appears in a rapid burst at the end of solidification, determined by the ability of nucleating bubbles to reach the surface. Larger planets will have briefer and more catastrophic atmospheric degassing during solidification of any magma ocean. Second, this early atmosphere is sufficiently insulating to keep the planetary surface hot for millions of years. Depending upon the atmospheric composition and temperature structure these hot young planets may be observable from Earth or from satellites. Third, small but significant quantities of volatiles remain in the planet's solid mantle, encouraging convection, plate tectonics, and later atmospheric degassing through volcanism. A critical outcome of magma ocean solidification is the development of a solid mantle density gradient with den-sity increasing with radius, which will flow to gravitational stability. Shallow, dense, damp material will carry its water content as it sinks into the perovskite stability zone and transforms into perovskite. Even in models with very low initial water contents, a large fraction of the sinking upper mantle material will be forced to dewater as it crosses the boundary into the relatively dry lower mantle, leaving its water behind in a rapid flux as it sinks. This water ad-dition could initiate or speed convection in planets in which perovskite is stable, that is, planets larger than Mars.

  18. Atmospheric nitrogen evolution on Earth and Venus

    Science.gov (United States)

    Wordsworth, R. D.

    2016-08-01

    Nitrogen is the most common element in Earth's atmosphere and also appears to be present in significant amounts in the mantle. However, its long-term cycling between these two reservoirs remains poorly understood. Here a range of biotic and abiotic mechanisms are evaluated that could have caused nitrogen exchange between Earth's surface and interior over time. In the Archean, biological nitrogen fixation was likely strongly limited by nutrient and/or electron acceptor constraints. Abiotic fixation of dinitrogen becomes efficient in strongly reducing atmospheres, but only once temperatures exceed around 1000 K. Hence if atmospheric N2 levels really were as low as they are today 3.0-3.5 Ga, the bulk of Earth's mantle nitrogen must have been emplaced in the Hadean, most likely at a time when the surface was molten. The elevated atmospheric N content on Venus compared to Earth can be explained abiotically by a water loss redox pump mechanism, where oxygen liberated from H2O photolysis and subsequent H loss to space oxidises the mantle, causing enhanced outgassing of nitrogen. This mechanism has implications for understanding the partitioning of other Venusian volatiles and atmospheric evolution on exoplanets.

  19. Origin and early evolution of photosynthesis

    Science.gov (United States)

    Blankenship, R. E.

    1992-01-01

    Photosynthesis was well-established on the earth at least 3.5 thousand million years ago, and it is widely believed that these ancient organisms had similar metabolic capabilities to modern cyanobacteria. This requires that development of two photosystems and the oxygen evolution capability occurred very early in the earth's history, and that a presumed phase of evolution involving non-oxygen evolving photosynthetic organisms took place even earlier. The evolutionary relationships of the reaction center complexes found in all the classes of currently existing organisms have been analyzed using sequence analysis and biophysical measurements. The results indicate that all reaction centers fall into two basic groups, those with pheophytin and a pair of quinones as early acceptors, and those with iron sulfur clusters as early acceptors. No simple linear branching evolutionary scheme can account for the distribution patterns of reaction centers in existing photosynthetic organisms, and lateral transfer of genetic information is considered as a likely possibility. Possible scenarios for the development of primitive reaction centers into the heterodimeric protein structures found in existing reaction centers and for the development of organisms with two linked photosystems are presented.

  20. Mega-Impacts on Mars: Implications for the Late Heavy Bombardment in the Inner Solar System, and the Early Evolution of the Earth and Mars

    Science.gov (United States)

    Frey, Herbert

    2012-01-01

    There are about 30 very large impact basins on Mars, > 1000 km in diameter, most of which are revealed by their topographic and/or crustal thickness signatures. Crater retention ages and model absolute ages suggest these all formed in a relatively short time (100-200 million years?), perhaps during a "Late Heavy Bombardment" (LHB) caused by the evolution of the orbits of the giant planets. This so-called "Nice Model" of planetary formation may explain the LHB on the Moon at about 3.9 billion years ago and would have produced a similar bombardment throughout the inner solar system. The formation of 30 very large impact basins would have had catastrophic environmental consequences for Mars, which were further complicated by the demise of the global magnetic field at about the same time. If there are no very large basins on Mars older than the 30 we see and the LHB really lasted everywhere only a short time, there may have been a relatively longer time (400 million years?) during which Mars and the Earth suffered no major impact trauma and during which conditions on both worlds may have been far more habitable than during the LHB. However, if the formation of the Mars crustal dichotomy was due to an even larger giant impact that predated the very large basins, all record of this earlier and possibly more clement time on Mars may have been erased. Ages of the smaller but still very large basins can be used to approximately date the giant impact (if it occurred). Even the very large basins appear to have reset the crater retention ages of the entire crust of Mars and may have by themselves erased any record of an earlier time.

  1. Evolution of U fractionation processes through geologic time : consequences for the variation of U deposit types from Early Earth to Present

    Science.gov (United States)

    Cuney, M.

    2009-12-01

    U deposits are known at nearly all stages of the geological cycle, but are not known prior to 2.95 Ga. Also, U deposit types vary greatly from Mesoarchean to Present. Most of these changes through time can be attributed to major modifications in the geodynamic evolution of the Earth, in magmatic fractionation processes, in the composition of the Atmosphere and in the nature of life. The first U-rich granites able to crystallize uraninite, appeared at about 3.1 Ga. They correspond to the most fractionated terms of high-K calcalkaline suites, resulting from crystal fractionation of magmas possibly derived from melting of mantle wedges enriched in K, U, Th. Highly fractionated peraluminous leucogranites, able to crystallize uraninite, appeared at about 2.6 Ga. Erosion of these two granite types led to the detrital accumulation of uraninite that formed the first U deposits on Earth: the Quartz Pebble Conglomerates from 2.95 to 2.4 Ga. From 2.3 Ga onwards, uprise of oxygen level in the atmosphere led to the oxidation of U(IV) to U(VI), U transport in solution, and exuberant development of marine algae in epicontinental platform sediments. From 2.3 to 1.8 Ga large amounts of U, previously accumulated as U(IV) minerals, were dissolved and trapped preferentially in passive margin settings, in organic-rich sediments, and which led to the formation of the world’s largest Paleoproterozoic U provinces, e.g. : the Wollaston belt, Canada and the Cahill Formation, Australia. During and after the worldwide 2.1-1.75 Ga orogenic events, responsible for the formation of the Nuna supercontinent, U trapped in these formations was the source for several types of mineralization: (i) metamorphosed U-mineralized graphitic schists, calcsilicates and meta-arkoses, (ii) diagenetic-hydrothermal remobilization with the formation of the first deposits related to redox processes at 2.0 Ga (Oklo, Gabon), (iii) partial melting of U-rich metasediments forming the uraninite disseminations in

  2. Natural evidence for chemical and early biological evolution

    Science.gov (United States)

    Kvenvolden, K. A.

    1974-01-01

    Oparin (1924) and Haldane (1929) have independently hypothesized that life arose under reducing conditions through an evolutionary sequence of events involving increasingly complex organic substances. The natural evidence for this hypothesis of chemical evolution is considered, giving particular attention to tangible samples which have been chemically analyzed in earth-bound laboratories. It is found that meteorites provide naturally occurring evidence in support of chemical evolution, but not of biological evolution. Studies on the early Precambrian Swaziland Sequence and the Bulawayan System of southern Africa provide evidence for very early biological evolution.

  3. Oxygen isotope perspective on crustal evolution on early Earth: A record of Precambrian shales with emphasis on Paleoproterozoic glaciations and Great Oxygenation Event

    Science.gov (United States)

    Bindeman, I. N.; Bekker, A.; Zakharov, D. O.

    2016-03-01

    We present stable isotope and chemical data for 206 Precambrian bulk shale and tillite samples that were collected mostly from drillholes on all continents and span the age range from 0.5 to 3.5 Ga with a dense coverage for 2.5-2.2 Ga time interval when Earth experienced four Snowball Earth glaciations and the irreversible rise in atmospheric O2. We observe significant, downward shift of several ‰ and a smaller range of δ18 O values (7 to 9‰) in shales that are associated with the Paleoproterozoic and, potentially, Neoproterozoic glaciations. The Paleoproterozoic samples consist of more than 50% mica minerals and have equal or higher chemical index of alteration than overlying and underlying formations and thus underwent equal or greater degrees of chemical weathering. Their pervasively low δ18 O and δD (down to - 85 ‰) values provide strong evidence of alteration and diagenesis in contact with ultra-low δ18 O glacial meltwaters in lacustrine, deltaic or periglacial lake (sikussak-type) environments associated with the Paleoproterozoic glaciations. The δDsilicate values for the rest of Precambrian shales range from -75 to - 50 ‰ and are comparable to those for Phanerozoic and Archean shales. Likewise, these samples have similar ranges in δ13Corg values (-23 to - 33 ‰ PDB) and Corg content (0.0 to 10 wt%) to Phanerozoic shales. Precambrian shales have a large range of δ18 O values comparable to that of the Phanerozoic shales in each age group and formation, suggesting similar variability in the provenance and intensity of chemical weathering, except for the earliest 3.3-3.5 Ga Archean shales, which have consistently lower δ18 O values. Moreover, Paleoproterozoic shales that bracket in age the Great Oxidation Event (GOE) overlap in δ18 O values. Absence of a step-wise increase in δ18 O and δD values suggests that despite the first-order change in the composition of the atmosphere, weathering cycle was not dramatically affected by the GOE at ∼2

  4. Earth's oxygen cycle and the evolution of animal life

    Science.gov (United States)

    Reinhard, Christopher T.; Planavsky, Noah J.; Olson, Stephanie L.; Lyons, Timothy W.; Erwin, Douglas H.

    2016-08-01

    The emergence and expansion of complex eukaryotic life on Earth is linked at a basic level to the secular evolution of surface oxygen levels. However, the role that planetary redox evolution has played in controlling the timing of metazoan (animal) emergence and diversification, if any, has been intensely debated. Discussion has gravitated toward threshold levels of environmental free oxygen (O2) necessary for early evolving animals to survive under controlled conditions. However, defining such thresholds in practice is not straightforward, and environmental O2 levels can potentially constrain animal life in ways distinct from threshold O2 tolerance. Herein, we quantitatively explore one aspect of the evolutionary coupling between animal life and Earth’s oxygen cycle—the influence of spatial and temporal variability in surface ocean O2 levels on the ecology of early metazoan organisms. Through the application of a series of quantitative biogeochemical models, we find that large spatiotemporal variations in surface ocean O2 levels and pervasive benthic anoxia are expected in a world with much lower atmospheric pO2 than at present, resulting in severe ecological constraints and a challenging evolutionary landscape for early metazoan life. We argue that these effects, when considered in the light of synergistic interactions with other environmental parameters and variable O2 demand throughout an organism’s life history, would have resulted in long-term evolutionary and ecological inhibition of animal life on Earth for much of Middle Proterozoic time (˜1.8-0.8 billion years ago).

  5. Impact phenomena as factors in the evolution of the Earth

    Science.gov (United States)

    Grieve, R. A. F.; Parmentier, E. M.

    1984-01-01

    It is estimated that 30 to 200 large impact basins could have been formed on the early Earth. These large impacts may have resulted in extensive volcanism and enhanced endogenic geologic activity over large areas. Initial modelling of the thermal and subsidence history of large terrestrial basins indicates that they created geologic and thermal anomalies which lasted for geologically significant times. The role of large-scale impact in the biological evolution of the Earth has been highlighted by the discovery of siderophile anomalies at the Cretaceous-Tertiary boundary and associated with North American microtektites. Although in neither case has an associated crater been identified, the observations are consistent with the deposition of projectile-contaminated high-speed ejecta from major impact events. Consideration of impact processes reveals a number of mechanisms by which large-scale impact may induce extinctions.

  6. Early differentiation of the Earth and the Moon.

    Science.gov (United States)

    Bourdon, Bernard; Touboul, Mathieu; Caro, Guillaume; Kleine, Thorsten

    2008-11-28

    We examine the implications of new 182W and 142Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60Ma after the formation of calcium-aluminium-rich inclusions (4.568Gyr). This is not inconsistent with the apparent U-Pb age of the Earth. The new 142Nd data for Martian meteorites show that Mars probably has a super-chondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142Nd-143Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50-100Myr could have yielded the 200Myr model age.

  7. UV SURFACE ENVIRONMENT OF EARTH-LIKE PLANETS ORBITING FGKM STARS THROUGH GEOLOGICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Rugheimer, S.; Sasselov, D. [Harvard Smithsonian Center for Astrophysics, 60 Garden st., 02138 MA Cambridge (United States); Segura, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México (Mexico); Kaltenegger, L., E-mail: srugheimer@cfa.harvard.edu [Carl Sagan Institute, Cornell University, Ithaca, NY 14853 (United States)

    2015-06-10

    The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early-Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present-day levels at 2.0 Gyr ago, 0.8 Gyr ago, and modern Earth. In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth–Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5 V) receives 300 times less biologically effective radiation, about 2 times modern Earth–Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments.

  8. The atmospheres of the earth and the other planets: Origin, evolution and composition

    Science.gov (United States)

    Levine, Joel S.

    1988-01-01

    The current understanding of the composition, chemistry, and structure of the atmospheres of the other planets and the origin, early history, and evolution of the earth's atmosphere is reviewed. The information on the atmospheres of the other planets is based on the successful Mariner, Viking, Pioneer, and Voyager missions to these planets. The information on the origin, early history, and evolution of the atmosphere, which is somewhat speculative, is largely based on numerical studies with geochemical and photochemical models.

  9. Environment and Climate of Early Human Evolution

    Science.gov (United States)

    Levin, Naomi E.

    2015-05-01

    Evaluating the relationships between climate, the environment, and human traits is a key part of human origins research because changes in Earth's atmosphere, oceans, landscapes, and ecosystems over the past 10 Myr shaped the selection pressures experienced by early humans. In Africa, these relationships have been influenced by a combination of high-latitude ice distributions, sea surface temperatures, and low-latitude orbital forcing that resulted in large oscillations in vegetation and moisture availability that were modulated by local basin dynamics. The importance of both climate and tectonics in shaping African landscapes means that integrated views of the ecological, environmental, and tectonic histories of a region are necessary in order to understand the relationships between climate and human evolution.

  10. Isotope composition and volume of Earth's early oceans.

    Science.gov (United States)

    Pope, Emily C; Bird, Dennis K; Rosing, Minik T

    2012-03-20

    Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH(4) and CO(2) concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth.

  11. Global-scale water circulation in the Earth's mantle: Implications for the mantle water budget in the early Earth

    Science.gov (United States)

    Nakagawa, Takashi; Spiegelman, Marc W.

    2017-04-01

    We investigate the influence of the mantle water content in the early Earth on that in the present mantle using numerical convection simulations that include three processes for redistribution of water: dehydration, partitioning of water into partially molten mantle, and regassing assuming an infinite water reservoir at the surface. These models suggest that the water content of the present mantle is insensitive to that of the early Earth. The initial water stored during planetary formation is regulated up to 1.2 OMs (OM = Ocean Mass; 1.4 ×1021 kg), which is reasonable for early Earth. However, the mantle water content is sensitive to the rheological dependence on the water content and can range from 1.2 to 3 OMs at the present day. To explain the evolution of mantle water content, we computed water fluxes due to subducting plates (regassing), degassing and dehydration. For weakly water dependent viscosity, the net water flux is almost balanced with those three fluxes but, for strongly water dependent viscosity, the regassing dominates the water cycle system because the surface plate activity is more vigorous. The increased convection is due to enhanced lubrication of the plates caused by a weak hydrous crust for strongly water dependent viscosity. The degassing history is insensitive to the initial water content of the early Earth as well as rheological strength. The degassing flux from Earth's surface is calculated to be approximately O (1013) kg /yr, consistent with a coupled model of climate evolution and mantle thermal evolution.

  12. Archean komatiite volcanism controlled by the evolution of early continents.

    Science.gov (United States)

    Mole, David R; Fiorentini, Marco L; Thebaud, Nicolas; Cassidy, Kevin F; McCuaig, T Campbell; Kirkland, Christopher L; Romano, Sandra S; Doublier, Michael P; Belousova, Elena A; Barnes, Stephen J; Miller, John

    2014-07-15

    The generation and evolution of Earth's continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50-30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean-Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits.

  13. Evolution of the earth's crust: Evidence from comparative planetology

    Science.gov (United States)

    Lowman, P. D., Jr.

    1973-01-01

    Geochemical data and orbital photography from Apollo, Mariner, and Venera missions were combined with terrestrial geologic evidence to study the problem of why the earth has two contrasting types of crust (oceanic and continental). The following outline of terrestrial crustal evolution is proposed. A global crust of intermediate to acidic composition, high in aluminum, was formed by igneous processes early in the earth's history; portions survive in some shield areas as granitic and anorthositic gneisses. This crust was fractured by major impacts and tectonic processes, followed by basaltic eruptions analogous to the lunar maria and the smooth plains of the north hemisphere of Mars. Seafloor spreading and subduction ensued, during which portions of the early continental crust and sediments derived therefrom were thrust under the remaining continental crust. The process is exemplified today in regions such as the Andes/Peru-Chile trench system. Underplating may have been roughly concentric, and the higher radioactive element content of the underplated sialic material could thus eventually cause concentric zones of regional metamorphism and magmatism.

  14. Warming the early Earth - CO2 reconsidered

    CERN Document Server

    Von Paris, P; Grenfell, L; Patzer, B; Hedelt, P; Stracke, B; Trautmann, T; Schreier, F

    2008-01-01

    Despite a fainter Sun, the surface of the early Earth was mostly ice-free. Proposed solutions to this so-called "faint young Sun problem" have usually involved higher amounts of greenhouse gases than present in the modern-day atmosphere. However, geological evidence seemed to indicate that the atmospheric CO2 concentrations during the Archaean and Proterozoic were far too low to keep the surface from freezing. With a radiative-convective model including new, updated thermal absorption coefficients, we found that the amount of CO2 necessary to obtain 273 K at the surface is reduced up to an order of magnitude compared to previous studies. For the late Archaean and early Proterozoic period of the Earth, we calculate that CO2 partial pressures of only about 2.9 mb are required to keep its surface from freezing which is compatible with the amount inferred from sediment studies. This conclusion was not significantly changed when we varied model parameters such as relative humidity or surface albedo, obtaining CO2 ...

  15. Prebiotic Phosphorylation Reactions on the Early Earth

    Directory of Open Access Journals (Sweden)

    Maheen Gull

    2014-07-01

    Full Text Available Phosphorus (P is an essential element for life. It occurs in living beings in the form of phosphate, which is ubiquitous in biochemistry, chiefly in the form of C-O-P (carbon, oxygen and phosphorus, C-P, or P-O-P linkages to form life. Within prebiotic chemistry, several key questions concerning phosphorus chemistry have developed: what were the most likely sources of P on the early Earth? How did it become incorporated into the biological world to form the P compounds that life employs today? Can meteorites be responsible for the delivery of P? What were the most likely solvents on the early Earth and out of those which are favorable for phosphorylation? Or, alternatively, were P compounds most likely produced in relatively dry environments? What were the most suitable temperature conditions for phosphorylation? A route to efficient formation of biological P compounds is still a question that challenges astrobiologists. This article discusses these important issues related to the origin of biological P compounds.

  16. Early Life on Earth: the Ancient Fossil Record

    Science.gov (United States)

    Westall, F.

    2004-07-01

    The evidence for early life and its initial evolution on Earth is lin= ked intimately with the geological evolution of the early Earth. The environment of the early Earth would be considered extreme by modern standards: hot (50-80=B0C), volcanically and hydrothermally active, a= noxic, high UV flux, and a high flux of extraterrestrial impacts. Habitats = for life were more limited until continent-building processes resulted in= the formation of stable cratons with wide, shallow, continental platforms= in the Mid-Late Archaean. Unfortunately there are no records of the first appearance of life and the earliest isotopic indications of the exist= ence of organisms fractionating carbon in ~3.8 Ga rocks from the Isua greenst= one belt in Greenland are tenuous. Well-preserved microfossils and micro= bial mats (in the form of tabular and domical stromatolites) occur in 3.5-= 3.3 Ga, Early Archaean, sedimentary formations from the Barberton (South Afri= ca) and Pilbara (Australia) greenstone belts. They document life forms that = show a relatively advanced level of evolution. Microfossil morphology inclu= des filamentous, coccoid, rod and vibroid shapes. Colonial microorganism= s formed biofilms and microbial mats at the surfaces of volcaniclastic = and chemical sediments, some of which created (small) macroscopic microbi= alites such as stromatolites. Anoxygenic photosynthesis may already have developed. Carbon, nitrogen and sulphur isotopes ratios are in the r= ange of those for organisms with anaerobic metabolisms, such as methanogenesi= s, sulphate reduction and photosynthesis. Life was apparently distribute= d widely in shallow-water to littoral environments, including exposed, evaporitic basins and regions of hydrothermal activity. Biomass in t= he early Archaean was restricted owing to the limited amount of energy t= hat could be produced by anaerobic metabolisms. Microfossils resembling o= xygenic photosynthesisers, such as cyanobacteria, probably first occurred in

  17. Electrons, life and the evolution of Earth's oxygen cycle.

    Science.gov (United States)

    Falkowski, Paul G; Godfrey, Linda V

    2008-08-27

    The biogeochemical cycles of H, C, N, O and S are coupled via biologically catalysed electron transfer (redox) reactions. The metabolic processes responsible for maintaining these cycles evolved over the first ca 2.3 Ga of Earth's history in prokaryotes and, through a sequence of events, led to the production of oxygen via the photobiologically catalysed oxidation of water. However, geochemical evidence suggests that there was a delay of several hundred million years before oxygen accumulated in Earth's atmosphere related to changes in the burial efficiency of organic matter and fundamental alterations in the nitrogen cycle. In the latter case, the presence of free molecular oxygen allowed ammonium to be oxidized to nitrate and subsequently denitrified. The interaction between the oxygen and nitrogen cycles in particular led to a negative feedback, in which increased production of oxygen led to decreased fixed inorganic nitrogen in the oceans. This feedback, which is supported by isotopic analyses of fixed nitrogen in sedimentary rocks from the Late Archaean, continues to the present. However, once sufficient oxygen accumulated in Earth's atmosphere to allow nitrification to out-compete denitrification, a new stable electron 'market' emerged in which oxygenic photosynthesis and aerobic respiration ultimately spread via endosymbiotic events and massive lateral gene transfer to eukaryotic host cells, allowing the evolution of complex (i.e. animal) life forms. The resulting network of electron transfers led a gas composition of Earth's atmosphere that is far from thermodynamic equilibrium (i.e. it is an emergent property), yet is relatively stable on geological time scales. The early coevolution of the C, N and O cycles, and the resulting non-equilibrium gaseous by-products can be used as a guide to search for the presence of life on terrestrial planets outside of our Solar System.

  18. The Evolution of the Earth's Magnetic Field.

    Science.gov (United States)

    Bloxham, Jeremy; Gubbins, David

    1989-01-01

    Describes the change of earth's magnetic field at the boundary between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)

  19. Core cooling by subsolidus mantle convection. [thermal evolution model of earth

    Science.gov (United States)

    Schubert, G.; Cassen, P.; Young, R. E.

    1979-01-01

    Although vigorous mantle convection early in the thermal history of the earth is shown to be capable of removing several times the latent heat content of the core, a thermal evolution model of the earth in which the core does not solidify can be constructed. The large amount of energy removed from the model earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the earth; the models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The earth models are constrained by the present surface heat flux and mantle viscosity and internal heat sources produce only about 55% of the earth model's present surface heat flow.

  20. Prebiotic materials from on and off the early Earth.

    Science.gov (United States)

    Bernstein, Max

    2006-10-29

    One of the greatest puzzles of all time is how did life arise? It has been universally presumed that life arose in a soup rich in carbon compounds, but from where did these organic molecules come? In this article, I will review proposed terrestrial sources of prebiotic organic molecules, such as Miller-Urey synthesis (including how they would depend on the oxidation state of the atmosphere) and hydrothermal vents and also input from space. While the former is perhaps better known and more commonly taught in school, we now know that comet and asteroid dust deliver tons of organics to the Earth every day, therefore this flux of reduced carbon from space probably also played a role in making the Earth habitable. We will compare and contrast the types and abundances of organics from on and off the Earth given standard assumptions. Perhaps each process provided specific compounds (amino acids, sugars, amphiphiles) that were directly related to the origin or early evolution of life. In any case, whether planetary, nebular or interstellar, we will consider how one might attempt to distinguish between abiotic organic molecules from actual signs of life as part of a robotic search for life in the Solar System.

  1. Atmospheric nitrogen evolution on Earth and Venus

    CERN Document Server

    Wordsworth, R D

    2016-01-01

    Nitrogen is the most common element in Earth's atmosphere and also appears to be present in significant amounts in the mantle. However, its long-term cycling between these two reservoirs remains poorly understood. Here a range of biotic and abiotic mechanisms are evaluated that could have caused nitrogen exchange between Earth's surface and interior over time. In the Archean, biological nitrogen fixation was likely strongly limited by nutrient and/or electron acceptor constraints. Abiotic fixation of dinitrogen becomes efficient in strongly reducing atmospheres, but only once temperatures exceed around 1000 K. Hence if atmospheric N2 levels really were as low as they are today 3.0 - 3.5 Ga, the bulk of Earth's mantle nitrogen must have been emplaced in the Hadean, most likely at a time when the surface was molten. The elevated atmospheric N content on Venus compared to Earth can be explained abiotically by a water loss redox pump mechanism, where oxygen liberated from H2O photolysis and subsequent H loss to s...

  2. The early Earth atmosphere and early life catalysts.

    Science.gov (United States)

    Ramírez Jiménez, Sandra Ignacia

    2014-01-01

    Homochirality is a property of living systems on Earth. The time, the place, and the way in which it appeared are uncertain. In a prebiotic scenario two situations are of interest: either an initial small bias for handedness of some biomolecules arouse and progressed with life, or an initial slight excess led to the actual complete dominance of the known chiral molecules. A definitive answer can probably never be given, neither from the fields of physics and chemistry nor biology. Some arguments can be advanced to understand if homochirality is necessary for the initiation of a prebiotic homochiral polymer chemistry, if this homochirality is suggesting a unique origin of life, or if a chiral template such as a mineral surface is always required to result in an enantiomeric excess. A general description of the early Earth scenario will be presented in this chapter, followed by a general description of some clays, and their role as substrates to allow the concentration and amplification of some of the building blocks of life.

  3. Peptide synthesis in early earth hydrothermal systems

    Science.gov (United States)

    Lemke, K.H.; Rosenbauer, R.J.; Bird, D.K.

    2009-01-01

    We report here results from experiments and thermodynamic calculations that demonstrate a rapid, temperature-enhanced synthesis of oligopeptides from the condensation of aqueous glycine. Experiments were conducted in custom-made hydrothermal reactors, and organic compounds were characterized with ultraviolet-visible procedures. A comparison of peptide yields at 260??C with those obtained at more moderate temperatures (160??C) gives evidence of a significant (13 kJ ?? mol-1) exergonic shift. In contrast to previous hydrothermal studies, we demonstrate that peptide synthesis is favored in hydrothermal fluids and that rates of peptide hydrolysis are controlled by the stability of the parent amino acid, with a critical dependence on reactor surface composition. From our study, we predict that rapid recycling of product peptides from cool into near-supercritical fluids in mid-ocean ridge hydrothermal systems will enhance peptide chain elongation. It is anticipated that the abundant hydrothermal systems on early Earth could have provided a substantial source of biomolecules required for the origin of life. Astrobiology 9, 141-146. ?? 2009 Mary Ann Liebert, Inc. 2009.

  4. Factors Influencing the Earth's Magnetic Field Evolution

    OpenAIRE

    Kurazhkovskii, A. Yu.; Kurazhkovskaya, N. A.; Klain, B. I.

    2008-01-01

    The relationship between the behavior of an ancient geomagnetic field characteristics (paleointensity and frequency of inversions) and cyclic recurrence of endogenic and cosmogeneous processes which are conceivably connected with radial mantle heat transmission and the Earth rotation speed has been studied. It is shown that endogenic processes affect the behavior of the paleointensity and frequency of inversions. Large basalt effusions identified with plumes are accompanied by the changes in ...

  5. UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution

    CERN Document Server

    Rugheimer, S; Kaltenegger, L; Sasselov, D

    2015-01-01

    The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars at the 1AU equivalent distance for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present day levels at 2.0 Gyr ago, 0.8 Gyr ago and modern Earth (Following Kaltenegger et al. 2007). In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth-Sun levels. A pre-biotic Earth orbiting GJ...

  6. Origin and evolution of the earth-moon system.

    Science.gov (United States)

    Alfven, H.; Arrhenius, G.

    1972-01-01

    The general problem of formation of secondary bodies around a central body is studied, and comparison is made with other satellite systems (Jupiter, Saturn, Uranus). The normal satellite systems of Neptune and the earth are reconstructed. The capture theory, the tidal evolution of the lunar orbit, destruction of a normal satellite system, asteroids and the earth-moon system, and accretion and heat structure of the moon are discussed. It is concluded that the moon originated as a planet accreted in a jet stream near the orbit of the earth, and was probably captured in a retrograde orbit.

  7. Siderophilic Cyanobacteria: Implications for Early Earth.

    Science.gov (United States)

    Brown, I. I.; Mummey, D.; Sarkisova, S.; Shen, G.; Bryant, D. A.; Lindsay, J.; Garrison, D.; McKay, D. S.

    2006-01-01

    Of all extant environs, iron-depositing hot springs (IDHS) may exhibit the greatest similarity to late Precambrian shallow warm oceans in regards to temperature, O2 gradients and dissolved iron and H2S concentrations. Despite the insights into the ecology, evolutionary biology, paleogeobiochemistry, and astrobiology examination of IDHS could potentially provide, very few studies dedicated to the physiology and diversity of cyanobacteria (CB) inhabiting IDHS have been conducted. Results. Here we describe the phylogeny, physiology, ultrastructure and biogeochemical activity of several recent CB isolates from two different greater Yellowstone area IDHS, LaDuke and Chocolate Pots. Phylogenetic analysis of 16S rRNA genes indicated that 6 of 12 new isolates examined couldn't be placed within established CB genera. Some of the isolates exhibited pronounced requirements for elevated iron concentrations, with maximum growth rates observed when 0.4-1 mM Fe(3+) was present in the media. In light of "typical" CB iron requirements, our results indicate that elevated iron likely represents a salient factor selecting for "siderophilicM CB species in IDHS. A universal feature of our new isolates is their ability to produce thick EPS layers in which iron accumulates resulting in the generation of well preserved signatures. In parallel, siderophilic CB show enhanced ability to etch the analogs of iron-rich lunar regolith minerals and impact glasses. Despite that iron deposition by CB is not well understood mechanistically, we recently obtained evidence that the PS I:PS II ratio is higher in one of our isolates than for other CB. Although still preliminary, this finding is in direct support of the Y. Cohen hypothesis that PSI can directly oxidize Fe(2+). Conclusion. Our results may have implications for factors driving CB evolutionary relationships and biogeochemical processes on early Earth and probably Mars.

  8. LSU scientists discover evidence of large meteorite impacts on the early earth

    Science.gov (United States)

    Lowe, Donald R.; Byerly, Gary R.

    1988-01-01

    Recent discoveries by scientists at Lousiana State University are examined which may provide a window through which early planetary accretion is viewed and studied and the role of large meteorite impacts on the evolution of life and the earth's surface evaluated.

  9. Research program for a search of the origin of Darwinian evolution. Research program for a vesicle-based model of the origin of Darwinian evolution on prebiotic early Earth

    Science.gov (United States)

    Tessera, Marc

    2017-03-01

    The search for origin of `life' is made even more complicated by differing definitions of the subject matter, although a general consensus is that an appropriate definition should center on Darwinian evolution (Cleland and Chyba 2002). Within a physical approach which has been defined as a level-4 evolution (Tessera and Hoelzer 2013), one mechanism could be described showing that only three conditions are required to allow natural selection to apply to populations of different system lineages. This approach leads to a vesicle- based model with the necessary properties. Of course such a model has to be tested. Thus, after a brief presentation of the model an experimental program is proposed that implements the different steps able to show whether this new direction of the research in the field is valid and workable.

  10. Research program for a search of the origin of Darwinian evolution : Research program for a vesicle-based model of the origin of Darwinian evolution on prebiotic early Earth.

    Science.gov (United States)

    Tessera, Marc

    2017-03-01

    The search for origin of 'life' is made even more complicated by differing definitions of the subject matter, although a general consensus is that an appropriate definition should center on Darwinian evolution (Cleland and Chyba 2002). Within a physical approach which has been defined as a level-4 evolution (Tessera and Hoelzer 2013), one mechanism could be described showing that only three conditions are required to allow natural selection to apply to populations of different system lineages. This approach leads to a vesicle- based model with the necessary properties. Of course such a model has to be tested. Thus, after a brief presentation of the model an experimental program is proposed that implements the different steps able to show whether this new direction of the research in the field is valid and workable.

  11. Early evolution stage of AGN

    Science.gov (United States)

    Kunert-Bajraszewska, M.; Labiano, A.; Siemiginowska, A.; Guainazzi, M.; Gawroński, M.

    2015-03-01

    Radio sources are divided into two distinct morphological groups of objects: Fanaroff-Riley type I and type II sources. There is a relatively sharp luminosity boundary between these at low frequency. The nature of the FR division is still an open issue, as are the details of the evolutionary process in which younger and smaller GHz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources become large-scale radio structures. It is still unclear whether FRII objects evolve to become FRIs, or whether a division has already occurred amongst CSS sources and some of these then become FRIs and some FRIIs. We explored evolution scenarios of AGNs using new radio, optical and X-ray data of unstudied so far Low Luminosity Compact (LLC) sources. We suggest that the determining factors of the further evolution of compact radio objects could occur at subgalactic (or even nuclear) scales, or they could be related to the radio jet - interstellar medium (ISM) interactions and evolution. Our studies show that the evolutionary track could be related to the interaction, strength of the radio source and excitation levels of the ionized gas instead of the radio morphology of the young radio source.

  12. Identifying early Earth microfossils in unsilicified sediments

    Science.gov (United States)

    Javaux, Emmanuelle J.; Asael, Dan; Bekker, Andrey; Debaille, Vinciane; Derenne, Sylvie; Hofmann, Axel; Mattielli, Nadine; Poulton, Simon

    2013-04-01

    The search for life on the early Earth or beyond Earth requires the definition of biosignatures, or "indices of life". These traditionally include fossil molecules, isotopic fractionations, biosedimentary structures and morphological fossils interpreted as remnants of life preserved in rocks. This research focuses on traces of life preserved in unsilicified siliciclastic sediments. Indeed, these deposits preserve well sedimentary structures indicative of past aqueous environments and organic matter, including the original organic walls of microscopic organisms. They also do not form in hydrothermal conditions which may be source of abiotic organics. At our knowledge, the only reported occurrence of microfossils preserved in unsilicified Archean sediments is a population of large organic-walled vesicles discovered in shales and siltstones of the 3.2 Ga Moodies Group, South Africa. (Javaux et al, Nature 2010). These have been interpreted as microfossils based on petrographic and geochemical evidence for their endogenicity and syngeneity, their carbonaceous composition, cellular morphology and ultrastructure, occurrence in populations, taphonomic features of soft wall deformation, and the geological context plausible for life, as well as lack of abiotic explanation falsifying a biological origin. Demonstrating that carbonaceous objects from Archaean rocks are truly old and truly biological is the subject of considerable debate. Abiotic processes are known to produce organics and isotopic signatures similar to life. Spheroidal pseudofossils may form as self-assembling vesicles from abiotic CM, e.g. in prebiotic chemistry experiments (Shoztak et al, 2001), from meteoritic lipids (Deamer et al, 2006), or hydrothermal fluids (Akashi et al, 1996); by artifact of maceration; by migration of abiotic or biotic CM along microfractures (VanZuilen et al, 2007) or along mineral casts (Brasier et al, 2005), or around silica spheres formed in silica-saturated water (Jones and

  13. Early Cretaceous angiosperms and beetle evolution

    OpenAIRE

    Bo eWang; Haichun eZhang; Edmund eJarzembowski

    2013-01-01

    The Coleoptera (beetles) constitute almost one–fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil record of some Early Cretaceous polyphagan beetles including Tenebrionoidea, Scarabaeoidea, Curculionoide...

  14. Mother Earth, Earth Mother: Gabriela Mistral as an Early Ecofeminist

    Science.gov (United States)

    Finzer, Erin

    2015-01-01

    Historians have noted that male bureaucrats and natural resource experts tended to dominate early twentieth-century national and hemispheric conservationist movements in Latin America, but a constellation of female activists, notable among them Gabriela Mistral, strengthened conservationism in the cultural sphere. Capitalizing on her leadership in…

  15. Thermospheric emissions of the early Earth

    Science.gov (United States)

    Bernard, D.; Barthélémy, M.; Gronoff, G.; Ménager, H.; Lilensten, J.

    2012-09-01

    The aim of this work is to examine the thermospheric emission of the Earth over its history. In this first step, we adapt a kinetic transport code developed for different planets of the Solar System to the first atmosphere of the Earth. We take into account the possible changes in the solar emission spectrum to compute the diurnal ionizations, excitations and dissociations. We deduce a thermospheric spectrum averaged over the planet. The effect of solar wind electron precipitation is also considered.

  16. Early dust evolution in protostellar accretion disks

    OpenAIRE

    2000-01-01

    We investigate dust dynamics and evolution during the formation of a protostellar accretion disk around intermediate mass stars via 2D numerical simulations. Using three different detailed dust models, compact spherical particles, fractal BPCA grains, and BCCA grains, we find that even during the early collapse and the first 10,000 yr of dynamical disk evolution, the initial dust size distribution is strongly modified. Close to the disk's midplane coagulation produces dust particles of sizes ...

  17. Atmospheres and evolution. [of microbial life on earth

    Science.gov (United States)

    Margulis, L.; Lovelock, J. E.

    1981-01-01

    Studies concerning the regulation of the earth atmosphere and the relation of atmospheric changes to the evolution of microbial life are reviewed. The improbable nature of the composition of the earth atmosphere in light of the atmospheric compositions of Mars and Venus and equilibrium considerations is pointed out, and evidence for the existence of microbial (procaryotic) life on earth as far back as 3.5 billion years ago is presented. The emergence of eucaryotic life in the Phanerozoic due to evolving symbioses between different procaryotic species is discussed with examples given of present-day symbiotic relationships between bacteria and eucaryotes. The idea that atmospheric gases are kept in balance mainly by the actions of bacterial cells is then considered, and it is argued that species diversity is necessary for the maintenance and origin of life on earth in its present form.

  18. Multiplicity in Early Stellar Evolution

    CERN Document Server

    Reipurth, Bo; Boss, Alan P; Goodwin, Simon P; Rodriguez, Luis Felipe; Stassun, Keivan G; Tokovinin, Andrei; Zinnecker, Hans

    2014-01-01

    Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of Class 0 protostars with mm interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of Class I protostars show a lower binary frequency relative to the Class 0 phase, a declining trend that continues through the Class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influenc...

  19. Earth Evolution and Dynamics (Arthur Holmes Medal Lecture)

    Science.gov (United States)

    Torsvik, Trond H.

    2016-04-01

    While physicists are fantasizing about a unified theory that can explain just about everything from subatomic particles (quantum mechanics) to the origin of the Universe (general relativity), Darwin already in 1858 elegantly unified the biological sciences with one grand vision. In the Earth Sciences, the description of the movement and deformation of the Earth's outer layer has evolved from Continental Drift (1912) into Sea-Floor Spreading (1962) and then to the paradigm of Plate Tectonics in the mid-to-late 1960s. Plate Tectonics has been extremely successful in providing a framework for understanding deformation and volcanism at plate boundaries, allowed us to understand how continent motions through time are a natural result of heat escaping from Earth's deep interior, and has granted us the means to conduct earthquake and volcanic hazard assessments and hydrocarbon exploration, which have proven indispensable for modern society. Plate Tectonics is as fundamentally unifying to the Earth Sciences as Darwin's Theory of Evolution is to the Life Sciences, but it is an incomplete theory that lacks a clear explanation of how plate tectonics, mantle convection and mantle plumes interact. Over the past decade, however, we have provided compelling evidence that plumes rise from explicit plume generation zones at the margins of two equatorial and antipodal large low shear-wave velocity provinces (Tuzo and Jason). These thermochemical provinces on the core-mantle boundary have been stable for at least the last 300 million years, possibly the last 540 million years, and their edges are the dominant sources of the plumes that generate large igneous provinces, hotspots and kimberlites. Linking surface and lithospheric processes to the mantle is extremely challenging and is only now becoming feasible due to breakthroughs in the estimation of ancient longitudes before the Cretaceous, greatly improved seismic tomography, recent advances in mineral physics, and new developments

  20. The Sensitivity of Earth's Climate History To Changes In The Rates of Biological And Geological Evolution

    Science.gov (United States)

    Waltham, D.

    2014-12-01

    The faint young Sun paradox (early Earth had surface liquid water despite solar luminosity 70% of the modern value) implies that our planet's albedo has increased through time and/or greenhouse warming has fallen. The obvious explanation is that negative feedback processes stabilized temperatures. However, the limited temperature data available does not exhibit the expected residual temperature rise and, at least for the Phanerozoic, estimates of climate sensitivity exceed the Planck sensitivity (the zero net-feedback value). The alternate explanation is that biological and geological evolution have tended to cool Earth through time hence countering solar-driven warming. The coincidence that Earth-evolution has roughly cancelled Solar-evolution can then be explained as an emergent property of a complex system (the Gaia hypothesis) or the result of the unavoidable observational bias that Earth's climate history must be compatible with our existence (the anthropic principle). Here, I use a simple climate model to investigate the sensitivity of Earth's climate to changes in the rate of Earth-evolution. Earth-evolution is represented by an effective emissivity which has an intrinsic variation through time (due to continental growth, the evolution of cyanobacteria, orbital fluctuations etc) plus a linear feedback term which enhances emissivity variations. An important feature of this model is a predicted maximum in the radiated-flux versus temperature function. If the increasing solar flux through time had exceeded this value then runaway warming would have occurred. For the best-guess temperature history and climate sensitivity, the Earth has always been within a few percent of this maximum. There is no obvious Gaian explanation for this flux-coincidence but the anthropic principle naturally explains it: If the rate of biological/geological evolution is naturally slow then Earth is a fortunate outlier which evolved just fast enough to avoid solar-induced over

  1. Carbonitriding reactions of diatomaceous earth: phase evolution and reaction mechanisms

    Directory of Open Access Journals (Sweden)

    BRANKO MATOVIC

    2006-06-01

    Full Text Available The possibility of using diatomaceous earth as Si precursor for low temperature synthesis of non-oxide powders by carbothermal reduction-nitridation was studied. It was found that carbonitriding reactions produce phases of the Si–Al–O–N system. Already at 1300 °C, nanosized, non-oxide powders were obtained. The comparatively low reaction temperatures is attributred to the nano-porous nature of the raw material. The evolution of crystalline phases proceeded via many intermediate stages. The powders were characterized by X-ray and SEM investigations. The results showed that diatomaceous earth can be a very effective source for obtaining non-oxide powders.

  2. The Role and Evolution of NASA's Earth Science Data Systems

    Science.gov (United States)

    Ramapriyan, H. K.

    2015-01-01

    One of the three strategic goals of NASA is to Advance understanding of Earth and develop technologies to improve the quality of life on our home planet (NASA strategic plan 2014). NASA's Earth Science Data System (ESDS) Program directly supports this goal. NASA has been launching satellites for civilian Earth observations for over 40 years, and collecting data from various types of instruments. Especially since 1990, with the start of the Earth Observing System (EOS) Program, which was a part of the Mission to Planet Earth, the observations have been significantly more extensive in their volumes, variety and velocity. Frequent, global observations are made in support of Earth system science. An open data policy has been in effect since 1990, with no period of exclusive access and non-discriminatory access to data, free of charge. NASA currently holds nearly 10 petabytes of Earth science data including satellite, air-borne, and ground-based measurements and derived geophysical parameter products in digital form. Millions of users around the world are using NASA data for Earth science research and applications. In 2014, over a billion data files were downloaded by users from NASAs EOS Data and Information System (EOSDIS), a system with 12 Distributed Active Archive Centers (DAACs) across the U. S. As a core component of the ESDS Program, EOSDIS has been operating since 1994, and has been evolving continuously with advances in information technology. The ESDS Program influences as well as benefits from advances in Earth Science Informatics. The presentation will provide an overview of the role and evolution of NASAs ESDS Program.

  3. Review, Intelligence and Development of Rare Earths during Biological Evolution

    Institute of Scientific and Technical Information of China (English)

    Qiu Guanming; Li Wei; Zhang Ming; Li Zhe; Yan Changhao; Li Yourong; Ding Guohui

    2004-01-01

    The relationship between organism and rare earth elements (REE) viewed from evolution was discussed.Some metal ions play key roles in biological functions, however, as the illustration in this article shows, with powerful affinities for oxygen and similar radius, REE can display equally or even more important functions in terms of its biological functions. These attractive characteristics have called more public attention and lead to many applications in agriculture, medicine fields, etc. Furthermore, the article employed the concept of entropy to discuss the dosage effect of REE on organism and the possibility whether REE can become a portion of organism during the evolution.

  4. The Early Flowers and Angiosperm Evolution

    DEFF Research Database (Denmark)

    Friis, Else Marie; Crane, P.R.; Pedersen, Kaj Raunsgaard

    The recent discovery of diverse fossil flowers and floral organs in Cretaceous strata has revealed astonishing details about the structural and systematic diversity of early angiosperms. Exploring the rich fossil record that has accumulated over the last three decades, this is a unique study...... based on research into Early and Late Cretaceous fossil floras from Europe and North America, the authors draw on direct palaeontological evidence of the pattern of angiosperm evolution through time. Synthesising palaeobotanical data with information from living plants, this unique book explores...... the latest research in the field, highlighting connections with phylogenetic systematics, structure and the biology of extant angiosperms....

  5. Human evolution. Evolution of early Homo: an integrated biological perspective.

    Science.gov (United States)

    Antón, Susan C; Potts, Richard; Aiello, Leslie C

    2014-07-04

    Integration of evidence over the past decade has revised understandings about the major adaptations underlying the origin and early evolution of the genus Homo. Many features associated with Homo sapiens, including our large linear bodies, elongated hind limbs, large energy-expensive brains, reduced sexual dimorphism, increased carnivory, and unique life history traits, were once thought to have evolved near the origin of the genus in response to heightened aridity and open habitats in Africa. However, recent analyses of fossil, archaeological, and environmental data indicate that such traits did not arise as a single package. Instead, some arose substantially earlier and some later than previously thought. From ~2.5 to 1.5 million years ago, three lineages of early Homo evolved in a context of habitat instability and fragmentation on seasonal, intergenerational, and evolutionary time scales. These contexts gave a selective advantage to traits, such as dietary flexibility and larger body size, that facilitated survival in shifting environments.

  6. Early Life on Earth and the Search for Extraterrestrial Biosignatures

    Science.gov (United States)

    Oehler, Dorothy Z.; House, Christopher

    2014-01-01

    In the last 2 years, scientists within the ARES Directorate at JSC have applied the technology of Secondary Ion Mass Spectrometry (SIMS) to individual organic structures preserved in Archean (approximately 3 billion years old) sediments on Earth. These organic structures are among the oldest on Earth that may be microfossils - structurally preserved remnants of ancient microbes. The SIMS work was done to determine the microfossils' stable carbon isotopic composition (delta C-13 values). This is the first time that such ancient, potential microfossils have been successfully analyzed for their individual delta C-13 values. The results support the interpretation that these structures are remnants of early life on Earth and that they may represent planktonic organisms that were widely distributed in the Earth's earliest oceans. This study has been accepted for publication in the journal Geology.

  7. Evolution of the Oxidation State of the Earth's Mantle

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, E.; Rahman, Z.

    2015-01-01

    The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3(+) at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. In our previous experiments on shergottite compositions, variable fO2, T, and P less than 4 GPa, Fe3(+)/sigma Fe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3(+)/sigma Fe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3(+). Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Preliminary multi-anvil experiments with Knippa basalt as the starting composition were conducted at 5-7 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal to Fe3(+)/2(+). Experiments are underway to produce glassy samples that can be measured by EELS and XANES, and are conducted at higher pressures.

  8. The Early Flowers and Angiosperm Evolution

    DEFF Research Database (Denmark)

    Friis, Else Marie; Crane, P.R.; Pedersen, Kaj Raunsgaard

    of the evolutionary history of flowering plants from their earliest phases in obscurity to their dominance in modern vegetation. The discussion provides comprehensive biological and geological background information, before moving on to summarise the fossil record in detail. Including previously unpublished results...... based on research into Early and Late Cretaceous fossil floras from Europe and North America, the authors draw on direct palaeontological evidence of the pattern of angiosperm evolution through time. Synthesising palaeobotanical data with information from living plants, this unique book explores...

  9. Cell evolution and Earth history: stasis and revolution.

    Science.gov (United States)

    Cavalier-Smith, Thomas

    2006-06-29

    This synthesis has three main parts. The first discusses the overall tree of life and nature of the last common ancestor (cenancestor). I emphasize key steps in cellular evolution important for ordering and timing the major evolutionary innovations in the history of the biosphere, explaining especially the origins of the eukaryote cell and of bacterial flagella and cell envelope novelties. Second, I map the tree onto the fossil record and discuss dates of key events and their biogeochemical impact. Finally, I present a broad synthesis, discussing evidence for a three-phase history of life. The first phase began perhaps ca 3.5 Gyr ago, when the origin of cells and anoxic photosynthesis generated the arguably most primitive prokaryote phylum, Chlorobacteria (= Chloroflexi), the first negibacteria with cells bounded by two acyl ester phospholipid membranes. After this 'chlorobacterial age' of benthic anaerobic evolution protected from UV radiation by mineral grains, two momentous quantum evolutionary episodes of cellular innovation and microbial radiation dramatically transformed the Earth's surface: the glycobacterial revolution initiated an oxygenic 'age of cyanobacteria' and, as the ozone layer grew, the rise of plankton; immensely later, probably as recently as ca 0.9 Gyr ago, the neomuran revolution ushered in the 'age of eukaryotes', Archaebacteria (arguably the youngest bacterial phylum), and morphological complexity. Diversification of glycobacteria ca 2.8 Gyr ago, predominantly inhabiting stratified benthic mats, I suggest caused serial depletion of 13C by ribulose 1,5-bis-phosphate caboxylase/oxygenase (Rubisco) to yield ultralight late Archaean organic carbon formerly attributed to methanogenesis plus methanotrophy. The late origin of archaebacterial methanogenesis ca 720 Myr ago perhaps triggered snowball Earth episodes by slight global warming increasing weathering and reducing CO2 levels, to yield runaway cooling; the origin of anaerobic methane

  10. The rise of oxygen in Earth's early ocean and atmosphere

    Science.gov (United States)

    Lyons, Timothy W.; Reinhard, Christopher T.; Planavsky, Noah J.

    2014-02-01

    The rapid increase of carbon dioxide concentration in Earth's modern atmosphere is a matter of major concern. But for the atmosphere of roughly two-and-half billion years ago, interest centres on a different gas: free oxygen (O2) spawned by early biological production. The initial increase of O2 in the atmosphere, its delayed build-up in the ocean, its increase to near-modern levels in the sea and air two billion years later, and its cause-and-effect relationship with life are among the most compelling stories in Earth's history.

  11. Subduction History and the Evolution of Earth's Lower Mantle

    Science.gov (United States)

    Bull, Abigail; Shephard, Grace; Torsvik, Trond

    2016-04-01

    Understanding the complex structure, dynamics and evolution of the deep mantle is a fundamental goal in solid Earth geophysics. Close to the core-mantle boundary, seismic images reveal a mantle characterised by (1) higher than average shear wave speeds beneath Asia and encircling the Pacific, consistent with sub ducting lithosphere beneath regions of ancient subduction, and (2) large regions of anomalously low seismic wavespeeds beneath Africa and the Central Pacific. The anomalously slow areas are often referred to as Large Low Shear Velocity Provinces (LLSVPs) due to the reduced velocity of seismic waves passing through them. The origin, composition and long-term evolution of the LLSVPs remain enigmatic. Geochemical inferences of multiple chemical reservoirs at depth, strong seismic contrasts, increased density, and an anticorrelation of shear wave velocity to bulk sound velocity in the anomalous regions imply that heterogeneities in both temperature and composition may be required to explain the seismic observations. Consequently, heterogeneous mantle models place the anomalies into the context of thermochemical piles, characterised by an anomalous component whose intrinsic density is a few percent higher relative to that of the surrounding mantle. Several hypotheses have arisen to explain the LLSVPs in the context of large-scale mantle convection. One end member scenario suggests that the LLSVPs are relatively mobile features over short timescales and thus are strongly affected by supercontinent cycles and Earth's plate motion history. In this scenario, the African LLSVP formed as a result of return flow in the mantle due to circum-Pangean subduction (~240 Ma), contrasting a much older Pacific LLSVP, which may be linked to the Rodinia supercontinent and is implied to have remained largely unchanged since Rodinian breakup (~750-700 Ma). This propounds that Earth's plate motion history plays a controlling role in LLSVP development, suggesting that the location

  12. Early dynamical evolution of young substructured clusters

    Science.gov (United States)

    Dorval, Julien; Boily, Christian

    2017-03-01

    Stellar clusters form with a high level of substructure, inherited from the molecular cloud and the star formation process. Evidence from observations and simulations also indicate the stars in such young clusters form a subvirial system. The subsequent dynamical evolution can cause important mass loss, ejecting a large part of the birth population in the field. It can also imprint the stellar population and still be inferred from observations of evolved clusters. Nbody simulations allow a better understanding of these early twists and turns, given realistic initial conditions. Nowadays, substructured, clumpy young clusters are usually obtained through pseudo-fractal growth and velocity inheritance. We introduce a new way to create clumpy initial conditions through a ''Hubble expansion'' which naturally produces self consistent clumps, velocity-wise. In depth analysis of the resulting clumps shows consistency with hydrodynamical simulations of young star clusters. We use these initial conditions to investigate the dynamical evolution of young subvirial clusters. We find the collapse to be soft, with hierarchical merging leading to a high level of mass segregation. The subsequent evolution is less pronounced than the equilibrium achieved from a cold collapse formation scenario.

  13. Fossil evidence for the early ant evolution

    Science.gov (United States)

    Perrichot, Vincent; Lacau, Sébastien; Néraudeau, Didier; Nel, André

    2008-02-01

    Ants are one of the most studied insects in the world; and the literature devoted to their origin and evolution, systematics, ecology, or interactions with plants, fungi and other organisms is prolific. However, no consensus yet exists on the age estimate of the first Formicidae or on the origin of their eusociality. We review the fossil and biogeographical record of all known Cretaceous ants. We discuss the possible origin of the Formicidae with emphasis on the most primitive subfamily Sphecomyrminae according to its distribution and the Early Cretaceous palaeogeography. And we review the evidence of true castes and eusociality of the early ants regarding their morphological features and their manner of preservation in amber. The mid-Cretaceous amber forest from south-western France where some of the oldest known ants lived, corresponded to a moist tropical forest close to the shore with a dominance of gymnosperm trees but where angiosperms (flowering plants) were already diversified. This palaeoenvironmental reconstruction supports an initial radiation of ants in forest ground litter coincident with the rise of angiosperms, as recently proposed as an ecological explanation for their origin and successful evolution.

  14. Electrical energy sources for organic synthesis on the early earth

    Science.gov (United States)

    Chyba, Christopher; Sagan, Carl

    1991-01-01

    In 1959, Miller and Urey (Science 130, 245) published their classic compilation of energy sources for indigenous prebiotic organic synthesis on the early Earth. Much contemporary origins of life research continues to employ their original estimates for terrestrial energy dissipation by lightning and coronal discharges, 2 × 1019 J yr-1 and 6 × 1019 J yr-1, respectively. However, more recent work in terrestrial lightning and point discharge research suggests that these values are overestimates by factors of about 20 and 120, respectively. Calculated concentrations of amino acids (or other prebiotic organic products) in the early terrestrial oceans due to electrical discharge sources may therefore have been equally overestimated. A review of efficiencies for those experiments that provide good analogues to naturally-occurring lightning and coronal discharges suggests that lightning energy yields for organic synthesis (nmole J-1) are about one order of magnitude higher than those for coronal discharge. Therefore organic production by lightning may be expected to have dominated that due to coronae on early Earth. Limited data available for production of nitric oxide in clouds suggests that coronal emission within clouds, a source of energy heretofore too uncertain to be included in the total coronal energy inventory, is insufficient to change this conclusion. Our recommended valves for lightning and coronal discharge dissipation rates on the early Earth are, respectively, 1 × 1018 J yr-1 and 5 × 1017 J yr-1.

  15. On the origin and early evolution of biological catalysis and other studies on chemical evolution

    Science.gov (United States)

    Oro, J.; Lazcano, A.

    1991-01-01

    One of the lines of research in molecular evolution which we have developed for the past three years is related to the experimental and theoretical study of the origin and early evolution of biological catalysis. In an attempt to understand the nature of the first peptidic catalysts and coenzymes, we have achieved the non-enzymatic synthesis of the coenzymes ADPG, GDPG, and CDP-ethanolamine, under conditions considered to have been prevalent on the primitive Earth. We have also accomplished the prebiotic synthesis of histidine, as well as histidyl-histidine, and we have measured the enhancing effects of this catalytic dipeptide on the dephosphorylation of deoxyribonucleotide monophosphates, the hydrolysis of oligo A, and the oligomerization 2', 3' cAMP. We reviewed and further developed the hypothesis that RNA preceded double stranded DNA molecules as a reservoir of cellular genetic information. This led us to undertake the study of extant RNA polymerases in an attempt to discover vestigial sequences preserved from early Archean times. In addition, we continued our studies of on the chemical evolution of organic compounds in the solar system and beyond.

  16. Mineral remains of early life on Earth? On Mars?

    Science.gov (United States)

    Iberall, Robbins E.; Iberall, A.S.

    1991-01-01

    The oldest sedimentary rocks on Earth, the 3.8-Ga Isua Iron-Formation in southwestern Greenland, are metamorphosed past the point where organic-walled fossils would remain. Acid residues and thin sections of these rocks reveal ferric microstructures that have filamentous, hollow rod, and spherical shapes not characteristic of crystalline minerals. Instead, they resemble ferric-coated remains of bacteria. Because there are no earlier sedimentary rocks to study on Earth, it may be necessary to expand the search elsewhere in the solar system for clues to any biotic precursors or other types of early life. A study of morphologies of iron oxide minerals collected in the southern highlands during a Mars sample return mission may therefore help to fill in important gaps in the history of Earth's earliest biosphere. -from Authors

  17. Jupiter and Planet Earth. [planetary and biological evolution and natural satellites

    Science.gov (United States)

    1975-01-01

    The evolution of Jupiter and Earth are discussed along with their atmospheres, the radiation belts around both planets, natural satellites, the evolution of life, and the Pioneer 10. Educational study projects are also included.

  18. Electrical energy sources for organic synthesis on the early earth

    Science.gov (United States)

    Chyba, Christopher; Sagan, Carl

    1991-01-01

    It is pointed out that much of the contemporary origin-of-life research uses the original estimates of Miller and Urey (1959) for terrestrial energy dissipation by lightning and coronal discharges being equal to 2 x 10 to the 19th J/yr and 6 x 10 to the 19th J/yr, respectively. However, data from experiments that provide analogues to naturally-occurring lightning and coronal discharges indicate that lightning energy yields for organic synthesis (nmole/J) are about one order of magnitude higher than the coronal discharge yields. This suggests that, on early earth, organic production by lightning may have dominated that due to coronal emission. New values are recommended for lightning and coronal discharge dissipation rates on the early earth, 1 x 10 to the 18th J/yr and 5 x 10 to the 17th J/yr, respectively.

  19. Hydrogen-nitrogen greenhouse warming in Earth's early atmosphere.

    Science.gov (United States)

    Wordsworth, Robin; Pierrehumbert, Raymond

    2013-01-04

    Understanding how Earth has sustained surface liquid water throughout its history remains a key challenge, given that the Sun's luminosity was much lower in the past. Here we show that with an atmospheric composition consistent with the most recent constraints, the early Earth would have been significantly warmed by H(2)-N(2) collision-induced absorption. With two to three times the present-day atmospheric mass of N(2) and a H(2) mixing ratio of 0.1, H(2)-N(2) warming would be sufficient to raise global mean surface temperatures above 0°C under 75% of present-day solar flux, with CO(2) levels only 2 to 25 times the present-day values. Depending on their time of emergence and diversification, early methanogens may have caused global cooling via the conversion of H(2) and CO(2) to CH(4), with potentially observable consequences in the geological record.

  20. Electrical energy sources for organic synthesis on the early earth

    Science.gov (United States)

    Chyba, Christopher; Sagan, Carl

    1991-01-01

    It is pointed out that much of the contemporary origin-of-life research uses the original estimates of Miller and Urey (1959) for terrestrial energy dissipation by lightning and coronal discharges being equal to 2 x 10 to the 19th J/yr and 6 x 10 to the 19th J/yr, respectively. However, data from experiments that provide analogues to naturally-occurring lightning and coronal discharges indicate that lightning energy yields for organic synthesis (nmole/J) are about one order of magnitude higher than the coronal discharge yields. This suggests that, on early earth, organic production by lightning may have dominated that due to coronal emission. New values are recommended for lightning and coronal discharge dissipation rates on the early earth, 1 x 10 to the 18th J/yr and 5 x 10 to the 17th J/yr, respectively.

  1. Follow the Carbon: Isotopic Labeling Studies of Early Earth Aerosol.

    Science.gov (United States)

    Hicks, Raea K; Day, Douglas A; Jimenez, Jose L; Tolbert, Margaret A

    2016-11-01

    Despite the faint young Sun, early Earth might have been kept warm by an atmosphere containing the greenhouse gases CH4 and CO2 in mixing ratios higher than those found on Earth today. Laboratory and modeling studies suggest that an atmosphere containing these trace gases could lead to the formation of organic aerosol haze due to UV photochemistry. Chemical mechanisms proposed to explain haze formation rely on CH4 as the source of carbon and treat CO2 as a source of oxygen only, but this has not previously been verified experimentally. In the present work, we use isotopically labeled precursor gases and unit-mass resolution (UMR) and high-resolution (HR) aerosol mass spectrometry to examine the sources of carbon and oxygen to photochemical aerosol formed in a CH4/CO2/N2 atmosphere. UMR results suggest that CH4 contributes 70-100% of carbon in the aerosol, while HR results constrain the value from 94% to 100%. We also confirm that CO2 contributes approximately 10% of the total mass to the aerosol as oxygen. These results have implications for the geochemical interpretations of inclusions found in Archean rocks on Earth and for the astrobiological potential of other planetary atmospheres. Key Words: Atmosphere-Early Earth-Planetary atmospheres-Carbon dioxide-Methane. Astrobiology 16, 822-830.

  2. Thermochemical Evolution of Earth's Core with Magnesium Precipitation

    Science.gov (United States)

    O'Rourke, J. G.; Stevenson, D. J.

    2014-12-01

    Vigorous convection within Earth's outer core drives a dynamo that has sustained a global magnetic field for at least 3.5 Gyr. Traditionally, people invoke three energy sources for the dynamo: thermal convection from cooling and freezing, compositional convection from light elements expelled by the growing inner core, and, perhaps, radiogenic heating from potassium-40. New theoretical and experimental work, however, indicates that the thermal and electrical conductivities of the outer core may be as much as three times higher than previously assumed. The implied increase in the adiabatic heat flux casts doubt on the ability of the usual mechanisms to explain the dynamo's longevity. Here, we present a quantitative model of the crystallization of magnesium-bearing minerals from the cooling core—a plausible candidate for the missing power source. Recent diamond-anvil cell experiments suggest that magnesium can partition into core material if thermodynamic equilibrium is achieved at high temperatures (>5000 K). We develop a model for core/mantle differentiation in which most of the core forms from material equilibrated at the base of a magma ocean as Earth slowly grows, but a small portion (~10%) equilibrated at extreme conditions in the aftermath of a giant impact. We calculate the posterior probability distribution for the original concentrations of magnesium and other light elements (chiefly oxygen and silicon) in the core, constrained by partitioning experiments and the observed depletion of siderophile elements in Earth's mantle. We then simulate the thermochemical evolution of cores with plausible compositions and thermal structures from the end of accretion to the present, focusing on the crystallization of a few percent of the initial core as ferropericlase and bridgmanite. Finally, we compute the associated energy release and verify that our final core compositions are consistent with the available seismological data.

  3. The early evolution of massive black holes

    CERN Document Server

    Volonteri, Marta

    2009-01-01

    Massive black holes are nowadays believed to reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~0.1%), are linked to the evolution of galactic structure. When did it all start? In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.

  4. Thermal evolution of Earth with magnesium precipitation in the core

    Science.gov (United States)

    O'Rourke, Joseph G.; Korenaga, Jun; Stevenson, David J.

    2017-01-01

    Vigorous convection in Earth's core powers our global magnetic field, which has survived for over three billion years. In this study, we calculate the rate of entropy production available to drive the dynamo throughout geologic time using one-dimensional parameterizations of the evolution of Earth's core and mantle. To prevent a thermal catastrophe in models with realistic Urey ratios, we avoid the conventional scaling for plate tectonics in favor of one featuring reduced convective vigor for hotter mantle. We present multiple simulations that capture the effects of uncertainties in key parameters like the rheology of the lower mantle and the overall thermal budget. Simple scaling laws imply that the heat flow across the core/mantle boundary was elevated by less than a factor of two in the past relative to the present. Another process like the precipitation of magnesium-bearing minerals is therefore required to sustain convection prior to the nucleation of the inner core roughly one billion years ago, especially given the recent, upward revision to the thermal conductivity of the core. Simulations that include precipitation lack a dramatic increase in entropy production associated with the formation of the inner core, complicating attempts to determine its age using paleomagnetic measurements of field intensity. Because mantle dynamics impose strict limits on the amount of heat extracted from the core, we find that the addition of radioactive isotopes like potassium-40 implies less entropy production today and in the past. On terrestrial planets like Venus with more sluggish mantle convection, even precipitation of elements like magnesium may not sustain a dynamo if cooling rates are too slow.

  5. Implications for the Earth of the early dynamical environment

    Science.gov (United States)

    Kaula, W. M.; Cooperman, S. A.

    1985-01-01

    The formation of the Earth, was mainly from sizeable bodies: perhaps moon sized. Models of interaction among small planetesimals which take into account only close encounters all lead to the formation of moon sized objects, thus leading to several 100 in the inner solar system. Longer term interactions, such as secular resonance sweepings, are needed to get these planetesimals together to form the observed terrestrial bodies. After the accumulation of the Earth, during which core formation certainly occurred, further impacts probably influenced the locations of rifting centers in the system of mantle convection and crustal differentiation. They may have affected craton stabilization by promoting lateral heterogeneity, but had little influence on the key problem of early recycling of sial.

  6. Spinal cord evolution in early Homo.

    Science.gov (United States)

    Meyer, Marc R; Haeusler, Martin

    2015-11-01

    The discovery at Nariokotome of the Homo erectus skeleton KNM-WT 15000, with a narrow spinal canal, seemed to show that this relatively large-brained hominin retained the primitive spinal cord size of African apes and that brain size expansion preceded postcranial neurological evolution. Here we compare the size and shape of the KNM-WT 15000 spinal canal with modern and fossil taxa including H. erectus from Dmanisi, Homo antecessor, the European middle Pleistocene hominins from Sima de los Huesos, and Pan troglodytes. In terms of shape and absolute and relative size of the spinal canal, we find all of the Dmanisi and most of the vertebrae of KNM-WT 15000 are within the human range of variation except for the C7, T2, and T3 of KNM-WT 15000, which are constricted, suggesting spinal stenosis. While additional fossils might definitively indicate whether H. erectus had evolved a human-like enlarged spinal canal, the evidence from the Dmanisi spinal canal and the unaffected levels of KNM-WT 15000 show that unlike Australopithecus, H. erectus had a spinal canal size and shape equivalent to that of modern humans. Subadult status is unlikely to affect our results, as spinal canal growth is complete in both individuals. We contest the notion that vertebrae yield information about respiratory control or language evolution, but suggest that, like H. antecessor and European middle Pleistocene hominins from Sima de los Huesos, early Homo possessed a postcranial neurological endowment roughly commensurate to modern humans, with implications for neurological, structural, and vascular improvements over Pan and Australopithecus. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. The Bombardment of the Earth During the Hadean and Early Archean Eras

    Science.gov (United States)

    Marchi, S.; Bottke, W. F.; Elkins-Tanton, L. T.; Morbidelli, A.; Wuennemann, K.; Kring, D. A.; Bierhaus, M.

    2013-12-01

    Our knowledge of the Earth during the Hadean and early Archean eons (ca 4.5-3.5 Ga) is very limited, mainly because few rocks older than 3.8 Ga have been found (e.g. Harrison 2009). Hadean-era zircons have allowed us to glean important insights into this era, but their data has led to considerably different evolution models for the evolution of the early Earth; some predict a hellish world dominated by a molten surface with a sporadic steam atmosphere (e.g. Pollack 1997), while others have predicted a tranquil, cool surface with stable oceans (e.g. Wilde et al 2001; Valley et al 2002). To understand whether either model (or both) could be right, we believe it is useful to quantitatively examine the post Moon-forming impact bombardment of the early Earth. Over the last several years, through a combination of observations (e.g., Marchi et al 2012), theoretical models (e.g., Bottke et al 2012), and geochemical constraints from lunar rock (e.g. highly siderophile elements -HSE- abundances delivered to the Moon by impactors; the global number of lunar basins; the record of Archean-era impact spherule beds on Earth; Walker 2009; Neumann et al 2012), we have constructed a calibrated model of the early lunar impactor flux (Morbidelli et al 2012). Our results have now been extrapolated to the Earth, where they can make predictions about its early bombardment. Using a Monte Carlo code to account for the stochastic nature of major impacts, and constraining our results by the estimated HSE abundances of Earth's mantle (that were presumably delivered by impactors; Walker 2009; Bottke et al. 2010), we find the following trends. In the first ~100-200 Myr after the formation of the Moon, which we assume was created ~4.5 Ga, the Earth was almost entirely resurfaced by impacts. This bombardment, which included numerous D > 1000 km diameter impactors, should have vigorously mixed the crust and upper mantle. Between ~4.1-4.3 Ga, the impactor flux steadily decreased; though an uptick

  8. The Early Evolution of Mars' Crust

    Science.gov (United States)

    Samuel, H.; Baratoux, D.; Kurita, K.

    2014-12-01

    The Mars crustal density and thickness have been recently re-evaluated using petrological constraints from remote sensing, in-situ data, and SNC meteorites. This work indicates that the present-day Martian crust is denser and thicker than previously proposed if essentially basaltic in composition. As a consequence, the average crustal thickness would be commensurable with the depth of the basalt/eclogite transition, re-opening the question of crustal recycling on Early Mars and more generally throughout all its history. We have therefore investigated the conditions under which a thick ancient crust with an eclogitic root could survive through the history of Mars using numerical modelling. Delamination may occur if the combination of poorly constrained physical parameters induces the presence of gravitationally unstable layers and favors a rheological decoupling. To study the conditions and the time scales for the occurrence of crustal delamination on Mars, we investigated the influence of critical parameters for a plausible range of values corresponding to the Martian mantle. For each case we follow the dynamic evolution over geological times of a three-layer system (i.e., crust-mantle with a distinction between low pressure, buoyant basaltic crust and higher pressure, denser eclogitic material). We systematically varied four governing parameters within plausible ranges: (1) the basalt-eclogite transition depth, (2) the density difference between the mantle and the basaltic crust, (3) the density difference between the eclogitic crust and the lithosphere & mantle, (4) the viscous rheology. These experiments allow determining the average Martian crustal thickness at early and late evolutionary stages.

  9. The Earth's core formation and development: evidence from evolution of tectonomagmatic processes and paleomagnetic data

    Science.gov (United States)

    Sharkov, E. V.

    2011-12-01

    Many geologists confident that the core provides modern tectonic and magmatic activity on the Earth, which explains our interest in this topic, and vice versa we can use evolution of tectonomagmatic processes throughout the Earth's (and other terrestrial planetary bodies) history for reconstruction of the core formation and evolution. Most researchers, follow to V. Safronov (1972) and A. Ringwood (1979), confident that the Earth has occurred due to accumulation of hypothetical chemically homogeneous planetesimals, composed by chondrite material, ie, as a result of homogeneous accretion. However, this single-stage chondrite model of accretion is inconsistent with fact of cardinal change of tectonomagmatic processes on the terrestrial planets in the middle stages of their development. For example, the critical irreversible change of the Earth's tectonomagmatic evolution occurred in range 2.35-2.0 Ga, when geochemical-enriched Fe-Ti picrites and basalts firstly appeared in large quantities and first geological evidence of plate tectonics showed up (Sharkov, Bogatikov, 2010). We suggest that these changes were linked with ascending of mantle superplumes of the second generation (thermochemical), originated at the the boundary of liquid iron core and silicate mantle, in similar way as the modern plumes. All terrestrial planetary bodies (Earth, Venus, Mars, Mercury, and the Moon) have a similar structure, consist of iron core and silicate envelope, and developed at the same scenario, which provide for drastic irreversible change in character of tectonomagmatic processes at the middle stages of their evolution (Sharkov, Bogatikov, 2009). Such a situation can be realized only in case: (1) the terrestrial planetary bodies originally had heterogeneous structure, and (2) their heating occurred from the top down accompanied by cooling of outer shells. As a result, material of the primordial cores, where enriched material survived, were remained a long time untouched. It

  10. Dynamical Evolution of the Earth-Moon Progenitors - Whence Theia?

    CERN Document Server

    Quarles, Billy

    2014-01-01

    We present integrations of a model Solar System with five terrestrial planets (beginning ~30-50 Myr after the formation of primitive Solar System bodies) in order to determine the preferred regions of parameter space leading to a giant impact that resulted in the formation of the Moon. Our results indicate which choices of semimajor axes and eccentricities for Theia (the proto-Moon) at this epoch can produce a late Giant Impact, assuming that Mercury, Venus, and Mars are near the current orbits. We find that the likely semimajor axis of Theia, at the epoch when our simulations begin, depends on the assumed mass ratio of Earth-Moon progenitors (8/1, 4/1, or 1/1). The low eccentricities of the terrestrial planets are most commonly produced when the progenitors have similar semimajor axes at the epoch when our integrations commence. Additionally, we show that mean motion resonances among the terrestrial planets and perturbations from the giant planets can affect the dynamical evolution of the system leading to a...

  11. On the Early Evolution of Young Starbursts

    CERN Document Server

    Rosa-Gonzalez, Daniel; Terlevich, Elena; Terlevich, Roberto

    2009-01-01

    We studied the radio properties of very young massive regions of star formation in HII galaxies, with the aim of detecting episodes of recent star formation in an early phase of evolution where the first supernovae start to appear. The observed radio spectral energy distribution (SED) covers a behaviour range; 1) there are galaxies where the SED is characterized by a synchrotron-type slope, 2) galaxies with a thermal slope, and 3) galaxies with possible free-free absorption at long wavelengths. The latter SED represents a signature of massive star clusters that are still well inside the progenitor molecular cloud. Based on the comparison of the star formation rates (SFR) determined from the recombination lines and those determined from the radio emission we find that SFR(Ha) is on average five times higher than SFR(1.4 GHz). These results suggest that the emission of these galaxies is dominated by a recent and massive star formation event in which the first supernovae (SN) just started to explode. We conclude...

  12. Photosynthetic microbial mats today, on early Earth, (and on early Mars?)

    Science.gov (United States)

    Des Marais, D. J.

    2008-05-01

    Marine hypersaline cyanobacterial mats offer insights about their ancient ancestors, whose fossil record is 3.43 billion years old. Studies of mat microbiota have greatly expanded the known diversity of ancient microbial lineages. Their evolution was shaped by mat microenvironments, which can differ substantially from their surroundings. Oxygenic photosynthesis perhaps developed in microbial mats and probably triggered a major evolutionary transformation and diversification of the early biosphere. Gross primary production rates in cyanobacterial mats can rival the most productive ecosystems known. Sunlight changes in intensity and spectral composition as it penetrates mats, and counteracting gradients of O2 and sulfide shape the chemical microenvironment. A combination of benefits and hazards of light, O2 and sulfide promotes the allocation of the various essential mat processes between light and dark periods and to various depths in the mat. Close inspection has revealed surprises, for example: anoxygenic phototrophs inside cyanobacterial sheaths, record- high sulfate reduction rates in O2-saturated conditions, and high H2 fluxes into overlying waters. Diverse organic biomarker compounds have been documented that are amenable to long-term preservation. Such coordinated observations of populations, processes and products are making fundamental questions in ecology accessible. Cyanobacterial mats have robust fossil records in part because they populated stable continental platforms and margins, contributing to sediments having high preservation potential. Proterozoic cyanobacterial fossils and organic biomarkers are well documented. The 3.43 Ga Strelley Pool cherts, W. Australia, reveal diverse stromatolites that populated a partially restricted, low-energy shallow hypersaline basin. Molecular studies of extant bacteria hint that early chlorophyll-utilizing photosynthesizers required geochemical sources of reductants. Did these anoxygenic phototrophs once sustain an

  13. The role of rotation on the evolution of dynamo generated magnetic fields in Super Earths

    CERN Document Server

    Zuluaga, Jorge I

    2011-01-01

    Planetary magnetic fields could have a role on the evolution of planetary atmospheres and the required conditions for the emergence and evolution of life (habitability). After briefly review the current efforts to study the evolution of dynamo generated magnetic fields in massive earth-like rocky planets (Super Earths), we take the results from thermal evolution models and updated scaling laws for convection driven magnetodynamos to predict the evolution of the local Rossby number, the basic indicator of core magnetic field geometry and regime. We study the dependence of this property on planetary mass and rotation rate. Previous works have paid Attention only to the evolution of dipolar dominant core magnetic fields assuming rapid rotating planets. Here we extend these results including consistently the effects of rotation on the evolution of planetary magnetic field properties and obtain global constraints to the existence of intense protective magnetic fields in rapidly and slowly rotating Super Earths. We...

  14. Records of our Early Biosphere Illuminate our Origins and Guide our Search for Life Beyond Earth

    Science.gov (United States)

    DesMarais, David J.

    2003-01-01

    A scientific "mission of exploration to early Earth" will help us chart the distribution of life elsewhere. We must discriminate between attributes of biospheres that are universal versus those attributes that represent principally the outcomes of long-term survival specifically on Earth. In addition to the basic physics and chemistry of matter, the geologic evolution of rocky habitable planets and their climates might be similar elsewhere in the Universe. Certain key agents that drive long-term environmental change (e.g., stellar evolution, impacts, geothermal heat flow, tectonics, etc.) can help us to reconstruct ancient climates and to compare their evolution among populations of Earth- like planets. Early Earth was tectonically more active than today and therefore it exhaled reduced chemical species into the more oxidized surface environment at greater rates. This tectonic activity thus sustained oxidation-reduction reactions that provided the basis for the development of biochemical pathways that harvest chemical energy ("bioenergetics"). Most examples of bioenergetics today that extract energy by reacting oxidized and reduced chemicals in the environment were likely more pervasive among our microbial ancestors than are the presently known examples of photosynthesis. The geologic rock record indicates that, as early as 3.5 billion years ago (3.5 Ga), microbial biofilms were widespread within the coastal environments of small continents and tectonically unstable volcanic islands. Non oxygen-producing (non-oxygenic) photosynthesis preceded oxygenic photosynthesis, but all types of photosynthesis contributed substantially to the long-term increase in global primary biological productivity. Evidence of photosynthesis is tentative by 3.5 Ga and compelling by 2.7 Ga. Evidence of oxygenic photosynthesis is strong by 2.7 Ga and compelling by 2.3 Ga. These successive innovations transformed life from local communities that survived principally by catalyzing chemical

  15. The emergence and early evolution of biological carbon-fixation.

    Directory of Open Access Journals (Sweden)

    Rogier Braakman

    Full Text Available The fixation of CO₂ into living matter sustains all life on Earth, and embeds the biosphere within geochemistry. The six known chemical pathways used by extant organisms for this function are recognized to have overlaps, but their evolution is incompletely understood. Here we reconstruct the complete early evolutionary history of biological carbon-fixation, relating all modern pathways to a single ancestral form. We find that innovations in carbon-fixation were the foundation for most major early divergences in the tree of life. These findings are based on a novel method that fully integrates metabolic and phylogenetic constraints. Comparing gene-profiles across the metabolic cores of deep-branching organisms and requiring that they are capable of synthesizing all their biomass components leads to the surprising conclusion that the most common form for deep-branching autotrophic carbon-fixation combines two disconnected sub-networks, each supplying carbon to distinct biomass components. One of these is a linear folate-based pathway of CO₂ reduction previously only recognized as a fixation route in the complete Wood-Ljungdahl pathway, but which more generally may exclude the final step of synthesizing acetyl-CoA. Using metabolic constraints we then reconstruct a "phylometabolic" tree with a high degree of parsimony that traces the evolution of complete carbon-fixation pathways, and has a clear structure down to the root. This tree requires few instances of lateral gene transfer or convergence, and instead suggests a simple evolutionary dynamic in which all divergences have primary environmental causes. Energy optimization and oxygen toxicity are the two strongest forces of selection. The root of this tree combines the reductive citric acid cycle and the Wood-Ljungdahl pathway into a single connected network. This linked network lacks the selective optimization of modern fixation pathways but its redundancy leads to a more robust topology

  16. Hydrogen consumption by methanogens on the early Earth

    Science.gov (United States)

    Kral, T. A.; Brink, K. M.; Miller, S. L.; McKay, C. P.; Bada, J. L. (Principal Investigator)

    1998-01-01

    It is possible that the first autotroph used chemical energy rather than light. This could have been the main source of primary production after the initial inventory of abiotic organic material had been depleted. The electron acceptor most readily available for use by this first chemoautotroph would have been CO2. The most abundant electron donor may have been H2 that would have been outgassing from volcanoes at a rate estimated to be as large as 10(12) moles yr-1, as well as from photo-oxidation of Fe+2. We report here that certain methanogens will consume H2 down to partial pressures as low as 4 Pa (4 x 10(-5) atm) with CO2 as the sole carbon source at a rate of 0.7 ng H2 min-1 microgram-1 cell protein. The lower limit of pH2 for growth of methanogens can be understood on the basis that the pH2 needs to be high enough for one ATP to be synthesized per CO2 reduced. The pH2 values needed for growth measured here are consistent with those measured by Stevens and McKinley for growth of methanogens in deep basalt aquifers. H2-consuming autotrophs are likely to have had a profound effect on the chemistry of the early atmosphere and to have been a dominant sink for H2 on the early Earth after life began rather than escape from the Earth's atmosphere to space.

  17. Continental crust formation on early Earth controlled by intrusive magmatism

    Science.gov (United States)

    Rozel, A. B.; Golabek, G. J.; Jain, C.; Tackley, P. J.; Gerya, T.

    2017-05-01

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the “Plutonic squishy lid” tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  18. Continental crust formation on early Earth controlled by intrusive magmatism.

    Science.gov (United States)

    Rozel, A B; Golabek, G J; Jain, C; Tackley, P J; Gerya, T

    2017-05-18

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the "Plutonic squishy lid" tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  19. The early evolution of protostellar disks

    Science.gov (United States)

    Stahler, Steven W.; Korycansky, D. G.; Brothers, Maxwell J.; Touma, Jihad

    1994-01-01

    We consider the origin and intital growth of the disks that form around protostars during the collapse of rotating molecular cloud cores. These disks are assumed to be inviscid and pressure free, and to have masses small compared to those of their central stars. We find that there exist three distinct components-an outer disk, in which shocked gas moves with comparable azimuthal and radical velocities; and inner disk, where material follows nearly circular orbits, but spirals slowly toward the star because of the drag exerted by adjacent onfalling matter, and a turbulent ring adjoining the first two regions. Early in the evolution, i.e., soon after infalling matter begins to miss the star, only the outer disk is present, and the total mass acceration rate onto the protostar is undiminished. Once the outer disk boundary grows to more than 2.9 times the stellar radius, first the ring, and then the inner disk appear. Thereafter, the radii of all three components expand as t(exp 3). The mass of the ring increase with time and is always 13% of the total mass that has fallen from the cloud. Concurrently with the buildup of the inner disk and ring, the accretion rate onto the star falls off. However, the protostellar mass continue to rise, asymptotically as t(exp 1/4). We calculated the radiated flux from the inner and outer disk components due to the release of gravitational potential energy. The flux from the inner disk is dominant and rises steeply toward the stellar surface. We also determine the surface temperature of the inner disk as a function of radius. The total disk luminosity decreases slowly with time, while the contributions from the ring and inner disk both fall as t(exp -2).

  20. Open system models of isotopic evolution in Earth's silicate reservoirs: Implications for crustal growth and mantle heterogeneity

    Science.gov (United States)

    Kumari, Seema; Paul, Debajyoti; Stracke, Andreas

    2016-12-01

    An open system evolutionary model of the Earth, comprising continental crust (CC), upper and lower mantle (UM, LM), and an additional isolated reservoir (IR) has been developed to study the isotopic evolution of the silicate Earth. The model is solved numerically at 1 Myr time steps over 4.55 Gyr of Earth history to reproduce both the present-day concentrations and isotope ratios of key radioactive decay systems (Rb-Sr, Sm-Nd, and U-Th-Pb) in these terrestrial reservoirs. Various crustal growth scenarios - continuous versus episodic and early versus late crustal growth - and their effect on the evolution of Sr-Nd-Pb isotope systematics in the silicate reservoirs have been evaluated. Modeling results where the present-day UM is ∼60% of the total mantle mass and a lower mantle that is non-primitive reproduce the estimated geochemical composition and isotope ratios in Earth's silicate reservoirs. The isotopic evolution of the silicate Earth is strongly affected by the mode of crustal growth; only an exponential crustal growth pattern with crustal growth since the early Archean satisfactorily explains the chemical and isotopic evolution of the crust-mantle system and accounts for the so-called Pb paradoxes. Assuming that the OIB source is located in the deeper mantle, our model could, however, not reproduce its target ɛNd of +4.6 for the UM, which has been estimated from the average isotope ratios of 32 individual ocean island localities. Hence, either mantle plumes sample the LM in a non-representative way, or the simplified model set-up does not capture the full complexity of Earth's lower mantle (Nd isotope) evolution. Compared to the results obtained for a 4.55 Ga Earth, a model assuming a protracted U-Pb evolution of silicate Earth by ca. 100 Myr reproduces a slightly better fit for the Pb isotope ratios in Earth's silicate reservoirs. One notable feature of successful models is the early depletion of incompatible elements (as well as rapid decrease in Th/U) in

  1. The early history of chance in evolution.

    Science.gov (United States)

    Pence, Charles H

    2015-04-01

    Work throughout the history and philosophy of biology frequently employs 'chance', 'unpredictability', 'probability', and many similar terms. One common way of understanding how these concepts were introduced in evolution focuses on two central issues: the first use of statistical methods in evolution (Galton), and the first use of the concept of "objective chance" in evolution (Wright). I argue that while this approach has merit, it fails to fully capture interesting philosophical reflections on the role of chance expounded by two of Galton's students, Karl Pearson and W.F.R. Weldon. Considering a question more familiar from contemporary philosophy of biology--the relationship between our statistical theories of evolution and the processes in the world those theories describe--is, I claim, a more fruitful way to approach both these two historical actors and the broader development of chance in evolution.

  2. Biomarkers as tracers for life on early earth and Mars

    Science.gov (United States)

    Simoneit, B. R.; Summons, R. E.; Jahnke, L. L.

    1998-01-01

    Biomarkers in geological samples are products derived from biochemical (natural product) precursors by reductive and oxidative processes (e.g., cholestanes from cholesterol). Generally, lipids, pigments and biomembranes are preserved best over longer geological times and labile compounds such as amino acids, sugars, etc. are useful biomarkers for recent times. Thus, the detailed characterization of biomarker compositions permits the assessment of the major contributing species of extinct and/or extant life. In the case of the early Earth, work has progressed to elucidate molecular structure and carbon isotropic signals preserved in ancient sedimentary rocks. In addition, the combination of bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems permits the modeling of the nature, behavior and preservation potential of primitive microbial communities. This approach uses combined molecular and isotopic analyses to characterize lipids produced by cultured bacteria (representative of ancient strains) and to test a variety of culture conditions which affect their biosynthesis. On considering Mars, the biomarkers from lipids and biopolymers would be expected to be preserved best if life flourished there during its early history (3.5-4 x 10(9) yr ago). Both oxidized and reduced products would be expected. This is based on the inferred occurrence of hydrothermal activity during that time with the concomitant preservation of biochemically-derived organic matter. Both known biomarkers (i.e., as elucidated for early terrestrial samples and for primitive terrestrial microbiota) and novel, potentially unknown compounds should be characterized.

  3. Petrochronology in constraining early Archean Earth processes and environments: Barberton greenstone belt, South Africa

    Science.gov (United States)

    Grosch, Eugene

    2017-04-01

    Analytical and petrological software developments over the past decade have seen rapid innovation in high-spatial resolution petrological techniques, for example, laser-ablation ICP-MS, secondary ion microprobe (SIMS, nano-SIMS), thermodynamic modelling and electron microprobe microscale mapping techniques (e.g. XMapTools). This presentation will focus on the application of petrochronology to ca. 3.55 to 3.33 billion-year-old metavolcanic and sedimentary rocks of the Onverwacht Group, shedding light on the earliest geologic evolution of the Paleoarchean Barberton greenstone belt (BGB) of South Africa. The field, scientific drilling and petrological research conducted over the past 8 years, aims to illustrate how: (a) LA-ICP-MS and SIMS U-Pb detrital zircon geochronology has helped identify the earliest tectono-sedimentary basin and sediment sources in the BGB, as well as reconstructing geodynamic processes as early as ca. 3.432 billion-years ago; (b) in-situ SIMS multiple sulphur isotope analysis of sulphides across various early Archean rock units help to reconstruct atmospheric, surface and subsurface environments on early Archean Earth and (c) the earliest candidate textural traces for subsurface microbial life can be investigated by in-situ LA-ICP-MS U-Pb dating of titanite, micro-XANES Fe-speciation analysis and metamorphic microscale mapping. Collectively, petrochronology combined with high-resolution field mapping studies, is a powerful multi-disciplinary approach towards deciphering petrogenetic and geodynamic processes preserved in the Paleoarchean Barberton greenstone belt of South Africa, with implications for early Archean Earth evolution.

  4. Isotopic constraints on the age and early differentiation of the Earth.

    Science.gov (United States)

    McCulloch, M T

    1996-03-01

    The Earth's age and early differentiation history are re-evaluated using updated isotopic constraints. From the most primitive terrestrial Pb isotopic compositions found at Isua Greenland, and the Pilbara of Western Australia, combined with precise geochronology of these localities, an age 4.49 +/- 0.02 Ga is obtained. This is interpreted as the mean age of core formation as U/Pb is fractionated due to sequestering of Pb into the Earth's core. The long-lived Rb-Sr isotopic system provides constraints on the time interval for the accretion of the Earth as Rb underwent significant depletion by volatile loss during accretion of the Earth or its precursor planetesimals. A primitive measured 87Sr/86Sr initial ratio of 0.700502 +/- 10 has been obtained for an early Archean (3.46 Ga) barite from the Pilbara Block of Western Australia. Using conservative models for the evolution of Rb/Sr in the early Archean mantle allows an estimate to be placed on the Earth's initial Sr ratio at approximately 4.50 Ga, of 0.69940 +/- 10. This is significantly higher than that measured for the Moon (0.69900 +/- 2) or in the achondrite, Angra dos Reis (0.69894 +/- 2) and for a Rb/Sr ratio of approximately 1/2 of chondrites corresponds to a mean age for accretion of the Earth of 4.48 + /- 0.04 Ga. The now extinct 146Sm-142Nd (T1/2(146)=103 l0(6)yrs) combined with the long-lived 147Sm-143Nd isotopic systematics can also be used to provide limits on the time of early differentiation of the Earth. High precision analyses of the oldest (3.8-3.9 Ga) Archean gneisses from Greenland (Amitsoq and Akilia gneisses), and Canada (Acasta gneiss) do not show measurable (> +/- l0ppm) variations of 142Nd, in contrast to the 33 ppm 142Nd excess reported for an Archean sample. The general lack of 142Nd variations, combined with the presence of highly positive epsilon 143 values (+4.0) at 3.9 Ga, indicates that the record of large-scale Sm/Nd fractionation events was not preserved in the early-Earth from 4

  5. Writing on the earth: Early European travellers to South Africa

    Directory of Open Access Journals (Sweden)

    M. Sienaert

    1996-05-01

    Full Text Available The issue of land in South Africa has always been problematic. This is to be expected in a country whose history has been one of colonisation, contested borders and, in the more recent apartheid past, of legalised removals of people from the land. In recent post-colonial theory too, the notion of spatiality has proved to be significant: to write a history of a country and its people is to write a spatial history through the processes of naming, mapping, classifying and painting. Our project in this article is to explore some of the ways in which early European travellers to South Africa traced their presence in this country, and in so doing began a chapter of “writing on the earth", the ideological marks of which linger on into this century.

  6. Cometary delivery of organic molecules to the early Earth.

    Science.gov (United States)

    Chyba, C F; Thomas, P J; Brookshaw, L; Sagan, C

    1990-07-27

    It has long been speculated that Earth accreted prebiotic organic molecules important for the origins of life from impacts of carbonaceous asteroids and comets during the period of heavy bombardment 4.5 x 10(9) to 3.8 x 10(9) years ago. A comprehensive treatment of comet-asteroid interaction with the atmosphere, surface impact, and resulting organic pyrolysis demonstrates that organics will not survive impacts at velocities greater than about 10 kilometers per second and that even comets and asteroids as small as 100 meters in radius cannot be aerobraked to below this velocity in 1-bar atmospheres. However, for plausible dense (10-bar carbon dioxide) early atmospheres, we find that 4.5 x 10(9) years ago Earth was accreting intact cometary organics at a rate of at least approximately 10(6) to 10(7) kilograms per year, a flux that thereafter declined with a half-life of approximately 10(8) years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, approximately 3 x 10(12) kilograms and approximately 6 x 10(14) kilograms, respectively.

  7. Transformation and diversification in early mammal evolution.

    Science.gov (United States)

    Luo, Zhe-Xi

    2007-12-13

    Evolution of the earliest mammals shows successive episodes of diversification. Lineage-splitting in Mesozoic mammals is coupled with many independent evolutionary experiments and ecological specializations. Classic scenarios of mammalian morphological evolution tend to posit an orderly acquisition of key evolutionary innovations leading to adaptive diversification, but newly discovered fossils show that evolution of such key characters as the middle ear and the tribosphenic teeth is far more labile among Mesozoic mammals. Successive diversifications of Mesozoic mammal groups multiplied the opportunities for many dead-end lineages to iteratively evolve developmental homoplasies and convergent ecological specializations, parallel to those in modern mammal groups.

  8. Stochastic evolution of cosmological parameters in the early universe

    Indian Academy of Sciences (India)

    C Sivakumar; Moncy V John; K Babu Joseph

    2001-04-01

    We develop a stochastic formulation of cosmology in the early universe, after considering the scatter in the redshift-apparent magnitude diagram in the early epochs as an observational evidence for the non-deterministic evolution of early universe. We consider the stochastic evolution of density parameter in the early universe after the inflationary phase qualitatively, under the assumption of fluctuating factor in the equation of state, in the Fokker–Planck formalism. Since the scale factor for the universe depends on the energy density, from the coupled Friedmann equations we calculated the two variable probability distribution function assuming a flat space geometry

  9. NASA's Earth Observing System Data and Information System - Many Mechanisms for On-Going Evolution

    Science.gov (United States)

    Ramapriyan, H. K.

    2012-12-01

    NASA's Earth Observing System Data and Information System has been serving a broad user community since August 1994. As a long-lived multi-mission system serving multiple scientific disciplines and a diverse user community, EOSDIS has been evolving continuously. It has had and continues to have many forms of community input to help with this evolution. Early in its history, it had inputs from the EOSDIS Advisory Panel, benefited from the reviews by various external committees and evolved into the present distributed architecture with discipline-based Distributed Active Archive Centers (DAACs), Science Investigator-led Processing Systems and a cross-DAAC search and data access capability. EOSDIS evolution has been helped by advances in computer technology, moving from an initially planned supercomputing environment to SGI workstations to Linux Clusters for computation and from near-line archives of robotic silos with tape cassettes to RAID-disk-based on-line archives for storage. The network capacities have increased steadily over the years making delivery of data on media almost obsolete. The advances in information systems technologies have been having an even greater impact on the evolution of EOSDIS. In the early days, the advent of the World Wide Web came as a game-changer in the operation of EOSDIS. The metadata model developed for the EOSDIS Core System for representing metadata from EOS standard data products has had an influence on the Federal Geographic Data Committee's metadata content standard and the ISO metadata standards. The influence works both ways. As ISO 19115 metadata standard has developed in recent years, EOSDIS is reviewing its metadata to ensure compliance with the standard. Improvements have been made in the cross-DAAC search and access of data using the centralized metadata clearing house (EOS Clearing House - ECHO) and the client Reverb. Given the diversity of the Earth science disciplines served by the DAACs, the DAACs have developed a

  10. Photochemistry of methane in the earth's early atmosphere

    Science.gov (United States)

    Kasting, J. F.; Zahnle, K J.; Walker, J. C. G.

    1983-01-01

    The photochemical behavior of methane in the early terrestrial atmosphere is investigated with a detailed model in order to determine how much CH4 might have been present and what types of higher hydroocarbons could have been formed. It is found that any primordial methane accumulated during the course of earth accretion would have been dissipated by photochemical reactions in the atmosphere in a geologically short period of time after the segregation of the core. Abiotic sources of methane are not likely to have been large enough to sustain CH4 mixing ratios as high as 10 to the -6th, the threshold for a possible methane greenhouse, with a CO-rich atmosphere being a possible exception. After the origin of life an increasing biogenic source of methane may have driven CH4 mixing ratios well above 10 to the 6th. The rise of atmospheric oxygen in the early Proterozoic may have led to a more rapid photochemical destruction of methane, lowering the mixing ratio to its present value.

  11. THE LONG TIME BEHAVIORS OF NON-AUTONOMOUS EVOLUTION SYSTEM DESCRIBING GEOPHYSICAL FLOW WITHIN THE EARTH

    Institute of Scientific and Technical Information of China (English)

    ZHAO Chunshan; LI Kaitai; HUANG Aixiang

    2002-01-01

    In this paper, the long time behaviors of non-autonomous evolution system describing geophysical flow within the earth are studied. The uniqueness and existence of the solution to the evolution system and the existence of uniform attractor are proven.Moreover, the upper bounds of the uniform attractor's Hausdorff and Fractal dimensions are obtained.

  12. Reactive Oxygen Species on the Early Earth and Survival of Bacteria

    Science.gov (United States)

    Balk, Melikea; Mason, Paul; Stams, Alfons J. M.; Smidt, Hauke; Freund, Friedemann; Rothschild, Lynn

    2011-01-01

    An oxygen-rich atmosphere appears to have been a prerequisite for complex, multicellular life to evolve on Earth and possibly elsewhere in the Universe. However it remains unclear how free oxygen first became available on the early Earth. A potentially important, and as yet poorly constrained pathway, is the production of oxygen through the weathering of rocks and release into the near-surface environment. Reactive Oxygen Species (ROS), as precursors to molecular oxygen, are a key step in this process, and may have had a decisive impact on the evolution of life, present and past. ROS are generated from minerals in igneous rocks during hydrolysis of peroxy defects, which consist of pairs of oxygen anions oxidized to the valence state -1 and during (bio) transformations of iron sulphide minerals. ROS are produced and consumed by intracellular and extracellular reactions of Fe, Mn, C, N, and S species. We propose that, despite an overall reducing or neutral oxidation state of the macroenvironment and the absence of free O2 in the atmosphere, organisms on the early Earth had to cope with ROS in their microenvironments. They were thus under evolutionary pressure to develop enzymatic and other defences against the potentially dangerous, even lethal effects of oxygen and its derived ROS. Conversely it appears that microorganisms learned to take advantage of the enormous reactive potential and energy gain provided by nascent oxygen. We investigate how oxygen might be released through weathering. We test microorganisms in contact with rock surfaces and iron sulphides. We model bacteria such as Deionococcus radiodurans and Desulfotomaculum, Moorella and Bacillus species for their ability to grow or survive in the presence of ROS. We examine how early Life might have adapted to oxygen.

  13. How do Early Impacts Modulate the Tectonic, Magnetic and Climatic Evolutions of Terrestrial Planets?

    Science.gov (United States)

    Jellinek, M.; Jackson, M. G.; Lenardic, A.; Weller, M. B.

    2015-12-01

    The landmark discovery showing that the 142Nd/144Nd ratio of the accessible modern terrestrial mantle is greater than ordinary-chondrites has remarkable implications for the formation, as well as the geodynamic, magnetic and climatic histories of Earth. If Earth is derived from ordinary chondrite precursors, mass balance requires that a missing reservoir with 142Nd/144Nd lower than ordinary chondrites was isolated from the accessible mantle within 20-30 Myr following accretion. Critically for Earth evolution, this reservoir hosts the equivalent of the modern continents' budget of radioactive heat-producing elements (U, Th and K). If this reservoir was lost to space through mechanical erosion by early impactors, the planet's radiogenic heat generation is 18-45% lower than chondrite-based compositional estimates. Recent geodynamic calculations suggest that this reduced heat production will favor the emergence of Earth-like plate tectonics. However, parameterized thermal history calculations favor a relatively recent transition from mostly Atlantic-sized plates to the current plate tectonic mode characterized predominantly by the subduction of Pacific-sized plates. Such a transition in the style of Earth's plate tectonics is also consistent with a delayed dynamo and an evolving rate of volcanic outgassing that ultimately favors Earth's long-term clement climate. By contrast, relatively enhanced radiogenic heat production related to a less early impact erosion reduces the likelihood of present day plate tectonics: A chondritic Earth has a stronger likelihood to evolve as a Venus-like planet characterized by potentially wild swings in tectonic and climatic regime. Indeed, differences in internal heat production related to varying extents of impact erosion may exert strong control over Earth's climate and explain aspects of the differences among the current climatic regimes of Earth, Venus and Mars.

  14. Directly detecting the evolution of early-type galaxies

    NARCIS (Netherlands)

    Trager, Scott; Faber, SM; Dressler, A; Renzini, A; Bender, R

    2005-01-01

    We describe observations focused on understanding the epochs and timescales of the formation and evolution of early-type galaxies, particularly those in clusters. We show that while early-type cluster galaxies are on average older and closer to coeval than their counterparts in the field, significan

  15. Continuing Evolution: The Rhode Island Early Childhood Summer Institute

    Science.gov (United States)

    Horm, Diane M.; O'Keefe, Beverly; Diffendale, Charlotte; Cohen, Amy; Schennum, Ruth; Pucciarelli, Larry; Collins, Cheryl; Merrifield, Margaret; Nardone, Virginia; Martin, Marilyn; Bryan, Linda; DeRobbio, Gail

    2004-01-01

    This narrative chronicles the continued evolution and development of the Rhode Island Early Childhood Summer Institute, an intensive 5-day inservice professional development program designed for educational leaders from various sectors of the early care and education field. The goal is to review the continued use of successful practices…

  16. Early Phases of Protoplanetary Disk Evolution

    NARCIS (Netherlands)

    Kamp, Inga; Macchetto, FD

    2010-01-01

    It is widely accepted that planetary systems form from protoplanetary disks, and observations of the dust reveal significant grain growth over timescales of a few million years. However, we know little about the gas processing in the first 10-20 Myr of disk evolution. This is the phase where protopl

  17. The early evolution of cooperation in humans

    NARCIS (Netherlands)

    Czárán, T.; Aanen, Duur K.

    2016-01-01

    The evolution of cooperation is difficult to understand, because cheaters — individuals who profit without cooperating themselves — have a benefit in interaction with cooperators. Cooperation among humans is even more difficult to understand, because cooperation occurs in large groups, making cheati

  18. Oxygenation of Earth's atmosphere and its impact on the evolution of nitrogen-based metabolisms

    Science.gov (United States)

    Papineau, D.; Mojzsis, S. J.

    2002-12-01

    The evolution of metabolic pathways is closely linked to the evolution of the redox state of the terrestrial atmosphere. Nitrogen has been an essential biological element since the emergence of life when reduced nitrogen compounds (e.g. ammonia) were utilized in the prebiotic synthesis of proteins and nucleic acids. The nitrogen isotopic composition of sediments has been used to trace the origin of sedimentary organic matter in the rock record. Nitrogen is therefore suitable as a biosignature to trace the emergence of life on Earth or other planetary bodies as well as to follow the subsequent evolution of the biosphere in response to global redox changes. Evidence is strong that biological nitrogen fixation evolved very early in the history of life. The Last Common Ancestor (LCA) on Earth was most likely capable of nitrogen fixation as seen from the phylogenetic distribution of nitrogen-fixing organisms in both the domains of Bacteria and Archaea. Phylogenetic trees plotted with nitrogen-fixing gene (Nif) sequences from lineages of Bacteria and Archaea suggest that the Nif genes originated in a common ancestor of the two domains. Other phylogenetic analyses have also demonstrated that the paralogous duplication of the nifDK and nifEN operons, central to nitrogen fixation, predated the divergence of Archaea from Bacteria and therefore occurred prior to the emergence of the LCA. Although the same may be true for denitrification, this metabolic pathway probably did not become dominant until atmospheric pO2 increased between ~2.4 to 1.9 Ga during the Great Oxygenation Event (GOE). Recent work has shown a general depletion in 15N content of Archean (pre-2.5 Ga) relative to Phanerozoic (<540 Ma) kerogens. Studies have shown that the distribution of the δ15N values in kerogens shift from negative values in the Early Archean (from -6 to +6‰ with an average near 0‰ ) to approximately contemporary positive values (from +2 to +10‰ with an average at +6‰ ) by the

  19. Early Earth plume-lid tectonics: A high-resolution 3D numerical modelling approach

    Science.gov (United States)

    Fischer, R.; Gerya, T.

    2016-10-01

    Geological-geochemical evidence point towards higher mantle potential temperature and a different type of tectonics (global plume-lid tectonics) in the early Earth (>3.2 Ga) compared to the present day (global plate tectonics). In order to investigate tectono-magmatic processes associated with plume-lid tectonics and crustal growth under hotter mantle temperature conditions, we conduct a series of 3D high-resolution magmatic-thermomechanical models with the finite-difference code I3ELVIS. No external plate tectonic forces are applied to isolate 3D effects of various plume-lithosphere and crust-mantle interactions. Results of the numerical experiments show two distinct phases in coupled crust-mantle evolution: (1) a longer (80-100 Myr) and relatively quiet 'growth phase' which is marked by growth of crust and lithosphere, followed by (2) a short (∼20 Myr) and catastrophic 'removal phase', where unstable parts of the crust and mantle lithosphere are removed by eclogitic dripping and later delamination. This modelling suggests that the early Earth plume-lid tectonic regime followed a pattern of episodic growth and removal also called episodic overturn with a periodicity of ∼100 Myr.

  20. Continental growth and mantle hydration as intertwined feedback cycles in the thermal evolution of Earth

    Science.gov (United States)

    Höning, Dennis; Spohn, Tilman

    2016-06-01

    A model of Earth's continental coverage and mantle water budget is discussed along with its thermal evolution. The model links a thermal evolution model based on parameterized mantle convection with a model of a generic subduction zone that includes the oceanic crust and a sedimentary layer as carriers of water. Part of the subducted water is used to produce continental crust while the remainder is subducted into the mantle. The total length of the subduction zones is calculated from the total surface area of continental crust assuming randomly distributed continents. The mantle viscosity is dependent of temperature and the water concentration. Sediments are generated by continental crust erosion, and water outgassing at mid-oceanic ridges closes the water cycle. We discuss the strongly coupled, non-linear model using a phase plane defined by the continental coverage and mantle water concentration. Fixed points are found in the phase plane at which the rates of change of both variables are zero. These fixed points evolve with time, but in many cases, three fixed points emerge of which two are stable and an intermediate point is unstable with respect to continental coverage. With initial conditions from a Monte-Carlo scheme we calculate evolution paths in the phase plane and find a large spread of final states that all have a mostly balanced water budget. The present day observed 40% continental surface coverage is found near the unstable fixed point. Our evolution model suggests that Earth's continental coverage formed early and has been stable for at least 1.5 Gyr. The effect of mantle water regassing (and mantle viscosity depending on water concentration) is found to lower the present day mantle temperature by about 120 K, but the present day mantle viscosity is affected little. The water cycle thus complements the well-known thermostat effect of viscosity and mantle temperature. Our results further suggest that the biosphere could impact the feedback cycles by

  1. A view of early cellular evolution.

    Science.gov (United States)

    Mikelsaar, R

    1987-01-01

    Some recent puzzling data on mitochondria put in question their place on the phylogenetic tree. A hypothesis, the archigenetic hypothesis, is presented, which generally agrees with Woese-Fox's concept of the common origin of eubacteria, archaebacteria, and eukaryotic hosts. However, for the first time, a case is made for the evolution of mitochondria from the ancient predecessors of pro- and eukaryotes (protobionts), not from eubacteria. Animal, fungal, and plant mitochondria are considered to be endosymbionts derived from independent free-living cells (mitobionts), which, having arisen at different developmental stages of protobionts, retained some of their ancient primitive features of the genetic code and the transcription-translation systems. The molecular-biological, bioenergetic, and paleontological aspects of this new concept of cellular evolution are discussed.

  2. Clues on the importance of comets in the origin and evolution of the atmospheres of Titan and Earth

    CERN Document Server

    Trigo-Rodriguez, Josep M

    2011-01-01

    Earth and Titan are two planetary bodies formed far from each other. Nevertheless the chemical composition of their atmospheres exhibits common indications of being produced by the accretion, plus ulterior in-situ processing of cometary materials. This is remarkable because while the Earth formed in the inner part of the disk, presumably from the accretion of rocky planetesimals depleted in oxygen and exhibiting a chemical similitude with enstatite chondrites, Titan formed within Saturn's sub-nebula from oxygen- and volatile-rich bodies, called cometesimals. From a cosmochemical and astrobiological perspective the study of the H, C, N, and O isotopes on Earth and Titan could be the key to decipher the processes occurred in the early stages of formation of both planetary bodies. The main goal of this paper is to quantify the presumable ways of chemical evolution of both planetary bodies, in particular the abundance of CO and N2 in their early atmospheres. In order to do that the primeval atmospheres and evolut...

  3. Astrophysics and Weak Form of Panspermia Hypothesis and Exogenous Factors in the Evolution of the Earth

    Science.gov (United States)

    Adushkin, V. V.; Vityazev, A. V.; Glazachev, D. O.; Pechernikova, G. V.

    2014-10-01

    The problems of the origin of Earth and life are fundamental in the modern science. We, relying on the data of resent years, contemplate a new course of research in this old problem. On the base of astrophysical data, obtained during the last 30-50 years, and the resent results of the study of small bodies in the Solar System (comets in particular) it is possible to combine the old idea about panspermia in a comprehensive sense and the search of the basis of life on the early Earth grounded on theoretical and laboratory data on the Earth evolution. Most likely, the Sun and a gas-and-dust disk surrounding it were created in a Giant molecular cloud near young giants - blue O-B-stars which ultraviolet radiation provided a weak chirality (to 15% of EEs) in organics of interstellar dust. Further a part of interstellar dust beyond orbits larger than 3-4 a.u. remained cold and then entered into the first planetesimals. The organics, after melting of interiors of the first planetesimals due to the heating by shortliving 26Al and 60Fe, sank, in the form of kerogens, into the core where formation of the first complex organic compounds began. This occurred in the first 3-4 Myr after the CAI. Apparently, it is necessary to look for anaerobic life in comets. In geosciences obtained various data banks, such as data on the endogenous activity of the Earth, mass extinctions of life and changes in biodiversity, impacts of cosmic bodies, inversions of the magnetic field, climate change, etc. The problem of cyclicity and correlation of all these processes is studied for 50 years. Results of spectral, wavelet and correlation analysis of the data series, representing some of these processes are given. We conclude, that most of them are cyclic, some of the periods are present in all the processes. The mechanisms of the influence of the galaxy on the processes occurring on the Earth are discussed.

  4. Tracing Earth's O2 Evolution Using Zn/Fe Systematics in Carbonates

    Science.gov (United States)

    Liu, X. M.; Hazen, R. M.; Kah, L. C.; Sverjensky, D. A.; Cui, H.; Kaufmann, A. J.

    2014-12-01

    Redox-sensitive major and trace elements in iron formations and black shales have been developed as proxies to reconstruct paleoenvironmental history in deep time [1, 2]. Many Proterozoic successions, however, contain abundant limestone and dolomite, and so carbonate-based redox proxies could help greatly to expand the paleoredox record in time and space. Most paleoenvironmental research on sedimentary rocks focuses on individual stratigraphic successions; here, however, we adopt a complementary strategy, analyzing a large suite of Mesozoic, Paleozoic, and Precambrian samples that enables us to make global statistical statements about elemental abundances through time. Here we explore the use of Zn/Fe ratios as proxies to trace the evolution of redox profiles in marine basins, based on analysis of major and trace element concentrations in micro-drilled carbonate rocks that are well characterized in terms of stratigraphy, environmental setting, and petrology. Consistent with previous studies, we observed a two step increase of mean Zn/Fe ratios in carbonates through Earth history: at the Paleoproterozoic Great Oxidation Event and during the later Neoproterozoic Oxidation Event. Diagenetic alteration is always an issue for carbonate rocks, and so we carefully screened these carbonates for possible late diagenetic effects and hydrothermal alteration. Individual samples may still bear a trace element signature of early diagenesis, but our statistical approach indicates that despite diagenetic issues, meaningful trends can be discerned in the data. It is unlikely that changes in depositional environment, secular evolution of the mantle, and/or directional change in continental inputs greatly influenced the observed trace element behavior. Therefore, Zn/Fe ratios in shallow marine carbonates have the potential to provide a useful tracer for the redox evolution of the oceans and the rise of atmospheric O2. References:[1] Sahoo et al. (2012) Ocean oxygenation in the wake

  5. Evolution of Life Cycles in Early Amphibians

    Science.gov (United States)

    Schoch, Rainer R.

    2009-05-01

    Many modern amphibians have biphasic life cycles with aquatic larvae and terrestrial adults. The central questions are how and when this complicated ontogeny was established, and what is known about the lives of amphibians in the Paleozoic. Fossil evidence has accumulated that sheds light on the life histories of early amphibians, the origin of metamorphosis, and the transition to a fully terrestrial existence. The majority of early amphibians were aquatic or amphibious and underwent only gradual ontogenetic changes. Developmental plasticity played a major role in some taxa but was restricted to minor modification of ontogeny. In the Permo-Carboniferous dissorophoids, a condensation of crucial ontogenetic steps into a short phase (metamorphosis) is observed. It is likely that the origin of both metamorphosis and neoteny falls within these taxa. Fossil evidence also reveals the sequence of evolutionary changes: apparently, the ontogenetic change in feeding, not the transition to a terrestrial existence per se, made a drastic metamorphosis necessary.

  6. The role of Jupiter in driving Earth's orbital evolution

    CERN Document Server

    Horner, Jonathan; Koch, F Elliot

    2014-01-01

    In coming years, the first truly Earth-like planets will be discovered orbiting other stars, and the search for signs of life on these worlds will begin. However, such observations will be hugely time-consuming and costly, and so it will be important to determine which of those planets represent the best prospects for life elsewhere. One of the key factors in such a decision will be the climate variability of the planet in question - too chaotic a climate might render a planet less promising as a target for our initial search for life elsewhere. On the Earth, the climate of the last few million years has been dominated by a series of glacial and interglacial periods, driven by periodic variations in the Earth's orbital elements and axial tilt. These Milankovitch cycles are driven by the gravitational influence of the other planets, and as such are strongly dependent on the architecture of the Solar system. Here, we present the first results of a study investigating the influence of the orbit of Jupiter on the...

  7. The stepwise evolution of early life driven by energy conservation.

    Science.gov (United States)

    Ferry, James G; House, Christopher H

    2006-06-01

    Two main theories have emerged for the origin and early evolution of life based on heterotrophic versus chemoautotrophic metabolisms. With the exception of a role for CO, the theories have little common ground. Here we propose an alternative theory for the early evolution of the cell which combines principal features of the widely disparate theories. The theory is based on the extant pathway for conversion of CO to methane and acetate, largely deduced from the genomic analysis of the archaeon Methanosarcina acetivorans. In contrast to current paradigms, we propose that an energy-conservation pathway was the major force which powered and directed the early evolution of the cell. We envision the proposed primitive energy-conservation pathway to have developed sometime after a period of chemical evolution but prior to the establishment of diverse protein-based anaerobic metabolisms. We further propose that energy conservation played the predominant role in the later evolution of anaerobic metabolisms which explains the origin and evolution of extant methanogenic pathways.

  8. Simulating Stellar Cluster Formation and Early Evolution

    Science.gov (United States)

    Wall, Joshua; McMillan, Stephen L. W.; Mac Low, Mordecai-Mark; Ibañez-Mejia, Juan; Portegies Zwart, Simon; Pellegrino, Andrew

    2017-01-01

    We present our current development of a model of stellar cluster formation and evolution in the presence of stellar feedback. We have integrated the MHD code Flash into the Astrophysical Multi-Use Software Environment (AMUSE) and coupled the gas dynamics to an N-body code using a Fujii gravity bridge. Further we have integrated feedback from radiation using the FERVENT module for Flash, supernovae by thermal and kinetic energy injection, and winds by kinetic energy injection. Finally we have developed a method of implementing star formation using the Jeans criterion of the gas. We present initial results from our cluster formation model in a cloud using self-consistent boundary conditions drawn from a model of supernova-driven interstellar turbulence.

  9. Synthesis of nitrous oxide by lightning in the early anoxic Earth's atmosphere

    Science.gov (United States)

    Navarro, K. F.; Navarro-Gonzalez, R.; McKay, C. P.

    2013-12-01

    Carbon dioxide (CO2) was the main atmospheric component of the early Earth's atmosphere and exerted a key role in climate by maintaining a hydrosphere during a primitive faint Sun [1]; however, CO2 was eventually removed from the atmosphere by rock weathering and sequestered in the Earth's crust and mantle [1]. Nitric oxide (NO) was fixed by lightning discharges at a rate of 1×1016 molecules J-1 in CO2 (50-80%) rich atmospheres [2]. As the levels of atmospheric CO2 dropped to 20%, the production rate of NO by lightning rapidly decreased to 2×1014 molecules J-1 and then slowly diminished to 1×1014 molecules J-1 at CO2 levels of about 2.5% [2]. In order to maintain the existence of liquid water in the early Earth, it is required to warm up the planet with other greenhouse gases such as methane (CH4) [3]. Here we report an experimental study of the effects of lightning discharges on the nitrogen fixation rate during the evolution of the Earth's early atmosphere from 10 to 0.8 percent of carbon dioxide with methane concentrations from 0 to 1,000 ppm in molecular nitrogen. Lightning was simulated in the laboratory by a plasma generated with a pulsed Nd-YAG laser [2]. Our results show that the production of NO by lightning is independent of the presence of methane but drops from 3×1014 molecules J-1 in 10% CO2 to 5×1013 molecules J-1 in 1% CO2. Surprisingly, nitrous oxide (N2O) is also produced at a rate of 4×1013 molecules J-1 independent of the levels of CH4 and CO2. N2O is produced by lightning in the contemporaneous oxygenated Earth's atmosphere at a comparable rate of (0.4-1.5)×1013 molecules J-1 [4, 5], but was not detected in nitrogen-carbon dioxide mixtures in the absence of oxygen [6]. The only previously reported abiotic synthesis of N2O was by corona discharges in rich CO2 atmospheres (20-80%) with a production rate of 8×1012 molecules J-1 [6]; however at lower CO2 (atmosphere was the main source of N2O in nitrogen dominated atmospheres. N2O is not

  10. Effects of differentiation on the geodynamics of the early Earth

    Science.gov (United States)

    Piccolo, Andrea; Kaus, Boris; White, Richard; Johnson, Tim

    2016-04-01

    Archean geodynamic processes are not well understood, but there is general agreement that the mantle potential temperature was higher than present, and that as a consequence significant amounts of melt were produced both in the mantle and any overlying crust. This has likely resulted in crustal differentiation. An early attempt to model the geodynamic effects of differentiation was made by Johnson et al. (2014), who used numerical modeling to investigate the crust production and recycling in conjunction with representative phase diagrams (based on the inferred chemical composition of the primary melt in accordance with the Archean temperature field). The results of the simulations show that the base of the over-thickened primary basaltic crust becomes gravitational unstable due to the mineral assemblage changes. This instability leads to the dripping of dense material into the mantle, which causes an asthenospheric return flow, local partial melting and new primary crust generation that is rapidly recycled in to mantle. Whereas they gave important insights, the previous simulations were simplified in a number of aspects: 1) the rheology employed was viscous, and both elasticity and pressure-dependent plasticity were not considered; 2) extracted mantle melts were 100% transformed into volcanic rocks, whereas on the present day Earth only about 20-30% are volcanic and the remainder is plutonic; 3) the effect of a free surface was not studied in a systematic manner. In order to better understand how these simplifications affect the geodynamic models, we here present additional simulations to study the effects of each of these parameters. Johnson, T.E., Brown, M., Kaus, B., and VanTongeren, J.A., 2014, Delamination and recycling of Archaean crust caused by gravitational instabilities: Nature Geoscience, v. 7, no. 1, p. 47-52, doi: 10.1038/NGEO2019.

  11. Membrane heredity and early chloroplast evolution.

    Science.gov (United States)

    Cavalier-Smith, T

    2000-04-01

    Membrane heredity was central to the unique symbiogenetic origin from cyanobacteria of chloroplasts in the ancestor of Plantae (green plants, red algae, glaucophytes) and to subsequent lateral transfers of plastids to form even more complex photosynthetic chimeras. Each symbiogenesis integrated disparate genomes and several radically different genetic membranes into a more complex cell. The common ancestor of Plantae evolved transit machinery for plastid protein import. In later secondary symbiogeneses, signal sequences were added to target proteins across host perialgal membranes: independently into green algal plastids (euglenoids, chlorarachneans) and red algal plastids (alveolates, chromists). Conservatism and innovation during early plastid diversification are discussed.

  12. What traces of life can we expect on Mars? Lessons from the early Earth

    Science.gov (United States)

    Westall, F.

    2008-09-01

    mats in the littoral environment, photosynthesisers need unlimited access to sunlight. The very existence of these microorganisms at ~3.5 Ga demonstrates that, although the Earth was at the cold edge of the habitable zone, the oceans were not frozen. Ice would have limited the penetration of light to the microorganisms (depending on thickness). From the microbial perspective, the lack of a global ocean on early Mars is irrelevant [11,12], as is the probability that standing bodies of water would have been covered with ice [13]. There would have been sufficient amounts of liquid water to support chemolithotrophic and heterotrophic microbial life beneath the ice covered basins (N.B. Lake Vostok on Antarctica has liquid water beneath 3 km of ice that is also fed from hydrothermal sources. Genetic traces of these hydrothermal microorganisms are frozen into the base of the ice [14]). Hydrothermal activity associated with volcanism and impact events would provide sufficient heat for liquid water (and life) to be present. However, the presence of ice on the early water bodies would have hindered the evolutionary development of martian life. Since photosynthetic microorganisms require access to sunlight, and since the earliest photosynthesisers were probably substratebound, the presence of ice on the surfaces of water bodies and, especially at their edges in the littoral environment, would have inhibited the development of photosynthesis. Moreover, the early degradation of the environmental conditions on Mars (between 4.2- 3.5 Ga [12]) would have been a further detriment to the evolution of martian life. Conclusions It is most likely that life appeared on Mars independently of the Earth since the planet had the same ingredients and probably the same starting conditions as the Earth. However, the early degradation of its environmental conditions and the fact that the planet was outside the habitable zone with probable ice-covered water surfaces would have limited the

  13. The Early Years: The Earth-Sun System

    Science.gov (United States)

    Ashbrook, Peggy

    2015-01-01

    We all experience firsthand many of the phenomena caused by Earth's Place in the Universe (Next Generation Science Standard 5-ESS1; NGSS Lead States 2013) and the relative motion of the Earth, Sun, and Moon. Young children can investigate phenomena such as changes in times of sunrise and sunset (number of daylight hours), Moon phases, seasonal…

  14. Evolution of an Early Titan Atmosphere: Comment

    CERN Document Server

    Johnson, Robert E; Volkov, Alexey N

    2015-01-01

    Escape of an early atmosphere from Titan, during which time NH3 could be converted by photolysis into the present N2 dominated atmosphere, is an important problem in planetary science. Recently Gilliam and Lerman (2014) estimated escape driven by the surface temperature and pressure, which we show gave loss rates that are orders of magnitude too large. Their model, related to Jeans escape from an isothermal atmosphere, was used to show that escape driven only by surface heating would deplete the atmospheric inventory of N for a suggested Titan accretion temperature of ~355 K. Therefore, they concluded that the accretion temperature must be lower in order to retain the present Titan atmosphere. Here we show that the near surface atmospheric temperature is essentially irrelevant for determining the atmospheric loss rate from Titan and that escape is predominantly driven by solar heating of the upper atmosphere. We also give a rough estimate of the escape rate in the early solar system (~10^4 kg/s) consistent wi...

  15. Cell evolution and Earth history: stasis and revolution

    OpenAIRE

    Cavalier-Smith, Thomas

    2006-01-01

    This synthesis has three main parts. The first discusses the overall tree of life and nature of the last common ancestor (cenancestor). I emphasize key steps in cellular evolution important for ordering and timing the major evolutionary innovations in the history of the biosphere, explaining especially the origins of the eukaryote cell and of bacterial flagella and cell envelope novelties. Second, I map the tree onto the fossil record and discuss dates of key events and their biogeochemical i...

  16. Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

    OpenAIRE

    Hu, Wenqian; Shin, Yung C.; King, Galen B.

    2012-01-01

    Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11. Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number den...

  17. The origin and early evolution of dinosaurs.

    Science.gov (United States)

    Langer, Max C; Ezcurra, Martin D; Bittencourt, Jonathas S; Novas, Fernando E

    2010-02-01

    The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and

  18. Early Stages of the Evolution of Life: a Cybernetic Approach

    Science.gov (United States)

    Melkikh, Alexey V.; Seleznev, Vladimir D.

    2008-08-01

    Early stages of the evolution of life are considered in terms of control theory. A model is proposed for the transport of substances in a protocell possessing the property of robustness with regard to changes in the environmental concentration of a substance.

  19. The early evolution of the Archegoniatae: a re-appraisal

    NARCIS (Netherlands)

    Meeuse, A.D.J.

    1966-01-01

    After a re-appraisal of the alternative hypotheses concerning the origin and the early evolution of the archegoniate land plants, the postulation of a thalassiophytic group of precursors with free isomorphic alternating generations by Church, Zimmermann, and several others is rejected. Several versi

  20. The early evolution of the Archegoniatae: a re-appraisal

    NARCIS (Netherlands)

    Meeuse, A.D.J.

    1966-01-01

    After a re-appraisal of the alternative hypotheses concerning the origin and the early evolution of the archegoniate land plants, the postulation of a thalassiophytic group of precursors with free isomorphic alternating generations by Church, Zimmermann, and several others is rejected. Several

  1. The role of rotation in the evolution of dynamo-generated magnetic fields in Super Earths

    Science.gov (United States)

    Zuluaga, Jorge I.; Cuartas, Pablo A.

    2012-01-01

    Planetary magnetic fields could impact the evolution of planetary atmospheres and have a role in the determination of the required conditions for the emergence and evolution of life (planetary habitability). We study here the role of rotation in the evolution of dynamo-generated magnetic fields in massive Earth-like planets, Super Earths (1-10 M⊕). Using the most recent thermal evolution models of Super Earths (Gaidos, E., Conrad, C.P., Manga, M., Hernlund, J. [2010]. Astrophys. J. 718, 596-609; Tachinami, C., Senshu, H., Ida, S. [2011]. Astrophys. J. 726, 70) and updated scaling laws for convection-driven dynamos, we predict the evolution of the local Rossby number. This quantity is one of the proxies for core magnetic field regime, i.e. non-reversing dipolar, reversing dipolar and multipolar. We study the dependence of the local Rossby number and hence the core magnetic field regime on planetary mass and rotation rate. Previous works have focused only on the evolution of core magnetic fields assuming rapidly rotating planets, i.e. planets in the dipolar regime. In this work we go further, including the effects of rotation in the evolution of planetary magnetic field regime and obtaining global constraints to the existence of intense protective magnetic fields in rapidly and slowly rotating Super Earths. We find that the emergence and continued existence of a protective planetary magnetic field is not only a function of planetary mass but also depend on rotation rate. Low-mass Super Earths ( M ≲ 2 M⊕) develop intense surface magnetic fields but their lifetimes will be limited to 2-4 Gyrs for rotational periods larger than 1-4 days. On the other hand and also in the case of slowly rotating planets, more massive Super Earths ( M ≳ 2 M⊕) have weak magnetic fields but their dipoles will last longer. Finally we analyze tidally locked Super Earths inside and outside the habitable zone of GKM stars. Using the results obtained here we develop a classification of

  2. [World"--an unlikely scenario of the life origin and early ecolution on Earth].

    Science.gov (United States)

    Bregestowski, P D

    2015-01-01

    The most widely accepted modern scenario of prebiotic evolution that led to the emergence of the first cells on our planet is the "RNA World"--a hypothetical period of the early Earth's biosphere, when the information transfer and all the processes necessary for the functioning of the primary systems were provided by replicating RNA molecules. The essence of the "RNA World" hypothesis is based on two postulates: 1) at the initial stages of the origin of life, RNA molecules performed all functions necessary for reproduction and replication of biological molecules: informational, catalytic and structural; 2) at a certain stage of evolution arose separation of RNA and DNA, appeared genetically encoded proteins and occurred a transition to the modern world of living systems functioning. However, the analysis shows that the hypothesis of "RNA World" has a number of unsurmountable problems of chemical and informational nature. The biggest of them are: a) the unreliability of the initial components synthesis; b) a catastrophic rise of polynucleotide chains instability with their elongation; c) catastrophically low probability of formation of sequences possessing meaningful information; d) lack of a mechanism determining the regularities division of the membrane vesicles permeable to nitrogen bases and other RNA components; e) lack of driving forces for the transition from the RNA world to the much more complex world based on DNA and RNA. Therefore, the "RNA World" scenario seems unlikely.

  3. Ocean Fertilization from Giant Icebergs on Earth and Early Mars

    Science.gov (United States)

    Uceda, E. R.; Fairen, A. G.; Rodriguez, J. A. P.; Woodworth-Lynas, C.

    2016-05-01

    Assuming that life existed on Mars coeval to glacial activity, enhanced concentrations of organic carbon could be anticipated near iceberg trails, analogous to what is observed in polar oceans on Earth.

  4. The Evolution and Future of Earth's Nitrogen Cycle

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Glazer, Alexander N.; Falkowski, Paul G.

    2010-01-01

    , the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N2O). Microbial processes......Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by similar to 2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however...... will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated....

  5. Earth science: Extraordinary world

    Science.gov (United States)

    Day, James M. D.

    2016-09-01

    The isotopic compositions of objects that formed early in the evolution of the Solar System have been found to be similar to Earth's composition -- overturning notions of our planet's chemical distinctiveness. See Letters p.394 & p.399

  6. Crystallization of silicon dioxide and compositional evolution of the Earth's core.

    Science.gov (United States)

    Hirose, Kei; Morard, Guillaume; Sinmyo, Ryosuke; Umemoto, Koichio; Hernlund, John; Helffrich, George; Labrosse, Stéphane

    2017-03-02

    The Earth's core is about ten per cent less dense than pure iron (Fe), suggesting that it contains light elements as well as iron. Modelling of core formation at high pressure (around 40-60 gigapascals) and high temperature (about 3,500 kelvin) in a deep magma ocean predicts that both silicon (Si) and oxygen (O) are among the impurities in the liquid outer core. However, only the binary systems Fe-Si and Fe-O have been studied in detail at high pressures, and little is known about the compositional evolution of the Fe-Si-O ternary alloy under core conditions. Here we performed melting experiments on liquid Fe-Si-O alloy at core pressures in a laser-heated diamond-anvil cell. Our results demonstrate that the liquidus field of silicon dioxide (SiO2) is unexpectedly wide at the iron-rich portion of the Fe-Si-O ternary, such that an initial Fe-Si-O core crystallizes SiO2 as it cools. If crystallization proceeds on top of the core, the buoyancy released should have been more than sufficient to power core convection and a dynamo, in spite of high thermal conductivity, from as early on as the Hadean eon. SiO2 saturation also sets limits on silicon and oxygen concentrations in the present-day outer core.

  7. The early evolution of the atmospheres of terrestrial planets

    CERN Document Server

    Raulin, François; Muller, Christian; Nixon, Conor; Astrophysics and Space Science Proceedings : Volume 35

    2013-01-01

    “The Early Evolution of the Atmospheres of Terrestrial Planets” presents the main processes participating in the atmospheric evolution of terrestrial planets. A group of experts in the different fields provide an update of our current knowledge on this topic. Several papers in this book discuss the key role of nitrogen in the atmospheric evolution of terrestrial planets. The earliest setting and evolution of planetary atmospheres of terrestrial planets is directly associated with accretion, chemical differentiation, outgassing, stochastic impacts, and extremely high energy fluxes from their host stars. This book provides an overview of the present knowledge of the initial atmospheric composition of the terrestrial planets. Additionally it includes some papers about the current exoplanet discoveries and provides additional clues to our understanding of Earth’s transition from a hot accretionary phase into a habitable world. All papers included were reviewed by experts in their respective fields. We are ...

  8. Rates of morphological evolution are heterogeneous in Early Cretaceous birds.

    Science.gov (United States)

    Wang, Min; Lloyd, Graeme T

    2016-04-13

    The Early Cretaceous is a critical interval in the early history of birds. Exceptional fossils indicate that important evolutionary novelties such as a pygostyle and a keeled sternum had already arisen in Early Cretaceous taxa, bridging much of the morphological gap between Archaeopteryx and crown birds. However, detailed features of basal bird evolution remain obscure because of both the small sample of fossil taxa previously considered and a lack of quantitative studies assessing rates of morphological evolution. Here we apply a recently available phylogenetic method and associated sensitivity tests to a large data matrix of morphological characters to quantify rates of morphological evolution in Early Cretaceous birds. Our results reveal that although rates were highly heterogeneous between different Early Cretaceous avian lineages, consistent patterns of significantly high or low rates were harder to pinpoint. Nevertheless, evidence for accelerated evolutionary rates is strongest at the point when Ornithuromorpha (the clade comprises all extant birds and descendants from their most recent common ancestors) split from Enantiornithes (a diverse clade that went extinct at the end-Cretaceous), consistent with the hypothesis that this key split opened up new niches and ultimately led to greater diversity for these two dominant clades of Mesozoic birds.

  9. Evolution of marine and terrestrial geobiodiversity in the history of the earth

    Institute of Scientific and Technical Information of China (English)

    SHEN ShuZhong; ZHOU ZhongHe

    2010-01-01

    @@ People have long been curious about the history of life on the earth-how many different species have existed,when they first occurred, how they evolved over geologic time, and how they reacted to major environmental crises.Although tremendous progresses have been made during the past decades, mysteries in evolution of life abound that remain to be deciphered.changes.

  10. Towards disruptions in Earth observation? New Earth Observation systems and markets evolution: Possible scenarios and impacts

    Science.gov (United States)

    Denis, Gil; Claverie, Alain; Pasco, Xavier; Darnis, Jean-Pierre; de Maupeou, Benoît; Lafaye, Murielle; Morel, Eric

    2017-08-01

    This paper reviews the trends in Earth observation (EO) and the possible impacts on markets of the new initiatives, launched either by existing providers of EO data or by new players, privately funded. After a presentation of the existing models, the paper discusses the new approaches, addressing both commercial and institutional markets. New concepts for the very high resolution markets, in Europe and in the US, are the main focus of this analysis. Two complementary perspectives are summarised: on the one hand, the type of system and its operational performance and, on the other, the related business models, concepts of operation and ownership schemes.

  11. A model for core formation in the early Earth

    Science.gov (United States)

    Jones, J. H.; Drake, M. J.

    1985-01-01

    Two basic types exogenous models were proposed to account for siderophile and chalcophile element abundances in the Earth's upper mantle. The first model requires that the Earth be depleted in volatiles and that, after a core formation event which extracted the most siderophile elements into the core, additional noble siderophile elements (Pt, Ir, Au) were added as a late veneer and mixed into the mantle. The second model postulates a reduced Earth with approximately CI elemental abundances in which a primary core forming event depleted all siderophile elements in the mantle. The plausibility of models which require fine scale mixing of chondritic material into the upper mantle is analyzed. Mixing in liquids is more efficient, but large degrees of silicate partial melting will facilitate the separation of magma from residual solids. Any external events affecting the upper mantle of the Earth should also be evident in the Moon; but siderophile and chalcophile element abundance patterns inferred for the mantles of the Earth and Moon differ. There appear to be significant physical difficulties associated with chondritic veneer models.

  12. Oxygen Evolution at Nickel Hydroxide Films Co-deposited Light Rare Earth Elements

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Composite nickel hydroxide films were prepared by cathodic co-electrodeposition from metal nitrate solution and characterized by cyclic voltammetry in 1.0 mol/L KOH solution. The codeposited light rare earth elements were lanthanum, cerium, praseodymium and neodymium. The films were analyzed by spectrophotometry and optical transmission. The results of the cyclic voltammetry in 1.0 mol/L KOH solution showed that the current density for oxygen evolution at the film electrode was affected by the co-deposited rare earth metal ions in the film. About 20 mA/cm2 increase of current density for oxygen evolution was found when the film was obtained from the solution with cerium (7% v/v) and nickel (93% v/v) nitrate. The effects of galvanostatic cathodic current density for the film formation on the oxygen evolution at the film electrodes from the alkaline were discussed.

  13. Evolution of the Earth and Origin of Life: The Role of Gas/Fluid Interactions with Rocks

    Science.gov (United States)

    Freund, Friedemann

    2001-01-01

    The work under the Cooperative Agreement will be centered on questions of the evolution of Life on the early Earth and possibly on Mars. It is still hotly debated whether the essential organic molecules were delivered to the early Earth from space (by comets, meteorites or interplanetary dust particles) or were generated in situ on Earth. Prior work that has shown that the matrix of igneous minerals is a medium in which progenitors of organic molecules assemble from H2O, C02 and N2 incorporated as minority "impurities" in minerals of igneous rocks during crystallization from H2O/CO2/N2-laden magmas. The underlying processes involve a redox. conversion whereby C, H, and N become chemically reduced, while 0 becomes oxidized to the peroxy state. During Year 02 the work will be divided into three tasks. Task 1: After carboxylic (fatty) acids and N-bearing compounds have been identified, other extractable organic molecules including lipids, oily substances and amino acids will be studied. Dedicated lipid analysis will be combined with gas chromatographic-mass spectroscopic (GCMS) analysis of organic compounds extracted from minerals and rocks. Task 2: Using infrared (IR) spectroscopy, C-H entities that are indicators for the organic progenitors in mineral matrices will be studied. A preliminary heating experiment with MgO single crystals has shown that the C-H entities can be pyrolyzed, causing the IR bands to disappear, but at room temperature the IR bands reappear in a matter of days to weeks. This work will be expanded, both by studying synthetic MgO crystals and olivine crystals from the Earth's upper mantle. The C-H bands will be compared to the published "organic" IR feature of dust in the interstellar medium (ISM) and interplanetary dust particles (IDP). Task 3: A paradox marks the evolution of early Life: Oxygen is highly toxic to primitive life, yet early organisms "learned" to detoxify reactive oxygen species, to utilize oxygen, and even produce it. Why would

  14. Ca isotope fingerprints of early crust-mantle evolution

    Science.gov (United States)

    Kreissig, K.; Elliott, T.

    2005-01-01

    The utility of 40Ca/ 44Ca as a tracer of pre-existing crustal contributions in early Archaean cratons has been explored to identify traces of Hadean crust and to assess the style of continental growth. The relatively short half-life of 40K (˜1.3 Gy) means that its decay to 40Ca occurs dominantly during early Earth History. If Archaean crust had a significant component derived from a more ancient protolith, as anticipated by "steady state" crustal evolution models, this should be clearly reflected in radiogenic 40Ca/ 44Ca ratios (or positive initial ɛ Ca) in different Archaean cratons. A high precision thermal ionisation technique has been used to analyse the 40Ca/ 44Ca ratios of plagioclase separates and associated whole rocks in ˜3.6 Ga (early Archaean) samples from Zimbabwe and West Greenland. Three out of four tonalite, trondhjemite, granodiorite (TTG) suite samples from Zimbabwe display initial 40Ca/ 44Ca ratios indistinguishable from our measured modern MORB value (i.e., ɛ Ca(3.6) ˜ 0). Greenland samples, however, are very diverse ranging from ɛ Ca(3.7) = 0.1 in mafic pillow lavas and felsic sheets from the Isua supracrustal belt, up to very radiogenic signatures (ɛ Ca(3.7) = 2.9) in both mafic rocks of the Akilia association and felsic TTG from the coastal Amîtsoq gneisses. At face value, these results imply the Zimbabwe crust is juvenile whereas most Greenland samples include an earlier crustal component. Yet the west Greenland craton, as with many Archaean localities, has experienced a complex geological history and the interpretation of age-corrected initial isotope values requires great care. Both felsic and mafic samples from Greenland display ɛ Ca(3.7) so radiogenic that they are not readily explained by crustal growth scenarios. The presence of such radiogenic 40Ca/ 44Ca found in low K/Ca plagioclases requires Ca isotope exchange between plagioclase and whole rock during later metamorphic event(s). In addition the unexpectedly radiogenic Ca

  15. The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

    Directory of Open Access Journals (Sweden)

    S. Maruyama

    2013-03-01

    To satisfy the tight conditions to make the Earth habitable, the formation mechanism of primordial Earth is an important factor. At first, a ‘dry Earth’ must be made through giant impact, followed by magma ocean to float nutrient-enriched primordial continents (anorthosite + KREEP. Late bombardment from asteroid belt supplied water to make 3–5 km thick ocean, and not from icy meteorites from Kuiper belt beyond cool Jupiter. It was essential to meet the above conditions that enabled the Earth as a habitable planet with evolved life forms. The tight constraints that we evaluate for birth and evolution of life on Earth would provide important guidelines for planetary scientists hunting for life in the exo-solar planets.

  16. New advances in understanding the heterohelicid planktic foraminifer early evolution

    Directory of Open Access Journals (Sweden)

    Marius Dan Georgescu

    2013-12-01

    Full Text Available Three Late Cretaceous lineages of heterohelicid planktic foraminifera, which evolved in the proximity of the Cenomanian/Turonian boundary, bring new data in understanding the group evolutionary history. Lunatriella Eicher and Worstell 1970a is a directional lineage of late Cenomanian-early Turonian age, which gradually develops peripheral backward extensions in the last-formed chambers. Steineckia Georgescu 2009a of the Turonian is the earliest heterohelicid lineage that evolved ornamentation consisting of pore mounds; a gap spanning the latest Turonian-early Santonian separates it from Laeviheterohelix Nederbragt 1991 of the late Santonian-Campanian, the second lineage that developed ornamentation consisting of pore mounds. Pseudoplanoglobulina Aliyulla 1977 evolved in the early Turonian and is the first heterohelicid lineage that developed multichamber growth in the adult stage; it became extinct in the Santonian. The three directional lineages show that the iterative and convergent evolution patterns occur extensively in the early heterohelicid history.

  17. What is the Emerging Knowledge of the Early Earth from the Oldest (>3.6 Ga) Rocks?

    Science.gov (United States)

    Bennett, V. C.; Nutman, A. P.

    2016-12-01

    Eoarchean to Hadean rocks are direct samples of early Earth chemistry and conditions and provide the ground-truth for models of early Earth formation, environments and evolution. Intensive investigations by many groups reveal rocks of this age comprise only one millionth of Earth's surface and are found in 9 areas of varying extent distributed worldwide. This record is of variable fidelity however, owing to metamorphic overprinting. The majority of the oldest rocks are high grade gneisses with protoliths from mid-crustal levels; the more rare supracrustal assemblages reflect early Earth's surface conditions and processes. First-order observations from supracrustal sequences at several localities and from 3.6 Ga to ≥3.9 Ga in age provide abundant evidence of liquid water at the Earth's surface with pillow basalts and chemical sedimentary rocks in the form of cherts, banded Fe formations and carbonates. Trace element patterns of these sedimentary rocks strongly resemble modern seawater compositions, except for the absence of redox sensitive Ce anomalies. Evidence for early life remains controversial and is mainly in the form of stable isotopic signatures of C and Fe. Our recent work from newly-discovered, exceptionally well-preserved 3.7 Ga sedimentary rocks and the deformed unconformity they rest on has provided the first evidence of Eoarchean intense weathering and shallow water sedimentary processes. Whilst the major and trace element compositions of Eoarchean gneisses have analogs in younger rocks in accord with a continuum of crust formation processes, radiogenic isotopic signatures from both long and short half-life decay schemes record an image of the Earth in transition from early differentiation processes, likely associated with planetary accretion and formation, to more modern styles. Most Eoarchean rocks possess extinct nuclide anomalies in the form of 142Nd and 182W isotopic signatures that are absent in modern terrestrial samples, and developed from

  18. Bryophyte diversity and evolution: windows into the early evolution of land plants.

    Science.gov (United States)

    Shaw, A Jonathan; Szövényi, Péter; Shaw, Blanka

    2011-03-01

    The "bryophytes" comprise three phyla of plants united by a similar haploid-dominant life cycle and unbranched sporophytes bearing one sporangium: the liverworts (Marchantiophyta), mosses (Bryophyta), and hornworts (Anthocerophyta). Combined, these groups include some 20000 species. As descendents of embryophytes that diverged before tracheophytes appeared, bryophytes offer unique windows into the early evolution of land plants. We review insights into the evolution of plant life cycles, in particular the elaboration of the sporophyte generation, the major lineages within bryophyte phyla, and reproductive processes that shape patterns of bryophyte evolution. Recent transcriptomic work suggests extensive overlap in gene expression in bryophyte sporophytes vs. gametophytes, but also novel patterns in the sporophyte, supporting Bower's antithetic hypothesis for origin of alternation of generations. Major lineages of liverworts, mosses, and hornworts have been resolved and general patterns of morphological evolution can now be inferred. The life cycles of bryophytes, arguably more similar to those of early embryophytes than are those in any other living plant group, provide unique insights into gametophyte mating patterns, sexual conflicts, and the efficacy and effects of spore dispersal during early land plant evolution.

  19. Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth.

    Science.gov (United States)

    Ćuk, Matija; Hamilton, Douglas P; Lock, Simon J; Stewart, Sarah T

    2016-11-17

    In the giant-impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however, the current lunar orbital inclination of five degrees requires a subsequent dynamical process that is still unclear. In addition, the giant-impact theory has been challenged by the Moon's unexpectedly Earth-like isotopic composition. Here we show that tidal dissipation due to lunar obliquity was an important effect during the Moon's tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations. We present a tidal evolution model starting with the Moon in an equatorial orbit around an initially fast-spinning, high-obliquity Earth, which is a probable outcome of giant impacts. Using numerical modelling, we show that the solar perturbations on the Moon's orbit naturally induce a large lunar inclination and remove angular momentum from the Earth-Moon system. Our tidal evolution model supports recent high-angular-momentum, giant-impact scenarios to explain the Moon's isotopic composition and provides a new pathway to reach Earth's climatically favourable low obliquity.

  20. Molecular clocks and the early evolution of metazoan nervous systems.

    Science.gov (United States)

    Wray, Gregory A

    2015-12-19

    The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation. © 2015 The Author(s).

  1. Early steps in plastid evolution: current ideas and controversies.

    Science.gov (United States)

    Bodył, Andrzej; Mackiewicz, Paweł; Stiller, John W

    2009-11-01

    Some nuclear-encoded proteins are imported into higher plant plastids via the endomembrane (EM) system. Compared with multi-protein Toc and Tic translocons required for most plastid protein import, the relatively uncomplicated nature of EM trafficking led to suggestions that it was the original transport mechanism for nuclear-encoded endosymbiont proteins, and critical for the early stages of plastid evolution. Its apparent simplicity disappears, however, when EM transport is considered in light of selective constraints likely encountered during the conversion of stable endosymbionts into fully integrated organelles. From this perspective it is more parsimonious to presume the early evolution of post-translational protein import via simpler, ancestral forms of modern Toc and Tic plastid translocons, with EM trafficking arising later to accommodate glycosylation and/or protein targeting to multiple cellular locations. This hypothesis is supported by both empirical and comparative data, and is consistent with the relative paucity of EM-based transport to modern primary plastids.

  2. Massive impact-induced release of carbon and sulfur gases in the early Earth's atmosphere

    Science.gov (United States)

    Marchi, S.; Black, B. A.; Elkins-Tanton, L. T.; Bottke, W. F.

    2016-09-01

    Recent revisions to our understanding of the collisional history of the Hadean and early-Archean Earth indicate that large collisions may have been an important geophysical process. In this work we show that the early bombardment flux of large impactors (>100 km) facilitated the atmospheric release of greenhouse gases (particularly CO2) from Earth's mantle. Depending on the timescale for the drawdown of atmospheric CO2, the Earth's surface could have been subject to prolonged clement surface conditions or multiple freeze-thaw cycles. The bombardment also delivered and redistributed to the surface large quantities of sulfur, one of the most important elements for life. The stochastic occurrence of large collisions could provide insights on why the Earth and Venus, considered Earth's twin planet, exhibit radically different atmospheres.

  3. Prebiotic materials from on and off the early Earth

    Science.gov (United States)

    Bernstein, Max

    2006-01-01

    One of the great puzzles of all time is how did life arise? It has been universally presumed that life arose in a soup rich in compounds made mostly of carbon, the kind of which we are currently composed. Where did these organic molecules come from? In this talk I will review proposed contributions to pre-biotic organic chemistry from both terrestrial processes (i.e., hydrothermal vents, Miller-Urey syntheses) and also from space. While the former is perhaps better known and more commonly taught in school, we now know that comet and asteroid dust deliver tons of organics to the Earth every day, and there is a growing consensus among scientists that molecules from space played an important role in making the Earth habitable, and perhaps even provided specific compounds that were directly related to the origin of life.

  4. Evolution of the protolunar disk: dynamics, cooling timescale and implantation of volatiles onto the Earth

    CERN Document Server

    Charnoz, Charnoz

    2015-01-01

    It is thought that the Moon accreted from the protolunar disk that was assembled after the last giant impact on Earth. Due to its high temperature, the protolunar disk may act as a thermochemical reactor in which the material is processed before being incorporated into the Moon. Outstanding issues like devolatilisation and istotopic evolution are tied to the disk evolution, however its lifetime, dynamics and thermodynamics are unknown. Here, we numerically explore the long term viscous evolution of the protolunar disk using a one dimensional model where the different phases (vapor and condensed) are vertically stratified. Viscous heating, radiative cooling, phase transitions and gravitational instability are accounted for whereas Moon s accretion is not considered for the moment. The viscosity of the gas, liquid and solid phases dictates the disk evolution. We find that (1) the vapor condenses into liquid in about 10 years, (2) a large fraction of the disk mass flows inward forming a hot and compact liquid di...

  5. Environmental Consequences of Big Nasty Impacts on the Early Earth

    Science.gov (United States)

    Zahnle, K. J.

    2015-12-01

    The geological record of the Archean Earth is spattered with impact spherules from a dozen or so major cosmic collisions involving Earth and asteroids or comets (Lowe, Byerly 1986, 2015). Extrapolation of the documented deposits suggests that most of these impacts were as big or bigger than the Chicxulub event that famously ended the reign of the thunder lizards. As the Archean impacts were greater, the environmental effects were also greater. The number and magnitude of the impacts is bounded by the lunar record. There are no lunar craters bigger than Chicxulub that date to Earth's mid-to-late Archean. Chance dictates that Earth experienced ~10 impacts bigger than Chicxulub between 2.5 Ga and 3.5 Ga, the biggest of which were ~30-100X more energetic than Chicxulub. To quantify the thermal consequences of big impacts on old Earth, we model the global flow of energy from the impact into the environment. The model presumes that a significant fraction of the impact energy goes into ejecta that interact with the atmosphere. Much of this energy is initially in rock vapor, melt, and high speed particles. (i) The upper atmosphere is heated by ejecta as they reenter the atmosphere. The mix of hot air, rock vapor, and hot silicates cools by thermal radiation. Rock raindrops fall out as the upper atmosphere cools. (ii) The energy balance of the lower atmosphere is set by radiative exchange with the upper atmosphere and with the surface, and by evaporation of seawater. Susequent cooling is governed by condensation of water vapor. (iii) The oceans are heated by thermal radiation and rock rain and cooled by evaporation. Surface waters become hot and salty; if a deep ocean remains it is relatively cool. Subsequently water vapor condenses to replenish the oceans with hot fresh water (how fresh depending on continental weathering, which might be rather rapid under the circumstances). (iv) The surface temperature of dry land is presumed to be the same as the lower atmosphere. A

  6. Environmental Consequences of Big Nasty Impacts on the Early Earth

    Science.gov (United States)

    Zahnle, Kevin

    2015-01-01

    The geological record of the Archean Earth is spattered with impact spherules from a dozen or so major cosmic collisions involving Earth and asteroids or comets (Lowe, Byerly 1986, 2015). Extrapolation of the documented deposits suggests that most of these impacts were as big or bigger than the Chicxulub event that famously ended the reign of the thunder lizards. As the Archean impacts were greater, the environmental effects were also greater. The number and magnitude of the impacts is bounded by the lunar record. There are no lunar craters bigger than Chicxulub that date to Earth's mid-to-late Archean. Chance dictates that Earth experienced no more than approximately 10 impacts bigger than Chicxulub between 2.5 billion years and 3.5 2.5 billion years, the biggest of which were approximately30-100 times more energetic, comparable to the Orientale impact on the Moon (1x10 (sup 26) joules). To quantify the thermal consequences of big impacts on old Earth, we model the global flow of energy from the impact into the environment. The model presumes that a significant fraction of the impact energy goes into ejecta that interact with the atmosphere. Much of this energy is initially in rock vapor, melt, and high speed particles. (i) The upper atmosphere is heated by ejecta as they reenter the atmosphere. The mix of hot air, rock vapor, and hot silicates cools by thermal radiation. Rock raindrops fall out as the upper atmosphere cools. (ii) The energy balance of the lower atmosphere is set by radiative exchange with the upper atmosphere and with the surface, and by evaporation of seawater. Susequent cooling is governed by condensation of water vapor. (iii) The oceans are heated by thermal radiation and rock rain and cooled by evaporation. Surface waters become hot and salty; if a deep ocean remains it is relatively cool. Subsequently water vapor condenses to replenish the oceans with hot fresh water (how fresh depending on continental weathering, which might be rather rapid

  7. Mixing in mantle convection models with self-consistent plate tectonics and melting and crustal production: Application to mixing in the early Earth

    Science.gov (United States)

    Tackley, Paul

    2016-04-01

    It is generally thought that the early Earth's mantle was hotter than today, which using conventional convective scalings should have led to vigorous convection and mixing. Geochemical observations, however, suggest that mixing was not as rapid as would be expected, leading to the suggestion that early Earth had stagnant lid convection (Debaille et al., EPSL 2013). Additionally, the mantle's thermal evolution is difficult to explain using conventional scalings because early heat loss would have been too rapid, which has led to the hypothesis that plate tectonics convection does not follow the conventional convective scalings (Korenaga, GRL 2003). One physical process that could be important in this context is partial melting leading to crustal production, which has been shown to have the major effects of buffering mantle temperature and carrying a significant fraction of the heat from hot mantle (Nakagawa and Tackley, EPSL 2012), making plate tectonics easier (Lourenco et al., submitted), and causing compositional differentiation of the mantle that can buffer core heat loss (Nakagawa and Tackley, GCubed 2010). Here, the influence of this process on mantle mixing is examined, using secular thermo-chemical models that simulate Earth's evolution over 4.5 billion years. Mixing is quantified both in terms of how rapidly stretching occurs, and in terms of dispersion: how rapidly initially close heterogeneities are dispersed horizontally and vertically through the mantle. These measures are quantified as a function of time through Earth's evolution. The results will then be related to geochemically-inferred mixing rates.

  8. Early Stage of Origin of Earth (interval after Emergence of Sun, Formation of Liquid Core, Formation of Solid Core)

    Science.gov (United States)

    Pechernikova, G. V.; Sergeev, V. N.

    2017-05-01

    Gravitational collapse of interstellar molecular cloud fragment has led to the formation of the Sun and its surrounding protoplanetary disk, consisting of 5 × 10^5 dust and gas. The collapse continued (1 years. Age of solar system (about 4.57×10^9 years) determine by age calcium-aluminum inclusions (CAI) which are present at samples of some meteorites (chondrites). Subsidence of dust to the central plane of a protoplanetary disk has led to formation of a dust subdisk which as a result of gravitational instability has broken up to condensations. In the process of collisional evolution they turned into dense planetesimals from which the planets formed. The accounting of a role of large bodies in evolution of a protoplanetary swarm in the field of terrestrial planets has allowed to define times of formation of the massive bodies permitting their early differentiation at the expense of short-lived isotopes heating and impacts to the melting temperature of the depths. The total time of Earth's growth is estimated about 10^8 years. Hf geochronometer showed that the core of the Earth has existed for Using W about 3×10^7 Hf geohronometer years since the formation of the CAI. Thus data W point to the formation of the Earth's core during its accretion. The paleomagnetic data indicate the existence of Earth's magnetic field past 3.5×10^9 years. But the age of the solid core, estimated by heat flow at the core-mantle boundary is 1.7×10^9 (0.5 years). Measurements of the thermal conductivity of liquid iron under the conditions that exist in the Earth's core, indicate the absence of the need for a solid core of existence to support the work geodynamo, although electrical resistivity measurements yield the opposite result.

  9. Biomolecule-Mineral Interactions in the Geochemical Environment on Early Earth and in the Human Body

    Science.gov (United States)

    Sahai, N.

    2011-12-01

    We worked on four projects consistent with the broad goals of the grant to investigate (i) the potential impacts of mineral surface chemistry and particle size on the stability and viability of cell membranes, bacteria and human cells and (ii) the influence of biomolecules on mineral nucleation and growth. The projects are of relevance to the origin and early evolution of life, biomineralization, medical mineralogy, and environmental biogeochemistry. The freedom enabled by the five-year grant to explore high-risk scientific areas, and the resulting high impact outcomes, cannot be overstated. We developed an almost entirely new field of Medical Mineralogyy and extended our concepts and knowledge-base to the potential roles of mineral surfaces in the evolution of protocells and the earliest cells. These exciting connections to medical mineralogy, and to the origin and evolution of life on early Earth are fascinating topics to the general public and even to other scientists, especially when the links to mineralogy and geochemistry are highlighted. In brief, we examined the stability of lipid bilayers representing model protocell membranes comprised of phospholipid bilayers with mineral surfaces. We found that the stability of lipid bilayers depends on mineral surface charge and increases as silica glass ~ quartz human either inadvertently as inhaled dusts or are inserted by design such as in components of orthopedic implants. It is important to know how the mineral surface properties affect the body's immune system response. We found that adhesion/detachment force of the Jurkat -line of T-lymphocytes increased as SiO2 glass ~ quartz < rutile (100) ~ mica (001) < polycrystalline corundum, and was related to the unraveling of cell surface glycoproteins, and to mineral surface charge. The studies described above have resulted in 23 peer-reviewed publications to date (published or in review or in prep.); one MSA volume and one Elements issue edited by the P.I.; trained

  10. A new model for early differentiation and chemical stratification of the Earth's mantle

    Science.gov (United States)

    Rubie, D. C.; Gessmann, C. K.; Frost, D. J.

    2003-04-01

    New experimental data on the solubility of oxygen in liquid Fe-rich alloy enable the geochemical consequences of core formation and the early geochemical evolution of the Earth's mantle to be better constrained. We have studied oxygen solubility in liquid Fe-alloy at 5-23 GPa, 2100--2700 K and variable oxygen fugacities using a multianvil apparatus. At constant oxygen fugacity, O solubility increases with increasing temperature but decreases with increasing pressure. Thus, along a high temperature adiabat (e.g. after formation of a deep magma ocean), oxygen solubility is high at relatively shallow depths (e.g. 3000 K) in a magma ocean result in significant Si being dissolved in liquid Fe-alloy whereas at depths >800--1000 km the solubility starts to decrease again and becomes close to zero at the CMB (Gessmann et al. 2001, EPSL 184, 367). Thus migration of liquid metal during core formation provides a mechanism for enriching the lower part of the mantle in the FeO component, and possibly also in SiO_2, relative to the upper part.

  11. On the Tidal Evolution of the Earth-Moon System: A Cosmological Model

    Directory of Open Access Journals (Sweden)

    Arbab A. I.

    2009-01-01

    Full Text Available We have presented a cosmological model for the tidal evolution of the Earth-Moon system. We have found that the expansion of the universe has immense consequences on our local systems. The model can be compared with the present observational data. The close approach problem inflicting the known tidal theory is averted in this model. We have also shown that the astronomical and geological changes of our local systems are of the order of Hubble constant.

  12. On the Tidal Evolution of the Earth-Moon System: A Cosmological Model

    Directory of Open Access Journals (Sweden)

    Arbab A. I.

    2009-01-01

    Full Text Available We have presented a cosmological model for the tidal evolution of the Earth-Moon system. We have found that the expansion of the universe has immense consequences on our local systems. The model can be compared with the present observational data. The close approach problem inflicting the known tidal theory is averted in this model. We have also shown that the astronomical and geological changes of our local systems are of the order of Hubble constant.

  13. Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth

    Science.gov (United States)

    Ćuk, Matija; Hamilton, Douglas P.; Lock, Simon J.; Stewart, Sarah T.

    2016-11-01

    In the giant-impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however, the current lunar orbital inclination of five degrees requires a subsequent dynamical process that is still unclear. In addition, the giant-impact theory has been challenged by the Moon’s unexpectedly Earth-like isotopic composition. Here we show that tidal dissipation due to lunar obliquity was an important effect during the Moon’s tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations. We present a tidal evolution model starting with the Moon in an equatorial orbit around an initially fast-spinning, high-obliquity Earth, which is a probable outcome of giant impacts. Using numerical modelling, we show that the solar perturbations on the Moon’s orbit naturally induce a large lunar inclination and remove angular momentum from the Earth-Moon system. Our tidal evolution model supports recent high-angular-momentum, giant-impact scenarios to explain the Moon’s isotopic composition and provides a new pathway to reach Earth’s climatically favourable low obliquity.

  14. Habitability of super-Earth planets around other suns: models including Red Giant Branch evolution.

    Science.gov (United States)

    von Bloh, W; Cuntz, M; Schröder, K-P; Bounama, C; Franck, S

    2009-01-01

    The unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses of up to several Earth masses and a similar chemical and mineralogical composition as Earth. We present a thermal evolution model for a 10 Earth-mass planet orbiting a star like the Sun. Our model is based on the integrated system approach, which describes the photosynthetic biomass production and takes into account a variety of climatological, biogeochemical, and geodynamical processes. This allows us to identify a so-called photosynthesis-sustaining habitable zone (pHZ), as determined by the limits of biological productivity on the planetary surface. Our model considers solar evolution during the main-sequence stage and along the Red Giant Branch as described by the most recent solar model. We obtain a large set of solutions consistent with the principal possibility of life. The highest likelihood of habitability is found for "water worlds." Only mass-rich water worlds are able to realize pHZ-type habitability beyond the stellar main sequence on the Red Giant Branch.

  15. Long-term preservation of early formed mantle heterogeneity by mobile lid convection: Importance of grainsize evolution

    Science.gov (United States)

    Foley, Bradford J.; Rizo, Hanika

    2017-10-01

    The style of tectonics on the Hadean and Archean Earth, particularly whether plate tectonics was in operation or not, is debated. One important, albeit indirect, constraint on early Earth tectonics comes from observations of early-formed geochemical heterogeneities: 142Nd and 182W anomalies recorded in Hadean to Phanerozoic rocks from different localities indicate that chemically heterogeneous reservoirs, formed during the first ∼500 Myrs of Earth's history, survived their remixing into the mantle for over 1 Gyrs. Such a long mixing time is difficult to explain because hotter mantle temperatures, expected for the early Earth, act to lower mantle viscosity and increase convective vigor. Previous studies found that mobile lid convection typically erases heterogeneity within ∼100 Myrs under such conditions, leading to the hypothesis that stagnant lid convection on the early Earth was responsible for the observed long mixing times. However, using two-dimensional Cartesian convection models that include grainsize evolution, we find that mobile lid convection can preserve heterogeneity at high mantle temperature conditions for much longer than previously thought, because higher mantle temperatures lead to larger grainsizes in the lithosphere. These larger grainsizes result in stronger plate boundaries that act to slow down surface and interior convective motions, in competition with the direct effect temperature has on mantle viscosity. Our models indicate that mobile lid convection can preserve heterogeneity for ≈0.4-1 Gyrs at early Earth mantle temperatures when the initial heterogeneity has the same viscosity as the background mantle, and ≈1-4 Gyrs when the heterogeneity is ten times more viscous than the background mantle. Thus, stagnant lid convection is not required to explain long-term survival of early formed geochemical heterogeneities, though these heterogeneities having an elevated viscosity compared to the surrounding mantle may be essential for their

  16. Schreibersite on the early Earth: Scenarios for prebiotic phosphorylation

    Directory of Open Access Journals (Sweden)

    Matthew A. Pasek

    2017-03-01

    Full Text Available The mineral schreibersite, (Fe,Ni3P, provides a reactive source of phosphorus capable of forming phosphorylated molecules. These molecules may have been an important component of prebiotic chemistry, allowing their build-up and eventual commencement of autopoiesis. Discussed here are potential geochemical routes to providing schreibersite, as a potentially important prebiotic mineral, to the Hadean Earth. Two routes are identified: delivery of phosphides by meteoritic material and the reduction of phosphates to phosphides by high-temperature, low-redox conditions. About 1–10% of all crustal phosphorus is estimated to have been in schreibersite during the Hadean, making the long-term reaction of this mineral with organic-laden water plausible for many years. Ultimately, such conditions would have been conducive to the formation of life as we know it today.

  17. The earth radiation budget experiment: Early validation results

    Science.gov (United States)

    Smith, G. Louis; Barkstrom, Bruce R.; Harrison, Edwin F.

    The Earth Radiation Budget Experiment (ERBE) consists of radiometers on a dedicated spacecraft in a 57° inclination orbit, which has a precessional period of 2 months, and on two NOAA operational meteorological spacecraft in near polar orbits. The radiometers include scanning narrow field-of-view (FOV) and nadir-looking wide and medium FOV radiometers covering the ranges 0.2 to 5 μm and 5 to 50 μm and a solar monitoring channel. This paper describes the validation procedures and preliminary results. Each of the radiometer channels underwent extensive ground calibration, and the instrument packages include in-flight calibration facilities which, to date, show negligible changes of the instruments in orbit, except for gradual degradation of the suprasil dome of the shortwave wide FOV (about 4% per year). Measurements of the solar constant by the solar monitors, wide FOV, and medium FOV radiometers of two spacecraft agree to a fraction of a percent. Intercomparisons of the wide and medium FOV radiometers with the scanning radiometers show agreement of 1 to 4%. The multiple ERBE satellites are acquiring the first global measurements of regional scale diurnal variations in the Earth's radiation budget. These diurnal variations are verified by comparison with high temporal resolution geostationary satellite data. Other principal investigators of the ERBE Science Team are: R. Cess, SUNY, Stoneybrook; J. Coakley, NCAR; C. Duncan, M. King and A Mecherikunnel, Goddard Space Flight Center, NASA; A. Gruber and A.J. Miller, NOAA; D. Hartmann, U. Washington; F.B. House, Drexel U.; F.O. Huck, Langley Research Center, NASA; G. Hunt, Imperial College, London U.; R. Kandel and A. Berroir, Laboratory of Dynamic Meteorology, Ecole Polytechique; V. Ramanathan, U. Chicago; E. Raschke, U. of Cologne; W.L. Smith, U. of Wisconsin and T.H. Vonder Haar, Colorado State U.

  18. A Geological Model for the Evolution of Early Continents (Invited)

    Science.gov (United States)

    Rey, P. F.; Coltice, N.; Flament, N. E.; Thébaud, N.

    2013-12-01

    Geochemical probing of ancient sediments (REE in black shales, strontium composition of carbonates, oxygen isotopes in zircons...) suggests that continents were a late Archean addition at Earth's surface. Yet, geochemical probing of ancient basalts reveals that they were extracted from a mantle depleted of its crustal elements early in the Archean. Considerations on surface geology, the early Earth hypsometry and the rheology and density structure of Archean continents can help solve this paradox. Surface geology: The surface geology of Archean cratons is characterized by thick continental flood basalts (CFBs, including greenstones) emplaced on felsic crusts dominated by Trondhjemite-Tonalite-Granodiorite (TTG) granitoids. This simple geology is peculiar because i/ most CFBs were emplaced below sea level, ii/ after their emplacement, CFBs were deformed into relatively narrow, curviplanar belts (greenstone basins) wrapping around migmatitic TTG domes, and iii/ Archean greenstone belts are richly endowed with gold and other metals deposits. Flat Earth hypothesis: From considerations on early Earth continental geotherm and density structure, Rey and Coltice (2008) propose that, because of the increased ability of the lithosphere to flow laterally, orogenic processes in the Archean produced only subdued topography (atmosphere and mantle systems, and did not contribute significantly to the sedimentary records. 2/ These continents evolved under the possibly episodic drive of plate tectonic processes, and certainly also under the drive of the density inversion imposed by the greenstone/TTG stratigraphy. Thébaud and Rey (2013) emphasized that sagduction was able to drive crustal-scale deformation in the interior of continents, away from plate margins. Since this process occurred on flooded continents, an infinite fluid reservoir was available to feed crustal-scale hydrothermal circulations promoting the formation of craton-wide metal deposits in the interior of continents

  19. Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

    Science.gov (United States)

    Hu, Wenqian; Shin, Yung C.; King, Galen B.

    2012-01-01

    Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11. Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps). Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators. PMID:22806170

  20. The Near Earth Object Surveillance Satellite: Mission status and CCD evolution after 18 months on-orbit

    Science.gov (United States)

    Wallace, B.; Scott, R.; Sale, M.

    2014-09-01

    The Near Earth Object Surveillance Satellite (NEOSSat) is a small telescope equipped microsatellite designed to perform both Space Situational Awareness (SSA) experiments and asteroid detection. NEOSSat was launched on 25 February 2013, however, due to time pressures, NEOSSat was launched with only the minimal software required to keep the spacecraft safe. The time pressure also resulted in the spacecraft undergoing reduced system and environmental testing on the ground. The full software suite, required to obtain imagery and maintain stable pointing, has since been uploaded to the spacecraft. NEOSSat has obtained imagery since June 2013, with the shutter both open and closed, but as of March 2014 has not achieved the fine pointing required to obtain scientifically useful data. The collected imagery is being used to characterize the on-board CCD camera. While gain and dark current values agree with pre-launch values, unexpected artefacts have appeared in the images. Methods for mitigating the artefacts through image processing have been developed, and spacecraft-level fixes are currently being investigated. In addition, damage from high energy particles impacting the CCD has produced hot pixels in imagery. We have been able to measure the evolution of these hot pixels over several months, both in terms of numbers and characteristics; these results will be presented. In addition, early results from the mission (image quality issues and evolution, early imagery examples), as well as the mission status (including fine pointing), will be discussed.

  1. Hydrogen, metals, bifurcating electrons, and proton gradients: the early evolution of biological energy conservation.

    Science.gov (United States)

    Martin, William F

    2012-03-09

    Life is a persistent, self-specified set of far from equilibrium chemical reactions. In modern microbes, core carbon and energy metabolism are what keep cells alive. In very early chemical evolution, the forerunners of carbon and energy metabolism were the processes of generating reduced carbon compounds from CO(2) and the mechanisms of harnessing energy as compounds capable of doing some chemical work. The process of serpentinization at alkaline hydrothermal vents holds promise as a model for the origin of early reducing power, because Fe(2+) in the Earth's crust reduces water to H(2) and inorganic carbon to methane. The overall geochemical process of serpentinization is similar to the biochemical process of methanogenesis, and methanogenesis is similar to acetogenesis in that both physiologies allow energy conservation from the reduction of CO(2) with electrons from H(2). Electron bifurcation is a newly recognized cytosolic process that anaerobes use generate low potential electrons, it plays an important role in some forms of methanogenesis and, via speculation, possibly in acetogenesis. Electron bifurcation likely figures into the early evolution of biological energy conservation.

  2. Modeling Continental Growth and Mantle Hydration in Earth's Evolution and the Impact of Life

    Science.gov (United States)

    Höning, Dennis; Spohn, Tilman

    2016-04-01

    The evolution of planets with plate tectonics is significantly affected by several intertwined feedback cycles. On Earth, interactions between atmosphere, hydrosphere, biosphere, crust, and interior determine its present day state. We here focus on the feedback cycles including the evolutions of mantle water budget and continental crust, and investigate possible effects of the Earth's biosphere. The first feedback loop includes cycling of water into the mantle at subduction zones and outgassing at volcanic chains and mid-ocean ridges. Water is known to reduce the viscosity of mantle rock, and therefore the speed of mantle convection and plate subduction will increase with the water concentration, eventually enhancing the rates of mantle water regassing and outgassing. A second feedback loop includes the production and erosion of continental crust. Continents are formed above subduction zones, whose total length is determined by the total size of the continents. Furthermore, the total surface area of continental crust determines the amount of eroded sediments per unit time. Subducted sediments affect processes in subduction zones, eventually enhancing the production rate of new continental crust. Both feedback loops affect each other: As a wet mantle increases the speed of subduction, continental production also speeds up. On the other hand, the total length of subduction zones and the rate at which sediments are subducted (both being functions of continental coverage) affect the rate of mantle water regassing. We here present a model that includes both cycles and show how the system develops stable and unstable fixed points in a plane defined by mantle water concentration and surface of continents. We couple these feedback cycles to a parameterized thermal evolution model that reproduces present day observations. We show how Earth has been affected by these feedback cycles during its evolution, and argue that Earth's present day state regarding its mantle water

  3. Isotope composition and volume of Earth´s early oceans

    DEFF Research Database (Denmark)

    Pope, Emily Catherine; Bird, Dennis K.; Rosing, Minik Thorleif

    2012-01-01

    Oxygen and hydrogen isotope compositions of Earth´s seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs......, but hydrogen´s was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as Î...... in Earth´s oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH4 and CO2 concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth....

  4. Excess hafnium-176 in meteorites and the early Earth zircon record

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Connelly, J.N.; Thrane, K.

    2012-01-01

    suggesting early extraction of a continental crust (>4.5 Gyr) but fail to identify a prevalent complementary depleted mantle reservoir, suggesting that crust formation processes in the early Earth were fundamentally distinct from today. However, this conclusion assumes that the Hf-isotope composition of bulk...... chondrite meteorites can be used to estimate the composition of Earth prior to its differentiation into major silicate reservoirs, namely the bulk silicate Earth (BSE). We report a Lu- Hf internal mineral isochron age of 4869 34 Myr for the pristine SAH99555 angrite meteorite. This age is ~300 Myr older...... than the age of the Solar System, confirming the existence of an energetic process yielding excess Hf in affected early formed Solar System objects through the production of the Lu isomer (t ~3.9 hours). Thus, chondrite meteorites contain excess Hf and their present-day composition cannot be used...

  5. Climatic consequences of very high carbon dioxide levels in the earth's early atmosphere

    Science.gov (United States)

    Kasting, James F.; Ackerman, Thomas P.

    1986-01-01

    The possible consequences of very high carbon dioxide concentrations in the earth's early atmosphere have been investigated with a radiative-convective climate model. The early atmosphere would apparently have been stable against the onset of a runaway greenhouse (that is, the complete evaporation of the oceans) for carbon dioxide pressures up to at least 100 bars. A 10- to 20-bar carbon dioxide atmosphere, such as may have existed during the first several hundred million years of the earth's history, would have had a surface temperature of approximately 85 to 110 C. The early stratosphere should have been dry, thereby precluding the possibility of an oxygenic prebiotic atmosphere caused by photodissociation of water vapor followed by escape of hydrogen to space. Earth's present atmosphere also appears to be stable against a carbon dioxide-induced runaway greenhouse.

  6. Climatic consequences of very high carbon dioxide levels in the earth's early atmosphere

    Science.gov (United States)

    Kasting, James F.; Ackerman, Thomas P.

    1986-01-01

    The possible consequences of very high carbon dioxide concentrations in the earth's early atmosphere have been investigated with a radiative-convective climate model. The early atmosphere would apparently have been stable against the onset of a runaway greenhouse (that is, the complete evaporation of the oceans) for carbon dioxide pressures up to at least 100 bars. A 10- to 20-bar carbon dioxide atmosphere, such as may have existed during the first several hundred million years of the earth's history, would have had a surface temperature of approximately 85 to 110 C. The early stratosphere should have been dry, thereby precluding the possibility of an oxygenic prebiotic atmosphere caused by photodissociation of water vapor followed by escape of hydrogen to space. Earth's present atmosphere also appears to be stable against a carbon dioxide-induced runaway greenhouse.

  7. Using Lunar Impact Glasses to Inform the Amount of Organic Material Delivered to the Early Earth

    Science.gov (United States)

    Nguyen, Pham; Zellner, Nicolle

    2017-01-01

    The delivery of organic material via comets and asteroids during the early history of Earth plays an important role in some theories about the origin of life on Earth. Given the close proximity of the Moon to the Earth, the Moon’s impact history can be used to estimate the amount of organic material delivered to the early Earth. Analysis of lunar impact glasses, derived from energetic impacts on the Moon, provide valuable data that can be used to interpret the Moon’s impact flux. Here we present the results of a study of the non-volatile lithophile element compositions of over 500 impact glass samples from the Apollo 14, 16, and 17 landing sites, along with associated ages of a subset of them. Our analyses show that many of the impact glasses possess compositions exotic to the local regolith in which they were found. Coupled with their ages, these glasses suggest material transport from distant regions of the Moon and may allow an estimate of the number of lunar (and terrestrial) impactors in a given time period. These results have important implications for constraining the Moon’s impact flux and also the amount of organic material delivered to the early Earth. Results of our preliminary study, which investigates the amounts of organic material delivered by comets and asteroids to the Moon (and Earth), will be presented.

  8. Earth's Early Biosphere and the Biogeochemical Carbon Cycle

    Science.gov (United States)

    DesMarais, David

    2004-01-01

    Our biosphere has altered the global environment principally by influencing the chemistry of those elements most important for life, e g., C, N, S, O, P and transition metals (e.g., Fe and Mn). The coupling of oxygenic photosynthesis with the burial in sediments of photosynthetic organic matter, and with the escape of H2 to space, has increased the state of oxidation of the Oceans and atmosphere. It has also created highly reduced conditions within sedimentary rocks that have also extensively affected the geochemistry of several elements. The decline of volcanism during Earth's history reduced the flow of reduced chemical species that reacted with photosynthetically produced O2. The long-term net accumulation of photosynthetic O2 via biogeochemical processes has profoundly influenced our atmosphere and biosphere, as evidenced by the O2 levels required for algae, multicellular life and certain modem aerobic bacteria to exist. When our biosphere developed photosynthesis, it tapped into an energy resource that was much larger than the energy available from oxidation-reduction reactions associated with weathering and hydrothermal activity. Today, hydrothermal sources deliver globally (0.13-1.1)x10(exp l2) mol yr(sup -1) of reduced S, Fe(2+), Mn(2+), H2 and CH4; this is estimated to sustain at most about (0.2-2)xl0(exp 12)mol C yr(sup -1) of organic carbon production by chemautotrophic microorganisms. In contrast, global photosynthetic productivity is estimated to be 9000x10(exp 12) mol C yr(sup -1). Thus, even though global thermal fluxes were greater in the distant geologic past than today, the onset of oxygenic photosynthesis probably increased global organic productivity by some two or more orders of magnitude. This enormous productivity materialized principally because oxygenic photosynthesizers unleashed a virtually unlimited supply of reduced H that forever freed life from its sole dependence upon abiotic sources of reducing power such as hydrothermal emanations

  9. Earth's Early Biosphere and the Biogeochemical Carbon Cycle

    Science.gov (United States)

    DesMarais, David

    2004-01-01

    Our biosphere has altered the global environment principally by influencing the chemistry of those elements most important for life, e g., C, N, S, O, P and transition metals (e.g., Fe and Mn). The coupling of oxygenic photosynthesis with the burial in sediments of photosynthetic organic matter, and with the escape of H2 to space, has increased the state of oxidation of the Oceans and atmosphere. It has also created highly reduced conditions within sedimentary rocks that have also extensively affected the geochemistry of several elements. The decline of volcanism during Earth's history reduced the flow of reduced chemical species that reacted with photosynthetically produced O2. The long-term net accumulation of photosynthetic O2 via biogeochemical processes has profoundly influenced our atmosphere and biosphere, as evidenced by the O2 levels required for algae, multicellular life and certain modem aerobic bacteria to exist. When our biosphere developed photosynthesis, it tapped into an energy resource that was much larger than the energy available from oxidation-reduction reactions associated with weathering and hydrothermal activity. Today, hydrothermal sources deliver globally (0.13-1.1)x10(exp l2) mol yr(sup -1) of reduced S, Fe(2+), Mn(2+), H2 and CH4; this is estimated to sustain at most about (0.2-2)xl0(exp 12)mol C yr(sup -1) of organic carbon production by chemautotrophic microorganisms. In contrast, global photosynthetic productivity is estimated to be 9000x10(exp 12) mol C yr(sup -1). Thus, even though global thermal fluxes were greater in the distant geologic past than today, the onset of oxygenic photosynthesis probably increased global organic productivity by some two or more orders of magnitude. This enormous productivity materialized principally because oxygenic photosynthesizers unleashed a virtually unlimited supply of reduced H that forever freed life from its sole dependence upon abiotic sources of reducing power such as hydrothermal emanations

  10. Hypermagnetic helicity evolution in early universe: leptogenesis and hypermagnetic diffusion

    OpenAIRE

    Semikoz, V. B.; Smirnov, A.Yu.(Max-Planck-Institute for Nuclear Physics, Saupfercheckweg 1, D-69117, Heidelberg, Germany); Sokoloff, D. D.

    2013-01-01

    We study hypermagnetic helicity and lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law $B/3 - L_{eR}=const$ at temperatures $T>T_{RL}\\simeq 10 TeV$ the fo...

  11. The evolution of oceanic 87Sr/86Sr does not rule out early continental growth

    Science.gov (United States)

    Flament, N.; Coltice, N.; Rey, P. F.

    2010-12-01

    Many contrasted continental growth models have been proposed to date, in which the amount of continental material extracted from the mantle at 3.8 Ga ranges between 0% (e.g. Taylor and McLennan, 1985) and 100% (e.g. Armstrong, 1981). One of the arguments in favor of delayed continental growth models is the shift in the 87Sr/86Sr of marine carbonates from mantle composition at ~ 2.8 Ga (Shields and Veizer, 2002). When using oceanic 87Sr/86Sr as a proxy of continental growth, the flux of strontium from the continents to the oceans is assumed to depend only on continental area and both continental hypsometry and continental freeboard are assumed to be constant through time. However, Rey and Coltice (2008) suggested that Archean reliefs were lower than present-day ones and Flament et al. (2008) suggested that the emerged land area is not proportional to continental growth. Therefore, the suitability of 87Sr/86Sr as a proxy of continental growth must be re-assessed. In this contribution, we develop an integrated model, from the mantle to the surface, to investigate the effect of contrasted continental growth models on the evolution of sea level, of the area of emerged land, and of oceanic 87Sr/86Sr. We estimate the evolution of mantle temperature using the model of Labrosse and Jaupart (2007) that takes the effect of continental growth into account. The maximum continental elevation is calculated using the results of Rey and Coltice (2008), sea level and the area of emerged land are calculated as in Flament et al. (2008), and the oceanic 87Sr/86Sr is calculated in a geochemical box model. We calculate Archean sea levels ~ 800 m higher than present for delayed continental growth and ~ 1500 m higher for early continental growth. In contrast, we calculate similar Archean areas of emerged land, of less than 5% of the Earth’s surface, for both early and delayed continental growth models. Because the area of emerged land does not depend on continental growth models, the

  12. THE INFLUENCE OF PRESSURE-DEPENDENT VISCOSITY ON THE THERMAL EVOLUTION OF SUPER-EARTHS

    Energy Technology Data Exchange (ETDEWEB)

    Stamenkovic, Vlada; Noack, Lena; Spohn, Tilman [Institute of Planetology, Westfaelische Wilhelms-Universitaet Muenster, Wilhelm-Klemm-Str. 10, 48149 Muenster (Germany); Breuer, Doris, E-mail: Vlada.Stamenkovic@dlr.de, E-mail: Lena.Noack@dlr.de, E-mail: Doris.Breuer@dlr.de, E-mail: Tilman.Spohn@dlr.de [Institute of Planetary Research, German Aerospace Center DLR, Rutherfordstrasse 2, 12489 Berlin (Germany)

    2012-03-20

    We study the thermal evolution of super-Earths with a one-dimensional (1D) parameterized convection model that has been adopted to account for a strong pressure dependence of the viscosity. A comparison with a 2D spherical convection model shows that the derived parameterization satisfactorily represents the main characteristics of the thermal evolution of massive rocky planets. We find that the pressure dependence of the viscosity strongly influences the thermal evolution of super-Earths-resulting in a highly sluggish convection regime in the lower mantles of those planets. Depending on the effective activation volume and for cooler initial conditions, we observe with growing planetary mass even the formation of a conductive lid above the core-mantle boundary (CMB), a so-called CMB-lid. For initially molten planets our results suggest no CMB-lids but instead a hot lower mantle and core as well as sluggish lower mantle convection. This implies that the initial interior temperatures, especially in the lower mantle, become crucial for the thermal evolution-the thermostat effect suggested to regulate the interior temperatures in terrestrial planets does not work for massive planets if the viscosity is strongly pressure dependent. The sluggish convection and the potential formation of the CMB-lid reduce the convective vigor throughout the mantle, thereby affecting convective stresses, lithospheric thicknesses, and heat fluxes. The pressure dependence of the viscosity may therefore also strongly affect the propensity of plate tectonics, volcanic activity, and the generation of a magnetic field of super-Earths.

  13. Plume tectonics and cratons formation in the early Earth

    Science.gov (United States)

    Gerya, T.; Stern, R. J.; Baes, M.; Fischer, R.; Sizova, E.; Sobolev, S. V.; Whattam, S. A.

    2015-12-01

    Modern geodynamics and continental growth are critically driven by subduction and plate tectonics, however how this tectonic regime started and what geodynamic regime was before remains controversial. Most present-day subduction initiation mechanisms require acting plate forces and/or pre-existing zones of lithospheric weakness, which are themselves the consequence of plate tectonics. Here, we focus on plume-lithosphere interactions and spontaneous plume-induced subduction initiation, which does not require pre-existing lithospheric fabric and is viable for both stagnant lid and mobile/deformable lid conditions. We present results of 2D and 3D numerical modeling of plume-induced deformation and associated crustal growth resulting from tectono-magmatic interaction of ascending mantle plumes with oceanic-type lithosphere. We demonstrate that weakening of the lithosphere by plume-induced magmatism is the key factor allowing for its internal deformation and differentiation resulting in continental crust growth. We also show that plume-lithosphere interaction can enable subduction and rudimentary plate tectonics initiation at the margins of a crustal plateau growing above the plume head. We argue that frequent plume-arc interactions recorded in Archean crust could reflect either short-term plume-induced subduction or plume-induced episodic lithospheric drips. We furthermore suggest a distinct plume-tectonics regime operated on Earth before plate tectonics, which was associated with widespread tectono-magmatic heat and mass exchange between the crust and the mantle. This regime was characterized by weak deformable plates with low topography, massive juvenile crust production from mantle derived melts, mantle-flows-driven crustal deformation, magma-assisted crustal convection and widespread development of lithospheric delamination and crustal drips. Plume tectonics also resulted in growth of hot depleted chemically buoyant subcrustal proto-cratonic mantle layer. Later

  14. A hot big bang theory: magnetic fields and the early evolution of the protolunar disk

    CERN Document Server

    Gammie, Charles F; Ricker, Paul M

    2016-01-01

    The leading theory for the formation of the Earth's moon invokes a collision between a Mars-sized body and the proto-Earth to produce a disk of orbiting material that later condenses to form the Moon. Here we study the early evolution of the protolunar disk. First, we show that the disk opacity is large and cooling is therefore inefficient (t_{cool} \\Omega >> 1). In this regime angular momentum transport in the disk leads to steady heating unless \\alpha < (t_{cool} \\Omega)^{-1} << 1. Following earlier work by Charnoz and Michaut, and Carballido et al., we show that once the disk is completely vaporized it is well coupled to the magnetic field. We consider a scenario in which turbulence driven by magnetic fields leads to a brief, hot phase where the disk is geometrically thick, wit h strong turbulent mixing. The disk cools by spreading until it decouples from the field. We point out that approximately half the accretion energy is dissipated in the boundary layer where the disk meets the Earth's surfac...

  15. Thermal Evolution of Terrestrial Planets: Earth, Mars, Size, Temperature, Tectonics, and Deep Volatile Cycling

    Science.gov (United States)

    Lenardic, A.; Hero, J.; McGovern, P. J., Jr.

    2014-12-01

    Recent efforts to constrain the thermal evolution of the Martian lithosphere suggest that the ratio of mantle heat production to heat loss, termed the Urey ratio, on Mars may be greater than unity at present (or in Mars' recent past). For comparison, the present day Earth value is 0.33. These estimates fly in the face of conventional wisdom that a smaller planet like Mars should have cooled faster than the Earth - and certainly should not be heating up at present. We perform a sensitivity analysis, using a thermal history modeling approach, to asses the relative effects of changing planetary size, mode of tectonics, and nature of deep volatile cycling (focussing on water). Our results indicate that differences in the nature of volatile cycling (degassing vs regassing over time) can outweigh the effects of size and tectonic mode in determining the thermal state of a planet. Mars models in which degassing dominates can give Urey ratios that exceed unity. Earth models in which regassing dominates over degassing in the later geologic stages of evolution lead to lower Urey ratio values.

  16. Early evolution of sexual dimorphism and polygyny in Pinnipedia.

    Science.gov (United States)

    Cullen, Thomas M; Fraser, Danielle; Rybczynski, Natalia; Schröder-Adams, Claudia

    2014-05-01

    Sexual selection is one of the earliest areas of interest in evolutionary biology. And yet, the evolutionary history of sexually dimorphic traits remains poorly characterized for most vertebrate lineages. Here, we report on evidence for the early evolution of dimorphism within a model mammal group, the pinnipeds. Pinnipeds show a range of sexual dimorphism and mating systems that span the extremes of modern mammals, from monomorphic taxa with isolated and dispersed mating to extreme size dimorphism with highly ordered polygynous harem systems. In addition, the degree of dimorphism in pinnipeds is closely tied to mating system, with strongly dimorphic taxa always exhibiting a polygynous system, and more monomorphic taxa possessing weakly polygynous systems. We perform a comparative morphological description, and provide evidence of extreme sexual dimorphism (similar to sea lions), in the Miocene-aged basal pinniped taxon Enaliarctos emlongi. Using a geometric morphometric approach and combining both modern and fossil taxa we show a close correlation between mating system and sex-related cranial dimorphism, and also reconstruct the ancestral mating system of extant pinnipeds as highly polygynous. The results suggest that sexual dimorphism and extreme polygyny in pinnipeds arose by 27 Ma, in association with changing climatic conditions. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  17. Hypermagnetic helicity evolution in early universe: leptogenesis and hypermagnetic diffusion

    CERN Document Server

    Semikoz, V B; Sokoloff, D D

    2013-01-01

    We study hypermagnetic helicity and lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law $B/3 - L_{eR}=const$ at temperatures $T>T_{RL}\\simeq 10 TeV$ the following universe cooling leads to the production of a non-zero left lepton (electrons and neutrinos) asymmetry. This is due to the Higgs decays becoming more faster when entering the equilibrium at $T=T_{RL}$ with the universe expansion, $\\Gamma_{RL}\\sim T> H\\sim T^2$, resulting in the parallel evolution of both the right and the left electron asymmetries at $Tevolution proceeds in a self...

  18. The Origin and Early Evolution of Membrane Proteins

    Science.gov (United States)

    Pohorille, Andrew; Schweighofer, Karl; Wilson, Michael A.

    2005-01-01

    Membrane proteins mediate functions that are essential to all cells. These functions include transport of ions, nutrients and waste products across cell walls, capture of energy and its transduction into the form usable in chemical reactions, transmission of environmental signals to the interior of the cell, cellular growth and cell volume regulation. In the absence of membrane proteins, ancestors of cell (protocells), would have had only very limited capabilities to communicate with their environment. Thus, it is not surprising that membrane proteins are quite common even in simplest prokaryotic cells. Considering that contemporary membrane channels are large and complex, both structurally and functionally, a question arises how their presumably much simpler ancestors could have emerged, perform functions and diversify in early protobiological evolution. Remarkably, despite their overall complexity, structural motifs in membrane proteins are quite simple, with a-helices being most common. This suggests that these proteins might have evolved from simple building blocks. To explain how these blocks could have organized into functional structures, we performed large-scale, accurate computer simulations of folding peptides at a water-membrane interface, their insertion into the membrane, self-assembly into higher-order structures and function. The results of these simulations, combined with analysis of structural and functional experimental data led to the first integrated view of the origin and early evolution of membrane proteins.

  19. What Do We Really Know About the Earth's Early Atmosphere?

    Science.gov (United States)

    Catling, D. C.; Krissansen-Totton, J.; Zahnle, K. J.

    2016-12-01

    ., Murakami T. (2015) Geochim. Cosmochim. Acta 159, 190. [5] Som S. M. et al. (2016) Nature Geosc. 9, 448. [6] Zahnle K. et al. (2006) Geobiology 4, 271. [7] Pope E. C. et al. (2012) P. Natl. Acad. Sci. USA 109, 4371. [8] Pujol M. et al. (2011) Earth Planet Sc Lett 308, 298. [9] Catling D. C. et al. (2001) Science 293, 839.

  20. Tidal heating of Earth-like exoplanets around M stars: Thermal, magnetic, and orbital evolutions

    CERN Document Server

    Driscoll, Peter

    2015-01-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low mass M stars whose radiative habitable zone overlaps with the "tidal zone". We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a visco-elastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within $0.07$ AU circularize before 10 G...

  1. The early Earth under a superflare and super-CME attack: prospects for life

    Science.gov (United States)

    Airapetian, Vladimir; Glocer, Alex; Gronoff, Guillaume

    Kepler observations suggest that G-type stars produce powerful flares suggesting that the early Earth may also have been exposed to frequent and energetic solar explosive events generated by the young Sun. We show that powerful coronal mass ejection (CME) events associated with superflares impacting the Earth magnetosphere with a frequency of 1 event/day. What was the impact of superflares, CMEs and associated solar energetic particle (SEPs) events on the atmospheric erosion of the young Earth and habitability? In this paper we discuss our three-dimensional (3D) magnetohydrodynamic (MHD) simulations that show that frequent and energetic CMEs from the early Sun continuously destroyed the sub-solar parts of Earth's magnetosphere at heights Photo-collisional dissociation of molecular nitrogen and carbon dioxide creates reactive chemistry that efficiently produces nitrous oxide and hydrogen cyanide, the essential molecule in prebiotic life chemistry. This raises an possibility that frequent super-CMEs could serve as a potential catalyst for the origin of life on early Earth.

  2. How Irreversible Heat Transport Processes Drive Earth's Interdependent Thermal, Structural, and Chemical Evolution Providing a Strongly Heterogeneous, Layered Mantle

    Science.gov (United States)

    Hofmeister, A.; Criss, R. E.

    2013-12-01

    Because magmatism conveys radioactive isotopes plus latent heat rapidly upwards while advecting heat, this process links and controls the thermal and chemical evolution of Earth. We present evidence that the lower mantle-upper mantle boundary is a profound chemical discontinuity, leading to observed heterogeneities in the outermost layers that can be directly sampled, and construct an alternative view of Earth's internal workings. Earth's beginning involved cooling via explosive outgassing of substantial ice (mainly CO) buried with dust during accretion. High carbon content is expected from Solar abundances and ice in comets. Reaction of CO with metal provided a carbide-rich core while converting MgSiO3 to olivine via oxidizing reactions. Because thermodynamic law (and buoyancy of hot particles) indicates that primordial heat from gravitational segregation is neither large nor carried downwards, whereas differentiation forced radioactive elements upwards, formation of the core and lower mantle greatly cooled the Earth. Reference conductive geotherms, calculated using accurate and new thermal diffusivity data, require that heat-producing elements are sequestered above 670 km which limits convection to the upper mantle. These irreversible beginnings limit secular cooling to radioactive wind-down, permiting deduction of Earth's inventory of heat-producing elements from today's heat flux. Coupling our estimate for heat producing elements with meteoritic data indicates that Earth's oxide content has been underestimated. Density sorting segregated a Si-rich, peridotitic upper mantle from a refractory, oxide lower mantle with high Ca, Al and Ti contents, consistent with diamond inclusion mineralogy. Early and rapid differentiation means that internal temperatures have long been buffered by freezing of the inner core, allowing survival of crust as old as ca.4 Ga. Magmatism remains important. Melt escaping though stress-induced fractures in the rigid lithosphere imparts a

  3. The role of Jupiter in driving Earth's orbital evolution: an update

    CERN Document Server

    Horner, J; Waltham, D

    2015-01-01

    In the coming decades, the discovery of the first truly Earth-like exoplanets is anticipated. The characterisation of those planets will play a vital role in determining which are chosen as targets for the search for life beyond the Solar system. One of the many variables that will be considered in that characterisation and selection process is the nature of the potential climatic variability of the exoEarths in question. In our own Solar system, the Earth's long-term climate is driven by several factors - including the modifying influence of life on our atmosphere, and the temporal evolution of Solar luminosity. The gravitational influence of the other planets in our Solar system add an extra complication - driving the Milankovitch cycles that are thought to have caused the on-going series of glacial and interglacial periods that have dominated Earth's climate for the past few million years. Here, we present the results of a large suite of dynamical simulations that investigate the influence of the giant pla...

  4. Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars

    CERN Document Server

    Möstl, Christian; Frahm, Rudy A; Liu, Ying D; Long, David M; Colaninno, Robin C; Reiss, Martin A; Temmer, Manuela; Farrugia, Charles J; Posner, Arik; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil; Mays, Mona L; Vrsnak, Bojan

    2015-01-01

    The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction + 37+/-10 degree (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts.

  5. Clades reach highest morphological disparity early in their evolution

    Science.gov (United States)

    Hughes, Martin; Gerber, Sylvain; Albion Wills, Matthew

    2013-08-01

    There are few putative macroevolutionary trends or rules that withstand scrutiny. Here, we test and verify the purported tendency for animal clades to reach their maximum morphological variety relatively early in their evolutionary histories (early high disparity). We present a meta-analysis of 98 metazoan clades radiating throughout the Phanerozoic. The disparity profiles of groups through time are summarized in terms of their center of gravity (CG), with values above and below 0.50 indicating top- and bottom-heaviness, respectively. Clades that terminate at one of the "big five" mass extinction events tend to have truncated trajectories, with a significantly top-heavy CG distribution overall. The remaining 63 clades show the opposite tendency, with a significantly bottom-heavy mean CG (relatively early high disparity). Resampling tests are used to identify groups with a CG significantly above or below 0.50; clades not terminating at a mass extinction are three times more likely to be significantly bottom-heavy than top-heavy. Overall, there is no clear temporal trend in disparity profile shapes from the Cambrian to the Recent, and early high disparity is the predominant pattern throughout the Phanerozoic. Our results do not allow us to distinguish between ecological and developmental explanations for this phenomenon. To the extent that ecology has a role, however, the paucity of bottom-heavy clades radiating in the immediate wake of mass extinctions suggests that early high disparity more probably results from the evolution of key apomorphies at the base of clades rather than from physical drivers or catastrophic ecospace clearing.

  6. Analyzing early exo-Earths with a coupled atmosphere biogeochemical model

    Science.gov (United States)

    Gebauer, Stefanie; Grenfell, John Lee; Stock, Joachim; Lehmann, Ralph; Godolt, Mareike; von Paris, Philip; Rauer, Heike

    2017-04-01

    Investigating Earth-like extrasolar planets with atmospheric models is a central focus in planetary science. Taking the development of Earth as a reference for Earth-like planets we investigate interactions between the atmosphere, planetary surface and organisms. The Great Oxidation Event (GOE) is related to feedbacks between these three. Its origin and controlling mechanisms are not well defined - requiring interdisciplinary, coupled models. We present results from our newly-developed Coupled Atmosphere Biogeochemistry (CAB) model which is unique in the literature. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles governing O2 in early Earth's atmosphere near the GOE. Complicated oxidation pathways play a key role in destroying O2 whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis.

  7. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions.

    Science.gov (United States)

    Driscoll, P E; Barnes, R

    2015-09-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the "tidal zone," where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life.

  8. Evolution of the Earth Observing System (EOS) Data and Information System (EOSDIS)

    Science.gov (United States)

    Ramapriyan, Hampapuram K.; Behnke, Jeanne; Sofinowski, Edwin; Lowe, Dawn; Esfandiari, Mary Ann

    2008-01-01

    One of the strategic goals of the U.S. National Aeronautics and Space Administration (NASA) is to "Develop a balanced overall program of science, exploration, and aeronautics consistent with the redirection of the human spaceflight program to focus on exploration". An important sub-goal of this goal is to "Study Earth from space to advance scientific understanding and meet societal needs." NASA meets this subgoal in partnership with other U.S. agencies and international organizations through its Earth science program. A major component of NASA s Earth science program is the Earth Observing System (EOS). The EOS program was started in 1990 with the primary purpose of modeling global climate change. This program consists of a set of space-borne instruments, science teams, and a data system. The instruments are designed to obtain highly accurate, frequent and global measurements of geophysical properties of land, oceans and atmosphere. The science teams are responsible for designing the instruments as well as scientific algorithms to derive information from the instrument measurements. The data system, called the EOS Data and Information System (EOSDIS), produces data products using those algorithms as well as archives and distributes such products. The first of the EOS instruments were launched in November 1997 on the Japanese satellite called the Tropical Rainfall Measuring Mission (TRMM) and the last, on the U.S. satellite Aura, were launched in July 2004. The instrument science teams have been active since the inception of the program in 1990 and have participation from Brazil, Canada, France, Japan, Netherlands, United Kingdom and U.S. The development of EOSDIS was initiated in 1990, and this data system has been serving the user community since 1994. The purpose of this chapter is to discuss the history and evolution of EOSDIS since its beginnings to the present and indicate how it continues to evolve into the future. this chapter is organized as follows. Sect

  9. Evolution of the Stability Work from Classic Retaining Walls to Mechanically Stabilized Earth Walls

    Directory of Open Access Journals (Sweden)

    Anghel Stanciu

    2008-01-01

    Full Text Available For the consolidation of soil mass and the construction of the stability works for roads infrastructure it was studied the evolution of these kinds of works from classical retaining walls - common concrete retaining walls, to the utilization in our days of the modern and competitive methods - mechanically stabilized earth walls. Like type of execution the variety of the reinforced soil is given by the utilization of different types of reinforcing inclusions (steel strips, geosynthetics, geogrids or facing (precast concrete panels, dry cast modular blocks, metal sheets and plates, gabions, and wrapped sheets of geosynthetics.

  10. Deep Phylogeny—How a Tree Can Help Characterize Early Life on Earth

    OpenAIRE

    Gaucher, Eric A.; Kratzer, James T.; Randall, Ryan N.

    2010-01-01

    The Darwinian concept of biological evolution assumes that life on Earth shares a common ancestor. The diversification of this common ancestor through speciation events and vertical transmission of genetic material implies that the classification of life can be illustrated in a tree-like manner, commonly referred to as the Tree of Life. This article describes features of the Tree of Life, such as how the tree has been both pruned and become bushier throughout the past century as our knowledge...

  11. Alternative Earths: The Diverse Chapters of Sustained Habitability on a Dynamic Early Earth and Their Astrobiological Significance

    Science.gov (United States)

    Lyons, T. W.

    2015-12-01

    The oldest signs of animal life appear in the geologic record 600 to 700 million years ago. For the four billion years prior, our planet experienced dramatic changes that paved the way for this milestone. Beyond the establishment of Earth's earliest oceans 4.3 billion years ago (Ga), the single most important environmental transformation in history may have been the first permanent rise of atmospheric oxygen around 2.3 Ga. Before this Great Oxidation Event (GOE), Earth's atmosphere and oceans were virtually devoid of this gas, which forms the basis for all macroscopic life. Yet full oxygenation was a long, drawn out process. This talk will lay out the state-of-the-art in our understanding of Earth's early oxygenation, with an emphasis on the delay between the first biological oxygen production, tentatively placed at 3 Ga, and the appearance of animals almost 2.5 billion years later. Recent work suggests transient oxygenation episodes occurred prior to the GOE. Once permanently present in the atmosphere, oxygen may have risen to very high levels and then nose-dived. Then, at least a billion years of dominantly oxygen-free conditions in the deep ocean followed, beneath an atmosphere and shallow oceans much leaner in oxygen than previous estimates indicated. Deficiencies in oxygen and associated nutrients may have, in turn, set a challenging course for many of the oceans' inhabitants, explaining persistently low populations and diversities of eukaryotes. The latest data suggest these billion-plus years of intermediate oxygen were followed by increases in both ocean and atmosphere oxygen contents and eukaryotic diversity 750 to 800 million years ago. Novel, rock-bound proxies and complementary numerical models are now steering our views of co-evolving life and marine and atmospheric chemistry, including greenhouse gas controls on climate. New findings are revealing various states of planetary habitability that differ greatly from the Earth we know today. These

  12. The Moon as a recorder of organic evolution in the early solar system: a lunar regolith analog study.

    Science.gov (United States)

    Matthewman, Richard; Court, Richard W; Crawford, Ian A; Jones, Adrian P; Joy, Katherine H; Sephton, Mark A

    2015-02-01

    The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter-containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable.

  13. The early evolution of Jean Piaget's clinical method.

    Science.gov (United States)

    Mayer, Susan Jean

    2005-11-01

    This article analyzes the early evolution of Jean Piaget's renowned "clinical method" in order to investigate the method's strikingly original and generative character. Throughout his 1st decade in the field, Piaget frequently discussed and justified the many different approaches to data collection he used. Analysis of his methodological progression during this period reveals that Piaget's determination to access the genuine convictions of children eventually led him to combine 3 distinct traditions in which he had been trained-naturalistic observation, psychometrics, and the psychiatric clinical examination. It was in this amalgam, first evident in his 4th text, that Piaget discovered the clinical dynamic that would drive the classic experiments for which he is most well known.

  14. Impact shocked rocks as protective habitats on an anoxic early Earth

    Science.gov (United States)

    Bryce, Casey C.; Horneck, Gerda; Rabbow, Elke; Edwards, Howell G. M.

    2015-01-01

    On Earth, microorganisms living under intense ultraviolet (UV) radiation stress can adopt endolithic lifestyles, growing within cracks and pore spaces in rocks. Intense UV irradiation encountered by microbes leads to death and significant damage to biomolecules, which also severely diminishes the likelihood of detecting signatures of life. Here we show that porous rocks shocked by asteroid or comet impacts provide protection for phototrophs and their biomolecules during 22 months of UV radiation exposure outside the International Space Station. The UV spectrum used approximated the high-UV flux on the surface of planets lacking ozone shields such as the early Earth. These data provide a demonstration that endolithic habitats can provide a refugium from the worst-case UV radiation environments on young planets and an empirical refutation of the idea that early intense UV radiation fluxes would have prevented phototrophs without the ability to form microbial mats or produce UV protective pigments from colonizing the surface of early landmasses.

  15. Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution.

    Science.gov (United States)

    Slack, Kerryn E; Jones, Craig M; Ando, Tatsuro; Harrison, G L Abby; Fordyce, R Ewan; Arnason, Ulfur; Penny, David

    2006-06-01

    Testing models of macroevolution, and especially the sufficiency of microevolutionary processes, requires good collaboration between molecular biologists and paleontologists. We report such a test for events around the Late Cretaceous by describing the earliest penguin fossils, analyzing complete mitochondrial genomes from an albatross, a petrel, and a loon, and describe the gradual decline of pterosaurs at the same time modern birds radiate. The penguin fossils comprise four naturally associated skeletons from the New Zealand Waipara Greensand, a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61-62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 +/- 3 Ma (Campanian). It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs, which also coexisted with early crown birds, show notable changes through the Late Cretaceous. There was a decrease in taxonomic diversity, and small- to medium-sized species disappeared well before the end of the Cretaceous. A simple reading of the fossil record might suggest competitive interactions with birds, but much more needs to be understood about pterosaur life histories. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain

  16. Probing early-type galaxy evolution with the Kormendy relation

    CERN Document Server

    Ziegler, B L; Bender, R; Belloni, P; Greggio, L; Seitz, S

    1999-01-01

    We investigate the evolution of early-type galaxies in four clusters at z=0.4 (Abell370, Cl0303+17, Cl0939+47 and Cl1447+26) and in one at z=0.55 (Cl0016+16). The galaxies are selected according to their spectrophotometrically determined spectral types and comprise the morphological classes E, S0 and Sa galaxies. Structural parameters are determined by a two-component fitting of the surface brightness profiles derived from HST images. Exploring a realistic range of K-corrections using Bruzual and Charlot models, we construct the rest-frame B-band Kormendy relations (mu_e-log(R_e)) for the different clusters. We do not detect a systematic change of the slope of the relation as a function of redshift. We discuss in detail how the luminosity evolution, derived by comparing the Kormendy relations of the distant clusters with the local one for Coma, depends on various assumptions and give a full description of random and systematic errors by exploring the influences of selection bias, different star formation hist...

  17. Origins and Early Evolution of the tRNA Molecule

    Directory of Open Access Journals (Sweden)

    Koji Tamura

    2015-12-01

    Full Text Available Modern transfer RNAs (tRNAs are composed of ~76 nucleotides and play an important role as “adaptor” molecules that mediate the translation of information from messenger RNAs (mRNAs. Many studies suggest that the contemporary full-length tRNA was formed by the ligation of half-sized hairpin-like RNAs. A minihelix (a coaxial stack of the acceptor stem on the T-stem of tRNA can function both in aminoacylation by aminoacyl tRNA synthetases and in peptide bond formation on the ribosome, indicating that it may be a vestige of the ancestral tRNA. The universal CCA-3′ terminus of tRNA is also a typical characteristic of the molecule. “Why CCA?” is the fundamental unanswered question, but several findings give a comprehensive picture of its origin. Here, the origins and early evolution of tRNA are discussed in terms of various perspectives, including nucleotide ligation, chiral selectivity of amino acids, genetic code evolution, and the organization of the ribosomal peptidyl transferase center (PTC. The proto-tRNA molecules may have evolved not only as adaptors but also as contributors to the composition of the ribosome.

  18. Transposable elements and early evolution of sex chromosomes in fish.

    Science.gov (United States)

    Chalopin, Domitille; Volff, Jean-Nicolas; Galiana, Delphine; Anderson, Jennifer L; Schartl, Manfred

    2015-09-01

    In many organisms, the sex chromosome pair can be recognized due to heteromorphy; the Y and W chromosomes have often lost many genes due to the absence of recombination during meiosis and are frequently heterochromatic. Repetitive sequences are found at a high proportion on such heterochromatic sex chromosomes and the evolution and emergence of sex chromosomes has been connected to the dynamics of repeats and transposable elements. With an amazing plasticity of sex determination mechanisms and numerous instances of independent emergence of novel sex chromosomes, fish represent an excellent lineage to investigate the early stages of sex chromosome differentiation, where sex chromosomes often are homomorphic and not heterochromatic. We have analyzed the composition, distribution, and relative age of TEs from available sex chromosome sequences of seven teleost fish. We observed recent bursts of TEs and simple repeat accumulations around young sex determination loci. More strikingly, we detected transposable element (TE) amplifications not only on the sex determination regions of the Y and W sex chromosomes, but also on the corresponding regions of the X and Z chromosomes. In one species, we also clearly demonstrated that the observed TE-rich sex determination locus originated from a TE-poor genomic region, strengthening the link between TE accumulation and emergence of the sex determination locus. Altogether, our results highlight the role of TEs in the initial steps of differentiation and evolution of sex chromosomes.

  19. Peptide synthesis triggered by comet impacts: A possible method for peptide delivery to the early Earth and icy satellites

    Science.gov (United States)

    Sugahara, Haruna; Mimura, Koichi

    2015-09-01

    We performed shock experiments simulating natural comet impacts in an attempt to examine the role that comet impacts play in peptide synthesis. In the present study, we selected a mixture of alanine (DL-alanine), water ice, and silicate (forsterite) to make a starting material for the experiments. The shock experiments were conducted under cryogenic conditions (77 K), and the shock pressure range achieved in the experiments was 4.8-25.8 GPa. The results show that alanine is oligomerized into peptides up to tripeptides due to the impact shock. The synthesized peptides were racemic, indicating that there was no enantioselective synthesis of peptides from racemic amino acids due to the impact shock. We also found that the yield of linear peptides was a magnitude higher than those of cyclic diketopiperazine. Furthermore, we estimated the amount of cometary-derived peptides to the early Earth based on two models (the Lunar Crating model and the Nice model) during the Late Heavy Bombardment (LHB) using our experimental data. The estimation based on the Lunar Crating model gave 3 × 109 mol of dialanine, 4 × 107 mol of trialanine, and 3 × 108 mol of alanine-diketopiperazine. Those based on the Nice model, in which the main impactor of LHB is comets, gave 6 × 1010 mol of dialanine, 1 × 109 mol of trialanine, and 8 × 109 mol of alanine-diketopiperazine. The estimated amounts were comparable to those originating from terrestrial sources (Cleaves, H.J., Aubrey, A.D., Bada, J.L. [2009]. Orig. Life Evol. Biosph. 39, 109-126). Our results indicate that comet impacts played an important role in chemical evolution as a supplier of linear peptides, which are important for further chemical evolution on the early Earth. Our study also highlights the importance of icy satellites, which were formed by comet accumulation, as prime targets for missions searching for extraterrestrial life.

  20. Studies of Physcomitrella patens reveal that ethylene-mediated submergence responses arose relatively early in land-plant evolution

    KAUST Repository

    Yasumura, Yuki

    2012-10-18

    Colonization of the land by multicellular green plants was a fundamental step in the evolution of life on earth. Land plants evolved from fresh-water aquatic algae, and the transition to a terrestrial environment required the acquisition of developmental plasticity appropriate to the conditions of water availability, ranging from drought to flood. Here we show that extant bryophytes exhibit submergence-induced developmental plasticity, suggesting that submergence responses evolved relatively early in the evolution of land plants. We also show that a major component of the bryophyte submergence response is controlled by the phytohormone ethylene, using a perception mechanism that has subsequently been conserved throughout the evolution of land plants. Thus a plant environmental response mechanism with major ecological and agricultural importance probably had its origins in the very earliest stages of the colonization of the land. © 2012 Blackwell Publishing Ltd.

  1. [Transparent evolution of the energy/matter interactions on earth: from gas whirlwind to technogenic civilization].

    Science.gov (United States)

    Pechurkin, N S; Shuvaev, A N

    2015-01-01

    The paper presents the idea of transparent evolution through the long-term reaction of the planet Earth on the external flow of radiant energy from the Sun. Due to limitations of matter on Earth, as well as on any other planet, the continuous pumping flow of radiant energy was shown to lead to cyclization and transport of substance on emerging gradients. The evolution of energy-matter interaction follows the path of capturing and transferring more energy by the fewer matter, i.e., the path of growth of the amount of energy used by each unit mass. For this indicator, the least effective mass transfer is a simple mass transfer as vortices of gases, in the gradients of temperature and pressure, which occurred on the primary surface of the planet. A long-term natural selection related to the accumulation of water on the planet has played a special role in developing the interaction of energy and matter. Phase transformations (ice, water, vapor) and mechanical transfers are the most common energy-matter processes. Based on water cycles, cyclic transports and transformations, chemical transformation of substances became possible developing over time into a biological transformation. This kind of the interaction of energy and matter is most efficient. In particular, during photosynthesis the energy of our star "is captured and utilized" in the most active part of the spectrum of its radiation. In the process of biological evolution of heterotrophs, a rise (by a factor of hundreds) in the coefficient that characterizes the intensity of energy exchange from protozoa to mammals is most illustratory. The development and the current dominance of humans as the most energy-using active species in capturing the energy and meaningful organization of its new flows especially on the basis of organic debris of former biospheres is admirable, but quite natural from the energy positions. In the course of technological evolution of humankind, the measure of the intensity of energy for

  2. Geodynamic evolution of the Earth over 600 Ma: implications for palaeo-climatic indicators

    Science.gov (United States)

    Hochard, C.; Vérard, C.

    2011-12-01

    During the last decades numerous local reconstructions were developed by the Geodynamic School of Lausanne. They participated to the elaboration of a 600Ma to present global plate tectonics model* based on field geology and controlled by geometric and kinematic constraints. Plate tectonics principles and lithospheric behaviour were applied to the model that drastically differs from the continental drift approach (i.e. based on palaeomagnetic data). Step after step lithospheric plates were reconstructed by adding or removing oceanic material (symbolized by synthetic isochrones) to major continents. The geodynamic evolution obtained is thus physically coherent and covers the whole surface of the Earth for the Phanerozoic. In the present contribution, we detail the basic tectonic features making up the model and the way they can be tested against the main palaeoclimatic indicators. Using synthetic isochrones, we developed a series of ocean lithosphere age maps. Based on plate rotation poles we computed velocity maps showing accretion and convergence rates. Converting ages into lithosphere thicknesses we quantified the volume of subducting material. Such tectonic parameters can be compared with the evolution of chemical proxies (e.g. CO2, δ18O, 87Sr/86Sr, Mg/Ca, SO4) offering a different way to decipher long-term climate changes. * This work was carried out as part of work done within the research program of the University of Lausanne on the Stampfli geodynamic model, model which is now owned by Neftex Petroleum Consultants Ltd. and is now attached to the "Neftex Earth Model ".

  3. Thoughts on the diversity of convergent evolution of bioluminescence on earth

    Science.gov (United States)

    Waldenmaier, Hans E.; Oliveira, Anderson G.; Stevani, Cassius V.

    2012-10-01

    The widespread independent evolution of analogous bioluminescent systems is one of the most impressive and diverse examples of convergent evolution on earth. There are roughly 30 extant bioluminescent systems that have evolved independently on Earth, with each system likely having unique enzymes responsible for catalysing the bioluminescent reaction. Bioluminescence is a chemical reaction involving a luciferin molecule and a luciferase or photoprotein that results in the emission of light. Some independent systems utilize the same luciferin, such as the use of tetrapyrrolic compounds by krill and dinoflagellates, and the wide use of coelenterazine by marine organisms, while the enzymes involved are unique. One common thread among all the different bioluminescent systems is the requirement of molecular oxygen. Bioluminescence is found in most forms of life, especially marine organisms. Bioluminescence in known to benefit the organism by: attraction, repulsion, communication, camouflage, and illumination. The marine ecosystem is significantly affected by bioluminescence, the only light found in the pelagic zone and below is from bioluminescent organisms. Transgenic bioluminescent organisms have revolutionized molecular research, medicine and the biotechnology industry. The use of bioluminescence in studying molecular pathways and disease allows for non-invasive and real-time analysis. Bioluminescence-based assays have been developed for several analytes by coupling luminescence to many enzyme-catalysed reactions.

  4. Long term evolution of distant retrograde orbits in the Earth-Moon system

    Science.gov (United States)

    Bezrouk, Collin; Parker, Jeffrey S.

    2017-09-01

    This work studies the evolution of several Distant Retrograde Orbits (DROs) of varying size in the Earth-Moon system over durations up to tens of millennia. This analysis is relevant for missions requiring a completely hands off, long duration quarantine orbit, such as a Mars Sample Return mission or the Asteroid Redirect Mission. Four DROs are selected from four stable size regions and are propagated for up to 30,000 years with an integrator that uses extended precision arithmetic techniques and a high fidelity dynamical model. The evolution of the orbit's size, shape, orientation, period, out-of-plane amplitude, and Jacobi constant are tracked. It has been found that small DROs, with minor axis amplitudes of approximately 45,000 km or less decay in size and period largely due to the Moon's solid tides. Larger DROs (62,000 km and up) are more influenced by the gravity of bodies external to the Earth-Moon system, and remain bound to the Moon for significantly less time.

  5. Ediacaran paleomagnetic field records from Laurentia: Insights into the evolution of the diversity of life and Earth's deep interior

    Science.gov (United States)

    Bono, R. K.; Tarduno, J. A.

    2015-12-01

    The Ediacaran to early Cambrian interval (~635-530 Ma) marks a tremendous increase in biotic diversity known as the Cambrian explosion. The magnitude of the biotic evolution has motivated hypotheses evoking a role for abiotic/environmental causal factors. For example, a rotation of the entire solid Earth by 90°, in what has been called an inertial interchange true polar wander (IITPW) event, has been linked to these events. One of the primary data sets motivating IITPW has been the report of nearly orthogonal directions from the Sept-Îles (ca. 565 Ma) intrusion (Quebec, Canada) on the basis of whole rock paleomagnetic analyses. We have found that only one direction (shallow) from our sampling of the Sept-Îles intrusion is carried by single domain magnetic grains and thus can be considered primary (Bono and Tarduno, Geology, 2015). Moreover, we find that the geomagnetic field was reversing during cooling of the intrusion; the small spatial scales on which we see antipodal directions suggest a very rapid reversal rate. Preliminary total-TRM paleointensity results from the Sept-Îles intrusion suggest a low field strength. The high geomagnetic reversal rate and low geomagnetic field intensity that characterize a portion of the Jurassic (ca. 165 Ma) may be an analog for field behavior during the Ediacaran to early Cambrian. This model may provide insight into the development of Earth's interior; if high thermal core conductivity values are correct, the onset of inner core growth is predicted to have an age similar to that of our directional and paleointensity data. To test these linkages, we investigate dated localities of the Grenville dikes (ca. 590 Ma) from which classic paleomagnetic results on whole rocks (Murthy, 1971) have long figured into debates over the paleolatitude history of Laurentia. New rock- and paleo-magnetic experiments testing single crystal feldspars from Laurentian Ediacaran intrusive units will be discussed, along with new estimates of

  6. Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth.

    Science.gov (United States)

    Cockell, Charles S; Rettberg, Petra; Rabbow, Elke; Olsson-Francis, Karen

    2011-10-01

    An epilithic microbial community was launched into low Earth orbit, and exposed to conditions in outer space for 548 days on the European Space Agency EXPOSE-E facility outside the International Space Station. The natural phototroph biofilm was augmented with akinetes of Anabaena cylindrica and vegetative cells of Nostoc commune and Chroococcidiopsis. In space-exposed dark controls, two algae (Chlorella and Rosenvingiella spp.), a cyanobacterium (Gloeocapsa sp.) and two bacteria associated with the natural community survived. Of the augmented organisms, cells of A. cylindrica and Chroococcidiopsis survived, but no cells of N. commune. Only cells of Chroococcidiopsis were cultured from samples exposed to the unattenuated extraterrestrial ultraviolet (UV) spectrum (>110 nm or 200 nm). Raman spectroscopy and bright-field microscopy showed that under these conditions the surface cells were bleached and their carotenoids were destroyed, although cell morphology was preserved. These experiments demonstrate that outer space can act as a selection pressure on the composition of microbial communities. The results obtained from samples exposed to >200 nm UV (simulating the putative worst-case UV exposure on the early Earth) demonstrate the potential for epilithic colonization of land masses during that time, but that UV radiation on anoxic planets can act as a strong selection pressure on surface-dwelling organisms. Finally, these experiments have yielded new phototrophic organisms of potential use in biomass and oxygen production in space exploration.

  7. East African climate pulses and early human evolution

    Science.gov (United States)

    Maslin, Mark A.; Brierley, Chris M.; Milner, Alice M.; Shultz, Susanne; Trauth, Martin H.; Wilson, Katy E.

    2014-10-01

    Current evidence suggests that all of the major events in hominin evolution have occurred in East Africa. Over the last two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of East Africa has varied in the past. The landscape of East Africa has altered dramatically over the last 10 million years. It has changed from a relatively flat, homogenous region covered with mixed tropical forest, to a varied and heterogeneous environment, with mountains over 4 km high and vegetation ranging from desert to cloud forest. The progressive rifting of East Africa has also generated numerous lake basins, which are highly sensitive to changes in the local precipitation-evaporation regime. There is now evidence that the presence of precession-driven, ephemeral deep-water lakes in East Africa were concurrent with major events in hominin evolution. It seems the unusual geology and climate of East Africa created periods of highly variable local climate, which, it has been suggested could have driven hominin speciation, encephalisation and dispersal out of Africa. One example is the significant hominin speciation and brain expansion event at ˜1.8 Ma that seems to have been coeval with the occurrence of highly variable, extensive, deep-water lakes. This complex, climatically very variable setting inspired first the variability selection hypothesis, which was then the basis for the pulsed climate variability hypothesis. The newer of the two suggests that the long-term drying trend in East Africa was punctuated by episodes of short, alternating periods of extreme humidity and aridity. Both hypotheses, together with other key theories of climate-evolution linkages, are discussed in this paper. Though useful the actual evolution mechanisms, which led to early hominins are still unclear and continue to be debated. However, it is clear that an understanding of East African

  8. Unexpected multiplicity of QRFP receptors in early vertebrate evolution.

    Science.gov (United States)

    Larhammar, Dan; Xu, Bo; Bergqvist, Christina A

    2014-01-01

    The neuropeptide QRFP, also called 26RFa, and its G protein-coupled receptor GPR103 have been identified in all vertebrates investigated. In mammals, this peptide-receptor pair has been found to have several effects including stimulation of appetite. Recently, we reported that a QRFP peptide is present in amphioxus, Branchiostoma floridae, and we also identified a QRFP receptor (QRFPR) that mediates a functional response to sub-nanomolar concentrations of the amphioxus peptide as well as short and long human QRFP (Xu et al., submitted). Because the ancestral vertebrate underwent two tetraploidizations, it might be expected that duplicates of the QRFP gene and its receptor gene may exist. Indeed, we report here the identification of multiple vertebrate QRFPR genes. Three QRFPR genes are present in the coelacanth Latimeria chalumnae, representing an early diverging sarcopterygian lineage. Three QRFPR genes are present in the basal actinopterygian fish, the spotted gar. Phylogenetic and chromosomal analyses show that only two of these receptor genes are orthologous between the two species, thus demonstrating a total of four distinct vertebrate genes. Three of the QRFPR genes resulted from the early vertebrate tetraploidizations and were copied along with syntenic neuropeptide Y receptor genes. The fourth QRFPR gene may be an even older and distinct lineage. Because mammals and birds have only a single QRFPR gene, this means that three genes have been lost in these lineages, and at least one of these was lost independently in mammals and birds because it is still present in a turtle. In conclusion, these results show that the QRFP system gained considerable complexity in the early stages of vertebrate evolution and still maintains much of this in some lineages, and that it has been secondarily reduced in mammals.

  9. Unexpected multiplicity of QRFP receptors in early vertebrate evolution

    Directory of Open Access Journals (Sweden)

    Dan eLarhammar

    2014-10-01

    Full Text Available The neuropeptide QRFP, also called 26RFa, and its G protein-coupled receptor GPR103 have been identified in all vertebrates investigated. In mammals, this peptide-receptor pair has been found to have several effects including stimulation of appetite. Recently, we reported that a QRFP peptide is present in amphioxus, Branchiostoma floridae, and we also identified a QRFP receptor (QRFPR that mediates a functional response to sub-nanomolar concentrations of the amphioxus peptide as well as short and long human QRFP (Xu et al., submitted. Because the ancestral vertebrate underwent two tetraploidizations, it might be expected that duplicates of the QRFP gene and its receptor gene may exist. Indeed, we report here the identification of multiple vertebrate QRFPR genes. Three QRFPR genes are present in the coelacanth Latimeria chalumnae, representing an early diverging sarcopterygian lineage. Three QRFP receptor genes are present in the basal actinopterygian fish, the spotted gar. Phylogenetic and chromosomal analyses show that only two of these receptor genes are orthologous between the two species, thus demonstrating a total of four distinct vertebrate genes. Three of the QRFPR genes resulted from the early vertebrate tetraploidizations and were copied along with syntenic neuropeptide Y receptor genes. The fourth QRFPR gene may be an even older and distinct lineage. Because mammals and birds have only a single QRFP receptor gene, this means that three genes have been lost in these lineages, and at least one of these was lost independently in mammals and birds because it is still present in a turtle. In conclusion, these results show that the QRFP system gained considerable complexity in the early stages of vertebrate evolution and still does so in some lineages, and that it has been secondarily reduced in mammals.

  10. Chloroplast genome evolution in early diverged leptosporangiate ferns.

    Science.gov (United States)

    Kim, Hyoung Tae; Chung, Myong Gi; Kim, Ki-Joong

    2014-05-01

    In this study, the chloroplast (cp) genome sequences from three early diverged leptosporangiate ferns were completed and analyzed in order to understand the evolution of the genome of the fern lineages. The complete cp genome sequence of Osmunda cinnamomea (Osmundales) was 142,812 base pairs (bp). The cp genome structure was similar to that of eusporangiate ferns. The gene/intron losses that frequently occurred in the cp genome of leptosporangiate ferns were not found in the cp genome of O. cinnamomea. In addition, putative RNA editing sites in the cp genome were rare in O. cinnamomea, even though the sites were frequently predicted to be present in leptosporangiate ferns. The complete cp genome sequence of Diplopterygium glaucum (Gleicheniales) was 151,007 bp and has a 9.7 kb inversion between the trnL-CAA and trnVGCA genes when compared to O. cinnamomea. Several repeated sequences were detected around the inversion break points. The complete cp genome sequence of Lygodium japonicum (Schizaeales) was 157,142 bp and a deletion of the rpoC1 intron was detected. This intron loss was shared by all of the studied species of the genus Lygodium. The GC contents and the effective numbers of codons (ENCs) in ferns varied significantly when compared to seed plants. The ENC values of the early diverged leptosporangiate ferns showed intermediate levels between eusporangiate and core leptosporangiate ferns. However, our phylogenetic tree based on all of the cp gene sequences clearly indicated that the cp genome similarity between O. cinnamomea (Osmundales) and eusporangiate ferns are symplesiomorphies, rather than synapomorphies. Therefore, our data is in agreement with the view that Osmundales is a distinct early diverged lineage in the leptosporangiate ferns.

  11. Coupled thermo-orbital evolution of tidally-evolved Earth-like planets

    Science.gov (United States)

    Behounkova, Marie; Walterova, Michaela; Cadek, Ondrej; Tobie, Gabriel; Choblet, Gael

    2016-10-01

    Progress in detection techniques of exoplanets inspired increasing number of studies focused on their internal dynamics and evolution. The detection methods tend to favor the discovery of short-period exoplanets, that are predicted to get rapidly tidally locked. During the locking process planets despin and a significant amount of tidal heating may contribute to the thermal budget of the planet. Moreover, tidally locked exoplanets exhibit large surface temperature contrasts between sub-stellar and anti-stellar sides due to uneven insolation which influence the convection pattern and cooling of the planet. Here, we will present the evolution of tidally locked Earth-like exoplanets using numerical tool Antigone (Behounkova et al., 2010, 2011) coupling long-term internal evolution, tidal dissipation (taking into account Maxwell or Andrade rheology) and uneven insolation pattern. For constant orbital parameters, we will focus on numerical simulation of the heat transfer in exoEarths for various rheological properties of planet and various values of spin-orbit resonance, semi-major axis, eccentricity and luminosity of star. In the case of effective heat transfer, our results suggest that the melting is mainly observed within the upper part of the mantle for tidal heating lower than 100TW . For tidal heating higher than 100TW, the melt is produced also within the deep part of the mantle and degree-2 convection is enhanced due to tidal heating pattern. For large tidal heating (larger than 1000TW), global melting is observed and temperature field is homogenized due to global melting, the heat transfer is mainly due to melt extraction and advection is suppressed. We will further present first results of coupled orbital-internal evolution of planets without companion using numerical model of orbital evolution with realistic (Maxwell or Andrade) rheology (Walterova et al., in prep). We will concentrate on the capture into the spin-orbit resonance. Special attention will be

  12. A study by computer simulation of the generation and evolution of the Earth`s magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Glatzmaier, G.A.; Hollerbach, R.; Roberts, P.H.

    1995-12-31

    Until recently very little has been known about the maintenance of the Earth`s magnetic field. The general consensus was that some type of convective motion edits in the Earth`s liquid iron alloy core that is affected by rotational forces in a way that continually generates new magnetic field to replace that which diffuses away. Magnetic-field reversals and secular variation have long been measured but no theory existed to explain these phenomena. To gain an understanding of the basic physical mechanisms of the ``geodynamo,`` we produced the first self-consistent computer simulation of convection and magnetic field generation in a rotating three-dimensional spherical fluid shell as an anologue to the Earth`s convective dynamo. This is a final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  13. Towards an Integrated Model of Earth's Thermo-Chemical Evolution and Plate Tectonics

    Science.gov (United States)

    Tackley, P. J.; Xie, S.

    2001-05-01

    It has long been a challenge for geodynamicists, who have typically modeled homogeneous mantles, to explain the geochemical evidence for the existence of several distinct chemical reservoirs, in terms of a dynamically and chemically self-consistent model. While the mixing behavior of generalized tracers has received much attention in the modeling community, a recent trend has been towards mantle convection models that track the evolution of specific chemical species, both major and minor, and can thus be related to geochemical observations. However, obtaining realistic chemical evolution in such models is dependent on their having a reasonable representation of plate tectonic behavior since the recycling of oceanic crust and complementary depleted residuum is a key process in Earth that other terrestrial planets may lack. In general, this has required inserting plate motions by hand in models. In recent years, however, we have learned how to perform numerical simulations of mantle convection in which plate tectonic behavior is introduced self-consistently through plastic yielding of the lithosphere. In this presentation, models of mantle convection that combine a treatment of geochemical evolution with self-consistently generated plate tectonics, will be presented. Preliminary results indicate that the system can self-consistently evolve regions which have a HIMU-like signature as well as regions with a high He3/He4 ratio.

  14. A Reducing Atmosphere From Out-gassing of the Early Earth

    Science.gov (United States)

    Schaefer, L.; Fegley, B., Jr.

    2005-08-01

    Earth's present atmosphere originated from out-gassing of volatile-bearing grains. We calculated the composition of volatiles out-gassed from chondritic planetary bodies. We present results for average CI, CM, CV, H, L, and EH chondrites, which are the building blocks of the Earth. From the oxygen-isotope mixing (OIM) model, we calculated a composition of 70% EH, 21% H, 5% CV, and 4% CI chondritic matter for the early Earth. The major out-gassed volatiles for these starting compositions are CH4, N2, NH3, H2, and H2O. The Miller-Urey experiment demonstrated that a reducing atmosphere like this generates amino acids and other organic compounds that are essential for the formation of life. This work is supported by the NASA Astrobiology Program. \\leavevmode \\epsfxsize=0.9\\hsize \\epsfbox{49.eps}

  15. Meteors as a Delivery Vehicle for Organic Matter to the Early Earth

    Science.gov (United States)

    Jenniskens, Peter; DeVincenzi, D. (Technical Monitor)

    2001-01-01

    Only in recent years has a concerted effort been made to study the circumstances under which extraterrestrial organic matter is accreted on Earth by way of meteors. Meteors are the luminous phenomena associated with the (partial) ablation of meteoric matter and represent the dominant pathway from space to Earth, with the possible exception of rare giant impacts of asteroids and comets. Meteors dominated the supply of organics to the early Earth if organic matter survived this pathway efficiently. Moreover, meteors are a source of kinetic energy that can convert inert atmospheric gases such as CO, N, and H2O into useful compounds, such as HCN and NO. Understanding these processes relies heavily on empirical evidence that is still very limited. Here I report on the observations in hand and discuss their relevance in the context of the origin of life.

  16. Rubidium isotopes in primitive chondrites: Constraints on Earth's volatile element depletion and lead isotope evolution

    Science.gov (United States)

    Nebel, O.; Mezger, K.; van Westrenen, W.

    2011-05-01

    The bulk silicate Earth (BSE) shows substantial deficits in volatile elements compared to CI-chondrites and solar abundances. These deficits could be caused by pre-accretionary depletion in the solar nebula during condensation of solids, or by later heat-driven evaporation during collision of small bodies that later accreted to form the Earth. The latter is considered to result in isotope fractionation for elements with low condensation temperatures that correlates with the degree of depletion. Here, we report first high-precision isotope ratio measurements of the moderately volatile and lithophile trace element Rb. Data from seventeen chondrite meteorites show that their Rb isotope abundances are nearly indistinguishable from Earth, not deviating more than 1 per mil in their 87Rb/85Rb. The almost uniform solar system Rb isotope pool suggests incomplete condensation or evaporation in a single stage is unlikely to be the cause of the volatile element deficit of the Earth. As Rb and Pb have similar condensation temperatures, we use their different degrees of depletion in the BSE to address the mechanisms and timing of terrestrial volatile depletion. The Rb isotope data are consistent with a scenario in which the volatile budget of the Earth was generated by a mixture of a highly volatile-element depleted early Proto-Earth with undepleted material in the course of terrestrial accretion. Observed Pb and Rb abundances and U-Pb and Rb-Sr isotope systematics suggest that volatile addition occurred at approximately the same time at which last core-mantle equilibration was achieved. In line with previous suggestions, this last equilibration involved a second stage of Pb (but not Rb) depletion from the BSE. The timing of this second Pb loss event can be constrained to ~ 110 Ma after the start of the solar system. This model supports a scenario with core storage of Pb in the aftermath of a putative Moon forming giant impact that also delivered the bulk of the volatile

  17. Evolution of the solar activity over time and effects on planetary atmospheres. II. kappa^1 Ceti, an analog of the Sun when life arose on Earth

    CERN Document Server

    Ribas, I; Ferreira, L D; Hebrard, E; Selsis, F; Catalan, S; Garces, A; Nascimento, J D do; de Medeiros, J R

    2010-01-01

    The early evolution of Earth's atmosphere and the origin of life took place at a time when physical conditions at the Earth where radically different from its present state. The radiative input from the Sun was much enhanced in the high-energy spectral domain, and in order to model early planetary atmospheres in detail, a knowledge of the solar radiative input is needed. We present an investigation of the atmospheric parameters, state of evolution and high-energy fluxes of the nearby star kap^1 Cet, previously thought to have properties resembling those of the early Sun. Atmospheric parameters were derived from the excitation/ionization equilibrium of Fe I and Fe II, profile fitting of Halpha and the spectral energy distribution. The UV irradiance was derived from FUSE and HST data, and the absolute chromospheric flux from the Halpha line core. From careful spectral analysis and the comparison of different methods we propose for kap^1 Cet the following atmospheric parameters: Teff = 5665+/-30 K (Halpha profil...

  18. Precambrian supercontinents, glaciations, atmospheric oxygenation, metazoan evolution and an impact that may have changed the second half of Earth history

    Directory of Open Access Journals (Sweden)

    Grant M. Young

    2013-05-01

    Full Text Available In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturbations, when extensive glaciations occurred, together with alternating warm periods which were accompanied by atmospheric oxygenation. The younger of these two episodes of climatic oscillation preceded the Cambrian “explosion” of metazoan life forms, but similar extreme climatic conditions existed between about 2.4 and 2.2 Ga. Over long time periods, changing solar luminosity and mantle temperatures have played important roles in regulating Earth's climate but both periods of climatic upheaval are associated with supercontinents. Enhanced weathering on the orogenically and thermally buoyed supercontinents would have stripped CO2 from the atmosphere, initiating a cooling trend that resulted in continental glaciation. Ice cover prevented weathering so that CO2 built up once more, causing collapse of the ice sheets and ushering in a warm climatic episode. This negative feedback loop provides a plausible explanation for multiple glaciations of the Early and Late Proterozoic, and their intimate association with sedimentary rocks formed in warm climates. Between each glacial cycle nutrients were flushed into world oceans, stimulating photosynthetic activity and causing oxygenation of the atmosphere. Accommodation for many ancient glacial deposits was provided by rifting but escape from the climatic cycle was predicated on break-up of the supercontinent, when flooded continental margins had a moderating influence on weathering. The geochemistry of Neoproterozoic cap carbonates carries a strong hydrothermal signal, suggesting that they precipitated from deep sea waters, overturned and spilled onto continental shelves at the termination of glaciations. Paleoproterozoic (Huronian carbonates of the Espanola Formation were probably formed as a result of ponding and evaporation in a hydrothermally influenced, restricted rift setting. Why did metazoan

  19. Proceedings of the Astrobiology Science Conference 2010. Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond

    Science.gov (United States)

    2010-01-01

    The Program of the 2010 Astrobiology Science Conference: Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond, included sessions on: 50 Years of Exobiology and Astrobiology: Greatest Hits; Extraterrestrial Molecular Evolution and Pre-Biological Chemistry: From the Interstellar Medium to the Solar System I; Human Exploration, Astronaut Health; Diversity in Astrobiology Research and Education; Titan: Past, Present, and Future; Energy Flow in Microbial Ecosystems; Extraterrestrial Molecular Evolution and Prebiological Chemistry: From the Interstellar Medium to the Solar System II; Astrobiology in Orbit; Astrobiology and Interdisciplinary Communication; Science from Rio Tinto: An Acidic Environment; Can We Rule Out Spontaneous Generation of RNA as the Key Step in the Origin of Life?; How Hellish Was the Hadean Earth?; Results from ASTEP and Other Astrobiology Field Campaigns I; Prebiotic Evolution: From Chemistry to Life I; Adaptation of Life in Hostile Space Environments; Extrasolar Terrestrial Planets I: Formation and Composition; Collaborative Tools and Technology for Astrobiology; Results from ASTEP and Other Astrobiology Field Campaigns II; Prebiotic Evolution: From Chemistry to Life II; Survival, Growth, and Evolution of Microrganisms in Model Extraterrestrial Environments; Extrasolar Terrestrial Planets II: Habitability and Life; Planetary Science Decadal Survey Update; Astrobiology Research Funding; Bioessential Elements Through Space and Time I; State of the Art in Life Detection; Terrestrial Evolution: Implications for the Past, Present, and Future of Life on Earth; Psychrophiles and Polar Environments; Life in Volcanic Environments: On Earth and Beyond; Geochronology and Astrobiology On and Off the Earth; Bioessential Elements Through Space and Time II; Origins and Evolution of Genetic Systems; Evolution of Advanced Life; Water-rich Asteroids and Moons: Composition and Astrobiological Potential; Impact Events and Evolution; A Warm, Wet

  20. Proceedings of the Astrobiology Science Conference 2010. Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond

    Science.gov (United States)

    2010-01-01

    The Program of the 2010 Astrobiology Science Conference: Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond, included sessions on: 50 Years of Exobiology and Astrobiology: Greatest Hits; Extraterrestrial Molecular Evolution and Pre-Biological Chemistry: From the Interstellar Medium to the Solar System I; Human Exploration, Astronaut Health; Diversity in Astrobiology Research and Education; Titan: Past, Present, and Future; Energy Flow in Microbial Ecosystems; Extraterrestrial Molecular Evolution and Prebiological Chemistry: From the Interstellar Medium to the Solar System II; Astrobiology in Orbit; Astrobiology and Interdisciplinary Communication; Science from Rio Tinto: An Acidic Environment; Can We Rule Out Spontaneous Generation of RNA as the Key Step in the Origin of Life?; How Hellish Was the Hadean Earth?; Results from ASTEP and Other Astrobiology Field Campaigns I; Prebiotic Evolution: From Chemistry to Life I; Adaptation of Life in Hostile Space Environments; Extrasolar Terrestrial Planets I: Formation and Composition; Collaborative Tools and Technology for Astrobiology; Results from ASTEP and Other Astrobiology Field Campaigns II; Prebiotic Evolution: From Chemistry to Life II; Survival, Growth, and Evolution of Microrganisms in Model Extraterrestrial Environments; Extrasolar Terrestrial Planets II: Habitability and Life; Planetary Science Decadal Survey Update; Astrobiology Research Funding; Bioessential Elements Through Space and Time I; State of the Art in Life Detection; Terrestrial Evolution: Implications for the Past, Present, and Future of Life on Earth; Psychrophiles and Polar Environments; Life in Volcanic Environments: On Earth and Beyond; Geochronology and Astrobiology On and Off the Earth; Bioessential Elements Through Space and Time II; Origins and Evolution of Genetic Systems; Evolution of Advanced Life; Water-rich Asteroids and Moons: Composition and Astrobiological Potential; Impact Events and Evolution; A Warm, Wet

  1. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  2. The not-so-sublime early Earth recorded in Hadean zircons

    Science.gov (United States)

    Cavosie, A. J.

    2011-12-01

    The first few hundred million years following accretion is the least understood eon in the geologic time scale- the Hadean. This poorly defined eon continues to both challenge and fascinate scientists seeking to understand the early Earth, as the most profound planet-wide transition in Earth history occurred during the Hadean: the post-accretion transformation from a meteorite impact dominated, partially molten, steam covered mafic surface on a 'Hot Earth', to a solidified, granitoid-bearing, water covered, life-supporting 'Cool Earth'. Intact rocks from the Hadean have not been identified; other means are thus required to study early Earth processes, such as the appearance, formation, and processing of evolved crust, duration of early impacts and magma oceans, the appearance of liquid water and oceans, and ultimately, stabilization of habitats for life. Hadean detrital zircons found in younger sedimentary rocks in Australia, China, and the USA constitute a mineral record from the early Earth that enables 'ground truth' constraints to be placed on early Earth processes. Hadean zircons are complicated and originate from myriad sources; identification of grains that preserve magmatic composition is critical (as evidenced by growth zoning in CL, concordant U-Pb systematics, trace element abundances and ratios), as many have been modified by secondary processes. Detailed documentation of analyzed material is paramount. A generally consistent understanding of processes on the Hadean Earth is emerging, based on data from well-documented igneous zircons with concordant U-Pb systems: (1) A record of continuous magmatism and rock-forming events starting at 4.4 Ga is recorded in U-Pb ages of Hadean zircons; no periods of magmatic quiescence occur in the Hadean. (2) Coupled Lu/Hf and U/Pb data require formation of evolved crust from extracted Hadean reservoirs by 4.5 to 4.4 Ga. (3) Mineral inclusion suites, low Ti and high Li abundances, trace elements (U-Yb), and elevated

  3. An early geodynamo driven by exsolution of mantle components from Earth's core.

    Science.gov (United States)

    Badro, James; Siebert, Julien; Nimmo, Francis

    2016-08-18

    Recent palaeomagnetic observations report the existence of a magnetic field on Earth that is at least 3.45 billion years old. Compositional buoyancy caused by inner-core growth is the primary driver of Earth's present-day geodynamo, but the inner core is too young to explain the existence of a magnetic field before about one billion years ago. Theoretical models propose that the exsolution of magnesium oxide--the major constituent of Earth's mantle--from the core provided a major source of the energy required to drive an early dynamo, but experimental evidence for the incorporation of mantle components into the core has been lacking. Indeed, terrestrial core formation occurred in the early molten Earth by gravitational segregation of immiscible metal and silicate melts, transporting iron-loving (siderophile) elements from the silicate mantle to the metallic core and leaving rock-loving (lithophile) mantle components behind. Here we present experiments showing that magnesium oxide dissolves in core-forming iron melt at very high temperatures. Using core-formation models, we show that extreme events during Earth's accretion (such as the Moon-forming giant impact) could have contributed large amounts of magnesium to the early core. As the core subsequently cooled, exsolution of buoyant magnesium oxide would have taken place at the core–mantle boundary, generating a substantial amount of gravitational energy as a result of compositional buoyancy. This amount of energy is comparable to, if not more than, that produced by inner-core growth, resolving the conundrum posed by the existence of an ancient magnetic field prior to the formation of the inner core.

  4. Correlating early evolution of parasitic platyhelminths to Gondwana breakup.

    Science.gov (United States)

    Badets, Mathieu; Whittington, Ian; Lalubin, Fabrice; Allienne, Jean-Francois; Maspimby, Jean-Luc; Bentz, Sophie; Du Preez, Louis H; Barton, Diane; Hasegawa, Hideo; Tandon, Veena; Imkongwapang, Rangpenyuba; Imkongwapang, Rangpenyubai; Ohler, Annemarie; Combes, Claude; Verneau, Olivier

    2011-12-01

    Investigating patterns and processes of parasite diversification over ancient geological periods should involve comparisons of host and parasite phylogenies in a biogeographic context. It has been shown previously that the geographical distribution of host-specific parasites of sarcopterygians was guided, from Palaeozoic to Cainozoic times, mostly by evolution and diversification of their freshwater hosts. Here, we propose phylogenies of neobatrachian frogs and their specific parasites (Platyhelminthes, Monogenea) to investigate coevolutionary processes and historical biogeography of polystomes and further discuss all the possible assumptions that may account for the early evolution of these parasites. Phylogenetic analyses of concatenated rRNA nuclear genes (18S and partial 28S) supplemented by cophylogenetic and biogeographic vicariance analyses reveal four main parasite lineages that can be ascribed to centers of diversity, namely Australia, India, Africa, and South America. In addition, the relationships among these biogeographical monophyletic groups, substantiated by molecular dating, reflect sequential origins during the breakup of Gondwana. The Australian polystome lineage may have been isolated during the first stages of the breakup, whereas the Indian lineage would have arisen after the complete separation of western and eastern Gondwanan components. Next, polystomes would have codiverged with hyloid sensu stricto and ranoid frog lineages before the completion of South American and African plate separation. Ultimately, they would have undergone an extensive diversification in South America when their ancestral host families diversified. Therefore, the presence of polystome parasites in specific anuran host clades and in discrete geographic areas reveals the importance of biogeographic vicariance in diversification processes and supports the occurrence and radiation of amphibians over ancient and recent geological periods.

  5. Impact melting of frozen oceans on the early Earth: implications for the origin of life

    Science.gov (United States)

    Bada, J. L.; Bigham, C.; Miller, S. L.

    1994-01-01

    Without sufficient greenhouse gases in the atmosphere, the early Earth would have become a permanently frozen planet because the young Sun was less luminous than it is today. Several resolutions to this faint young Sun-frozen Earth paradox have been proposed, with an atmosphere rich in CO2 being the one generally favored. However, these models assume that there were no mechanisms for melting a once frozen ocean. Here we show that bolide impacts between about 3.6 and 4.0 billion years ago could have episodically melted an ice-covered early ocean. Thaw-freeze cycles associated with bolide impacts could have been important for the initiation of abiotic reactions that gave rise to the first living organisms.

  6. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions

    Science.gov (United States)

    Barnes, R.

    2015-01-01

    Abstract The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the “tidal zone,” where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life. Key Words

  7. The hills are alive: Earth surface dynamics in the University of Arizona Landscape Evolution Observatory

    Science.gov (United States)

    DeLong, S.; Troch, P. A.; Barron-Gafford, G. A.; Huxman, T. E.; Pelletier, J. D.; Dontsova, K.; Niu, G.; Chorover, J.; Zeng, X.

    2012-12-01

    To meet the challenge of predicting landscape-scale changes in Earth system behavior, the University of Arizona has designed and constructed a new large-scale and community-oriented scientific facility - the Landscape Evolution Observatory (LEO). The primary scientific objectives are to quantify interactions among hydrologic partitioning, geochemical weathering, ecology, microbiology, atmospheric processes, and geomorphic change associated with incipient hillslope development. LEO consists of three identical, sloping, 333 m2 convergent landscapes inside a 5,000 m2 environmentally controlled facility. These engineered landscapes contain 1 meter of basaltic tephra ground to homogenous loamy sand and contains a spatially dense sensor and sampler network capable of resolving meter-scale lateral heterogeneity and sub-meter scale vertical heterogeneity in moisture, energy and carbon states and fluxes. Each ~1000 metric ton landscape has load cells embedded into the structure to measure changes in total system mass with 0.05% full-scale repeatability (equivalent to less than 1 cm of precipitation), to facilitate better quantification of evapotraspiration. Each landscape has an engineered rain system that allows application of precipitation at rates between3 and 45 mm/hr. These landscapes are being studied in replicate as "bare soil" for an initial period of several years. After this initial phase, heat- and drought-tolerant vascular plant communities will be introduced. Introduction of vascular plants is expected to change how water, carbon, and energy cycle through the landscapes, with potentially dramatic effects on co-evolution of the physical and biological systems. LEO also provides a physical comparison to computer models that are designed to predict interactions among hydrological, geochemical, atmospheric, ecological and geomorphic processes in changing climates. These computer models will be improved by comparing their predictions to physical measurements made in

  8. False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth.

    Science.gov (United States)

    Reinhard, Christopher T; Olson, Stephanie L; Schwieterman, Edward W; Lyons, Timothy W

    2017-04-01

    Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.

  9. Alkali element depletion by core formation and vaporization on the early Earth

    Science.gov (United States)

    Lodders, K.; Fegley, B., Jr.

    1994-01-01

    The depletion of Na, K, Rb, and Cs in the Earth's upper mantle and crust relative to their abundances in chondrites is a long standing problem in geochemistry. Here we consider two commonly invoked mechanisms, namely core formation, and vaporization, for producing the observed depletions. Our models predict that a significant percentage of the Earth's bulk alkali element inventory is in the core (30 percent for Na, 52 percent for K, 74 percent for Rb, and 92 percent for Cs). These predictions agree with independent estimates from nebular volatility trends and (for K) from terrestrial heat flow data. Our models also predict that vaporization and thermal escape during planetary accretion are unlikely to produce the observed alkali element depletion pattern. However, loss during the putative giant impact which formed the Moon cannot be ruled out. Experimental, observational, and theoretical tests of our predictions are also described. Alkali element partitioning into the Earth's core was modeled by assuming that alkali element partitioning during core formation on the aubrite parent body (APB) is analogous to that on the early Earth. The analogy is reasonable for three reasons. First, the enstatite meteorites are the only known meteorites with the same oxygen isotope systematics as the Earth-Moon system. Second, the large core size of the Earth and the V depletion in the mantle requires accretion from planetesimals as reduced as the enstatite chondrites. Third, experimental studies of K partitioning between silicate and metal plus sulfide show that more K goes into the metal plus sulfide at higher pressures than at one atmosphere pressure. Thus partitioning in the relatively low pressure natural laboratory of the APB is a good guide to alkali elemental partitioning during the growth of the Earth.

  10. THE PRECAMBRIAN HISTORY OF THE ORIGIN AND EVOLUTION OF THE SOLAR SYSTEM AND EARTH. PART 1

    Directory of Open Access Journals (Sweden)

    M. I. Kuz’min

    2015-09-01

    Full Text Available The paper provides a review of early stages of development the Solar System and the geological history of Earth with reference to the latest data on the origin of the Solar System and the formation of the first continental rocks and results of studies of zircon, the oldest mineral so far dated on Earth. The formation of the Solar System from a gas-and-dust nebula is estimated to have begun 4.568 billion years ago. Ice was formed 1.5 million years later; it concentrated at the periphery of the system and served as the material for the largest planets, Jupiter and Saturn. In the central areas of the system, asteroids with diameters of about 10 km were formed. Their small bodies were composed of the basic material of the solar nebula, as evidenced by carbonaceous chondrite, CI, which composition is similar to the composition of the Sun, with the exception of hydrogen, helium, and volatile components that served as the main material for peripheral planets of the Solar System. Due to collision and partial merger of such small bodies, the formation of embryos of the terrestrial planets was initiated. Gravity made such embryos to cluster into larger bodies. After 7 million years, large asteroids and planet Mars were formed. It took 11 million years to form Planet Earth with a mass of 63 %, and 30 million years to form 93 % of its mass. Almost from the beginning of the formation of the Earth, short-lived radionuclides, 26Al and 60Fe, caused warming up of the small planetary bodies which led to the formation of their cores. During the initial stages, small magma reservoirs were formed, and molten iron particles gathered in the centres of the planetary bodies. As suggested by the ratio of 182W/184W, the major part of the core was formed within 20 million years, while its full mass accumulated completely within the next 50 million years. In 30–40 million years after the creation of the Solar System, the Earth collided with a cosmic body which mass was

  11. Early resistance change and stress/electromigration evolution in near bamboo interconnects

    NARCIS (Netherlands)

    Petrescu, V.; Mouthaan, A.J.; Dima, G.; Govoreanu, B.; Mitrea, O.; Profirescu, M.

    1997-01-01

    A complete description for early resistance change and mechanical stress evolution in near-bamboo interconnects, related to the electromigration, is given in this paper. The proposed model, for the first time, combines the stress/vacancy concentration evolution with the early resistance change of

  12. The sustainability of habitability on terrestrial planets: Insights, questions, and needed measurements from Mars for understanding the evolution of Earth-like worlds

    Science.gov (United States)

    Ehlmann, B. L.; Anderson, F. S.; Andrews-Hanna, J.; Catling, D. C.; Christensen, P. R.; Cohen, B. A.; Dressing, C. D.; Edwards, C. S.; Elkins-Tanton, L. T.; Farley, K. A.; Fassett, C. I.; Fischer, W. W.; Fraeman, A. A.; Golombek, M. P.; Hamilton, V. E.; Hayes, A. G.; Herd, C. D. K.; Horgan, B.; Hu, R.; Jakosky, B. M.; Johnson, J. R.; Kasting, J. F.; Kerber, L.; Kinch, K. M.; Kite, E. S.; Knutson, H. A.; Lunine, J. I.; Mahaffy, P. R.; Mangold, N.; McCubbin, F. M.; Mustard, J. F.; Niles, P. B.; Quantin-Nataf, C.; Rice, M. S.; Stack, K. M.; Stevenson, D. J.; Stewart, S. T.; Toplis, M. J.; Usui, T.; Weiss, B. P.; Werner, S. C.; Wordsworth, R. D.; Wray, J. J.; Yingst, R. A.; Yung, Y. L.; Zahnle, K. J.

    2016-10-01

    What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar system's longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to

  13. The Sustainability of Habitability on Terrestrial Planets: Insights, Questions, and Needed Measurements from Mars for Understanding the Evolution of Earth-Like Worlds

    Science.gov (United States)

    Ehlmann, B. L.; Anderson, F. S.; Andrews-Hanna, J.; Catling, D. C.; Christensen, P. R.; Cohen, B. A.; Dressing, C. D.; Edwards, C. S.; Elkins-Tanton, L. T.; Farley, K. A.; hide

    2016-01-01

    What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar systems longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to

  14. Proceedings of the Astrobiology Science Conference 2010. Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond

    Science.gov (United States)

    2010-01-01

    The Program of the 2010 Astrobiology Science Conference: Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond, included sessions on: 50 Years of Exobiology and Astrobiology: Greatest Hits; Extraterrestrial Molecular Evolution and Pre-Biological Chemistry: From the Interstellar Medium to the Solar System I; Human Exploration, Astronaut Health; Diversity in Astrobiology Research and Education; Titan: Past, Present, and Future; Energy Flow in Microbial Ecosystems; Extraterrestrial Molecular Evolution and Prebiological Chemistry: From the Interstellar Medium to the Solar System II; Astrobiology in Orbit; Astrobiology and Interdisciplinary Communication; Science from Rio Tinto: An Acidic Environment; Can We Rule Out Spontaneous Generation of RNA as the Key Step in the Origin of Life?; How Hellish Was the Hadean Earth?; Results from ASTEP and Other Astrobiology Field Campaigns I; Prebiotic Evolution: From Chemistry to Life I; Adaptation of Life in Hostile Space Environments; Extrasolar Terrestrial Planets I: Formation and Composition; Collaborative Tools and Technology for Astrobiology; Results from ASTEP and Other Astrobiology Field Campaigns II; Prebiotic Evolution: From Chemistry to Life II; Survival, Growth, and Evolution of Microrganisms in Model Extraterrestrial Environments; Extrasolar Terrestrial Planets II: Habitability and Life; Planetary Science Decadal Survey Update; Astrobiology Research Funding; Bioessential Elements Through Space and Time I; State of the Art in Life Detection; Terrestrial Evolution: Implications for the Past, Present, and Future of Life on Earth; Psychrophiles and Polar Environments; Life in Volcanic Environments: On Earth and Beyond; Geochronology and Astrobiology On and Off the Earth; Bioessential Elements Through Space and Time II; Origins and Evolution of Genetic Systems; Evolution of Advanced Life; Water-rich Asteroids and Moons: Composition and Astrobiological Potential; Impact Events and Evolution; A Warm, Wet

  15. Proceedings of the Astrobiology Science Conference 2010. Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond

    Science.gov (United States)

    2010-01-01

    The Program of the 2010 Astrobiology Science Conference: Evolution and Life: Surviving Catastrophes and Extremes on Earth and Beyond, included sessions on: 50 Years of Exobiology and Astrobiology: Greatest Hits; Extraterrestrial Molecular Evolution and Pre-Biological Chemistry: From the Interstellar Medium to the Solar System I; Human Exploration, Astronaut Health; Diversity in Astrobiology Research and Education; Titan: Past, Present, and Future; Energy Flow in Microbial Ecosystems; Extraterrestrial Molecular Evolution and Prebiological Chemistry: From the Interstellar Medium to the Solar System II; Astrobiology in Orbit; Astrobiology and Interdisciplinary Communication; Science from Rio Tinto: An Acidic Environment; Can We Rule Out Spontaneous Generation of RNA as the Key Step in the Origin of Life?; How Hellish Was the Hadean Earth?; Results from ASTEP and Other Astrobiology Field Campaigns I; Prebiotic Evolution: From Chemistry to Life I; Adaptation of Life in Hostile Space Environments; Extrasolar Terrestrial Planets I: Formation and Composition; Collaborative Tools and Technology for Astrobiology; Results from ASTEP and Other Astrobiology Field Campaigns II; Prebiotic Evolution: From Chemistry to Life II; Survival, Growth, and Evolution of Microrganisms in Model Extraterrestrial Environments; Extrasolar Terrestrial Planets II: Habitability and Life; Planetary Science Decadal Survey Update; Astrobiology Research Funding; Bioessential Elements Through Space and Time I; State of the Art in Life Detection; Terrestrial Evolution: Implications for the Past, Present, and Future of Life on Earth; Psychrophiles and Polar Environments; Life in Volcanic Environments: On Earth and Beyond; Geochronology and Astrobiology On and Off the Earth; Bioessential Elements Through Space and Time II; Origins and Evolution of Genetic Systems; Evolution of Advanced Life; Water-rich Asteroids and Moons: Composition and Astrobiological Potential; Impact Events and Evolution; A Warm, Wet

  16. Evolution of the Oxidation State of the Earth's Mantle: Challenges of High Pressure Quenching

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, R.; Rahman, Z.

    2015-01-01

    The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3+ at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. Experiments of more mafic compositions and at higher pressures commonly form a polyphase quench intergrowth composed primarily of pyroxenes, with interstitial glass which hosts nearly all of the more volatile minor elements. In our previous experiments on shergottite compositions, variable fO2, T, and P is less than 4 GPa, Fe3+/TotFe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3+/TotFe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3+. Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Experiments with Knippa basalt as the starting composition were conducted at 1-8 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products from 7-8 GPa quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal Fe3+/2+. A number of different approaches have been employed to produce glassy samples that can be measured by EELS and XANES. A more intermediate andesite was used in one experiment, and decompression during quenching was attempted after, but both resulted in a finer grained polyphase texture. Experiments are currently underway to test different capsule materials may affect quench texture. A preliminary experiment using liquid nitrogen to greatly enhance the rate of cooling of the assembly has also been attempted and this technique will be

  17. Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

    Science.gov (United States)

    Willis, Emily M.; Pour, Maria Z. A.

    2017-01-01

    High voltage solar array interactions with the space environment can have a significant impact on array performance and spacecraft charging. Over the past 10 years, data from the International Space Station has allowed for detailed observations of these interactions over long periods of time. Some of the surprising observations have been floating potential transients, which were not expected and are not reproduced by existing models. In order to understand the underlying processes producing these transients, the temporal evolution of the plasma sheath surrounding the solar cells in low Earth orbit is being investigated. This study includes lumped element modeling and particle-in-cell simulation methods. This presentation will focus on recent results from the on-going investigations.

  18. A new time tree reveals Earth history's imprint on the evolution of modern birds.

    Science.gov (United States)

    Claramunt, Santiago; Cracraft, Joel

    2015-12-01

    Determining the timing of diversification of modern birds has been difficult. We combined DNA sequences of clock-like genes for most avian families with 130 fossil birds to generate a new time tree for Neornithes and investigated their biogeographic and diversification dynamics. We found that the most recent common ancestor of modern birds inhabited South America around 95 million years ago, but it was not until the Cretaceous-Paleogene transition (66 million years ago) that Neornithes began to diversify rapidly around the world. Birds used two main dispersion routes: reaching the Old World through North America, and reaching Australia and Zealandia through Antarctica. Net diversification rates increased during periods of global cooling, suggesting that fragmentation of tropical biomes stimulated speciation. Thus, we found pervasive evidence that avian evolution has been influenced by plate tectonics and environmental change, two basic features of Earth's dynamics.

  19. The Formation and Early Evolution of Young Massive Clusters

    CERN Document Server

    Longmore, Steven N; Bastian, Nate; Bally, John; Rathborne, Jill; Testi, Leonardo; Stolte, Andrea; Dale, James; Bressert, Eli; Alves, Joao

    2014-01-01

    We review the formation and early evolution of the most massive and dense young stellar clusters, focusing on the role they can play in our understanding of star and planet formation as a whole. Young massive cluster (YMC) progenitor clouds in the Galactic Center can accumulate to a high enough density without forming stars that the initial protostellar densities are close to the final stellar density. For this to hold in the disk, the time scale to accumulate the gas to such high densities must be much shorter than the star formation timescale. Otherwise the gas begins forming stars while it is being accumulated to high density. The distinction between the formation regimes in the two environments is consistent with the predictions of environmentally-dependent density thresholds for star formation. This implies that stars in YMCs of similar total mass and radius can have formed at widely different initial protostellar densities. The fact that no systematic variations in fundamental properties are observed be...

  20. Origins and early evolution of the translation machinery

    Science.gov (United States)

    Fox, George E.

    2010-09-01

    The modern ribosome is a complex biological machine that is responsible for chiral synthesis of cellular proteins according to the genetic code as specified by a mRNA. Major portions of the ribosomal machinery were likely in place before the last universal common ancestor (LUCA) of life. The early evolution of the ribosome has implications for the origin of the genetic code, the emergence of chirality in peptide synthesis, and the emergence of LUCA. Although codon assignments may remain a mystery, the history of the ribosome provides a context for dating the first usage of mRNA. In the case of chirality, the modern ribosome suggests that a small initial chiral preference for L-amino acids in the environment may have been greatly enhanced by a two step process in which the charging of a primitive tRNA and the subsequent synthesis of a peptide bond both had the same chiral preference. The resulting ability to make largely chiral peptides may have provided an advantage over other prebiotic mechanisms for making peptides. Finally, the late addition of factors such as EF-G may have greatly accelerated the emerging ribosome's ability to synthesize proteins, thereby allowing entities with this novel capability to emerge as the LUCA.

  1. Milgram's Obedience to Authority experiments: origins and early evolution.

    Science.gov (United States)

    Russell, Nestar John Charles

    2011-03-01

    Stanley Milgram's Obedience to Authority experiments remain one of the most inspired contributions in the field of social psychology. Although Milgram undertook more than 20 experimental variations, his most (in)famous result was the first official trial run - the remote condition and its 65% completion rate. Drawing on many unpublished documents from Milgram's personal archive at Yale University, this article traces the historical origins and early evolution of the obedience experiments. Part 1 presents the previous experiences that led to Milgram's conception of his rudimentary research idea and then details the role of his intuition in its refinement. Part 2 traces the conversion of Milgram's evolving idea into a reality, paying particular attention to his application of the exploratory method of discovery during several pilot studies. Both parts illuminate Milgram's ad hoc introduction of various manipulative techniques and subtle tension-resolving refinements. The procedural adjustments continued until Milgram was confident that the first official experiment would produce a high completion rate, a result contrary to expectations of people's behaviour. Showing how Milgram conceived of, then arrived at, this first official result is important because the insights gained may help others to determine theoretically why so many participants completed this experiment.

  2. Kinematic and chemical evolution of early-type galaxies

    CERN Document Server

    Ziegler, B L; Böhm, A; Bender, R; Fritz, A; Maraston, C

    2004-01-01

    We investigate in detail 13 early-type field galaxies with 0.2evolution in the B-band of 0.3-0.5mag for both samples. We compare measured Lick absorption line strengths (Hdelta, Hgamma, Hbeta, Mg_b, & Fe5335) with evolutionary stellar population models to derive light-averaged ages, metallicities and the element abundance ratios Mg/Fe. We find that all these three stellar parameters of the distant galaxies obey a scaling with velocity dispersion (mass) which is very well consistent with the one of local nearby galaxies. In particular, the distribution...

  3. The Early Evolution of Primordial Pair-Instability Supernovae

    CERN Document Server

    Joggerst, C C

    2010-01-01

    The observational signatures of the first cosmic explosions and their chemical imprint on second-generation stars both crucially depend on how heavy elements mix within the star at the earliest stages of the blast. We present numerical simulations of the early evolution of Population III pair-instability supernovae with the new adaptive mesh refinement code CASTRO. In stark contrast to 15 - 40 Msun core-collapse primordial supernovae, we find no mixing in most 150 - 250 Msun pair-instability supernovae out to times well after breakout from the surface of the star. This may be the key to determining the mass of the progenitor of a primeval supernova, because vigorous mixing will cause emission lines from heavy metals such as Fe and Ni to appear much sooner in the light curves of core-collapse supernovae than in those of pair-instability explosions. Our results also imply that unlike low-mass Pop III supernovae, whose collective metal yields can be directly compared to the chemical abundances of extremely metal...

  4. Merging of phonological and gestural circuits in early language evolution.

    Science.gov (United States)

    Aboitiz, Francisco; García, Ricardo

    2009-01-01

    In the monkey, cortical auditory projections subdivide into a dorsal stream mostly involved in spatiotemporal processing, that projects mainly to dorsal frontal areas; and a ventral stream involved in stimulus identification, connected to the ventrolateral prefrontal cortex (VLPFC). We propose that in the human lineage, part of the dorsal auditory pathway has specialized in vocalization processing, enhancing vocal repetition and short-term memory capacities that are crucial for linguistic development. In the human, the vocalization-related dorsal auditory component tends to converge in the VLPFC with the ventral auditory stream and with projections involved in gestural control; and consists of a direct connection between the auditory cortex and the VLPFC via the arcuate fasciculus, and an indirect pathway via the supramarginal gyrus. Additionally, intraparietal and inferior parietal afferents to the VLPFC are associated with communicative hand gestures, with manipulation skills and with early tool-making. Although in general terms compatible with the mirror-neuron gestural hypothesis for language origins, this proposal underlines the participation of the dorsal auditory pathway in voice processing as a key event that marked the beginning of human phonology and the subsequent evolution of language. Instead, the mirror neuron system for gestures and the primitive vocalization network (ventral pathway) contributed to provide a communicative scaffolding that facilitated the emergence of human-like phonology. Furthermore, we emphasize the phylogenetic continuity (homology) between non-human and human vocalization and their neural substrates, something that is not usually stressed in the mirror neuron perspective.

  5. Chemical evolution and the preservation of organic compounds on Mars

    Science.gov (United States)

    Kanavarioti, Anastassia; Mancinelli, Rocco L.

    1989-01-01

    Several lines of evidence suggest that the environment on early Mars and early Earth were very similar. Since life is abundant on Earth, it seems likely that conditions on early Earth were conducive to chemical evolution and the origin of life. The similarity between early Mars and early Earth encourages the hypothesis that chemical evolution might have also occurred on Mars, but that decreasing temperatures and the loss of its atmosphere brought the evolution to a halt. The possibility of finding on Mars remnants of organic material dating back to this early clement period is addressed.

  6. Geoethics and philosophy of Earth sciences: the role of geophysical factors in human evolution

    Directory of Open Access Journals (Sweden)

    Telmo Pievani

    2012-07-01

    Full Text Available This article explores the role of philosophy of the Earth sciences in the foundation of the principles of ‘geoethics’. In particular, the focus is on two different examples of philosophical analysis in the field of geosciences: the first is the trial against the Italian National Commission for Forecasting and Predicting Great Risks, which was charged with negligence in communication and prediction on the occasion of the earthquake that almost destroyed the city of L’Aquila on the night of April 6, 2009; the second is related to the scientific and theoretical consequences of the updated geographical scenario of the human global populating of the Earth, based on archeological, paleontological and genetic data. Our concept of ‘scientific prediction’ in the case of geophysical phenomena and the new ways to see human evolution that depend on geophysical factors have ethical and philosophical implications that are crucial for the foundations of geoethics. The tentative conclusion is that we need an evolutionary sense of belonging to our Planet, and a concept of ‘natural’ phenomena and ‘natural’ disasters that should not be an alibi for the underestimation of our political and ethical responsibilities.

  7. On the importance of lowermost mantle melt in the long term evolution of the Earth

    Science.gov (United States)

    Labrosse, S.; Hernlund, J. W.; Coltice, N.

    2011-12-01

    The thermal evolution of the Earth is usually modeled using its global energy balance and a scaling law for the heat transfer by mantle convection where the heat flow q depends on the mantle potential temperature T and its viscosity η as q=AT1+βη-β, with typical fluid dynamics models giving β≈1/3. The present small ratio of heat production to heat loss (Urey ratio) implies a large secular cooling rate and, because of the feedback from temperature dependent viscosity, backward calculations from the present time lead to a completely molten Earth about 1 Gyr ago. Starting with Christensen (1985), values of β smaller than 1/3 have been proposed to solve this problem by reducing the strength of the feedback loop between core temperature and surface heat flow. However, a self-consistent theory of mantle convection is still lacking to justify unconventional β values. We propose an entirely different approach recognizing that the lowermost mantle, which presently shows evidence of partial melting (ULVZs), was likely largely molten in its hotter past. Coupling a parameterized model of mantle convection using standard scalings for the solid upper part to a crystallizing basal magma ocean (BMO) enriched in radioactive elements and the core cuts the feedback loop very efficiently by introducing two independent potential temperatures. Backward integration of the model makes the core and the BMO hotter in the past while keeping the solid mantle temperature reasonable. A thermal catastrophe may in fact have happened, but only deep in the Earth!

  8. Early Earth tectonics: A high-resolution 3D numerical modelling approach

    Science.gov (United States)

    Fischer, R.; Gerya, T.

    2014-12-01

    Early Earth had a higher amount of remaining radiogenic elements as well as a higher amount of leftover primordial heat. Both contributed to the increased temperature in the Earth's interior and it is mainly this increased mantle potential temperature ΔTp that controls the dynamics of the crust and upper mantle and the style of Early Earth tectonics. For a minor increase in temperature ΔTp buckling, delamination and Rayleigh-Taylor style dripping of the plate is observed in addition. For higher temperatures ΔTp > 250 K no subduction can be observed anymore and tectonics is dominated by delamination and Rayleigh-Taylor instabilities. We conduct 3D petrological-thermomechanical numerical modelling experiments of the crust and upper mantle under Early Earth conditions and a plume tectonics model setup. For varying crustal structures and an increased mantle potential temperature ΔTp, a thermal anomaly in the bottom temperature boundary introduces a plume. The model is able to self-sufficiently form depleted mantle lithosphere after repeated melt removal. New crust can be produced in the form of volcanics or plutonics. To simulate differentiation the newly formed crust can have a range in composition from basaltic over dacitic to granitic depending on its source rock. Models show large amounts of subcrustal decompression melting and consequently large amounts of new formed crust which in turn influences the dynamics. Mantle and crust are convecting separately. Dome-shaped plutons of mafic or felsic composition can be observed in the crust. Between these domes elongated belts of upper crust, volcanics and sediments are formed. These structures look similar to, for example, the Kaapvaal craton in South Africa where the elongated shape of the Barberton Greenstone Belt is surrounded by multiple plutons.

  9. On the effects of the evolution of microbial mats and land plants on the Earth as a planet. Photometric and spectroscopic light curves of paleo-Earths

    CERN Document Server

    Sanromá, E; García-Muñoz, A

    2013-01-01

    Understanding the spectral and photometric variability of the Earth and the rest of the Solar System planets has become of the utmost importance for the future characterization of rocky exoplanets. As this is not only interesting at present times but also along the planetary evolution, we studied the effect that the evolution of microbial mats and plants over land has had on the way our planet looks from afar. As life evolved, continental surfaces changed gradually and non- uniformly from deserts through microbial mats to land plants, modifying the reflective properties of the ground and most probably the distribution of moisture and cloudiness. Here, we used a radiative transfer model of the Earth, together with geological paleo-records of the continental distribution and a reconstructed cloud distribution, to simulate the visible and near-IR radiation reflected by our planet as a function of the Earth's rotation. We found that the evolution from deserts to microbial mats and to land plants produce detectabl...

  10. Genesis and evolution of dust in the early Universe

    Science.gov (United States)

    Gall, Christa

    2010-10-01

    The most fascinating aspect of studying dust is the fact that small dust particles of a few micrometer which we cannot see with our naked eyes are a fundamentally important component in a Universe whose dimension we hardly can imagine. Dust grains impact the evolution of the Universe in many ways. For example they are known as the main formation site of molecular hydrogen which acts as important coolant by the formation of stars similar to our Sun. Dust is essential for the formation of planets and plays an important role in the end stages of life of most stars. Large amounts of dust have been discovered in quasars (QSOs) at high redshift where the epoch of cosmic evolution was ! 1 Gyr, but the origin and evolution of these remains elusive. Supernovae (SNe) and asymptotic giant branch (AGB) stars have been contemplated as prime dust sources due to their potential ability of generating sufficiently high amounts of dust. Though AGB stars are in fact known as the main dust source in the present Universe, their partially (too) long lifetimes questions their significance as dust contributers in the early Universe. SNe are sufficiently short-lived, but there exists a discrepancy between observationally and theoretically ascertained dust yields. The principal aim of this thesis is to elucidate the astrophysical conditions required for generating these large amounts of dust in massive starburst galaxies and QSOs at high redshift. We first intend to identify the mass ranges of the most efficient dust producing stars at high redshift. We ascertain the dust production efficiency of stars in the mass range 3-40 M⊙ using observed and theoretical dust yields of AGB stars and SNe. Based on these efficiencies we determine the total dust productivity for different stellar sources and investigate its dependency on the initial mass function (IMF). It is found that the dust production efficiency generally decreases with increasing progenitor mass. The total dust production strongly

  11. Water and the Earth System in the Anthropocene: Evolution of Socio-Hydrology

    Science.gov (United States)

    Sivapalan, M.; Bloeschl, G.

    2014-12-01

    Over the past century, hydrological science has evolved through distinct eras as judged by ideas, information sources, technological advances and societal influences: Empirical Era which was data based with little theory, Systems Era that focused on input-output relationships, Process Era with a focus on processes, and the Geosciences Era where hydrology was considered an Earth System science. We argue that as the human footprint on earth becomes increasingly dominant, we are moving into a Co-evolution Era. Co-evolution implies that the components of the Earth system are intimately intertwined at many time scales - fast scales of immediate feedbacks that translate into slow scale interdependencies and trends. These involve feedbacks between the atmosphere, biota, soils and landforms, mediated by water flow and transport processes. The human factor is becoming a key component of this coupled system. While there is a long tradition of considering effects of water on humans, and vice versa, the new thrust on socio-hydrology has a number of defining characteristics that sets it apart from traditional approaches: - Capturing feedbacks of human-natural water system in a dynamic way (slow and fast processes) to go beyond prescribing human factors as mere boundary conditions. These feedbacks will be essential to understand how the system may evolve in the future into new, perhaps previously unobserved, states. - Quantifying system dynamics in a generalizable way. So far, water resources assessment has been context dependent, tied to local conditions. While for immediate decision making this is undoubtedly essential, for more scientific inquiry, a more uniform knowledge base is indispensable. - Not necessarily predictive. The coupled human-nature system is inherently non-linear, which may prohibit predictability in the traditional sense. The socio-hydrologic approach may still be predictive in a statistical sense and, perhaps even more importantly, it may yet reveal

  12. The tungsten isotopic composition of Eoarchean rocks: Implications for early silicate differentiation and core-mantle interaction on Earth

    Science.gov (United States)

    Iizuka, Tsuyoshi; Nakai, Shun'ichi; Sahoo, Yu Vin; Takamasa, Asako; Hirata, Takafumi; Maruyama, Shigenori

    2010-03-01

    We have measured 182W/ 184W for Eoarchean rocks from the Itsaq Gneiss Complex (3.8-3.7 Ga pillow meta-basalts, a meta-tonalite, and meta-sediments) and Acasta Gneiss Complex (4.0-3.6 Ga felsic orthogneisses) to assess possible W isotopic heterogeneity within the silicate Earth and to constrain W isotopic evolution of the mantle. The data reveal that 182W/ 184W values in the Eoarchean samples are uniform within the analytical error and indistinguishable from the modern accessible mantle signature, suggesting that the W isotopic composition of the upper mantle has not changed significantly since the Eoarchean era. The results imply either that chemical communication between the mantle and core has been insignificant in post-Hadean times, or that a lowermost mantle with a distinctive W isotope signature has been isolated from mantle convective cycling. Most terrestrial rock samples have a 0.2 ɛ142Nd/ 144Nd higher than the chondrite average. This requires either the presence of a hidden enriched reservoir formed within the first 30 Ma of the Solar System, or the bulk Earth having a ˜ 5% higher Sm/Nd than the chondrite average. We explored the relevance of the 182Hf- 182W isotope system to the 146Sm- 142Nd isotope system during early silicate differentiation events on Earth. In this context, we demonstrate that the lack of resolvable 182W excesses in the Itsaq rocks, despite 142Nd excesses compared to the modern accessible mantle, is more consistent with the view that the bulk Earth has a non-chondritic Sm/Nd. In the non-chondritic Sm/Nd Earth model, the 182W- 142Nd chronometry constrains the age of the source mantle depletion for the Itsaq samples to more than ˜ 40 Ma after the Solar System origin. Our results cannot confirm the previous report of 182W anomalies in the Eoarchean Itsaq meta-sediments, which were interpreted as reflecting an impact-derived meteoritic component.

  13. Plate tectonics on the early Earth: Limitations imposed by strength and buoyancy of subducted lithosphere

    Science.gov (United States)

    van Hunen, Jeroen; van den Berg, Arie P.

    2008-06-01

    The tectonic style and viability of modern plate tectonics in the early Earth is still debated. Field observations and theoretical arguments both in favor and against the uniformitarian view of plate tectonics back until the Archean continue to accumulate. Here, we present the first numerical modeling results that address for a hotter Earth the viability of subduction, one of the main requirements for plate tectonics. A hotter mantle has mainly two effects: 1) viscosity is lower, and 2) more melt is produced, which in a plate tectonic setting will lead to a thicker oceanic crust and harzburgite layer. Although compositional buoyancy resulting from these thick crust and harzburgite might be a serious limitation for subduction initiation, our modeling results show that eclogitization significantly relaxes this limitation for a developed, ongoing subduction process. Furthermore, the lower viscosity leads to more frequent slab breakoff, and sometimes to crustal separation from the mantle lithosphere. Unlike earlier propositions, not compositional buoyancy considerations, but this lithospheric weakness could be the principle limitation to the viability of plate tectonics in a hotter Earth. These results suggest a new explanation for the absence of ultrahigh-pressure metamorphism (UHPM) and blueschists in most of the Precambrian: early slabs were not too buoyant, but too weak to provide a mechanism for UHPM and exhumation.

  14. Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth.

    Science.gov (United States)

    Cooper, G; Kimmich, N; Belisle, W; Sarinana, J; Brabham, K; Garrel, L

    The much-studied Murchison meteorite is generally used as the standard reference for organic compounds in extraterrestrial material. Amino acids and other organic compounds important in contemporary biochemistry are thought to have been delivered to the early Earth by asteroids and comets, where they may have played a role in the origin of life. Polyhydroxylated compounds (polyols) such as sugars, sugar alcohols and sugar acids are vital to all known lifeforms-they are components of nucleic acids (RNA, DNA), cell membranes and also act as energy sources. But there has hitherto been no conclusive evidence for the existence of polyols in meteorites, leaving a gap in our understanding of the origins of biologically important organic compounds on Earth. Here we report that a variety of polyols are present in, and indigenous to, the Murchison and Murray meteorites in amounts comparable to amino acids. Analyses of water extracts indicate that extraterrestrial processes including photolysis and formaldehyde chemistry could account for the observed compounds. We conclude from this that polyols were present on the early Earth and therefore at least available for incorporation into the first forms of life.

  15. Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth

    Science.gov (United States)

    Cooper, G.; Kimmich, N.; Belisle, W.; Sarinana, J.; Brabham, K.; Garrel, L.

    2001-01-01

    The much-studied Murchison meteorite is generally used as the standard reference for organic compounds in extraterrestrial material. Amino acids and other organic compounds important in contemporary biochemistry are thought to have been delivered to the early Earth by asteroids and comets, where they may have played a role in the origin of life. Polyhydroxylated compounds (polyols) such as sugars, sugar alcohols and sugar acids are vital to all known lifeforms-they are components of nucleic acids (RNA, DNA), cell membranes and also act as energy sources. But there has hitherto been no conclusive evidence for the existence of polyols in meteorites, leaving a gap in our understanding of the origins of biologically important organic compounds on Earth. Here we report that a variety of polyols are present in, and indigenous to, the Murchison and Murray meteorites in amounts comparable to amino acids. Analyses of water extracts indicate that extraterrestrial processes including photolysis and formaldehyde chemistry could account for the observed compounds. We conclude from this that polyols were present on the early Earth and therefore at least available for incorporation into the first forms of life.

  16. Planetary Temperatures : Early Estimates, Lowell, and the Albedo of the Earth

    Science.gov (United States)

    Lorenz, Ralph

    2016-10-01

    While it was recognized by Huygens, as soon as the architecture of the solar system was understood, that outer planets would be much cooler than Earth, quantitative estimation of planetary temperatures only became possible with understanding of radiant heat, and specifically the Stefan law relating heat flux to the fourth power of absolute temperature. This relation appears to have been first applied to planetary temperatures by the Danish physicist Christiansen in 1885, and he derived results for Mars and Saturn of -40 and -180C, rather reasonable values. However, the separate values of the solar constant, absolute planetary albedos (including that of the Earth) and the short- and long-wave transparency of planetary atmospheres were not known, although mountaintop measurements by Langley made some first steps to quantifying these effects. Lowell recognized that the Martian atmosphere was thinner than ours, but had more carbon dioxide, and so considered these factors to cancel out. However, he suggested that the Earth had a reflectivity of some 75%, such that darker Mars would absorb a larger fraction of incident sunlight than the Earth, compensating for Mars' greater distance from the sun and thus allowing clement temperatures. It is difficult not to see this as pushing the numbers to obtain a desired result, and indeed a robust refutation of his calculations swiftly followed by Poynting and Alfred Russel Wallace. I present a brief review of these early days of planetary climate modeling.

  17. Heat flow evolution of the Earth from paleomantle temperatures: Evidence for increasing heat loss since ∼2.5 Ga

    Science.gov (United States)

    Ruiz, Javier

    2017-08-01

    Earth currently loses two to five times as much heat through its surface as it is internally produced by radioactivity. This proportion cannot be extrapolated into the past, because it would imply high interior temperatures and catastrophic melting of the planet in ancient times. The heat loss evolution of the Earth cannot therefore be described by a constant heat flow decreasing. This is consistent with previous work finding that the mantle heated up until ∼2.5-3.0 Ga and then progressively cooled down. The present work derives a first-order heat loss evolution of the Earth by comparing the evolution of the total heat content of the silicate Earth (as described by mantle potential temperatures deduced from the melting conditions of ancient non-arc basalts) with the total radioactive heat production. The results show that the heat flow was declining, and the mantle heating-up, until ∼2.5 Ga, but that after this time the heat flow has been slowly (but constantly) increasing, and the mantle cooling-down, until the present-day. The change in heat loss trend is roughly coeval with other major geological, geochemical and environmental changes, and could indicate the starting of the modern-style of plate tectonics. This work provides therefore the first quantitative evidence of change in terrestrial heat loss regime, and suggests that substantial variations in the internal heat budget occurred during Earth's history.

  18. Early Earth melt production in a subduction zone, a petrological model

    Science.gov (United States)

    Magni, V.; Bouilhol, P.; Van Hunen, J.; Moyen, J.

    2013-12-01

    A large part of the Archean continental crust is made of a composite rock assemblage dominated by granitoids belonging to the TTG series (tonalite-trondhejmeite-granodiorite). The modus operandi of this sodic granitoids still disputed. If the modern processes leading to continental crust formation at convergent margins are well constrained, the extrapolation to early Earth conditions is hazardous, because the composition of Earth's early crust can be achieved through several processes. However, an 'arc' signature seems to be present in TTGs, suggesting a formation of continental crust in subduction zone settings. Moreover, they show strong similarities with modern adakites, which are thought to be formed by melting of the oceanic subducting crust. We present the results of a study where numerical models of subduction are integrated with a thermodynamic database. Our goal is to investigate under which conditions slab melting can be achieved if at all. We particularly focus our attention on the fate of water, since it is a component that is essential to the formation of TTG series, independently of the petrogenetical scenario preferred. The amount and composition of water bearing fluids in a subduction zone is controlled by slab devolatilization, and influence both the melting regime and the melt composition. Our reference model of an early Earth regime, with a high mantle potential temperature, show that the slab dehydrates early, ending up being composed of a dry eclogites. Importantly, our models show that dehydration melting is not achieved in the slab crust; yet, water-present melting of the 'dry' eclogites can be achieved if a dehydration reaction occurs in the deeper portion of the slab, fuelling the melting reaction with water. Moreover, the dehydration reactions that occurred within the slab are able to metasomatize the overlying mantle wedge, forming hydrated peridotites, that becomes a melt source when dragged down by corner-flow. Our results show the

  19. Lipid biomarker production and preservation in acidic ecosystems: Relevance to early Earth and Mars

    Science.gov (United States)

    Jahnke, L. L.; Parenteau, M. N.; Harris, R.; Bristow, T.; Farmer, J. D.; Des Marais, D. J.

    2013-12-01

    Compared to relatively benign carbonate buffered marine environments, terrestrial Archean and Paleoproterozoic life was forced to cope with a broader range of pH values. In particular, acidic terrestrial ecosystems arose from the oxidation of reduced species in hydrothermal settings and crustal reservoirs of metal sulfides, creating acid sulfate conditions. While oxidation of reduced species is facilitated by reactions with molecular oxygen, acidic conditions also arose in Archean hydrothermal systems before the rise of oxygen (Van Kranendonk, 2006), expanding the range of time over which acidophiles could have existed on the early Earth. Acidic terrestrial habitats would have included acidic hydrothermal springs, acid sulfate soils, and possibly lakes and streams lacking substantial buffering capacity with sources of acidity in their catchments. Although acidic hot springs are considered extreme environments on Earth, robust and diverse microbial communities thrive in these habitats. Such acidophiles are found across all three domains of life and include both phototrophic and chemotrophic members. In this presentation, we examine hopanes and sterols that are characteristic of microbial communities living in acidic hydrothermal environments. Moreover we discuss taphonomic processes governing the capture and preservation of these biosignatures in acid environments. In particular, we discuss the production and early preservation of hopanoids and sterols in the following geological/mineralogical settings: 1) rapid entombment of microbes and organic matter by predominantly fine-grained silica; 2) rapid burial of organic matter by clay-rich, silica poor sediments; 3) and the survival of organics in iron oxide and sulfate rich sediments. We discovered and isolated an acid-tolerant purple non-sulfur anoxygenic phototroph from Lassen Volcanic National Park that synthesizes 3methyl-bacteriohopanepolyols. These compounds were previously thought to be exclusively made by

  20. Evolution of the Oxidation State of the Earth's Mantle: Challenges of High Pressure Quenching

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Keller, L. P.; Rahman, Z.

    2015-12-01

    The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion [1], transitioned from reduced to oxidized [2,3,4], or from oxidized to reduced [1,5]. We investigate the stability of Fe3+ at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. Experiments of more mafic compositions and at higher pressures commonly form a polyphase quench intergrowth composed primarily of pyroxenes, with interstitial glass which hosts nearly all of the more volatile minor elements. In our previous experiments on shergottite compositions, variable fO2, T, and P <4 GPa, Fe3+/ΣFe decreased slightly with increasing P, similar to terrestrial basalt [6,7,8]. For oxidizing experiments < 7GPa, Fe3+/ΣFe decreased as well [9], but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3+ [1,10]. Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Experiments with Knippa basalt as the starting composition were conducted at 1-8 GPa and 1800 °C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products from 7-8 GPa quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal Fe3+/2+. A number of different approaches have been employed to produce glassy samples that can be measured by EELS and XANES. A more intermediate andesite was used in one experiment, and decompression during quenching was attempted after [11], but both resulted in a finer grained polyphase texture. Experiments are currently underway to test how different capsule materials may affect quench texture. A preliminary experiment using liquid nitrogen to greatly enhance the rate of cooling of the assembly has also been attempted and

  1. Kingian Co-Evolution of the Water and Mineral/Rock Components for Earth and Mars: Implications for Planetary Habitability (Invited)

    Science.gov (United States)

    Baker, V. R.

    2013-12-01

    Planetary habitability may fluctuate episodically against a background provided by the co-evolution of a planet's mineral/rock (geosphere) components and its water (hydrosphere) in relation to its position in a circumstellar system. The water/rock (geosphere/hydrosphere) co-evolution can be inferred from the geological histories of the terrestrial planets of the solar system, particularly from the very extensive understanding of Earth and Mars. Habitability and water/rock co-evolution have components that are tychistic (i.e., driven by chance) and anancastic (i.e., dynamically driven largely by deterministic forces). They also have a final, end-directed (i.e., teleomatic) aspect that operates in accordance with natural laws. This is a larger perspective on the idea of planetary habitability than is generally associated with an astronomical approach, and it incorporates additional insights from a geological perspective on the issue. The geological histories of Mars and Earth are punctuated with critical, short-term epochs of extreme change, which for Earth are known to be associated with major disruptions of its biosphere. These catastrophic epochs can be described as a type of non-Darwinian evolution that was envisioned by the geologist Clarence King. In an 1877 paper King proposed that accelerated evolutionary change occurs during sudden environmental disruptions. Such Kingian disruptions in mineral/rock and water evolution mark the planetary histories of Mars and Earth, including the early formation and condensation of a steam atmosphere, an impacting cataclysm at about 3.9 to 4 Ga, episodes of concentrated volcanism and tectonism, and associated rapid changes in the linked atmosphere and hydrosphere. These disruptions are closely tied to migrations of water between different planetary reservoirs, the nature of planetary accretion, the origin of a physically coupled atmosphere and ocean, the prospects for initiating plate tectonics, and punctuated greenhouse

  2. Past Plate Motions and The Evolution of Earth's Lower Mantle: Relating LLSVPs and Plume Distribution

    Science.gov (United States)

    Bull, A. L.; Torsvik, T. H.; Shephard, G. E.

    2015-12-01

    Seismic tomography elucidates broad, low shear-wave velocity structures in the lower mantle beneath Africa and the central Pacific with uncertain physical and compositional origins. The anomalously slow areas, which cover nearly 50% of the core-mantle boundary, are often referred to as Large Low Shear Velocity Provinces (LLSVPs) due to the reduced velocity of seismic waves passing through them. Several hypotheses have arisen to explain the LLSVPs in the context of large-scale mantle convection. One end-member scenario infers a spatial correlation between LLSVP margins at depth and the reconstructed surface eruption sites of hotspots, kimberlites, and Large Igneous Provinces. Such a correlation has been explained by the preferential triggering of plumes at LLSVP margins by impingement of the subducting lithosphere upon the lower thermal boundary layer at the interface between ambient mantle and the higher density structures. This scenario propounds that Earth's plate motion history plays a controlling role in plume development, and that the location, geometry and morphology of plumes may be influenced by the movement of subducting slabs. Here, we investigate what is necessary to create such a pattern of plume distribution in relation to LLSVPs. We consider what effect past plate motions may have had on the evolution of Earth's lower mantle, and discuss the development of mantle plumes in terms of subduction dynamics. We integrate plate tectonic histories and numerical models of mantle convection to investigate the role that subduction history plays in the development and evolution of plumes in the presence of LLSVPs. To test whether an interaction exists between the surface location of subduction and plume eruption sites, and if so, to what degree over time, we apply varying shifts to the absolute reference frame of the plate reconstruction. With this method, we are able to change the location of subduction at the surface and thus the global flow field. This in turn

  3. A review of noble gas geochemistry in relation to early Earth history

    Science.gov (United States)

    Kurz, M. D.

    1985-01-01

    One of the most fundamental noble gas constraints on early Earth history is derived from isotopic differences in (129)Xe/(130)Xe between various terrestrial materials. The short half life (17 m.y.) of extinct (129I, parent of (129)Xe, means that these differences must have been produced within the first 100 m.y. after terrestrial accretion. The identification of large anomalies in (129)Xe/(130)Xe in mid ocean ridge basalts (MORB), with respect to atmospheric xenon, suggests that the atmosphere and upper mantle have remained separate since that time. This alone is a very strong argument for early catastrophic degassing, which would be consistent with an early fractionation resulting in core formation. However, noble gas isotopic systematics of oceanic basalts show that the mantle cannot necessarily be regarded as a homogeneous system, since there are significant variations in (3)He/(4)He, (40)Ar/(36)Ar, and (129)Xe/(130)Xe. Therefore, the early degassing cannot be considered to have acted on the whole mantle. The specific mechanisms of degassing, in particular the thickness and growth of the early crust, is an important variable in understanding present day noble gas inventories. Another constraint can be obtained from rocks that are thought to be derived from near the lithosphere asthenosphere boundary: ultramafic xenoliths.

  4. Early evolution of the LIM homeobox gene family

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Mansi; Larroux, Claire; Lu, Daniel R; Mohanty, Kareshma; Chapman, Jarrod; Degnan, Bernard M; Rokhsar, Daniel S

    2010-01-01

    LIM homeobox (Lhx) transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known. We identified Lhx genes in two cnidarians and a placozoan and report the expression of Lhx genes during embryonic development in Nematostella and the demosponge Amphimedon. Members of the six major LIM homeobox subfamilies are represented in the genomes of the starlet sea anemone, Nematostella vectensis, and the placozoan Trichoplax adhaerens. The hydrozoan cnidarian, Hydra magnipapillata, has retained four of the six Lhx subfamilies, but apparently lost two others. Only three subfamilies are represented in the haplosclerid demosponge Amphimedon queenslandica. A tandem cluster of three Lhx genes of different subfamilies and a gene containing two LIM domains in the genome of T. adhaerens (an animal without any neurons) indicates that Lhx subfamilies were generated by tandem duplication. This tandem cluster in Trichoplax is likely a remnant of the original chromosomal context in which Lhx subfamilies first appeared. Three of the six Trichoplax Lhx genes are expressed in animals in laboratory culture, as are all Lhx genes in Hydra. Expression patterns of Nematostella Lhx genes correlate with neural territories in larval and juvenile polyp stages. In the aneural demosponge, A. queenslandica, the three Lhx genes are expressed widely during development, including in cells that are associated with the larval photosensory ring. The Lhx family expanded and diversified early in animal evolution, with all six subfamilies already diverged prior to the cnidarian-placozoan-bilaterian last common ancestor. In Nematostella, Lhx gene expression is correlated with neural

  5. Early evolution of the LIM homeobox gene family

    Directory of Open Access Journals (Sweden)

    Degnan Bernard M

    2010-01-01

    Full Text Available Abstract Background LIM homeobox (Lhx transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known. Results We identified Lhx genes in two cnidarians and a placozoan and report the expression of Lhx genes during embryonic development in Nematostella and the demosponge Amphimedon. Members of the six major LIM homeobox subfamilies are represented in the genomes of the starlet sea anemone, Nematostella vectensis, and the placozoan Trichoplax adhaerens. The hydrozoan cnidarian, Hydra magnipapillata, has retained four of the six Lhx subfamilies, but apparently lost two others. Only three subfamilies are represented in the haplosclerid demosponge Amphimedon queenslandica. A tandem cluster of three Lhx genes of different subfamilies and a gene containing two LIM domains in the genome of T. adhaerens (an animal without any neurons indicates that Lhx subfamilies were generated by tandem duplication. This tandem cluster in Trichoplax is likely a remnant of the original chromosomal context in which Lhx subfamilies first appeared. Three of the six Trichoplax Lhx genes are expressed in animals in laboratory culture, as are all Lhx genes in Hydra. Expression patterns of Nematostella Lhx genes correlate with neural territories in larval and juvenile polyp stages. In the aneural demosponge, A. queenslandica, the three Lhx genes are expressed widely during development, including in cells that are associated with the larval photosensory ring. Conclusions The Lhx family expanded and diversified early in animal evolution, with all six subfamilies already diverged prior to the cnidarian-placozoan-bilaterian last common ancestor. In

  6. Life might be rare despite its early emergence on Earth: a Bayesian analysis of the probability of abiogenesis

    CERN Document Server

    Spiegel, David S

    2011-01-01

    Life arose on Earth sometime in the first few hundred million years after the young planet had cooled to the point that it could support water-based organisms on its surface. The early emergence of life on Earth has been taken as evidence that the probability of abiogenesis is high, if starting from young-Earth-like conditions. We revisit this argument quantitatively in a Bayesian statistical framework. By constructing a simple model of the probability of abiogenesis, we calculate a Bayesian estimate of its posterior probability, given the data that life emerged fairly early in Earth's history and that, billions of years later, sentient creatures noted this fact and considered its implications. We find that, given only this very limited empirical information, the choice of Bayesian prior for the abiogenesis probability parameter has a dominant influence on the computed posterior probability. Thus, although life began on this planet fairly soon after the Earth became habitable, this fact is consistent with an ...

  7. Early human communication helps in understanding language evolution.

    Science.gov (United States)

    Lenti Boero, Daniela

    2014-12-01

    Building a theory on extant species, as Ackermann et al. do, is a useful contribution to the field of language evolution. Here, I add another living model that might be of interest: human language ontogeny in the first year of life. A better knowledge of this phase might help in understanding two more topics among the "several building blocks of a comprehensive theory of the evolution of spoken language" indicated in their conclusion by Ackermann et al., that is, the foundation of the co-evolution of linguistic motor skills with the auditory skills underlying speech perception, and the possible phylogenetic interactions of protospeech production with referential capabilities.

  8. Geodynamic evolution of the Earth over the Phanerozoic: Plate tectonic activity and palaeoclimatic indicators

    Directory of Open Access Journals (Sweden)

    Christian Vérard

    2015-04-01

    In this paper, we compare values derived from the tectonic model (ages of oceanic floor, production and subduction rates, tectonic activity with a combination of chemical proxies (namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations known to be strongly influenced by tectonics. One of the outstanding results is the observation of an overall decreasing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend reflects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations confirms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-floor production rates are in contradiction with the steady-state model hypothesized by some.

  9. Thermal evolution and interior models of the transiting super-Earth GJ 1214b

    CERN Document Server

    Nettelmann, N; Kramm, U; Redmer, R

    2010-01-01

    The planet GJ 1214b is the second known super-Earth with a measured mass and radius. Orbiting a quiet M-star, it receives considerably less mass-loss driving X-ray and UV radiation than CoRoT-7b, so that the interior may be quite dissimilar in composition, including the possibility of a large fraction of water. We model the interior of GJ 1214b assuming a two-layer (envelope+rock core) structure where the envelope material is either H/He, pure water, or a mixture of H/He and H2O. Within this framework we perform models of the thermal evolution and contraction of the planet. We discuss possible compositions that are consistent with Mp=6.55 ME, Rp=2.678 RE, an age tau=3-10 Gyr, and the irradiation level of the atmosphere. These conditions require that if water exists in the interior, it must remain in a fluid state, with important consequences for magnetic field generation. These conditions also require the atmosphere to have a deep isothermal region extending down to 80-800 bar, depending on composition. Our r...

  10. Geodynamic evolution of the Earth over the Phanerozoic:Plate tectonic activity and palaeoclimatic indicators

    Institute of Scientific and Technical Information of China (English)

    Christian Vérard; Cyril Hochard; Peter O. Baumgartner; Gérard M. Stamplfi

    2015-01-01

    During the last decades, numerous local reconstructions based on ifeld geol-ogy were developed at the University of Lausanne (UNIL). Team members of the UNIL partici-pated in the elaboration of a 600 Ma to present global plate tectonic model deeply rooted in geological data, controlled by geometric and kinematic constraints and coherent with forces acting at plate boundaries. In this paper, we compare values derived from the tectonic model (ages of oceanic lfoor, production and subduction rates, tectonic activity) with a combination of chemical proxies (namely CO2, 87Sr/86Sr, glaciation evidence, and sea-level variations) known to be strongly in-lfuenced by tectonics. One of the outstanding results is the observation of an overall decreas-ing trend in the evolution of the global tectonic activity, mean oceanic ages and plate velocities over the whole Phanerozoic. We speculate that the decreasing trend relfects the global cooling of the Earth system. Additionally, the parallel between the tectonic activity and CO2 together with the extension of glaciations conifrms the generally accepted idea of a primary control of CO2 on climate and highlights the link between plate tectonics and CO2 in a time scale greater than 107 yr. Last, the wide variations observed in the reconstructed sea-lfoor production rates are in contradiction with the steady-state model hypothesized by some.

  11. Deep Reaching Gas-permeable Tectonic Faults of the Early Earth as Habitats for the Origin of Life

    Science.gov (United States)

    Schreiber, U.; Mayer, C.

    2012-04-01

    The discussion on the origin of life encounters difficulties when it comes to estimate the conditions of the early earth and to define plausible environments for the development of the first complex organic molecules. Until now, the role of the earth's crust has been more or less ignored. First continental crustal cores may have been developed some tens to hundreds of million years after formation of earth. Due to tectonic stress the proto continents were sheared by vertical strike-slip faults at an early stage. These deep-reaching open, interconnected tectonic faults may provide possible reaction habitats ranging from nano- to centimetre and even larger dimensions that sum up to several cubic kilometres for the formation of prebiotic molecules. Their fillings consist of supercritical and subcritical waters and supercritical and subcritical gases. Here, all necessary raw materials including phosphate for the development of prebiotic molecules exist in variable concentrations and in sufficient quantities. Furthermore, there are periodically changing pressure and temperature conditions, varying pH-values, metallic surfaces, clay minerals and a large number of catalysts. While cosmic and UV-radiation are excluded, nuclear radiation intervenes the chemical evolution of the molecules inside the crust. Carbon dioxide (CO2) is of crucial importance. It can be present in an almost pure form as a supercritical fluid (scCO2) in a crustal depth less than 1 km (critical point of pure CO2: 74 bar; 31°C). Inside strike-slip faults, a two-phase system formed by supercritical CO2 in liquid water provides the environment for condensation and polymerisation of hydrogen cyanide, nucleobases, nucleotides and amino acids. ScCO2 is a non-polar solvent that is widely used in "green chemistry" (Anastas and Kirchhoff 2002) and enables the dissolution of non-polar reactants and their reactions normally occurring in the absence of water. Under the influence of periodically changing

  12. Looking Backwards in Time to the Early Earth Using the Lens of Stable Isotope Geodynamic Cycles

    Science.gov (United States)

    Gregory, R. T.

    2016-12-01

    The stable isotope ratios of hydrogen, carbon, oxygen and sulfur provide of means of tracing interactions between the major reservoirs of the Earth. The oceans and the dichotomy between continental and oceanic crust are key differences between the Earth and other terrestrial bodies. The existence of plate tectonics and the recognition that no primary crust survives at the Earth's surface sets this planet apart from the smaller terrestrial bodies. The thermostatic control of carbonate-silicate cycle works because of the hydrosphere and plate tectonics. Additionally, the contrast between the carbon isotope ratios for reduced and oxidized species appear to also be invariant over geologic time with evidence of old recycled carbon in the form of diamond inclusions in mantle-derived igneous rocks. Lessons from comparative planetology suggest that early differentiation of the Earth would have likely resulted in the rapid formation of the oceans, a water world over the primary crust. Plate tectonics provides a mechanism for buffering the oxygen isotope fractionation between the oceans and the mantle. The set point for hydrosphere's oxygen isotope composition is a result of the geometry of mid-ocean ridge accretion that is stable over an order magnitude change in spreading rates with time constants much younger shorter than the age of the Earth. The recognition that the "normal" ranges for hydrogen isotope ratios of igneous, metamorphic and sedimentary rocks of any age generally overlap with similar ranges, with the exception of rocks that have interacted with D- and 18O-depleted meteoric waters (generally at high latitudes), is an argument for a constant volume ocean over geologic time. Plate tectonics with a constant volume ocean constrains the thickness of the continental crust because of the rapidity of the mechanical weathering cycle (characteristic times of 10's of millions of years; freeboard of the continents argument). In a plate tectonic regime, chemical

  13. Electrochemical studies of iron meteorites: phosphorus redox chemistry on the early Earth

    Science.gov (United States)

    Bryant, David E.; Greenfield, David; Walshaw, Richard D.; Evans, Suzanne M.; Nimmo, Alexander E.; Smith, Caroline L.; Wang, Liming; Pasek, Matthew A.; Kee, Terence P.

    2009-01-01

    The mineral schreibersite, (Fe,Ni)3P, a ubiquitous component of iron meteorites, is known to undergo anoxic hydrolytic modification to afford a range of phosphorus oxyacids. H-phosphonic acid (H3PO3) is the principal hydrolytic product under hydrothermal conditions, as confirmed here by 31P-NMR spectroscopic studies on shavings of the Seymchan pallasite (Magadan, Russia, 1967), but in the presence of photochemical irradiation a more reduced derivative, H-phosphinic (H3PO2) acid, dominates. The significance of such lower oxidation state oxyacids of phosphorus to prebiotic chemistry upon the early Earth lies with the facts that such forms of phosphorus are considerably more soluble and chemically reactive than orthophosphate, the commonly found form of phosphorus on Earth, thus allowing nature a mechanism to circumvent the so-called Phosphate Problem. This paper describes the Galvanic corrosion of Fe3P, a hydrolytic modification pathway for schreibersite, leading again to H-phosphinic acid as the key P-containing product. We envisage this pathway to be highly significant within a meteoritic context as iron meteorites are polymetallic composites in which dissimilar metals, with different electrochemical potentials, are connected by an electrically conducting matrix. In the presence of a suitable electrolyte medium, i.e., salt water, galvanic corrosion can take place. In addition to model electrochemical studies, we also report the first application of the Kelvin technique to map surface potentials of a meteorite sample that allows the electrochemical differentiation of schreibersite inclusions within an Fe:Ni matrix. Such experiments, coupled with thermodynamic calculations, may allow us to better understand the chemical redox behaviour of meteoritic components with early Earth environments.

  14. Ultramafic Terranes and Associated Springs as Analogs for Mars and Early Earth

    Science.gov (United States)

    Blake, David; Schulte, Mitch; Cullings, Ken; DeVincezi, D. (Technical Monitor)

    2002-01-01

    Putative extinct or extant Martian organisms, like their terrestrial counterparts, must adopt metabolic strategies based on the environments in which they live. In order for organisms to derive metabolic energy from the natural environment (Martian or terrestrial), a state of thermodynamic disequilibrium must exist. The most widespread environment of chemical disequilibrium on present-day Earth results from the interaction of mafic rocks of the ocean crust with liquid water. Such environments were even more pervasive and important on the Archean Earth due to increased geothermal heat flow and the absence of widespread continental crust formation. The composition of the lower crust and upper mantle of the Earth is essentially the-same as that of Mars, and the early histories of these two planets are similar. It follows that a knowledge of the mineralogy, water-rock chemistry and microbial ecology of Earth's oceanic crust could be of great value in devising a search strategy for evidence of past or present life on Mars. In some tectonic regimes, cross-sections of lower oceanic crust and upper mantle are exposed on land as so-called "ophiolite suites." Such is the case in the state of California (USA) as a result of its location adjacent to active plate margins. These mafic and ultramafic rocks contain numerous springs that offer an easily accessible field laboratory for studying water/rock interactions and the microbial communities that are supported by the resulting geochemical energy. A preliminary screen of Archaean biodiversity was conducted in a cold spring located in a presently serpentinizing ultramafic terrane. PCR and phylogenetic analysis of partial 16s rRNA, sequences were performed on water and sediment samples. Archaea of recent phylogenetic origin were detected with sequences nearly identical to those of organisms living in ultra-high pH lakes of Africa.

  15. Chemo-dynamical deuterium fractionation in the early solar nebula: The origin of water on Earth and in asteroids and comets

    CERN Document Server

    Albertsson, T; Henning, Th

    2014-01-01

    Formation and evolution of water in the Solar System and the origin of water on Earth constitute one of the most interesting questions in astronomy. The prevailing hypothesis for the origin of water on Earth is by delivery through water-rich small Solar system bodies. In this paper, the isotopic and chemical evolution of water during the early history of the solar nebula, before the onset of planetesimal formation, is studied. A gas-grain chemical model that includes multiply-deuterated species and nuclear spin-states is combined with a steady-state solar nebula model. To calculate initial abundances, we simulated 1 Myr of evolution of a cold and dark TMC1-like prestellar core. Two time-dependent chemical models of the solar nebula are calculated over 1 Myr: (1) a laminar model and (2) a model with 2D turbulent mixing. We find that the radial outward increase of the H2O D/H ratio is shallower in the chemo-dynamical nebular model compared to the laminar model. This is related to more efficient de-fractionation...

  16. The split fate of the early Earth, Mars, Venus, and Moon

    Science.gov (United States)

    Albarède, Francis; Blichert-Toft, Janne

    2007-11-01

    Plate tectonics shaped the Earth, whereas the Moon is a dry and inactive desert, Mars probably came to rest within the first billion years of its history, and Venus, although internally very active, has a dry inferno for its surface. Here we review the parameters that determined the fates of each of these planets and their geochemical expressions. The strong gravity field of a large planet allows for an enormous amount of gravitational energy to be released, causing the outer part of the planetary body to melt (magma ocean), helps retain water on the planet, and increases the pressure gradient. The weak gravity field and anhydrous conditions prevailing on the Moon stabilized, on top of its magma ocean, a thick buoyant plagioclase lithosphere, which insulated the molten interior. On Earth, the buoyant hydrous phases (serpentines) produced by reactions between the terrestrial magma ocean and the wet impactors received from the outer solar system isolated the magma and kept it molten for some few tens of million years. The planets from the inner solar system accreted dry: foundering of wet surface material softened the terrestrial mantle and set the scene for the onset of plate tectonics. This very same process also may have removed all the water from the surface of Venus and added enough water to its mantle to make its internal dynamics very strong and keep the surface very young. Because of a radius smaller than that of the Earth, not enough water could be drawn into the Martian mantle before it was lost to space and Martian plate tectonics never began. The radius of a planet is therefore the key parameter controlling most of its evolutional features.

  17. Terrestrial production vs. extraterrestrial delivery of prebiotic organics to the early Earth

    Science.gov (United States)

    Chyba, C. F.; Sagan, C.; Thomas, P. J.; Brookshaw, L.

    1991-01-01

    A comprehensive treatment of comet/asteroid interaction with the atmosphere, ensuring surface impact, and resulting organic pyrolysis is required to determine whether more than a negligible fraction of the organics in incident comets and asteroids actually survived collision with Earth. Results of such an investigation, using a smoothed particle hydrodynamic simulation of cometary and asteroidal impacts into both oceans and rock, demonstrate that organics will not survive impacts at velocities approx. greater than 10 km s(exp -1), and that even comets and asteroids as small as 100m in radius cannot be aerobraked to below this velocity in 1 bar atmospheres. However, for plausible dense (10 bar CO2) early atmospheres, there will be sufficient aerobraking during atmospheric passage for some organics to survive the ensuing impact. Combining these results with analytical fits to the lunar impact record shows that 4.5 Gyr ago Earth was accreting at least approx. 10(exp 6) kg yr(exp 1) of intact cometary organics, a flux which thereafter declined with a approx. 100 Myr half-life. The extent to which this influx was augmented by asteroid impacts, as well as the effect of more careful modelling of a variety of conservative approximations, is currently being quantified. These results may be placed in context by comparison with in situ organic production from a variety of terrestrial energy sources, as well as organic delivery by interplanetary dust. Which source dominated the early terrestrial prebiotic inventory is found to depend on the nature of the early terrestrial atmosphere. However, there is an intriguing symmetry: it is exactly those dense CO2 atmospheres where in situ atmospheric production of organic molecules should be the most difficult, in which intact cometary organics would be delivered in large amounts.

  18. Plate tectonics: Crustal recycling evolution

    Science.gov (United States)

    Magni, Valentina

    2017-09-01

    The processes that form and recycle continental crust have changed through time. Numerical models reveal an evolution from extensive recycling on early Earth as the lower crust peeled away, to limited recycling via slab break-off today.

  19. Precambrian supercontinents, glaciations, atmospheric oxygenation, metazoan evolution and an impact that may have changed the second half of Earth history

    OpenAIRE

    Grant M. Young

    2013-01-01

    In more than 4 Ga of geological evolution, the Earth has twice gone through extreme climatic perturbations, when extensive glaciations occurred, together with alternating warm periods which were accompanied by atmospheric oxygenation. The younger of these two episodes of climatic oscillation preceded the Cambrian “explosion” of metazoan life forms, but similar extreme climatic conditions existed between about 2.4 and 2.2 Ga. Over long time periods, changing solar luminosity and mantle tempera...

  20. Biogeochemical Signatures in Precambrian Black Shales: Window Into the Co-Evolution of Ocean Chemistry and Life on Earth

    OpenAIRE

    Scott, Clinton

    2009-01-01

    The degradation of sedimentary organic matter drives a suite of biologically- mediated redox reactions that in turn reflect the chemical composition of pore waters and bottom waters on local to global scales. By analyzing the chemical and isotopic composition of modern sediments and ancient black shales, biogeochemists can track the evolution of ocean/atmosphere redox conditions, the chemical composition of the oceans, and the evolutionary course of life throughout Earth history. Chapter 1 in...

  1. The Evolution of the National Early Childhood Technical Assistance Center

    Science.gov (United States)

    Gallagher, James J.; Danaher, Joan C.; Clifford, Richard M.

    2009-01-01

    This review traces the evolution from 1971 to the present of a national technical assistance (TA) program to support the creation, expansion, and improvement of services for infants, toddlers, and preschoolers with special needs. From its beginning as a TA resource for demonstration projects, to linking outreach projects' expertise with state…

  2. Investigating the Early Atmospheres of Earth and Mars through Rivers, Raindrops, and Lava Flows

    Science.gov (United States)

    Som, Sanjoy M.

    2010-11-01

    The discovery of a habitable Earth-like planet beyond our solar-system will be remembered as one of the major breakthroughs of 21st century science, and of the same magnitude as Copernicus' heliocentric model dating from the mid 16th century. The real astrobiological breakthrough will be the added results from atmospheric remote sensing of such planets to determine habitability. Atmospheres, in both concentration and composition are suggestive of processes occurring at the planetary surface and upper crust. Unfortunately, only the modern Earth's atmosphere is known to be habitable. I investigate the density and pressure of our planet's early atmosphere before the rise of oxygen 2.5 billion years ago, because our planet was very much alive microbially. Such knowledge gives us another example of a habitable atmosphere. I also investigates the atmosphere of early Mars, as geomorphic signatures on its surface are suggestive of a past where liquid water may have present in a warmer climate, conditions suitable for the emergence of life, compared with today's 6 mbar CO2-dominated atmosphere. Using tools of fluvial geomorphology, I find that the largest river-valleys on Mars do not record a signature of a sustained hydrological cycle, in which precipitation onto a drainage basin induces many cycles of water flow, substrate incision, water ponding, and return to the atmosphere via evaporation. Rather, I conclude that while episodes of flow did occur in perhaps warmer environments, those periods were short-lived and overprinted onto a dominantly cold and dry planet. For Earth, I develop a new method of investigating atmospheric density and pressure using the size of raindrop imprints, and find that raindrop imprints preserved in the 2.7 billion year old Ventersdorp Supergroup of South Africa are consistent with precipitation falling in an atmosphere of near-surface density 0.1 kg/m3, compared to a modern value of 1.2 kg/m3, further suggesting a nitrogen level of at most

  3. On the chronology of lunar origin and evolution. Implications for Earth, Mars and the Solar System as a whole

    Science.gov (United States)

    Geiss, Johannes; Rossi, Angelo Pio

    2013-11-01

    An origin of the Moon by a Giant Impact is presently the most widely accepted theory of lunar origin. It is consistent with the major lunar observations: its exceptionally large size relative to the host planet, the high angular momentum of the Earth-Moon system, the extreme depletion of volatile elements, and the delayed accretion, quickly followed by the formation of a global crust and mantle. According to this theory, an impact on Earth of a Mars-sized body set the initial conditions for the formation and evolution of the Moon. The impact produced a protolunar cloud. Fast accretion of the Moon from the dense cloud ensured an effective transformation of gravitational energy into heat and widespread melting. A "Magma Ocean" of global dimensions formed, and upon cooling, an anorthositic crust and a mafic mantle were created by gravitational separation. Several 100 million years after lunar accretion, long-lived isotopes of K, U and Th had produced enough additional heat for inducing partial melting in the mantle; lava extruded into large basins and solidified as titanium-rich mare basalt. This delayed era of extrusive rock formation began about 3.9 Ga ago and may have lasted nearly 3 Ga. A relative crater count timescale was established and calibrated by radiometric dating (i.e., dating by use of radioactive decay) of rocks returned from six Apollo landing regions and three Luna landing spots. Fairly well calibrated are the periods ≈4 Ga to ≈3 Ga BP (before present) and ≈0.8 Ga BP to the present. Crater counting and orbital chemistry (derived from remote sensing in spectral domains ranging from γ- and x-rays to the infrared) have identified mare basalt surfaces in the Oceanus Procellarum that appear to be nearly as young as 1 Ga. Samples returned from this area are needed for narrowing the gap of 2 Ga in the calibrated timescale. The lunar timescale is not only used for reconstructing lunar evolution, but it serves also as a standard for chronologies of the

  4. Early Cretaceous mammal from North America and the evolution of marsupial dental characters.

    OpenAIRE

    1993-01-01

    A mammal from the Early Cretaceous of the western United States, represented by a lower jaw exceptional in its completeness, presents unambiguous evidence of postcanine dental formula in an Early Cretaceous marsupial-like mammal, and prompts a reconsideration of the early evolution of marsupial dental characters. A marsupial postcanine dental formula (three premolars and four molars) and several marsupial-like features of the lower molars are present in the new taxon, but a hallmark specializ...

  5. Extent of metal-silicate disequilibrium during accretion and early differentiation of the Earth

    Science.gov (United States)

    Rubie, D. C.; Nimmo, F.; Morbidelli, A.; Frost, D. J.

    2012-12-01

    Earth, Mars, Venus and Mercury accreted on a timescale of 10-100 My through a series of violent collisions with planetesimals and embryos. The high energy of such impacts was sufficient to cause deep magma ocean formation which facilitated the segregation of metal and silicate liquids. Planetary cores thus formed as a multistage process that was inseparable from the accretion process. In order to better understand the formation and early differentiation of the terrestrial planets, we are integrating a multistage core-formation model with N-body accretion simulations. Constraints on model parameters are the compositions of the Earth's primitive mantle and, to a lesser extent, the mantles of Mars and Mercury which may be FeO rich and FeO-poor respectively. We use a least-squares minimization to optimise 4 model parameters. Elements currently considered include Si, O, Ni, Co, W, Nb, Cr, Ta and V. We concentrate on recent N-body simulations that result in an approximately Earth-mass planet at ~1 AU. In order to satisfy the model constraints, accretion has to be heterogeneous, with embryos and planetesimals originating in the inner part of the solar system (e.g. emulsify and equilibrate in a magma ocean and (2) the fraction of magma oceans that are involved in the equilibration process for both impacting planetesimals and embryos. Both estimates are crucial for interpreting Hf-W age determinations. Best results are obtained when the fraction of silicate mantle/magma ocean that interacts chemically with the metallic cores of impactors is limited and lies in the range 0.003 to 0.1, depending on the size of the impactor and magma ocean depth. The degree of incomplete metal equilibration depends on the extent to which the impactor's mantle participates in the metal-silicate equilibration process.

  6. Synthesis of glycine-containing complexes in impacts of comets on early Earth

    Science.gov (United States)

    Goldman, Nir; Reed, Evan J.; Fried, Laurence E.; William Kuo, I.-F.; Maiti, Amitesh

    2010-11-01

    Delivery of prebiotic compounds to early Earth from an impacting comet is thought to be an unlikely mechanism for the origins of life because of unfavourable chemical conditions on the planet and the high heat from impact. In contrast, we find that impact-induced shock compression of cometary ices followed by expansion to ambient conditions can produce complexes that resemble the amino acid glycine. Our ab initio molecular dynamics simulations show that shock waves drive the synthesis of transient C-N bonded oligomers at extreme pressures and temperatures. On post impact quenching to lower pressures, the oligomers break apart to form a metastable glycine-containing complex. We show that impact from cometary ice could possibly yield amino acids by a synthetic route independent of the pre-existing atmospheric conditions and materials on the planet.

  7. The Solubility of Rock in Steam Atmospheres of the Early Earth and Hot Rocky Exoplanets

    Science.gov (United States)

    Fegley, Bruce

    2016-07-01

    Extensive experimental studies show all major rock-forming elements (e.g., Si, Mg, Fe, Ca, Al, Na, K) dissolve in steam to a greater or lesser extent. We use these results to compute chemical equilibrium abundances of rocky element - bearing gases in steam atmospheres equilibrated with silicate magma oceans. Rocky elements partition into steam atmospheres as volatile hydroxide gases (e.g., Si(OH)4, Mg(OH)2, Fe(OH)2, Ni(OH)2, Al(OH)3, Ca(OH)2, NaOH, KOH) and via reaction with HF and HCl as volatile halide gases (e.g., NaCl, KCl, CaFOH, CaClOH, FAl(OH)2) in much larger amounts than expected from their vapor pressures over volatile-free solid or molten rock at high temperatures expected for steam atmospheres on the early Earth and hot rocky exoplanets. We quantitatively compute the extent of fractional vaporization by defining gas/magma distribution coefficients and show Earth's sub-solar Si/Mg ratio may be due to loss of a primordial steam atmosphere. We conclude hot rocky exoplanets that are undergoing or have undergone escape of steam-bearing atmospheres may experience fractional vaporization and loss of Si, Mg, Fe, Ni, Al, Ca, Na, and K. This loss can modify their bulk composition, density, heat balance, and interior structure. This work was supported by NSF Astronomy Program Grant AST-1412175.

  8. Differentiation of crusts and cores of the terrestrial planets - Lessons for the early earth

    Science.gov (United States)

    Solomon, S. C.

    1980-01-01

    The extent and mechanisms of global differentiation and the early thermal and tectonic histories of the terrestrial planets are surveyed in order to provide constraints on the first billion years of earth history. Indirect and direct seismic evidence for crusts on the moon, Mars and Venus is presented, and it is pointed out that substantial portions of these crusts have been in place since the cessation of heavy bombardment of the inner solar system four billion years ago. Evidence for sizable cores on Mars and Mercury and a small core on the moon is also discussed, and the heat involved in core formation is pointed out. Examination of the volcanic and tectonic histories of planets lacking plate tectonics indicates that core formation was not closely linked to crust formation on the moon or Mars, with chemical differentiation restricted to shallow regions, and was much more extensive on Mercury. Extension of these considerations to the earth results in a model of a hot and vigorously convecting mantle with an easily deformable crust immediately following core formation, and the gradual development of a lithosphere and plates.

  9. On effect of precession-induced flows in the liquid core for early Earth's history

    Directory of Open Access Journals (Sweden)

    S. L. Shalimov

    2006-01-01

    Full Text Available Secondary and tertiary flow patterns seen in experiments simulating flow in the Earth's liquid core induced by luni-solar precession of the solid mantle (Vanyo et al., 1995 hint at the development of non-axisymmetric columnar periodic structures. A simple interpretation of the structure formation is presented in a hydrodynamic approach. It is suggested that if similar flow patterns can occur in the Earth's liquid core enclosed into precessing and rotating mantle then kinematic of the flows may be regarded as a possible geodynamo mechanism for early Earth's history (before the solid core formation.

  10. Earth 616, Earth 1610, Earth 3490—Wait, what universe is this again? The creation and evolution of the Avengers and Captain America/Iron Man fandom

    Directory of Open Access Journals (Sweden)

    Catherine Coker

    2013-06-01

    Full Text Available This essay surveys the creation and evolution of the Captain America/Iron Man or Steve/Tony ship in Avengers fandom, from its origin in comics to its reinterpretation by fandom through the recent movies, and discusses how the alternate universe trope in both canon and fanon is used to make a case for the pairing.

  11. The Hubble Deep Field and the Early Evolution of Galaxies

    CERN Document Server

    Madau, P

    1997-01-01

    I review some recent progress made in our understanding of galaxy evolution and the cosmic history of star formation. The Hubble Deep Field (HDF) imaging survey has achieved the sensitivity to capture the bulk of the extragalactic background light from discrete sources. No evidence is found in the optical number-magnitude relation down to AB=29 mag for a large amount of star formation at high redshifts. The emission history of the universe at ultraviolet, optical, and near-infrared wavelengths can be modeled from the present epoch to z~4 by tracing the evolution with cosmic time of the galaxy luminosity density, as determined from several deep spectroscopic samples and the HDF. The global spectrophotometric properties of field galaxies are well fitted by a simple stellar evolution model, defined by a time-dependent star formation rate (SFR) per unit comoving volume and a universal initial mass function which is relatively rich in massive stars. The SFR density is found to rise sharply, by about an order of ma...

  12. Early Ideas in Underground Coal Gasification and Their Evolution

    Directory of Open Access Journals (Sweden)

    Alexander Y. Klimenko

    2009-06-01

    Full Text Available This article follows the development of early UCG (underground coal gasification ideas. Historical facts are discussed mainly from the technological perspective and early experiments in UCG are analyzed. Our search for the first successful UCG experiment brings to light a new finding, which was commonly overlooked in previous reviews. We also outline the key role that engineer and inventor A. G. Betts played in introducing technologies utilizing unmined coal; his original ideas are visible in the first successful UCG experiments and in modern UCG technology.

  13. The survival of early Earth mantle reservoirs: Evidence from flood basalts

    Science.gov (United States)

    Jackson, M. G.

    2011-12-01

    Over geologic time, large quantities of oceanic crust and sediment have been injected into the mantle at subduction zones, thereby generating heterogeneities in the mantle. The mantle has been further modified by melt extraction at mid-ocean ridges, a process that has generated large depleted reservoirs throughout the mantle. Owing to the fact that the Earth's mantle mixes and stirs chaotically on geologic timescales, it has long been thought that any evidence of an early terrestrial primitive mantle reservoir has either been erased by melt extraction, or has been overprinted by mixing with recycled materials. This hypothesis was supported by a lack of evidence for chondritic primitive mantle material in the mantle sources of oceanic hotspots, which are thought to yield material from the Earth's deep mantle. Instead, ocean island basalts (OIB) exhibit median 143Nd/144Nd isotopic ratios near 0.5130, suggesting that plume fed hotspots sample a largely-depleted mantle. However, the discovery of Boyet and Carlson (2005, Science) presented evidence that the Earth's primitive mantle may not be chondritic in composition. Boyet and Carlson (2005) found that modern terrestrial lavas have 142Nd/144Nd ratios ~18 ppm higher than chondrites. This result implies that all modern crustal and mantle reservoirs derive from a reservoir with Sm/Nd ratios ~5% higher than chondritic. Today, the 143Nd/144Nd of the primitive (albeit non-chondritic) reservoir would be ~0.5130. Critically, this value is similar to the median 143Nd/144Nd ratio identified in OIB lavas, suggesting that the OIB mantle may in fact be a largely primitive reservoir. However, most OIB lavas fail to exhibit the elevated 3He/4He ratios associated with primitive mantle reservoirs. Similarly, OIB lavas generally lack primitive Pb-isotopic compositions that plot on the geochron, a requirement for all early-Earth reservoirs. To date, no terrestrial OIB lavas have been found that exhibit the required He, Nd and Pb

  14. Earth Observations for Early Detection of Agricultural Drought: Contributions of the Famine Early Warning Systems Network (FEWS NET)

    Science.gov (United States)

    Budde, M. E.; Funk, C.; Husak, G. J.; Peterson, P.; Rowland, J.; Senay, G. B.; Verdin, J. P.

    2016-12-01

    The U.S. Geological Survey (USGS) has a long history of supporting the use of Earth observation data for food security monitoring through its role as an implementing partner of the Famine Early Warning Systems Network (FEWS NET) program. The use of remote sensing and crop modeling to address food security threats in the form of drought, floods, pests, and changing climatic regimes has been a core activity in monitoring FEWS NET countries. In recent years, it has become a requirement that FEWS NET apply monitoring and modeling frameworks at global scales to assess emerging crises in regions that FEWS NET does not traditionally monitor. USGS FEWS NET, in collaboration with the University of California, Santa Barbara, has developed a number of new global applications of satellite observations, derived products, and efficient tools for visualization and analyses to address these requirements. (1) A 35-year quasi-global (+/- 50 degrees latitude) time series of gridded rainfall estimates, the Climate Hazards Infrared Precipitation with Stations (CHIRPS) dataset, based on infrared satellite imagery and station observations. Data are available as 5-day (pentadal) accumulations at 0.05 degree spatial resolution. (2) Global actual evapotranspiration data based on application of the Simplified Surface Energy Balance (SSEB) model using 10-day MODIS Land Surface Temperature composites at 1-km resolution. (3) Production of global expedited MODIS (eMODIS) 10-day NDVI composites updated every 5 days. (4) Development of an updated Early Warning eXplorer (EWX) tool for data visualization, analysis, and sharing. (5) Creation of stand-alone tools for enhancement of gridded rainfall data and trend analyses. (6) Establishment of an agro-climatology analysis tool and knowledge base for more than 90 countries of interest to FEWS NET. In addition to these new products and tools, FEWS NET has partnered with the GEOGLAM community to develop a Crop Monitor for Early Warning (CM4EW) which

  15. Geochemistry of U and Th and its Influence on the Origin and Evolution of the Crust of Earth and the Biological Evolution

    CERN Document Server

    Bao, Xuezhao

    1998-01-01

    We have investigated the migration behaviors of uranium (U) and thorium (Th) in the Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of the Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with oxidative volatile components and water, migrate up to the asthenosphere position to form an enrichment zone (EZ) of U and Th first, and then migrate up further to the crusts through magmatism and metamorphism. We emphasize that the formation of an EZ of U, Th and other heat-producing elements is a prerequisite for the formation of a plate tectonic system. The heat-producing elements, currently mainly U and Th, in the EZ are also the energy sources that drive the formation and evolution of the crust of Earth and create special granitic continental crusts. In other terrestrial planets, including Mercury, Venus, and Mars, an EZ can not be formed ...

  16. Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth.

    Science.gov (United States)

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-04-28

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago.

  17. Evolution Inclusions and Variation Inequalities for Earth Data Processing II Differential-operator Inclusions and Evolution Variation Inequalities for Earth Data Processing

    CERN Document Server

    Zgurovsky, Mikhail Z; Kasyanov, Pavlo O

    2011-01-01

    Here, the authors present modern mathematical methods to solve problems of differential-operator inclusions and evolution variation inequalities which may occur in fields such as geophysics, aerohydrodynamics, or fluid dynamics. For the first time, they describe the detailed generalization of various approaches to the analysis of fundamentally nonlinear models and provide a toolbox of mathematical equations. These new mathematical methods can be applied to a broad spectrum of problems. Examples of these are phase changes, diffusion of electromagnetic, acoustic, vibro-, hydro- and seismoacousti

  18. On mega-undations: A new model for the earth's evolution

    NARCIS (Netherlands)

    Bemmelen, R.W. van

    Two fundamentally different views on the origin of the sialic crust of the earth are possible. According to one view the sialic crust has been produced from the inside by progressive physico-chemical differentiation of the earth's material into concentric spheres. Such an endogenic origin of the

  19. On mega-undations: A new model for the earth's evolution

    NARCIS (Netherlands)

    Bemmelen, R.W. van

    1966-01-01

    Two fundamentally different views on the origin of the sialic crust of the earth are possible. According to one view the sialic crust has been produced from the inside by progressive physico-chemical differentiation of the earth's material into concentric spheres. Such an endogenic origin of the cru

  20. Sulfur Isotopic Fractionation During Vacuum Ultraviolet Photolysis of SO2: Implication for Meteorites and Early Earth

    Science.gov (United States)

    Chakraborty, S.; Jackson, T. L.; Rude, B.; Ahmed, M.; Thiemens, M. H.

    2016-12-01

    Several sulfur bearing gas phase species existed in the solar nebula, including H2S, SO2, SiS, OCS, CS2, CS, NS and SO as a consequence of multiple available chemical valence states (S2- to S6+). Sulfur directly condensed into refractory phases in the solar nebula under reducing conditions. Mass independent (MI) sulfur isotopic compositions have been measured in chondrules and organics from chondritic meteorites. Large 33S excesses in sulfides from achondrite meteoritic groups have also been found suggesting that refractory sulfide minerals condensed from a nebular gas with an enhanced carbon to oxygen ratio. Photochemical reactions in the early solar nebula have been inferred to be a leading process in generating MI sulfur compositions. Previously, we have reported wavelength dependent mass-independent sulfur isotopic compositions (with a varying degree in D33S and D36S) in the product elemental sulfur during vacuum ultraviolet (VUV) photodissociation of H2S. Recently we performed photodissociation of SO2 experiments in the wavelength region 98 to 200 nm at low pressures (0.5 torr) using the VUV photons from the Advanced Light Source Synchrotron in a differentially pumped reaction chamber. To our knowledge, this is the first ever experiment to determine the isotopic fractionation in VUV photodissociation of SO2. At VUV energy region, SO2 is mostly predissociative. The measured sulfur isotopic compositions in the product elemental sulfur are MI and dependent on the wavelength. These new results support the previous finding from photodissociation of other di- and tri-atomic molecules (CO, N2, H2S) that predissociative photodissociation produces MI isotopic products and is a quantum mechanically driven selective phenomenon. These new results are useful because (i) they are important in interpreting meteoritic data and decipher sulfur chemistry in the early nebula which is indicative of the redox condition of the nebula (ii) SO2 photolysis in the atmosphere of early

  1. Convergence of ion channel genome content in early animal evolution

    Science.gov (United States)

    Liebeskind, Benjamin J.; Hillis, David M.; Zakon, Harold H.

    2015-01-01

    Multicellularity has evolved multiple times, but animals are the only multicellular lineage with nervous systems. This fact implies that the origin of nervous systems was an unlikely event, yet recent comparisons among extant taxa suggest that animal nervous systems may have evolved multiple times independently. Here, we use ancestral gene content reconstruction to track the timing of gene family expansions for the major families of ion-channel proteins that drive nervous system function. We find that animals with nervous systems have broadly similar complements of ion-channel types but that these complements likely evolved independently. We also find that ion-channel gene family evolution has included large loss events, two of which were immediately followed by rounds of duplication. Ctenophores, cnidarians, and bilaterians underwent independent bouts of gene expansion in channel families involved in synaptic transmission and action potential shaping. We suggest that expansions of these family types may represent a genomic signature of expanding nervous system complexity. Ancestral nodes in which nervous systems are currently hypothesized to have originated did not experience large expansions, making it difficult to distinguish among competing hypotheses of nervous system origins and suggesting that the origin of nerves was not attended by an immediate burst of complexity. Rather, the evolution of nervous system complexity appears to resemble a slow fuse in stem animals followed by many independent bouts of gene gain and loss. PMID:25675537

  2. Enhanced transcription and translation in clay hydrogel and implications for early life evolution

    Science.gov (United States)

    Yang, Dayong; Peng, Songming; Hartman, Mark R.; Gupton-Campolongo, Tiffany; Rice, Edward J.; Chang, Anna Kathryn; Gu, Zi; Lu, G. Q. (Max); Luo, Dan

    2013-11-01

    In most contemporary life forms, the confinement of cell membranes provides localized concentration and protection for biomolecules, leading to efficient biochemical reactions. Similarly, confinement may have also played an important role for prebiotic compartmentalization in early life evolution when the cell membrane had not yet formed. It remains an open question how biochemical reactions developed without the confinement of cell membranes. Here we mimic the confinement function of cells by creating a hydrogel made from geological clay minerals, which provides an efficient confinement environment for biomolecules. We also show that nucleic acids were concentrated in the clay hydrogel and were protected against nuclease, and that transcription and translation reactions were consistently enhanced. Taken together, our results support the importance of localized concentration and protection of biomolecules in early life evolution, and also implicate a clay hydrogel environment for biochemical reactions during early life evolution.

  3. Halwaxiids and the early evolution of the lophotrochozoans.

    Science.gov (United States)

    Morris, Simon Conway; Caron, Jean-Bernard

    2007-03-02

    Halkieriids and wiwaxiids are cosmopolitan sclerite-bearing metazoans from the Lower and Middle Cambrian. Although they have similar scleritomes, their phylogenetic position is contested. A new scleritomous fossil from the Burgess Shale has the prominent anterior shell of the halkieriids but also bears wiwaxiid-like sclerites. This new fossil defines the monophyletic halwaxiids and indicates that they have a key place in early lophotrochozoan history.

  4. The Interwoven Evolution of the Early Keyboard and Baroque Culture

    Directory of Open Access Journals (Sweden)

    Rachel Stevenson

    2016-04-01

    Full Text Available The purpose of this paper is to analyze the impact that Baroque society had in the development of the early keyboard. While the main timeframe is Baroque, a few references are made to the late Medieval Period in determining the reason for the keyboard to more prominently emerge in the musical scene. As Baroque society develops and new genres are formed, different keyboard instruments serve vital roles unique to their construction. These new roles also affect the way music was written for the keyboard as well. Advantages and disadvantages of each instrument are discussed, providing an analysis of what would have been either accepted or rejected by Baroque culture. While music is the main focus, other fine arts are mentioned, including architecture, poetry, politics, and others. My research includes primary and secondary resources retrieved from databases provided by Cedarville University. By demonstrating the relationship between Baroque society and early keyboard development, roles and music, this will be a helpful source in furthering the pianist's understanding of the instrument he or she plays. It also serves pedagogical purposes in its analysis of context in helping a student interpret a piece written during this time period with these early keyboard instruments.

  5. Geodynamic evolution of early Mesozoic sedimentary basins in eastern Australia

    Science.gov (United States)

    Rosenbaum, G.; Babaahmadi, A.; Esterle, J.

    2014-12-01

    Eastern Australia is covered by a series of continental sedimentary basins deposited during the Triassic and Jurassic, but the geodynamic context of these basins is not fully understood. Using gridded aeromagnetic data, seismic reflection data, geological maps, digital elevation models, and field observations, we conducted a structural synthesis aimed at characterizing major structures and deformation style in the Triassic-Jurassic sedimentary basins of eastern Australia. Our results show evidence for four alternating episodes of rifting and contractional events during the Triassic. Two major episodes of rifting, characterized by syn-sedimentary steep normal faults and bimodal volcanism, resulted in the development of the Early-Middle Triassic Esk-Nymboida Rift System and the early Late Triassic Ipswich Basin. Faults in the Esk-Nymboida Rift System have been controlled by a pre-existing oroclinal structure. Each phase of rifting was followed by a contractional event, which produced folds, reverse faults and unconformities in the basins. Since the latest Late Triassic, thermal subsidence led to the deposition of continental sediments in the Clarence-Moreton Basin, which continued until the Early Cretaceous. We suggest that the geodynamic control on the alternating episodes of rifting and contraction during the Triassic in eastern Australia was ultimately related to plate boundary migration and switches between trench retreat and advance.

  6. Evolutionary Competition Between Primitive Photosynthetic Systems: Existence of an early purple Earth?

    Science.gov (United States)

    Sparks, William B.; DasSarma, S.; Reid, I. N.

    2006-12-01

    The onset of photosynthesis in primitive cyanobacteria is thought to have profoundly altered the Earth’s atmosphere by producing an oxygen-rich atmosphere some 2 billion years ago. However, the pigments used by chlorophyll-based photosynthesis absorb at a variety of wavelengths, curiously except those centered around the peak of the Solar spectrum, 550nm. By contrast, simpler retinal-based light harvesting systems such as the haloarchaeal purple membrane bacteriorhodopsin and halorhodopsin show a strong well-defined peak of absorbance centered at 550nm. The spectroscopic complementarity for retinal pigments with chlorophyll-based pigments suggests an intriguing possibility of their co-evolution. This hypothesis argues that simpler retinal-based phototrophic capability may have evolved earlier, in microorganisms that dominated during the anaerobic and purple phase of the planet. Later, the more complex chlorophyll-based photosystem pigments could have evolved to harvest light in regions of the spectrum not absorbed by preexisting species. This would have led to the greening and oxidation of our planet and displacement of most of the retinal-based microorganisms. Not surprisingly, evidence for retinal chromoproteins have recently turned up in a variety of planktonic microorganisms. Although speculative, such a scenario would indicate that retinal-based phototrophy may be one of the oldest metabolic capabilities on Earth. Moreover, if the chlorophyll absorption spectrum is simply a product of adaptation, then its utility as a potential biomarker is likely to be limited.

  7. Dynamical evolution of interplanetary dust particles trapped in Earth's horseshoe and quasi-satellite co-orbital resonance regions

    Science.gov (United States)

    Kortenkamp, Stephen J.

    2016-10-01

    We use numerical integrations to model the orbital evolution of IDPs decaying from the asteroid belt into the inner solar system under the influence of radiation pressure, Poynting-Roberston light drag, and solar wind drag. In our models the ratio of radiation pressure to solar gravity ranges from 0.0025 up to 0.02, corresponding to IDP diameters ranging from about 200 microns down to about 25 microns, respectively. In this size range nearly 100% of IDPs become temporarily trapped in mean-motion resonances just outside Earth's orbit. While trapped in these outer resonances the orbital eccentricities of IDPs significantly increases. This causes most IDPs to eventually escape the resonances, allowing their orbits to continue decaying inwards past 1 AU. We've shown previously (Kortenkamp, Icarus 226, 1550-1558, 2013) that significant fractions of IDPs in this size range can subsequently become trapped in Earth's co-orbital horseshoe and quasi-satellite resonance regions, with semi-major axes just inside of 1 AU. Here, we present new results on the long-term effects of Earth's varying orbital eccentricity and inclination on the trapping and evolution of these co-orbital IDPs.

  8. Nonproteinogenic D-amino acids at millimolar concentrations are a toxin for anaerobic microorganisms relevant to early Earth and other anoxic planets.

    Science.gov (United States)

    Nixon, Sophie L; Cockell, Charles S

    2015-03-01

    The delivery of extraterrestrial organics to early Earth provided a potentially important source of carbon and energy for microbial life. Optically active organic compounds of extraterrestrial origin exist in racemic form, yet life on Earth has almost exclusively selected for L- over D-enantiomers of amino acids. Although D-enantiomers of proteinogenic amino acids are known to inhibit aerobic microorganisms, the role of concentrated nonproteinogenic meteoritic D-amino acids on anaerobic metabolisms relevant to early Earth and other anoxic planets such as Mars is unknown. Here, we test the inhibitory effect of D-enantiomers of two nonproteinogenic amino acids common to carbonaceous chondrites, norvaline and α-aminobutyric acid, on microbial iron reduction. Three pure strains (Geobacter bemidjiensis, Geobacter metallireducens, Geopsychrobacter electrodiphilus) and an iron-reducing enrichment culture were grown in the presence of 10 mM D-enantiomers of both amino acids. Further tests were conducted to assess the inhibitory effect of these D-amino acids at 1 and 0.1 mM. The presence of 10 mM D-norvaline and D-α-aminobutyric acid inhibited microbial iron reduction by all pure strains and the enrichment. G. bemidjiensis was not inhibited by either amino acid at 0.1 mM, but D-α-aminobutyric acid still inhibited at 1 mM. Calculations using published meteorite accumulation rates to the martian surface indicate D-α-aminobutyric acid may have reached inhibitory concentrations in little over 1000 years during peak infall. These data show that, on a young anoxic planet, the use of one enantiomer over another may render the nonbiological enantiomer an environmental toxin. Processes that generate racemic amino acids in the environment, such as meteoritic infall or impact synthesis, would have been toxic processes and could have been a selection pressure for the evolution of early racemases.

  9. Birth and early evolution of a planetary nebula

    CERN Document Server

    Bobrowsky, M; Parthasarathy, M; García-Lario, P

    1998-01-01

    The final expulsion of gas by a star as it forms a planetary nebula --- the ionized shell of gas often observed surrounding a young white dwarf --- is one of the most poorly understood stages of stellar evolution. Such nebulae form extremely rapidly (about 100 years for the ionization) and so the formation process is inherently difficult to observe. Particularly puzzling is how a spherical star can produce a highly asymmetric nebula with collimated outflows. Here we report optical observations of the Stingray Nebula which has become an ionized planetary nebula within the past few decades. We find that the collimated outflows are already evident, and we have identified the nebular structure that focuses the outflows. We have also found a companion star, reinforcing previous suspicions that binary companions play an important role in shaping planetary nebulae and changing the direction of successive outflows.

  10. Magnetic field and early evolution of circumstellar disks

    CERN Document Server

    Tsukamoto, Yusuke

    2016-01-01

    The magnetic field plays a central role in the formation and evolution of circumstellar disks. The magnetic field connects the rapidly rotating central region with the outer envelope and extracts angular momentum from the central region during gravitational collapse of the cloud core. This process is known as magnetic braking. Both analytical and multidimensional simulations have shown that disk formation is strongly suppressed by magnetic braking in moderately magnetized cloud cores in the ideal magnetohydrodynamic limit. On the other hand, recent observations have provided growing evidence of a relatively large disk several tens of astronomical units in size existing in some Class 0 young stellar objects. This introduces a serious discrepancy between the theoretical study and observations. Various physical mechanisms have been proposed to solve the problem of catastrophic magnetic braking, such as misalignment between the magnetic field and the rotation axis, turbulence, and non-ideal effect. In this paper,...

  11. Kinematical fingerprints of star cluster early dynamical evolution

    CERN Document Server

    Vesperini, Enrico; McMillan, Stephen L W; Zepf, Stephen E

    2014-01-01

    We study the effects of the external tidal field on the violent relaxation phase of star clusters dynamical evolution, with particular attention to the kinematical properties of the equilibrium configurations emerging at the end of this phase.We show that star clusters undergoing the process of violent relaxation in the tidal field of their host galaxy can acquire significant internal differential rotation and are characterized by a distinctive radial variation of the velocity anisotropy. These kinematical properties are the result of the symmetry breaking introduced by the external tidal field in the collapse phase and of the action of the Coriolis force on the orbit of the stars. The resulting equilibrium configurations are characterized by differential rotation, with a peak located between one and two half-mass radii. As for the anisotropy, similar to clusters evolving in isolation, the systems explored in this Letter are characterized by an inner isotropic core, followed by a region of increasing radial a...

  12. Effects of dust grains on early galaxy evolution

    CERN Document Server

    Hirashita, H

    2002-01-01

    Stars form out of molecular gas and supply dust grains during their last evolutionary stages; in turn hydrogen molecules (H2) are produced more efficiently on dust grains. Therefore, dust can drastically accelerate H2 formation, leading to an enhancement of star formation activity. In order to examine the first formation of stars and dust in galaxies, we model the evolution of galaxies in the redshift range of 55) galaxies in sub-millimetre and near-infrared bands. We find that: i) ALMA can detect dust emission from several thousands of galaxies per square degree, and ii) NGST can detect the stellar emission from 10^6 galaxies per square degree. Further observational checks of our predictions include the integrated flux of metal (oxygen and carbon) lines. We finally discuss possible color selection strategies for high-redshift galaxy searches.

  13. The Early-Time Evolution of the Cosmological Perturbations in f(R) Gravity

    CERN Document Server

    Gu, Je-An; Wu, Yen-Ting; Chen, Pisin; Hwang, W-Y Pauchy

    2011-01-01

    We investigate the evolution of the linear cosmological perturbations in f(R) gravity, an alternative to dark energy for explaining the late-time cosmic acceleration. We numerically calculate the early-time evolution with an approximation we contrive to solve a problem that commonly appears when one solves the full evolution equations. With the approximate evolution equations we can fairly assess the effect of the gravity modification on the early-time evolution, thereby examining the validity of the general-relativity (GR) approximation that is widely used for the early universe. In particular, we compare the CMB photon density perturbation and the matter density perturbation obtained respectively by our approximation and the conventional GR approximation. We find that the effect of the gravity modification at early times in f(R) gravity may not be negligible. We conclude that to be self-consistent, in the f(R) theory one should employ the approximation presented in this paper instead of that of GR in the tr...

  14. Evolution of Information Management at the GSFC Earth Sciences (GES) Data and Information Services Center (DISC): 2006-2007

    Science.gov (United States)

    Kempler, Steven; Lynnes, Christopher; Vollmer, Bruce; Alcott, Gary; Berrick, Stephen

    2009-01-01

    Increasingly sophisticated National Aeronautics and Space Administration (NASA) Earth science missions have driven their associated data and data management systems from providing simple point-to-point archiving and retrieval to performing user-responsive distributed multisensor information extraction. To fully maximize the use of remote-sensor-generated Earth science data, NASA recognized the need for data systems that provide data access and manipulation capabilities responsive to research brought forth by advancing scientific analysis and the need to maximize the use and usability of the data. The decision by NASA to purposely evolve the Earth Observing System Data and Information System (EOSDIS) at the Goddard Space Flight Center (GSFC) Earth Sciences (GES) Data and Information Services Center (DISC) and other information management facilities was timely and appropriate. The GES DISC evolution was focused on replacing the EOSDIS Core System (ECS) by reusing the In-house developed disk-based Simple, Scalable, Script-based Science Product Archive (S4PA) data management system and migrating data to the disk archives. Transition was completed in December 2007

  15. A Cretaceous eutriconodont and integument evolution in early mammals.

    Science.gov (United States)

    Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D

    2015-10-15

    The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

  16. A Cretaceous eutriconodont and integument evolution in early mammals

    Science.gov (United States)

    Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D.

    2015-10-01

    The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

  17. Global-scale modelling of melting and isotopic evolution of Earth's mantle: Melting modules for TERRA

    NARCIS (Netherlands)

    Van Heck, H.J.; Huw Davies, J.; Elliott, T.; Porcelli, D.

    2016-01-01

    Many outstanding problems in solid-Earth science relate to the geodynamical explanation of geochemical observations. Currently, extensive geochemical databases of surface observations exist, but satisfying explanations of underlying mantle processes are lacking. One way to address these problems is

  18. Evolution of marine and terrestrial geobiodiversity in the history of the earth

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    People have long been curious about the history of life on the earth-how many different species have existed, when they first occurred, how they evolved over geologic time, and how they reacted to major environmental crises.

  19. Early evolution of efficient enzymes and genome organization

    Directory of Open Access Journals (Sweden)

    Szilágyi András

    2012-10-01

    Full Text Available Abstract Background Cellular life with complex metabolism probably evolved during the reign of RNA, when it served as both information carrier and enzyme. Jensen proposed that enzymes of primordial cells possessed broad specificities: they were generalist. When and under what conditions could primordial metabolism run by generalist enzymes evolve to contemporary-type metabolism run by specific enzymes? Results Here we show by numerical simulation of an enzyme-catalyzed reaction chain that specialist enzymes spread after the invention of the chromosome because protocells harbouring unlinked genes maintain largely non-specific enzymes to reduce their assortment load. When genes are linked on chromosomes, high enzyme specificity evolves because it increases biomass production, also by reducing taxation by side reactions. Conclusion The constitution of the genetic system has a profound influence on the limits of metabolic efficiency. The major evolutionary transition to chromosomes is thus proven to be a prerequisite for a complex metabolism. Furthermore, the appearance of specific enzymes opens the door for the evolution of their regulation. Reviewers This article was reviewed by Sándor Pongor, Gáspár Jékely, and Rob Knight.

  20. Early evolution of efficient enzymes and genome organization

    Science.gov (United States)

    2012-01-01

    Background Cellular life with complex metabolism probably evolved during the reign of RNA, when it served as both information carrier and enzyme. Jensen proposed that enzymes of primordial cells possessed broad specificities: they were generalist. When and under what conditions could primordial metabolism run by generalist enzymes evolve to contemporary-type metabolism run by specific enzymes? Results Here we show by numerical simulation of an enzyme-catalyzed reaction chain that specialist enzymes spread after the invention of the chromosome because protocells harbouring unlinked genes maintain largely non-specific enzymes to reduce their assortment load. When genes are linked on chromosomes, high enzyme specificity evolves because it increases biomass production, also by reducing taxation by side reactions. Conclusion The constitution of the genetic system has a profound influence on the limits of metabolic efficiency. The major evolutionary transition to chromosomes is thus proven to be a prerequisite for a complex metabolism. Furthermore, the appearance of specific enzymes opens the door for the evolution of their regulation. Reviewers This article was reviewed by Sándor Pongor, Gáspár Jékely, and Rob Knight. PMID:23114029

  1. Cracking the Code of Soil Genesis. The Early Role of Rare Earth Elements

    Science.gov (United States)

    Zaharescu, D. G.; Dontsova, K.; Burghelea, C. I.; Maier, R. M.; Huxman, T. E.; Chorover, J.

    2014-12-01

    Soil is terrestrial life support system. Its genesis involves tight interactions between biota and mineral surfaces that mobilize structural elements into biogeochemical cycles. Of all chemical elements rare earth elements (REE) are a group of 16 non-nutrient elements of unusual geochemical similarity and present in all components of the surface environment. While much is known about the role of major nutrients in soil development we lack vital understanding of how early biotic colonization affects more conservative elements such as REE. A highly controlled experiment was set up at University of Arizona's Biosphere-2 that tested the effect of 4 biological treatments, incorporating a combination of microbe, grass, mycorrhiza and uninoculated control on REE leaching and uptake in 4 bedrock substrates: basalt, rhyolite, granite and schist. Generally the response of REE to biota presence was synergistic. Variation in total bedrock chemistry could explain major trends in pore water REE. There was a fast transition from chemistry-dominated to a biota dominated environment in the first 3-4 months of inoculation/seeding which translated into increase in REE signal over time. Relative REE abundances in water were generally reflected in plant concentrations, particularly in root, implying that below ground biomass is the main sync of REE in the ecosystem. Mycorrhiza effect on REE uptake in plant organs was significant and increased with infection rates. Presence of different biota translated into subtle differences in REE release, reveling potential biosignatures of biolota-rock colonization. The results thus bring fundamental insight into early stages non-nutrient cycle and soil genesis.

  2. Phylogenetic origins of biological cognition: convergent patterns in the early evolution of learning.

    Science.gov (United States)

    van Duijn, Marc

    2017-06-06

    Various forms of elementary learning have recently been discovered in organisms lacking a nervous system, such as protists, fungi and plants. This finding has fundamental implications for how we view the role of convergent evolution in biological cognition. In this article, I first review the evidence for basic forms of learning in aneural organisms, focusing particularly on habituation and classical conditioning and considering the plausibility for convergent evolution of these capacities. Next, I examine the possible role of convergent evolution regarding these basic learning abilities during the early evolution of nervous systems. The evolution of nervous systems set the stage for at least two major events relevant to convergent evolution that are central to biological cognition: (i) nervous systems evolved, perhaps more than once, because of strong selection pressures for sustaining sensorimotor strategies in increasingly larger multicellular organisms and (ii) associative learning was a subsequent adaptation that evolved multiple times within the neuralia. Although convergent evolution of basic forms of learning among distantly related organisms such as protists, plants and neuralia is highly plausible, more research is needed to verify whether these forms of learning within the neuralia arose through convergent or parallel evolution.

  3. Analytic model for the long-term evolution of circular Earth satellite orbits including lunar node regression

    Science.gov (United States)

    Zhu, Ting-Lei; Zhao, Chang-Yin; Zhang, Ming-Jiang

    2017-04-01

    This paper aims to obtain an analytic approximation to the evolution of circular orbits governed by the Earth's J2 and the luni-solar gravitational perturbations. Assuming that the lunar orbital plane coincides with the ecliptic plane, Allan and Cook (Proc. R. Soc. A, Math. Phys. Eng. Sci. 280(1380):97, 1964) derived an analytic solution to the orbital plane evolution of circular orbits. Using their result as an intermediate solution, we establish an approximate analytic model with lunar orbital inclination and its node regression be taken into account. Finally, an approximate analytic expression is derived, which is accurate compared to the numerical results except for the resonant cases when the period of the reference orbit approximately equals the integer multiples (especially 1 or 2 times) of lunar node regression period.

  4. Early events in the evolution of spider silk genes.

    Directory of Open Access Journals (Sweden)

    James Starrett

    Full Text Available Silk spinning is essential to spider ecology and has had a key role in the expansive diversification of spiders. Silk is composed primarily of proteins called spidroins, which are encoded by a multi-gene family. Spidroins have been studied extensively in the derived clade, Orbiculariae (orb-weavers, from the suborder Araneomorphae ('true spiders'. Orbicularians produce a suite of different silks, and underlying this repertoire is a history of duplication and spidroin gene divergence. A second class of silk proteins, Egg Case Proteins (ECPs, is known only from the orbicularian species, Lactrodectus hesperus (Western black widow. In L. hesperus, ECPs bond with tubuliform spidroins to form egg case silk fibers. Because most of the phylogenetic diversity of spiders has not been sampled for their silk genes, there is limited understanding of spidroin gene family history and the prevalence of ECPs. Silk genes have not been reported from the suborder Mesothelae (segmented spiders, which diverged from all other spiders >380 million years ago, and sampling from Mygalomorphae (tarantulas, trapdoor spiders and basal araneomorph lineages is sparse. In comparison to orbicularians, mesotheles and mygalomorphs have a simpler silk biology and thus are hypothesized to have less diversity of silk genes. Here, we present cDNAs synthesized from the silk glands of six mygalomorph species, a mesothele, and a non-orbicularian araneomorph, and uncover a surprisingly rich silk gene diversity. In particular, we find ECP homologs in the mesothele, suggesting that ECPs were present in the common ancestor of extant spiders, and originally were not specialized to complex with tubuliform spidroins. Furthermore, gene-tree/species-tree reconciliation analysis reveals that numerous spidroin gene duplications occurred after the split between Mesothelae and Opisthothelae (Mygalomorphae plus Araneomorphae. We use the spidroin gene tree to reconstruct the evolution of amino acid

  5. Early events in the evolution of spider silk genes.

    Science.gov (United States)

    Starrett, James; Garb, Jessica E; Kuelbs, Amanda; Azubuike, Ugochi O; Hayashi, Cheryl Y

    2012-01-01

    Silk spinning is essential to spider ecology and has had a key role in the expansive diversification of spiders. Silk is composed primarily of proteins called spidroins, which are encoded by a multi-gene family. Spidroins have been studied extensively in the derived clade, Orbiculariae (orb-weavers), from the suborder Araneomorphae ('true spiders'). Orbicularians produce a suite of different silks, and underlying this repertoire is a history of duplication and spidroin gene divergence. A second class of silk proteins, Egg Case Proteins (ECPs), is known only from the orbicularian species, Lactrodectus hesperus (Western black widow). In L. hesperus, ECPs bond with tubuliform spidroins to form egg case silk fibers. Because most of the phylogenetic diversity of spiders has not been sampled for their silk genes, there is limited understanding of spidroin gene family history and the prevalence of ECPs. Silk genes have not been reported from the suborder Mesothelae (segmented spiders), which diverged from all other spiders >380 million years ago, and sampling from Mygalomorphae (tarantulas, trapdoor spiders) and basal araneomorph lineages is sparse. In comparison to orbicularians, mesotheles and mygalomorphs have a simpler silk biology and thus are hypothesized to have less diversity of silk genes. Here, we present cDNAs synthesized from the silk glands of six mygalomorph species, a mesothele, and a non-orbicularian araneomorph, and uncover a surprisingly rich silk gene diversity. In particular, we find ECP homologs in the mesothele, suggesting that ECPs were present in the common ancestor of extant spiders, and originally were not specialized to complex with tubuliform spidroins. Furthermore, gene-tree/species-tree reconciliation analysis reveals that numerous spidroin gene duplications occurred after the split between Mesothelae and Opisthothelae (Mygalomorphae plus Araneomorphae). We use the spidroin gene tree to reconstruct the evolution of amino acid compositions of

  6. Geologic constraints on earth system sensitivity to CO2 during the Cretaceous and early Paleogene

    Directory of Open Access Journals (Sweden)

    D. J. Beerling

    2011-03-01

    Full Text Available Earth system sensitivity (ESS is the long-term (>103 yr equilibrium temperature response to doubled CO2. ESS has climate policy implications because global temperatures are not expected to decline appreciably for at least 103 yr, even if anthropogenic greenhouse-gas emissions drop to zero. We report quantitative ESS estimates of 3 °C or higher for much of the Cretaceous and early Paleogene based on paleo-reconstructions of CO2 and temperature. These estimates are generally higher than climate sensitivities simulated from global climate models for the same ancient periods (~3 °C. We conclude that climate models do not capture the full suite of positive climate feedbacks during greenhouse worlds. These absent feedbacks are probably related to clouds, trace greenhouse gases, seasonal snow cover, and/or vegetation, especially in polar regions. Continued warming in the coming decades as anthropogenic greenhouse gases accumulate in the atmosphere ensures that characterizing and quantifying these positive climate feedbacks will become a scientific challenge of increasing priority.

  7. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

    Science.gov (United States)

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-12-01

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

  8. Evolution of attention mechanisms for early visual processing

    Science.gov (United States)

    Müller, Thomas; Knoll, Alois

    2011-03-01

    Early visual processing as a method to speed up computations on visual input data has long been discussed in the computer vision community. The general target of a such approaches is to filter nonrelevant information from the costly higher-level visual processing algorithms. By insertion of this additional filter layer the overall approach can be speeded up without actually changing the visual processing methodology. Being inspired by the layered architecture of the human visual processing apparatus, several approaches for early visual processing have been recently proposed. Most promising in this field is the extraction of a saliency map to determine regions of current attention in the visual field. Such saliency can be computed in a bottom-up manner, i.e. the theory claims that static regions of attention emerge from a certain color footprint, and dynamic regions of attention emerge from connected blobs of textures moving in a uniform way in the visual field. Top-down saliency effects are either unconscious through inherent mechanisms like inhibition-of-return, i.e. within a period of time the attention level paid to a certain region automatically decreases if the properties of that region do not change, or volitional through cognitive feedback, e.g. if an object moves consistently in the visual field. These bottom-up and top-down saliency effects have been implemented and evaluated in a previous computer vision system for the project JAST. In this paper an extension applying evolutionary processes is proposed. The prior vision system utilized multiple threads to analyze the regions of attention delivered from the early processing mechanism. Here, in addition, multiple saliency units are used to produce these regions of attention. All of these saliency units have different parameter-sets. The idea is to let the population of saliency units create regions of attention, then evaluate the results with cognitive feedback and finally apply the genetic mechanism

  9. Early evolution of the continental crust, the oxygenated atmosphere and oceans, and the heterogeneous mantle

    Science.gov (United States)

    Ohmoto, H.

    2011-12-01

    The current paradigm for the evolution of early Earth is that, only since ~2.5 Ga ago, the Earth began to: (a) form a large granitic continental crust; (b) form an oxygenated atmosphere; (c) operate oxidative weathering of rocks on land; (d) form Fe-poor, but S-, U- and Mo-rich, oceans; (e) operate large-scale transfers of elements between oceans and oceanic crust at MORs; (f) subduct the altered oceanic crust; (g) create the mantle heterogeneity, especially in the concentrations and isotopic compositions of Fe(III), Fe(II), U, Pb, alkali elements, C, S, REEs, and many other elements; (h) create chemical and isotopic variations among OIB-, OPB-, and MORB magmas, and between I- and S-type granitoid magmas; and (i) create variations in the chemical and isotopic compositions of volcanic gas. Submarine hydrothermal fluids have typically developed from seawater-rock interactions during deep (>2 km) circulation of seawater through underlying hot volcanic rocks. When the heated hydrothermal fluids ascend toward the seafloor, they mix with local bottom seawater to precipitate a variety of minerals on and beneath the seafloor. Thus, the mineralogy and geochemistry of submarine hydrothermal deposits and associated volcanic rocks can be used to decipher the chemistry of the contemporaneous seawater, which in turn indicate the chemistry of the atmosphere and the compositions and size of the continental crust. The results of mineralogical and geochemical investigations by our and other research groups on submarine hydrothermal deposits (VMS and BIF) and hydrothermally-altered submarine volcanic rocks in Australia, South Africa, and Canada, ~3.5-2.5 Ga in ages, suggest that the above processes (a)-(i) had began by ~3.5 Ga ago. Supportive evidence includes, but not restricted to, the similarities between Archean submarine rocks and modern ones in: (1) the abundance of ferric oxides; (2) the Fe(III)/Fe(I) ratios; (3) the abundance of barite; (4) the increased Li contents; (5) the

  10. Basin evolution and deposition during the Early Paleogene in Tunisia

    Energy Technology Data Exchange (ETDEWEB)

    Zaier, A.; Beji-Sassi, A.; Sassi, S. [Universite de Tunis II (Libyan Arab Jamahiriya). Laboratoire des Ressources Minerales; Moody, R.T.J. [Kingston University (United Kingdom). School of Geological Science

    1998-12-31

    The marine Paleocene and Ypresian deposits of Tunisia, within the El Haria Formation and the Metlaoui Group, have been intensively studied because of the commercial interest in phosphates and hydrocarbons. This paper presents the latest updates of isochron, lithofacies and palaeogeographical maps, and interprets the patterns identified in light of syn-sedimentary structures. This reveals a close association between structure, basin geometry and subsidence. Facies distribution during the Early Paleogene is thought to be structurally controlled along basement lineaments. These major fault systems were reactivated several times during Mesozoic and Tertiary, with the last movements occurring as Neogene and post-Villafranchian events. The structural control of facies is most evident during the Ypresian, particularly along the `North-South Axis` (Nosa) a sub-meridian orogenic segment of Central Tunisia. The general pattern across Tunisia throughout the period is of a number of small tectonically controlled basins. The distribution of phosphorites, organic-rich shales and evaporites can be particularly linked to the development of restricted basins during the period. (author)

  11. Formation and early evolution of massive black holes

    Science.gov (United States)

    Madau, Piero

    2007-04-01

    I review scenarios for the assembly of massive black holes (MBHs) at the center of galaxies that trace their hierarchical build-up far up in the dark halo merger tree. The first active galactic nuclei likely formed 150 Myr after the big bang in 1e6 Msun minihaloes. X-ray photons from such miniquasars may have permeated the universe more uniformly than EUV radiation, made the low-density diffuse intergalactic medium shine at 21-cm prior to the epoch of reionization, and changed the chemistry of primordial gas. I'll discuss the conditions under which massive black holes become incorporated through a series of mergers into larger and larger halos, sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, form a binary system, and eventually coalesce. The spin distribution of MBHs is determined by gas accretion, and is predicted to be heavily skewed towards fast-rotating Kerr holes, already in place at early epochs, and not to change significantly below redshift 5. Decaying MBH binaries may shape the innermost central regions of galaxies and should be detected in significant numbers by LISA.

  12. Early evolution of the T-box transcription factor family

    Science.gov (United States)

    Sebé-Pedrós, Arnau; Ariza-Cosano, Ana; Weirauch, Matthew T.; Leininger, Sven; Yang, Ally; Torruella, Guifré; Adamski, Marcin; Adamska, Maja; Hughes, Timothy R.; Gómez-Skarmeta, José Luis; Ruiz-Trillo, Iñaki

    2013-01-01

    Developmental transcription factors are key players in animal multicellularity, being members of the T-box family that are among the most important. Until recently, T-box transcription factors were thought to be exclusively present in metazoans. Here, we report the presence of T-box genes in several nonmetazoan lineages, including ichthyosporeans, filastereans, and fungi. Our data confirm that Brachyury is the most ancient member of the T-box family and establish that the T-box family diversified at the onset of Metazoa. Moreover, we demonstrate functional conservation of a homolog of Brachyury of the protist Capsaspora owczarzaki in Xenopus laevis. By comparing the molecular phenotype of C. owczarzaki Brachyury with that of homologs of early branching metazoans, we define a clear difference between unicellular holozoan and metazoan Brachyury homologs, suggesting that the specificity of Brachyury emerged at the origin of Metazoa. Experimental determination of the binding preferences of the C. owczarzaki Brachyury results in a similar motif to that of metazoan Brachyury and other T-box classes. This finding suggests that functional specificity between different T-box classes is likely achieved by interaction with alternative cofactors, as opposed to differences in binding specificity. PMID:24043797

  13. Early evolution of disrupted asteroid P/2016 G1 (PANSTARRS)

    CERN Document Server

    Moreno, Fernando; Cabrera-Lavers, Antonio; Pozuelos, Francisco J

    2016-01-01

    We present deep imaging observations of activated asteroid P/2016 G1 (PANSTARRS) using the 10.4m Gran Telescopio Canarias (GTC) from late April to early June 2016. The images are best interpreted as the result of a relatively short-duration event with onset about $\\mathop{350}_{-30}^{+10}$ days before perihelion (i.e., around 10th February, 2016), starting sharply and decreasing with a $\\mathop{24}_{-7}^{+10}$ days (Half-width at half-maximum, HWHM). The results of the modeling imply the emission of $\\sim$1.7$\\times$10$^7$ kg of dust, if composed of particles of 1 micrometer to 1 cm in radius, distributed following a power-law of index --3, and having a geometric albedo of 0.15. A detailed fitting of a conspicuous westward feature in the head of the comet-like object indicates that a significant fraction of the dust was ejected along a privileged direction right at the beginning of the event, which suggests that the parent body has possibly suffered an impact followed by a partial or total disruption. From th...

  14. The evolution of insight, paranoia and depression during early schizophrenia.

    Science.gov (United States)

    Drake, R J; Pickles, A; Bentall, R P; Kinderman, P; Haddock, G; Tarrier, N; Lewis, S W

    2004-02-01

    How insight, paranoia and depression evolve in relation to each other during and after the first episode of schizophrenia is poorly understood but of clinical importance. Serial assessments over 18 months were made using multiple instruments in a consecutive sample of 257 patients with first episode DSM-IV non-affective psychosis. Repeated measures of paranoia, insight, depression and self-esteem were analysed using structural equation modelling, to examine the direction of relationships over time after controlling for confounds. Depression was predicted directly by greater insight, particularly at baseline, and by greater paranoia at every stage of follow-up. Neither relationship was mediated by self-esteem, although there was a weak association of lower self-esteem with greater depression and better insight. Paranoia was not strongly associated with insight. Duration of untreated psychosis and substance use at baseline predicted depression at 18 months. In first-episode psychosis, good insight predicts depression. Subsequently, paranoia is the strongest predictor. Neither effect is mediated by low self-esteem. Effective treatment of positive symptoms is important in preventing and treating low mood in early schizophrenia.

  15. NASA's Evolution to K(sub a)- Band Space Communications for Near-Earth Spacecraft

    Science.gov (United States)

    McCarthy, Kevin P.; Stocklin, Frank J.; Geldzahler, Barry J.; Friedman, Daniel E.; Celeste, Peter B.

    2010-01-01

    Over the next several years, NASA plans to launch multiple earth-science missions which will send data from low-Earth orbits to ground stations at 1-3 Gbps, to achieve data throughputs of 5-40 terabits per day. These transmission rates exceed the capabilities of S-band and X-band frequency allocations used for science probe downlinks in the past. Accordingly, NASA is exploring enhancements to its space communication capabilities to provide the Agency's first Ka-band architecture solution for next generation missions in the near-earth regime. This paper describes the proposed Ka-band solution's drivers and concept, constraints and analyses which shaped that concept, and expansibility for future needs

  16. Size Evolution of Early-Type Galaxies and Massive Compact Objects as the Dark Matter

    CERN Document Server

    Totani, Tomonori

    2009-01-01

    The dramatic size evolution of early-type galaxies from z ~ 2 to 0 poses a new challenge in the theory of galaxy formation, which may not be explained by the standard picture. It is shown here that the size evolution can be explained if the non-baryonic cold dark matter is composed of compact objects having a mass scale of ~10^5 M_sun. This form of dark matter is consistent with or only weakly constrained by the currently available observations. The kinetic energy of the dark compact objects is transferred to stars by dynamical friction, and stars around the effective radius are pushed out to larger radii, resulting in a pure size evolution. This scenario has several good properties to explain the observations, including the ubiquitous nature of size evolution and faster disappearance of higher density galaxies.

  17. Time-dependent heat transfer in the spherical Earth: Implications on the power and thermal evolution of the core

    Science.gov (United States)

    Hofmeister, A. M.; Criss, R. E.

    2015-12-01

    We quantitatively investigate the time-dependence of heat conduction for a post-core, spherical Earth that is not convecting, due to compositional layering, based on hundreds of measurements of thermal diffusivity (D) for insulators and metals. Consistency of our solutions for widely ranging input parameters indicates how additional heat transfer mechanisms (mantle magmatism and convection) affect thermal evolution of the core. We consider 1) interior starting temperatures (T) of 273-5000 K, which represent variations in primordial heat, 2) different distributions and decay of long-lived radioactive isotopes, 3) additional heat sources in the core (primordial or latent heat), and 4) variable depth-T dependence of D. Our new analytical solution for cooling of a constant D sphere validates our numerical results. The bottom line is that the thermally insulating nature of minerals, combined with constraints of spherical geometry, limits steep thermal gradients to the upper mantle, consistent with the short length scale (x ~700 km) of cooling over t = 4.5 Ga indicated by dimensional analysis [x2 ~ 4Dt], and with plate tectonics. Consequently, interior temperatures vary little so the core has remained hot and is possibly warming. Findings include: 1) Constant vs. variable D affects thermal profiles only in detail, with D for the metallic core being inconsequential. 2) The hottest zone in Earth may lie in the uppermost lower mantle; 3) Most radiogenic heat is released in Earth's outermost 1000 km thereby driving an active outer shell; 4) Earth's core is essentially isothermal and is thus best described by the liquid-solid phase boundary; 5) Deeply sequestered radioactivity or other heat will melt the core rather than by run the dynamo (note that the heat needed to have melted the outer core is 10% of radiogenic heat generated over Earth's history); 6) Inefficient cooling of an Earth-sized mass means that heat essentially remains where it is generated, until it is removed

  18. Recent Alkaline Lakes: Clues to Understanding the Evolution of Early Planetary Alkaline Oceans and Biogenesis

    Science.gov (United States)

    Kempe, S.; Hartmann, J.; Kazmierczak, J.

    2008-09-01

    Abstract New models suggest that terrestrial weathering consumes 0.26GtC/a (72% silicate-, 28% carbonateweathering), equivalent to a loss of one atmospheric C content every 3700a. Rapid weathering leads in volcanic areas to alkaline conditions, illustrated by the crater lake of Niuafo`ou/Tonga and Lake Van/Turkey, the largest soda lake on Earth. Alkaline conditions cause high CaCO3 supersaturation, permineralization of algal mats and growth of stromatolites. Alkaline conditions can nearly depress free [Ca2+] to levels necessary for proteins to function. Therefore early oceans on Earth (and possibly on Mars) should have been alkaline (i.e. "Soda Oceans"). Recent findings of MgSO4 in top soils on Mars may be misleading about the early history of martian oceans.

  19. Hf and Nd Isotope Evidence for Production of an Incompatible Trace Element Enriched Crustal Reservoir in Early Earth (Invited)

    Science.gov (United States)

    Brandon, A. D.; Debaille, V.; Lapen, T. J.

    2010-12-01

    The final significant stage of accretion of the Earth was likely a collision between proto-Earth and a Mars sized impactor that formed the Moon. This event is thought to have produced enough thermal energy to melt all or most of the Earth, with a consequent magma ocean (MO). During subsequent cooling, the Earth would have formed its protocrust and corresponding mantle lithosphere, consisting of solidified basalt-komatiitic melt, in combination with buoyant cumulates and late stage residual melts from the MO. Relative to the convecting mantle, portions of this protolithosphere are likely to have been enriched in incompatible trace elements (ITE) in sufficient quantities to contain a significant amount of the bulk Earth’s budget for rare earth elements, U, Th, and Hf. If the protolithosphere was negatively buoyant, it may have overturned at or near the final stages of MO crystallization and a significant portion of that material may have been transported into the deep mantle where it resided and remixed into the convecting mantle over Earth history [1,2]. If the protolithosphere remained positively buoyant, its crust would have likely begun to erode from surface processes, and subsequently recycled back into the mantle over time as sediment and altered crust, once a subduction mechanism arose. The Nd and Hf isotopic compositions of Earth’s earliest rocks support the idea that an early-formed ITE-enriched reservoir was produced. The maxima in 142Nd/144Nd for 3.85 to 3.64 Ga rocks from Isua, Greenland decreases from +20 ppm to +12 ppm relative to the present day mantle value, respectively [3]. This indicates mixing of an early-formed ITE enriched reservoir back into the convecting mantle. In addition, zircons from the 3.1 Ga Jack Hills conglomerate indicate that material with an enriched 176Lu/177Hf of ~0.02 and an age of 4.4 Ga or greater was present at the Earth’s surface over the first 2 Ga of Earth history, supporting the scenario of a positively buoyant

  20. Thermochemical equilibrium calculations of high-temperature O2 generation on the early Earth: Giant asteroid impacts on land

    Directory of Open Access Journals (Sweden)

    PAVLE I. PREMOVIC

    2003-02-01

    Full Text Available Earth’s atmosphere is composed primarily of N2 and O2. The origin of free O2 in the early Earth’s atmosphere is still subject of considerable debate.1 Theoretical models suggest that the initial form of free O2 in the atmosphere has been oceanic H2O. Recent computation modelling has suggested that a superheated (ca. 2000 K H2O vapor atmosphere of 1.4x1021 kg (the present mass of the oceans lasting for about 3000 y could probably have been formed on Earth by an enormous (ca. 1028 J asteroid impact. In this report, the occurrence of the thermochemical dissociation of the vapor, creating a primitive oxygenic (ca. 0.1 of the present level (PAL of free O2 atmosphere.

  1. Widespread tungsten isotope anomalies and W mobility in crustal and mantle rocks of the Eoarchean Saglek Block, northern Labrador, Canada: Implications for early Earth processes and W recycling

    Science.gov (United States)

    Liu, Jingao; Touboul, Mathieu; Ishikawa, Akira; Walker, Richard J.; Graham Pearson, D.

    2016-08-01

    Well-resolved 182W isotope anomalies, relative to the present mantle, in Hadean-Archean terrestrial rocks have been interpreted to reflect the effects of variable late accretion and early mantle differentiation processes. To further explore these early Earth processes, we have carried out W concentration and isotopic measurements of Eoarchean ultramafic rocks, including lithospheric mantle rocks, meta-komatiites, a layered ultramafic body and associated crustal gneisses and amphibolites from the Uivak gneiss terrane of the Saglek Block, northern Labrador, Canada. These analyses are augmented by in situ W concentration measurements of individual phases in order to examine the major hosts of W in these rocks. Although the W budget in some rocks can be largely explained by a combination of their major phases, W in other rocks is hosted mainly in secondary grain-boundary assemblages, as well as in cryptic, unidentified W-bearing 'nugget' minerals. Whole rock W concentrations in the ultramafic rocks show unexpected enrichments relative, to elements with similar incompatibilities. By contrast, W concentrations are low in the Uivak gneisses. These data, along with the in situ W concentration data, suggest metamorphic transport/re-distribution of W from the regional felsic rocks, the Uivak gneiss precursors, to the spatially associated ultramafic rocks. All but one sample from the lithologically varied Eoarchean Saglek suite is characterized by generally uniform ∼ + 11 ppm enrichments in 182W relative to Earth's modern mantle. Modeling shows that the W isotopic enrichments in the ultramafic rocks were primarily inherited from the surrounding 182W-rich felsic precursor rocks, and that the W isotopic composition of the original ultramafic rocks cannot be determined. The observed W isotopic composition of mafic to ultramafic rocks in intimate contact with ancient crust should be viewed with caution in order to plate constraints on the early Hf-W isotopic evolution of the

  2. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally

  3. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally

  4. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  5. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  6. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  7. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  8. Excursions into the Evolution of Early-Type Galaxies in Clusters

    CERN Document Server

    López-Cruz, O; Barrientos, L F; Gladders, M D; Yee, H K C; Kodama, T; Lopez-Cruz, Omar; Schade, David; Gladders, Michael D.

    2002-01-01

    Recent observations have revealed that early-type galaxies (ETG) in clusters comprise an old galaxy population that is evolving passively. We review some recent observations from the ground and from HST that show that ETG have undergone a significant amount of luminosity evolution. This evolution is traced by two projections of the fundamental plane (FP): the size-magnitude relation (SMR) and the color-magnitude relation (CMR). We will briefly discuss the relevance of all these results in the context of the universality of the IMF.

  9. The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes

    Science.gov (United States)

    Pangle, Luke A.; DeLong, Stephen B.; Abramson, Nate; Adams, John; Barron-Gafford, Greg A.; Breshears, David D.; Brooks, Paul D.; Chorover, Jon; Dietrich, William E.; Dontsova, Katerina; Durcik, Matej; Espeleta, Javier; Ferre, T. P. A.; Ferriere, Regis; Henderson, Whitney; Hunt, Edward A.; Huxman, Travis E.; Millar, David; Murphy, Brendan; Niu, Guo-Yue; Pavao-Zuckerman, Mitch; Pelletier, Jon D.; Rasmussen, Craig; Ruiz, Joaquin; Saleska, Scott; Schaap, Marcel; Sibayan, Michael; Troch, Peter A.; Tuller, Markus; van Haren, Joost; Zeng, Xubin

    2015-09-01

    Zero-order drainage basins, and their constituent hillslopes, are the fundamental geomorphic unit comprising much of Earth's uplands. The convergent topography of these landscapes generates spatially variable substrate and moisture content, facilitating biological diversity and influencing how the landscape filters precipitation and sequesters atmospheric carbon dioxide. In light of these significant ecosystem services, refining our understanding of how these functions are affected by landscape evolution, weather variability, and long-term climate change is imperative. In this paper we introduce the Landscape Evolution Observatory (LEO): a large-scale controllable infrastructure consisting of three replicated artificial landscapes (each 330 m2 surface area) within the climate-controlled Biosphere 2 facility in Arizona, USA. At LEO, experimental manipulation of rainfall, air temperature, relative humidity, and wind speed are possible at unprecedented scale. The Landscape Evolution Observatory was designed as a community resource to advance understanding of how topography, physical and chemical properties of soil, and biological communities coevolve, and how this coevolution affects water, carbon, and energy cycles at multiple spatial scales. With well-defined boundary conditions and an extensive network of sensors and samplers, LEO enables an iterative scientific approach that includes numerical model development and virtual experimentation, physical experimentation, data analysis, and model refinement. We plan to engage the broader scientific community through public dissemination of data from LEO, collaborative experimental design, and community-based model development.

  10. The Landscape Evolution Observatory: a large-scale controllable infrastructure to study coupled Earth-surface processes

    Science.gov (United States)

    Pangle, Luke A.; DeLong, Stephen B.; Abramson, Nate; Adams, John; Barron-Gafford, Greg A.; Breshears, David D.; Brooks, Paul D.; Chorover, Jon; Dietrich, William E.; Dontsova, Katerina; Durcik, Matej; Espeleta, Javier; Ferre, T. P. A.; Ferriere, Regis; Henderson, Whitney; Hunt, Edward A.; Huxman, Travis E.; Millar, David; Murphy, Brendan; Niu, Guo-Yue; Pavao-Zuckerman, Mitch; Pelletier, Jon D.; Rasmussen, Craig; Ruiz, Joaquin; Saleska, Scott; Schaap, Marcel; Sibayan, Michael; Troch, Peter A.; Tuller, Markus; van Haren, Joost; Zeng, Xubin

    2015-01-01

    Zero-order drainage basins, and their constituent hillslopes, are the fundamental geomorphic unit comprising much of Earth's uplands. The convergent topography of these landscapes generates spatially variable substrate and moisture content, facilitating biological diversity and influencing how the landscape filters precipitation and sequesters atmospheric carbon dioxide. In light of these significant ecosystem services, refining our understanding of how these functions are affected by landscape evolution, weather variability, and long-term climate change is imperative. In this paper we introduce the Landscape Evolution Observatory (LEO): a large-scale controllable infrastructure consisting of three replicated artificial landscapes (each 330 m2 surface area) within the climate-controlled Biosphere 2 facility in Arizona, USA. At LEO, experimental manipulation of rainfall, air temperature, relative humidity, and wind speed are possible at unprecedented scale. The Landscape Evolution Observatory was designed as a community resource to advance understanding of how topography, physical and chemical properties of soil, and biological communities coevolve, and how this coevolution affects water, carbon, and energy cycles at multiple spatial scales. With well-defined boundary conditions and an extensive network of sensors and samplers, LEO enables an iterative scientific approach that includes numerical model development and virtual experimentation, physical experimentation, data analysis, and model refinement. We plan to engage the broader scientific community through public dissemination of data from LEO, collaborative experimental design, and community-based model development.

  11. Evolution of Mg-5Al-0.4Mn microstructure after rare earth elements addition

    Directory of Open Access Journals (Sweden)

    A. Żydek

    2011-04-01

    Full Text Available Mg-5Al-0.4Mn-xRE (x = 0, 1, 2, 3 wt.% magnesium alloys were prepared successfully by casting method. The microstructure wasinvestigated by light microscopy. The influence of rare earth (RE elements on the area fraction of eutectic was analysed. The obtainedresults revealed that the as-cast Mg-5Al-0.4Mn alloy consist of α - Mg matrix and eutectic α + γ (where γ is Mg17Al12. However, whilerare earth elements were added to the Mg-Al type alloy, Al11RE3 precipitates were formed. The amount of the Al11RE3 precipitatesincreased with increasing addition of RE, but the amount of γ - Mg17Al12 decreased.

  12. Evolution of planetary cores and the Earth-Moon system from Nb/Ta systematics.

    Science.gov (United States)

    Münker, Carsten; Pfänder, Jörg A; Weyer, Stefan; Büchl, Anette; Kleine, Thorsten; Mezger, Klaus

    2003-07-04

    It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 +/- 0.3) and the Moon (17.0 +/- 0.8) are below the chondritic ratio of 19.9 +/- 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.

  13. Uderstanding Snowball Earth Deglaciation

    Science.gov (United States)

    Abbot, D. S.

    2012-12-01

    Earth, a normally clement planet comfortably in its star's habitable zone, suffered global or nearly global glaciation at least twice during the Neoproterozoic era (at about 635 and 710 million years ago). Viewed in the context of planetary evolution, these pan-global glaciations (Snowball Earth events) were extremely rapid, lasting only a few million years. The dramatic effect of the Snowball Earth events on the development of the planet can be seen through their link to rises in atmospheric oxygen and evolutionary innovations. These potential catastrophes on an otherwise clement planet can be used to gain insight into planetary habitability more generally. Since Earth is not currently a Snowball, a sound deglaciation mechanism is crucial for the viability of the Snowball Earth hypothesis. The traditional deglaciation mechanism is a massive build up of CO2 due to reduced weathering during Snowball Earth events until tropical surface temperatures reach the melting point. Once initiated, such a deglaciation might happen on a timescale of only dozens of thousands of years and would thrust Earth from the coldest climate in its history to the warmest. Therefore embedded in Snowball Earth events is an even more rapid and dramatic environmental change. Early global climate model simulations raised doubt about whether Snowball Earth deglaciation could be achieved at a CO2 concentration low enough to be consistent with geochemical data, which represented a potential challenge to the Snowball Earth hypothesis. Over the past few years dust and clouds have emerged as the essential missing additional processes that would allow Snowball Earth deglaciation at a low enough CO2 concentration. I will discuss the dust and cloud mechanisms and the modeling behind these ideas. This effort is critical for the broader implications of Snowball Earth events because understanding the specific deglaciation mechanism determines whether similar processes could happen on other planets.

  14. NASA's Evolution to Ka-Band Space Communications for Near-Earth Spacecraft

    Science.gov (United States)

    McCarthy, Kevin; Stocklin, Frank; Geldzahler, Barry; Friedman, Daniel; Celeste, Peter

    2010-01-01

    This slide presentation reviews the exploration of NASA using a Ka-band system for spacecraft communications in Near-Earth orbits. The reasons for changing to Ka-band are the higher data rates, and the current (X-band spectrum) is becoming crowded. This will require some modification to the current ground station antennas systems. The results of a Request for Information (RFI) are discussed, and the recommended solution is reviewed.

  15. Weathering Pathways and Limitations in Biogeochemical Models: Application to Earth System Evolution

    OpenAIRE

    Mills, Benjamin

    2012-01-01

    Current biogeochemical box models for Phanerozoic climate are reviewed and reduced to a robust, modular system, allowing application to the Precambrian. It is shown that stabilisation of climate following a Neoproterozoic snowball Earth should take more than 10(7) years, due to long-term geological limitation of global weathering rates. The timescale matches the observed gaps between extreme glaciations at this time, suggesting that the late Neoproterozoic system was oscillating around a s...

  16. A planetary perspective on Earth evolution: Lid Tectonics before Plate Tectonics

    Science.gov (United States)

    Piper, John D. A.

    2013-03-01

    Plate Tectonics requires a specific range of thermal, fluid and compositional conditions before it will operate to mobilise planetary lithospheres. The response to interior heat dispersion ranges from mobile lids in constant motion able to generate zones of subduction and spreading (Plate Tectonics), through styles of Lid Tectonics expressed by stagnant lids punctured by volcanism, to lids alternating between static and mobile. The palaeomagnetic record through Earth history provides a test for tectonic style because a mobile Earth of multiple continents is recorded by diverse apparent polar wander paths, whilst Lid Tectonics is recorded by conformity to a single position. The former is difficult to isolate without extreme selection whereas the latter is a demanding requirement and easily recognised. In the event, the Precambrian palaeomagnetic database closely conforms to this latter property over very long periods of time (~ 2.7-2.2 Ga, 1.5-1.3 Ga and 0.75-0.6 Ga); intervening intervals are characterised by focussed loops compatible with episodes of true polar wander stimulated by disturbances to the planetary figure. Because of this singular property, the Precambrian palaeomagnetic record is highly effective in showing that a dominant Lid Tectonics operated throughout most of Earth history. A continental lid comprising at least 60% of the present continental area and volume had achieved quasi-integrity by 2.7 Ga. Reconfiguration of mantle and continental lid at ~ 2.2 Ga correlates with isotopic signatures and the Great Oxygenation Event and is the closest analogy in Earth history to the resurfacing of Venus. Change from Lid Tectonics to Plate Tectonics is transitional and the geological record identifies incipient development of Plate Tectonics on an orogenic scale especially after 1.1 Ga, but only following break-up of the continental lid (Palaeopangaea) in Ediacaran times beginning at ~ 0.6 Ga has it become comprehensive in the style evident during the

  17. Changes in the manner of tectonic movements under the Earth's evolution

    Science.gov (United States)

    Kuzmin, M. I.; Yarmolyuk, V. V.

    2016-08-01

    Variations in the O, Sr, Nd, and Hf isotopic compositions in rocks of various ages, minerals, and mantle temperature in the geological history are considered. Two periods in the Earth's history are studied: the beginning of the formation of the planet until the turn of (3.4) 2.7-2.5 Ga and the tectonic movement period in the last 2 Ga, and also the transitional period within 2.7-2.0 Ga.

  18. A warm or a cold early Earth? New insights from a 3-D climate-carbon model

    Science.gov (United States)

    Charnay, Benjamin; Le Hir, Guillaume; Fluteau, Frédéric; Forget, François; Catling, David C.

    2017-09-01

    Oxygen isotopes in marine cherts have been used to infer hot oceans during the Archean with temperatures between 60 °C (333 K) and 80 °C (353 K). Such climates are challenging for the early Earth warmed by the faint young Sun. The interpretation of the data has therefore been controversial. 1D climate modeling inferred that such hot climates would require very high levels of CO2 (2-6 bars). Previous carbon cycle modeling concluded that such stable hot climates were impossible and that the carbon cycle should lead to cold climates during the Hadean and the Archean. Here, we revisit the climate and carbon cycle of the early Earth at 3.8 Ga using a 3D climate-carbon model. We find that CO2 partial pressures of around 1 bar could have produced hot climates given a low land fraction and cloud feedback effects. However, such high CO2 partial pressures should not have been stable because of the weathering of terrestrial and oceanic basalts, producing an efficient stabilizing feedback. Moreover, the weathering of impact ejecta during the Late Heavy Bombardment (LHB) would have strongly reduced the CO2 partial pressure leading to cold climates and potentially snowball Earth events after large impacts. Our results therefore favor cold or temperate climates with global mean temperatures between around 8 °C (281 K) and 30 °C (303 K) and with 0.1-0.36 bar of CO2 for the late Hadean and early Archean. Finally, our model suggests that the carbon cycle was efficient for preserving clement conditions on the early Earth without necessarily requiring any other greenhouse gas or warming process.

  19. Titration of the Earth: Ocean-Atmosphere Evolution Recorded in Marine Carbonates

    Science.gov (United States)

    Kah, L. C.

    2012-12-01

    The enzymatic production of carbonate biominerals marks a clear association between biological processes and carbonate mineral formation. Prior to the evolution of skeletonizing metazoans, however, biotic activity played a less critical role in the morphological development of carbonate minerals. Instead, carbonate mineral morphology was more strongly affected by abiotic parameters that affect carbonate nucleation and growth. The texture of non-enzymatically controlled carbonate precipitation in the Precambrian may therefore provide us with an additional window through which to observe fundamental changes in the chemical evolution of the global ocean. The Precambrian ocean experienced a progressive evolution from CO2-rich and O2-poor, to CO2-poor and O2-rich. Changes in CO2-availability fundamentally affect marine carbonate saturation state, which is reflected primarily in the rate of crystal growth. By contrast, redox evolution appears to have played a fundamental role in regulating carbonate precipitation via the differential inhibition of mineral nucleation. Carbonate mineral textures that indicate differential nucleation and growth can be traced both spatially and temporally in the Precambrian sedimentary record. Textures that are dominated by high rates of growth relative to nucleation are common in Archean, and become progressively restricted in their distribution by the latter Proterozoic. Spatial restriction, particularly of fabrics associated with redox-controlled nucleation, suggesting the development of chemically discrete oceanic environments. Such observations are consistent with recent models of suggesting that ocean oxygenation occurred in a top-down fashion, with well-oxygenated surface waters underlain by either anoxic deep-waters or oxygen-depleted substrate pore-waters. Deciphering relationships among these environments permits attribution of carbonate fabrics to specific geochemical conditions within the water column and provides critical

  20. Replicating the Ice-Volume Signal of the Early Pleistocene with a Complex Earth System Model

    Science.gov (United States)

    Tabor, C. R.; Poulsen, C. J.; Pollard, D.

    2013-12-01

    Milankovitch theory proposes high-latitude summer insolation intensity paces the ice ages by controlling perennial snow cover amounts (Milankovitch, 1941). According to theory, the ~21 kyr cycle of precession should dominate the ice-volume records since it has the greatest influence on high-latitude summer insolation. Modeling experiments frequently support Milankovitch theory by attributing the majority of Northern Hemisphere high-latitude summer snowmelt to changes in the cycle of precession (e.g. Jackson and Broccoli, 2003). However, ice-volume proxy records, especially those of the Early Pleistocene (2.6-0.8 Ma), display variability with a period of ~41 kyr (Raymo and Lisiecki, 2005), indicative of insolation forcing from obliquity, which has a much smaller influence on summer insolation intensity than precession. Several hypotheses attempt to explain the discrepancies between Milkankovitch theory and the proxy records by invoking phenomena such as insolation gradients (Raymo and Nisancioglu, 2003), hemispheric offset (Raymo et al., 2006; Lee and Poulsen, 2009), and integrated summer energy (Huybers, 2006); however, all of these hypotheses contain caveats (Ruddiman, 2006) and have yet to be supported by modeling studies that use a complex GCM. To explore potential solutions to this '41 kyr problem,' we use an Earth system model composed of the GENESIS GCM and Land Surface model, the BIOME4 vegetation model, and the Pennsylvania State ice-sheet model. Using an asynchronous coupling technique, we run four idealized transient combinations of obliquity and precession, representing the orbital extremes of the Pleistocene (Berger and Loutre, 1991). Each experiment is run through several complete orbital cycles with a dynamic ice domain spanning North America and Greenland, and fixed preindustrial greenhouse-gas concentrations. For all orbital configurations, model results produce greater ice-volume spectral power at the frequency of obliquity despite significantly

  1. Accretion in the Early Kuiper Belt; 1, Coagulation and Velocity Evolution

    CERN Document Server

    Kenyon, S J; Kenyon, Scott J.; Luu, Jane X.

    1998-01-01

    We describe planetesimal accretion calculations in the Kuiper Belt. Our evolution code simulates planetesimal growth in a single annulus and includes velocity evolution but not fragmentation. Test results match analytic solutions and duplicate previous simulations at 1 AU. In the Kuiper Belt, simulations without velocity evolution produce a single runaway body with a radius of 1000 km on a time scale inversely proportional to the initial mass in the annulus. Runaway growth occurs in 100 Myr for 10 earth masses and an initial eccentricity of 0.001 in a 6 AU annulus centered at 35 AU. This mass is close to the amount of dusty material expected in a minimum mass solar nebula extrapolated into the Kuiper Belt. Simulations with velocity evolution produce runaway growth on a wide range of time scales. Dynamical friction and viscous stirring increase particle velocities in models with large (8 km radius) initial bodies. This velocity increase delays runaway growth by a factor of two compared to models without veloci...

  2. Evolution of CO2 and H2O on Mars: A cold Early History?

    Science.gov (United States)

    Niles, P. B.; Michalski, J.

    2011-01-01

    The martian climate has long been thought to have evolved substantially through history from a warm and wet period to the current cold and dry conditions on the martian surface. This view has been challenged based primarily on evidence that the early Sun had a substantially reduced luminosity and that a greenhouse atmosphere would be difficult to sustain on Mars for long periods of time. In addition, the evidence for a warm, wet period of martian history is far from conclusive with many of the salient features capable of being explained by an early cold climate. An important test of the warm, wet early Mars hypothesis is the abundance of carbonates in the crust [1]. Recent high precision isotopic measurements of the martian atmosphere and discoveries of carbonates on the martian surface provide new constraints on the evolution of the martian atmosphere. This work seeks to apply these constraints to test the feasibility of the cold early scenario

  3. Early-late life trade-offs and the evolution of ageing in the wild.

    Science.gov (United States)

    Lemaître, Jean-François; Berger, Vérane; Bonenfant, Christophe; Douhard, Mathieu; Gamelon, Marlène; Plard, Floriane; Gaillard, Jean-Michel

    2015-05-07

    Empirical evidence for declines in fitness components (survival and reproductive performance) with age has recently accumulated in wild populations, highlighting that the process of senescence is nearly ubiquitous in the living world. Senescence patterns are highly variable among species and current evolutionary theories of ageing propose that such variation can be accounted for by differences in allocation to growth and reproduction during early life. Here, we compiled 26 studies of free-ranging vertebrate populations that explicitly tested for a trade-off between performance in early and late life. Our review brings overall support for the presence of early-late life trade-offs, suggesting that the limitation of available resources leads individuals to trade somatic maintenance later in life for high allocation to reproduction early in life. We discuss our results in the light of two closely related theories of ageing-the disposable soma and the antagonistic pleiotropy theories-and propose that the principle of energy allocation roots the ageing process in the evolution of life-history strategies. Finally, we outline research topics that should be investigated in future studies, including the importance of natal environmental conditions in the study of trade-offs between early- and late-life performance and the evolution of sex-differences in ageing patterns. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  4. Phylogenetic ctDNA analysis depicts early stage lung cancer evolution

    OpenAIRE

    Wilson, Gareth A.; Constantin, Tudor; Quesne, John Le; Moore, David A.; Kirkizlar, Eser; Fraioli, Francesco; Bakir, Maise Al; Zambrana, Francisco; Endozo, Raymondo; Bi, Wenya Linda; Fennessy, Fiona M.; Forster, Martin D.; Hafez, Dina; Ganguly, Apratim; Kareht, Stephanie

    2017-01-01

    The early detection of relapse following primary surgery for non-small cell lung cancer and the characterization of emerging subclones seeding metastatic sites might offer new therapeutic approaches to limit tumor recurrence. The potential to non-invasively track tumor evolutionary dynamics in ctDNA of early-stage lung cancer is not established. Here we conduct a tumour-specific phylogenetic approach to ctDNA profiling in the first 100 TRACERx (TRAcking non-small cell lung Cancer Evolution th...

  5. A continued role for signaling functions in the early evolution of feathers.

    Science.gov (United States)

    Ruxton, Graeme D; Persons Iv, W Scott; Currie, Philip J

    2017-03-01

    Persons and Currie (2015) argued against either flight, thermoregulation, or signaling as a functional benefit driving the earliest evolution of feathers; rather, they favored simple feathers having an initial tactile sensory function, which changed to a thermoregulatory function as density increased. Here, we explore the relative merits of early simple feathers that may have originated as tactile sensors progressing instead toward a signaling, rather than (or in addition to) a thermoregulatory function. We suggest that signaling could act in concert with a sensory function more naturally than could thermoregulation. As such, the dismissal of a possible signaling function and the presumption that an initial sensory function led directly to a thermoregulatory function (implicit in the title "bristles before down") are premature. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  6. Phylogenetic position of sponges in early metazoan evolution and bionic applications of siliceous sponge spicules

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Sponges are the oldest and the simplest but not primitive multicellular animals. They represent the earliest evolutionary metazoan phylum still extant. It was a long and painful scientific process to position the most enigmatic and mysterious metazoan, the Porifera, into their correct phylogenetic place among the eukaryotes in general and multicellular animals in particular. As living fossils, sponges provide the best evidence for the early evolution of Metazoa. More recently, interest has been focused on the bionic applications of sponges' siliceous spicules, after the discovery of their unique structure and high fiber performance. In this review, the emergence of sponges, evolutionary novelties found in sponges, and the phylogenetic position of sponges in early metazoan evolution are highlighted. In addition, the pre-sent state of knowledge on silicatein-mediated "biosilica" formation in marine sponges, including the involvement of other molecules in silica metabolism and their potential application in nanobiotechnol-ogy and medicine, is given.

  7. The Evolution of Field Early-Type Galaxies in the FDF and WHDF

    CERN Document Server

    Fritz, Alexander; Ziegler, Bodo L

    2009-01-01

    We explore the properties of 24 field early-type galaxies at 0.20=-0.74\\pm0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5 Gyr, that gets support by recent studies of field galaxies up to z~1. Independent evidence for recent SF activity is provided by spectroscopic (OII em., Hdelta) and photometric (rest-frame colors) diagnostics. Based on the Hdelta absorption feature we detect a weak residual SF for galaxies that acco unts for 5%-10% in the total stellar mass of these galaxies. The co-evolution in the luminosity and mass of our galaxies favours a downsizing formation process. We find some evidence that our galaxies experienced a period of SF quenching, possible triggered by AGN activity that is in good agreement with recent results on both observational and theoretical side. (abridged)

  8. Early Thermal Evolution of Planetesimals and its Impact on Processing and Dating of Meteoritic Material

    CERN Document Server

    Gail, H -P; Breuer, D; Spohn, T

    2013-01-01

    Radioisotopic ages for meteorites and their components provide constraints on the evolution of small bodies: timescales of accretion, thermal and aqueous metamorphism, differentiation, cooling and impact metamorphism. Realising that the decay heat of short-lived nuclides (e.g. 26Al, 60Fe), was the main heat source driving differentiation and metamorphism, thermal modeling of small bodies is of utmost importance to set individual meteorite age data into the general context of the thermal evolution of their parent bodies, and to derive general conclusions about the nature of planetary building blocks in the early solar system. As a general result, modelling easily explains that iron meteorites are older than chondrites, as early formed planetesimals experienced a higher concentration of short-lived nuclides and more severe heating. However, core formation processes may also extend to 10 Ma after formation of Calcium-Aluminum-rich inclusions (CAIs). A general effect of the porous nature of the starting material ...

  9. The redshift evolution of early-type galaxies in COSMOS: Do massive early-type galaxies form by dry mergers?

    CERN Document Server

    Scarlata, C; Lilly, S J; Feldmann, R; Kampczyk, P; Renzini, A; Cimatti, A; Halliday, C; Daddi, E; Sargent, M T; Koekemoer, A; Scoville, N; Kneib, J P; Leauthaud, A; Massey, R; Rhodes, J; Tasca, L; McCracken, H J; Mobasher, B; Taniguchi, Y; Thompson, D; Ajiki, M; Aussel, H; Murayama, T; Sanders, D B; Sasaki, S; Shioya, Y; Takahashi, M

    2007-01-01

    ABRIDGED: We study the evolution since z~1 of the rest-frame B luminosity function of the early-type galaxies (ETGs) in ~0.7 deg^2 in the COSMOS field. In order to identify ALL progenitors of local ETGs we construct the sample of high-z galaxies using two complementary criteria: (i) A morphological selection based on the Zurich Estimator of Structural Types, and (ii) A photometric selection based on the galaxy properties in the (U-V)-M_V color-magnitude diagram. We furthermore constrain both samples so as to ensure that the selected progenitors of ETGs are compatible with evolving into systems which obey the mu_B-r_{hl} Kormendy relation. Assuming the luminosity evolution derived from studies of the fundamental plane for high-z ETGs, our analysis shows no evidence for a decrease in the number density of the most massive ETGs out to z~ 0.7: Both the morphologically- and the photometrically-selected sub-samples show no evolution in the number density of bright (~L>2.5L*) ETGs. Allowing for different star format...

  10. Life: Origin and evolution on Earth--How can we escape?

    Science.gov (United States)

    Markert, Clement L.; Krikorian, Abraham D.

    1993-01-01

    Exploitation of gene regulation rather than the creation of new genes has been predominantly responsible for the evolutionary advances in animals and plants that are widely recognized today. Until very recently it was not possible to examine life in the absence of gravity. We can now imagine forms of life in the universe adapting to circumstances different from those found on Earth. Our own life forms would surely become different in time if they were transferred to other planets with different conditions, including much lower or higher gravity.

  11. Geochronology and geochemistry of Early Jurassic volcanic rocks in the Erguna Massif, northeast China: Petrogenesis and implications for the tectonic evolution of the Mongol-Okhotsk suture belt

    Science.gov (United States)

    Wang, Wei; Tang, Jie; Xu, Wen-Liang; Wang, Feng

    2015-03-01

    The Mongol-Okhotsk suture belt played an important role in the tectonic evolution of northeast Asia during the Mesozoic. However, few studies have examined the influence of this tectonic belt on the geological evolution of northeast China. In this paper, we present zircon U-Pb geochronology, major and trace element geochemistry, and zircon Hf-O isotopic data for Early Jurassic volcanic rocks in the Erguna Massif of northeast China, with the aim of constraining the evolution of the Mongol-Okhotsk suture belt and its influence on the tectonic history of China during the Early Jurassic. Zircon U-Pb dating indicates that the trachybasalt and basaltic andesite in the study area were erupted between 193 ± 5 Ma and 181 ± 9 Ma (i.e., in the Early Jurassic). These Early Jurassic volcanic rocks belong to the high-K calc-alkaline series and are enriched in large ion lithophile elements and light rare earth elements, as well as being depleted in heavy rare earth elements and high field strength elements such as Nb and Ta. The rocks show a small negative Eu anomaly. The zircon εHf (182 Ma) values of the volcanic rocks range from - 1.9 to + 5.1, corresponding to TDM1 values of 640-901 Ma and TDM2 values of 901-1345 Ma. Zircons from two volcanic rocks yield δ18O values of 7.2‰ ± 1.5‰ (n = 19) and 6.6‰ ± 0.7‰ (n = 35). Geochemically, these Early Jurassic volcanic rocks are similar to those from active continental margin settings, and their primary magmas could have been derived from the partial melting of a lithospheric mantle wedge modified by fluid from a subducted slab. The discovery of Early Jurassic calc-alkaline volcanic rocks in the Erguna Massif, together with the coeval porphyry Cu-Mo deposits, indicates that an active continental margin existed in the Erguna area during the Early Jurassic. Taken together, we conclude that southward subduction of the Mongol-Okhotsk oceanic plate took place beneath the Erguna Massif during the Early Jurassic.

  12. Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda

    OpenAIRE

    Yang, Jie; Ortega-Hernández, Javier; Butterfield, Nicholas J.; Liu, Yu; Boyan, George S.; Hou, Jin-bo; Lan, Tian; Zhang, Xi-guang

    2016-01-01

    Understanding the evolution of the CNS is fundamental for resolving the phylogenetic relationships within Panarthropoda (Euarthropoda, Tardigrada, Onychophora). The ground pattern of the panarthropod CNS remains elusive, however, as there is uncertainty on which neurological characters can be regarded as ancestral among extant phyla. Here we describe the ventral nerve cord (VNC) in Chengjiangocaris kunmingensis, an early Cambrian euarthropod from South China. The VNC reveals extraordinary det...

  13. The early stage of bacterial genome-reductive evolution in the host.

    Directory of Open Access Journals (Sweden)

    Han Song

    2010-05-01

    Full Text Available The equine-associated obligate pathogen Burkholderia mallei was developed by reductive evolution involving a substantial portion of the genome from Burkholderia pseudomallei, a free-living opportunistic pathogen. With its short history of divergence (approximately 3.5 myr, B. mallei provides an excellent resource to study the early steps in bacterial genome reductive evolution in the host. By examining 20 genomes of B. mallei and B. pseudomallei, we found that stepwise massive expansion of IS (insertion sequence elements ISBma1, ISBma2, and IS407A occurred during the evolution of B. mallei. Each element proliferated through the sites where its target selection preference was met. Then, ISBma1 and ISBma2 contributed to the further spread of IS407A by providing secondary insertion sites. This spread increased genomic deletions and rearrangements, which were predominantly mediated by IS407A. There were also nucleotide-level disruptions in a large number of genes. However, no significant signs of erosion were yet noted in these genes. Intriguingly, all these genomic modifications did not seriously alter the gene expression patterns inherited from B. pseudomallei. This efficient and elaborate genomic transition was enabled largely through the formation of the highly flexible IS-blended genome and the guidance by selective forces in the host. The detailed IS intervention, unveiled for the first time in this study, may represent the key component of a general mechanism for early bacterial evolution in the host.

  14. On the Chemical Evolution of Upper Mantle of the Early Earth—An Experimental Study on Melting of the Silicate Phase in Jilin Chondrite at High Pressures

    Institute of Scientific and Technical Information of China (English)

    谢鸿森; 方虹; 等

    1989-01-01

    Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.

  15. Is lithostatic loading important for the slip behavior and evolution of normal faults in the Earth's crust?

    Energy Technology Data Exchange (ETDEWEB)

    Kattenhorn, Simon A. [Department of Geological and Environmental Sciences, Stanford University, Stanford, California (United States); Pollard, David D. [Department of Geological and Environmental Sciences, Stanford University, Stanford, California (United States)

    1999-12-10

    Normal faults growing in the Earth's crust are subject to the effects of an increasing frictional resistance to slip caused by the increasing lithostatic load with depth. We use three-dimensional (3-D) boundary element method numerical models to evaluate these effects on planar normal faults with variable elliptical tip line shapes in an elastic solid. As a result of increasing friction with depth, normal fault slip maxima for a single slip event are skewed away from the fault center toward the upper fault tip. There is a correspondingly greater propagation tendency at the upper tip. However, the tall faults that would result from such a propagation tendency are generally not observed in nature. We show how mechanical interaction between laterally stepping fault segments significantly competes with the lithostatic loading effect in the evolution of a normal fault system, promoting lateral propagation and possibly segment linkage. Resultant composite faults are wider than they are tall, resembling both 3-D seismic data interpretations and previously documented characteristics of normal fault systems. However, this effect may be greatly complemented by the influence of a heterogeneous stratigraphy, which can control fault nucleation depth and inhibit fault propagation across the mechanical layering. Our models demonstrate that although lithostatic loading may be an important control on fault evolution in relatively homogeneous rocks, the contribution of lithologic influences and mechanical interaction between closely spaced, laterally stepping faults may predominate in determining the slip behavior and propagation tendency of normal faults in the Earth's crust. (c) 1999 American Geophysical Union.

  16. Deep mantle heat flow and thermal evolution of the Earth's core based on thermo-chemical mantle convection

    Science.gov (United States)

    Nakagawa, T.; Tackley, P.; Buffett, B.

    2004-12-01

    A coupled core-mantle evolution model that combines the global heat balance in the core with a fully-dynamical thermo-chemical mantle convection [Nakagawa and Tackley, 2004 published in EPSL] is used to investigate the deep mantle heat flow that is required to sustain the magnetic field generated by the geodynamo process. Effects of a radioactive heat source due to potassium in the core are also included in the global heat balance in the Earth??s core. Two important parameters are checked in this study; (1) density variation between depleted hartzbergite and basaltic material (0 to 3 percent) and (2) concentration of radioactive potassium in the core alloy (0ppm to 400ppm). The parameter set that most closely satisfies the criteria of size of the inner core (1220km at present time) is around 2 percent of density difference in a convecting mantle and 200ppm of radioactive heat source in the core. The concentration of potassium in the core is consistent with the geochemical approach [Murthy et al., 2003] but smaller than other successful thermal evolution models [Labrosse, 2003; Nimmo et al., 2004]. Heat flow through the core-mantle boundary and the contribution of radioactive heat sources in the core are consistent with theoretical estimates [e.g. Buffett, 2002] and geochemical constraints [Gessmann and Wood, 2002]. The power available to the geodynamo, based on the predicted heat flow through the core-mantle boundary, is approximately four times greater than the value predicted by numerical models of the geodynamo [Christensen and Kutzner, 2004] but closer to theoretical estimates [e.g. Buffett, 2002].

  17. Properties and evolution of NEO families created by tidal disruption at Earth

    CERN Document Server

    Schunová, Eva; Walsh, Kevin J; Granvik, Mikael; Wainscoat, Richard J; Haghighipour, Nader

    2014-01-01

    We have calculated the coherence and detectable lifetimes of synthetic near-Earth object (NEO) families created by catastrophic disruption of a progenitor as it suffers a very close Earth approach. The closest or slowest approaches yield the most violent `s-class' disruption events. We found that the average slope of the absolute magnitude (H) distribution, $N(H)\\propto10^{(0.55\\pm0.04)\\,H}$, for the fragments in the s-class families is steeper than the slope of the NEO population \\citep{mainzer2011} in the same size range. The families remain coherent as statistically significant clusters of orbits within the NEO population for an average of $\\bar\\tau_c = (14.7\\pm0.6)\\times10^3$ years after disruption. The s-class families are detectable with the techniques developed by \\citet{fu2005} and \\citet{Schunova2012} for an average duration ($\\bar\\tau_{det}$) ranging from about 2,000 to about 12,000 years for progenitors in the absolute magnitude ($H_p$) range from 20 to 13 corresponding to diameters in the range fr...

  18. Comets as Messengers from the Early Solar System - Emerging Insights on Delivery of Water, Nitriles, and Organics to Earth

    Science.gov (United States)

    Mumma, Michael J.; Charnley, Steven B.

    2012-01-01

    The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's volatiles, and for assessing the possible existence of exo-planets similar to Earth. Viewed from a cosmic perspective, Earth is a dry planet, yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen and analogous isotopic enrichments in atmospheric nitrogen and noble gases are also seen. Why is this so? What are the implications for Mars? For icy Worlds in our Planetary System? For the existence of Earth-like exoplanets? An exogenous (vs. outgassed) origin for Earth's atmosphere is implied, and intense debate on the relative contributions of comets and asteroids continues - renewed by fresh models for dynamical transport in the protoplanetary disk, by revelations on the nature and diversity of volatile and rocky material within comets, and by the discovery of ocean-like water in a comet from the Kuiper Belt (cf., Mumma & Charnley 2011). Assessing the creation of conditions favorable to the emergence and sustenance of life depends critically on knowledge of the nature of the impacting bodies. Active comets have long been grouped according to their orbital properties, and this has proven useful for identifying the reservoir from which a given comet emerged (OC, KB) (Levison 1996). However, it is now clear that icy bodies were scattered into each reservoir from a range of nebular distances, and the comet populations in today's reservoirs thus share origins that are (in part) common. Comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition, resulting from strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models of early radial transport and mixing with later dispersion of the final cometary nuclei into the long-term storage reservoirs. The inclusion of material from the natal interstellar cloud is probable

  19. The evolution of Earth Observation satellites in Europe and its impact on the performance of emergency response services

    Science.gov (United States)

    Denis, Gil; de Boissezon, Hélène; Hosford, Steven; Pasco, Xavier; Montfort, Bruno; Ranera, Franck

    2016-10-01

    The paper reviews the evolution of Earth Observation systems in Europe and Worldwide and analyses the potential impact of their performance in support of emergency response services. Earth Observation satellites play already a significant role in supporting the action of first responders in case of major disasters. The main principle is the coordinated use of satellites in order to ensure a rapid response and the timely delivery of images and geospatial information of the area affected by the event. The first part of the paper reviews the main instruments and evaluates their current performance. The International Charter "Space and Major Disasters", signed in October 2000, was the first international initiative aimed at establishing a unified system for the acquisition of space data. The charter is a cooperation agreement between space agencies and operators of space systems. At regional level, a similar instrument exists in Asia: Sentinel-Asia. In the frame of the European programme Copernicus, the emergency management service was launched in 2009. Geo-information products derived from space imagery are delivered during all phases of the emergency management cycle, in either rush or non-rush mode, free of charge for the users. In both cases, the capacities were historically drawn from national missions, funded with public money and directly operated by the space agencies or by national operators.

  20. Nonlinear evolution of mirror instability in the Earth's magnetosheath in pic simulations

    Science.gov (United States)

    Ahmadi, Narges

    Mirror modes are large amplitude non-propagating structures frequently observed in the magnetosheath and they are generated in space plasma environments with proton temperature anisotropy of larger than one. The proton temperature anisotropy also drives the proton cyclotron instability which has larger linear growth rate than that of the mirror instability. Linear dispersion theory predicts that electron temperature anisotropy can enhance the mirror instability growth rate while leaving the proton cyclotron instability largely unaffected. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than the mirror instability and quickly consumes the electron free energy, so that there is not enough electron temperature anisotropy left to significantly impact the evolution of the mirror instability. Observational studies have shown that the shape of mirror structures is related to local plasma parameters and distance to the mirror instability threshold. Mirror structures in the form of magnetic holes are observed when plasma is mirror stable or marginally mirror unstable and magnetic peaks are observed when plasma is mirror unstable. Mirror structures are created downstream of the quasi-perpendicular bow shock and they are convected toward the magnetopause. In the middle magnetosheath, where plasma is mirror unstable, mirror structures are dominated by magnetic peaks. Close to the magnetopause, plasma expansion makes the region mirror stable and magnetic peaks evolve to magnetic holes. We investigate the nonlinear evolution of mirror instability using expanding box Particle-in-Cell simulations. We change the plasma conditions by artificially enlarging the simulation box over time to make the plasma mirror stable and investigate the final nonlinear state of the mirror structures. We show that the direct nonlinear evolution of the mirror

  1. A Mercury-like component of early Earth yields uranium in the core and high mantle (142)Nd.

    Science.gov (United States)

    Wohlers, Anke; Wood, Bernard J

    2015-04-16

    Recent (142)Nd isotope data indicate that the silicate Earth (its crust plus the mantle) has a samarium to neodymium elemental ratio (Sm/Nd) that is greater than that of the supposed chondritic building blocks of the planet. This elevated Sm/Nd has been ascribed either to a 'hidden' reservoir in the Earth or to loss of an early-formed terrestrial crust by impact ablation. Since removal of crust by ablation would also remove the heat-producing elements--potassium, uranium and thorium--such removal would make it extremely difficult to balance terrestrial heat production with the observed heat flow. In the 'hidden' reservoir alternative, a complementary low-Sm/Nd layer is usually considered to reside unobserved in the silicate lower mantle. We have previously shown, however, that the core is a likely reservoir for some lithophile elements such as niobium. We therefore address the question of whether core formation could have fractionated Nd from Sm and also acted as a sink for heat-producing elements. We show here that addition of a reduced Mercury-like body (or, alternatively, an enstatite-chondrite-like body) rich in sulfur to the early Earth would generate a superchondritic Sm/Nd in the mantle and an (142)Nd/(144)Nd anomaly of approximately +14 parts per million relative to chondrite. In addition, the sulfur-rich core would partition uranium strongly and thorium slightly, supplying a substantial part of the 'missing' heat source for the geodynamo.

  2. Highly stable evolution of Earth's future orbit despite chaotic behavior of the Solar System

    CERN Document Server

    Zeebe, Richard E

    2015-01-01

    Due to the chaotic nature of the Solar System, the question of its dynamic long-term stability can only be answered in a statistical sense, e.g. based on numerical ensemble integrations of nearby orbits. Destabilization, including catastrophic encounters and/or collisions involving the Earth, has been suggested to be initiated through a large increase in Mercury's eccentricity (eM), with an estimated probability of ~1%. However, it has recently been shown that the statistics of numerical Solar System integrations are sensitive to the accuracy and type of numerical algorithm. Here I report results from computationally demanding ensemble integrations (N=1,600 with slightly different initial conditions) at unprecedented accuracy based on the full equations of motion of the eight planets and Pluto over 5Gyr, including contributions from general relativity. The standard symplectic algorithm produced spurious results for highly eccentric orbits and during close encounters, which were hence integrated with a suitabl...

  3. Human factors dimensions in the evolution of increasingly automated control rooms for near-earth satellites

    Science.gov (United States)

    Mitchell, C. M.

    1982-01-01

    The NASA-Goddard Space Flight Center is responsible for the control and ground support for all of NASA's unmanned near-earth satellites. Traditionally, each satellite had its own dedicated mission operations room. In the mid-seventies, an integration of some of these dedicated facilities was begun with the primary objective to reduce costs. In this connection, the Multi-Satellite Operations Control Center (MSOCC) was designed. MSOCC represents currently a labor intensive operation. Recently, Goddard has become increasingly aware of human factors and human-machine interface issues. A summary is provided of some of the attempts to apply human factors considerations in the design of command and control environments. Current and future activities with respect to human factors and systems design are discussed, giving attention to the allocation of tasks between human and computer, and the interface for the human-computer dialogue.

  4. Human factors dimensions in the evolution of increasingly automated control rooms for near-earth satellites

    Science.gov (United States)

    Mitchell, C. M.

    1982-01-01

    The NASA-Goddard Space Flight Center is responsible for the control and ground support for all of NASA's unmanned near-earth satellites. Traditionally, each satellite had its own dedicated mission operations room. In the mid-seventies, an integration of some of these dedicated facilities was begun with the primary objective to reduce costs. In this connection, the Multi-Satellite Operations Control Center (MSOCC) was designed. MSOCC represents currently a labor intensive operation. Recently, Goddard has become increasingly aware of human factors and human-machine interface issues. A summary is provided of some of the attempts to apply human factors considerations in the design of command and control environments. Current and future activities with respect to human factors and systems design are discussed, giving attention to the allocation of tasks between human and computer, and the interface for the human-computer dialogue.

  5. The minimal kinome of Giardia lamblia illuminates early kinase evolution and unique parasite biology

    Science.gov (United States)

    2011-01-01

    Background The major human intestinal pathogen Giardia lamblia is a very early branching eukaryote with a minimal genome of broad evolutionary and biological interest. Results To explore early kinase evolution and regulation of Giardia biology, we cataloged the kinomes of three sequenced strains. Comparison with published kinomes and those of the excavates Trichomonas vaginalis and Leishmania major shows that Giardia's 80 core kinases constitute the smallest known core kinome of any eukaryote that can be grown in pure culture, reflecting both its early origin and secondary gene loss. Kinase losses in DNA repair, mitochondrial function, transcription, splicing, and stress response reflect this reduced genome, while the presence of other kinases helps define the kinome of the last common eukaryotic ancestor. Immunofluorescence analysis shows abundant phospho-staining in trophozoites, with phosphotyrosine abundant in the nuclei and phosphothreonine and phosphoserine in distinct cytoskeletal organelles. The Nek kinase family has been massively expanded, accounting for 198 of the 278 protein kinases in Giardia. Most Neks are catalytically inactive, have very divergent sequences and undergo extensive duplication and loss between strains. Many Neks are highly induced during development. We localized four catalytically active Neks to distinct parts of the cytoskeleton and one inactive Nek to the cytoplasm. Conclusions The reduced kinome of Giardia sheds new light on early kinase evolution, and its highly divergent sequences add to the definition of individual kinase families as well as offering specific drug targets. Giardia's massive Nek expansion may reflect its distinctive lifestyle, biphasic life cycle and complex cytoskeleton. PMID:21787419

  6. POLARIZATION EVOLUTION OF EARLY OPTICAL AFTERGLOWS OF GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Mi-Xiang; Dai, Zi-Gao [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Wu, Xue-Feng, E-mail: dzg@nju.edu.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2016-01-10

    The central engine and jet composition of gamma-ray bursts (GRBs) remain mysterious. Here we suggest that observations on the polarization evolution of early optical afterglows may shed light on these questions. We first study the dynamics of a reverse shock and a forward shock that are generated during the interaction of a relativistic jet and its ambient medium. The jet is likely magnetized with a globally large-scale magnetic field from the central engine. The existence of the reverse shock requires that the magnetization degree of the jet should not be high (σ ≤ 1), so that the jet is mainly composed of baryons and leptons. We then calculate the light curves and polarization evolution of early optical afterglows and find that when the polarization position angle changes by 90° during the early afterglow, the polarization degree is zero for a toroidal magnetic field but is very likely to be nonzero for an aligned magnetic field. This result would be expected to provide a probe for the central engine of GRBs because an aligned field configuration could originate from a magnetar central engine and a toroidal field configuration could be produced from a black hole via the Blandford–Znajek mechanism. Finally, for such two kinds of magnetic field configurations, we fit the observed data of the early optical afterglow of GRB 120308A equally well.

  7. Ceruloplasmin gene-deficient mice with experimental autoimmune encephalomyelitis show attenuated early disease evolution.

    Science.gov (United States)

    Gresle, Melissa M; Schulz, Katrin; Jonas, Anna; Perreau, Victoria M; Cipriani, Tania; Baxter, Alan G; Miranda-Hernandez, Socorro; Field, Judith; Jokubaitis, Vilija G; Cherny, Robert; Volitakis, Irene; David, Samuel; Kilpatrick, Trevor J; Butzkueven, Helmut

    2014-06-01

    We conducted a microarray study to identify genes that are differentially regulated in the spinal cords of mice with the inflammatory disease experimental autoimmune encephalomyelitis (EAE) relative to healthy mice. In total 181 genes with at least a two-fold increase in expression were identified, and most of these genes were associated with immune function. Unexpectedly, ceruloplasmin (Cp), a ferroxidase that converts toxic ferrous iron to its nontoxic ferric form and also promotes the efflux of iron from astrocytes in the CNS, was shown to be highly upregulated (13.2-fold increase) in EAE spinal cord. Expression of Cp protein is known to be increased in several neurological conditions, but the role of Cp regulation in CNS autoimmune disease is not known. To investigate this, we induced EAE in Cp gene knockout, heterozygous, and wild-type mice. Cp knockout mice were found to have slower disease evolution than wild-type mice (EAE days 13-17; P = 0.05). Interestingly, Cp knockout mice also exhibited a significant increase in the number of astrocytes with reactive morphology in early EAE compared with wild-type mice at the same stage of disease. CNS iron levels were not increased with EAE in these mice. Based on these observations, we propose that an increase in Cp expression could contribute to tissue damage in early EAE. In addition, endogenous CP either directly or indirectly inhibits astrocyte reactivity during early disease, which could also worsen early disease evolution.

  8. 100th anniversary special paper: Sedimentary mineral deposits and the evolution of earth's near-surface environments

    Energy Technology Data Exchange (ETDEWEB)

    Holland, H.D. [Harvard University, Cambridge, MA (United States). Dept. of Earth & Planetary Science

    2005-12-15

    The nature of sedimentary mineral deposits has evolved during Earth's history in concert with changes in the oxidation (redo) state of the ocean-atmosphere system, biological evolution, and the growing importance of geologically young accumulations of ore-grade material. There is now strong evidence that the atmosphere and the oceans were anoxic, or essentially anoxic, before 2.4 Ga. Banded iron formations (BIF) and the detrital uranium ores formed prior to 2.4 Ga are consistent with such a state. The period between 2.4 and 2.0 Ga is called the Great Oxidation Event by some. Its ores bear unmistakable marks of the presence of atmospheric O{sub 2}. Between 1.8 and 0.8 Ga the Earth system seems to have been remarkably stable. Sedimentary ore deposits of this period were influenced by the presence of O{sub 2}. BIF, sedimentary manganese, and phosphorites disappeared ca. 1.8 Ga, but sedimentary exhalative (SEDEX) deposits and unconformity-type uranium deposits flourished, and nonsulfide zinc deposits put in an appearance. The period between 0.8 Ga and the end of the Proterozoic at 0.54 Ga was as turbulent or more so than the Paleoproterozoic. BIF returned, as did sedimentary manganese deposits and phosphorites. A further rise in the O{sub 2} content of the atmosphere and an increase in the sulfate concentration of seawater during this period brought the composition of the atmosphere and of seawater close to their present redox state. The last 540 m.y. of Earth's history have seen the system pass through two supercycles of roughly equal length. Climate, the redox stratification of the oceans ocean mixing, and the nature of sedimentary ores were influenced by tectonically and volcanically driven changes during these supercycles. The evolution of the higher land plants gave rise to coal deposits and sandstone-type uranium ores and was important for the formation of bauxites.

  9. Texture evolution during thermomechanical processing in rare earth free magnesium alloys

    Science.gov (United States)

    Miller, Victoria Mayne

    The use of wrought magnesium alloys is highly desirable for a wide range of applications where low component weight is desirable due to the high specific strength and stiffness the alloys can achieve. However, the implementation of wrought magnesium has been hindered by the limited room temperature formability which typically results from deformation processing. This work identifies opportunities for texture modification during thermomechanical processing of conventional (rare earth free) magnesium alloys via a combination of experimental investigation and polycrystal plasticity simulations. During deformation, it is observed that a homogeneous distribution of coarse intermetallic particles efficiently weakens deformation texture at all strain levels, while a highly inhomogeneous particle distribution is only effective at high strains. The particle deformation effects are complemented by the addition of alkaline earth solute, which modifies the relative deformation mode activity. During recrystallization, grains with basal orientations recrystallize more readily than off-basal grains, despite similar levels of internal misorientation. Dislocation substructure investigations revealed that this is a result of enhanced nucleation in the basal grains due to the dominance of prismatic slip. This dissertation identifies avenues to enhance the potential formability of magnesium alloys during thermomechanical processing by minimizing the evolved texture strength. The following are the identified key aspects of microstructural control: -Maintaining a fine grain size, likely via Zener pinning, to favorably modify deformation mode activity and homogenize deformation. -Developing a coarse, homogeneously distributed population of coarse intermetallic particles to promote a diffuse deformation texture. -Minimizing the activity of prismatic slip to retard the recrystallization of grains with basal orientations, allowing the development of a more diffuse recrystallization texture.

  10. Status and Evolution of the Journal of Astronomy & Earth Science Education's First Year

    Science.gov (United States)

    Slater, Timothy F.

    2016-01-01

    The Journal of Astronomy & Earth Science Education (JAESE.org) is a recently created, peer-reviewed journal designed to serve the discipline-based astronomy, planetary, and geo-sciences education research community. JAESE's first issue was published on December 31, 2014 and has published two volumes and three issues since that time, encompassing 15 peer-reviewed articles. By far, the median article topic has been focused on planetarium education research, while there has only been one article on solid Earth geosciences education research. Although there is not yet an even distribution of topics across the field, there is a relatively even distribution among author demographics. Authors include a range of both junior and senior members of the field. There have been slightly female authors than male authors. Submissions are distributed to two or three reviewers with authors' names redacted from the manuscript. The average time to complete the first round of peer-review reviewers is 6.2-weeks. There have been too few manuscripts to reliably publish a "percentage acceptance rate." Finally, the majority of recently completed astronomy education research doctoral dissertations have been published in JAESE. Taken together, JAESE's guiding Editorial Advisory Board judges this to be a successful first year. In a purposeful effort to make JAESE authors' scholarly works as widely accessible as possible, JAESE adopted an open-access business model. JAESE articles are available to read free-of-charge over the Internet, delivered as PDFs. To date, the most common way articles are downloaded by readers is through Google Scholar. Instead of charging readers and libraries recurring subscription fees, JAESE charges authors a nominal submission fee and a small open-access fee, averaging about $500 USD. These charges are similar to the traditional page charges typically charged to authors or their institutions by scientific journals, making JAESE an attractive publishing venue for

  11. Evolution of an Early Illness Warning System to Monitor Frail Elders in Independent Living

    Directory of Open Access Journals (Sweden)

    Gregory L. Alexander

    2011-01-01

    Full Text Available This paper describes the evolution of an early illness warning system used by an interdisciplinary team composed of clinicians and engineers in an independent living facility. The early illness warning system consists of algorithms which analyze resident activity patterns obtained from sensors embedded in residents' apartments. The engineers designed an automated reasoning system to generate clinically relevant alerts which are sent to clinicians when significant changes occur in the sensor data, for example declining activity levels. During January 2010 through July 2010, clinicians and engineers conducted weekly iterative review cycles of the early illness warning system to discuss concerns about the functionality of the warning system, to recommend solutions for the concerns, and to evaluate the implementation of the solutions. A total of 45 concerns were reviewed during this period. Iterative reviews resulted in greater efficiencies and satisfaction for clinician users who were monitoring elder activity patterns.

  12. New hominin fossils from Kanapoi, Kenya, and the mosaic evolution of canine teeth in early hominins

    Directory of Open Access Journals (Sweden)

    J. Michael Plavcan

    2012-03-01

    Full Text Available Whilst reduced size, altered shape and diminished sexual dimorphism of the canine–premolar complex are diagnostic features of the hominin clade, little is known about the rate and timing of changes in canine size and shape in early hominins. The earliest Australopithecus, Australopithecus anamensis, had canine crowns similar in size to those of its descendant Australopithecus afarensis, but a single large root alveolus has suggested that this species may have had larger and more dimorphic canines than previously recognised. Here we present three new associated dentitions attributed to A. anamensis, recently recovered from the type site of Kanapoi, Kenya, that provide evidence of canine evolution in early Australopithecus. These fossils include the largest mandibular canine root in the hominin fossil record. We demonstrate that, although canine crown height did not differ between these species, A. anamensis had larger and more dimorphic roots, more like those of extant great apes and Ardipithecus ramidus, than those of A. afarensis. The canine and premolar occlusal shapes of A. anamensis also resemble those of Ar. ramidus, and are intermediary between extant great apes and A. afarensis. A. afarensis achieved Homo-like maxillary crown basal proportions without a reduction in crown height. Thus, canine crown size and dimorphism remained stable during the early evolution of Australopithecus, but mandibular root dimensions changed only later within the A. anamensis–afarensis lineage, coincident with morphological changes in the canine–premolar complex. These observations suggest that selection on canine tooth crown height, shape and root dimensions was not coupled in early hominin evolution, and was not part of an integrated adaptive package.

  13. ON THE UNIQUENESS OF THE UNBOUNDED CLASSICAL SOULTION OF THE EVOLUTION SYSTEM DESCRIBING GEOPHYSICAL FLOW WITHIN THE EARTH AND ITS ASSOCIATED SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    李开泰; 赵春山

    2001-01-01

    The uniqueness for unbounded classical solutions of the evolution system describing geophysical flow within the earth and its associated systems is investigated. Under suitable growth conditions,it is shown that the solution to the initial value problem is unique. Moreover,a counterexample is given if the growth conditions are not satisfied.

  14. A new time tree reveals Earth history’s imprint on the evolution of modern birds

    Science.gov (United States)

    Claramunt, Santiago; Cracraft, Joel

    2015-01-01

    Determining the timing of diversification of modern birds has been difficult. We combined DNA sequences of clock-like genes for most avian families with 130 fossil birds to generate a new time tree for Neornithes and investigated their biogeographic and diversification dynamics. We found that the most recent common ancestor of modern birds inhabited South America around 95 million years ago, but it was not until the Cretaceous-Paleogene transition (66 million years ago) that Neornithes began to diversify rapidly around the world. Birds used two main dispersion routes: reaching the Old World through North America, and reaching Australia and Zealandia through Antarctica. Net diversification rates increased during periods of global cooling, suggesting that fragmentation of tropical biomes stimulated speciation. Thus, we found pervasive evidence that avian evolution has been influenced by plate tectonics and environmental change, two basic features of Earth’s dynamics. PMID:26824065

  15. Early non-destructive biofouling detection in spiral wound RO Membranes using a mobile earth's field NMR

    KAUST Repository

    Fridjonsson, E.O.

    2015-04-20

    We demonstrate the use of Earth\\'s field (EF) Nuclear Magnetic Resonance (NMR) to provide early non-destructive detection of active biofouling of a commercial spiral wound reverse osmosis (RO) membrane module. The RO membrane module was actively biofouled to different extents, by the addition of biodegradable nutrients to the feed stream, as revealed by a subtle feed-channel pressure drop increase. Easily accessible EF NMR parameters (signal relaxation parameters T1, T2 and the total NMR signal modified to be sensitive to stagnant fluid only) were measured and analysed in terms of their ability to detect the onset of biofouling. The EF NMR showed that fouling near the membrane module entrance significantly distorted the flow field through the whole membrane module. The total NMR signal is shown to be suitable for non-destructive early biofouling detection of spiral wound membrane modules, it was readily deployed at high (operational) flow rates, was particularly sensitive to flow field changes due to biofouling and could be deployed at any position along the membrane module axis. In addition to providing early fouling detection, the mobile EF NMR apparatus could also be used to (i) evaluate the production process of spiral wound membrane modules, and (ii) provide an in-situ determination of module cleaning process efficiency.

  16. A Burst of miRNA Innovation in the Early Evolution of Butterflies and Moths

    Science.gov (United States)

    Quah, Shan; Hui, Jerome H.L.; Holland, Peter W.H.

    2015-01-01

    MicroRNAs (miRNAs) are involved in posttranscriptional regulation of gene expression. Because several miRNAs are known to affect the stability or translation of developmental regulatory genes, the origin of novel miRNAs may have contributed to the evolution of developmental processes and morphology. Lepidoptera (butterflies and moths) is a species-rich clade with a well-established phylogeny and abundant genomic resources, thereby representing an ideal system in which to study miRNA evolution. We sequenced small RNA libraries from developmental stages of two divergent lepidopterans, Cameraria ohridella (Horse chestnut Leafminer) and Pararge aegeria (Speckled Wood butterfly), discovering 90 and 81 conserved miRNAs, respectively, and many species-specific miRNA sequences. Mapping miRNAs onto the lepidopteran phylogeny reveals rapid miRNA turnover and an episode of miRNA fixation early in lepidopteran evolution, implying that miRNA acquisition accompanied the early radiation of the Lepidoptera. One lepidopteran-specific miRNA gene, miR-2768, is located within an intron of the homeobox gene invected, involved in insect segmental and wing patterning. We identified cubitus interruptus (ci) as a likely direct target of miR-2768, and validated this suppression using a luciferase assay system. We propose a model by which miR-2768 modulates expression of ci in the segmentation pathway and in patterning of lepidopteran wing primordia. PMID:25576364

  17. Minds on Earth Hour--A Theme for Sustainability in Swedish Early Childhood Education

    Science.gov (United States)

    Ärlemalm-Hagsér, Eva

    2013-01-01

    This educational science article illustrates education for sustainability in a theme about Earth Hour (energy conservation) in one Swedish preschool. This case study is based on audio recordings of dialogues between children aged five to six years and preschool teachers. It is guided by critical theory, which is also used as a conceptual tool to…

  18. End products of cometary evolution - Cometary origin of earth-crossing bodies of asteroidal appearance

    Science.gov (United States)

    Wetherill, G. W.

    1991-01-01

    The present state of the understanding of the dynamic mechanisms under which the orbits of some comets evolve into those observed for Apollo-Amor objects is reviewed. Observed Jupiter-family objects of asteroidal appearance, e.g., 1983SA, are much more likely to be of cometary rather than asteroidal origin. 'Decoupling' is facilitated by several mechanisms: perturbations by terrestrial planets, perturbations by Jupiter and the other giant planets, and nongravitational orbital changes caused by the loss of gas and dust from the comet. The dynamical time scale for decoupling is argued to be 100,000-1,000,000 yr, and almost all decoupled comets are likely to be of asteroidal appearance. Estimates can be made of the number of cometary Apollo-Amor 'asteroids', the observed number of earth-crossing active and inactive short-period comets, and the production rate of short-period comets. These estimates are compatible with other theoretical and observational inferences that suggest the presence of a significant population of Apollo objects that formerly were active comets.

  19. Constrained pattern of viral evolution in acute and early HCV infection limits viral plasticity.

    Directory of Open Access Journals (Sweden)

    Katja Pfafferott

    Full Text Available Cellular immune responses during acute Hepatitis C virus (HCV and HIV infection are a known correlate of infection outcome. Viral adaptation to these responses via mutation(s within CD8+ T-cell epitopes allows these viruses to subvert host immune control. This study examined HCV evolution in 21 HCV genotype 1-infected subjects to characterise the level of viral adaptation during acute and early HCV infection. Of the total mutations observed 25% were within described CD8+ T-cell epitopes or at viral adaptation sites. Most mutations were maintained into the chronic phase of HCV infection (75%. The lack of reversion of adaptations and high proportion of silent substitutions suggests that HCV has structural and functional limitations that constrain evolution. These results were compared to the pattern of viral evolution observed in 98 subjects during a similar phase in HIV infection from a previous study. In contrast to HCV, evolution during acute HIV infection is marked by high levels of amino acid change relative to silent substitutions, including a higher proportion of adaptations, likely reflecting strong and continued CD8+ T-cell pressure combined with greater plasticity of the virus. Understanding viral escape dynamics for these two viruses is important for effective T cell vaccine design.

  20. Early Mission Maneuver Operations for the Deep Space Climate Observatory Sun-Earth L1 Libration Point Mission

    Science.gov (United States)

    Roberts, Craig; Case, Sara; Reagoso, John; Webster, Cassandra

    2015-01-01

    The Deep Space Climate Observatory mission launched on February 11, 2015, and inserted onto a transfer trajectory toward a Lissajous orbit around the Sun-Earth L1 libration point. This paper presents an overview of the baseline transfer orbit and early mission maneuver operations leading up to the start of nominal science orbit operations. In particular, the analysis and performance of the spacecraft insertion, mid-course correction maneuvers, and the deep-space Lissajous orbit insertion maneuvers are discussed, com-paring the baseline orbit with actual mission results and highlighting mission and operations constraints..

  1. The Public Goods Hypothesis for the evolution of life on Earth.

    Science.gov (United States)

    McInerney, James O; Pisani, Davide; Bapteste, Eric; O'Connell, Mary J

    2011-08-23

    It is becoming increasingly difficult to reconcile the observed extent of horizontal gene transfers with the central metaphor of a great tree uniting all evolving entities on the planet. In this manuscript we describe the Public Goods Hypothesis and show that it is appropriate in order to describe biological evolution on the planet. According to this hypothesis, nucleotide sequences (genes, promoters, exons, etc.) are simply seen as goods, passed from organism to organism through both vertical and horizontal transfer. Public goods sequences are defined by having the properties of being largely non-excludable (no organism can be effectively prevented from accessing these sequences) and non-rival (while such a sequence is being used by one organism it is also available for use by another organism). The universal nature of genetic systems ensures that such non-excludable sequences exist and non-excludability explains why we see a myriad of genes in different combinations in sequenced genomes. There are three features of the public goods hypothesis. Firstly, segments of DNA are seen as public goods, available for all organisms to integrate into their genomes. Secondly, we expect the evolution of mechanisms for DNA sharing and of defense mechanisms against DNA intrusion in genomes. Thirdly, we expect that we do not see a global tree-like pattern. Instead, we expect local tree-like patterns to emerge from the combination of a commonage of genes and vertical inheritance of genomes by cell division. Indeed, while genes are theoretically public goods, in reality, some genes are excludable, particularly, though not only, when they have variant genetic codes or behave as coalition or club goods, available for all organisms of a coalition to integrate into their genomes, and non-rival within the club. We view the Tree of Life hypothesis as a regionalized instance of the Public Goods hypothesis, just like classical mechanics and euclidean geometry are seen as regionalized

  2. The public goods hypothesis for the evolution of life on Earth

    Directory of Open Access Journals (Sweden)

    Bapteste Eric

    2011-08-01

    Full Text Available Abstract It is becoming increasingly difficult to reconcile the observed extent of horizontal gene transfers with the central metaphor of a great tree uniting all evolving entities on the planet. In this manuscript we describe the Public Goods Hypothesis and show that it is appropriate in order to describe biological evolution on the planet. According to this hypothesis, nucleotide sequences (genes, promoters, exons, etc. are simply seen as goods, passed from organism to organism through both vertical and horizontal transfer. Public goods sequences are defined by having the properties of being largely non-excludable (no organism can be effectively prevented from accessing these sequences and non-rival (while such a sequence is being used by one organism it is also available for use by another organism. The universal nature of genetic systems ensures that such non-excludable sequences exist and non-excludability explains why we see a myriad of genes in different combinations in sequenced genomes. There are three features of the public goods hypothesis. Firstly, segments of DNA are seen as public goods, available for all organisms to integrate into their genomes. Secondly, we expect the evolution of mechanisms for DNA sharing and of defense mechanisms against DNA intrusion in genomes. Thirdly, we expect that we do not see a global tree-like pattern. Instead, we expect local tree-like patterns to emerge from the combination of a commonage of genes and vertical inheritance of genomes by cell division. Indeed, while genes are theoretically public goods, in reality, some genes are excludable, particularly, though not only, when they have variant genetic codes or behave as coalition or club goods, available for all organisms of a coalition to integrate into their genomes, and non-rival within the club. We view the Tree of Life hypothesis as a regionalized instance of the Public Goods hypothesis, just like classical mechanics and euclidean geometry are

  3. The public goods hypothesis for the evolution of life on Earth

    LENUS (Irish Health Repository)

    McInerney, James O

    2011-08-23

    Abstract It is becoming increasingly difficult to reconcile the observed extent of horizontal gene transfers with the central metaphor of a great tree uniting all evolving entities on the planet. In this manuscript we describe the Public Goods Hypothesis and show that it is appropriate in order to describe biological evolution on the planet. According to this hypothesis, nucleotide sequences (genes, promoters, exons, etc.) are simply seen as goods, passed from organism to organism through both vertical and horizontal transfer. Public goods sequences are defined by having the properties of being largely non-excludable (no organism can be effectively prevented from accessing these sequences) and non-rival (while such a sequence is being used by one organism it is also available for use by another organism). The universal nature of genetic systems ensures that such non-excludable sequences exist and non-excludability explains why we see a myriad of genes in different combinations in sequenced genomes. There are three features of the public goods hypothesis. Firstly, segments of DNA are seen as public goods, available for all organisms to integrate into their genomes. Secondly, we expect the evolution of mechanisms for DNA sharing and of defense mechanisms against DNA intrusion in genomes. Thirdly, we expect that we do not see a global tree-like pattern. Instead, we expect local tree-like patterns to emerge from the combination of a commonage of genes and vertical inheritance of genomes by cell division. Indeed, while genes are theoretically public goods, in reality, some genes are excludable, particularly, though not only, when they have variant genetic codes or behave as coalition or club goods, available for all organisms of a coalition to integrate into their genomes, and non-rival within the club. We view the Tree of Life hypothesis as a regionalized instance of the Public Goods hypothesis, just like classical mechanics and euclidean geometry are seen as

  4. The TIM Barrel Architecture Facilitated the Early Evolution of Protein-Mediated Metabolism.

    Science.gov (United States)

    Goldman, Aaron David; Beatty, Joshua T; Landweber, Laura F

    2016-01-01

    The triosephosphate isomerase (TIM) barrel protein fold is a structurally repetitive architecture that is present in approximately 10% of all enzymes. It is generally assumed that this ubiquity in modern proteomes reflects an essential historical role in early protein-mediated metabolism. Here, we provide quantitative and comparative analyses to support several hypotheses about the early importance of the TIM barrel architecture. An information theoretical analysis of protein structures supports the hypothesis that the TIM barrel architecture could arise more easily by duplication and recombination compared to other mixed α/β structures. We show that TIM barrel enzymes corresponding to the most taxonomically broad superfamilies also have the broadest range of functions, often aided by metal and nucleotide-derived cofactors that are thought to reflect an earlier stage of metabolic evolution. By comparison to other putatively ancient protein architectures, we find that the functional diversity of TIM barrel proteins cannot be explained simply by their antiquity. Instead, the breadth of TIM barrel functions can be explained, in part, by the incorporation of a broad range of cofactors, a trend that does not appear to be shared by proteins in general. These results support the hypothesis that the simple and functionally general TIM barrel architecture may have arisen early in the evolution of protein biosynthesis and provided an ideal scaffold to facilitate the metabolic transition from ribozymes, peptides, and geochemical catalysts to modern protein enzymes.

  5. Recent Structural Evolution of Early-Type Galaxies: Size Growth from z=1 to z=0

    CERN Document Server

    van der Wel, Arjen; Zirm, Andrew W; Franx, Marijn; Rettura, Alessandro; Illingworth, Garth D; Ford, Holland C

    2008-01-01

    Strong size and internal density evolution of early-type galaxies between z~2 and the present has been reported by several authors. Here we analyze samples of nearby and distant (z~1) galaxies with dynamically measured masses in order to confirm the previous, model-dependent results and constrain the uncertainties that may play a role. Velocity dispersion measurements are taken from the literature for 50 morphologically selected 0.8early-type galaxies with typical masses 2e11 Msol. Sizes are determined with ACS imaging. We compare the distant sample with a large sample of nearby (0.04early-type galaxies extracted from the SDSSfor which we determine sizes, masses, and densities in a consistent manner, using simulations to quantify systematic differences between the size measurements of nearby and distant galaxies. We find a highly significant structural difference between the nearby and distant samples, regardless of sample selection effects. The implied evolution ...

  6. Statistical signal analysis of the Phanerozoic ð13C curve: implications for Earth system evolution

    Science.gov (United States)

    Bachan, A.; Kump, L. R.; Payne, J.; Saltzman, M.; Thomas, E.

    2014-12-01

    In recent years, vast amounts of carbon isotopic data have been collected allowing the construction of the Phanerozoic δ13C curve in unprecedented detail. Our dataset comprises 8143 points spanning the last 541 m.y., with a mean spacing of 66 k.y. The average δ13C of Phanerozoic carbonate is 1 ‰ ± 2 ‰, in accordance with the canonical values measured in the past. However, the record also shows numerous, highly resolved, large (± 6 ‰) excursions whose magnitude declines through time, especially going into the late Mesozoic and Cenozoic. When the magnitude - distribution of the excursions is tabulated we find that it follows a power law: plotting the min-max differences vs. number of bins in which a particular value occurs reveals that the data fall on a semilogarithmic line with a slope of -0.23 and R2 = 0.99. The result is insensitive to outliers: smoothing the data with lowess, spline, Savitzky-Golay, and Butterworth filters yields similar results. The continuity from small variation to large perturbations, both positive and negative, suggests that, despite the numerous proposed causes for individual carbon isotopic evens, there is likely an underlying mechanism which governs the magnitude of δ13C response to perturbations. We suggest that a mechanism acting to amplify carbon cycle perturbations is the key to explaining the power-law distribution, and identify the anoxia-productivity feedback as the most likely candidate. Establishment of sulfidic conditions is accompanied by increased release of phosphate to the water column, which allows for further productivity, and thus acts as a destabilizing, positive, feedback. This feedback would act to increase carbon cycle swings irrespective of their proximal trigger. The decline in frequency of anoxic-sulfidic bottom waters in the world's oceans, and potential disappearance in the Late Mesozoic-Cenozoic, may account for a reduction in the Earth system's gain and increase in its resilience.

  7. Maximal sequence length of exact match between members from a gene family during early evolution

    Institute of Scientific and Technical Information of China (English)

    WEN Xiao; GUO Xing-yi; FAN Long-jiang

    2005-01-01

    Mutation (substitution, deletion, insertion, etc.) in nucleotide acid causes the maximal sequence lengths of exact match (MALE) between paralogous members from a duplicate event to become shorter during evolution. In this work, MALE changes between members of 26 gene families from four representative species (Arabidopsis thaliana, Oryza sativa, Mus musculus and Homo sapiens) were investigated. Comparative study ofparalogous' MALE and amino acid substitution rate (dA<0.5)indicated that a close relationship existed between them. The results suggested that MALE could be a sound evolutionary scale for the divergent time for paralogous genes during their early evolution. A reference table between MALE and divergent time for the four species was set up, which would be useful widely, for large-scale genome alignment and comparison. As an example, detection of large-scale duplication events of rice genome based on the table was illustrated.

  8. Dynamical systems for modeling the evolution of the magnetic field of stars and Earth

    Science.gov (United States)

    Popova, H.

    2016-02-01

    The cycles of solar magnetic activity are connected with a solar dynamo that operates in the convective zone. Solar dynamo mechanism is based on the combined action of the differential rotation and the alpha-effect. Application of these concepts allows us to get an oscillating solution as a wave of the toroidal field propagating from middle latitudes to the equator. We investigated the dynamo model with the meridional circulation by the low-mode approach. This approach is based on an assumption that the solar magnetic field can be described by non-linear dynamical systems with a relatively small number of parameters. Such non-linear dynamical systems are based on the equations of dynamo models. With this method dynamical systems have been built for media which contains the meridional flow and thickness of the convection zone of the star. It was shown the possibility of coexistence of quiasi-biennial and 22-year cycle. We obtained the different regimes (oscillations, vacillations, dynamo-bursts) depending on the value of the dynamo-number, the meridional circulation, and thickness of the convection zone. We discuss the features of these regimes and compare them with the observed features of evolution of the solar and geo magnetic fields. We built theoretical paleomagnetic time scale and butterfly-diagrams for the helicity and toroidal magnetic field for different regimes.

  9. The role of impact and radiogenic heating in the early thermal evolution of Mars

    Indian Academy of Sciences (India)

    S Sahijpal; G K Bhatia

    2015-02-01

    The planetary differentiation models of Mars are proposed that take into account core–mantle and coremantle–crust differentiation. The numerical simulations are presented for the early thermal evolution of Mars spanning up to the initial 25 million years (Ma) of the early solar system, probably for the first time, by taking into account the radiogenic heating due to the short-lived nuclides, 26Al and 60Fe. The influence of impact heating during the accretion of Mars is also incorporated in the simulations. The early accretion of Mars would necessitate a substantial role played by the short-lived nuclides in its heating. 26Al along with impact heating could have provided sufficient thermal energy to the entire body to substantially melt and trigger planetary scale differentiation. This is contrary to the thermal models based exclusively on the impact heating that could not produce widespread melting and planetary differentiation. The early onset of the accretion of Mars perhaps within the initial ∼1.5 Ma in the early solar system could have resulted in substantial differentiation of Mars, provided, it accreted over the timescale of ∼1 Ma. This seems to be consistent with the chronological records of the Martian meteorites.

  10. Shape Evolution of Massive Early-Type Galaxies: Confirmation of Increased Disk Prevalence at z>1

    CERN Document Server

    Chang, Yu-Yen; Rix, Hans-Walter; Wuyts, Stijn; Zibetti, Stefano; Ramkumar, Balasubramanian; Holden, Bradford P

    2012-01-01

    We use high-resolution K-band VLT/HAWK-I imaging over 0.25 square degrees to study the structural evolution of massive early-type galaxies since z~1. Mass-selected samples, complete down to log(M/M_sun)~10.7 such that `typical' L* galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separated the samples into different redshift slices and classify them as late- or early-type galaxies on the basis of their specific star-formation rate. Axis-ratio measurements for the ~400 early-type galaxies in the redshift range 0.61 are, on average, flatter than at z11.3) are the roundest, with a pronounced lack among them of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs merging is required for early-type galaxies to grow beyond log(M/M_sun)~11.3, and all early types over time gradually and partially loose their disk-like characteristics.

  11. Lunge feeding in early marine reptiles and fast evolution of marine tetrapod feeding guilds.

    Science.gov (United States)

    Motani, Ryosuke; Chen, Xiao-hong; Jiang, Da-yong; Cheng, Long; Tintori, Andrea; Rieppel, Olivier

    2015-01-01

    Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual, and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds, and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic.

  12. Microstructural evolution of 7012 alloy during the early stages of artificial ageing

    Energy Technology Data Exchange (ETDEWEB)

    Ferragut, R.; Somoza, A.; Tolley, A.

    1999-11-26

    A study of the microstructural evolution of a commercial 7012 (Al-Zn-Mg-Cu) age-hardenable alloy following artificial ageing by high resolution and conventional transmission electron microscopy and positron annihilation lifetime spectroscopy is presented. At the early stages of decomposition, the microstructure included precipitation of either pre-precipitate solute clusters or Guinier-Preston zones and semi-coherent {eta}{prime} precipitates, with typical sizes between 1 and 10 nm. Quantitative information on the size, number density and morphology of the particles present in the microstructure was obtained. The results were correlated with those obtained using positron annihilation lifetime spectroscopy.

  13. A Model of Isotope Separation in Cells at the Early Stages of Evolution.

    Science.gov (United States)

    Melkikh, A V; Bokunyaeva, A O

    2016-03-01

    The separation of the isotopes of certain ions can serve as an important criterion for the presence of life in the early stages of its evolution. A model of the separation of isotopes during their transport through the cell membrane is constructed. The dependence of the selection coefficient on various parameters is found. In particular, it is shown that the maximum efficiency of the transport of ions corresponds to the minimum enrichment coefficient. At the maximum enrichment, the efficiency of the transport system approaches ½. Calculated enrichment coefficients are compared with experimentally obtained values for different types of cells, and the comparison shows a qualitative agreement between these quantities.

  14. Young Sun, Early Earth and the Origins of Life Lessons for Astrobiology

    CERN Document Server

    Gargaud, Muriel; López-García, Purificación; Montmerle, Thierry; Pascal, Robert

    2012-01-01

    - How did the Sun come into existence? - How was the Earth formed? - How long has Earth been the way it is now, with its combination of oceans and continents? - How do you define “life”? - How did the first life forms emerge? - What conditions made it possible for living things to evolve? All these questions are answered in this colourful textbook addressing undergraduate students in "Origins of Life" courses and the scientifically interested public. The authors take the reader on an amazing voyage through time, beginning five thousand million years ago in a cloud of interstellar dust and ending five hundred million years ago, when the living world that we see today was finally formed. A chapter on exoplanets provides an overview of the search for planets outside the solar system, especially for habitable ones. The appendix closes the book with a glossary, a bibliography of further readings and a summary of the Origins of the Earth and life in fourteen boxes.

  15. Evolution of the Proterozoic Earth System: Insights from the ∆17O Record of Sedimentary Sulfate Minerals

    Science.gov (United States)

    Crockford, P. W.; Hayles, J. A.; Halverson, G. P.; Bekker, A.; Rainbird, R.; Wing, B. A.

    2014-12-01

    Triple oxygen isotope ratios (18O/16O and 17O/16O) are a powerful tool to tease out interconnections within the Surface Earth System, both today and throughout Earth's history. This ability comes from the fact that stratospheric photochemistry imparts a negative ∆17O anomaly (∆17O = δ17O - 0.52×δ18O) to atmospheric oxygen whose magnitude is proportional to pCO2 levels and photosynthetic oxygen production. Atmospheric oxygen readily weathers continental sulfides and, as a result, the secular variations in atmospheric ∆17O values may be recorded in marine sulfate minerals (barite, gypsum and anhydrite). The largest ∆17O anomalies found in the rock record are from peculiar barite layers that immediately post-date the 635 Ma Marinoan Snowball Event. While these anomalies have been interpreted to result from a weak post-glacial photosynthetic O2 flux, the balance of other evidence (e.g., Zn isotope records of near-modern post-glacial productivity) suggests that they instead reflect the elevated CO2 levels thought to be required to exit a snowball state. As this situation illustrates, the ∆17O record by itself does not provide a unique solution between production of the anomaly by stratospheric reactions and its destruction by global biospheric productivity. In the context of additional geological and geochemical constraints, however, a marine sulfate ∆17O record has the potential to provide new insights into paleoatmospheres, paleoclimates, and paleoproductivity. We have produced new data (n ≈ 200) for Proterozoic evaporites that extend the sulfate ∆17O record from the Neoproterozoic to ~2.3 Ga. This data will be interpreted within our current understanding of Proterozoic Earth System Evolution on basinal to global scales and will address key questions that include: Were Paleoproterozoic glacial episodes terminated by elevated pCO2? Was the Great Oxidation Event accompanied by enhanced productivity? Does the lack of C isotope variability throughout

  16. Insights into the early evolution of animal calcium signaling machinery: a unicellular point of view.

    Science.gov (United States)

    Cai, Xinjiang; Wang, Xiangbing; Patel, Sandip; Clapham, David E

    2015-03-01

    The basic principles of Ca(2+) regulation emerged early in prokaryotes. Ca(2+) signaling acquired more extensive and varied functions when life evolved into multicellular eukaryotes with intracellular organelles. Animals, fungi and plants display differences in the mechanisms that control cytosolic Ca(2+) concentrations. The aim of this review is to examine recent findings from comparative genomics of Ca(2+) signaling molecules in close unicellular relatives of animals and in common unicellular ancestors of animals and fungi. Also discussed are the evolution and origins of the sperm-specific CatSper channel complex, cation/Ca(2+) exchangers and four-domain voltage-gated Ca(2+) channels. Newly identified evolutionary evidence suggests that the distinct Ca(2+) signaling machineries in animals, plants and fungi likely originated from an ancient Ca(2+) signaling machinery prior to early eukaryotic radiation.

  17. The formation and early evolution of stars from dust to stars and planets

    CERN Document Server

    Schulz, Norbert S

    2012-01-01

    Starburst regions in nearby and distant galaxies have a profound impact on our understanding of the early universe. This new, substantially updated and extended edition of Norbert Schulz’s unique book "From Dust to Stars" describes complex physical processes involved in the creation and early evolution of stars. It illustrates how these processes reveal themselves from radio wavelengths to high energy X-rays and gamma–rays, with special reference towards high energy signatures. Several sections devoted to key analysis techniques demonstrate how modern research in this field is pursued and new chapters are introduced on massive star formation, proto-planetary disks and observations of young exoplanets. Recent advances and contemporary research on the theory of star formation are explained, as are new observations, specifically from the three great observatories of the Spitzer Space Telescope, the Hubble Space Telescope and the Chandra X-Ray Observatory which all now operate at the same time and make high r...

  18. Phylogenetic ctDNA analysis depicts early stage lung cancer evolution

    DEFF Research Database (Denmark)

    Abbosh, Christopher; Birkbak, Nicolai Juul; Wilson, Gareth A.

    2017-01-01

    of early-stage lung cancer is not established. Here we conduct a tumour-specific phylogenetic approach to ctDNA profiling in the first 100 TRACERx (TRAcking non-small cell lung Cancer Evolution through therapy (Rx)) study participants, including one patient co-recruited to the PEACE (Posthumous Evaluation......The early detection of relapse following primary surgery for non-small cell lung cancer and the characterization of emerging subclones seeding metastatic sites might offer new therapeutic approaches to limit tumor recurrence. The potential to non-invasively track tumor evolutionary dynamics in ctDNA...... of Advanced Cancer Environment) post-mortem study. We identify independent predictors of ctDNA release and perform tumor volume limit of detection analyses. Through blinded profiling of post-operative plasma, we observe evidence of adjuvant chemotherapy resistance and identify patients destined to experience...

  19. Evaluating the primary and/or diagenetic origin of rare earth element abundances in Ediacaran to early Cambrian phosphate deposits, Yangtze Platform (South China) by LA-ICPMS

    Science.gov (United States)

    Hippler, Dorothee; Klügel, Andreas; Biedermann, Nicole; Guo, Qingjun; Franz, Gerhard

    2014-05-01

    The Precambrian-Cambrian time interval represents one of the greatest phosphogenic episodes in Earth's history with giant and well-preserved phosphate deposits occurring on the Yangtze Platform in South China. We investigated concentrations of rare earth elements (REE) and yttrium of shallow and deep-water sedimentary phosphate deposits of the Ediacaran Doushantou Formation and the early Cambrian Zhongyicun Formation by using LA-ICP mass spectrometry. The aim is to examine the temporal and spatial variability of seawater chemistry in conjunction with the conditions of phosphate formation and the evaluation of the extent of diagenetic modification. The mineralogical and textural composition of the samples was pre-screened using SEM and XRD, and polished thick sections were prepared for subsequent high-resolution LA-ICPMS analyses. Overall concentrations in REE range between 18 and 657 ppm, with elevated concentrations (> 200 ppm) in apatite from the deep-water phosphate deposits. REE+Y patterns of shallow-water phosphate deposits exhibit the evolution from flat shale-like to gently inclined seawater-derived patterns, with the early Cambrian phosphate deposits revealing distinct negative Ce- and positive Y-anomalies indicative for oxygenated surface waters. REE+Y patterns of phosphate deposits of the deep-water facies are flat to highly enriched in MREE, which is manifested in variably pronounced concave-down patterns. In detail, these patterns display different Ce-anomalies, as well as small positive Eu-anomalies. We propose that REE+Y patterns of Ediacaran and early Cambrian sedimentary phosphate deposits can inherit both primary and secondary signatures reflecting either seawater composition or diagenetic modification and fluid flow. The combination of imaging techniques and in-situ LA-ICPMS thereby enables a more sophisticated examination of the potential sources and processes than whole rock determinations. Placing the results in stratigraphic order and assuming

  20. Mechanisms of inclusion evolution and intra-granular acicular ferrite formation in steels containing rare earth elements

    Institute of Scientific and Technical Information of China (English)

    Xiaoxuan DENG; Min JIANG; Xinhua WANG

    2012-01-01

    Inclusion characteristic and microstructure of rare earth (RE) elements containing steel were evaluated with scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS),element-mapping,optical microscopy (OM),and automated feature analysis (AFA) option equipped with ASPEX PSEM.Factsage was used tocalculate the equilibrium inclusion composition.Based on the calculation,an inclusion evolution mechanism was proposed.Furthermore,line scanning analysis was used to elucidate the intra-granular acicular ferrite (IAF) nucleation mechanism.The result showed that two different inclusions exist in sample steel:(Mn-Al-Si-Ti-La-Ce-O)+MnS complex inclusion and isolated MnS inclusion.Almost all nucleation sites for IAF are complex inclusions,while single MnS inclusion cannot induce IAF.A possible formation mechanism of complex inclusion is proposed based on calculated results using Factsage,which agrees well with experimental results.A Mn-depletion zone (MDZ) which exists adjacent to the (Mn-A1-Si-Ti-La-Ce-O) +-MnS complex inclusion can account for the IAF formation.However,the low volume fraction (1.49× 10-7)of effective inclusion may result in onlv 10% (volume fraction) IAF.

  1. Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

    Science.gov (United States)

    Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

    2007-09-04

    The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

  2. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica.

    Science.gov (United States)

    Barreda, Viviana D; Palazzesi, Luis; Tellería, Maria C; Olivero, Eduardo B; Raine, J Ian; Forest, Félix

    2015-09-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general.

  3. The role of impact and radiogenic heating in the early thermal evolution of Mars

    CERN Document Server

    Sahijpal, S

    2014-01-01

    The planetary differentiation models of Mars are proposed that take into account core-mantle and core-mantle-crust differentiation. The numerical simulations are presented for the early thermal evolution of Mars spanning up to the initial 25 million years (Ma) of the early solar system, probably for the first time, by taking into account the radiogenic heating due to the short-lived nuclides, 26Al and 60Fe. The influence of impact heating during the accretion of Mars is also incorporated in the simulations. The early accretion of Mars would necessitate a substantial role played by the short-lived nuclides in its heating. 26Al along with impact heating could have provided sufficient thermal energy to the entire body to substantially melt and trigger planetary scale differentiation. This is contrary to the thermal models based exclusively on the impact heating that could not produce widespread melting and planetary differentiation. The early onset of the accretion of Mars perhaps within the initial ~1.5 Ma in t...

  4. The earth radiation budget satellite system of the early 1980's

    Science.gov (United States)

    Cooper, J. E.; Woerner, C. V.

    1978-01-01

    The overall program objective of the Earth Radiation Budget Satellite System is to gather the required radiation budget data and apply these data for a better understanding and prediction of climate. The paper describes the planned system, including the instruments and the associated sampling strategies and data analysis methods. Examination of mission implications reveals the need for a multisensor, multisatellite system consisting of high- and mid-inclination orbits. Each spacecraft will carry wide and medium field-of-view sensors, a sensor for measuring the solar constant, and a narrow field-of-view cross-track scanner.

  5. Molecular Evolution of Aminoacyl tRNA Synthetase Proteins in the Early History of Life

    Science.gov (United States)

    Fournier, Gregory P.; Andam, Cheryl P.; Alm, Eric J.; Gogarten, J. Peter

    2011-12-01

    Aminoacyl-tRNA synthetases (aaRS) consist of several families of functionally conserved proteins essential for translation and protein synthesis. Like nearly all components of the translation machinery, most aaRS families are universally distributed across cellular life, being inherited from the time of the Last Universal Common Ancestor (LUCA). However, unlike the rest of the translation machinery, aaRS have undergone numerous ancient horizontal gene transfers, with several independent events detected between domains, and some possibly involving lineages diverging before the time of LUCA. These transfers reveal the complexity of molecular evolution at this early time, and the chimeric nature of genomes within cells that gave rise to the major domains. Additionally, given the role of these protein families in defining the amino acids used for protein synthesis, sequence reconstruction of their pre-LUCA ancestors can reveal the evolutionary processes at work in the origin of the genetic code. In particular, sequence reconstructions of the paralog ancestors of isoleucyl- and valyl- RS provide strong empirical evidence that at least for this divergence, the genetic code did not co-evolve with the aaRSs; rather, both amino acids were already part of the genetic code before their cognate aaRSs diverged from their common ancestor. The implications of this observation for the early evolution of RNA-directed protein biosynthesis are discussed.

  6. The evolution of early cellular systems viewed through the lens of biological interactions.

    Science.gov (United States)

    Poole, Anthony M; Lundin, Daniel; Rytkönen, Kalle T

    2015-01-01

    The minimal cell concept represents a pragmatic approach to the question of how few genes are required to run a cell. This is a helpful way to build a parts-list, and has been more successful than attempts to deduce a minimal gene set for life by inferring the gene repertoire of the last universal common ancestor, as few genes trace back to this hypothetical ancestral state. However, the study of minimal cellular systems is the study of biological outliers where, by practical necessity, coevolutionary interactions are minimized or ignored. In this paper, we consider the biological context from which minimal genomes have been removed. For instance, some of the most reduced genomes are from endosymbionts and are the result of coevolutionary interactions with a host; few such organisms are "free-living." As few, if any, biological systems exist in complete isolation, we expect that, as with modern life, early biological systems were part of an ecosystem, replete with organismal interactions. We favor refocusing discussions of the evolution of cellular systems on processes rather than gene counts. We therefore draw a distinction between a pragmatic minimal cell (an interesting engineering problem), a distributed genome (a system resulting from an evolutionary transition involving more than one cell) and the looser coevolutionary interactions that are ubiquitous in ecosystems. Finally, we consider the distributed genome and coevolutionary interactions between genomic entities in the context of early evolution.

  7. A horizontal gene transfer supported the evolution of an early metazoan biomineralization strategy

    Directory of Open Access Journals (Sweden)

    Wörheide Gert

    2011-08-01

    Full Text Available Abstract Background The synchronous and widespread adoption of the ability to biomineralize was a defining event for metazoan evolution during the late Precambrian/early Cambrian 545 million years ago. However our understanding on the molecular level of how animals first evolved this capacity is poor. Because sponges are the earliest branching phylum of biomineralizing metazoans, we have been studying how biocalcification occurs in the coralline demosponge Astrosclera willeyana. Results We have isolated and characterized a novel protein directly from the calcified spherulites of A. willeyana. Using three independent lines of evidence (genomic architecture of the gene in A. willeyana, spatial expression of the gene product in A. willeyana and genomic architecture of the gene in the related demosponge Amphimedon queenslandica, we show that the gene that encodes this protein was horizontally acquired from a bacterium, and is now highly and exclusively expressed in spherulite forming cells. Conclusions Our findings highlight the ancient and close association that exists between sponges and bacteria, and provide support for the notion that horizontal gene transfer may have been an important mechanism that supported the evolution of this early metazoan biomineralisation strategy.

  8. Sm/Lsm genes provide a glimpse into the early evolution of the spliceosome.

    Directory of Open Access Journals (Sweden)

    Stella Veretnik

    2009-03-01

    Full Text Available The spliceosome, a sophisticated molecular machine involved in the removal of intervening sequences from the coding sections of eukaryotic genes, appeared and subsequently evolved rapidly during the early stages of eukaryotic evolution. The last eukaryotic common ancestor (LECA had both complex spliceosomal machinery and some spliceosomal introns, yet little is known about the early stages of evolution of the spliceosomal apparatus. The Sm/Lsm family of proteins has been suggested as one of the earliest components of the emerging spliceosome and hence provides a first in-depth glimpse into the evolving spliceosomal apparatus. An analysis of 335 Sm and Sm-like genes from 80 species across all three kingdoms of life reveals two significant observations. First, the eukaryotic Sm/Lsm family underwent two rapid waves of duplication with subsequent divergence resulting in 14 distinct genes. Each wave resulted in a more sophisticated spliceosome, reflecting a possible jump in the complexity of the evolving eukaryotic cell. Second, an unusually high degree of conservation in intron positions is observed within individual orthologous Sm/Lsm genes and between some of the Sm/Lsm paralogs. This suggests that functional spliceosomal introns existed before the emergence of the complete Sm/Lsm family of proteins; hence, spliceosomal machinery with considerably fewer components than today's spliceosome was already functional.

  9. Revalidation of the genus Chiloguembelitria Hofker: Implications for the evolution of early Danian planktonic foraminifera

    Science.gov (United States)

    Arenillas, Ignacio; Arz, José A.; Gilabert, Vicente

    2017-10-01

    Guembelitria is the only planktonic foraminiferal genus whose survival from the mass extinction event of the Cretaceous/Paleogene (K/Pg) boundary has been clearly proven. The evolution of Guembelitria after the K/Pg boundary led to the appearance of two guembelitriid lineages in the early Danian: one biserial, represented by Woodringina and culminating in Chiloguembelina, and the other trochospiral, represented by Trochoguembelitria and culminating in Globoconusa. We have re-examined the genus Chiloguembelitria, another guembelitriid descended from Guembelitria and whose taxonomic validity had been questioned, it being considered a junior synonym of the latter. Nevertheless, Chiloguembelitria differs from Guembelitria mainly in the wall texture (pustulate to rugose vs. pore-mounded) and the position of the aperture (umbilical-extraumbilical to extraumbilical vs. umbilical). Chiloguembelitria shares its wall texture with Trochoguembelitria and some of the earliest specimens of Woodringina, suggesting that it played an important role in the evolution of early Danian guembelitriids, as it seems to be the most immediate ancestor of both trochospiral and biserial lineages. Morphological and morphostatistical analyses of Chiloguembelitria discriminate at least five species: Chg. danica, Chg. irregularis, and three new species: Chg. hofkeri, Chg. trilobata and Chg. biseriata.

  10. Early evolution of electron cyclotron driven current during suppression of tearing modes in a circular tokamak

    CERN Document Server

    Pratt, J; Westerhof, E

    2016-01-01

    When electron cyclotron (EC) driven current is first applied to the inside of a magnetic island, the current spreads throughout the island and after a short period achieves a steady level. Using a two equation fluid model for the EC current that allows us to examine this early evolution in detail, we analyze high-resolution simulations of a 2/1 classical tearing mode in a low-beta large aspect-ratio circular tokamak. These simulations use a nonlinear 3D reduced-MHD fluid model and the JOREK code. During the initial period where the EC driven current grows and spreads throughout the magnetic island, it is not a function of the magnetic flux. However, once it has reached a steady-state, it should be a flux function. We demonstrate numerically that if sufficiently resolved toroidally, the steady-state EC driven current becomes approximately a flux function. We discuss the physics of this early period of EC evolution and its impact on the size of the magnetic island.

  11. Early Evolution of Vertebrate Mybs: An Integrative Perspective Combining Synteny, Phylogenetic, and Gene Expression Analyses.

    Science.gov (United States)

    Campanini, Emeline B; Vandewege, Michael W; Pillai, Nisha E; Tay, Boon-Hui; Jones, Justin L; Venkatesh, Byrappa; Hoffmann, Federico G

    2015-10-15

    The genes in the Myb superfamily encode for three related transcription factors in most vertebrates, A-, B-, and c-Myb, with functionally distinct roles, whereas most invertebrates have a single Myb. B-Myb plays an essential role in cell division and cell cycle progression, c-Myb is involved in hematopoiesis, and A-Myb is involved in spermatogenesis and regulating expression of pachytene PIWI interacting RNAs, a class of small RNAs involved in posttranscriptional gene regulation and the maintenance of reproductive tissues. Comparisons between teleost fish and tetrapods suggest that the emergence and functional divergence of the Myb genes were linked to the two rounds of whole-genome duplication early in vertebrate evolution. We combined phylogenetic, synteny, structural, and gene expression analyses of the Myb paralogs from elephant shark and lampreys with data from 12 bony vertebrates to reconstruct the early evolution of vertebrate Mybs. Phylogenetic and synteny analyses suggest that the elephant shark and Japanese lamprey have copies of the A-, B-, and c-Myb genes, implying their origin could be traced back to the common ancestor of lampreys and gnathostomes. However, structural and gene expression analyses suggest that their functional roles diverged between gnathostomes and cyclostomes. In particular, we did not detect A-Myb expression in testis suggesting that the involvement of A-Myb in the pachytene PIWI interacting RNA pathway is probably a gnathostome-specific innovation. We speculate that the secondary loss of a central domain in lamprey A-Myb underlies the functional differences between the cyclostome and gnathostome A-Myb proteins. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  12. Bayesian Morphological Clock Methods Resurrect Placoderm Monophyly and Reveal Rapid Early Evolution in Jawed Vertebrates.

    Science.gov (United States)

    King, Benedict; Qiao, Tuo; Lee, Michael S Y; Zhu, Min; Long, John A

    2017-07-01

    The phylogeny of early gnathostomes provides an important framework for understanding one of the most significant evolutionary events, the origin and diversification of jawed vertebrates. A series of recent cladistic analyses have suggested that the placoderms, an extinct group of armoured fish, form a paraphyletic group basal to all other jawed vertebrates. We revised and expanded this morphological data set, most notably by sampling autapomorphies in a similar way to parsimony-informative traits, thus ensuring this data (unlike most existing morphological data sets) satisfied an important assumption of Bayesian tip-dated morphological clock approaches. We also found problems with characters supporting placoderm paraphyly, including character correlation and incorrect codings. Analysis of this data set reveals that paraphyly and monophyly of core placoderms (excluding maxillate forms) are essentially equally parsimonious. The two alternative topologies have different root positions for the jawed vertebrates but are otherwise similar. However, analysis using tip-dated clock methods reveals strong support for placoderm monophyly, due to this analysis favoring trees with more balanced rates of evolution. Furthermore, enforcing placoderm paraphyly results in higher levels and unusual patterns of rate heterogeneity among branches, similar to that generated from simulated trees reconstructed with incorrect root positions. These simulations also show that Bayesian tip-dated clock methods outperform parsimony when the outgroup is largely uninformative (e.g., due to inapplicable characters), as might be the case here. The analysis also reveals that gnathostomes underwent a rapid burst of evolution during the Silurian period which declined during the Early Devonian. This rapid evolution during a period with few articulated fossils might partly explain the difficulty in ascertaining the root position of jawed vertebrates. © The Author(s) 2016. Published by Oxford University

  13. Hafnium and iron isotopes in early Archean komatiites record a plume-driven convection cycle in the Hadean Earth

    Science.gov (United States)

    Nebel, Oliver; Campbell, Ian H.; Sossi, Paolo A.; Van Kranendonk, Martin J.

    2014-07-01

    Archean (>2.5 billion years) komatiites are considered expressions of mantle plumes that originate from and thereby sample the lowermost mantle overlying the Earth's core. Some komatiites have reported Hf isotope signatures that require a mantle source with a time-integrated Lu/Hf that is appreciably higher than average modern depleted mantle. The systematic study of the time and locus of parent-daughter fractionation of the mantle sources of these komatiites potentially constrains differentiation processes in the early Earth, and subsequent distribution and storage of early mantle reservoirs. We present radiogenic Hf and stable Fe isotopes for a series of komatiites from the Pilbara craton in Western Australia (aged 3.5 to 2.9 Ga). After careful evaluation of the effects of alteration, we find that pristine samples are characterised by a light Fe isotope mantle source and initial 176Hf/177Hf well above the age-corrected depleted mantle. Taken together these observations require a component of an old, melt-depleted reservoir in their mantle source. The Hf isotope signature of this component appears to be complementary to the first terrestrial crust, as preserved in Hadean (i.e., >4 Ga) detrital zircon cores, suggesting a causal relationship and a Hadean age for this depletion event. We propose that this Early Refractory Reservoir (ERR) is the residue formed by deep melting in hot Hadean mantle plumes, which then accumulated at the base of the first crust. Parts of this primordial lithosphere were destabilised and sank to the core-mantle boundary in cold drips and subsequently returned in hot mantle plumes, whose thermal capacity allows melting of such refractory mantle with its archetype isotope signature. The cycling of this material via cold drips and hot plumes suggests a plume-dominated convection prior to ∼3.9 Ga, which is then replaced by Archean-style plate tectonics.

  14. Earth's early fossil record: Why not look for similar fossils on Mars?

    Science.gov (United States)

    Awramik, Stanley M.

    1989-01-01

    The oldest evidence of life on Earth is discussed with attention being given to the structure and formation of stromatolites and microfossils. Fossilization of microbes in calcium carbonate or chert media is discussed. In searching for fossil remains on Mars, some lessons learned from the study of Earth's earliest fossil record can be applied. Certain sedimentary rock types and sedimentary rock configurations should be targeted for investigation and returned by the Martian rover and ultimately by human explorers. Domical, columnar to wavy laminated stratiform sedimentary rocks that resemble stromatolites should be actively sought. Limestone, other carbonates, and chert are the favored lithology. Being macroscopic, stromatolites might be recognized by an intelligent unmanned rover. In addition, black, waxy chert with conchoidal fracture should be sought. Chert is by far the preferred lithology for the preservation of microbes and chemical fossils. Even under optimal geological conditions (little or no metamorphism or tectonic alteration, excellent outcrops, and good black chert) and using experienced field biogeologists, the chances of finding well preserved microbial remains in chert are very low.

  15. Iron oxides, divalent cations, silica, and the early earth phosphorus crisis

    DEFF Research Database (Denmark)

    Jones, C.; Nomosatryo, S.; Crowe, S.A.;

    2015-01-01

    and silica content of BIFs, we estimate that seawater in the Archean and early Proterozoic Eons likely contained 0.04–0.13 µM phosphorus, on average. These phosphorus limiting conditions could have favored primary production through photoferrotrophy at the expense of oxygenic photosynthesis until upwelling......As a nutrient required for growth, phosphorus regulates the activity of life in the oceans. Iron oxides sorb phosphorus from seawater, and through the Archean and early Proterozoic Eons, massive quantities of iron oxides precipitated from the oceans, producing a record of seawater chemistry...

  16. Early Mantle Evolution and the Late Veneer - New Perspectives from Highly Siderophile Elements

    Science.gov (United States)

    Coggon, J. A.; Luguet, A.; Lorand, J. P.; Fonseca, R.; Appel, P.; Mondal, S. K.; Peters, S.; Nowell, G. M.; Hoffmann, J. E.

    2015-12-01

    Numerous studies show that core - mantle differentiation should have fractionated the highly siderophile elements (HSE) into Earth's core during its formation, leaving them almost entirely depleted in the mantle. It is widely held that later addition of chondritic material (a.k.a. the "late veneer") can account for the disparity between modelled and observed HSE concentrations in the upper mantle. Recent experimental data (Médard et al., 2015) indicate that addition of ~0.6 % of the mass of the Earth could re-enrich the mantle HSE budget sufficiently to satisfy these observations. However, debate remains strong regarding the absolute timing, duration and nature of the re-enrichment. Chondrite-normalised HSE patterns (Coggon et al., 2015) of massive chromitites from the >3.811 Ga Ujaragssuit nunât layered ultramafic body, Greenland, are strikingly similar in both shape and abundance to the patterns of Phanerozoic chromitites from ultramafic layered intrusions. These data suggest that late veneer re-enrichment had already occurred prior to 3.811 Ga (Bennett et al., 2002; Coggon et al., 2013). Furthermore, Pt-Os model ages for these samples indicate that a late veneer component may have been present in Earth's mantle as early as 4.1 - 4.3 Ga (Coggon et al., 2013). HSE inter-element ratios demonstrate distinct differences between this chromitite sample suite and younger chromitites from analogous tectonic settings. It remains unclear whether late veneer addition was already complete at 3.82 Ga and how long it took for this material to be accreted and homogenised within the upper mantle. We will address these issues using HSE and Os isotope data from Ujaragssuit nunât, Greenland, and the Singhbum Craton, India.

  17. Cuatro Ciénegas Basin an analog of precambrian Earth and possible early mars scenario. (Invited)

    Science.gov (United States)

    Souza, V.; Eguiarte, L. E.; Sierfert, J.

    2010-12-01

    In the present, the Cuatro Cienegas Basin (CCB) is in the Chihuahuan Desert in the state of Coahuila, Mexico. However, in the early Triasic, the sea penetrated the region of CCB with the opening of Pangea and became a continental wetland with the closing the western interior seaway only 35 million years ago. Its particular tectonics made of CCB a valley surrounded by high sierras that rose above the sea level 700 mt. All available molecular data lead us to suggest that these ancient marine microbial mats have persisted for a very long time and during all that time, the living microbial community evolved and diversified locally due to the rarity of migration and sex. The struggle for life in these structured communities generated uncountable new species that had to deal with the environment, the neighbors and most of all with the extreme lack of P. What for a long time represented the most successful community assemblage in the history of planet Earth, became mostly extinct in modern earth. The herbivores and the competition with algae left few relict communities in extreme environments such as CCB, Shark Bay and Guerrero Negro. Lets remember that stromatolite reefs have fossils as old as 3.6 billion years and that they became so successful that they changed the planet atmosphere producing the great oxygenation event. We also have data that at CCB these extensive microbialites are very patchy and differentiated both taxonomically and genetically, implying that, even though they may look as a continuum in the wetlands, each patch has been geographically isolated for a long time allowing each community to diverge in its composition. All these particularities of CCB arise because, due to its unusual geology, the valley floor was never buried, hence its marine sediment, with extensive microbial mats, always had sun and water, maintaining both the ancient lineages and the oligotrophic conditions that characterized early earth. The lack of P (less than 0.05 n

  18. New insights on early evolution of spiny-rayed fishes (Teleostei: Acanthomorpha

    Directory of Open Access Journals (Sweden)

    Wei-Jen eChen

    2014-10-01

    Full Text Available The Acanthomorpha is the largest group of teleost fishes with about one third of extant vertebrate species. In the course of its evolution this lineage experienced several episodes of radiation, leading to a large number of descendant lineages differing profoundly in morphology, ecology, distribution and behavior. Although Acanthomorpha was recognized decades ago, we are only now beginning to decipher its large-scale, time-calibrated phylogeny, a prerequisite to test various evolutionary hypotheses explaining the tremendous diversity of this group. In this study, we provide new insights into the early evolution of the acanthomorphs and the euteleost allies based on the phylogenetic analysis of a newly developed dataset combining nine nuclear and mitochondrial gene markers. Our inferred tree is time-calibrated using 15 fossils, some of which have not been used before. While our phylogeny strongly supports a monophyletic Neoteleostei, Ctenosquamata (i.e., Acanthomorpha plus Myctophiformes, and Acanthopterygii, we find weak support (bootstrap value < 48% for the traditionally defined Acanthomorpha, as well as evidence of non-monophyly for the traditional Paracanthopterygii, Beryciformes, and Percomorpha. We corroborate the new Paracanthopterygii sensu Miya et al. (2005 including Polymixiiformes, Zeiformes, Gadiformes, Percopsiformes, and likely the enigmatic Stylephorus chordatus. Our timetree largely agrees with other recent studies based on nuclear loci in inferring an Early Cretaceous origin for the acanthomorphs followed by a Late Cretaceous/Early Paleogene radiation of major lineages. This is in contrast to mitogenomic studies mostly inferring Jurassic or even Triassic ages for the origin of the acanthomorphs. We compare our results to those of previous studies, and attempt to address some of the issues that may have led to incongruence between the fossil record and the molecular clock studies, as well as between the different molecular

  19. Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation.

    Science.gov (United States)

    Simmons, Nancy B; Seymour, Kevin L; Habersetzer, Jörg; Gunnell, Gregg F

    2008-02-14

    Bats (Chiroptera) represent one of the largest and most diverse radiations of mammals, accounting for one-fifth of extant species. Although recent studies unambiguously support bat monophyly and consensus is rapidly emerging about evolutionary relationships among extant lineages, the fossil record of bats extends over 50 million years, and early evolution of the group remains poorly understood. Here we describe a new bat from the Early Eocene Green River Formation of Wyoming, USA, with features that are more primitive than seen in any previously known bat. The evolutionary pathways that led to flapping flight and echolocation in bats have been in dispute, and until now fossils have been of limited use in documenting transitions involved in this marked change in lifestyle. Phylogenetically informed comparisons of the new taxon with other bats and non-flying mammals reveal that critical morphological and functional changes evolved incrementally. Forelimb anatomy indicates that the new bat was capable of powered flight like other Eocene bats, but ear morphology suggests that it lacked their echolocation abilities, supporting a 'flight first' hypothesis for chiropteran evolution</