Jupiter and planet Earth

International Nuclear Information System (INIS)

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

Origin of the Earth and planets

International Nuclear Information System (INIS)

Safronov, V.S.; Ruskol, E.L.

1982-01-01

The present state of the Schmidt hypothesis on planets formation by combining cold solid particles and bodies in the protoplanet dust cloud is briefly outlined in a popular form. The most debatable problems of the planet cosmogony: formation of and processes in a protoplanet cloud, results of analytical evaluations and numerical simulation of origin of the Earth and planets-giants are discussed [ru

An Earth-mass planet orbiting α Centauri B.

Science.gov (United States)

Dumusque, Xavier; Pepe, Francesco; Lovis, Christophe; Ségransan, Damien; Sahlmann, Johannes; Benz, Willy; Bouchy, François; Mayor, Michel; Queloz, Didier; Santos, Nuno; Udry, Stéphane

2012-11-08

Exoplanets down to the size of Earth have been found, but not in the habitable zone--that is, at a distance from the parent star at which water, if present, would be liquid. There are planets in the habitable zone of stars cooler than our Sun, but for reasons such as tidal locking and strong stellar activity, they are unlikely to harbour water-carbon life as we know it. The detection of a habitable Earth-mass planet orbiting a star similar to our Sun is extremely difficult, because such a signal is overwhelmed by stellar perturbations. Here we report the detection of an Earth-mass planet orbiting our neighbour star α Centauri B, a member of the closest stellar system to the Sun. The planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star (one astronomical unit is the Earth-Sun distance).

Terrestrial planet formation in the presence of migrating super-Earths

International Nuclear Information System (INIS)

Izidoro, André; Morbidelli, Alessandro; Raymond, Sean N.

2014-01-01

Super-Earths with orbital periods less than 100 days are extremely abundant around Sun-like stars. It is unlikely that these planets formed at their current locations. Rather, they likely formed at large distances from the star and subsequently migrated inward. Here we use N-body simulations to study the effect of super-Earths on the accretion of rocky planets. In our simulations, one or more super-Earths migrate inward through a disk of planetary embryos and planetesimals embedded in a gaseous disk. We tested a wide range of migration speeds and configurations. Fast-migrating super-Earths (τ mig ∼ 0.01-0.1 Myr) only have a modest effect on the protoplanetary embryos and planetesimals. Sufficient material survives to form rocky, Earth-like planets on orbits exterior to the super-Earths'. In contrast, slowly migrating super-Earths shepherd rocky material interior to their orbits and strongly deplete the terrestrial planet-forming zone. In this situation any Earth-sized planets in the habitable zone are extremely volatile-rich and are therefore probably not Earth-like.

The Magnetic Field of Planet Earth

DEFF Research Database (Denmark)

Hulot, G.; Finlay, Chris; Constable, C. G.

2010-01-01

The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks...... yr) to the longest (virtually the age of the Earth) time scales are finally reviewed, underlining the respective roles of the magnetohydodynamics at work in the core, and of the slow dynamic evolution of the planet as a whole....

Earth Sciences' Capacity Building In Developing Countries through International Programmes

Science.gov (United States)

Eder, W.

2007-12-01

Within the framework of "traditional" programmes, like the joint UNESCO-IUGS "International Geoscience Programme" (IGCP), the "International Continental Scientific Drilling Program" (ICDP), the "Integrated Ocean Drilling Program" (IODP) or the "International Lithosphere Programme" (ILP) numerous opportunities are provided to strengthen postgraduate geo-scientific education of representatives from developing countries. Recently established new initiatives, such as the "International Year of Planet Earth" (IYPE) or UNESCO's Global Network of Geoparks complement these in addition as important components to UNESCO's 'Education for All' programme, notably the youth, as well as to the United Nations Decade of Education for Sustainable Development (2005 - 2014). The "International Year of Planet Earth" is a joint initiative of the International Union of Geological Sciences (IUGS) and UNESCO. The central aims and ambitions of the Year, proclaimed for 2008 by the UN General Assembly, are to demonstrate the great potential of the Earth sciences in building a safer, healthier and wealthier society, and to encourage more widespread and effective application of this potential by targeting politicians and other decision-makers, educational systems, and the general public. Promotion of international collaboration, as well as capacity building and training of students of developing countries in all fields of Earth Sciences seem to be the most appropriate way to meet also the challenges of the IYPE. Another opportunity to improve the international recognition of Earth Scinces, also in developing countries, is the use of Geoparks as a promotional tool for education and popularization of Earth Sciences. Geoparks, notably those included in the European and/or Global Geoparks Networks, provide an international platform of cooperation and exchange between experts and practitioners in geological heritage matters, and are as such excellent instruments in highlighting Earth sciences. The

From Extrasolar Planets to Exo-Earths

Science.gov (United States)

Fischer, Debra

2018-06-01

The ancient Greeks debated whether the Earth was unique, or innumerable worlds existed around other Suns. Twenty five years ago, technology and human ingenuity enabled the discovery of the first extrasolar planet candidates. The architectures of these first systems, with gas giant planets in star-skirting orbits, were unexpected and again raised an echo of that ancient question: is the Earth typical or unique? We are interested in this seemingly anthropocentric question because with all of our searching and discoveries, Earth is the only place where life has been found. It is the question of whether life exists elsewhere that energizes the search for exoplanets. The trajectory of this field has been stunning. After a steady stream of detections with the radial velocity method, a burst of discovery was made possible with the NASA Kepler mission. While thousands of smaller planets have now been found, true Earth analogs have eluded robust detection. However, we are sharpening the knives of our technology and without a doubt we now stand at the threshold of detecting hundreds of Earth analogs. Using Gaia, TESS, WFIRST, JWST and new ground-based spectrographs, we will learn the names and addresses of the worlds that orbit nearby stars and we will be ready to probe their atmospheres. We will finally resolve the ancient question of whether life is unique or common.

Electromagnetic behaviour of the earth and planets

International Nuclear Information System (INIS)

McCarthy, A.J.

2002-01-01

Forecast problems of global warming, rising sea-levels, UV enhancement, and solar disruptions of power grids and satellite communications, have been widely discussed. Added to these calamities is the steady decay of the Earth's magnetic radiation shield against high energy particles. A system of solar-induced aperiodic electromagnetic resonances, referred to here as the Debye resonances, is resurrected as the preferred basis for describing the electromagnetic behaviour of the Earth and planets. Debye's two basic solutions to the spherical vector wave equation provide foundations for electromagnetic modes of the terrestrial and gaseous planets respectively in contrast with the separate electric and magnetic approaches usually taken. For those engaged in radiation protection issues, this paper provides the first published account of how the Sun apparently triggers an Earth magnetic shield against its own harmful radiation. Disturbances from the Sun - which are random in terms of polarity, polarisation, amplitude, and occurrence - are considered here to trigger the Debye modes and generate observed planetary electric and magnetic fields. Snapping or reconnection of solar or interplanetary field lines, acting together with the newly conceived magnetospheric transmission lines of recent literature, is suspected as the excitation mechanism. Virtual replacement of free space by plasma, places the electromagnetic behaviour of the Earth and planets under greatly enhanced control from the Sun. From a radiation protection viewpoint, modal theory based on solar-terrestrial coupling provides a new insight into the origin of the Earth's magnetic radiation shield, greater understanding of which is essential to development of global cosmic radiation protection strategies. Should man-made influences unduly increase conductivities of the Earth's magnetosphere, planet Earth could be left with no magnetic radiation shield whatsoever. Copyright (2002) Australasian Radiation Protection

THE OCCURRENCE RATE OF EARTH ANALOG PLANETS ORBITING SUN-LIKE STARS

International Nuclear Information System (INIS)

Catanzarite, Joseph; Shao, Michael

2011-01-01

Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine η Earth , the fraction of Sun-like stars that have planets like Earth. When a planet 'transits' or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler's Science Team has determined sizes, surface temperatures, orbit sizes, and periods for over a thousand new planet candidates. In this paper, we characterize the period probability distribution function of the super-Earth and Neptune planet candidates with periods up to 132 days, and find three distinct period regimes. For candidates with periods below 3 days, the density increases sharply with increasing period; for periods between 3 and 30 days, the density rises more gradually with increasing period, and for periods longer than 30 days, the density drops gradually with increasing period. We estimate that 1%-3% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of 2011 February. This estimate of η Earth is based on extrapolation from a fiducial subsample of the Kepler planet candidates that we chose to be nominally 'complete' (i.e., no missed detections) to the realm of the Earth-like planets, by means of simple power-law models. The accuracy of the extrapolation will improve as more data from the Kepler mission are folded in. Accurate knowledge of η Earth is essential for the planning of future missions that will image and take spectra of Earth-like planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.

New worlds on the horizon: Earth-sized planets close to other stars.

Science.gov (United States)

Gaidos, Eric; Haghighipour, Nader; Agol, Eric; Latham, David; Raymond, Sean; Rayner, John

2007-10-12

The search for habitable planets like Earth around other stars fulfills an ancient imperative to understand our origins and place in the cosmos. The past decade has seen the discovery of hundreds of planets, but nearly all are gas giants like Jupiter and Saturn. Recent advances in instrumentation and new missions are extending searches to planets the size of Earth but closer to their host stars. There are several possible ways such planets could form, and future observations will soon test those theories. Many of these planets we discover may be quite unlike Earth in their surface temperature and composition, but their study will nonetheless inform us about the process of planet formation and the frequency of Earth-like planets around other stars.

Terraforming the Planets and Climate Change Mitigation on Earth

Science.gov (United States)

Toon, O. B.

2008-12-01

Hopefully, purposeful geo-engineering of the Earth will remain a theoretical concept. Of course, we have already inadvertently changed the Earth, and over geologic history life has left an indelible imprint on our planet. We can learn about geo-engineering schemes by reference to Earth history, for example climate changes after volcanic eruptions provide important clues to using sulfates to modify the climate. The terrestrial planets and Titan offer additional insights. For instance, Mars and Venus both have carbon dioxide dominated greenhouses. Both have more than 10 times as much carbon dioxide in their atmospheres as Earth, and both absorb less sunlight than Earth, yet one is much colder than Earth and one is much hotter. These facts provide important insights into carbon dioxide greenhouses that I will review. Mars cools dramatically following planet wide dust storms, and Titan has what is referred to as an anti- greenhouse climate driven by aerosols. These data can be used to reassure us that we can model aerosol caused changes to the climate of a planet, and also provide examples of aerosols offsetting a gas-driven greenhouse effect. People have long considered whether we might make the other planets habitable. While most of the schemes considered belong in the realm of science fiction, it is possible that some schemes might be practical. Terraforming brings to mind a number of issues that are thought provoking, but not so politically charged as geo-engineering. For example: What criteria define habitability, is it enough for people to live in isolated glass enclosures, or do we need to walk freely on the planet? Different creatures have different needs. Is a planet habitable if plants can thrive in the open, or do animals also need to be free? Are the raw materials present on any planet to make it habitable? If not, can we make the materials, or do we have to import them? Is it ethical to change a planetary climate? What if there are already primitive

Planet logy : Towards Comparative Planet logy beyond the Solar Earth System

Science.gov (United States)

Khan, A. H.

2011-10-01

Today Scenario planet logy is a very important concept because now days the scientific research finding new and new planets and our work's range becoming too long. In the previous study shows about 10-12 years the research of planet logy now has changed . Few years ago we was talking about Sun planet, Earth planet , Moon ,Mars Jupiter & Venus etc. included but now the time has totally changed the recent studies showed that mono lakes California find the arsenic food use by micro organism that show that our study is very tiny as compare to planet long areas .We have very well known that arsenic is the toxic agent's and the toxic agent's present in the lakes and micro organism developing and life going on it's a unbelievable point for us but nature always play a magical games. In few years ago Aliens was the story no one believe the Aliens origin but now the aliens showed catch by our space craft and shuttle and every one believe that Aliens origin but at the moment's I would like to mention one point's that we have too more work required because our planet logy has a vast field. Most of the time our scientific mission shows that this planet found liquid oxygen ,this planet found hydrogen .I would like to clear that point's that all planet logy depend in to the chemical and these chemical gave the indication of the life but we are not abele to developed the adaptation according to the micro organism . Planet logy compare before study shows that Sun it's a combination of the various gases combination surrounded in a round form and now the central Sun Planets ,moons ,comets and asteroids In other word we can say that Or Sun has a wide range of the physical and Chemical properties in the after the development we can say that all chemical and physical property engaged with a certain environment and form a various contains like asteroids, moon, Comets etc. Few studies shows that other planet life affected to the out living planet .We can assure with the example the life

The Earth as a Distant Planet A Rosetta Stone for the Search of Earth-Like Worlds

CERN Document Server

Vázquez, M; Montañés Rodríguez, P

2010-01-01

Is the Earth, in some way, special? Or is our planet but one of the millions of other inhabited planets within our galaxy? This is an exciting time to be asking this old question, because for the first time in history, the answer is within reach. In The Earth as a Distant Planet, the authors set themselves as external observers of our Solar System from an astronomical distance. From that perspective, the authors describe how the Earth, the third planet in distance to the central star, can be catalogued as having its own unique features and as capable of sustaining life. The knowledge gained from this original perspective is then applied to the ongoing search for planets outside the solar system, or exoplanets. Since the discovery in 1992 of the first exoplanet, the number of known planets has increased exponentially. Ambitious space missions are already being designed for the characterization of their atmospheres and to explore the possibility that they host life. The exploration of Earth and the rest of the ...

An Earth-sized planet in the habitable zone of a cool star.

Science.gov (United States)

Quintana, Elisa V; Barclay, Thomas; Raymond, Sean N; Rowe, Jason F; Bolmont, Emeline; Caldwell, Douglas A; Howell, Steve B; Kane, Stephen R; Huber, Daniel; Crepp, Justin R; Lissauer, Jack J; Ciardi, David R; Coughlin, Jeffrey L; Everett, Mark E; Henze, Christopher E; Horch, Elliott; Isaacson, Howard; Ford, Eric B; Adams, Fred C; Still, Martin; Hunter, Roger C; Quarles, Billy; Selsis, Franck

2014-04-18

The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star's radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form.

Tidal effects on Earth, Planets, Sun by far visiting moons

Science.gov (United States)

Fargion, Daniele

2016-07-01

The Earth has been formed by a huge mini-planet collision forming our Earth surface and our Moon today. Such a central collision hit was statistically rare. A much probable skimming or nearby encounter by other moons or planets had to occur. Indeed Recent observations suggest that many planetary-mass objects may be present in the outer solar system between the Kuiper belt and the Oort cloud. Gravitational perturbations may occasionally bring them into the inner solar system. Their passage near Earth could have generated gigantic tidal waves, large volcanic eruptions, sea regressions, large meteoritic impacts and drastic changes in global climate. They could have caused the major biological mass extinctions in the past in the geological records. For instance a ten times a terrestrial radius nearby impact scattering by a peripherical encounter by a small moon-like object will force huge tidal waves (hundred meter height), able to lead to huge tsunami and Earth-quake. Moreover the historical cumulative planet hits in larger and wider planets as Juppiter, Saturn, Uranus will leave a trace, as observed, in their tilted spin axis. Finally a large fraction of counter rotating moons in our solar system probe and test such a visiting mini-planet captur origination. In addition the Earth day duration variability in the early past did show a rare discountinuity, very probably indebt to such a visiting planet crossing event. These far planets in rare trajectory to our Sun may, in thousands event capture, also explain sudden historical and recent temperature changes.

How Do Earth-Sized, Short-Period Planets Form?

Science.gov (United States)

Kohler, Susanna

2017-08-01

Matching theory to observation often requires creative detective work. In a new study, scientists have used a clever test to reveal clues about the birth of speedy, Earth-sized planets.Former Hot Jupiters?Artists impression of a hot Jupiter with an evaporating atmosphere. [NASA/Ames/JPL-Caltech]Among the many different types of exoplanets weve observed, one unusual category is that of ultra-short-period planets. These roughly Earth-sized planets speed around their host stars at incredible rates, with periods of less than a day.How do planets in this odd category form? One popular theory is that they were previously hot Jupiters, especially massive gas giants orbiting very close to their host stars. The close orbit caused the planets atmospheres to be stripped away, leaving behind only their dense cores.In a new study, a team of astronomers led by Joshua Winn (Princeton University) has found a clever way to test this theory.Planetary radius vs. orbital period for the authors three statistical samples (colored markers) and the broader sample of stars in the California Kepler Survey. [Winn et al. 2017]Testing MetallicitiesStars hosting hot Jupiters have an interesting quirk: they typically have metallicities that are significantly higher than an average planet-hosting star. It is speculated that this is because planets are born from the same materials as their host stars, and hot Jupiters require the presence of more metals to be able to form.Regardless of the cause of this trend, if ultra-short-period planets are in fact the solid cores of former hot Jupiters, then the two categories of planets should have hosts with the same metallicity distributions. The ultra-short-period-planet hosts should therefore also be weighted to higher metallicities than average planet-hosting stars.To test this, the authors make spectroscopic measurements and gather data for a sample of stellar hosts split into three categories:64 ultra-short-period planets (orbital period shorter than a

Temperate Earth-sized planets transiting a nearby ultracool dwarf star.

Science.gov (United States)

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-12

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

On the possibility of Earth-type habitable planets in the 55 Cancri system.

Science.gov (United States)

von Bloh, W; Cuntz, M; Franck, S; Bounama, C

2003-01-01

We discuss the possibility of Earth-type planets in the planetary system of 55 Cancri, a nearby G8 V star, which is host to two, possibly three, giant planets. We argue that Earth-type planets around 55 Cancri are in principle possible. Several conditions are necessary. First, Earth-type planets must have formed despite the existence of the close-in giant planet(s). In addition, they must be orbitally stable in the region of habitability considering that the stellar habitable zone is relatively close to the star compared to the Sun because of 55 Cancri's low luminosity and may therefore be affected by the close-in giant planet(s). We estimate the likelihood of Earth-type planets around 55 Cancri based on the integrated system approach previously considered, which provides a way of assessing the long-term possibility of photosynthetic biomass production under geodynamic conditions.

The search for life on Earth and other planets.

Science.gov (United States)

Gross, Michael

2012-04-10

As the NASA rover Curiosity approaches Mars on its quest to look for signs of past or present life there and sophisticated instruments like the space telescopes Kepler and CoRoT keep discovering additional, more Earth-like planets orbiting distant stars, science faces the question of how to spot life on other planets. Even here on Earth biotopes remain to be discovered and explored.

International Conference and Advanced School Planet Earth

CERN Document Server

Jeltsch, Rolf; Pinto, Alberto; Viana, Marcelo

2015-01-01

The focus of this volume is research carried out as part of the program Mathematics of Planet Earth, which provides a platform to showcase the essential role of mathematics in addressing planetary problems and creating a context for mathematicians and applied scientists to foster mathematical and interdisciplinary developments that will be necessary to tackle a myriad of issues and meet future global challenges. Earth is a planet with dynamic processes in its mantle, oceans and atmosphere creating climate, causing natural disasters, and influencing fundamental aspects of life and life-supporting systems. In addition to these natural processes, human activity has increased to the point where it influences the global climate, impacts the ability of the planet to feed itself and threatens the stability of these systems. Issues such as climate change, sustainability, man-made disasters, control of diseases and epidemics, management of resources, risk analysis, and global integration have come to the fore. Written...

Selections from 2017: Atmosphere Around an Earth-Like Planet

Science.gov (United States)

Kohler, Susanna

2017-12-01

Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Detection of the Atmosphere of the 1.6 M Exoplanet GJ 1132 bPublished March2017Main takeaway:An atmosphere was detected around the roughly Earth-size exoplanet GJ 1132 b using a telescope at the European Southern Observatory in Chile. A team of scientists led byJohn Southworth (Keele University) found features indicating the presence of an atmosphere in theobservationsof this 1.6-Earth-mass planet as it transits an M-dwarf host star. This is the lowest-mass planet with a detected atmosphere thus far.Why its interesting:M dwarfs are among the most common stars in our galaxy, and weve found manyEarth-sizeexoplanets in or near the habitable zones around M-dwarf hosts. But M dwarfs are also more magnetically active than stars like our Sun, suggesting that the planets in M-dwarfhabitable zones may not be able to support life due to stellar activity eroding their atmospheres. The detection of an atmosphere around GJ 1132 b suggests that some planets orbiting M dwarfsare able to retain their atmospheres which meansthat these planetsmay be an interesting place to search for life after all.How the atmosphere was detected:The measured planetary radius for GJ 1132 b as a function of the wavelength used to observe it. [Southworth et al. 2017]When measuring the radius of GJ 1132 b based on its transits, the authors noticed that the planet appeared to be largerwhen observed in some wavelengths than in others. This can beexplained if the planet has asurface radius of 1.4 Earth radii, overlaid by an atmosphere that extends out another few tenths of an Earth radius. The atmosphere, which may consist of water vapor or methane, is transparent to some wavelengths and absorbs others which is why the apparent size of the planet changes

Earth-based planet finders power up

Science.gov (United States)

Clery, Daniel

2018-01-01

NASA's Kepler spacecraft has racked up thousands of exoplanet discoveries since its launch in 2009, but before Kepler, the workhorses of exoplanet identification were ground-based instruments that measure tiny stellar wobbles caused by the gravity of an orbiting planet. They are now undergoing a quiet renaissance. The new generation of these devices may be precise enough to find a true Earth twin: a planet with the same mass as ours, orbiting a sunlike star once a year. That's something Kepler—sensitive to planet size, but not mass—can't do. Over the past few months, two new third-generation instruments have opened their eyes to the sky and nearly two dozen others are either under construction or have recently begun service.

Our Mission to Planet Earth: A guide to teaching Earth system science

Science.gov (United States)

1994-01-01

Volcanic eruptions, hurricanes, floods, and El Nino are naturally occurring events over which humans have no control. But can human activities cause additional environmental change? Can scientists predict the global impacts of increased levels of pollutants in the atmosphere? Will the planet warm because increased levels of greenhouse gases, produced by the burning of fossil fuels, trap heat and prevent it from being radiated back into space? Will the polar ice cap melt, causing massive coastal flooding? Have humans initiated wholesale climatic change? These are difficult questions, with grave implications. Predicting global change and understanding the relationships among earth's components have increased in priority for the nation. The National Aeronautics and Space Administration (NASA), along with many other government agencies, has initiated long-term studies of earth's atmosphere, oceans, and land masses using observations from satellite, balloon, and aircraft-borne instruments. NASA calls its research program Mission to Planet Earth. Because NASA can place scientific instruments far above earth's surface, the program allows scientists to explore earth's components and their interactions on a global scale.

Spectral fingerprints of Earth-like planets around FGK stars.

Science.gov (United States)

Rugheimer, Sarah; Kaltenegger, Lisa; Zsom, Andras; Segura, Antígona; Sasselov, Dimitar

2013-03-01

We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions.

Astronomy: A small star with an Earth-like planet

Science.gov (United States)

Deming, Drake

2015-11-01

A rocky planet close in size to Earth has been discovered in the cosmic vicinity of our Sun. The small size and proximity of the associated star bode well for studies of the planet's atmosphere. See Letter p.204

Life, hierarchy, and the thermodynamic machinery of planet Earth.

Science.gov (United States)

Kleidon, Axel

2010-12-01

Throughout Earth's history, life has increased greatly in abundance, complexity, and diversity. At the same time, it has substantially altered the Earth's environment, evolving some of its variables to states further and further away from thermodynamic equilibrium. For instance, concentrations in atmospheric oxygen have increased throughout Earth's history, resulting in an increased chemical disequilibrium in the atmosphere as well as an increased redox gradient between the atmosphere and the Earth's reducing crust. These trends seem to contradict the second law of thermodynamics, which states for isolated systems that gradients and free energy are dissipated over time, resulting in a state of thermodynamic equilibrium. This seeming contradiction is resolved by considering planet Earth as a coupled, hierarchical and evolving non-equilibrium thermodynamic system that has been substantially altered by the input of free energy generated by photosynthetic life. Here, I present this hierarchical thermodynamic theory of the Earth system. I first present simple considerations to show that thermodynamic variables are driven away from a state of thermodynamic equilibrium by the transfer of power from some other process and that the resulting state of disequilibrium reflects the past net work done on the variable. This is applied to the processes of planet Earth to characterize the generation and transfer of free energy and its dissipation, from radiative gradients to temperature and chemical potential gradients that result in chemical, kinetic, and potential free energy and associated dynamics of the climate system and geochemical cycles. The maximization of power transfer among the processes within this hierarchy yields thermodynamic efficiencies much lower than the Carnot efficiency of equilibrium thermodynamics and is closely related to the proposed principle of Maximum Entropy Production (MEP). The role of life is then discussed as a photochemical process that generates

Earthlike planets: Surfaces of Mercury, Venus, earth, moon, Mars

Science.gov (United States)

Murray, B.; Malin, M. C.; Greeley, R.

1981-01-01

The surfaces of the earth and the other terrestrial planets of the inner solar system are reviewed in light of the results of recent planetary explorations. Past and current views of the origin of the earth, moon, Mercury, Venus and Mars are discussed, and the surface features characteristic of the moon, Mercury, Mars and Venus are outlined. Mechanisms for the modification of planetary surfaces by external factors and from within the planet are examined, including surface cycles, meteoritic impact, gravity, wind, plate tectonics, volcanism and crustal deformation. The origin and evolution of the moon are discussed on the basis of the Apollo results, and current knowledge of Mercury and Mars is examined in detail. Finally, the middle periods in the history of the terrestrial planets are compared, and future prospects for the exploration of the inner planets as well as other rocky bodies in the solar system are discussed.

The Earth is a Planet Too!

Science.gov (United States)

Cairns, Brian

2014-01-01

When the solar system formed, the sun was 30 dimmer than today and Venus had an ocean. As the sun brightened, a runaway greenhouse effect caused the Venus ocean to boil away. At times when Earth was younger, the sun less bright, and atmospheric CO2 less, Earth froze over (snowball Earth). Earth is in the sweet spot today. Venus is closer to sun than Earth is, but cloud-covered Venus absorbs only 25 of incident sunlight, while Earth absorbs 70. Venus is warmer because it has a thick carbon dioxide atmosphere causing a greenhouse effect of several hundred degrees. Earth is Goldilocks choice among the planets, the one that is just right for life to exist. Not too hot. Not too cold. How does the Earth manage to stay in this habitable range? Is there a Gaia phenomenon keeping the climate in bounds? A nice idea, but it doesnt work. Today, greenhouse gas levels are unprecedented compared to the last 450,000 years.

Kepler-62: a five-planet system with planets of 1.4 and 1.6 Earth radii in the habitable zone.

Science.gov (United States)

Borucki, William J; Agol, Eric; Fressin, Francois; Kaltenegger, Lisa; Rowe, Jason; Isaacson, Howard; Fischer, Debra; Batalha, Natalie; Lissauer, Jack J; Marcy, Geoffrey W; Fabrycky, Daniel; Désert, Jean-Michel; Bryson, Stephen T; Barclay, Thomas; Bastien, Fabienne; Boss, Alan; Brugamyer, Erik; Buchhave, Lars A; Burke, Chris; Caldwell, Douglas A; Carter, Josh; Charbonneau, David; Crepp, Justin R; Christensen-Dalsgaard, Jørgen; Christiansen, Jessie L; Ciardi, David; Cochran, William D; DeVore, Edna; Doyle, Laurance; Dupree, Andrea K; Endl, Michael; Everett, Mark E; Ford, Eric B; Fortney, Jonathan; Gautier, Thomas N; Geary, John C; Gould, Alan; Haas, Michael; Henze, Christopher; Howard, Andrew W; Howell, Steve B; Huber, Daniel; Jenkins, Jon M; Kjeldsen, Hans; Kolbl, Rea; Kolodziejczak, Jeffery; Latham, David W; Lee, Brian L; Lopez, Eric; Mullally, Fergal; Orosz, Jerome A; Prsa, Andrej; Quintana, Elisa V; Sanchis-Ojeda, Roberto; Sasselov, Dimitar; Seader, Shawn; Shporer, Avi; Steffen, Jason H; Still, Martin; Tenenbaum, Peter; Thompson, Susan E; Torres, Guillermo; Twicken, Joseph D; Welsh, William F; Winn, Joshua N

2013-05-03

We present the detection of five planets--Kepler-62b, c, d, e, and f--of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super-Earth-size (1.25 R⊕ planet radius ≤ 2.0 R⊕) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth's orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.

Earth-type planets (Mercury, Venus, and Mars)

Science.gov (United States)

Marov, M. Y.; Davydov, V. D.

1975-01-01

Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.

Planetary protection protecting earth and planets against alien microbes

International Nuclear Information System (INIS)

Leys, N.

2006-01-01

Protecting Earth and planets against the invasion of 'alien life forms' is not military science fiction, but it is the peaceful daily job of engineers and scientists of space agencies. 'Planetary Protection' is preventing microbial contamination of both the target planet and the Earth when sending robots on interplanetary space mission. It is important to preserve the 'natural' conditions of other planets and to not bring with robots 'earthly microbes' (forward contamination) when looking for 'spores of extra terrestrial life'. The Earth and its biosphere must be protected from potential extraterrestrial biological contamination when returning samples of other planets to the Earth (backward contamination). The NASA-Caltech Laboratory for Planetary Protection of Dr. Kasthuri Venkateswaran at the Jet Propulsion Laboratory (JPL) (California, USA) routinely monitors and characterizes the microbes of NASA spacecraft assembly rooms and space robots prior to flight. They have repeatedly isolated Cupriavidus and Ralstonia strains pre-flight from spacecraft assembly rooms (floor and air) and surfaces of space robots such as the Mars Odyssey Orbiter (La Duc et al., 2003). Cupriavidus and Ralstonia strains have also been found in-flight, in ISS cooling water and Shuttle drinking water (Venkateswaran et al., Pyle et al., Ott et al., all unpublished). The main objective of this study is to characterise the Cupriavidus and Ralstonia strains isolated at JPL and compare them to the Cupriavidus metallidurans CH34T model strain, isolated from a Belgian contaminated soil and studied since 25 years at SCK-CEN and to enhance our knowledge by performing additional tests at JPL and gathering information regarding the environmental conditions and the cleaning and isolation methods used in such spacecraft assembling facilities

AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS

Energy Technology Data Exchange (ETDEWEB)

Campante, T. L.; Davies, G. R.; Chaplin, W. J.; Handberg, R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Barclay, T.; Huber, D.; Burke, C. J.; Quintana, E. V. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Swift, J. J. [Department of Astronomy and Department of Planetary Science, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Adibekyan, V. Zh. [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Cochran, W. [Department of Astronomy and McDonald Observatory, The University of Texas at Austin, TX 78712-1205 (United States); Isaacson, H. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S.; Bedding, T. R. [Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Ragozzine, D. [Department of Physics and Space Sciences, Florida Institute of Technology, 150 West University Boulevard, Melbourne, FL 32901 (United States); Riddle, R. [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Baranec, C. [Institute for Astronomy, University of Hawai' i at Mānoa, Hilo, HI 96720-2700 (United States); Basu, S., E-mail: campante@bison.ph.bham.ac.uk [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others

2015-02-01

The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation.

AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS

International Nuclear Information System (INIS)

Campante, T. L.; Davies, G. R.; Chaplin, W. J.; Handberg, R.; Barclay, T.; Huber, D.; Burke, C. J.; Quintana, E. V.; Swift, J. J.; Adibekyan, V. Zh.; Cochran, W.; Isaacson, H.; Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S.; Bedding, T. R.; Ragozzine, D.; Riddle, R.; Baranec, C.; Basu, S.

2015-01-01

The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation

Earth as an extrasolar planet: Earth model validation using EPOXI earth observations.

Science.gov (United States)

Robinson, Tyler D; Meadows, Victoria S; Crisp, David; Deming, Drake; A'hearn, Michael F; Charbonneau, David; Livengood, Timothy A; Seager, Sara; Barry, Richard K; Hearty, Thomas; Hewagama, Tilak; Lisse, Carey M; McFadden, Lucy A; Wellnitz, Dennis D

2011-06-01

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ∼100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ∼10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ∼7% and brightness temperature errors of less than 1 K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be

THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

Energy Technology Data Exchange (ETDEWEB)

Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Bagnulo, S. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Kowalski, P. M. [GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam (Germany); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Sterzik, M. F., E-mail: l.fossati@open.ac.uk, E-mail: C.A.Haswell@open.ac.uk, E-mail: M.R.Patel@open.ac.uk, E-mail: r.busuttil@open.ac.uk, E-mail: sba@arm.ac.uk, E-mail: kowalski@gfz-potsdam.de, E-mail: denis.shulyak@gmail.com, E-mail: msterzik@eso.org [European Southern Observatory, Casilla 19001, Santiago 19 (Chile)

2012-09-20

Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for {approx}8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10{sup 2} (10{sup 4}) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M{sub Sun} white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

International Nuclear Information System (INIS)

Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R.; Bagnulo, S.; Kowalski, P. M.; Shulyak, D. V.; Sterzik, M. F.

2012-01-01

Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for ∼8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10 2 (10 4 ) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M ☉ white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

Origin of the atmospheres of the earth and the planets

Energy Technology Data Exchange (ETDEWEB)

Chen, Z M

1978-06-01

From a systematic analysis of the whole history of the protoplanetary cloud and the observational facts of the earth's atmosphere, new theory is proposed on the origin of the atmospheres of the earth and the planets. For the earth-like planets, there were profound primordial atmospheres originated from the protoplanetary cloud by the accretion of the embryoes of planets. These primordial atmospheres has existed in a time scale of 10/sup 3/ to 10/sup 7/ years and were composed of chemically reducing gases. The presence of such a reducing atmosphere may be of great significance to the theories of cosmogony and the origin of life. The contents are as follows: the escape of the nebulae and the planetary atmospheres, the blowing-off of the atmospheres and the disspiation of gases driven by the solar wind, the accretion of gases by the planetary embryoes, the primordial atmospheres.

Spectra of Earth-like Planets through Geological Evolution around FGKM Stars

Science.gov (United States)

Rugheimer, S.; Kaltenegger, L.

2018-02-01

Future observations of terrestrial exoplanet atmospheres will occur for planets at different stages of geological evolution. We expect to observe a wide variety of atmospheres and planets with alternative evolutionary paths, with some planets resembling Earth at different epochs. For an Earth-like atmospheric time trajectory, we simulate planets from the prebiotic to the current atmosphere based on geological data. We use a stellar grid F0V to M8V ({T}{eff}=7000–2400 K) to model four geological epochs of Earth's history corresponding to a prebiotic world (3.9 Ga), the rise of oxygen at 2.0 Ga and at 0.8 Ga, and the modern Earth. We show the VIS–IR spectral features, with a focus on biosignatures through geological time for this grid of Sun-like host stars and the effect of clouds on their spectra. We find that the observability of biosignature gases reduces with increasing cloud cover and increases with planetary age. The observability of the visible O2 feature for lower concentrations will partly depend on clouds, which, while slightly reducing the feature, increase the overall reflectivity, and thus the detectable flux of a planet. The depth of the IR ozone feature contributes substantially to the opacity at lower oxygen concentrations, especially for the high near-UV stellar environments around F stars. Our results are a grid of model spectra for atmospheres representative of Earth's geological history to inform future observations and instrument design and are available online at http://carlsaganinstitute.org/data/.

Two drastically different climate states on an Earth-like terra-planet

Directory of Open Access Journals (Sweden)

S. Kalidindi

2018-06-01

Full Text Available We study an Earth-like terra-planet (water-limited terrestrial planet with an overland recycling mechanism bringing fresh water back from the high latitudes to the low latitudes. By performing model simulations for such a planet we find two drastically different climate states for the same set of boundary conditions and parameter values: a cold and wet (CW state with dominant low-latitude precipitation and a hot and dry (HD state with only high-latitude precipitation. We notice that for perpetual equinox conditions, both climate states are stable below a certain threshold value of background soil albedo while above the threshold only the CW state is stable. Starting from the HD state and increasing background soil albedo above the threshold causes an abrupt shift from the HD state to the CW state resulting in a sudden cooling of about 35 °C globally, which is of the order of the temperature difference between present day and the Snowball Earth state. When albedo starting from the CW state is reduced down to zero the terra-planet does not shift back to the HD state (no closed hysteresis. This is due to the high cloud cover in the CW state hiding the surface from solar irradiation so that surface albedo has only a minor effect on the top of the atmosphere radiation balance. Additional simulations with present-day Earth's obliquity all lead to the CW state, suggesting a similar abrupt transition from the HD state to the CW state when increasing obliquity from zero. Our study also has implications for the habitability of Earth-like terra-planets. At the inner edge of the habitable zone, the higher cloud cover in the CW state cools the planet and may prevent the onset of a runaway greenhouse state. At the outer edge, the resupply of water at low latitudes stabilizes the greenhouse effect and keeps the planet in the HD state and may prevent water from getting trapped at high latitudes in frozen form. Overall, the existence of bistability in the

International Conference and Advanced School Planet Earth

CERN Document Server

Jeltsch, Rolf; Pinto, Alberto; Viana, Marcelo

2015-01-01

The focus of this volume is research carried out as part of the program Mathematics of Planet Earth, which provides a platform to showcase the essential role of mathematics in addressing problems of an economic and social nature and creating a context for mathematicians and applied scientists to foster mathematical and interdisciplinary developments that will be necessary to tackle a myriad of issues and meet future global economic and social challenges. Earth is a planet with dynamic processes in its mantle, oceans and atmosphere creating climate, causing natural disasters, and influencing fundamental aspects of life and life-supporting systems. In addition to these natural processes, human activity has developed highly complex systems, including economic and financial systems; the World Wide Web; frameworks for resource management, transportation, energy production and utilization; health care delivery, and social organizations. This development has increased to the point where it impacts the stability and ...

A Google Earth Grand Tour of the Terrestrial Planets

Science.gov (United States)

De Paor, Declan; Coba, Filis; Burgin, Stephen

2016-01-01

Google Earth is a powerful instructional resource for geoscience education. We have extended the virtual globe to include all terrestrial planets. Downloadable Keyhole Markup Language (KML) files (Google Earth's scripting language) associated with this paper include lessons about Mercury, Venus, the Moon, and Mars. We created "grand…

GEODYNAMICS AND RATE OF VOLCANISM ON MASSIVE EARTH-LIKE PLANETS

International Nuclear Information System (INIS)

Kite, E. S.; Manga, M.; Gaidos, E.

2009-01-01

We provide estimates of volcanism versus time for planets with Earth-like composition and masses 0.25-25 M + , as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. We use a thermal evolution model, calibrated against Earth, in combination with standard melting models, to explore the dependence of convection-driven decompression mantle melting on planet mass. We show that (1) volcanism is likely to proceed on massive planets with plate tectonics over the main-sequence lifetime of the parent star; (2) crustal thickness (and melting rate normalized to planet mass) is weakly dependent on planet mass; (3) stagnant lid planets live fast (they have higher rates of melting than their plate tectonic counterparts early in their thermal evolution), but die young (melting shuts down after a few Gyr); (4) plate tectonics may not operate on high-mass planets because of the production of buoyant crust which is difficult to subduct; and (5) melting is necessary but insufficient for efficient volcanic degassing-volatiles partition into the earliest, deepest melts, which may be denser than the residue and sink to the base of the mantle on young, massive planets. Magma must also crystallize at or near the surface, and the pressure of overlying volatiles must be fairly low, if volatiles are to reach the surface. If volcanism is detected in the 10 Gyr-old τ Ceti system, and tidal forcing can be shown to be weak, this would be evidence for plate tectonics.

The Runaway Greenhouse Effect on Earth and other Planets

Science.gov (United States)

Rabbette, Maura; Pilewskie, Peter; McKay, Christopher; Young, Robert

2001-01-01

Water vapor is an efficient absorber of outgoing longwave infrared radiation on Earth and is the primary greenhouse gas. Since evaporation increases with increasing sea surface temperature, and the increase in water vapor further increases greenhouse warming, there is a positive feedback. The runaway greenhouse effect occurs if this feedback continues unchecked until all the water has left the surface and enters the atmosphere. For Mars and the Earth the runaway greenhouse was halted when water vapor became saturated with respect to ice or liquid water respectively. However, Venus is considered to be an example of a planet where the runaway greenhouse effect did occur, and it has been speculated that if the solar luminosity were to increase above a certain limit, it would also occur on the Earth. Satellite data acquired during the Earth Radiation Budget Experiment (ERBE) under clear sky conditions shows that as the sea surface temperature (SST) increases, the rate of outgoing infrared radiation at the top of the atmosphere also increases, as expected. Over the pacific warm pool where the SST exceeds 300 K the outgoing radiation emitted to space actually decreases with increasing SST, leading to a potentially unstable system. This behavior is a signature of the runaway greenhouse effect on Earth. However, the SST never exceeds 303K, thus the system has a natural cap which stops the runaway. According to Stefan-Boltzmann's law the amount of heat energy radiated by the Earth's surface is proportional to (T(sup 4)). However, if the planet has a substantial atmosphere, it can absorb all infrared radiation from the lower surface before the radiation penetrates into outer space. Thus, an instrument in space looking at the planet does not detect radiation from the surface. The radiation it sees comes from some level higher up. For the earth#s atmosphere the effective temperature (T(sub e)) has a value of 255 K corresponding to the middle troposphere, above most of the

EVOLUTIONARY TRACKS OF THE CLIMATE OF EARTH-LIKE PLANETS AROUND DIFFERENT MASS STARS

Energy Technology Data Exchange (ETDEWEB)

Kadoya, S.; Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Faculty of Science Bldg. 1 #711, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan)

2016-07-10

The climatic evolution of the Earth depends strongly on the evolution of the insolation from the Sun and the amount of the greenhouse gasses, especially CO{sub 2} in the atmosphere. Here, we investigate the evolution of the climate of hypothetical Earths around stars whose masses are different from the solar mass with a luminosity evolution model of the stars, a mantle degassing model coupled with a parameterized convection model of the planetary interiors, and an energy balance climate model of the planetary surface. In the habitable zone (HZ), the climate of the planets is initially warm or hot, depending on the orbital semimajor axes. We found that, in the inner HZ, the climate of the planets becomes hotter with time owing to the increase in the luminosity of the central stars, while, in the outer HZ, it becomes colder and eventually globally ice-covered owing to the decrease in the CO{sub 2} degassing rate of the planets. The orbital condition for maintaining the warm climate similar to the present Earth becomes very limited, and more interestingly, the planet orbiting in the outer HZ becomes globally ice-covered after a certain critical age (∼3 Gyr for the hypothetical Earth with standard parameters), irrespective of the mass of the central star. This is because the critical age depends on the evolution of the planets and planetary factors, rather than on the stellar mass. The habitability of the Earth-like planet is shown to be limited with age even though it is orbiting within the HZ.

EVOLUTIONARY TRACKS OF THE CLIMATE OF EARTH-LIKE PLANETS AROUND DIFFERENT MASS STARS

International Nuclear Information System (INIS)

Kadoya, S.; Tajika, E.

2016-01-01

The climatic evolution of the Earth depends strongly on the evolution of the insolation from the Sun and the amount of the greenhouse gasses, especially CO_2 in the atmosphere. Here, we investigate the evolution of the climate of hypothetical Earths around stars whose masses are different from the solar mass with a luminosity evolution model of the stars, a mantle degassing model coupled with a parameterized convection model of the planetary interiors, and an energy balance climate model of the planetary surface. In the habitable zone (HZ), the climate of the planets is initially warm or hot, depending on the orbital semimajor axes. We found that, in the inner HZ, the climate of the planets becomes hotter with time owing to the increase in the luminosity of the central stars, while, in the outer HZ, it becomes colder and eventually globally ice-covered owing to the decrease in the CO_2 degassing rate of the planets. The orbital condition for maintaining the warm climate similar to the present Earth becomes very limited, and more interestingly, the planet orbiting in the outer HZ becomes globally ice-covered after a certain critical age (∼3 Gyr for the hypothetical Earth with standard parameters), irrespective of the mass of the central star. This is because the critical age depends on the evolution of the planets and planetary factors, rather than on the stellar mass. The habitability of the Earth-like planet is shown to be limited with age even though it is orbiting within the HZ.

The International Year of Planet Earth (2007-2009):Earth Sciences for Society

Institute of Scientific and Technical Information of China (English)

Eduardo F.J.de Mulder; Ted Nield; Edward Derbyshire

2006-01-01

Natural disasters like the 2004 tsunami bear graphic testimony to the Earth's incredible power. More effective use of geoscientific knowledge can save lives and protect property. Such knowledge also enables us to satisfy, in a sustainable manner,the growing need for Earth's resources by an expanding human population. Such knowledge is readily available in the practical experience and publications of some half a million Earth scientists all over the world, a professional community that is ready and willing to contribute to a safer, healthier and wealthier society if called upon by politicians and decision makers. Professional guidance by Earth scientists is available in many aspects of everyday life including, for example, identification of the best areas for urban expansion, sites to avoid for waste disposal, the location of new underground fresh water resources, and where certain toxic agents implicated in Earth-related diseases may be located, etc.The International Year of Planet Earth (2007-2009) aims to build on existing knowledge and make it more available for the improvement of everyday life, especially in the less developed countries, as expressed in the Year's subtitle: Earth sciences for Society. Ambitious outreach and science programmes constitute the backbone of the International Year, now politically endorsed by all 191 member states of the United Nations Organisation which has proclaimed 2008, the central year of the triennium, as the UN Year of Planet Earth. This paper describes who is behind the initiative,how it will work, and how the political process leading to United Nations proclamation proceeded. It also describes the financial and organisational aspects of the International Year, sets out the commitments necessary for the realization of the Year's ambitions by all nations, and explains how the raising of US$ 20 million will be approached.

Extrasolar Giant Planet in Earth-like Orbit

Science.gov (United States)

1999-07-01

companion . iota Hor b has an orbital period of 320 days. From this period, the known mass of the central star (1.03 solar masses) and the amplitude of the velocity changes, a mass of at least 2.26 times that of planet Jupiter is deduced for the planet. It revolves around the host star in a somewhat elongated orbit (the eccentricity is 0.16). If it were located in our own solar system, this orbit would stretch from just outside the orbit of Venus (at 117 million km or 0.78 Astronomical Units from the Sun) to just outside the orbit of the Earth (the point farthest from the Sun, at 162 million km or 1.08 Astronomical Units) The new giant planet is thus moving in an orbit not unlike that of the Earth. In fact, of all the planets discovered so far, the orbit of iota Hor b is the most Earth-like. Also, with a spectral type of G0 V , its host star is quite similar to the Sun (G2 V). iota Hor b is, however, at least 720 times more massive than the Earth and it is probably more similar to planet Jupiter in our own solar system. While the radial velocity technique described above only determines a minimum value for the planet's mass, an analysis of the velocity with which the star turns around its own axis suggests that the true mass of iota Hor b is unlikely to be much higher. A difficult case Natural phenomena with periods near one solar year always present a particular challenge to astronomers. This is one of the reasons why it has been necessary to observe the iota Hor system for such a long time to be absolutely sure about the present result. First, special care must be taken to verify that the radial velocity variations found in the data are not an artefact of the Earth's movement around the Sun. In any case, the effect of this movement on the measurements must be accurately accounted for; it reaches about ± 30 km/sec over one year, i.e. much larger than the effect of the new planet. In the present case of iota Hor , this was thoroughly tested and any residual influence of

Star Masses and Star-Planet Distances for Earth-like Habitability.

Science.gov (United States)

Waltham, David

2017-01-01

This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M ⊙ planets with at least simple life is 0.57 M ⊙  < M < 1.64 M ⊙ . Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.

Discovery of Temperate Earth-Sized Planets Transiting a Nearby Ultracool Dwarf Star

Science.gov (United States)

Jehin, Emmanuel; Gillon, Michael; Lederer, Susan M.; Delrez, Laetitia; De Wit, Julien; Burdanov, Artem; Van Grootel, Valerie; Burgasser, Adam; Triaud, Amaury; Demory, Brice-Olivier;

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.

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

International Nuclear Information System (INIS)

Rugheimer, S.; Sasselov, D.; Segura, A.; Kaltenegger, L.

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 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

Early Hydrodynamic Escape Limits Rocky Planets to Less Than or Equal to 1.6 Earth Radii

Science.gov (United States)

Lehmer, O. R.; Catling, D. C.

2017-01-01

In the past decade thousands of exoplanet candidates and hundreds of confirmed exoplanets have been found. For sub-Neptune-sized planets, those less than approx. 10 Earth masses, we can separate planets into two broad categories: predominantly rocky planets, and gaseous planets with thick volatile sheaths. Observations and subsequent analysis of these planets show that rocky planets are only found with radii less than approx. 1.6 Earth radii. No rocky planet has yet been found that violates this limit. We propose that hydrodynamic escape of hydrogen rich protoatmospheres, accreted by forming planets, explains the limit in rocky planet size. Following the hydrodynamic escape model employed by Luger et al. (2015), we modelled the XUV driven escape from young planets (less than approx.100 Myr in age) around a Sun-like star. With a simple, first-order model we found that the rocky planet radii limit occurs consistently at approx. 1.6 Earth radii across a wide range of plausible parameter spaces. Our model shows that hydrodynamic escape can explain the observed cutoff between rocky and gaseous planets. Fig. 1 shows the results of our model for rocky planets between 0.5 and 10 Earth masses that accrete 3 wt. % H2/He during formation. The simulation was run for 100 Myr, after that time the XUV flux drops off exponentially and hydrodynamic escape drops with it. A cutoff between rocky planets and gaseous ones is clearly seen at approx. 1.5-1.6 Earth radii. We are only interested in the upper size limit for rocky planets. As such, we assumed pure hydrogen atmospheres and the highest possible isothermal atmospheric temperatures, which will produce an upper limit on the hydrodynamic loss rate. Previous work shows that a reasonable approximation for an upper temperature limit in a hydrogen rich protoatmosphere is 2000-3000 K, consistent with our assumptions. From these results, we propose that the observed dichotomy between mini-Neptunes and rocky worlds is simply explained by

Dynamically hot Super-Earths from outer giant planet scattering

OpenAIRE

Huang, Chelsea X.; Petrovich, Cristobal; Deibert, Emily

2016-01-01

The hundreds of multiple planetary systems discovered by the \\textit{Kepler} mission are typically observed to reside in close-in ($\\lesssim0.5$ AU), low-eccentricity, and low-inclination orbits. We run N-body experiments to study the effect that unstable outer ($\\gtrsim1$ AU) giant planets, whose end orbital configurations resemble those in the Radial Velocity population, have on these close-in multiple super-Earth systems. Our experiments show that the giant planets greatly reduce the multi...

Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST

Science.gov (United States)

Morley, Caroline V.; Kreidberg, Laura; Rustamkulov, Zafar; Robinson, Tyler; Fortney, Jonathan J.

2017-12-01

Nine transiting Earth-sized planets have recently been discovered around nearby late-M dwarfs, including the TRAPPIST-1 planets and two planets discovered by the MEarth survey, GJ 1132b and LHS 1140b. These planets are the smallest known planets that may have atmospheres amenable to detection with the James Webb Space Telescope (JWST). We present model thermal emission and transmission spectra for each planet, varying composition and surface pressure of the atmosphere. We base elemental compositions on those of Earth, Titan, and Venus and calculate the molecular compositions assuming chemical equilibrium, which can strongly depend on temperature. Both thermal emission and transmission spectra are sensitive to the atmospheric composition; thermal emission spectra are sensitive to surface pressure and temperature. We predict the observability of each planet’s atmosphere with JWST. GJ 1132b and TRAPPIST-1b are excellent targets for emission spectroscopy with JWST/MIRI, requiring fewer than 10 eclipse observations. Emission photometry for TRAPPIST-1c requires 5-15 eclipses; LHS 1140b and TRAPPIST-1d, TRAPPIST-1e, and TRAPPIST-1f, which could possibly have surface liquid water, may be accessible with photometry. Seven of the nine planets are strong candidates for transmission spectroscopy measurements with JWST, although the number of transits required depends strongly on the planets’ actual masses. Using the measured masses, fewer than 20 transits are required for a 5σ detection of spectral features for GJ 1132b and six of the TRAPPIST-1 planets. Dedicated campaigns to measure the atmospheres of these nine planets will allow us, for the first time, to probe formation and evolution processes of terrestrial planetary atmospheres beyond our solar system.

Planet earth a beginner's guide

CERN Document Server

Gribbin, John

2012-01-01

In this incredible expedition into the origins, workings, and evolution of our home planet, John Gribbin, bestselling author of In Search of Schrödinger's Cat, The Scientists, and In Search of the Multiverse, does what he does best: taking four and a half billion years of mind-boggling science and digging out the best bits. From the physics of Newton and the geology of Wegener, to the environmentalism of Lovelock, this is a must read for Earth's scientists and residents alike. Trained as an astrophysicist at Cambridge University, John Gribbin is currently Visiting Fellow in Astronomy at the University of Sussex, England.

Occurrence and core-envelope structure of 1-4× Earth-size planets around Sun-like stars.

Science.gov (United States)

Marcy, Geoffrey W; Weiss, Lauren M; Petigura, Erik A; Isaacson, Howard; Howard, Andrew W; Buchhave, Lars A

2014-09-02

Small planets, 1-4× the size of Earth, are extremely common around Sun-like stars, and surprisingly so, as they are missing in our solar system. Recent detections have yielded enough information about this class of exoplanets to begin characterizing their occurrence rates, orbits, masses, densities, and internal structures. The Kepler mission finds the smallest planets to be most common, as 26% of Sun-like stars have small, 1-2 R⊕ planets with orbital periods under 100 d, and 11% have 1-2 R⊕ planets that receive 1-4× the incident stellar flux that warms our Earth. These Earth-size planets are sprinkled uniformly with orbital distance (logarithmically) out to 0.4 the Earth-Sun distance, and probably beyond. Mass measurements for 33 transiting planets of 1-4 R⊕ show that the smallest of them, R planets. Their densities increase with increasing radius, likely caused by gravitational compression. Including solar system planets yields a relation: ρ = 2:32 + 3:19 R=R ⊕ [g cm(-3)]. Larger planets, in the radius range 1.5-4.0 R⊕, have densities that decline with increasing radius, revealing increasing amounts of low-density material (H and He or ices) in an envelope surrounding a rocky core, befitting the appellation ''mini-Neptunes.'' The gas giant planets occur preferentially around stars that are rich in heavy elements, while rocky planets occur around stars having a range of heavy element abundances. Defining habitable zones remains difficult, without benefit of either detections of life elsewhere or an understanding of life's biochemical origins.

Chances for earth-like planets and life around metal-poor stars

OpenAIRE

Zinnecker, Hans

2003-01-01

We discuss the difficulties of forming earth-like planets in metal-poor environments, such as those prevailing in the Galactic halo (Pop II), the Magellanic Clouds, and the early universe. We suggest that, with less heavy elements available, terrestrial planets will be smaller size and lower mass than in our solar system (solar metallicity). Such planets may not be able to sustain life as we know it. Therefore, the chances of very old lifeforms in the universe are slim, and a threshold metall...

Shell of Planet Earth – Global Batch Bioreactor.

Czech Academy of Sciences Publication Activity Database

Hanika, Jiří; Šolcová, Olga; Kaštánek, P.

2017-01-01

Roč. 40, č. 11 (2017), s. 1959-1965 ISSN 0930-7516 R&D Projects: GA TA ČR TE01020080 Institutional support: RVO:67985858 Keywords : critical raw materials * global batch bioreactor * planet earth Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.051, year: 2016

The thermal state and evolution of the earth and terrestrial planets

International Nuclear Information System (INIS)

Tozer, D.C.

1977-01-01

In considering the problem of planetary evolution it is suggested that a completely fresh look at the working of the heat transfer process has made it possible to give a general interpretation of many of the recent discoveries of the Earth's present dynamism and past development without appealing to any but very general assumptions about the material behaviour. Once again, the flow properties of rock are in the forefront of the understanding of the Earth's internal heat while the temperature has somewhat receded into the background as a determined rather than a determining characteristic of the behaviour of the terrestrial planets (Mercury, Venus, Earth, Mars) and the Moon. Misunderstanding about the nature of material properties has made theorists go too far in seeing planets as aggregates of potential laboratory samples, rather than as systems in their own right whose sheer size brings out behaviour requiring distinct ways of describing in situ planetary material. Study of the way in which the evolution of the terrestrial planets becomes regulated by a degree of creep resistance that is quite impossible to measure in the laboratory underlines the similarity of this situation with that which faced attempts to understand stellar evolution. (U.K.)

Gravitational mechanism of active life of the Earth, planets and satellites

Science.gov (United States)

Barkin, Yury

2010-05-01

From positions of geodynamic model of the forced gravitational swing, wobble and displacements of shells of a planet are studied and fundamental problems of geodynamics, geology, geophysics, planetary sciences are solved etc.: 1) The mechanism of cyclic variations of activity of natural processes in various time scales. 2) The power of endogenous activity of planetary natural processes on planets and satellites. 3) The phenomenon of polar inversion of natural processes on planets and satellites. 4) Spasmodic and catastrophic changes of activity of natural processes. 5) The phenomenon of twisting of hemispheres (latitude zones or belts) of celestial bodies. 6) Formation of the pear-shaped form of celestial bodies and the mechanism of its change. 7) The ordered planetary structures of geological formations. 8) The phenomena of bipolarity of celestial bodies and antipodality of geology formations. Mechanism. The fundamental feature of a structure of celestial bodies is their shell structure. The most investigated is the internal structure of the Earth. For the Moon and wide set of other bodies of solar system models of an internal structure have been constructed on the basis of the data of observations obtained at studying of their gravitational fields as a result of realization of the appropriate space missions. The basic components for the majority of celestial bodies are the core, the mantle and the crust. To other shells we concern atmospheres (for example, at Venus, Mars, the Titan etc.) and oceanic shells (the Titan, the Earth, Enceladus etc.). Shells are the complex (composite) formations. Planets and satellites are not spherical celestial bodies. The centers of mass of shells of the given planet (or the satellite) and their appropriate principal axes of inertia do not coincide. Accordingly, all their shells are characterized by the certain dynamic oblatenesses. Differences of dynamical oblatenesses results in various forced influences of external celestial

Mathematical models and methods for planet Earth

CERN Document Server

Locatelli, Ugo; Ruggeri, Tommaso; Strickland, Elisabetta

2014-01-01

In 2013 several scientific activities have been devoted to mathematical researches for the study of planet Earth. The current volume presents a selection of the highly topical issues presented at the workshop “Mathematical Models and Methods for Planet Earth”, held in Roma (Italy), in May 2013. The fields of interest span from impacts of dangerous asteroids to the safeguard from space debris, from climatic changes to monitoring geological events, from the study of tumor growth to sociological problems. In all these fields the mathematical studies play a relevant role as a tool for the analysis of specific topics and as an ingredient of multidisciplinary problems. To investigate these problems we will see many different mathematical tools at work: just to mention some, stochastic processes, PDE, normal forms, chaos theory.

10 years with Planet Earth essence in the primary school children drawings

Science.gov (United States)

D'Addezio, Giuliana

2016-04-01

"10 years with Planet Earth" is the title of the 2016 INGV calendar for primary schools representing the review of a project conceived as support and complement of 15 years long INGV dissemination activities with schools. We realized 10 calendars together with and for primary schools, every year with a subject related to a World in constant evolution. Earthquakes, volcanic eruptions, tsunami waves, magnetic storms and other phenomena are manifestations of the complexity and dynamicity, which began more than four billion years ago and never halted. Since the Earth originated to the first presence of water, life and oxygen, the Cambrian explosion of species, the domain of dinosaurs, the great extinctions and glaciations, the surface of our planet experiences continents collisions, mountains and oceans formation and life forms emerging and disappearing. Every year we have launched a competition asking children to send drawings on themes chosen to stimulate learning about Earth Sciences and Planet Earth dynamics. We intended to raise awareness on issues as water resources availability, protection against natural disasters and control of environmental degradation. For each competition, we chose the most significant drawings to be included in the yearly calendar about the Earth. The authors of drawings were awarded by scientists, journalists, artists and science communicators and even by a minister. Besides the competitions, these drawings depict their own impressions and reflections, providing an opportunity to illustrate the children's point of view. From drawings and texts arise a great consideration and respect for the Planet, raising hopes that similar initiatives can contribute to increase the knowledge of the Earth and of the fragile human ecosystem in the hearts and minds of future active citizens. The project was made possible thanks to the teachers and to the wonderful students of more than 200 schools that sent about 10,000 drawings that have intrigued

Two drastically different climate states on an Earth-like land planet with overland water recycling

Science.gov (United States)

Kalidindi, S.; Reick, C. H.; Raddatz, T.; Claussen, M.

2017-12-01

Prior studies have demonstrated that habitable areas on low-obliquity land planets are confined to the edges of frozen ice caps. Whether such dry planets can maintain long-lived liquid water is unclear. Leconte et al. 2013 argue that on such planets mechanisms like gravity driven ice flows and geothermal flux can maintain liquid water at the edges of thick ice caps and this water may flow back to the lower latitudes through rivers. However, there exists no modelling study which investigates the climate of an Earth-like land planet with an overland recycling mechanism bringing fresh water back from higher to lower latitudes. In our study, by using a comprehensive climate model ICON, we find that an Earth-like land planet with an overland recycling mechanism can exist in two drastically different climate states for the same set of boundary conditions and parameter values: A Cold and Wet (CW) state with dominant low-latitude precipitation and, a Hot and Dry (HD) state with only high-latitude precipitation. For perpetual equinox conditions, both climate states are stable below a certain threshold value of background soil albedo (α) while above that only the CW state is stable. Starting from the HD state and increasing α above the threshold causes an abrupt shift from the HD state to the CW state resulting in a sudden cooling of about 35°C globally which is of the order of the temperature difference between the present-day and the Snowball Earth state. In contrast to the Snowball Earth instability, we find that the sudden cooling in our study is driven by the cloud albedo feedback rather than the snow-albedo feedback. Also, when α in the CW state is reduced back to zero the land planet does not display a closed hysteresis. Our study also has implications for the habitability of Earth-like land planets. At the inner edge of the habitable zone, the higher cloud cover in the CW state cools the planet and may prevent the onset of a runaway greenhouse state. At the outer

The Stability of Hydrogen-Rich Atmospheres of Earth-Like Planets

Science.gov (United States)

Zahnle, Kevin

2016-01-01

Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydro- dynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than 1.6 Earth radii.

Considerations for the habitable zone of super-Earth planets in Gliese 581

OpenAIRE

Chylek, P.; Perez, M. R.

2007-01-01

We assess the possibility that planets Gliese 581 c and d are within the habitable zone. In analogy with our solar system, we use an empirical definition of the habitable zone. We include assumptions such as planetary climates, and atmospheric circulation on gravitationally locked synchronous rotation. Based on the different scenarios, we argue that both planets in Gliese 581 could develop conditions for a habitable zone. In an Earth-like environment planet d could be within a habitable zone,...

The most conserved genome segments for life detection on Earth and other planets.

Science.gov (United States)

Isenbarger, Thomas A; Carr, Christopher E; Johnson, Sarah Stewart; Finney, Michael; Church, George M; Gilbert, Walter; Zuber, Maria T; Ruvkun, Gary

2008-12-01

On Earth, very simple but powerful methods to detect and classify broad taxa of life by the polymerase chain reaction (PCR) are now standard practice. Using DNA primers corresponding to the 16S ribosomal RNA gene, one can survey a sample from any environment for its microbial inhabitants. Due to massive meteoritic exchange between Earth and Mars (as well as other planets), a reasonable case can be made for life on Mars or other planets to be related to life on Earth. In this case, the supremely sensitive technologies used to study life on Earth, including in extreme environments, can be applied to the search for life on other planets. Though the 16S gene has become the standard for life detection on Earth, no genome comparisons have established that the ribosomal genes are, in fact, the most conserved DNA segments across the kingdoms of life. We present here a computational comparison of full genomes from 13 diverse organisms from the Archaea, Bacteria, and Eucarya to identify genetic sequences conserved across the widest divisions of life. Our results identify the 16S and 23S ribosomal RNA genes as well as other universally conserved nucleotide sequences in genes encoding particular classes of transfer RNAs and within the nucleotide binding domains of ABC transporters as the most conserved DNA sequence segments across phylogeny. This set of sequences defines a core set of DNA regions that have changed the least over billions of years of evolution and provides a means to identify and classify divergent life, including ancestrally related life on other planets.

Doppler spectroscopy as a path to the detection of Earth-like planets.

Science.gov (United States)

Mayor, Michel; Lovis, Christophe; Santos, Nuno C

2014-09-18

Doppler spectroscopy was the first technique used to reveal the existence of extrasolar planetary systems hosted by solar-type stars. Radial-velocity surveys led to the detection of a rich population of super-Earths and Neptune-type planets. The numerous detected systems revealed a remarkable diversity. Combining Doppler measurements with photometric observations of planets transiting their host stars further provides access to the planet bulk density, a first step towards comparative exoplanetology. The development of new high-precision spectrographs and space-based facilities will ultimately lead us to characterize rocky planets in the habitable zone of our close stellar neighbours.

THE NASA-UC ETA-EARTH PROGRAM. II. A PLANET ORBITING HD 156668 WITH A MINIMUM MASS OF FOUR EARTH MASSES

International Nuclear Information System (INIS)

Howard, Andrew W.; Marcy, Geoffrey W.; Isaacson, Howard; Johnson, John Asher; Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.

2011-01-01

We report the discovery of HD 156668 b, an extrasolar planet with a minimum mass of M P sin i = 4.15 M + . This planet was discovered through Keplerian modeling of precise radial velocities from Keck-HIRES and is the second super-Earth to emerge from the NASA-UC Eta-Earth Survey. The best-fit orbit is consistent with circular and has a period of P = 4.6455 days. The Doppler semi-amplitude of this planet, K = 1.89 m s -1 , is among the lowest ever detected, on par with the detection of GJ 581 e using HARPS. A longer period (P ∼ 2.3 years), low-amplitude signal of unknown origin was also detected in the radial velocities and was filtered out of the data while fitting the short-period planet. Additional data are required to determine if the long-period signal is due to a second planet, stellar activity, or another source. Photometric observations using the Automated Photometric Telescopes at Fairborn Observatory show that HD 156668 (an old, quiet K3 dwarf) is photometrically constant over the radial velocity period to 0.1 mmag, supporting the existence of the planet. No transits were detected down to a photometric limit of ∼3 mmag, ruling out transiting planets dominated by extremely bloated atmospheres, but not precluding a transiting solid/liquid planet with a modest atmosphere.

Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO2 degassing

International Nuclear Information System (INIS)

Kadoya, S.; Tajika, E.

2014-01-01

Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO 2 degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO 2 degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO 2 degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth

Science.gov (United States)

Batalha, Natalie M.

2018-01-01

A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth "Not too hot, not too cold" begins the prescription for a world that's just right for life as we know it. Finding evidence of life beyond Earth is one of the primary goals of science agencies around the world thanks in large part to NASA's Kepler Mission which launched in 2009 with the objective of finding Goldilocks planets orbiting other stars like our Sun. Indeed, the space telescope opened our eyes to the terrestrial-sized planets that populate the galaxy as well as exotic worlds unlike anything that exists in the solar system. The mission ignited the search for life beyond earth via remote detection of atmospheric biosignatures on exoplanets. Most recently, our collective imagination was awakened by the discovery of Goldilocks worlds orbiting some of the nearest neighbors to the Sun, turning abstractions into destinations. Dr. Batalha will give an overview of the science legacy of the Kepler Mission and other key discoveries. She'll give a preview of what's to come by highlighting the missions soon to launch and those that are concepts taking shape on the drawing board.

Kepler: NASA's First Mission Capable of Finding Earth-Size Planets

Science.gov (United States)

Borucki, William J.

2009-01-01

Kepler, a NASA Discovery mission, is a spaceborne telescope designed to search a nearby region of our galaxy for Earth-size planets orbiting in the habitable zone of stars like our sun. The habitable zone is that region around a start where the temperature permits water to be liquid on the surface of a planet. Liquid water is considered essential forth existence of life. Mission Phases: Six mission phases have been defined to describe the different periods of activity during Kepler's mission. These are: launch; commissioning; early science operations, science operations: and decommissioning

Searching for New Earths: Teaching Children How We Seek Distant Planets

Science.gov (United States)

Pulliam, C.

2008-06-01

Teaching science to children ages 8-13 can be a great challenge, especially if you lack the resources for a full-blown audio/visual presentation. How do you hold their attention and get them involved? One method is to teach a topic no one else covers at this educational level: something exciting and up-to-the-minute, at the cutting edge of science. We developed an interactive 45-minute presentation to convey the two basic techniques used to locate planets orbiting other stars. Activities allowed children to hunt for their own planets in simulated data sets. We also stimulated their imagination by giving each child a take-home, multicolored marble ``planet'' and asking them to discuss their planet's characteristics. The resulting presentation ``Searching for New Earths'' could be adapted to a variety of educational settings.

Hydrodynamics of embedded planets' first atmospheres - III. The role of radiation transport for super-Earth planets

NARCIS (Netherlands)

Cimerman, N.P.; Kuiper, R.; Ormel, Chris W.

2017-01-01

The population of close-in super-Earths, with gas mass fractions of up to 10 per cent represents a challenge for planet formation theory: how did they avoid runaway gas accretion and collapsing to hot Jupiters despite their core masses being in the critical range of Mc ≃ 10 M⊕? Previous

A POPULATION OF VERY HOT SUPER-EARTHS IN MULTIPLE-PLANET SYSTEMS SHOULD BE UNCOVERED BY KEPLER

International Nuclear Information System (INIS)

Schlaufman, Kevin C.; Lin, D. N. C.; Ida, S.

2010-01-01

We simulate a Kepler-like observation of a theoretical exoplanet population and show that the observed orbital period distribution of the Kepler giant planet candidates is best matched by an average stellar specific dissipation function Q' * in the interval 10 6 ∼ * ∼ 7 . In that situation, the few super-Earths that are driven to orbital periods of P < 1 day by dynamical interactions in multiple-planet systems will survive tidal disruption for a significant fraction of the main-sequence lifetimes of their stellar hosts. Consequently, though these very hot super-Earths are not characteristic of the overall super-Earth population, their substantial transit probability implies that they should be significant contributors to the full super-Earth population uncovered by Kepler. As a result, the CoRoT-7 system may be the first representative of a population of very hot super-Earths that we suggest should be found in multiple-planet systems preferentially orbiting the least-dissipative stellar hosts in the Kepler sample.

DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

International Nuclear Information System (INIS)

Eggl, Siegfried; Pilat-Lohinger, Elke; Haghighipour, Nader

2013-01-01

Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the α Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery of α Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the α Centauri system.

DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

Energy Technology Data Exchange (ETDEWEB)

Eggl, Siegfried; Pilat-Lohinger, Elke [University of Vienna, Institute for Astrophysics, Tuerkenschanzstr. 17, A-1180 Vienna (Austria); Haghighipour, Nader, E-mail: siegfried.eggl@univie.ac.at [Institute for Astronomy and NASA Astrobiology Institute, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2013-02-20

Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the {alpha} Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery of {alpha} Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the {alpha} Centauri system.

Extending Whole-earth Tectonics To The Terrestrial Planets

Science.gov (United States)

Baker, V. R.; Maruyama, S.; Dohm, J. M.

Based on the need to explain a great many geological and geophysical anomalies on Mars, and stimulated by the new results from the Mars Global Surveyor Mission, we propose a conceptual model of whole-EARTH (Episodic Annular Revolving Thermal Hydrologic) tectonics for the long-term evolution of terrestrial planets. The theory emphasizes (1) the importance of water in planetary evolution, and (2) the physi- cal transitions in modes of mantle convection in relation to planetary heat produc- tion. Depending on their first-order geophysical parameters and following accretion and differentiation from volatile-rich planetessimals, terrestrial planets should evolve through various stages of mantle convection, including magma ocean, plate tectonic, and stagnant lid processes. If a water ocean is able to condense from the planet's early steam atmosphere, an early regime of plate tectonics will follow the initial magma ocean. This definitely happened on earth, probably on Mars, and possibly on Venus. The Mars history led to transfer of large amounts of water to the mantle during the pe- riod of heavy bombardment. Termination of plate tectonics on Mars during the heavy bombardment period led to initiation of superplumes at Tharsis and Elysium, where long-persistent volcanism and water outbursts dominated much of later Martian his- tory. For Venus, warming of the early sun made the surface ocean unstable, eliminating its early plate-tectonic regime. Although Venus now experiences stagnant-lid convec- tion with episodic mantle overturns, the water subducted to its lower mantle during the ancient plate-tectonic regime manifests itself in the initation of volatile-rich plumes that dominate its current tectonic regime.

Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

Energy Technology Data Exchange (ETDEWEB)

Kadoya, S. [Department of Earth and Planetary Science, The University of Tokyo, Kiban Bldg. 408, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, Kiban Bldg. 409, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

2014-08-01

Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

THE NASA-UC ETA-EARTH PROGRAM. III. A SUPER-EARTH ORBITING HD 97658 AND A NEPTUNE-MASS PLANET ORBITING Gl 785

International Nuclear Information System (INIS)

Howard, Andrew W.; Marcy, Geoffrey W.; Isaacson, Howard; Johnson, John Asher; Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.

2011-01-01

We report the discovery of planets orbiting two bright, nearby early K dwarf stars, HD 97658 and Gl 785. These planets were detected by Keplerian modeling of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth with minimum mass Msin i = 8.2 ± 1.2 M + , orbital period P = 9.494 ± 0.005 days, and an orbit that is consistent with circular. Gl 785 b is a Neptune-mass planet with Msin i = 21.6 ± 2.0 M + , P = 74.39 ± 0.12 days, and orbital eccentricity e = 0.30 ± 0.09. Photometric observations with the T12 0.8 m automatic photometric telescope at Fairborn Observatory show that HD 97658 is photometrically constant at the radial velocity period to 0.09 mmag, supporting the existence of the planet.

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.

Two planets: Earth and Mars - One salt model: The Hydrothermal SCRIW-Model

Science.gov (United States)

Hovland, M. T.; Rueslaatten, H.; Johnsen, H. K.; Indreiten, T.

2011-12-01

One of the common characteristics of planets Earth and Mars is that both host water (H2O) and large accumulations of salt. Whereas Earth's surface-environment can be regarded as 'water-friendly' and 'salt hostile', the reverse can be said for the surface of Mars. This is because liquid water is stable on Earth, and the atmosphere transports humidity around the globe, whereas on planet Mars, liquid water is unstable, rendering the atmosphere dry and, therefore, 'salt-friendly'. The riddle as to how the salt accumulated in various locations on those two planets is one of long-lasting and great debate. The salt accumulations on Earth are traditionally termed 'evaporites', meaning that they formed by the evaporation of large masses of seawater. How the accumulations on Mars formed is much harder to explain, with a similar model, as surface water, representing a large ocean only existed briefly. Although water molecules and OH-groups may exist in abundance in bound form (crystal water, adsorbed water, etc.), the only place where free water is expected to be stable on Mars is within underground faults, fractures, and crevices. Here it likely occurs as brine or in the form of ice. Based on these conditions, a key to understanding the accumulation of large deposits of salt on both planets is linked to how brines behave in the subsurface when pressurized and heated beyond their supercritical point. At depths greater than about 3 km (i.e., a pressure, P>300 bars) water will no longer boil in a steam phase. Rather, it becomes supercritical and will form a supercritical water 'vapor' (SCRIW) with a specific gravity of typically 0.3 g/cm3. An important characteristic of SCRIW is its inability to dissolve the common sea salts. The salt dissolved in the brines will therefore precipitate as solid particles when brines (seawater on the Earth) move into the supercritical P&T-domain (above 400 C and 300 bars). Numerical modeling of a hydrothermal system in the Atlantis II Deep of the

A Population of planetary systems characterized by short-period, Earth-sized planets

Science.gov (United States)

Steffen, Jason H.; Coughlin, Jeffrey L.

2016-01-01

We analyze data from the Quarter 1–17 Data Release 24 (Q1–Q17 DR24) planet candidate catalog from NASA’s Kepler mission, specifically comparing systems with single transiting planets to systems with multiple transiting planets, and identify a population of exoplanets with a necessarily distinct system architecture. Such an architecture likely indicates a different branch in their evolutionary past relative to the typical Kepler system. The key feature of these planetary systems is an isolated, Earth-sized planet with a roughly 1-d orbital period. We estimate that at least 24 of the 144 systems we examined (≳17%) are members of this population. Accounting for detection efficiency, such planetary systems occur with a frequency similar to the hot Jupiters. PMID:27790984

A Population of planetary systems characterized by short-period, Earth-sized planets.

Science.gov (United States)

Steffen, Jason H; Coughlin, Jeffrey L

2016-10-25

We analyze data from the Quarter 1-17 Data Release 24 (Q1-Q17 DR24) planet candidate catalog from NASA's Kepler mission, specifically comparing systems with single transiting planets to systems with multiple transiting planets, and identify a population of exoplanets with a necessarily distinct system architecture. Such an architecture likely indicates a different branch in their evolutionary past relative to the typical Kepler system. The key feature of these planetary systems is an isolated, Earth-sized planet with a roughly 1-d orbital period. We estimate that at least 24 of the 144 systems we examined ([Formula: see text]17%) are members of this population. Accounting for detection efficiency, such planetary systems occur with a frequency similar to the hot Jupiters.

RECONSTRUCTING THE PHOTOMETRIC LIGHT CURVES OF EARTH AS A PLANET ALONG ITS HISTORY

International Nuclear Information System (INIS)

Sanromá, E.; Pallé, E.

2012-01-01

By utilizing satellite-based estimations of the distribution of clouds, we have studied Earth's large-scale cloudiness behavior according to latitude and surface types (ice, water, vegetation, and desert). These empirical relationships are used here to reconstruct the possible cloud distribution of historical epochs of Earth's history such as the Late Cretaceous (90 Ma ago), the Late Triassic (230 Ma ago), the Mississippian (340 Ma ago), and the Late Cambrian (500 Ma ago), when the landmass distributions were different from today's. With this information, we have been able to simulate the globally integrated photometric variability of the planet at these epochs. We find that our simple model reproduces well the observed cloud distribution and albedo variability of the modern Earth. Moreover, the model suggests that the photometric variability of the Earth was probably much larger in past epochs. This enhanced photometric variability could improve the chances for the difficult determination of the rotational period and the identification of continental landmasses for a distant planets.

EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS

Energy Technology Data Exchange (ETDEWEB)

Rugheimer, S. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kaltenegger, L. [Carl Sagan Institute, Cornell University, Ithaca, NY 14853 (United States); Segura, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México (Mexico); Linsky, J. [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309-0440 (United States); Mohanty, S. [Imperial College London, 1010 Blackett Lab, Prince Consort Road, London SW7 2AZ (United Kingdom)

2015-08-10

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T{sub eff} = 2300 K to T{sub eff} = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H{sub 2}O, O{sub 3}, CH{sub 4}, N{sub 2}O, and CH{sub 3}Cl. To observe signatures of life—O{sub 2}/O{sub 3} in combination with reducing species like CH{sub 4}—we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O{sub 2} spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N{sub 2}O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH{sub 3}Cl could become detectable, depending on the depth of the overlapping N{sub 2}O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities.

EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS

International Nuclear Information System (INIS)

Rugheimer, S.; Kaltenegger, L.; Segura, A.; Linsky, J.; Mohanty, S.

2015-01-01

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T eff = 2300 K to T eff = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H 2 O, O 3 , CH 4 , N 2 O, and CH 3 Cl. To observe signatures of life—O 2 /O 3 in combination with reducing species like CH 4 —we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O 2 spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N 2 O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH 3 Cl could become detectable, depending on the depth of the overlapping N 2 O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities

Hydrodynamics of embedded planets' first atmospheres - III. The role of radiation transport for super-Earth planets

Science.gov (United States)

Cimerman, Nicolas P.; Kuiper, Rolf; Ormel, Chris W.

2017-11-01

The population of close-in super-Earths, with gas mass fractions of up to 10 per cent represents a challenge for planet formation theory: how did they avoid runaway gas accretion and collapsing to hot Jupiters despite their core masses being in the critical range of Mc ≃ 10 M⊕? Previous three-dimensional (3D) hydrodynamical simulations indicate that atmospheres of low-mass planets cannot be considered isolated from the protoplanetary disc, contrary to what is assumed in 1D-evolutionary calculations. This finding is referred to as the recycling hypothesis. In this paper, we investigate the recycling hypothesis for super-Earth planets, accounting for realistic 3D radiation hydrodynamics. Also, we conduct a direct comparison in terms of the evolution of the entropy between 1D and 3D geometries. We clearly see that 3D atmospheres maintain higher entropy: although gas in the atmosphere loses entropy through radiative cooling, the advection of high-entropy gas from the disc into the Bondi/Hill sphere slows down Kelvin-Helmholtz contraction, potentially arresting envelope growth at a sub-critical gas mass fraction. Recycling, therefore, operates vigorously, in line with results by previous studies. However, we also identify an `inner core' - in size ≈25 per cent of the Bondi radius - where streamlines are more circular and entropies are much lower than in the outer atmosphere. Future studies at higher resolutions are needed to assess whether this region can become hydrodynamically isolated on long time-scales.

A SUPER-EARTH-SIZED PLANET ORBITING IN OR NEAR THE HABITABLE ZONE AROUND A SUN-LIKE STAR

Energy Technology Data Exchange (ETDEWEB)

Barclay, Thomas; Burke, Christopher J.; Howell, Steve B.; Rowe, Jason F.; Huber, Daniel; Jenkins, Jon M.; Quintana, Elisa V.; Still, Martin; Twicken, Joseph D.; Bryson, Stephen T.; Borucki, William J.; Caldwell, Douglas A.; Clarke, Bruce D.; Christiansen, Jessie L; Coughlin, Jeffrey L. [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States); Isaacson, Howard; Kolbl, Rea; Marcy, Geoffrey W. [Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720 (United States); Ciardi, David [NASA Exoplanet Science Institute, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Fischer, Debra A. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others

2013-05-10

We present the discovery of a super-Earth-sized planet in or near the habitable zone of a Sun-like star. The host is Kepler-69, a 13.7 mag G4V-type star. We detect two periodic sets of transit signals in the 3-year flux time series of Kepler-69, obtained with the Kepler spacecraft. Using the very high precision Kepler photometry, and follow-up observations, our confidence that these signals represent planetary transits is >99.3%. The inner planet, Kepler-69b, has a radius of 2.24{sup +0.44}{sub -0.29} R{sub Circled-Plus} and orbits the host star every 13.7 days. The outer planet, Kepler-69c, is a super-Earth-sized object with a radius of 1.7{sup +0.34}{sub -0.23} R{sub Circled-Plus} and an orbital period of 242.5 days. Assuming an Earth-like Bond albedo, Kepler-69c has an equilibrium temperature of 299 {+-} 19 K, which places the planet close to the habitable zone around the host star. This is the smallest planet found by Kepler to be orbiting in or near the habitable zone of a Sun-like star and represents an important step on the path to finding the first true Earth analog.

Occurrence and core-envelope structure of 1–4× Earth-size planets around Sun-like stars

Science.gov (United States)

Marcy, Geoffrey W.; Weiss, Lauren M.; Petigura, Erik A.; Isaacson, Howard; Howard, Andrew W.; Buchhave, Lars A.

2014-01-01

Small planets, 1–4× the size of Earth, are extremely common around Sun-like stars, and surprisingly so, as they are missing in our solar system. Recent detections have yielded enough information about this class of exoplanets to begin characterizing their occurrence rates, orbits, masses, densities, and internal structures. The Kepler mission finds the smallest planets to be most common, as 26% of Sun-like stars have small, 1–2 R⊕ planets with orbital periods under 100 d, and 11% have 1–2 R⊕ planets that receive 1–4× the incident stellar flux that warms our Earth. These Earth-size planets are sprinkled uniformly with orbital distance (logarithmically) out to 0.4 the Earth–Sun distance, and probably beyond. Mass measurements for 33 transiting planets of 1–4 R⊕ show that the smallest of them, R planets. Their densities increase with increasing radius, likely caused by gravitational compression. Including solar system planets yields a relation: ρ=2.32+3.19R/R⊕ [g cm−3]. Larger planets, in the radius range 1.5–4.0 R⊕, have densities that decline with increasing radius, revealing increasing amounts of low-density material (H and He or ices) in an envelope surrounding a rocky core, befitting the appellation ‘‘mini-Neptunes.’’ The gas giant planets occur preferentially around stars that are rich in heavy elements, while rocky planets occur around stars having a range of heavy element abundances. Defining habitable zones remains difficult, without benefit of either detections of life elsewhere or an understanding of life’s biochemical origins. PMID:24912169

How to save the earth planet. Ecology and human spirit

International Nuclear Information System (INIS)

Al Gore.

1993-01-01

The author has undertaken for 25 years in all the struggles for the environment protection. His ecology competences are worldwide recognized. With ''HOW TO SAVE THE EARTH PLANET'' AL GORE calls for help facing a great importance economic crisis, the consequences of which are dramatic. Beyond the exhaustive report, very well documented on the scientific topics, he proposes a true ecologic ''Marshall PLAN'' at the planet level, and a global reflection followed by precise and concrete measures. In the beginning of the XXIst century the challenge taken up by AL GORE is also a true defence plea for the future. We are all concerned and our children too. 27 refs

Kepler Mission: A Mission to Find Earth-size Planets in the Habitable Zone

Science.gov (United States)

Borucki, W. J.

2003-01-01

The Kepler Mission is a Discovery-class mission designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. It is a wide field of view photometer Schmidt-type telescope with an array of 42 CCDs. It has a 0.95 m aperture and 1.4 m primary and is designed to attain a photometric precision of 2 parts in 10(exp 5) for 12th magnitude solar-like stars for a 6 hr transit duration. It will continuously observe 100,000 main-sequence stars from 9th to 14th magnitude in the Cygnus constellation for a period of four years with a cadence of 4/hour. An additional 250 stars can be monitored at a cadence of l/minute to do astro-seismology of stars brighter than 11.5 mv. The photometer is scheduled to be launched into heliocentric orbit in 2007. When combined with ground-based spectrometric observations of these stars, the positions of the planets relative to the habitable zone can be found. The spectra of the stars are also used to determine the relationships between the characteristics of terrestrial planets and the characteristics of the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. Based on the results of the current Doppler-velocity discoveries, over a thousand giant planets will also be found. Information on the albedos and densities of those giants showing transits will be obtained. At the end of the four year mission, hundreds of Earth-size planets should be discovered in and near the HZ of their stars if such planets are common. A null result would imply that terrestrial planets in the HZ are very rare and that life might also be quite rare.

A scientometric prediction of the discovery of the first potentially habitable planet with a mass similar to Earth.

Science.gov (United States)

Arbesman, Samuel; Laughlin, Gregory

2010-10-04

The search for a habitable extrasolar planet has long interested scientists, but only recently have the tools become available to search for such planets. In the past decades, the number of known extrasolar planets has ballooned into the hundreds, and with it, the expectation that the discovery of the first Earth-like extrasolar planet is not far off. Here, we develop a novel metric of habitability for discovered planets and use this to arrive at a prediction for when the first habitable planet will be discovered. Using a bootstrap analysis of currently discovered exoplanets, we predict the discovery of the first Earth-like planet to be announced in the first half of 2011, with the likeliest date being early May 2011. Our predictions, using only the properties of previously discovered exoplanets, accord well with external estimates for the discovery of the first potentially habitable extrasolar planet and highlight the the usefulness of predictive scientometric techniques to understand the pace of scientific discovery in many fields.

Pioneering Mars: Turning the Red Planet Green with Earth's Smallest Settlers

Science.gov (United States)

Cwikla, Julie; Milroy, Scott; Reider, David; Skelton, Tara

2014-01-01

Pioneering Mars: Turning the Red Planet Green with the Earth's Smallest Settlers (http://pioneeringmars.org) provides a partnership model for STEM (science, technology, engineering, and mathematics) learning that brings university scientists together with high school students to investigate whether cyanobacteria from Antarctica could survive on…

Remote Sensing Data Analytics for Planetary Science with PlanetServer/EarthServer

Science.gov (United States)

Rossi, Angelo Pio; Figuera, Ramiro Marco; Flahaut, Jessica; Martinot, Melissa; Misev, Dimitar; Baumann, Peter; Pham Huu, Bang; Besse, Sebastien

2016-04-01

Planetary Science datasets, beyond the change in the last two decades from physical volumes to internet-accessible archives, still face the problem of large-scale processing and analytics (e.g. Rossi et al., 2014, Gaddis and Hare, 2015). PlanetServer, the Planetary Science Data Service of the EC-funded EarthServer-2 project (#654367) tackles the planetary Big Data analytics problem with an array database approach (Baumann et al., 2014). It is developed to serve a large amount of calibrated, map-projected planetary data online, mainly through Open Geospatial Consortium (OGC) Web Coverage Processing Service (WCPS) (e.g. Rossi et al., 2014; Oosthoek et al., 2013; Cantini et al., 2014). The focus of the H2020 evolution of PlanetServer is still on complex multidimensional data, particularly hyperspectral imaging and topographic cubes and imagery. In addition to hyperspectral and topographic from Mars (Rossi et al., 2014), the use of WCPS is applied to diverse datasets on the Moon, as well as Mercury. Other Solar System Bodies are going to be progressively available. Derived parameters such as summary products and indices can be produced through WCPS queries, as well as derived imagery colour combination products, dynamically generated and accessed also through OGC Web Coverage Service (WCS). Scientific questions translated into queries can be posed to a large number of individual coverages (data products), locally, regionally or globally. The new PlanetServer system uses the the Open Source Nasa WorldWind (e.g. Hogan, 2011) virtual globe as visualisation engine, and the array database Rasdaman Community Edition as core server component. Analytical tools and client components of relevance for multiple communities and disciplines are shared across service such as the Earth Observation and Marine Data Services of EarthServer. The Planetary Science Data Service of EarthServer is accessible on http://planetserver.eu. All its code base is going to be available on GitHub, on

Coagulation calculations of icy planet formation around 0.1-0.5 M {sub ☉} stars: Super-Earths from large planetesimals

Energy Technology Data Exchange (ETDEWEB)

Kenyon, Scott J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Bromley, Benjamin C., E-mail: skenyon@cfa.harvard.edu, E-mail: bromley@physics.utah.edu [Department of Physics, University of Utah, 201 JFB, Salt Lake City, UT 84112 (United States)

2014-01-01

We investigate formation mechanisms for icy super-Earth-mass planets orbiting at 2-20 AU around 0.1-0.5 M {sub ☉} stars. A large ensemble of coagulation calculations demonstrates a new formation channel: disks composed of large planetesimals with radii of 30-300 km form super-Earths on timescales of ∼1 Gyr. In other gas-poor disks, a collisional cascade grinds planetesimals to dust before the largest planets reach super-Earth masses. Once icy Earth-mass planets form, they migrate through the leftover swarm of planetesimals at rates of 0.01-1 AU Myr{sup –1}. On timescales of 10 Myr to 1 Gyr, many of these planets migrate through the disk of leftover planetesimals from semimajor axes of 5-10 AU to 1-2 AU. A few percent of super-Earths might migrate to semimajor axes of 0.1-0.2 AU. When the disk has an initial mass comparable with the minimum-mass solar nebula, scaled to the mass of the central star, the predicted frequency of super-Earths matches the observed frequency.

A scientometric prediction of the discovery of the first potentially habitable planet with a mass similar to Earth.

Directory of Open Access Journals (Sweden)

Samuel Arbesman

Full Text Available BACKGROUND: The search for a habitable extrasolar planet has long interested scientists, but only recently have the tools become available to search for such planets. In the past decades, the number of known extrasolar planets has ballooned into the hundreds, and with it, the expectation that the discovery of the first Earth-like extrasolar planet is not far off. METHODOLOGY/PRINCIPAL FINDINGS: Here, we develop a novel metric of habitability for discovered planets and use this to arrive at a prediction for when the first habitable planet will be discovered. Using a bootstrap analysis of currently discovered exoplanets, we predict the discovery of the first Earth-like planet to be announced in the first half of 2011, with the likeliest date being early May 2011. CONCLUSIONS/SIGNIFICANCE: Our predictions, using only the properties of previously discovered exoplanets, accord well with external estimates for the discovery of the first potentially habitable extrasolar planet and highlight the the usefulness of predictive scientometric techniques to understand the pace of scientific discovery in many fields.

The Now Frontier. Pioneer to Jupiter. Man Links Earth and Planets. Issue No. 1-5.

Science.gov (United States)

1973

This packet of space science instructional materials includes five issues related to the planet Jupiter. Each issue presents factual material about the planet, diagramatic representations of its movements and positions relative to bright stars or the earth, actual photographs and/or tables of data collected relevant to Pioneer 10, the spacecraft…

Two planetary systems with transiting Earth-size and super-Earth planets orbiting late-type dwarf stars

Science.gov (United States)

Alonso, E. Díez; Hernández, J. I. González; Suárez Gómez, S. L.; Aguado, D. S.; González Gutiérrez, C.; Suárez Mascareño, A.; Cabrera-Lavers, A.; González-Nuevo, J.; Toledo-Padrón, B.; Gracia, J.; de Cos Juez, F. J.; Rebolo, R.

2018-06-01

We present two new planetary systems found around cool dwarf stars with data from the K2 mission. The first system was found in K2-XX1 (EPIC 248545986), characterized in this work as M3.0V and observed in the 14th campaign of K2. It consists of three Earth-size transiting planets with radii of 1.1, 1.0 and 1.1 R⊕, showing a compact configuration with orbital periods of 5.24, 7.78 and 10.1 days, close to 2:3:4 resonance. The second was found in K2-XX2 (EPIC 249801827), characterized in this work as M0.5V and observed in the 15th campaign. It consists of two transiting super-Earths with radii 2.0 and 1.8 R⊕ and orbital periods of 6.03 and 20.5 days. The equilibrium temperatures of the atmospheres of these planets are estimated to be in the range of 380-600 K and the amplitudes of signals in transmission spectroscopy are estimated at ˜ 10 ppm.

The Carbonate-Silicate Cycle on Earth-like Planets Near The End Of Their Habitable Lifetimes

Science.gov (United States)

Rushby, A. J.; Mills, B.; Johnson, M.; Claire, M.

2016-12-01

The terrestrial cycle of silicate weathering and metamorphic outgassing buffers atmospheric CO2 and global climate over geological time on Earth. To first order, the operation of this cycle is assumed to occur on Earth-like planets in the orbit of other main-sequence stars in the galaxy that exhibit similar continent/ocean configurations. This has important implications for studies of planetary habitability, atmospheric and climatic evolution, and our understanding of the potential distribution of life in the Universe. We present results from a simple biogeochemical carbon cycle model developed to investigate the operation of the carbonate-silicate cycle under conditions of differing planet mass and position within the radiative habitable zone. An active carbonate-silicate cycle does extend the length of a planet's habitable period through the regulation of the CO2 greenhouse. However, the breakdown of the negative feedback between temperature, pCO2, and weathering rates towards the end of a planet's habitable lifespan results in a transitory regime of `carbon starvation' that would inhibit the ability of oxygenic photoautotrophs to metabolize, and result in the collapse of any putative biosphere supported by these organisms, suggesting an earlier limit for the initiation of inhabitable conditions than when considering temperature alone. This conclusion stresses the importance of considering the full suite of planetary properties when determining potential habitability. A small sample of exoplanets was tested using this model, and the length of their habitable periods were found to be significantly longer than that of the Earth, primarily as a function of the differential rates of stellar evolution expected from their host stars. Furthermore, we carried out statistical analysis of a series of model input parameters, determining that both the mass of the planet and the sensitivity of seafloor weathering processes to dissolved CO2 exhibit significant controls on the

International Year of Planet Earth Cooperating with Other Years in 2007-2009

Science.gov (United States)

de Mulder, E. F.

2006-05-01

After its inception in 2001, the International Year of Planet Earth was proclaimed for 2008 by the UN General Assembly in December 2005. The UN Year will be in the core of a triennium, starting in January 2007 and closing by the end of 2009. Through UN proclamation, it has gained the political support by 191 UN nations. The International Year of Planet Earth was initiated by the International Union of Geological Sciences (IUGS) finding UNESCO's Earth Sciences Division ready as co-initiator. It enjoys the backing of all relevant IUGS's sister unions in ICSU, including IUGG, IGU, IUSS, ISPRS and INQUA among its 12 Founding Partners and AGI, AAPG and AIPG as major USA based international geoscientific organizations. Moreover, the initiative is supported by 26 more geoscientific and other relevant bodies. The aim of the Year, encapsulated in its subtitle Earth sciences for Society, is to build awareness of the relationship between humankind and Planet Earth, and to demonstrate that geoscientists are key players in creating a balanced, sustainable future for both. In this respect it aims to convince politicians to apply the wealth of geodata and information in day-to-day policy making. The International Year includes a Science and an Outreach Programme, both of equal financial size. The ten Science Themes (Groundwater, Hazards, Health, Climate, Resources, Deep Earth, Ocean, Megacities, Soils, and Life) in the Science Programme were selected for their societal impact, their potential for outreach, as well as their multidisciplinary nature and high scientific potential. Brochures with key questions and invitations for scientists to submit project proposals have been printed for each Theme and can be downloaded from www.yearofplanetearth.org. The same bottom-up mode is applied for the Outreach Programme which will operate as a funding body, receiving bids for financial support - for anything from web-based educational resources to commissioning works of art that will help

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.

Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1

Science.gov (United States)

de Wit, Julien; Wakeford, Hannah R.; Lewis, Nikole K.; Delrez, Laetitia; Gillon, Michaël; Selsis, Frank; Leconte, Jérémy; Demory, Brice-Olivier; Bolmont, Emeline; Bourrier, Vincent; Burgasser, Adam J.; Grimm, Simon; Jehin, Emmanuël; Lederer, Susan M.; Owen, James E.; Stamenković, Vlada; Triaud, Amaury H. M. J.

2018-03-01

Seven temperate Earth-sized exoplanets readily amenable for atmospheric studies transit the nearby ultracool dwarf star TRAPPIST-1 (refs 1,2). Their atmospheric regime is unknown and could range from extended primordial hydrogen-dominated to depleted atmospheres3-6. Hydrogen in particular is a powerful greenhouse gas that may prevent the habitability of inner planets while enabling the habitability of outer ones6-8. An atmosphere largely dominated by hydrogen, if cloud-free, should yield prominent spectroscopic signatures in the near-infrared detectable during transits. Observations of the innermost planets have ruled out such signatures9. However, the outermost planets are more likely to have sustained such a Neptune-like atmosphere10, 11. Here, we report observations for the four planets within or near the system's habitable zone, the circumstellar region where liquid water could exist on a planetary surface12-14. These planets do not exhibit prominent spectroscopic signatures at near-infrared wavelengths either, which rules out cloud-free hydrogen-dominated atmospheres for TRAPPIST-1 d, e and f, with significance of 8σ, 6σ and 4σ, respectively. Such an atmosphere is instead not excluded for planet g. As high-altitude clouds and hazes are not expected in hydrogen-dominated atmospheres around planets with such insolation15, 16, these observations further support their terrestrial and potentially habitable nature.

Theory for the Origin and Evolution of Stars and Planets, Including Earth

Science.gov (United States)

Cimorelli, S. A.; Samuels, C.

2001-05-01

In this paper we present a novel hypothesis for the formation and evolution of galaxies, stars (including black holes (BHs), giant, mid-size, dwarf, dying and dead stars), planets (including earth), and moons. Present day phenomenon will be used to substantiate the validity of this hypothesis. Every `body' is a multiple type of star, generated from pieces called particle proliferators, of a dislodged/expanded BH which explodes due to a collision with another expanded BH. This includes the sun, and the planet earth, which is a type of dead star. Such that, if we remove layers of the earth, starting with the crust, we will find evidence of each preceding star formation, such as a brown star, a red star, a white star, a blue star, and the remains of the particle proliferator as the innermost core is reached. We intend to show that the hypothesis is consistent with both the available astronomical data regarding stellar evolution and planetary formation; as well as the evolution of the earth itself, by considerations of the available geophysical data. Where data is not available, reasonably simple experiments will be suggested to demonstrate further the consistency and viability of the hypothesis. Theories are presented to help define and explain phenomenon such as how two (or more) BHs expand and collide to form a small `big bang' (it is postulated that there was a small big bang to form each galaxy). This in turn afforded the material/matter to form all the galactic bodies, including the dark matter. The start and development of the planet earth, initially as an emergent piece from the colliding BHs, is given special attention to explain the continuing expansion/growth that takes place in all stars and planets. Also, to explain the formation of the land, the growing/expanding earth (proportional to the ocean bed growth), the division of the continents, and the formation of the ocean beds (possibly long before the oceans existed). Attempts will be made to explain the

Dependence of the Onset of the Runaway Greenhouse Effect on the Latitudinal Surface Water Distribution of Earth-Like Planets

Science.gov (United States)

Kodama, T.; Nitta, A.; Genda, H.; Takao, Y.; O'ishi, R.; Abe-Ouchi, A.; Abe, Y.

2018-02-01

Liquid water is one of the most important materials affecting the climate and habitability of a terrestrial planet. Liquid water vaporizes entirely when planets receive insolation above a certain critical value, which is called the runaway greenhouse threshold. This threshold forms the inner most limit of the habitable zone. Here we investigate the effects of the distribution of surface water on the runaway greenhouse threshold for Earth-sized planets using a three-dimensional dynamic atmosphere model. We considered a 1 bar atmosphere whose composition is similar to the current Earth's atmosphere with a zonally uniform distribution of surface water. As previous studies have already showed, we also recognized two climate regimes: the land planet regime, which has dry low-latitude and wet high-latitude regions, and the aqua planet regime, which is globally wet. We showed that each regime is controlled by the width of the Hadley circulation, the amount of surface water, and the planetary topography. We found that the runaway greenhouse threshold varies continuously with the surface water distribution from about 130% (an aqua planet) to 180% (the extreme case of a land planet) of the present insolation at Earth's orbit. Our results indicate that the inner edge of the habitable zone is not a single sharp boundary, but a border whose location varies depending on planetary surface condition, such as the amount of surface water. Since land planets have wider habitable zones and less cloud cover, land planets would be good targets for future observations investigating planetary habitability.

Dynamics of the accumulation process of the Earth group of planets: Formation of the reverse rotation of Venus

Science.gov (United States)

Koslov, N. N.; Eneyev, T. M.

1979-01-01

A numerical simulation of the process of formation of the terrestrial planets is carried within the framework of a new theory for the accumulation of planetary and satellite systems. The numerical simulation permitted determining the parameters of the protoplanetary disk from which Mercury, Venus and the Earth were formed as result of the evolution. The acquisition of a slow retrograde rotation for Venus was discovered during the course of the investigation, whereas Mercury and the Earth acquired direct rotation about their axes. Deviations of the semimajor axes of these three planets as well as the masses of the Earth and Venus from the true values are small as a rule (l 10%). It is shown that during the accumulation of the terrestrial planets, there existed a profound relationship between the process of formation of the orbits and masses of the planet and the process of formation of their rotation about their axes. Estimates are presented for the radii of the initial effective bodies and the time of evolution for the terrestrial accumulation zone.

Optical Images of an Exosolar Planet 25 Light-Years from Earth

Science.gov (United States)

Clampin, Mark

2008-01-01

Fomalhaut is a bright star 7.7 parsec (25 light year) from Earth that harbors a belt of cold dust with a structure consistent with gravitational sculpting by an orbiting planet. Here, we present optical observations of an exoplanet candidate. Fomalhaut b. In the plane of the belt, Fomalhaut b lies approximately 119 astronomical units (AU) from the star, and within 18 All of the dust belt. We detect counterclockwise orbital motion using Hubble Space Telescope observations separated by 1.73 years. Dynamical models of the interaction between the planet and the belt indicate that the planet's mass is at most three times that of Jupiter for the belt to avoid gravitational disruption. The flux detected at 0.8 micron flux is also consistent with that of a planet with mass a few limes that of Jupiter. The brightness at 0.6 microns and the lack of detection at longer wavelengths suggest that the detected flux may include starlight reflected off a circumplanetary disk, with dimension comparable to the orbits of the Galilean satellites. We also observed variability of unknown origin at 0.6 microns.

Optical Images of an Exosolar Planet 25 Light Years from Earth

Science.gov (United States)

Kalas, Paul; Graham, James R.; Chiang, Eugene; Fitzgerald, Michael P.; Clampin, Mark; Kite, Edwin S.; Stapelfeldt, Karl; Marois, Christian; Krist, John

2008-01-01

Fomalhaut is a bright star 7.7 parsecs (25 light years) from Earth that harbors a belt of cold dust with a structure consistent with gravitational sculpting by an orbiting planet. Here, we present optical observations of an exoplanet candidate, Fomalhaut b. In the plane of the belt, Fomalhaut b lies approximately 119 astronomical units (AU) from the star and 18 AU from the dust belt, matching predictions. We detect counterclockwise orbital motion using Hubble Space Telescope observations separated by 1.73 years. Dynamical models of the interaction between the planet and the belt indicate that the planet's mass is at most three times that of Jupiter for the belt to avoid gravitational disruption. The flux detected at 0.8 m is also consistent with that of a planet with mass no greater than a few times that of Jupiter. The brightness at 0.6 micron and the lack of detection at longer wavelengths suggest that the detected flux may include starlight reflected off a circumplanetary disk, with dimension comparable to the orbits of the Galilean satellites. We also observed variability of unknown origin at 0.6 micron.

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 (O 2 ), ozone (O 3 ), and methane (CH 4 ). We suggest that the canonical O 2 -CH 4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O 2 /O 3 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 CH 4 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.

Auroral phenomenology and magnetospheric processes earth and other planets

CERN Document Server

Keiling, Andreas; Bagenal, Fran; Karlsson, Tomas

2013-01-01

Published by the American Geophysical Union as part of the Geophysical Monograph Series. Many of the most basic aspects of the aurora remain unexplained. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the diffe

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 O 2 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 O 2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O 2 , whereas in the upper atmosphere, most O 2 is formed abiotically via CO 2 photolysis. The O 2 bistability found by Goldblatt et al. ( 2006 ) is not observed in our calculations likely due to our detailed CH 4 oxidation scheme. We calculate increased CH 4 with increasing O 2 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 O 2 is unique. Mixing, CH 4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O 2 fluxes. Regarding exoplanets, different "states" of O 2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases

Observed properties of extrasolar planets.

Science.gov (United States)

Howard, Andrew W

2013-05-03

Observational surveys for extrasolar planets probe the diverse outcomes of planet formation and evolution. These surveys measure the frequency of planets with different masses, sizes, orbital characteristics, and host star properties. Small planets between the sizes of Earth and Neptune substantially outnumber Jupiter-sized planets. The survey measurements support the core accretion model, in which planets form by the accumulation of solids and then gas in protoplanetary disks. The diversity of exoplanetary characteristics demonstrates that most of the gross features of the solar system are one outcome in a continuum of possibilities. The most common class of planetary system detectable today consists of one or more planets approximately one to three times Earth's size orbiting within a fraction of the Earth-Sun distance.

The effect of lunarlike satellites on the orbital infrared light curves of Earth-analog planets.

Science.gov (United States)

Moskovitz, Nicholas A; Gaidos, Eric; Williams, Darren M

2009-04-01

We have investigated the influence of lunarlike satellites on the infrared orbital light curves of Earth-analog extrasolar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet and determine its orbit. We used an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites are assumed to lack an atmosphere, have a low thermal inertia like that of the Moon, and span a range of plausible radii. The planets are assumed to have thermal and orbital properties that mimic those of Earth, while their obliquities and orbital longitudes of inferior conjunction remain free parameters. Even if the gross thermal properties of the planet can be independently constrained (e.g., via spectroscopy or visible-wavelength detection of specular glint from a surface ocean), only the largest (approximately Mars-sized) lunarlike satellites can be detected by light curve data from a TPF-like instrument (i.e., one that achieves a photometric signal-to-noise ratio of 10 to 20 at infrared wavelengths). Nondetection of a lunarlike satellite can obfuscate the interpretation of a given system's infrared light curve so that it may resemble a single planet with high obliquity, different orbital longitude of vernal equinox relative to inferior conjunction, and in some cases drastically different thermal characteristics. If the thermal properties of the planet are not independently established, then the presence of a lunarlike satellite cannot be inferred from infrared data, which would thus demonstrate that photometric light curves alone can only be used for preliminary study, and the addition of spectroscopic data will be necessary.

Preliminary study on the influence of the tides of planet earth on hydrostatic leveling system

International Nuclear Information System (INIS)

He Xiaoye; Xu Shaofeng; Wang Peng

2012-01-01

Hydrostatic leveling system, used mainly in survey and alignment technology in particle accelerator and monitoring the tides is introduced in this paper. Based on the theory about the ocean tide and earth tide, we analyze effects of the earth tides on a hydrostatic leveling system. From the data obtained from an HLS, and their F are, and finally we verify the influence of the tides of planet earth. (authors)

Survival Function Analysis of Planet Size Distribution

OpenAIRE

Zeng, Li; Jacobsen, Stein B.; Sasselov, Dimitar D.; Vanderburg, Andrew

2018-01-01

Applying the survival function analysis to the planet radius distribution of the Kepler exoplanet candidates, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplanets from large exoplanets above. When combined with the recently-discovered radius gap at 2 Earth radii, it supports the treatment of planets 2-4 Earth rad...

High-resolution simulations of the final assembly of Earth-like planets. 2. Water delivery and planetary habitability.

Science.gov (United States)

Raymond, Sean N; Quinn, Thomas; Lunine, Jonathan I

2007-02-01

The water content and habitability of terrestrial planets are determined during their final assembly, from perhaps 100 1,000-km "planetary embryos " and a swarm of billions of 1-10-km "planetesimals. " During this process, we assume that water-rich material is accreted by terrestrial planets via impacts of water-rich bodies that originate in the outer asteroid region. We present analysis of water delivery and planetary habitability in five high-resolution simulations containing about 10 times more particles than in previous simulations. These simulations formed 15 terrestrial planets from 0.4 to 2.6 Earth masses, including five planets in the habitable zone. Every planet from each simulation accreted at least the Earth's current water budget; most accreted several times that amount (assuming no impact depletion). Each planet accreted at least five water-rich embryos and planetesimals from the past 2.5 astronomical units; most accreted 10-20 water-rich bodies. We present a new model for water delivery to terrestrial planets in dynamically calm systems, with low-eccentricity or low-mass giant planets-such systems may be very common in the Galaxy. We suggest that water is accreted in comparable amounts from a few planetary embryos in a " hit or miss " way and from millions of planetesimals in a statistically robust process. Variations in water content are likely to be caused by fluctuations in the number of water-rich embryos accreted, as well as from systematic effects, such as planetary mass and location, and giant planet properties.

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

Science.gov (United States)

Sanromá, E.; Pallé, E.; García Munõz, A.

2013-04-01

Understanding the spectral and photometric variability of the Earth and the rest of the solar system planets has become of 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 likely 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 Earth's rotation. We found that the evolution from deserts to microbial mats and to land plants produces detectable changes in the globally averaged Earth's reflectance. The variability of each surface type is located in different bands and can induce reflectance changes of up to 40% in period of hours. We conclude that by using photometric observations of an Earth-like planet at different photometric bands it would be possible to discriminate between different surface types. While recent literature proposes the red-edge feature of vegetation near 0.7 μm as a signature for land plants, observations in near-IR bands can be equally or even better suited for this purpose.

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

International Nuclear Information System (INIS)

Sanromá, E.; Pallé, E.; García Munõz, A.

2013-01-01

Understanding the spectral and photometric variability of the Earth and the rest of the solar system planets has become of 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 likely 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 Earth's rotation. We found that the evolution from deserts to microbial mats and to land plants produces detectable changes in the globally averaged Earth's reflectance. The variability of each surface type is located in different bands and can induce reflectance changes of up to 40% in period of hours. We conclude that by using photometric observations of an Earth-like planet at different photometric bands it would be possible to discriminate between different surface types. While recent literature proposes the red-edge feature of vegetation near 0.7 μm as a signature for land plants, observations in near-IR bands can be equally or even better suited for this purpose.

Headlines: Planet Earth: Improving Climate Literacy with Short Format News Videos

Science.gov (United States)

Tenenbaum, L. F.; Kulikov, A.; Jackson, R.

2012-12-01

One of the challenges of communicating climate science is the sense that climate change is remote and unconnected to daily life--something that's happening to someone else or in the future. To help face this challenge, NASA's Global Climate Change website http://climate.nasa.gov has launched a new video series, "Headlines: Planet Earth," which focuses on current climate news events. This rapid-response video series uses 3D video visualization technology combined with real-time satellite data and images, to throw a spotlight on real-world events.. The "Headlines: Planet Earth" news video products will be deployed frequently, ensuring timeliness. NASA's Global Climate Change Website makes extensive use of interactive media, immersive visualizations, ground-based and remote images, narrated and time-lapse videos, time-series animations, and real-time scientific data, plus maps and user-friendly graphics that make the scientific content both accessible and engaging to the public. The site has also won two consecutive Webby Awards for Best Science Website. Connecting climate science to current real-world events will contribute to improving climate literacy by making climate science relevant to everyday life.

Occurrence and core-envelope structure of 1-4x Earth-size planets around Sun-like stars

OpenAIRE

Marcy, Geoffrey W.; Weiss, Lauren M.; Petigura, Erik A.; Isaacson, Howard; Howard, Andrew W.; Buchhave, Lars A.

2014-01-01

Small planets, 1-4x the size of Earth, are extremely common around Sun-like stars, and surprisingly so, as they are missing in our solar system. Recent detections have yielded enough information about this class of exoplanets to begin characterizing their occurrence rates, orbits, masses, densities, and internal structures. The Kepler mission finds the smallest planets to be most common, as 26% of Sun-like stars have small, 1-2 R_e planets with orbital periods under 100 days, and 11% have 1-2...

Habitable zone limits for dry planets.

Science.gov (United States)

Abe, Yutaka; Abe-Ouchi, Ayako; Sleep, Norman H; Zahnle, Kevin J

2011-06-01

Most discussion of habitable planets has focused on Earth-like planets with globally abundant liquid water. For an "aqua planet" like Earth, the surface freezes if far from its sun, and the water vapor greenhouse effect runs away if too close. Here we show that "land planets" (desert worlds with limited surface water) have wider habitable zones than aqua planets. For planets at the inner edge of the habitable zone, a land planet has two advantages over an aqua planet: (i) the tropics can emit longwave radiation at rates above the traditional runaway limit because the air is unsaturated and (ii) the dry air creates a dry stratosphere that limits hydrogen escape. At the outer limits of the habitable zone, the land planet better resists global freezing because there is less water for clouds, snow, and ice. Here we describe a series of numerical experiments using a simple three-dimensional global climate model for Earth-sized planets. Other things (CO(2), rotation rate, surface pressure) unchanged, we found that liquid water remains stable at the poles of a low-obliquity land planet until net insolation exceeds 415 W/m(2) (170% that of modern Earth), compared to 330 W/m(2) (135%) for the aqua planet. At the outer limits, we found that a low-obliquity land planet freezes at 77%, while the aqua planet freezes at 90%. High-obliquity land and aqua planets freeze at 58% and 72%, respectively, with the poles offering the last refuge. We show that it is possible that, as the Sun brightens, an aqua planet like Earth can lose most of its hydrogen and become a land planet without first passing through a sterilizing runaway greenhouse. It is possible that Venus was a habitable land planet as recently as 1 billion years ago.

Culture of peace and care for the Planet Earth as predictors of students’ understanding of chemistry concepts

Directory of Open Access Journals (Sweden)

Ngozi Okafor

2016-05-01

Full Text Available This study focused on how culture of peace and care for the planet earth variables predicted public coeducational secondary school students understanding of chemistry concepts in Anambra State of Nigeria. Three research questions guided the study. It was a survey and correlational research designs that involved sample of 180 drawn from six schools through a three-stage sampling procedures. Culture of Peace and Care for the Planet Earth Questionnaire (CPCPEQ and Chemistry Understanding Test (CUT were used for data collection. Their validity and reliability were determined using Cronbach alpha and Kuder-Richardson formula 20 which gave indices of r=.71 and r= 0.78 respectively. Linear regression and bivariate correlation analyses as well as One-way analysis of variance (ANOVA were used in data analysis. The results showed that for culture of peace, tolerance significantly predicted higher chemistry concepts scores while social movement significantly predicted lower concepts scores on chemistry understanding test. On care for the planet earth, adjusting thermostat significantly predicted higher scores while saving water significantly predicted lower scores on chemistry understanding test. The study recommended setting- up of Visionary Chemists for Environment and Peace Culture (VCEPC in all schools that would sensitize students on how to shun hostility, indoctrination and embracing effective methods of waste disposal. It concludes that everybody should go green, plant more trees, and promote mutual understanding, tolerance, peaceful co-existence and friendly environments as fundamental tips of peace culture and care for the planet earth that foster meaningful understanding of chemistry concepts among secondary school students.

Earth observations during Space Shuttle mission STS-45 Mission to Planet Earth - March 24-April 2, 1992

Science.gov (United States)

Pitts, David E.; Helfert, Michael R.; Lulla, Kamlesh P.; Mckay, Mary F.; Whitehead, Victor S.; Amsbury, David L.; Bremer, Jeffrey; Ackleson, Steven G.; Evans, Cynthia A.; Wilkinson, M. J.

1992-01-01

A description is presented of the activities and results of the Space Shuttle mission STS-45, known as the Mission to Planet Earth. Observations of Mount St. Helens, Manila Bay and Mt. Pinatubo, the Great Salt Lake, the Aral Sea, and the Siberian cities of Troitsk and Kuybyshev are examined. The geological features and effects of human activity seen in photographs of these areas are pointed out.

Making Nature's Wisdom Public: The Affirmation of Planet Earth as a Living Organism.

Science.gov (United States)

Cohen, Michael J.

Planet Earth is a living organism that preserves and regenerates itself and shares information with humans through sensations, feelings, and actions. After early humans migrated from their tropical origins to colder climates, they developed technologies to impose their tropical memories on their new surroundings and lost touch with their ancient…

Development of a Model of Geophysical and Geochemical Controls on Abiotic Carbon Cycling on Earth-Like Planets

Science.gov (United States)

Neveu, M.; Felton, R.; Domagal-Goldman, S. D.; Desch, S. J.; Arney, G. N.

2017-12-01

About 20 Earth-sized planets (0.6-1.6 Earth masses and radii) have now been discovered beyond our solar system [1]. Although such planets are prime targets in the upcoming search for atmospheric biosignatures, their composition, geology, and climate are essentially unconstrained. Yet, developing an understanding of how these factors influence planetary evolution through time and space is essential to establishing abiotic backgrounds against which any deviations can provide evidence for biological activity. To this end, we are building coupled geophysical-geochemical models of abiotic carbon cycling on such planets. Our models are controlled by atmospheric factors such as temperature and composition, and compute interior inputs to atmospheric species. They account for crustal weathering, ocean-atmosphere equilibria, and exchange with the deep interior as a function of planet composition and size (and, eventually, age).Planets in other solar systems differ from the Earth not only in their bulk physical properties, but also likely in their bulk chemical composition [2], which influences key parameters such as the vigor of mantle convection and the near-surface redox state. Therefore, simulating how variations in such parameters affect carbon cycling requires us to simulate the above processes from first principles, rather than by using arbitrary parameterizations derived from observations as is often done with models of carbon cycling on Earth [3] or extrapolations thereof [4]. As a first step, we have developed a kinetic model of crustal weathering using the PHREEQC code [5] and kinetic data from [6]. We will present the ability of such a model to replicate Earth's carbon cycle using, for the time being, parameterizations for surface-interior-atmosphere exchange processes such as volcanism (e.g., [7]).[1] exoplanet.eu, 7/28/2017.[2] Young et al. (2014) Astrobiology 14, 603-626.[3] Lerman & Wu (2008) Kinetics of Global Geochemical Cycles. In Kinetics of Water

Plan for Living on a Restless Planet Sets NASA's Solid Earth Agenda

Science.gov (United States)

Solomon, Sean C.; Baker, Victor R.; Bloxham, Jeremy; Booth, Jeffrey; Donnellan, Andrea; Elachi, Charles; Evans, Diane; Rignot, Eric; Burbank, Douglas; Chao, Benjamin F.; Chave, Alan; Gillespie, Alan; Herring, Thomas; Jeanloz, Raymond; LaBrecque, John; Minster, Bernard; Pittman, Walter C., III; Simons, Mark; Turcotte, Donald L.; Zoback, Mary Lou C.

What are the most important challenges facing solid Earth science today and over the next two decades? And what is the best approach for NASA, in partnership with other agencies, to address those challenges? A new report, Living on a Restless Planet, provides a blueprint for answering these questions. The top priority for a new spacecraft mission in the area of solid Earth science over the next 5 years, according to this report, is a satellite dedicated to Interferometric Synthetic Aperture Radar (InSAR). At the request of NASA, the Solid Earth Science Working Group (SESWG) developed a strategy for the highest priority objectives in solid Earth science for the space agency over the next 25 years. The strategy addresses six challenges that are of fundamental scientific importance, have strong implications for society, and are amenable to substantial progress through a concerted series of scientific observations from space.

Two cultures are better than one: Earth sciences and Art for a better planet sustainability

Science.gov (United States)

Lanza, Tiziana; Rubbia, Giuliana; Negrete, Aquiles

2015-04-01

Climate change, pollution, desertification, natural hazard, animals' extinction are some of the problems we face every day. Very often Science and Technology are charged of the solutions while Art is intended mainly for entertainment. Are we sure this is the right attitude? "Technology is a queer thing. It brings you gifts with one hand, and stabs you in the back with the other", says C.P.Snow, author of a milestone book on the Two Cultures, namely Sciences and Humanities. If Science can drive to a rigorous knowledge of the Earth speaking to people's mind, Technology is Science in action. When individuals act very often the reasons behind their actions are linked to their education, values, sense of beauty, presence or absence of feelings, all things pertaining to the emotional sphere of humans usually addressed by humanistic culture. But if in one hand, Science and Technology cannot be left alone to solve the impelling problems that are deteriorating not only our planet resources but also our quality of life, on the other hand the humanistic culture can find a powerful ally in scientific culture for re-awakening in everybody the sense of beauty, values and respect for the planet. To know Earth is to love Earth, since nature is in itself a work of Art. Earth sciences dig out all the secrets that make our planet a unique place in the Universe we know. Every single phenomena can be seen then in a double face value. An Aurora, for instance, can inspire poetry for its beauty and colors but always remains the result of the interaction between the solar wind and the Earth magnetic field. And, most important, an Aurora will never inspire negative feelings. To make our part in creating a common field between Art and Earth sciences, we have created a blog and a related FaceBook page to collect, browsing the web, all the experiences in this trend, to find out that many scientists and artists are already working in this direction as a final and enjoyable surprise.

THERMAL PHASES OF EARTH-LIKE PLANETS: ESTIMATING THERMAL INERTIA FROM ECCENTRICITY, OBLIQUITY, AND DIURNAL FORCING

International Nuclear Information System (INIS)

Cowan, Nicolas B.; Voigt, Aiko; Abbot, Dorian S.

2012-01-01

In order to understand the climate on terrestrial planets orbiting nearby Sun-like stars, one would like to know their thermal inertia. We use a global climate model to simulate the thermal phase variations of Earth analogs and test whether these data could distinguish between planets with different heat storage and heat transport characteristics. In particular, we consider a temperate climate with polar ice caps (like the modern Earth) and a snowball state where the oceans are globally covered in ice. We first quantitatively study the periodic radiative forcing from, and climatic response to, rotation, obliquity, and eccentricity. Orbital eccentricity and seasonal changes in albedo cause variations in the global-mean absorbed flux. The responses of the two climates to these global seasons indicate that the temperate planet has 3× the bulk heat capacity of the snowball planet due to the presence of liquid water oceans. The obliquity seasons in the temperate simulation are weaker than one would expect based on thermal inertia alone; this is due to cross-equatorial oceanic and atmospheric energy transport. Thermal inertia and cross-equatorial heat transport have qualitatively different effects on obliquity seasons, insofar as heat transport tends to reduce seasonal amplitude without inducing a phase lag. For an Earth-like planet, however, this effect is masked by the mixing of signals from low thermal inertia regions (sea ice and land) with that from high thermal inertia regions (oceans), which also produces a damped response with small phase lag. We then simulate thermal light curves as they would appear to a high-contrast imaging mission (TPF-I/Darwin). In order of importance to the present simulations, which use modern-Earth orbital parameters, the three drivers of thermal phase variations are (1) obliquity seasons, (2) diurnal cycle, and (3) global seasons. Obliquity seasons are the dominant source of phase variations for most viewing angles. A pole-on observer

THERMAL PHASES OF EARTH-LIKE PLANETS: ESTIMATING THERMAL INERTIA FROM ECCENTRICITY, OBLIQUITY, AND DIURNAL FORCING

Energy Technology Data Exchange (ETDEWEB)

Cowan, Nicolas B. [Center for Interdisciplinary Exploration and Research in Astrophysics and Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States); Voigt, Aiko [Max Planck Institute for Meteorology, Bundesstr. 53, D-20146 Hamburg (Germany); Abbot, Dorian S., E-mail: n-cowan@nortwestern.edu [Department of Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

2012-09-20

In order to understand the climate on terrestrial planets orbiting nearby Sun-like stars, one would like to know their thermal inertia. We use a global climate model to simulate the thermal phase variations of Earth analogs and test whether these data could distinguish between planets with different heat storage and heat transport characteristics. In particular, we consider a temperate climate with polar ice caps (like the modern Earth) and a snowball state where the oceans are globally covered in ice. We first quantitatively study the periodic radiative forcing from, and climatic response to, rotation, obliquity, and eccentricity. Orbital eccentricity and seasonal changes in albedo cause variations in the global-mean absorbed flux. The responses of the two climates to these global seasons indicate that the temperate planet has 3 Multiplication-Sign the bulk heat capacity of the snowball planet due to the presence of liquid water oceans. The obliquity seasons in the temperate simulation are weaker than one would expect based on thermal inertia alone; this is due to cross-equatorial oceanic and atmospheric energy transport. Thermal inertia and cross-equatorial heat transport have qualitatively different effects on obliquity seasons, insofar as heat transport tends to reduce seasonal amplitude without inducing a phase lag. For an Earth-like planet, however, this effect is masked by the mixing of signals from low thermal inertia regions (sea ice and land) with that from high thermal inertia regions (oceans), which also produces a damped response with small phase lag. We then simulate thermal light curves as they would appear to a high-contrast imaging mission (TPF-I/Darwin). In order of importance to the present simulations, which use modern-Earth orbital parameters, the three drivers of thermal phase variations are (1) obliquity seasons, (2) diurnal cycle, and (3) global seasons. Obliquity seasons are the dominant source of phase variations for most viewing angles. A

The twin sister planets Venus and Earth why are they so different?

CERN Document Server

Malcuit, Robert J

2014-01-01

This book explains how it came to be that Venus and Earth, while very similar in chemical composition, zonation, size and heliocentric distance from the Sun, are very different in surface environmental conditions. It is argued here that these differences can be accounted for by planetoid capture processes and the subsequent evolution of the planet-satellite system. Venus captured a one-half moon-mass planetoid early in its history in the retrograde direction and underwent its "fatal attraction scenario" with its satellite (Adonis). Earth, on the other hand, captured a moon-mass planetoid (Luna) early in its history in prograde orbit and underwent a benign estrangement scenario with its captured satellite.

IMPACT OF η{sub Earth} ON THE CAPABILITIES OF AFFORDABLE SPACE MISSIONS TO DETECT BIOSIGNATURES ON EXTRASOLAR PLANETS

Energy Technology Data Exchange (ETDEWEB)

Léger, Alain [IAS, Univ. Paris-Sud, Orsay (France); Defrère, Denis [Steward Observatory, Department of Astronomy, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States); Malbet, Fabien [UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, BP 53, F-38041 Grenoble cedex 9 (France); Labadie, Lucas [I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Cologne (Germany); Absil, Olivier, E-mail: Alain.Leger@ias.u-psud.fr [Département d’Astrophysique, Géophysique and Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Liège (Belgium)

2015-08-01

We present an analytic model to estimate the capabilities of space missions dedicated to the search for biosignatures in the atmosphere of rocky planets located in the habitable zone of nearby stars. Relations between performance and mission parameters, such as mirror diameter, distance to targets, and radius of planets, are obtained. Two types of instruments are considered: coronagraphs observing in the visible, and nulling interferometers in the thermal infrared. Missions considered are: single-pupil coronagraphs with a 2.4 m primary mirror, and formation-flying interferometers with 4 × 0.75 m collecting mirrors. The numbers of accessible planets are calculated as a function of η{sub Earth}. When Kepler gives its final estimation for η{sub Earth}, the model will permit a precise assessment of the potential of each instrument. Based on current estimations, η{sub Earth} = 10% around FGK stars and 50% around M stars, the coronagraph could study in spectroscopy only ∼1.5 relevant planets, and the interferometer ∼14.0. These numbers are obtained under the major hypothesis that the exozodiacal light around the target stars is low enough for each instrument. In both cases, a prior detection of planets is assumed and a target list established. For the long-term future, building both types of spectroscopic instruments, and using them on the same targets, will be the optimal solution because they provide complementary information. But as a first affordable space mission, the interferometer looks the more promising in terms of biosignature harvest.

Homes for extraterrestrial life: extrasolar planets.

Science.gov (United States)

Latham, D W

2001-12-01

Astronomers are now discovering giant planets orbiting other stars like the sun by the dozens. But none of these appears to be a small rocky planet like the earth, and thus these planets are unlikely to be capable of supporting life as we know it. The recent discovery of a system of three planets is especially significant because it supports the speculation that planetary systems, as opposed to single orbiting planets, may be common. Our ability to detect extrasolar planets will continue to improve, and space missions now in development should be able to detect earth-like planets.

Asteroid impacts on terrestrial planets: the effects of super-Earths and the role of the ν6 resonance

Science.gov (United States)

Smallwood, Jeremy L.; Martin, Rebecca G.; Lepp, Stephen; Livio, Mario

2018-01-01

With N-body simulations of a planetary system with an asteroid belt, we investigate how the asteroid impact rate on the Earth is affected by the architecture of the planetary system. We find that the ν6 secular resonance plays an important role in the asteroid collision rate with the Earth. Compared to exoplanetary systems, the Solar system is somewhat special in its lack of a super-Earth mass planet in the inner Solar system. We therefore first consider the effects of the presence of a super-Earth in the terrestrial planet region. We find a significant effect for super-Earths with a mass of around 10 M⊕ and a separation greater than about 0.7 au. For a super-Earth which is interior to the Earth's orbit, the number of asteroids colliding with Earth increases the closer the super-Earth is to the Earth's orbit. This is the result of multiple secular resonance locations causing more asteroids to be perturbed on to Earth-crossing orbits. When the super-Earth is placed exterior to Earth's orbit, the collision rate decreases substantially because the ν6 resonance no longer exists in the asteroid belt region. We also find that changing the semimajor axis of Saturn leads to a significant decrease in the asteroid collision rate, though increasing its mass increases the collision rate. These results may have implications for the habitability of exoplanetary systems.

Lonely life of a double planet

Energy Technology Data Exchange (ETDEWEB)

Pearson, Jerome

1988-08-25

The paper concerns extraterrestrial intelligence, and the requirements for a terrestrial planet and life. The effect of the Moon on the Earth, the presence of the Earth's atmosphere and oceans, the Earth's magnetic field, and the Earth's molten core, the distance between the sun and Earth where life is possible, and estimates of the number of habitable planets in the galaxies, are all discussed. (U.K.).

Confirmation of Earth-Mass Planets Orbiting the Millisecond Pulsar PSR B1257 + 12.

Science.gov (United States)

Wolszczan, A

1994-04-22

The discovery of two Earth-mass planets orbiting an old ( approximately 10(9) years), rapidly spinning neutron star, the 6.2-millisecond radio pulsar PSR B1257+12, was announced in early 1992. It was soon pointed out that the approximately 3:2 ratio of the planets' orbital periods should lead to accurately predictable and possibly measurable gravitational perturbations of their orbits. The unambiguous detection of this effect, after 3 years of systematic timing observations of PSR B1257+12 with the 305-meter Arecibo radiotelescope, as well as the discovery of another, moon-mass object in orbit around the pulsar, constitutes irrefutable evidence that the first planetary system around a star other than the sun has been identified.

The problem of iron partition between Earth and Moon during simultaneous formation as a double planet system

Science.gov (United States)

Cassidy, W. A.

1984-01-01

A planetary model is described which requires fractional vapor/liquid condensation, planet accumulation during condensation, a late start for accumulation of the Moon, and volatile accretion to the surfaces of each planet only near the end of the accumulation process. In the model, initial accumulation of small objects is helped if the agglomerating particles are somewhat sticky. Assuming that growth proceeds through this range, agglomeration continues. If the reservoir of vapor is being preferentially depleted in iron by fractional condensation, an iron-rich planetary core forms. As the temperature decreases, condensing material becomes progressively richer in silicates and poorer in iron, forming the silicate-rich mantle of an already differentiated Earth. A second center of agglomeration successfully forms near the growing Earth after most of the iron in the reservoir has been used up. The bulk composition of the Moon then is similar to the outer mantle of the accumulating Earth.

Effect of ''outer'' sources and dissipative processes on abundance of inert gases in atmospheres of the Earth group planets

International Nuclear Information System (INIS)

Pavlov, A.K.

1981-01-01

The problem of abundance of inert gases in atmospheres of the Earth group planets is discussed. It is shown that introduction of He, Ne and 36 Ar into the Mars and Mercury atmospheres with interplanetary dust and from other external sources require the presence of special mechanisms of losses for these gases. For the Mars atmosphere dissipation on atmosphere interaction with solar wind during the periods of anomalously low temperatures is a probable mechanisms of Ne and 36 Ar losses. For the Mercury thermal dissipation for He and polar wind for other inert gases are possible. For all the planets of the Earth group dissipation on interaction with solar wind and introduction with interplanetary dust could play an important role at the early stages of evolution of planets [ru

Equilibrium Temperatures and Albedos of Habitable Earth-Like Planets in a Coupled Atmosphere-Ocean GCM

Science.gov (United States)

Del Genio, Anthony; Way, Michael; Amundsen, David; Sohl, Linda; Fujii, Yuka; Ebihara, Yuka; Kiang, Nancy; Chandler, Mark; Aleinov, Igor; Kelley, Maxwell

2017-01-01

The potential habitability of detected exoplanets is typically assessed using the concept of equilibrium temperature (T[subscript] e) based on cloud-free 1-D models with assumed albedo equal to Earth's (0.3) to determine whether a planet lies in the habitable zone. Incident stellar flux appears to be a better metric for stars unlike the Sun. These estimates, however, ignore the effect of clouds on planetary albedo and the fact that the climates of synchronously rotating planets are not well predicted by 1-D models. Given that most planet candidates that will be detected in the next few years will be tidally locked and orbiting M stars, how might the habitable zone e tailored to better in-form characterization with scarce observing resources?

THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS

International Nuclear Information System (INIS)

Dressing, Courtney D.; Charbonneau, David

2013-01-01

We use the optical and near-infrared photometry from the Kepler Input Catalog to provide improved estimates of the stellar characteristics of the smallest stars in the Kepler target list. We find 3897 dwarfs with temperatures below 4000 K, including 64 planet candidate host stars orbited by 95 transiting planet candidates. We refit the transit events in the Kepler light curves for these planet candidates and combine the revised planet/star radius ratios with our improved stellar radii to revise the radii of the planet candidates orbiting the cool target stars. We then compare the number of observed planet candidates to the number of stars around which such planets could have been detected in order to estimate the planet occurrence rate around cool stars. We find that the occurrence rate of 0.5-4 R ⊕ planets with orbital periods shorter than 50 days is 0.90 +0.04 -0.03 planets per star. The occurrence rate of Earth-size (0.5-1.4 R ⊕ ) planets is constant across the temperature range of our sample at 0.51 -0.05 +0.06 Earth-size planets per star, but the occurrence of 1.4-4 R ⊕ planets decreases significantly at cooler temperatures. Our sample includes two Earth-size planet candidates in the habitable zone, allowing us to estimate that the mean number of Earth-size planets in the habitable zone is 0.15 +0.13 -0.06 planets per cool star. Our 95% confidence lower limit on the occurrence rate of Earth-size planets in the habitable zones of cool stars is 0.04 planets per star. With 95% confidence, the nearest transiting Earth-size planet in the habitable zone of a cool star is within 21 pc. Moreover, the nearest non-transiting planet in the habitable zone is within 5 pc with 95% confidence.

Constraints on planet formation from Kepler’s multiple planet systems

Science.gov (United States)

Quintana, Elisa V.

2015-01-01

The recent haul of hundreds of multiple planet systems discovered by Kepler provides a treasure trove of new clues for planet formation theories. The substantial amount of protoplanetary disk mass needed to form the most commonly observed multi-planet systems - small (Earth-sized to mini-Neptune-sized) planets close to their stars - argues against pure in situ formation and suggests that the planets in these systems must have undergone some form of migration. I will present results from numerical simulations of terrestrial planet formation that aim to reproduce the sizes and architecture of Kepler's multi-planet systems, and will discuss the observed resonances and giant planets (or the lack thereof) associated with these systems.

How to save the earth planet. Ecology and human spirit. Sauver la planete terre. L'ecologie et l'esprit humain

Energy Technology Data Exchange (ETDEWEB)

Al Gore.

1993-01-01

The author has undertaken for 25 years in all the struggles for the environment protection. His ecology competences are worldwide recognized. With ''HOW TO SAVE THE EARTH PLANET'' AL GORE calls for help facing a great importance economic crisis, the consequences of which are dramatic. Beyond the exhaustive report, very well documented on the scientific topics, he proposes a true ecologic ''Marshall PLAN'' at the planet level, and a global reflection followed by precise and concrete measures. In the beginning of the XXIst century the challenge taken up by AL GORE is also a true defence plea for the future. We are all concerned and our children too. 27 refs.

A Population of Very-Hot Super-Earths in Multiple-Planet Systems Should be Uncovered by Kepler

OpenAIRE

Schlaufman, Kevin C.; Lin, D. N. C.; Ida, S.

2010-01-01

We simulate a Kepler-like observation of a theoretical exoplanet population and we show that the observed orbital period distribution of the Kepler giant planet candidates is best matched by an average stellar specific dissipation function Q_* in the interval 10^6 ~< Q_* ~< 10^7. In that situation, the few super-Earths that are driven to orbital periods P < 1 day by dynamical interactions in multiple-planet systems will survive tidal disruption for a significant fraction of the main-sequence ...

Bioremediation at a global scale: from the test tube to planet Earth

OpenAIRE

de Lorenzo, V?ctor; Marli?re, Philippe; Sol?, Ricard

2016-01-01

Summary Planet Earth's biosphere has evolved over billions of years as a balanced bio?geological system ultimately sustained by sunpower and the large?scale cycling of elements largely run by the global environmental microbiome. Humans have been part of this picture for much of their existence. But the industrial revolution started in the XIX century and the subsequent advances in medicine, chemistry, agriculture and communications have impacted such balances to an unprecedented degree ? and ...

INTERACTION OF CLOSE-IN PLANETS WITH THE MAGNETOSPHERE OF THEIR HOST STARS. II. SUPER-EARTHS AS UNIPOLAR INDUCTORS AND THEIR ORBITAL EVOLUTION

International Nuclear Information System (INIS)

Laine, Randy O.; Lin, Douglas N. C.

2012-01-01

Planets with several Earth masses and orbital periods of a few days have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, an important evolution issue is the efficiency of their retention in the proximity of their host stars. If these 'super-Earths' attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction of these planets would have encountered an intense stellar magnetic field. These rocky planets have a higher conductivity than the atmosphere of their host stars and, therefore, the magnetic flux tube connecting them would slip though the envelope of the host stars faster than across the planets. The induced electromotive force across the planet's diameter leads to a potential drop which propagates along a flux tube away from the planet with an Alfvén speed. The foot of the flux tube would sweep across the stellar surface and the potential drop across the field lines drives a DC current analogous to that proposed for the electrodynamics of the Io-Jupiter system. The ohmic dissipation of this current produces potentially observable hot spots in the star envelope. It also heats the planet and leads to a torque which drives the planet's orbit to evolve toward both circularization and a state of synchronization with the spin of the star. The net effect is the damping of the planet's orbital eccentricity. Around slowly (or rapidly) spinning stars, this process also causes rocky planets with periods less than a few days to undergo orbital decay (or expansion/stagnation) within a few Myr. In principle, this effect can determine the retention efficiency of short-period hot Earths. We also estimate the ohmic dissipation interior to these planets and show that it can lead to severe structure evolution and potential loss of volatile material in them. However, these effects may be significantly weakened by the reconnection of the induced field.

A Novel Theory For The Origin And Evolution Of Stars And Planets, Including Earth, Which Asks, 'Was The Earth Once A Small Bright Star?'

Science.gov (United States)

Cimorelli, S. A.; Samuels, C.

2001-12-01

Improved prediction methods for earthquakes and volcanic activity will naturally follow from our theory, based on new concepts of the earth's interior composition, state and activity. In this paper we present a novel hypothesis for the formation and evolution of galaxies, stars (including black holes (BHs), neutron stars, giant, mid-size, dwarf, dying and dead stars), planets (including earth), and moons. Present day phenomenon will be used to substantiate the validity of this hypothesis. Every `body' is a multiple type of star, generated from modified pieces called particle proliferators, of a dislodged/expanded BH (of category 2 (c-2)) which explodes due to a collision with another expanded BH (or explodes on its own). This includes the sun, and the planet earth, which is a type of dead star. Such that, if we remove layers of the earth, starting with the crust, we will find evidence of each preceding star formation, from brown to blue, and the remains of the particle proliferator as the innermost core is reached. We show that the hypothesis is consistent with both the available astronomical data regarding stellar evolution and planetary formation; as well as the evolution of the earth itself, by considerations of the available geophysical data. Where data is not available, reasonably simple experiments are suggested to demonstrate further the consistency and viability of the hypothesis. Theories are presented to help define and explain phenomenon such as how two (or more) c-2 BHs expand and collide to form a small `big bang' (It is postulated that there was a small big bang to form each galaxy, similar to the big bang from a category 1 BH(s) that may have formed our universe. The Great Attractors would be massive c-2 BHs and act on galaxy clusters similar to the massive c-3 BHs at the center of Galaxies acting on stars.). This in turn afforded the material/matter to form all the galactic bodies, including the dark matter inside the galaxies that we catalogue as

Exoplanet dynamics. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars.

Science.gov (United States)

Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

2015-02-06

Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets' rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere. Copyright © 2015, American Association for the Advancement of Science.

Do Inner Planets Modulate the Space Environment of the Earth?

Directory of Open Access Journals (Sweden)

Jung-Hee Kim

2014-03-01

Full Text Available Variabilities in the solar wind cause disturbances throughout the heliosphere on all temporal and spatial scales, which leads to changeable space weather. As a view of space weather forecasting, in particular, it is important to know direct and indirect causes modulating the space environment near the Earth in advance. Recently, there are discussions on a role of the interaction of the solar wind with Mercury in affecting the solar wind velocity in the Earth’s neighborhood during its inferior conjunctions. In this study we investigate a question of whether other parameters describing the space environment near the Earth are modulated by the inner planets’ wake, by examining whether the interplanetary magnetic field and the proton density in the solar wind observed by the Advanced Composition Explorer (ACE spacecraft, and the geomagnetic field via the Dst index and Auroral Electrojet index (AE index are dependent upon the relative position of the inner planets. We find there are indeed apparent variations. For example, the mean variations of the geomagnetic fields measured in the Earth’s neighborhood apparently have varied with a timescale of about 10 to 25 days. Those variations in the parameters we have studied, however, turn out to be a part of random fluctuations and have nothing to do with the relative position of inner planets. Moreover, it is found that variations of the proton density in the solar wind, the Dst index, and the AE index are distributed with the Gaussian distribution. Finally, we point out that some of properties in the behavior of the random fluctuation are to be studied.

The lonely life of a double planet

International Nuclear Information System (INIS)

Pearson, Jerome

1988-01-01

The paper concerns extraterrestrial intelligence, and the requirements for a terrestrial planet and life. The effect of the Moon on the Earth, the presence of the Earth's atmosphere and oceans, the Earth's magnetic field, and the Earth's molten core, the distance between the sun and Earth where life is possible, and estimates of the number of habitable planets in the galaxies, are all discussed. (U.K.)

The New Worlds Observer: An Optimal Path to Direct Study of Earth-like Planets

Science.gov (United States)

Cash, Webster C., Jr.; New Worlds Study Team

2009-01-01

Direct detection and spectroscopic study of the planets around the nearby stars is generally recognized as a prime goal of astronomy. The New Worlds Observer mission concept is being studied as an Astrophysics Strategic Mission Concept Study for this purpose. NWO features two spacecraft: a general purpose 4m telescope that operates from the UV to the Near IR, and a starshade, a flower-shaped occulter about 50m in diameter flying in alignment about 70,000km away. Our study shows this is the most effective way to map nearby planetary systems. In this poster we will show that NWO can return much more science than any of the competing approaches at any given price point. Images will show dust and debris down to a fraction of our zodiacal light level. Planets fainter than the Earth can be seen from the Habitable Zone outward, at distances up to 20pc. High throughput and low noise enable immediate follow-up spectroscopy of discovered planets. NWO can discover many more Earth-like planets than all competing approaches including astrometric, interferometric, and internal coronagraphic. Within hours of discovery, a high quality spectrum can determine the true nature of the exoplanet and open the search for biomarkers and life. Over half of the time will be spent with the starshade in transit to the next target. During those times the telescope will be available to for general astrophysics purposes. Operating from the ultraviolet to the near infrared, this will be a true HST follow-on. The study shows all needed technologies already exist. The cost scales primarily with telescope size. The mission is definitely within the financial and technical reach of NASA for the coming decade.

Differentiation of crusts and cores of the terrestrial planets: lessons for the early Earth

International Nuclear Information System (INIS)

Solomon, S.C.

1980-01-01

It now appears probable that all of the terrestrial planets underwent some form of global chemical differentiation to produce crusts, mantles, and cores of variable relative mass fractions. There is direct seismic evidence for a crust on the Moon, and indirect evidence for distinct crusts on Mars and Venus. Substantial portions of these crusts have been in place since the time that heavy bombardment of the inner solar system ceased approximately 4 Ga ago. There is direct evidence for a sizeable core on Mars, indirect evidence for one on Mercury, and bounds on a possible small core for the Moon. Core formation is an important heat source confined to times prior to 4 Ga ago for Mercury and the Earth, but was not closely linked to crustal formation on the Moon nor, apparently, on Mars. The tectonic and volcanic histories of the surfaces of the terrestrial planets Moon, Mars, and Mercury can be used, with simple thermal history models, to restrict the earliest chemical differentiation to be shallow (outer 200-400 km) for the first two bodies and much more extensive for Mercury. Extension of these models to an Earth-size planet leads to the prediction of a hot and vigorously convecting mantle with an easily deformable crust immediately following core formation, and of the gradual development of a lithosphere and of plates with some lateral rigidity in Late Archean-Proterzoic times. (Auth.)

Kepler Mission: a Discovery-Class Mission Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-Like Stars

Science.gov (United States)

Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Caldwell, Douglas; Kondo, Yoji;

THE FIRST PLANETS: THE CRITICAL METALLICITY FOR PLANET FORMATION

International Nuclear Information System (INIS)

Johnson, Jarrett L.; Li Hui

2012-01-01

A rapidly growing body of observational results suggests that planet formation takes place preferentially at high metallicity. In the core accretion model of planet formation this is expected because heavy elements are needed to form the dust grains which settle into the midplane of the protoplanetary disk and coagulate to form the planetesimals from which planetary cores are assembled. As well, there is observational evidence that the lifetimes of circumstellar disks are shorter at lower metallicities, likely due to greater susceptibility to photoevaporation. Here we estimate the minimum metallicity for planet formation, by comparing the timescale for dust grain growth and settling to that for disk photoevaporation. For a wide range of circumstellar disk models and dust grain properties, we find that the critical metallicity above which planets can form is a function of the distance r at which the planet orbits its host star. With the iron abundance relative to that of the Sun [Fe/H] as a proxy for the metallicity, we estimate a lower limit for the critical abundance for planet formation of [Fe/H] crit ≅ –1.5 + log (r/1 AU), where an astronomical unit (AU) is the distance between the Earth and the Sun. This prediction is in agreement with the available observational data, and carries implications for the properties of the first planets and for the emergence of life in the early universe. In particular, it implies that the first Earth-like planets likely formed from circumstellar disks with metallicities Z ∼> 0.1 Z ☉ . If planets are found to orbit stars with metallicities below the critical metallicity, this may be a strong challenge to the core accretion model.

Modelos del planeta Tierra en escolares rurales de Chile / Planet Earth models about students in rural schools from Chile

Directory of Open Access Journals (Sweden)

Paula Alonqueo Boudon

2015-12-01

Full Text Available RESUMEN El presente estudio tuvo como objetivo identificar los modelos del planeta Tierra en escolares mapuches y no mapuches de procedencia rural. Los participantes fueron 40 escolares distribuidos en dos grupos de edad, quienes respondieron a una tarea cognitiva que indaga la representación de la forma del planeta Tierra. En base al grado de acuerdo con la representación científica, cada participante fue categorizado en uno de cuatro modelos del planeta Tierra. El modelo 4, concordante con el conocimiento científico, no fue observado, pues la mayoría de los participantes se concentra en el modelo 3 en el que coexisten conocimientos previos con algunos elementos científicos. En los niños no mapuches se aprecia que el modelo del planeta Tierra se ajusta a los significados científicos a medida que aumenta el conocimiento escolar. Por el contrario, en los niños mapuches no se observa esta tendencia. Se discute el papel de la cultura y la enseñanza en el aprendizaje del modelo científico del planeta. ABSTRACT The aim of this study was to identify planet Earth models in mapuches and non mapuches students of rural origin. The participants were 40 students divided into two age groups who responded to a cognitive task which explores the representation of the shape of the planet Earth. Based on the degree of agreement with the scientific representation, each participant was categorized into one of four models of planet Earth. Model 4, consistent with the scientific knowledge was not observed because the majority of the participants were concentrated in Model 3. In non mapuche children, it is observed that the model of the planet Earth is adjusted to the scientific meaning in accordance with the increase of school knowledge. On the other hand, this trend is not observed in mapuche children. The role of culture and teaching is discussed in the learning of planet scientific model.

Simulated JWST/NIRISS Spectroscopy of Anticipated TESS Planets and Selected Super-Earths Discovered from K2 and Ground-Based Surveys

Science.gov (United States)

Louie, Dana; Albert, Loic; Deming, Drake

2017-01-01

The 2018 launch of James Webb Space Telescope (JWST), coupled with the 2017 launch of the Transiting Exoplanet Survey Satellite (TESS), heralds a new era in Exoplanet Science, with TESS projected to detect over one thousand transiting sub-Neptune-sized planets (Ricker et al, 2014), and JWST offering unprecedented spectroscopic capabilities. Sullivan et al (2015) used Monte Carlo simulations to predict the properties of the planets that TESS is likely to detect, and published a catalog of 962 simulated TESS planets. Prior to TESS launch, the re-scoped Kepler K2 mission and ground-based surveys such as MEarth continue to seek nearby Earth-like exoplanets orbiting M-dwarf host stars. The exoplanet community will undoubtedly employ JWST for atmospheric characterization follow-up studies of promising exoplanets, but the targeted planets for these studies must be chosen wisely to maximize JWST science return. The goal of this project is to estimate the capabilities of JWST’s Near InfraRed Imager and Slitless Spectrograph (NIRISS)—operating with the GR700XD grism in Single Object Slitless Spectrography (SOSS) mode—during observations of exoplanets transiting their host stars. We compare results obtained for the simulated TESS planets, confirmed K2-discovered super-Earths, and exoplanets discovered using ground-based surveys. By determining the target planet characteristics that result in the most favorable JWST observing conditions, we can optimize the choice of target planets in future JWST follow-on atmospheric characterization studies.

A TIDALLY DESTRUCTED MASSIVE PLANET AS THE PROGENITOR OF THE TWO LIGHT PLANETS AROUND THE sdB STAR KIC 05807616

International Nuclear Information System (INIS)

Bear, Ealeal; Soker, Noam

2012-01-01

We propose that the two newly detected Earth-size planets around the hot B subdwarf star KIC 05807616 are remnant of the tidally destructed metallic core of a massive planet. A single massive gas-giant planet was spiralling-in inside the envelope of the red giant branch star progenitor of the extreme horizontal branch (EHB) star KIC 05807616. The released gravitational energy unbound most of the stellar envelope, turning it into an EHB star. The massive planet reached the tidal-destruction radius of ∼1 R ☉ from the core, where the planet's gaseous envelope was tidally removed. In our scenario, the metallic core of the massive planet was tidally destructed into several Earth-like bodies immediately after the gaseous envelope of the planet was removed. Two, and possibly more, Earth-size fragments survived at orbital separations of ∼> 1 R ☉ within the gaseous disk. The bodies interact with the disk and among themselves, and migrated to reach orbits close to a 3:2 resonance. These observed planets can have a planetary magnetic field about 10 times as strong as that of Earth. This strong magnetic field can substantially reduce the evaporation rate from the planets and explain their survivability against the strong UV radiation of the EHB star.

Climate of Earth-Like Planets With and Without Ocean Heat Transport Orbiting a Range of M and K Stars

Science.gov (United States)

Kiang, N. Y.; Jablonski, Emma R.; Way, Michael J.; Del Genio, Anthony; Roberge, Aki

2015-01-01

The mean surface temperature of a planet is now acknowledged as insufficient to surmise its full potential habitability. Advancing our understanding requires exploration with 3D general circulation models (GCMs), which can take into account how gradients and fluxes across a planet's surface influence the distribution of heat, clouds, and the potential for heterogeneous distribution of liquid water. Here we present 3D GCM simulations of the effects of alternative stellar spectra, instellation, model resolution, and ocean heat transport, on the simulated distribution of heat and moisture of an Earth-like planet (ELP).

THE HABITABLE ZONE OF EARTH-LIKE PLANETS WITH DIFFERENT LEVELS OF ATMOSPHERIC PRESSURE

Energy Technology Data Exchange (ETDEWEB)

Vladilo, Giovanni; Murante, Giuseppe; Silva, Laura [INAF-Trieste Astronomical Observatory, Trieste (Italy); Provenzale, Antonello [Institute of Atmospheric Sciences and Climate-CNR, Torino (Italy); Ferri, Gaia; Ragazzini, Gregorio, E-mail: vladilo@oats.inaf.it [Department of Physics, University of Trieste, Trieste (Italy)

2013-04-10

As a contribution to the study of the habitability of extrasolar planets, we implemented a one-dimensional energy balance model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities. Here we apply our EBM to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure. The habitability, defined as the mean fraction of the planet's surface on which liquid water could exist, is estimated from the pressure-dependent liquid water temperature range, taking into account seasonal and latitudinal variations of surface temperature. By running several thousands of EBM simulations we generated a map of the habitable zone (HZ) in the plane of the orbital semi-major axis, a, and surface pressure, p, for planets in circular orbits around a Sun-like star. As pressure increases, the HZ becomes broader, with an increase of 0.25 AU in its radial extent from p = 1/3 to 3 bar. At low pressure, the habitability is low and varies with a; at high pressure, the habitability is high and relatively constant inside the HZ. We interpret these results in terms of the pressure dependence of the greenhouse effect, the efficiency of horizontal heat transport, and the extent of the liquid water temperature range. Within the limits discussed in the paper, the results can be extended to planets in eccentric orbits around non-solar-type stars. The main characteristics of the pressure-dependent HZ are modestly affected by variations of planetary properties, particularly at high pressure.

THE HABITABLE ZONE OF EARTH-LIKE PLANETS WITH DIFFERENT LEVELS OF ATMOSPHERIC PRESSURE

International Nuclear Information System (INIS)

Vladilo, Giovanni; Murante, Giuseppe; Silva, Laura; Provenzale, Antonello; Ferri, Gaia; Ragazzini, Gregorio

2013-01-01

As a contribution to the study of the habitability of extrasolar planets, we implemented a one-dimensional energy balance model (EBM), the simplest seasonal model of planetary climate, with new prescriptions for most physical quantities. Here we apply our EBM to investigate the surface habitability of planets with an Earth-like atmospheric composition but different levels of surface pressure. The habitability, defined as the mean fraction of the planet's surface on which liquid water could exist, is estimated from the pressure-dependent liquid water temperature range, taking into account seasonal and latitudinal variations of surface temperature. By running several thousands of EBM simulations we generated a map of the habitable zone (HZ) in the plane of the orbital semi-major axis, a, and surface pressure, p, for planets in circular orbits around a Sun-like star. As pressure increases, the HZ becomes broader, with an increase of 0.25 AU in its radial extent from p = 1/3 to 3 bar. At low pressure, the habitability is low and varies with a; at high pressure, the habitability is high and relatively constant inside the HZ. We interpret these results in terms of the pressure dependence of the greenhouse effect, the efficiency of horizontal heat transport, and the extent of the liquid water temperature range. Within the limits discussed in the paper, the results can be extended to planets in eccentric orbits around non-solar-type stars. The main characteristics of the pressure-dependent HZ are modestly affected by variations of planetary properties, particularly at high pressure.

Histories of terrestrial planets

International Nuclear Information System (INIS)

Benes, K.

1981-01-01

The uneven historical development of terrestrial planets - Mercury, Venus, Earth, Moon and Mars - is probably due to the differences in their size, weight and rotational dynamics in association with the internal planet structure, their distance from the Sun, etc. A systematic study of extraterrestrial planets showed that the time span of internal activity was not the same for all bodies. It is assumed that the initial history of all terrestrial planets was marked with catastrophic events connected with the overall dynamic development of the solar system. In view of the fact that the cores of small terrestrial bodies cooled quicker, their geological development almost stagnated after two or three thousand million years. This is what probably happened to the Mercury and the Moon as well as the Mars. Therefore, traces of previous catastrophic events were preserved on the surface of the planets. On the other hand, the Earth is the most metamorphosed terrestrial planet and compared to the other planets appears to be atypical. Its biosphere is significantly developed as well as the other shell components, its hydrosphere and atmosphere, and its crust is considerably differentiated. (J.P.)

Properties of an Earth-like planet orbiting a Sun-like star: Earth observed by the EPOXI mission.

Science.gov (United States)

Livengood, Timothy A; Deming, L Drake; A'hearn, Michael F; Charbonneau, David; Hewagama, Tilak; Lisse, Carey M; McFadden, Lucy A; Meadows, Victoria S; Robinson, Tyler D; Seager, Sara; Wellnitz, Dennis D

2011-11-01

NASA's EPOXI mission observed the disc-integrated Earth and Moon to test techniques for reconnoitering extrasolar terrestrial planets, using the Deep Impact flyby spacecraft to observe Earth at the beginning and end of Northern Hemisphere spring, 2008, from a range of ∼1/6 to 1/3 AU. These observations furnish high-precision and high-cadence empirical photometry and spectroscopy of Earth, suitable as "ground truth" for numerically simulating realistic observational scenarios for an Earth-like exoplanet with finite signal-to-noise ratio. Earth was observed at near-equatorial sub-spacecraft latitude on 18-19 March, 28-29 May, and 4-5 June (UT), in the range of 372-4540 nm wavelength with low visible resolving power (λ/Δλ=5-13) and moderate IR resolving power (λ/Δλ=215-730). Spectrophotometry in seven filters yields light curves at ∼372-948 nm filter-averaged wavelength, modulated by Earth's rotation with peak-to-peak amplitude of ≤20%. The spatially resolved Sun glint is a minor contributor to disc-integrated reflectance. Spectroscopy at 1100-4540 nm reveals gaseous water and carbon dioxide, with minor features of molecular oxygen, methane, and nitrous oxide. One-day changes in global cloud cover resulted in differences between the light curve beginning and end of ≤5%. The light curve of a lunar transit of Earth on 29 May is color-dependent due to the Moon's red spectrum partially occulting Earth's relatively blue spectrum. The "vegetation red edge" spectral contrast observed between two long-wavelength visible/near-IR bands is ambiguous, not clearly distinguishing between the verdant Earth diluted by cloud cover versus the desolate mineral regolith of the Moon. Spectrophotometry in at least one other comparison band at short wavelength is required to distinguish between Earth-like and Moon-like surfaces in reconnaissance observations. However, measurements at 850 nm alone, the high-reflectance side of the red edge, could be sufficient to

Rocky Planet Formation: Quick and Neat

Science.gov (United States)

Kenyon, Scott J.; Najita, Joan R.; Bromley, Benjamin C.

2016-11-01

We reconsider the commonly held assumption that warm debris disks are tracers of terrestrial planet formation. The high occurrence rate inferred for Earth-mass planets around mature solar-type stars based on exoplanet surveys (˜20%) stands in stark contrast to the low incidence rate (≤2%-3%) of warm dusty debris around solar-type stars during the expected epoch of terrestrial planet assembly (˜10 Myr). If Earth-mass planets at au distances are a common outcome of the planet formation process, this discrepancy suggests that rocky planet formation occurs more quickly and/or is much neater than traditionally believed, leaving behind little in the way of a dust signature. Alternatively, the incidence rate of terrestrial planets has been overestimated, or some previously unrecognized physical mechanism removes warm dust efficiently from the terrestrial planet region. A promising removal mechanism is gas drag in a residual gaseous disk with a surface density ≳10-5 of the minimum-mass solar nebula.

Possible Outcomes of Coplanar High-eccentricity Migration: Hot Jupiters, Close-in Super-Earths, and Counter-orbiting Planets

Energy Technology Data Exchange (ETDEWEB)

Xue, Yuxin; Masuda, Kento; Suto, Yasushi, E-mail: yuxin@utap.phys.s.u-tokyo.ac.jp [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan)

2017-02-01

We investigate the formation of close-in planets in near-coplanar eccentric hierarchical triple systems via the secular interaction between an inner planet and an outer perturber (Coplanar High-eccentricity Migration; CHEM). We generalize the previous work on the analytical condition for successful CHEM for point masses interacting only through gravity by taking into account the finite mass effect of the inner planet. We find that efficient CHEM requires that the systems should have m {sub 1}≪m {sub 0} and m {sub 1} ≪ m {sub 2}. In addition to the gravity for point masses, we examine the importance of the short-range forces, and provide an analytical estimate of the migration timescale. We perform a series of numerical simulations in CHEM for systems consisting of a Sun-like central star, giant gas inner planet, and planetary outer perturber, including the short-range forces and stellar and planetary dissipative tides. We find that most of such systems end up with a tidal disruption; a small fraction of the systems produce prograde hot Jupiters (HJs), but no retrograde HJ. In addition, we extend CHEM to super-Earth mass range, and show that the formation of close-in super-Earths in prograde orbits is also possible. Finally, we carry out CHEM simulation for the observed hierarchical triple and counter-orbiting HJ systems. We find that CHEM can explain a part of the former systems, but it is generally very difficult to reproduce counter-orbiting HJ systems.

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

OpenAIRE

Sanromá, E.; Pallé, 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 des...

Earth Stewardship: An initiative by the Ecological Society of America to foster engagement to sustain Planet Earth

Science.gov (United States)

Chapin, F. Stuart; Pickett, S.T.A.; Power, Mary E.; Collins, Scott L.; Baron, Jill S.; Inouye, David W.; Turner, Monica G.

2017-01-01

The Ecological Society of America (ESA) has responded to the growing commitment among ecologists to make their science relevant to society through a series of concerted efforts, including the Sustainable Biosphere Initiative (1991), scientific assessment of ecosystem management (1996), ESA’s vision for the future (2003), Rapid Response Teams that respond to environmental crises (2005), and the Earth Stewardship Initiative (2009). During the past 25 years, ESA launched five new journals, largely reflecting the expansion of scholarship linking ecology with broader societal issues. The goal of the Earth Stewardship Initiative is to raise awareness and to explore ways for ecologists and other scientists to contribute more effectively to the sustainability of our planet. This has occurred through four approaches: (1) articulation of the stewardship concept in ESA publications and Website, (2) selection of meeting themes and symposia, (3) engagement of ESA sections in implementing the initiative, and (4) outreach beyond ecology through collaborations and demonstration projects. Collaborations include societies and groups of Earth and social scientists, practitioners and policy makers, religious and business leaders, federal agencies, and artists and writers. The Earth Stewardship Initiative is a work in progress, so next steps likely include continued nurturing of these emerging collaborations, advancing the development of sustainability and stewardship theory, improving communication of stewardship science, and identifying opportunities for scientists and civil society to take actions that move the Earth toward a more sustainable trajectory.

KEPLER-68: THREE PLANETS, ONE WITH A DENSITY BETWEEN THAT OF EARTH AND ICE GIANTS

Energy Technology Data Exchange (ETDEWEB)

Gilliland, Ronald L. [Department of Astronomy, and Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Marcy, Geoffrey W.; Isaacson, Howard [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rowe, Jason F.; Henze, Christopher E.; Lissauer, Jack J. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Rogers, Leslie [California Institute of Technology, Pasadena, CA 91125 (United States); Torres, Guillermo; Fressin, Francois; Desert, Jean-Michel [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lopez, Eric D. [University of California, Santa Cruz, CA 95064 (United States); Buchhave, Lars A. [Niels Bohr Institute, Copenhagen University (Denmark); Christensen-Dalsgaard, Jorgen; Handberg, Rasmus [Stellar Astrophysics Centre, Department of Physics and Astronomy, DK-8000 Aarhus C (Denmark); Jenkins, Jon M. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States); Chaplin, William J.; Elsworth, Yvonne [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Basu, Sarbani [Department of Astronomy, Yale University, 260 Whitney Ave., New Haven, CT 06511 (United States); Metcalfe, Travis S. [White Dwarf Research Corporation, Boulder, CO 80301 (United States); Hekker, Saskia, E-mail: gillil@stsci.edu [Astronomical Institute Anton Pannekoek, University of Amsterdam, 1098 XH Amsterdam, Science Park 904 (Netherlands); and others

2013-03-20

NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third Jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit, has M{sub P}=8.3{sup +2.2}{sub -2.4} M{sub Circled-Plus }, R{sub P}=2.31{sup +0.06}{sub -0.09} R{sub Circled-Plus }, and {rho}{sub P}=3.32{sup +0.86}{sub -0.98} g cm{sup -3}, giving Kepler-68b a density intermediate between that of the ice giants and Earth. Kepler-68c is Earth-sized, with a radius R{sub P}=0.953{sup +0.037}{sub -0.042} R{sub Circled-Plus} and transits on a 9.6 day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an orbital period of 580 {+-} 15 days and a minimum mass of M{sub P}sin i = 0.947 {+-} 0.035M{sub J} . Power spectra of the Kepler photometry at one minute cadence exhibit a rich and strong set of asteroseismic pulsation modes enabling detailed analysis of the stellar interior. Spectroscopy of the star coupled with asteroseismic modeling of the multiple pulsation modes yield precise measurements of stellar properties, notably T{sub eff} = 5793 {+-} 74 K, M{sub *} = 1.079 {+-} 0.051 M{sub Sun }, R{sub *} = 1.243 {+-} 0.019 R{sub Sun }, and {rho}{sub *} = 0.7903 {+-} 0.0054 g cm{sup -3}, all measured with fractional uncertainties of only a few percent. Models of Kepler-68b suggest that it is likely composed of rock and water, or has a H and He envelope to yield its density {approx}3 g cm{sup -3}.

A Direct Path to Finding Earth-Like Planets

Science.gov (United States)

Heap, Sara R.; Linder, Don J.

2009-01-01

As envisaged by the 2000 astrophysics decadal survey panel: The main goal of Terrestrial Planet Finder (TPF) is nothing less than to search for evidence of life on terrestrial planets around nearby stars . Here, we consider how an optical telescope paired with a free-flying occulter blocking light from the star can reach this goal directly, without knowledge of results from prior astrometric, doppler, or transit exoplanet observations. Using design reference missions and other simulations, we explore the potential of TPF-O to find planets in the habitable zone around their central stars, to spectrally characterize the atmospheres of detected planets, and to obtain rudimentary information about their orbits. We emphasize the importance of ozone absorption in the UV spectrum of a planet as a marker of photosynthesis by plants, algae, and cyanobacteria.

ROTATIONAL VARIABILITY OF EARTH'S POLAR REGIONS: IMPLICATIONS FOR DETECTING SNOWBALL PLANETS

International Nuclear Information System (INIS)

Cowan, Nicolas B.; Robinson, Tyler; Agol, Eric; Meadows, Victoria S.; Shields, Aomawa L.; Livengood, Timothy A.; Deming, Drake; A'Hearn, Michael F.; Wellnitz, Dennis D.; Charbonneau, David; Lisse, Carey M.; Seager, Sara

2011-01-01

We have obtained the first time-resolved, disk-integrated observations of Earth's poles with the Deep Impact spacecraft as part of the EPOXI mission of opportunity. These data mimic what we will see when we point next-generation space telescopes at nearby exoplanets. We use principal component analysis (PCA) and rotational light curve inversion to characterize color inhomogeneities and map their spatial distribution from these unusual vantage points, as a complement to the equatorial views presented by Cowan et al. in 2009. We also perform the same PCA on a suite of simulated rotational multi-band light curves from NASA's Virtual Planetary Laboratory three-dimensional spectral Earth model. This numerical experiment allows us to understand what sorts of surface features PCA can robustly identify. We find that the EPOXI polar observations have similar broadband colors as the equatorial Earth, but with 20%-30% greater apparent albedo. This is because the polar observations are most sensitive to mid-latitudes, which tend to be more cloudy than the equatorial latitudes emphasized by the original EPOXI Earth observations. The cloudiness of the mid-latitudes also manifests itself in the form of increased variability at short wavelengths in the polar observations and as a dominant gray eigencolor in the south polar observation. We construct a simple reflectance model for a snowball Earth. By construction, our model has a higher Bond albedo than the modern Earth; its surface albedo is so high that Rayleigh scattering does not noticeably affect its spectrum. The rotational color variations occur at short wavelengths due to the large contrast between glacier ice and bare land in those wavebands. Thus, we find that both the broadband colors and diurnal color variations of such a planet would be easily distinguishable from the modern-day Earth, regardless of viewing angle.

Habitable Planets for Man

National Research Council Canada - National Science Library

Dole, Stephen H

2007-01-01

..., and discusses how to search for habitable planets. Interestingly for our time, he also gives an appraisal of the earth as a planet and describes how its habitability would be changed if some of its basic properties were altered...

Carbon trading, climate change, environmental sustainability and saving planet Earth

Science.gov (United States)

Yim, W. W.

2009-12-01

Carbon trading namely the reduction of future carbon dioxide levels has been widely touted as a solution needed to counter the problem of climate change. However, there are enormous risks involved as the measure tackles only one of the causes of climate change and may prove to be ineffective. This presentation highlights ten points relevant to the discussion on carbon trading, climate change, environmental sustainability and saving planet Earth for increasing public awareness. They include: (1) Climate has changed throughout Earth’s history. (2) The present level of about 388 parts per million level of carbon dioxide in the atmosphere has already exceeded the maximum level of the past 800,000 years. This value is obtained from air bubbles trapped within the ice in Antarctica but the consequence of further increases remains uncertain. (3) Earth scientists do not have an overwhelming consensus on whether carbon trading alone is an effective measure in mitigating climate change. (4) The present state of the Earth’s demise is largely the result of human actions including population growth and the mismanagement of the Earth. (5) The latest evidence on sea-level changes in the South China Sea a far-field region unaffected by glacial isostatic readjustment is not in support of a ‘rapid’ rate of future sea-level rise through global warming. (6) Volcanic eruptions have an important role in driving the Earth’s climate. Examples of temperature lowering as well as abnormally wet and dry years can both be found in the instrumental record. (7) Humans have drastically modified the ‘natural’ water cycle. This is however not a well recognized cause of climate change compared to the emission of greenhouse gases through fossil fuel consumption. (8) The bulk (~75%) of the rise in mean annual temperature of about 1oC observed at the Hong Kong Observatory Station since record began in 1884 is best explained by the thermal heat island effect. (9) No evidence has been found

The fate of scattered planets

Energy Technology Data Exchange (ETDEWEB)

Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2014-12-01

As gas giant planets evolve, they may scatter other planets far from their original orbits to produce hot Jupiters or rogue planets that are not gravitationally bound to any star. Here, we consider planets cast out to large orbital distances on eccentric, bound orbits through a gaseous disk. With simple numerical models, we show that super-Earths can interact with the gas through dynamical friction to settle in the remote outer regions of a planetary system. Outcomes depend on planet mass, the initial scattered orbit, and the evolution of the time-dependent disk. Efficient orbital damping by dynamical friction requires planets at least as massive as the Earth. More massive, longer-lived disks damp eccentricities more efficiently than less massive, short-lived ones. Transition disks with an expanding inner cavity can circularize orbits at larger distances than disks that experience a global (homologous) decay in surface density. Thus, orbits of remote planets may reveal the evolutionary history of their primordial gas disks. A remote planet with an orbital distance ∼100 AU from the Sun is plausible and might explain correlations in the orbital parameters of several distant trans-Neptunian objects.

CANDIDATE PLANETS IN THE HABITABLE ZONES OF KEPLER STARS

International Nuclear Information System (INIS)

Gaidos, Eric

2013-01-01

A key goal of the Kepler mission is the discovery of Earth-size transiting planets in ''habitable zones'' where stellar irradiance maintains a temperate climate on an Earth-like planet. Robust estimates of planet radius and irradiance require accurate stellar parameters, but most Kepler systems are faint, making spectroscopy difficult and prioritization of targets desirable. The parameters of 2035 host stars were estimated by Bayesian analysis and the probabilities p HZ that 2738 candidate or confirmed planets orbit in the habitable zone were calculated. Dartmouth Stellar Evolution Program models were compared to photometry from the Kepler Input Catalog, priors for stellar mass, age, metallicity and distance, and planet transit duration. The analysis yielded probability density functions for calculating confidence intervals of planet radius and stellar irradiance, as well as p HZ . Sixty-two planets have p HZ > 0.5 and a most probable stellar irradiance within habitable zone limits. Fourteen of these have radii less than twice the Earth; the objects most resembling Earth in terms of radius and irradiance are KOIs 2626.01 and 3010.01, which orbit late K/M-type dwarf stars. The fraction of Kepler dwarf stars with Earth-size planets in the habitable zone (η ⊕ ) is 0.46, with a 95% confidence interval of 0.31-0.64. Parallaxes from the Gaia mission will reduce uncertainties by more than a factor of five and permit definitive assignments of transiting planets to the habitable zones of Kepler stars.

CoRoT’s first seven planets: An overview*

Directory of Open Access Journals (Sweden)

Barge P.

2011-07-01

Full Text Available The up to 150 day uninterrupted high-precision photometry of about 100000 stars – provided so far by the exoplanet channel of the CoRoT space telescope – gave a new perspective on the planet population of our galactic neighbourhood. The seven planets with very accurate parameters widen the range of known planet properties in almost any respect. Giant planets have been detected at low metallicity, rapidly rotating and active, spotted stars. CoRoT-3 populated the brown dwarf desert and closed the gap of measured physical properties between standard giant planets and very low mass stars. CoRoT extended the known range of planet masses down-to 5 Earth masses and up to 21 Jupiter masses, the radii to less than 2 Earth radii and up to the most inflated hot Jupiter found so far, and the periods of planets discovered by transits to 9 days. Two CoRoT planets have host stars with the lowest content of heavy elements known to show a transit hinting towards a different planet-host-star-metallicity relation then the one found by radial-velocity search programs. Finally the properties of the CoRoT-7b prove that terrestrial planets with a density close to Earth exist outside the Solar System. The detection of the secondary transit of CoRoT-1 at the 10−5-level and the very clear detection of the 1.7 Earth radii of CoRoT-7b at 3.5 10−4 relative flux are promising evidence of CoRoT being able to detect even smaller, Earth sized planets.

Limits On Undetected Planets in the Six Transiting Planets Kepler-11 System

Science.gov (United States)

Lissauer, Jack

2017-01-01

The Kepler-11 has five inner planets ranging from approx. 2 - 1 times as massive Earth in a tightly-packed configuration, with orbital periods between 10 and 47 days. A sixth planet, Kepler-11 g, with a period of118 days, is also observed. The spacing between planets Kepler-11 f and Kepler-11 g is wide enough to allow room for a planet to orbit stably between them. We compare six and seven planet fits to measured transit timing variations (TTVs) of the six known planets. We find that in most cases an additional planet between Kepler-11 f and Kepler-11 g degrades rather than enhances the fit to the TTV data, and where the fit is improved, the improvement provides no significant evidence of a planet between Kepler-11 f and Kepler-11 g. This implies that any planet in this region must be low in mass. We also provide constraints on undiscovered planets orbiting exterior to Kepler-11 g. representations will be described.

Kepler planet-detection mission

DEFF Research Database (Denmark)

Borucki...[], William J.; Koch, David; Buchhave, Lars C. Astrup

2010-01-01

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet’s surface. During the first 6 weeks of observations, Kepler...... is one of the lowest-density planets (~0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets....

A comprehensive mission to planet Earth: Woods Hole Space Science and Applications Advisory Committee Planning Workshop

Science.gov (United States)

1991-01-01

The NASA program Mission to Planet Earth (MTPE) is described in this set of visuals presented in Massachusetts on July 29, 1991. The problem presented in this document is that the earth system is changing and that human activity accelerates the rate of change resulting in increased greenhouse gases, decreasing levels of stratospheric ozone, acid rain, deforestation, decreasing biodiversity, and overpopulation. Various national and international organizations are coordinating global change research. The complementary space observations for this activity are sun-synchronous polar orbits, low-inclination, low altitude orbits, geostationary orbits, and ground measurements. The Geostationary Earth Observatory is the major proposed mission of MTPE. Other proposed missions are EOS Synthetic Aperture Radar, ARISTOTELES Magnetic Field Experiment, and the Global Topography Mission. Use of the NASA DC-8 aircraft is outlined as carrying out the Airborne Science and Applications Program. Approved Earth Probes Program include the Total Ozone Mapping Spectrometer (TOMS). Other packages for earth observation are described.

Geophysical and atmospheric evolution of habitable planets.

Science.gov (United States)

Lammer, Helmut; Selsis, Frank; Chassefière, Eric; Breuer, Doris; Griessmeier, Jean-Mathias; Kulikov, Yuri N; Erkaev, Nikolai V; Khodachenko, Maxim L; Biernat, Helfried K; Leblanc, Francois; Kallio, Esa; Lundin, Richard; Westall, Frances; Bauer, Siegfried J; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Gröller, Hannes; Hanslmeier, Arnold; Hausleitner, Walter; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Léger, Alain; Leitzinger, Martin; Lichtenegger, Herbert I M; Liseau, René; Lunine, Jonathan; Motschmann, Uwe; Odert, Petra; Paresce, Francesco; Parnell, John; Penny, Alan; Quirrenbach, Andreas; Rauer, Heike; Röttgering, Huub; Schneider, Jean; Spohn, Tilman; Stadelmann, Anja; Stangl, Günter; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

2010-01-01

The evolution of Earth-like habitable planets is a complex process that depends on the geodynamical and geophysical environments. In particular, it is necessary that plate tectonics remain active over billions of years. These geophysically active environments are strongly coupled to a planet's host star parameters, such as mass, luminosity and activity, orbit location of the habitable zone, and the planet's initial water inventory. Depending on the host star's radiation and particle flux evolution, the composition in the thermosphere, and the availability of an active magnetic dynamo, the atmospheres of Earth-like planets within their habitable zones are differently affected due to thermal and nonthermal escape processes. For some planets, strong atmospheric escape could even effect the stability of the atmosphere.

Taxonomy of the extrasolar planet.

Science.gov (United States)

Plávalová, Eva

2012-04-01

When a star is described as a spectral class G2V, we know that the star is similar to our Sun. We know its approximate mass, temperature, age, and size. When working with an extrasolar planet database, it is very useful to have a taxonomy scale (classification) such as, for example, the Harvard classification for stars. The taxonomy has to be easily interpreted and present the most relevant information about extrasolar planets. I propose an extrasolar planet taxonomy scale with four parameters. The first parameter concerns the mass of an extrasolar planet in the form of units of the mass of other known planets, where M represents the mass of Mercury, E that of Earth, N Neptune, and J Jupiter. The second parameter is the planet's distance from its parent star (semimajor axis) described in a logarithm with base 10. The third parameter is the mean Dyson temperature of the extrasolar planet, for which I established four main temperature classes: F represents the Freezing class, W the Water class, G the Gaseous class, and R the Roasters class. I devised one additional class, however: P, the Pulsar class, which concerns extrasolar planets orbiting pulsar stars. The fourth parameter is eccentricity. If the attributes of the surface of the extrasolar planet are known, we are able to establish this additional parameter where t represents a terrestrial planet, g a gaseous planet, and i an ice planet. According to this taxonomy scale, for example, Earth is 1E0W0t, Neptune is 1N1.5F0i, and extrasolar planet 55 Cnc e is 9E-1.8R1.

More Planets in the Hyades Cluster

Science.gov (United States)

Kohler, Susanna

2017-12-01

through the K2 light curves of young stars as part of the ZEIT (Zodiacal Exoplanets in Time) Survey. Using these data, they identified the presence of three planets in the EPIC 247589423 system:a roughly Earth-sized planet ( 1.0 Earth radii) with a period of 8.0 days,the mini-Neptune identified in the other study, with a size of 2.9 Earth radii and period of 17 days, anda super-Earth, with a size of 1.5 Earth radii and period of 26 days.Light curve of EPIC 247589423 from K2, with the lower panels showing the transits of the three discovered planets. [Mann et al. 2018]The smallest planet is among the youngest Earth-sized planets ever discovered, allowing us a rare glimpse into the history and evolution of planets similar to our own.But these planetary discoveries are additionally exciting because theyre orbiting a bright star thats relatively quiet for its age making the system an excellent target for dedicated radial-velocity observations to determine the planet masses.Since most young star clusters are much further away, they lie out of range of radial-velocity follow-up, rendering EPIC 247589423 a unique opportunity to explore the properties of young planets in detail. With more discoveries like these from Keplers data, we can hope to soon learn more about planets in all their stages of evolution.CitationAndrew W. Mann et al 2018 AJ 155 4. doi:10.3847/1538-3881/aa9791

Factors Affecting the Habitability of Earth-like Planets

Science.gov (United States)

Meadows, Victoria; NAI-Virtual Planetary Laboratory Team

2014-03-01

Habitability is a measure of an environment's potential to support life. For exoplanets, the concept of habitability can be used broadly - to inform our calculations of the possibility and distribution of life elsewhere - or as a practical tool to inform mission designs and to prioritize specific targets in the search for extrasolar life. Although a planet's habitability does depend critically on the effect of stellar type and planetary semi-major axis on climate balance, work in the interdisciplinary field of astrobiology has identified many additional factors that can affect a planet's environment and its potential ability to support life. Life requires material for metabolism and structures, a liquid medium for chemical transport, and an energy source to drive metabolism and other life processes. Whether a planet's surface or sub-surface can provide these requirements is the result of numerous planetary and astrophysical processes that affect the planet's formation and evolution. Many of these factors are interdependent, and fall into three main categories: stellar effects, planetary effects and planetary system effects. Key abiotic processes affecting the resultant planetary environment include photochemistry (e.g. Segura et al., 2003; 2005), stellar effects on climate balance (e.g. Joshii et al., 2012; Shields et al., 2013), atmospheric loss (e.g. Lopez and Fortney, 2013), and gravitational interactions with the star (e.g. Barnes et al., 2013). In many cases, the effect of these processes is strongly dependent on a specific planet's existing environmental properties. Examples include the resultant UV flux at a planetary surface as a product of stellar activity and the strength of a planet's atmospheric UV shield (Segura et al., 2010); and the amount of tidal energy available to a planet to drive plate tectonics and heat the surface (Barnes et al., 2009), which is in turn due to a combination of stellar mass, planetary mass and composition, planetary orbital

Extrusive and Intrusive Magmatism Greatly Influence the Tectonic Mode of Earth-Like Planets

Science.gov (United States)

Lourenco, D.; Tackley, P. J.; Rozel, A.; Ballmer, M.

2017-09-01

Plate tectonics on Earth-like planets is typically modelling using a strongly temperature-dependent visco-plastic rheology. Previous analyses have generally focussed on purely thermal convection. However, we have shown that the influence of compositional heterogeneity in the form of continental or oceanic crust can greatly influence plate tectonics by making it easier (i.e. it occurs at a lower yield stress or friction coefficient). Here we present detailed results on this topic, in particular focussing on the influence of intrusive vs. extrusive magmatism on the tectonic mode.

TERRESTRIAL PLANET FORMATION DURING THE MIGRATION AND RESONANCE CROSSINGS OF THE GIANT PLANETS

International Nuclear Information System (INIS)

Lykawka, Patryk Sofia; Ito, Takashi

2013-01-01

The newly formed giant planets may have migrated and crossed a number of mutual mean motion resonances (MMRs) when smaller objects (embryos) were accreting to form the terrestrial planets in the planetesimal disk. We investigated the effects of the planetesimal-driven migration of Jupiter and Saturn, and the influence of their mutual 1:2 MMR crossing on terrestrial planet formation for the first time, by performing N-body simulations. These simulations considered distinct timescales of MMR crossing and planet migration. In total, 68 high-resolution simulation runs using 2000 disk planetesimals were performed, which was a significant improvement on previously published results. Even when the effects of the 1:2 MMR crossing and planet migration were included in the system, Venus and Earth analogs (considering both orbits and masses) successfully formed in several runs. In addition, we found that the orbits of planetesimals beyond a ∼ 1.5-2 AU were dynamically depleted by the strengthened sweeping secular resonances associated with Jupiter's and Saturn's more eccentric orbits (relative to the present day) during planet migration. However, this depletion did not prevent the formation of massive Mars analogs (planets with more than 1.5 times Mars's mass). Although late MMR crossings (at t > 30 Myr) could remove such planets, Mars-like small mass planets survived on overly excited orbits (high e and/or i), or were completely lost in these systems. We conclude that the orbital migration and crossing of the mutual 1:2 MMR of Jupiter and Saturn are unlikely to provide suitable orbital conditions for the formation of solar system terrestrial planets. This suggests that to explain Mars's small mass and the absence of other planets between Mars and Jupiter, the outer asteroid belt must have suffered a severe depletion due to interactions with Jupiter/Saturn, or by an alternative mechanism (e.g., rogue super-Earths)

The "Planet Earth Week": a National Scientific Festival helping Italy Discover Geosciences.

Science.gov (United States)

Seno, S.; Coccioni, R.

2017-12-01

The "Planet Earth Week- Italy Discovering Geosciences: a More Informed Society is a More Engaged Society" (www.settimanaterra.org) is a science festival that involves the whole of the Italian Regions: founded in 2012, it has become the largest event of Italian Geosciences and one of the biggest European science festivals. During a week in October several locations distributed throughout the Country (see map) are animated by events, called "Geoeventi", to disseminate geosciences to the masses and deliver science education by means of a wide range of activities: hiking, walking in city and town centers, open-door at museums and research centers, guided tours, exhibitions, educational and experimental workshops for children and young people, music and art performances, food and wine events, lectures, conferences, round tables. Universities and colleges, research centers, local Authorities, cultural and scientific associations, parks and museums, professionals organize the Geoeventi. The festival aims at bringing adults and young people to Geosciences, conveying enthusiasm for scientific research and discoveries, promoting sustainable cultural tourism, aware of environmental values and distributed all over Italy. The Geoeventi shed light both on the most spectacular and on the less known geological sites, which are often a stone's throw from home. The Planet Earth Week is growing year after year: the 2016 edition proposed 310 Geoeventi, 70 more than in 2015. The number of places involved in the project also increased and rose from 180 in 2015 to 230 in 2016. This initiative, that is also becoming a significant economic driver for many small companies active in the field of science divulgation, is analyzed, evaluated and put in a transnational network perspective.

An extrasolar planetary system with three Neptune-mass planets.

Science.gov (United States)

Lovis, Christophe; Mayor, Michel; Pepe, Francesco; Alibert, Yann; Benz, Willy; Bouchy, François; Correia, Alexandre C M; Laskar, Jacques; Mordasini, Christoph; Queloz, Didier; Santos, Nuno C; Udry, Stéphane; Bertaux, Jean-Loup; Sivan, Jean-Pierre

2006-05-18

Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called 'hot Neptunes' or 'super-Earths' around Sun-like stars. These planets have masses 5-20 times larger than the Earth and are mainly found on close-in orbits with periods of 2-15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun-Earth distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star.

KOI-3158: The oldest known system of terrestrial-size planets

Directory of Open Access Journals (Sweden)

Campante T. L.

2015-01-01

Full Text Available The first discoveries of exoplanets around Sun-like stars have fueled efforts to find ever smaller worlds evocative of Earth and other terrestrial planets in the Solar System. While gas-giant planets appear to form preferentially around metal-rich stars, small planets (with radii less than four Earth radii can form under a wide range of metallicities. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universe’s history when metals were far less abundant. We report Kepler spacecraft observations of KOI-3158, a metal-poor Sun-like star from the old population of the Galactic thick disk, which hosts five planets with sizes between Mercury and Venus. We used asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that KOI-3158 formed when the Universe was less than 20 % of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the Universe’s 13.8-billion-year history, providing scope for the existence of ancient life in the Galaxy.

The effect of a strong stellar flare on the atmospheric chemistry of an earth-like planet orbiting an M dwarf.

Science.gov (United States)

Segura, Antígona; Walkowicz, Lucianne M; Meadows, Victoria; Kasting, James; Hawley, Suzanne

2010-09-01

Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9 × 10⁸ protons cm⁻² sr⁻¹ s⁻¹ for particles with energies >10 MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100 s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity.

A rocky composition for an Earth-sized exoplanet.

Science.gov (United States)

Howard, Andrew W; Sanchis-Ojeda, Roberto; Marcy, Geoffrey W; Johnson, John Asher; Winn, Joshua N; Isaacson, Howard; Fischer, Debra A; Fulton, Benjamin J; Sinukoff, Evan; Fortney, Jonathan J

2013-11-21

Planets with sizes between that of Earth (with radius R Earth symbol) and Neptune (about 4R Earth symbol) are now known to be common around Sun-like stars. Most such planets have been discovered through the transit technique, by which the planet's size can be determined from the fraction of starlight blocked by the planet as it passes in front of its star. Measuring the planet's mass--and hence its density, which is a clue to its composition--is more difficult. Planets of size 2-4R Earth symbol have proved to have a wide range of densities, implying a diversity of compositions, but these measurements did not extend to planets as small as Earth. Here we report Doppler spectroscopic measurements of the mass of the Earth-sized planet Kepler-78b, which orbits its host star every 8.5 hours (ref. 6). Given a radius of 1.20 ± 0.09 R Earth symbol and a mass of 1.69 ± 0.41 R Earth symbol, the planet's mean density of 5.3 ± 1.8 g cm(-3) is similar to Earth's, suggesting a composition of rock and iron.

Observing the Spectra of MEarth and TRAPPIST Planets with JWST

Science.gov (United States)

Morley, Caroline; Kreidberg, Laura; Rustamkulov, Zafar; Robinson, Tyler D.; Fortney, Jonathan J.

2017-10-01

During the past two years, nine planets close to Earth in radius have been discovered around nearby M dwarfs cooler than 3300 K. These planets include the 7 planets in the TRAPPIST-1 system and two planets discovered by the MEarth survey, GJ 1132b and LHS 1140b (Dittmann et al. 2017; Berta-Thompson et al. 2015; Gillon et al. 2017). These planets are the smallest planets discovered to date that will be amenable to atmospheric characterization with JWST. They span equilibrium temperatures from ˜130 K to >500 K, and radii from 0.7 to 1.43 Earth radii. Some of these planets orbit as distances potentially amenable to surface liquid water, though the actual surface temperatures will depend strongly on the albedo of the planet and the thickness and composition of its atmosphere. The stars they orbit also vary in activity levels, from the quiet LHS 1140b host star to the more active TRAPPIST-1 host star. This set of planets will form the testbed for our first chance to study the diversity of atmospheres around Earth-sized planets. Here, we will present model spectra of these 9 planets, varying the composition and the surface pressure of the atmosphere. We base our elemental compositions on three outcomes of planetary atmosphere evolution in our own solar system: Earth, Titan, and Venus. We calculate the molecular compositions in chemical equilibrium. We present both thermal emission spectra and transmission spectra for each of these objects, and make predictions for the observability of these spectra with different instrument modes with JWST.

How, when and where Life will begin on another planet after Earth by Duky’s Theory

Science.gov (United States)

Deol, Satveer; Singh Nafria, Amritpal

2017-01-01

Our Sun is a Red Giant Star and in distant future it will engulf Mercury, Venus and probably Earth and Mars. This paper shows that in distant future due to increasing size & luminosity of the Sun life will begin on one of the planet after 1 duky’s Unit. 1 duky's Unit is the time from now to the time when Mercury would get merged in Sun. At that time Venus would be first planet & due to closeness to Sun, its upper atmosphere would get heated up by solar wind. In a continuous process the clouds of sulfuric acid would escape its gravity. Eventually it would get drifted off into space and it become Mercury twin. On Earth after few million years moisture in air would become very good to trap infra red radiation. As it will warms up, oceans would evaporate even more & in few million years it would get covered with blanket of water vapours. Due to increasing temperature & pressure, volcanoes on Earth would become active then volcanic eruption would blast billions of tons of sulfur high into atmosphere there sulfur would mix with water vapors & form conc. Sulfuric acids. In a continuous process of few more million years whole Earth would get covered with sulphuric acids cloud. As Earth’s moon is receding away from Earth, so before 1 DU, Moon will have been gone away from Earth. As a result it would get started slow down one spin about 1 million year. These would lead to massive outpouring of CO2 & other greenhouse gasses. At that Earth would become Venus Twin. Now it's Mars turn, according to scientists after 50 millions years from now phobo will crash onto the surface of Mars. When that would happen, Mars would have one moon like Earth. This collision would be so hard & strong that phobo would get totally immersed in the surface of Mars as a results it's possible that Mars would get tilted at about 23.5 degree. Due to collision molten lava would come out. When temperature & pressure would rise then water ice would become water. When water would get enriched with

Planet hunters. VI. An independent characterization of KOI-351 and several long period planet candidates from the Kepler archival data

International Nuclear Information System (INIS)

Schmitt, Joseph R.; Wang, Ji; Fischer, Debra A.; Moriarty, John C.; Boyajian, Tabetha S.; Jek, Kian J.; LaCourse, Daryll; Omohundro, Mark R.; Winarski, Troy; Goodman, Samuel Jon; Jebson, Tony; Schwengeler, Hans Martin; Paterson, David A.; Schwamb, Megan E.; Lintott, Chris; Simpson, Robert; Lynn, Stuart; Smith, Arfon M.; Parrish, Michael; Schawinski, Kevin

2014-01-01

We report the discovery of 14 new transiting planet candidates in the Kepler field from the Planet Hunters citizen science program. None of these candidates overlapped with Kepler Objects of Interest (KOIs) at the time of submission. We report the discovery of one more addition to the six planet candidate system around KOI-351, making it the only seven planet candidate system from Kepler. Additionally, KOI-351 bears some resemblance to our own solar system, with the inner five planets ranging from Earth to mini-Neptune radii and the outer planets being gas giants; however, this system is very compact, with all seven planet candidates orbiting ≲ 1 AU from their host star. A Hill stability test and an orbital integration of the system shows that the system is stable. Furthermore, we significantly add to the population of long period transiting planets; periods range from 124 to 904 days, eight of them more than one Earth year long. Seven of these 14 candidates reside in their host star's habitable zone.

Scenarios of giant planet formation and evolution and their impact on the formation of habitable terrestrial planets.

Science.gov (United States)

Morbidelli, Alessandro

2014-04-28

In our Solar System, there is a clear divide between the terrestrial and giant planets. These two categories of planets formed and evolved separately, almost in isolation from each other. This was possible because Jupiter avoided migrating into the inner Solar System, most probably due to the presence of Saturn, and never acquired a large-eccentricity orbit, even during the phase of orbital instability that the giant planets most likely experienced. Thus, the Earth formed on a time scale of several tens of millions of years, by collision of Moon- to Mars-mass planetary embryos, in a gas-free and volatile-depleted environment. We do not expect, however, that this clear cleavage between the giant and terrestrial planets is generic. In many extrasolar planetary systems discovered to date, the giant planets migrated into the vicinity of the parent star and/or acquired eccentric orbits. In this way, the evolution and destiny of the giant and terrestrial planets become intimately linked. This paper discusses several evolutionary patterns for the giant planets, with an emphasis on the consequences for the formation and survival of habitable terrestrial planets. The conclusion is that we should not expect Earth-like planets to be typical in terms of physical and orbital properties and accretion history. Most habitable worlds are probably different, exotic worlds.

THE COMPOSITIONAL DIVERSITY OF EXTRASOLAR TERRESTRIAL PLANETS. II. MIGRATION SIMULATIONS

International Nuclear Information System (INIS)

Carter-Bond, Jade C.; O'Brien, David P.; Raymond, Sean N.

2012-01-01

Prior work has found that a variety of terrestrial planetary compositions are expected to occur within known extrasolar planetary systems. However, such studies ignored the effects of giant planet migration, which is thought to be very common in extrasolar systems. Here we present calculations of the compositions of terrestrial planets that formed in dynamical simulations incorporating varying degrees of giant planet migration. We used chemical equilibrium models of the solid material present in the disks of five known planetary host stars: the Sun, GJ 777, HD4203, HD19994, and HD213240. Giant planet migration has a strong effect on the compositions of simulated terrestrial planets as the migration results in large-scale mixing between terrestrial planet building blocks that condensed at a range of temperatures. This mixing acts to (1) increase the typical abundance of Mg-rich silicates in the terrestrial planets' feeding zones and thus increase the frequency of planets with Earth-like compositions compared with simulations with static giant planet orbits, and (2) drastically increase the efficiency of the delivery of hydrous phases (water and serpentine) to terrestrial planets and thus produce waterworlds and/or wet Earths. Our results demonstrate that although a wide variety of terrestrial planet compositions can still be produced, planets with Earth-like compositions should be common within extrasolar planetary systems.

Extrasolar planets : - From gaseous giant planets to rocky planets. - Steps towards the detection of life biomarkers.

CERN Multimedia

CERN. Geneva

2017-01-01

Today, great efforts are made to detect Earth-mass rocky planets in the so-called habitable zone of their host stars. What are the difficulties, the instrumental projects  and the already detected interesting systems ?

Check-Up of Planet Earth at the Turn of the Millennium: Contribution of EOS-Terra to a New Phase in Earth Sciences

Science.gov (United States)

Kaufman, Yoram

1999-01-01

Langley's remarkable solar and lunar spectra collected from Mt. Whitney inspired Arrhenius to develop the first quantitative climate model in 1896. In 1999, NASA's Earth Observing AM Satellite (EOS-Terra) will repeat Langley's experiment, but for the entire planet, thus pioneering a wide array of calibrated spectral observations from space of the Earth System. Conceived in response to real environmental problems, EOS-Terra, in conjunction with other international satellite efforts, will fill a major gap in current efforts by providing quantitative global data sets with a resolution of few kilometers on the physical, chemical and biological elements of the earth system. Thus, like Langley's data, EOS-Terra can revolutionize climate research by inspiring a new generation of climate system models and enable us to assess the human impact on the environment. In the talk I shall review the historical developments that brought to the Terra mission, its objectives and example of application to biomass burning.

Constitution of terrestrial planets

International Nuclear Information System (INIS)

Waenke, H.

1981-01-01

Reliable estimates of the bulk composition are restricted to the Earth, the Moon and the eucrite parent asteroid. The last, the parent body of the eucrite-diogenite family of meteorites, seems to have an almost chondritic composition except for a considerable depletion of all moderately volatile (Na, K, Rb, F, etc.) and highly volatile (Cl, Br, Cd, Pb, etc.) elements. The moon is also depleted in moderate volatile and volatile elements compared to carbonaceous chondrites of type 1 (C1) and to the Earth. Again normalized to C1 and Si the Earth's mantle and the Moon are slightly enriched in refractory lithophile elements and in magnesium. The striking depletion of the Earth's mantle for the elements V, Cr and Mn can be explained by their partial removal into the core. Apart from their contents of metallic iron, all siderophile elements, moderately volatile and volatile elements, Earth and Moon are chemically very similar. It might well be that, with these exceptions and that of a varying degree of oxidation, all the inner planets have a similar chemistry. The chemical composition of the Earth's mantle, yields important information about the accretion history of the Earth and that of the inner planets. (author)

Climate evolution on the terrestrial planets

International Nuclear Information System (INIS)

Kasting, J.F.; Toon, O.B.

1989-01-01

The present comparative evaluation of the long-term evolution of the Venus, earth, and Mars climates suggests that the earth's climate has remained temperate over most of its history despite a secular solar luminosity increase in virtue of a negative-feedback cycle based on atmospheric CO 2 levels and climate. The examination of planetary climate histories suggests that an earth-sized planet should be able to maintain liquid water on its surface at orbital distances in the 0.9-1.5 AU range, comparable to the orbit of Mars; this, in turn, implies that there may be many other habitable planets within the Galaxy

Direct Imaging of Warm Extrasolar Planets

International Nuclear Information System (INIS)

Macintosh, B

2005-01-01

One of the most exciting scientific discoveries in the last decade of the twentieth century was the first detection of planets orbiting a star other than our own. By now more than 130 extrasolar planets have been discovered indirectly, by observing the gravitational effects of the planet on the radial velocity of its parent star. This technique has fundamental limitations: it is most sensitive to planets close to their star, and it determines only a planet's orbital period and a lower limit on the planet's mass. As a result, all the planetary systems found so far are very different from our own--they have giant Jupiter-sized planets orbiting close to their star, where the terrestrial planets are found in our solar system. Such systems have overturned the conventional paradigm of planet formation, but have no room in them for habitable Earth-like planets. A powerful complement to radial velocity detections of extrasolar planets will be direct imaging--seeing photons from the planet itself. Such a detection would allow photometric measurements to determine the temperature and radius of a planet. Also, direct detection is most sensitive to planets in wide orbits, and hence more capable of seeing solar systems resembling our own, since a giant planet in a wide orbit does not preclude the presence of an Earth-like planet closer to the star. Direct detection, however, is extremely challenging. Jupiter is roughly a billion times fainter than our sun. Two techniques allowed us to overcome this formidable contrast and attempt to see giant planets directly. The first is adaptive optics (AO) which allows giant earth-based telescopes, such as the 10 meter W.M. Keck telescope, to partially overcome the blurring effects of atmospheric turbulence. The second is looking for young planets: by searching in the infrared for companions to young stars, we can see thermal emission from planets that are still warm with the heat of their formation. Together with a UCLA team that leads the

A review of the US Global Change Research Program and NASA's Mission to Planet Earth/Earth Observing System

Science.gov (United States)

Moore, Berrien, III; Anderson, James G.; Costanza, Robert; Gates, W. Lawrence; Grew, Priscilla C.; Leinen, Margaret S.; Mayewski, Paul A.; McCarthy, James J.; Sellers, Piers J.

1995-01-01

This report reflects the results of a ten-day workshop convened at the Scripps Institution of Oceanography July 19-28, 1995. The workshop was convened as the first phase of a two part review of the U.S. Global Change Research Program (USGCRP). The workshop was organized to provide a review of the scientific foundations and progress to date in the USGCRP and an assessment of the implications of new scientific insights for future USGCRP and Mission to Planet Earth/Earth Observing System (MTPE/EOS) activities; a review of the role of NASA's MTPE/EOS program in the USGCRP observational strategy; a review of the EOS Data and Information System (EOSDIS) as a component of USGCRP data management activities; and an assessment of whether recent developments in the following areas lead to a need to readjust MTPE/EOS plans. Specific consideration was given to: proposed convergence of U.S. environmental satellite systems and programs, evolving international plans for Earth observation systems, advances in technology, and potential expansion of the role of the private sector. The present report summarizes the findings and recommendations developed by the Committee on Global Change Research on the basis of the presentations, background materials, working group deliberations, and plenary discussions of the workshop. In addition, the appendices include summaries prepared by the six working groups convened in the course of the workshop.

ERA-PLANET THE EUROPEAN NETWORK FOR OBSERVING OUR CHANGING PLANET

Directory of Open Access Journals (Sweden)

N. Pirrone

2016-06-01

Full Text Available In the last decade a significant number of projects and programmes in different domains of Earth Observation and environmental monitoring have generated a substantial amount of data and knowledge on different aspects related to environmental quality and sustainability. Big data generated by in-situ or satellite platforms are being collected and archived with a plethora of systems and instruments making difficult the sharing of data and transfer of knowledge to stakeholders and policy makers to support key economic and societal sectors. The overarching goal of ERAPLANET is to strengthen the European Research Area in the domain of Earth Observation in coherence with the European participation in the Group on Earth Observation (GEO and Copernicus. The expected impact is to strengthen European leadership within the forthcoming GEO 2015-2025 Work Plan. ERA-PLANET is designed to reinforce the interface with user communities, whose needs the Global Earth Observation System of Systems (GEOSS intends to address. It will provide more accurate, comprehensive and authoritative information to policy and decision-makers in key societal benefit areas, such as Smart Cities and Resilient Societies; Resource efficiency and Environmental management; Global changes and Environmental treaties; Polar areas and Natural resources. ERA-PLANET will provide advanced decision-support tools and technologies aimed to better monitor our global environment and share the information and knowledge available in the different domains of Earth Observation.

Era-Planet the European Network for Observing Our Changing Planet

Science.gov (United States)

Pirrone, N.; Cinnirella, S.; Nativi, S.; Sprovieri, F.; Hedgecock, I. M.

2016-06-01

In the last decade a significant number of projects and programmes in different domains of Earth Observation and environmental monitoring have generated a substantial amount of data and knowledge on different aspects related to environmental quality and sustainability. Big data generated by in-situ or satellite platforms are being collected and archived with a plethora of systems and instruments making difficult the sharing of data and transfer of knowledge to stakeholders and policy makers to support key economic and societal sectors. The overarching goal of ERAPLANET is to strengthen the European Research Area in the domain of Earth Observation in coherence with the European participation in the Group on Earth Observation (GEO) and Copernicus. The expected impact is to strengthen European leadership within the forthcoming GEO 2015-2025 Work Plan. ERA-PLANET is designed to reinforce the interface with user communities, whose needs the Global Earth Observation System of Systems (GEOSS) intends to address. It will provide more accurate, comprehensive and authoritative information to policy and decision-makers in key societal benefit areas, such as Smart Cities and Resilient Societies; Resource efficiency and Environmental management; Global changes and Environmental treaties; Polar areas and Natural resources. ERA-PLANET will provide advanced decision-support tools and technologies aimed to better monitor our global environment and share the information and knowledge available in the different domains of Earth Observation.

Tracing the ingredients for a habitable earth from interstellar space through planet formation.

Science.gov (United States)

Bergin, Edwin A; Blake, Geoffrey A; Ciesla, Fred; Hirschmann, Marc M; Li, Jie

2015-07-21

We use the C/N ratio as a monitor of the delivery of key ingredients of life to nascent terrestrial worlds. Total elemental C and N contents, and their ratio, are examined for the interstellar medium, comets, chondritic meteorites, and terrestrial planets; we include an updated estimate for the bulk silicate Earth (C/N = 49.0 ± 9.3). Using a kinetic model of disk chemistry, and the sublimation/condensation temperatures of primitive molecules, we suggest that organic ices and macromolecular (refractory or carbonaceous dust) organic material are the likely initial C and N carriers. Chemical reactions in the disk can produce nebular C/N ratios of ∼1-12, comparable to those of comets and the low end estimated for planetesimals. An increase of the C/N ratio is traced between volatile-rich pristine bodies and larger volatile-depleted objects subjected to thermal/accretional metamorphism. The C/N ratios of the dominant materials accreted to terrestrial planets should therefore be higher than those seen in carbonaceous chondrites or comets. During planetary formation, we explore scenarios leading to further volatile loss and associated C/N variations owing to core formation and atmospheric escape. Key processes include relative enrichment of nitrogen in the atmosphere and preferential sequestration of carbon by the core. The high C/N bulk silicate Earth ratio therefore is best satisfied by accretion of thermally processed objects followed by large-scale atmospheric loss. These two effects must be more profound if volatile sequestration in the core is effective. The stochastic nature of these processes hints that the surface/atmospheric abundances of biosphere-essential materials will likely be variable.

A STATISTICAL RECONSTRUCTION OF THE PLANET POPULATION AROUND KEPLER SOLAR-TYPE STARS

International Nuclear Information System (INIS)

Silburt, Ari; Wu, Yanqin; Gaidos, Eric

2015-01-01

Using the cumulative catalog of planets detected by the NASA Kepler mission, we reconstruct the intrinsic occurrence of Earth- to Neptune-size (1-4 R ⊕ ) planets and their distributions with radius and orbital period. We analyze 76,711 solar-type (0.8 < R * /R ☉ < 1.2) stars with 430 planets on 20-200 day orbits, excluding close-in planets that may have been affected by the proximity to the host star. Our analysis considers errors in planet radii and includes an ''iterative simulation'' technique that does not bin the data. We find a radius distribution that peaks at 2-2.8 Earth radii, with lower numbers of smaller and larger planets. These planets are uniformly distributed with logarithmic period, and the mean number of such planets per star is 0.46 ± 0.03. The occurrence is ∼0.66 if planets interior to 20 days are included. We estimate the occurrence of Earth-size planets in the ''habitable zone'' (defined as 1-2 R ⊕ , 0.99-1.7 AU for solar-twin stars) as 6.4 −1.1 +3.4 %. Our results largely agree with those of Petigura et al., although we find a higher occurrence of 2.8-4 Earth-radii planets. The reasons for this excess are the inclusion of errors in planet radius, updated Huber et al. stellar parameters, and also the exclusion of planets that may have been affected by proximity to the host star

Hydrothermal systems in small ocean planets.

Science.gov (United States)

Vance, Steve; Harnmeijer, Jelte; Kimura, Jun; Hussmann, Hauke; Demartin, Brian; Brown, J Michael

2007-12-01

We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system-for example, high or low temperature system or chemically driven system. As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets-Mars, a number of icy satellites, Pluto, and other trans-neptunian objects-and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth. In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 10(9) and 10(10) molecules cm(2) s(1).

Human impact on the planet: an earth system science perspective and ethical considerations

Science.gov (United States)

Williams, Richard S.

2002-01-01

natural and human history to stop further degradation of Earth?s ecosystems and extinction of its biota? The fate of the biosphere, including humanity, depends on a reaffirmation by all humans of all cultures and religions of the global importance of a planet-wide conservation of the Earth?s biotic heritage. For the world?s religions it means elevation of stewardship of the Earth to a moral imperative and a goal of complete preservation of the Earth?s biotic inheritance, one which is based on a Do No Harm ethic.

Cosmic Rays in Magnetospheres of the Earth and other Planets

CERN Document Server

Dorman, Lev

2009-01-01

This monograph describes the behaviour of cosmic rays in the magnetosphere of the Earth and of some other planets. Recently this has become an important topic both theoretically, because it is closely connected with the physics of the Earth’s magnetosphere, and practically, since cosmic rays determine a significant part of space weather effects on satellites and aircraft. The book contains eight chapters, dealing with – The history of the discovery of geomagnetic effects caused by cosmic rays and their importance for the determination of the nature of cosmic rays or gamma rays – The first explanations of geomagnetic effects within the framework of the dipole approximation of the Earth’s magnetic field – Trajectory computations of cutoff rigidities, transmittance functions, asymptotic directions, and acceptance cones in the real geomagnetic field taking into account higher harmonics – Cosmic ray latitude-longitude surveys on ships, trains, tracks, planes, balloons and satellites for determining the...

VULCAN PLANETS: INSIDE-OUT FORMATION OF THE INNERMOST SUPER-EARTHS

Energy Technology Data Exchange (ETDEWEB)

Chatterjee, Sourav [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Tan, Jonathan C., E-mail: sourav.chatterjee@northwestern.edu, E-mail: jt@astro.ufl.edu [Departments of Astronomy and Physics, University of Florida, Gainesville, FL 32611 (United States)

2015-01-10

The compact multi-transiting systems discovered by Kepler challenge traditional planet formation theories. These fall into two broad classes: (1) formation further out followed by migration and (2) formation in situ from a disk of gas and planetesimals. In the former, an abundance of resonant chains is expected, which the Kepler data do not support. In the latter, required disk mass surface densities may be too high. A recently proposed mechanism hypothesizes that planets form in situ at the pressure trap associated with the dead-zone inner boundary (DZIB) where radially drifting ''pebbles'' accumulate. This scenario predicts planet masses (M{sub p} ) are set by the gap-opening process that then leads to DZIB retreat, followed by sequential, inside-out planet formation (IOPF). For typical disk accretion rates, IOPF predictions for M{sub p} , M{sub p} versus orbital radius r, and planet-planet separations are consistent with observed systems. Here we investigate the IOPF prediction for how the masses, M{sub p,} {sub 1}, of the innermost (''Vulcan'') planets vary with r. We show that for fiducial parameters, M {sub p,} {sub 1} ≅ 5.0(r/0.1 AU) M {sub ⊕}, independent of the disk's accretion rate at time of planet formation. Then, using Monte Carlo sampling of a population of these innermost planets, we test this predicted scaling against observed planet properties, allowing for intrinsic dispersions in planetary densities and Kepler's observational biases. These effects lead to a slightly shallower relation M{sub p,} {sub 1}∝r {sup 0.9} {sup ±} {sup 0.2}, which is consistent with M{sub p,} 1∝r {sup 0.7} {sup ±} {sup 0.2} of the observed Vulcans. The normalization of the relation constrains the gap-opening process, favoring relatively low viscosities in the inner dead zone.

Three regimes of extrasolar planet radius inferred from host star metallicities.

Science.gov (United States)

Buchhave, Lars A; Bizzarro, Martin; Latham, David W; Sasselov, Dimitar; Cochran, William D; Endl, Michael; Isaacson, Howard; Juncher, Diana; Marcy, Geoffrey W

2014-05-29

Approximately half of the extrasolar planets (exoplanets) with radii less than four Earth radii are in orbits with short periods. Despite their sheer abundance, the compositions of such planets are largely unknown. The available evidence suggests that they range in composition from small, high-density rocky planets to low-density planets consisting of rocky cores surrounded by thick hydrogen and helium gas envelopes. Here we report the metallicities (that is, the abundances of elements heavier than hydrogen and helium) of more than 400 stars hosting 600 exoplanet candidates, and find that the exoplanets can be categorized into three populations defined by statistically distinct (∼4.5σ) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (radii less than 1.7 Earth radii), gas dwarf planets with rocky cores and hydrogen-helium envelopes (radii between 1.7 and 3.9 Earth radii) and ice or gas giant planets (radii greater than 3.9 Earth radii). These transitions correspond well with those inferred from dynamical mass estimates, implying that host star metallicity, which is a proxy for the initial solids inventory of the protoplanetary disk, is a key ingredient regulating the structure of planetary systems.

Lunar Science from and for Planet Earth

Science.gov (United States)

Pieters, M. C.; Hiesinger, H.; Head, J. W., III

2008-09-01

Our Moon Every person on Earth is familiar with the Moon. Every resident with nominal eyesight on each continent has seen this near-by planetary body with their own eyes countless times. Those fortunate enough to have binoculars or access to a telescope have explored the craters, valleys, domes, and plains across the lunar surface as changing lighting conditions highlight the mysteries of this marvellously foreign landscape. Schoolchildren learn that the daily rhythm and flow of tides along the coastlines of our oceans are due to the interaction of the Earth and the Moon. This continuous direct and personal link is but one of the many reasons lunar science is fundamental to humanity. The Earth-Moon System In the context of space exploration, our understanding of the Earth-Moon system has grown enormously. The Moon has become the cornerstone for most aspects of planetary science that relate to the terrestrial (rocky) planets. The scientific context for exploration of the Moon is presented in a recent report by a subcommittee of the Space Studies Board of the National Research Council [free from the website: http://books.nap.edu/catalog.php?record_id=11954]. Figure 1 captures the interwoven themes surrounding lunar science recognized and discussed in that report. In particular, it is now recognized that the Earth and the Moon have been intimately linked in their early history. Although they subsequently took very different evolutionary paths, the Moon provides a unique and valuable window both into processes that occurred during the first 600 Million years of solar system evolution (planetary differentiation and the heavy bombardment record) as well as the (ultimately dangerous) impact record of more recent times. This additional role of the Moon as keystone is because the Earth and the Moon share the same environment at 1 AU, but only the Moon retains a continuous record of cosmic events. An Initial Bloom of Exploration and Drought The space age celebrated its 50th

The Effect of Varying Atmospheric Pressure upon Habitability and Biosignatures of Earth-like Planets.

Science.gov (United States)

Keles, Engin; Grenfell, John Lee; Godolt, Mareike; Stracke, Barbara; Rauer, Heike

2018-02-01

Understanding the possible climatic conditions on rocky extrasolar planets, and thereby their potential habitability, is one of the major subjects of exoplanet research. Determining how the climate, as well as potential atmospheric biosignatures, changes under different conditions is a key aspect when studying Earth-like exoplanets. One important property is the atmospheric mass, hence pressure and its influence on the climatic conditions. Therefore, the aim of the present study is to understand the influence of atmospheric mass on climate, hence habitability, and the spectral appearance of planets with Earth-like, that is, N 2 -O 2 dominated, atmospheres orbiting the Sun at 1 AU. This work utilizes a 1D coupled, cloud-free, climate-photochemical atmospheric column model; varies atmospheric surface pressure from 0.5 to 30 bar; and investigates temperature and key species profiles, as well as emission and brightness temperature spectra in a range between 2 and 20 μm. Increasing the surface pressure up to 4 bar leads to an increase in the surface temperature due to increased greenhouse warming. Above this point, Rayleigh scattering dominates, and the surface temperature decreases, reaching surface temperatures below 273 K (approximately at ∼34 bar surface pressure). For ozone, nitrous oxide, water, methane, and carbon dioxide, the spectral response either increases with surface temperature or pressure depending on the species. Masking effects occur, for example, for the bands of the biosignatures ozone and nitrous oxide by carbon dioxide, which could be visible in low carbon dioxide atmospheres. Key Words: Planetary habitability and biosignatures-Atmospheres-Radiative transfer. Astrobiology 18, 116-132.

Characterization of Extrasolar Planets Using SOFIA

Science.gov (United States)

Deming, Drake

2010-01-01

Topics include: the landscape of extrasolar planets, why focus on transiting planets, some history and Spitzer results, problems in atmospheric structure or hot Jupiters and hot super Earths, what observations are needed to make progress, and what SOFIA can currently do and comments on optimized instruments.

Kepler's first rocky planet

DEFF Research Database (Denmark)

Batalha, N.M.; Borucki, W.J.; Bryson, S.T.

2011-01-01

NASA's Kepler Mission uses transit photometry to determine the frequency of Earth-size planets in or near the habitable zone of Sun-like stars. The mission reached a milestone toward meeting that goal: the discovery of its first rocky planet, Kepler-10b. Two distinct sets of transit events were...... tests on the photometric and pixel flux time series established the viability of the planet candidates triggering ground-based follow-up observations. Forty precision Doppler measurements were used to confirm that the short-period transit event is due to a planetary companion. The parent star is bright...

Worlds beyond our own the search for habitable planets

CERN Document Server

Sengupta, Sujan

2015-01-01

This is a book on planets: Solar system planets and dwarf planets. And planets outside our solar system – exoplanets. How did they form? What types of planets are there and what do they have in common? How do they differ? What do we know about their atmospheres – if they have one? What are the conditions for life and on which planets may they be met? And what’s the origin of life on Earth and how did it form? You will understand how rare the solar system, the Earth and hence life is. This is also a book on stars. The first and second generation of stars in the Universe. But in particular also on the link between planets and stars – brown dwarfs. Their atmospheric properties and similarities with giant exoplanets. All these fascinating questions will be answered in a non-technical manner. But those of you who want to know a bit more may look up the relevant mathematical relationships in appendices.

Guide to the universe inner planets

CERN Document Server

Grier, Jennifer

2009-01-01

This volume in the Greenwood Guides to the Universe series covers the inner planets-Mercury, Venus, Earth, and Mars. Thematic chapters discuss all of the many areas of astronomical research surrounding each subject, providing readers with the most up-to-date understanding of current knowledge and the ways in which it has been obtained. Like all of the books in this series, Inner Planets is scientifically sound, but written with the student in mind. It is an excellent first step for researching the exciting scientific discoveries of the Earth and its closest neighbors.

Comparative Climatology of Terrestrial Planets

Science.gov (United States)

Mackwell, Stephen J.; Simon-Miller, Amy A.; Harder, Jerald W.; Bullock, Mark A.

Public awareness of climate change on Earth is currently very high, promoting significant interest in atmospheric processes. We are fortunate to live in an era where it is possible to study the climates of many planets, including our own, using spacecraft and groundbased observations as well as advanced computational power that allows detailed modeling. Planetary atmospheric dynamics and structure are all governed by the same basic physics. Thus differences in the input variables (such as composition, internal structure, and solar radiation) among the known planets provide a broad suite of natural laboratory settings for gaining new understanding of these physical processes and their outcomes. Diverse planetary settings provide insightful comparisons to atmospheric processes and feedbacks on Earth, allowing a greater understanding of the driving forces and external influences on our own planetary climate. They also inform us in our search for habitable environments on planets orbiting distant stars, a topic that was a focus of Exoplanets, the preceding book in the University of Arizona Press Space Sciences Series. Quite naturally, and perhaps inevitably, our fascination with climate is largely driven toward investigating the interplay between the early development of life and the presence of a suitable planetary climate. Our understanding of how habitable planets come to be begins with the worlds closest to home. Venus, Earth, and Mars differ only modestly in their mass and distance from the Sun, yet their current climates could scarcely be more divergent. Our purpose for this book is to set forth the foundations for this emerging science and to bring to the forefront our current understanding of atmospheric formation and climate evolution. Although there is significant comparison to be made to atmospheric processes on nonterrestrial planets in our solar system — the gas and ice giants — here we focus on the terrestrial planets, leaving even broader comparisons

Alpha Centauri's siren call has frustrated planet hunters

Science.gov (United States)

Clery, Daniel

2018-04-01

Alpha Centauri, a three-star system just 4 light-years away that is the sun's nearest neighbor, ought to be a great place to look for Earth-like planets. But last week, at a meeting of the European Astronomical Society here, astronomers lamented that the system has so far thwarted discovery efforts—and announced new schemes to probe it. The two sunlike stars, Alpha Centauri A and B, orbit each other closely while Proxima Centauri, a tempestuous red dwarf, hangs onto the system tenuously in a much more distant orbit. In 2016, astronomers discovered an Earth-mass planet around Proxima Centauri, but few think the planet, blasted by radiation and fierce stellar winds, is habitable. Astrobiologists believe the other two stars are more likely to host temperate, Earth-like worlds.

Characterizing the Purple Earth: Modeling the globally integrated spectral variability of the Archean Earth

International Nuclear Information System (INIS)

Sanromá, E.; Pallé, E.; López, R.; Montañés-Rodríguez, P.; Parenteau, M. N.; Kiang, N. Y.; Gutiérrez-Navarro, A. M.

2014-01-01

Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. However, the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3.0 Gyr ago. At that time, one of the more widespread life forms on the planet was purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and purple bacteria concentration/distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

A Model of the Temporal Variability of Optical Light from Extrasolar Terrestrial Planets

OpenAIRE

Ford, Eric B.; Seager, Sara; Turner, Edwin L.

2002-01-01

The light scattered by an extrasolar Earth-like planet's surface and atmosphere will vary in intensity and color as the planet rotates; the resulting light curve will contain information about the planet's properties. Since most of the light comes from a small fraction of the planet's surface, the temporal flux variability can be quite significant, $\\sim$ 10-100%. In addition, for cloudless Earth-like extrasolar planet models, qualitative changes to the surface (such as ocean fraction, ice co...

MAKING PLANET NINE: A SCATTERED GIANT IN THE OUTER SOLAR SYSTEM

International Nuclear Information System (INIS)

Bromley, Benjamin C.; Kenyon, Scott J.

2016-01-01

Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least 10 times the mass of the Earth and a perihelion well beyond 100 au, Planet Nine poses a challenge to planet formation theory. Here we expand on a scenario in which the planet formed closer to the Sun and was gravitationally scattered by Jupiter or Saturn onto a very eccentric orbit in an extended gaseous disk. Dynamical friction with the gas then allowed the planet to settle in the outer solar system. We explore this possibility with a set of numerical simulations. Depending on how the gas disk evolves, scattered super-Earths or small gas giants settle on a range of orbits, with perihelion distances as large as 300 au. Massive disks that clear from the inside out on million-year timescales yield orbits that allow a super-Earth or gas giant to shepherd the minor planets as observed. A massive planet can achieve a similar orbit in a persistent, low-mass disk over the lifetime of the solar system.

MAKING PLANET NINE: A SCATTERED GIANT IN THE OUTER SOLAR SYSTEM

Energy Technology Data Exchange (ETDEWEB)

Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 South 1400 East, Room 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2016-07-20

Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least 10 times the mass of the Earth and a perihelion well beyond 100 au, Planet Nine poses a challenge to planet formation theory. Here we expand on a scenario in which the planet formed closer to the Sun and was gravitationally scattered by Jupiter or Saturn onto a very eccentric orbit in an extended gaseous disk. Dynamical friction with the gas then allowed the planet to settle in the outer solar system. We explore this possibility with a set of numerical simulations. Depending on how the gas disk evolves, scattered super-Earths or small gas giants settle on a range of orbits, with perihelion distances as large as 300 au. Massive disks that clear from the inside out on million-year timescales yield orbits that allow a super-Earth or gas giant to shepherd the minor planets as observed. A massive planet can achieve a similar orbit in a persistent, low-mass disk over the lifetime of the solar system.

Making Planet Nine: A Scattered Giant in the Outer Solar System

Science.gov (United States)

Bromley, Benjamin C.; Kenyon, Scott J.

2016-07-01

Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least 10 times the mass of the Earth and a perihelion well beyond 100 au, Planet Nine poses a challenge to planet formation theory. Here we expand on a scenario in which the planet formed closer to the Sun and was gravitationally scattered by Jupiter or Saturn onto a very eccentric orbit in an extended gaseous disk. Dynamical friction with the gas then allowed the planet to settle in the outer solar system. We explore this possibility with a set of numerical simulations. Depending on how the gas disk evolves, scattered super-Earths or small gas giants settle on a range of orbits, with perihelion distances as large as 300 au. Massive disks that clear from the inside out on million-year timescales yield orbits that allow a super-Earth or gas giant to shepherd the minor planets as observed. A massive planet can achieve a similar orbit in a persistent, low-mass disk over the lifetime of the solar system.

Kepler Mission: A Wide-FOV Photometer Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-like stars

Science.gov (United States)

Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Jenkins, Jon M.; Caldwell, Douglas;

The hottest planet.

Science.gov (United States)

Harrington, Joseph; Luszcz, Statia; Seager, Sara; Deming, Drake; Richardson, L Jeremy

2007-06-07

Of the over 200 known extrasolar planets, just 14 pass in front of and behind their parent stars as seen from Earth. This fortuitous geometry allows direct determination of many planetary properties. Previous reports of planetary thermal emission give fluxes that are roughly consistent with predictions based on thermal equilibrium with the planets' received radiation, assuming a Bond albedo of approximately 0.3. Here we report direct detection of thermal emission from the smallest known transiting planet, HD 149026b, that indicates a brightness temperature (an expression of flux) of 2,300 +/- 200 K at 8 microm. The planet's predicted temperature for uniform, spherical, blackbody emission and zero albedo (unprecedented for planets) is 1,741 K. As models with non-zero albedo are cooler, this essentially eliminates uniform blackbody models, and may also require an albedo lower than any measured for a planet, very strong 8 microm emission, strong temporal variability, or a heat source other than stellar radiation. On the other hand, an instantaneous re-emission blackbody model, in which each patch of surface area instantly re-emits all received light, matches the data. This planet is known to be enriched in heavy elements, which may give rise to novel atmospheric properties yet to be investigated.

Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars.

Science.gov (United States)

Kasting, James F; Kopparapu, Ravikumar; Ramirez, Ramses M; Harman, Chester E

2014-09-02

The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, S(eff), the recently recalculated HZ boundaries are: recent Venus--1.78; runaway greenhouse--1.04; moist greenhouse--1.01; maximum greenhouse--0.35; and early Mars--0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5.

CHARACTERIZING THE ATMOSPHERES OF TRANSITING ROCKY PLANETS AROUND LATE-TYPE DWARFS

International Nuclear Information System (INIS)

Palle, E.; Garcia Munoz, A.; Zosorio, M. R. Zapatero

2011-01-01

Visible and near-infrared spectra of transiting hot Jupiter planets have recently been observed, revealing some of the atmospheric constituents of their atmospheres. In the near future, it is probable that primary and secondary eclipse observations of Earth-like rocky planets will also be achieved. The characterization of Earth's transmission spectrum has shown that both major and trace atmospheric constituents may present strong absorption features, including important bio-markers such as water, oxygen, and methane. Our simulations using a recently published empirical Earth's transmission spectrum, and the stellar spectra for a variety of stellar types, indicate that the new generation of extremely large telescopes, such as the proposed 42 m European Extremely Large Telescope, could be capable of retrieving the transmission spectrum of an Earth-like planet around very cool stars and brown dwarfs (T eff ≤ ∼3100 K). For a twin of Earth around a star with T eff ∼ 3100 K (M4), for example, the spectral features of H 2 O, CH 4 , CO 2 , and O 2 in the wavelength range between 0.9 and 2.4 μm can simultaneously be detected within 100 hr of observing time, or even less for a late-M star. Such detection would constitute proof for the existence of life in that planet. The detection time can be reduced to a few hours for a super-Earth type of planet with twice Earth's radius.

The HARPS search for southern extra-solar planets . XXXII. New multi-planet systems in the HARPS volume limited sample: a super-Earth and a Neptune in the habitable zone

Science.gov (United States)

Lo Curto, G.; Mayor, M.; Benz, W.; Bouchy, F.; Hébrard, G.; Lovis, C.; Moutou, C.; Naef, D.; Pepe, F.; Queloz, D.; Santos, N. C.; Segransan, D.; Udry, S.

2013-03-01

The vast diversity of planetary systems detected to date is defying our capability of understanding their formation and evolution. Well-defined volume-limited surveys are the best tool at our disposal to tackle the problem, via the acquisition of robust statistics of the orbital elements. We are using the HARPS spectrograph to conduct our survey of ≈850 nearby solar-type stars, and in the course of the past nine years we have monitored the radial velocity of HD 103774, HD 109271, and BD-061339. In this work we present the detection of five planets orbiting these stars, with msin (i) between 0.6 and 7 Neptune masses, four of which are in two multiple systems, comprising one super-Earth and one planet within the habitable zone of a late-type dwarf. Although for strategic reasons we chose efficiency over precision in this survey, we have the capability to detect planets down to the Neptune and super-Earth mass range as well as multiple systems, provided that enough data points are made available. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla (Chile), under the GTO program ID 072.C-0488 and the regular programs: 085.C-0019, 087.C-0831 and 089.C-0732. RV data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/551/A59

Extrasolar planets searches today and tomorrow

CERN Multimedia

2000-01-01

So far the searches for extrasolar planets have found 40 planetary companions orbiting around nearby stars. In December 1999 a transit has been observed for one of them, providing the first independent confirmation of the reality of close-in planets as well as a measurement of its density. The techniques used to detect planets are limited and the detection threshold is biased but a first picture of the planet diversity and distribution emerges. Results of the search for extra-solar planets and their impacts on planetary formation will be reviewed. Future instruments are foreseen to detect Earth-like planets and possible signatures of organic activity. An overview of these future projects will be presented and more particularly the Darwin-IRSI mission studied by ESA for Horizon 2015.

Increased insolation threshold for runaway greenhouse processes on Earth-like planets.

Science.gov (United States)

Leconte, Jérémy; Forget, Francois; Charnay, Benjamin; Wordsworth, Robin; Pottier, Alizée

2013-12-12

The increase in solar luminosity over geological timescales should warm the Earth's climate, increasing water evaporation, which will in turn enhance the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can 'run away' until the oceans have completely evaporated. Through increases in stratospheric humidity, warming may also cause evaporative loss of the oceans to space before the runaway greenhouse state occurs. The critical insolation thresholds for these processes, however, remain uncertain because they have so far been evaluated using one-dimensional models that cannot account for the dynamical and cloud feedback effects that are key stabilizing features of the Earth's climate. Here we use a three-dimensional global climate model to show that the insolation threshold for the runaway greenhouse state to occur is about 375 W m(-2), which is significantly higher than previously thought. Our model is specifically developed to quantify the climate response of Earth-like planets to increased insolation in hot and extremely moist atmospheres. In contrast with previous studies, we find that clouds have a destabilizing feedback effect on the long-term warming. However, subsident, unsaturated regions created by the Hadley circulation have a stabilizing effect that is strong enough to shift the runaway greenhouse limit to higher values of insolation than are inferred from one-dimensional models. Furthermore, because of wavelength-dependent radiative effects, the stratosphere remains sufficiently cold and dry to hamper the escape of atmospheric water, even at large fluxes. This has strong implications for the possibility of liquid water existing on Venus early in its history, and extends the size of the habitable zone around other stars.

Which Type of Planets do We Expect to Observe in the Habitable Zone?

Science.gov (United States)

Adibekyan, Vardan; Figueira, Pedro; Santos, Nuno C

2016-11-01

We used a sample of super-Earth-like planets detected by the Doppler spectroscopy and transit techniques to explore the dependence of orbital parameters of the planets on the metallicity of their host stars. We confirm the previous results (although still based on small samples of planets) that super-Earths orbiting around metal-rich stars are not observed to be as distant from their host stars as we observe their metal-poor counterparts to be. The orbits of these super-Earths with metal-rich hosts usually do not reach into the Habitable Zone (HZ), keeping them very hot and inhabitable. We found that most of the known planets in the HZ are orbiting their GK-type hosts which are metal-poor. The metal-poor nature of planets in the HZ suggests a high Mg abundance relative to Si and high Si abundance relative to Fe. These results lead us to speculate that HZ planets might be more frequent in the ancient Galaxy and had compositions different from that of our Earth.

Beyond the principle of plentitude: a review of terrestrial planet habitability.

Science.gov (United States)

Gaidos, E; Deschenes, B; Dundon, L; Fagan, K; Menviel-Hessler, L; Moskovitz, N; Workman, M

2005-04-01

We review recent work that directly or indirectly addresses the habitability of terrestrial (rocky) planets like the Earth. Habitability has been traditionally defined in terms of an orbital semimajor axis within a range known as the habitable zone, but it is also well known that the habitability of Earth is due to many other astrophysical, geological, and geochemical factors. We focus this review on (1) recent refinements to habitable zone calculations; (2) the formation and orbital stability of terrestrial planets; (3) the tempo and mode of geologic activity (e.g., plate tectonics) on terrestrial planets; (4) the delivery of water to terrestrial planets in the habitable zone; and (5) the acquisition and loss of terrestrial planet carbon and nitrogen, elements that constitute important atmospheric gases responsible for habitable conditions on Earth's surface as well as being the building blocks of the biosphere itself. Finally, we consider recent work on evidence for the earliest habitable environments and the appearance of life itself on our planet. Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds.

M2K. II. A TRIPLE-PLANET SYSTEM ORBITING HIP 57274

Energy Technology Data Exchange (ETDEWEB)

Fischer, Debra A.; Giguere, Matthew J.; Moriarty, John; Brewer, John; Spronck, Julien F. P.; Schwab, Christian; Szymkowiak, Andrew [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822 (United States); Howard, Andrew W.; Marcy, Geoffrey W. [Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720 (United States); Johnson, John A. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Wright, Jason T. [Center for Exoplanets and Habitable Worlds, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16803 (United States); Valenti, Jeff A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Piskunov, Nikolai [Department of Astronomy and Space Physics, Uppsala University, Box 515, 751 20 Uppsala (Sweden); Clubb, Kelsey I.; Isaacson, Howard [Pufendorf Institute for Advanced Studies, Lund University, Lund (Sweden); Apps, Kevin [75B Cheyne Walk, Surrey RH6 7LR (United Kingdom); Lepine, Sebastien [American Museum of Natural History, New York, NY 10023 (United States); Mann, Andrew, E-mail: debra.fischer@yale.edu [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

2012-01-20

Doppler observations from Keck Observatory have revealed a triple-planet system orbiting the nearby K4V star, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with Msin i = 11.6 M{sub Circled-Plus} (0.036 M{sub Jup}), an orbital period of 8.135 {+-} 0.004 days, and slightly eccentric orbit e = 0.19 {+-} 0.1. We calculate a transit probability of 6.5% for the inner planet. The second planet has Msin i = 0.4 M{sub Jup} with an orbital period of 32.0 {+-} 0.02 days in a nearly circular orbit (e = 0.05 {+-} 0.03). The third planet has Msin i = 0.53 M{sub Jup} with an orbital period of 432 {+-} 8 days (1.18 years) and an eccentricity e = 0.23 {+-} 0.03. This discovery adds to the number of super-Earth mass planets with M sin i < 12 M{sub Circled-Plus} that have been detected with Doppler surveys. We find that 56% {+-} 18% of super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, 20% {+-} 8%, that are members of Doppler-detected, multi-planet systems.

M2K. II. A TRIPLE-PLANET SYSTEM ORBITING HIP 57274

International Nuclear Information System (INIS)

Fischer, Debra A.; Giguere, Matthew J.; Moriarty, John; Brewer, John; Spronck, Julien F. P.; Schwab, Christian; Szymkowiak, Andrew; Gaidos, Eric; Howard, Andrew W.; Marcy, Geoffrey W.; Johnson, John A.; Wright, Jason T.; Valenti, Jeff A.; Piskunov, Nikolai; Clubb, Kelsey I.; Isaacson, Howard; Apps, Kevin; Lepine, Sebastien; Mann, Andrew

2012-01-01

Doppler observations from Keck Observatory have revealed a triple-planet system orbiting the nearby K4V star, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with Msin i = 11.6 M ⊕ (0.036 M Jup ), an orbital period of 8.135 ± 0.004 days, and slightly eccentric orbit e = 0.19 ± 0.1. We calculate a transit probability of 6.5% for the inner planet. The second planet has Msin i = 0.4 M Jup with an orbital period of 32.0 ± 0.02 days in a nearly circular orbit (e = 0.05 ± 0.03). The third planet has Msin i = 0.53 M Jup with an orbital period of 432 ± 8 days (1.18 years) and an eccentricity e = 0.23 ± 0.03. This discovery adds to the number of super-Earth mass planets with M sin i ⊕ that have been detected with Doppler surveys. We find that 56% ± 18% of super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, 20% ± 8%, that are members of Doppler-detected, multi-planet systems.

Wandering stars about planets and exo-planets : an introductory notebook

CERN Document Server

Cole, George H A

2006-01-01

The space vehicle spectaculars of recent years have been revealing the full scope and beauty of our own solar system but have also shown that a growing number of other stars too have planetary bodies orbiting around them. The study of these systems is just beginning. It seems that our galaxy contains untold numbers of planets, and presumably other galaxies will be similar to our own. Our solar system contains life, on Earth: do others as well? Such questions excite modern planetary scientists and astro-biologists. This situation is a far cry from ancient times when the five planets that can be

How does the Earth system generate and maintain thermodynamic disequilibrium and what does it imply for the future of the planet?

Science.gov (United States)

Kleidon, Axel

2012-01-01

The Earth's chemical composition far from chemical equilibrium is unique in our Solar System, and this uniqueness has been attributed to the presence of widespread life on the planet. Here, I show how this notion can be quantified using non-equilibrium thermodynamics. Generating and maintaining disequilibrium in a thermodynamic variable requires the extraction of power from another thermodynamic gradient, and the second law of thermodynamics imposes fundamental limits on how much power can be extracted. With this approach and associated limits, I show that the ability of abiotic processes to generate geochemical free energy that can be used to transform the surface–atmosphere environment is strongly limited to less than 1 TW. Photosynthetic life generates more than 200 TW by performing photochemistry, thereby substantiating the notion that a geochemical composition far from equilibrium can be a sign for strong biotic activity. Present-day free energy consumption by human activity in the form of industrial activity and human appropriated net primary productivity is of the order of 50 TW and therefore constitutes a considerable term in the free energy budget of the planet. When aiming to predict the future of the planet, we first note that since global changes are closely related to this consumption of free energy, and the demands for free energy by human activity are anticipated to increase substantially in the future, the central question in the context of predicting future global change is then how human free energy demands can increase sustainably without negatively impacting the ability of the Earth system to generate free energy. This question could be evaluated with climate models, and the potential deficiencies in these models to adequately represent the thermodynamics of the Earth system are discussed. Then, I illustrate the implications of this thermodynamic perspective by discussing the forms of renewable energy and planetary engineering that would

How does the Earth system generate and maintain thermodynamic disequilibrium and what does it imply for the future of the planet?

Science.gov (United States)

Kleidon, Axel

2012-03-13

The Earth's chemical composition far from chemical equilibrium is unique in our Solar System, and this uniqueness has been attributed to the presence of widespread life on the planet. Here, I show how this notion can be quantified using non-equilibrium thermodynamics. Generating and maintaining disequilibrium in a thermodynamic variable requires the extraction of power from another thermodynamic gradient, and the second law of thermodynamics imposes fundamental limits on how much power can be extracted. With this approach and associated limits, I show that the ability of abiotic processes to generate geochemical free energy that can be used to transform the surface-atmosphere environment is strongly limited to less than 1 TW. Photosynthetic life generates more than 200 TW by performing photochemistry, thereby substantiating the notion that a geochemical composition far from equilibrium can be a sign for strong biotic activity. Present-day free energy consumption by human activity in the form of industrial activity and human appropriated net primary productivity is of the order of 50 TW and therefore constitutes a considerable term in the free energy budget of the planet. When aiming to predict the future of the planet, we first note that since global changes are closely related to this consumption of free energy, and the demands for free energy by human activity are anticipated to increase substantially in the future, the central question in the context of predicting future global change is then how human free energy demands can increase sustainably without negatively impacting the ability of the Earth system to generate free energy. This question could be evaluated with climate models, and the potential deficiencies in these models to adequately represent the thermodynamics of the Earth system are discussed. Then, I illustrate the implications of this thermodynamic perspective by discussing the forms of renewable energy and planetary engineering that would

News and Views: Keep it down! AU becomes au, and is defined in metres; Kepler survey announces two planets in a binary star system; Is there plate tectonics on Mars? Vaporizing Earth - for research!

Science.gov (United States)

2012-10-01

Division 1 of the IAU recommended that the astronomical unit - originally the length of the semi-major axis of the Earth's orbit - be redefined as a fixed number of kilometres. A team of observers using data from NASA's Kepler space observatory announced at the IAU General Assembly that they had discovered two planets orbiting a pair of binary stars, and that such planets could exist in the habitable zone of their system. The Red Planet has long been considered something of a dead planet as far as tectonic movements of its crust, but careful analysis of thermal and topographic images of the surface suggest the existence of major faults with horizontal slip along the Valles Marineris. The question of what would happen if Earth were to approach the Sun and start vaporizing has been modelled in order to help to model the composition of super-Earths.

One or more bound planets per Milky Way star from microlensing observations.

Science.gov (United States)

Cassan, A; Kubas, D; Beaulieu, J-P; Dominik, M; Horne, K; Greenhill, J; Wambsganss, J; Menzies, J; Williams, A; Jørgensen, U G; Udalski, A; Bennett, D P; Albrow, M D; Batista, V; Brillant, S; Caldwell, J A R; Cole, A; Coutures, Ch; Cook, K H; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Hill, K; Kains, N; Kane, S; Marquette, J-B; Martin, R; Pollard, K R; Sahu, K C; Vinter, C; Warren, D; Watson, B; Zub, M; Sumi, T; Szymański, M K; Kubiak, M; Poleski, R; Soszynski, I; Ulaczyk, K; Pietrzyński, G; Wyrzykowski, L

2012-01-11

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10 AU (Sun-Earth distance) from their stars. We find that 17(+6)(-9)% of stars host Jupiter-mass planets (0.3-10 M(J), where M(J) = 318 M(⊕) and M(⊕) is Earth's mass). Cool Neptunes (10-30 M(⊕)) and super-Earths (5-10 M(⊕)) are even more common: their respective abundances per star are 52(+22)(-29)% and 62(+35)(-37)%. We conclude that stars are orbited by planets as a rule, rather than the exception.

DETECTING OCEANS ON EXTRASOLAR PLANETS USING THE GLINT EFFECT

International Nuclear Information System (INIS)

Robinson, Tyler D.; Meadows, Victoria S.; Crisp, David

2010-01-01

Glint, the specular reflection of sunlight off Earth's oceans, may reveal the presence of oceans on an extrasolar planet. As an Earth-like planet nears crescent phases, the size of the ocean glint spot increases relative to the fraction of the illuminated disk, while the reflectivity of this spot increases. Both effects change the planet's visible reflectivity as a function of phase. However, strong forward scattering of radiation by clouds can also produce increases in a planet's reflectivity as it approaches crescent phases, and surface glint can be obscured by Rayleigh scattering and atmospheric absorption. Here, we explore the detectability of glint in the presence of an atmosphere and realistic phase-dependent scattering from oceans and clouds. We use the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model to simulate Earth's broadband visible brightness and reflectivity over an orbit. Our validated simulations successfully reproduce phase-dependent Earthshine observations. We find that the glinting Earth can be as much as 100% brighter at crescent phases than simulations that do not include glint, and that the effect is dependent on both orbital inclination and wavelength, where the latter dependence is caused by Rayleigh scattering limiting sensitivity to the surface. We show that this phenomenon may be observable using the James Webb Space Telescope paired with an external occulter.

Mission to planet earth: A call to repeal the Landsat Act

International Nuclear Information System (INIS)

Gabrynowicz, J.I.; Wood, C.A.

1991-01-01

Mission to Planet Earth (MPE) is being planned to provide scientists with data and information about global climate change so that policymakers can make informed decisions in directing the nation's response to the change. A crucial component of MPE is the Landsat system and the continuous, multidecade database it has produced. Yet because of an ill-conceived and poorly-executed commercialization policy, MPE researchers are being deprived of these vital national assets, profoundly hampering their ability to carry out the work of MPE. Effects of the US commercialization policy have reached abroad. The French, Japanese, and Canadians, following the US lead, have also commercialized their existing and future land remote sensing systems - further inhibiting the free flow of data among these complementary systems and preventing a truly international, scientific effort in MPE. Meeting the challenges of global climate change requires reconsidering the proper role of the Landsat system and identifying appropriate and inappropriate commercial remote sensing activities

The Earth Microbiome Project and modeling the planets microbial potential (Invited)

Science.gov (United States)

Gilbert, J. A.

2013-12-01

The understanding of Earth's climate and ecology requires multiscale observations of the biosphere, of which microbial life are a major component. However, to acquire and process physical samples of soil, water and air that comprise the appropriate spatial and temporal resolution to capture the immense variation in microbial dynamics, would require a herculean effort and immense financial resources dwarfing even the most ambitious projects to date. To overcome this hurdle we created the Earth Microbiome Project, a crowd-sourced effort to acquire physical samples from researchers around the world that are, importantly, contextualized with physical, chemical and biological data detailing the environmental properties of that sample in the location and time it was acquired. The EMP leverages these existing efforts to target a systematic analysis of microbial taxonomic and functional dynamics across a vast array of environmental parameter gradients. The EMP captures the environmental gradients, location, time and sampling protocol information about every sample donated by our valued collaborators. Physical samples are then processed using a standardized DNA extraction, PCR, and shotgun sequencing protocol to generate comparable data regarding the microbial community structure and function in each sample. To date we have processed >17,000 samples from 40 different biomes. One of the key goals of the EMP is to map the spatiotemporal variability of microbial communities to capture the changes in important functional processes that need to be appropriately expressed in models to provide reliable forecasts of ecosystem phenotype across our changing planet. This is essential if we are to develop economically sound strategies to be good stewards of our Earth. The EMP recognizes that environments are comprised of complex sets of interdependent parameters and that the development of useful predictive computational models of both terrestrial and atmospheric systems requires

THE STEPPENWOLF: A PROPOSAL FOR A HABITABLE PLANET IN INTERSTELLAR SPACE

International Nuclear Information System (INIS)

Abbot, D. S.; Switzer, E. R.

2011-01-01

Rogue planets have been ejected from their planetary system. We investigate the possibility that a rogue planet could maintain a liquid ocean under layers of thermally insulating water ice and frozen gas as a result of geothermal heat flux. We find that a rogue planet of Earth-like composition and age could maintain a subglacial liquid ocean if it were ∼3.5 times more massive than Earth, corresponding to ∼8 km of ice. Suppression of the melting point by contaminants, a layer of frozen gas, or a larger complement of water could significantly reduce the planetary mass that is required to maintain a liquid ocean. Such a planet could be detected from reflected solar radiation, and its thermal emission could be characterized in the far-IR if it were to pass within O(1000) AU of Earth.

Planet Ocean

Science.gov (United States)

Afonso, Isabel

2014-05-01

A more adequate name for Planet Earth could be Planet Ocean, seeing that ocean water covers more than seventy percent of the planet's surface and plays a fundamental role in the survival of almost all living species. Actually, oceans are aqueous solutions of extraordinary importance due to its direct implications in the current living conditions of our planet and its potential role on the continuity of life as well, as long as we know how to respect the limits of its immense but finite capacities. We may therefore state that natural aqueous solutions are excellent contexts for the approach and further understanding of many important chemical concepts, whether they be of chemical equilibrium, acid-base reactions, solubility and oxidation-reduction reactions. The topic of the 2014 edition of GIFT ('Our Changing Planet') will explore some of the recent complex changes of our environment, subjects that have been lately included in Chemistry teaching programs. This is particularly relevant on high school programs, with themes such as 'Earth Atmosphere: radiation, matter and structure', 'From Atmosphere to the Ocean: solutions on Earth and to Earth', 'Spring Waters and Public Water Supply: Water acidity and alkalinity'. These are the subjects that I want to develop on my school project with my pupils. Geographically, our school is located near the sea in a region where a stream flows into the sea. Besides that, our school water comes from a borehole which shows that the quality of the water we use is of significant importance. This project will establish and implement several procedures that, supported by physical and chemical analysis, will monitor the quality of water - not only the water used in our school, but also the surrounding waters (stream and beach water). The samples will be collected in the borehole of the school, in the stream near the school and in the beach of Carcavelos. Several physical-chemical characteristics related to the quality of the water will

Planet traps and first planets: The critical metallicity for gas giant formation

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, Yasuhiro; Hirashita, Hiroyuki, E-mail: yasu@asiaa.sinica.edu.tw, E-mail: hirashita@asiaa.sinica.edu.tw [Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), P.O. Box 23-141, Taipei 10617, Taiwan (China)

2014-06-10

The ubiquity of planets poses an interesting question: when are first planets formed in galaxies? We investigate this by adopting a theoretical model where planet traps are combined with the standard core accretion scenario in which the efficiency of forming planetary cores directly relates to the metallicity ([Fe/H]) in disks. Three characteristic exoplanetary populations are examined: hot Jupiters, exo-Jupiters around 1 AU, and low-mass planets in tight orbits, such as super-Earths. We statistically compute planet formation frequencies (PFFs), as well as the orbital radius (〈R{sub rapid}〉) within which gas accretion becomes efficient enough to form Jovian planets, as a function of metallicity (–2 ≤ [Fe/H] ≤–0.6). We show that the total PFFs for these three populations increase steadily with metallicity. This is the direct outcome of the core accretion picture. For the metallicity range considered here, the population of low-mass planets dominates Jovian planets. The Jovian planets contribute to the PFFs above [Fe/H] ≅ –1. We find that the hot Jupiters form more efficiently than the exo-Jupiters at [Fe/H] ≲ –0.7. This arises from the slower growth of planetary cores and their more efficient radial inward transport by the host traps in lower metallicity disks. We show that the critical metallicity for forming Jovian planets is [Fe/H] ≅ –1.2 by comparing 〈R{sub rapid}〉 of hot Jupiters and low-mass planets. The comparison intrinsically links to the different gas accretion efficiency between these two types of planets. Therefore, this study implies that important physical processes in planet formation may be tested by exoplanet observations around metal-poor stars.

Planet traps and first planets: The critical metallicity for gas giant formation

International Nuclear Information System (INIS)

Hasegawa, Yasuhiro; Hirashita, Hiroyuki

2014-01-01

The ubiquity of planets poses an interesting question: when are first planets formed in galaxies? We investigate this by adopting a theoretical model where planet traps are combined with the standard core accretion scenario in which the efficiency of forming planetary cores directly relates to the metallicity ([Fe/H]) in disks. Three characteristic exoplanetary populations are examined: hot Jupiters, exo-Jupiters around 1 AU, and low-mass planets in tight orbits, such as super-Earths. We statistically compute planet formation frequencies (PFFs), as well as the orbital radius (〈R rapid 〉) within which gas accretion becomes efficient enough to form Jovian planets, as a function of metallicity (–2 ≤ [Fe/H] ≤–0.6). We show that the total PFFs for these three populations increase steadily with metallicity. This is the direct outcome of the core accretion picture. For the metallicity range considered here, the population of low-mass planets dominates Jovian planets. The Jovian planets contribute to the PFFs above [Fe/H] ≅ –1. We find that the hot Jupiters form more efficiently than the exo-Jupiters at [Fe/H] ≲ –0.7. This arises from the slower growth of planetary cores and their more efficient radial inward transport by the host traps in lower metallicity disks. We show that the critical metallicity for forming Jovian planets is [Fe/H] ≅ –1.2 by comparing 〈R rapid 〉 of hot Jupiters and low-mass planets. The comparison intrinsically links to the different gas accretion efficiency between these two types of planets. Therefore, this study implies that important physical processes in planet formation may be tested by exoplanet observations around metal-poor stars.

New planet hints at life in the stars

CERN Multimedia

Dalton, A W

2002-01-01

Astronomers have detected a distant planet 100 light years from Earth, circling Tau1 Gruis, its star, in the constellation of Grus (the crane). The planet, similar in appearance to Jupiter, is three times as far away from its star as the Earth is from the Sun and takes four years to revolve around the star, in a roughly circular orbit. Scientists believe this type of planetary orbit is the most promising for finding worlds that contain life (1 page).

Three regimes of extrasolar planet radius inferred from host star metallicities

DEFF Research Database (Denmark)

Buchhave, Lars A.; Bizzarro, Martin; Latham, David W.

2014-01-01

Approximately half of the extrasolar planets (exoplanets) with radii less than four Earth radii are in orbits with short periods. Despite their sheer abundance, the compositions of such planets are largely unknown. The available evidence suggests that they range in composition from small, high......-density rocky planets to low-density planets consisting of rocky cores surrounded by thick hydrogen and helium gas envelopes. Here we report the metallicities (that is, the abundances of elements heavier than hydrogen and helium) of more than 400 stars hosting 600 exoplanet candidates, and find...... that the exoplanets can be categorized into three populations defined by statistically distinct (~4.5σ) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (radii less than 1.7 Earth radii), gas dwarf planets with rocky cores and hydrogen-helium envelopes...

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

Terrestrial Planet Finder Coronagraph High Accuracy Optical Propagation, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The Terrestrial Planet Finder (TPF) project is considering several approaches to discovering planets orbiting stars far from earth and assessing their suitability to...

Emergence of two types of terrestrial planet on solidification of magma ocean.

Science.gov (United States)

Hamano, Keiko; Abe, Yutaka; Genda, Hidenori

2013-05-30

Understanding the origins of the diversity in terrestrial planets is a fundamental goal in Earth and planetary sciences. In the Solar System, Venus has a similar size and bulk composition to those of Earth, but it lacks water. Because a richer variety of exoplanets is expected to be discovered, prediction of their atmospheres and surface environments requires a general framework for planetary evolution. Here we show that terrestrial planets can be divided into two distinct types on the basis of their evolutionary history during solidification from the initially hot molten state expected from the standard formation model. Even if, apart from their orbits, they were identical just after formation, the solidified planets can have different characteristics. A type I planet, which is formed beyond a certain critical distance from the host star, solidifies within several million years. If the planet acquires water during formation, most of this water is retained and forms the earliest oceans. In contrast, on a type II planet, which is formed inside the critical distance, a magma ocean can be sustained for longer, even with a larger initial amount of water. Its duration could be as long as 100 million years if the planet is formed together with a mass of water comparable to the total inventory of the modern Earth. Hydrodynamic escape desiccates type II planets during the slow solidification process. Although Earth is categorized as type I, it is not clear which type Venus is because its orbital distance is close to the critical distance. However, because the dryness of the surface and mantle predicted for type II planets is consistent with the characteristics of Venus, it may be representative of type II planets. Also, future observations may have a chance to detect not only terrestrial exoplanets covered with water ocean but also those covered with magma ocean around a young star.

Discovery of a bright microlensing event with planetary features towards the Taurus region: a super-Earth planet

Science.gov (United States)

Nucita, A. A.; Licchelli, D.; De Paolis, F.; Ingrosso, G.; Strafella, F.; Katysheva, N.; Shugarov, S.

2018-05-01

The transient event labelled as TCP J05074264+2447555 recently discovered towards the Taurus region was quickly recognized to be an ongoing microlensing event on a source located at distance of only 700-800 pc from Earth. Here, we show that observations with high sampling rate close to the time of maximum magnification revealed features that imply the presence of a binary lens system with very low-mass ratio components. We present a complete description of the binary lens system, which host an Earth-like planet with most likely mass of 9.2 ± 6.6 M⊕. Furthermore, the source estimated location and detailed Monte Carlo simulations allowed us to classify the event as due to the closest lens system, being at a distance of ≃380 pc and mass ≃0.25 M⊙.

Virtualization of the Y.E.S. Congress 2009 Roundtable Symposia (Invited)

Science.gov (United States)

Gonzales, L. M.; Gaines, S. M.

2009-12-01

The Y.E.S. Congress 2009 was the first international conference organized by the Y.E.S. Network, an association of early-career geoscientists who represent professional societies, geoscience companies, geoscience departments, and interested policy makers from across the world, in collaboration with the International Year of Planet Earth (IYPE). The conference, hosted by the China University of Geosciences in Beijing, focused on scientific and career challenges faced by early-career geoscientists, with a particular emphasis on how the Y.E.S. Network can work collaboratively and internationally towards solving these challenges and furthering the IYPE motto of “Earth Sciences for Society”. A key features of the Y.E.S. Congress was the implementation of “virtualized” roundtable symposia which engaged senior and early-career geoscientists via presentations, panel discussions, and working group sessions in which strategies related to scientific challenges (i.e. climate change in the polar regions, natural hazards, natural resource sustainability) and academic and career pathway challenges (i.e. academic-industry linkages, gender parity in the geosciences, geoscience education sustainability, and international licensure issues) were developed. These strategies were then tasked to the Y.E.S. Network for further development and implementation. The virtualization of the roundtable symposia facilitated active discussion between those participants and speakers who were physically located at the conference facilities in Beijing with a wider international audience of virtual participants and speakers. This talk will address the key features of the roundtable virtualization, the successes and challenges faced during the pre-conference set-up as well as during the roundtable sessions, and potential future applications.

An introduction to planets ours and others : from Earth to exoplanets

CERN Document Server

Encrenaz, Thérèse

2014-01-01

What is a planet? The answer seems obvious, but nonetheless the definition of a planet has continuously evolved over the centuries, and their number has changed following successive discoveries. The decision endorsed by the International Astronomical Union to remove Pluto from the list of planets in 2006 well illustrates the difficulty associated with their definition. The recent discovery of hundreds of exoplanets around nearby stars of our Galaxy opens a new and spectacular dimension to astrophysics. We presently know very little about the physical nature of exoplanets. In contrast, our knowledge of Solar System planets has made huge progress over the past decades, thanks, especially, to space planetary exploration. The purpose of this book is first to characterize what planets are, in their global properties and in their diversity. Then, this knowledge is used to try to imagine the physical nature of exoplanets, starting from the few parameters we know about them. Throughout this book, as we explore the su...

Planets and Life

Science.gov (United States)

Sullivan, Woodruff T., III; Baross, John

2007-09-01

Foreword; Preface; Contributors; Prologue; Part I. History: 1. History of astrobiological ideas W. T. Sullivan and D. Carney; 2. From exobiology to astrobiology S. J. Dick; Part II. The Physical Stage: 3. Formation of Earth-like habitable planets D. E. Brownlee and M. Kress; 4. Planetary atmospheres and life D. Catling and J. F. Kasting; Part III. The Origin of Life on Earth: 5. Does 'life' have a definition? C.E. Cleland and C. F. Chyba; 6. Origin of life: crucial issues R. Shapiro; 7. Origin of proteins and nucleic acids A. Ricardo and S. A. Benner; 8. The roots of metabolism G.D. Cody and J. H. Scott; 9. Origin of cellular life D. W. Deamer; Part IV. Life on Earth: 10. Evolution: a defining feature of life J. A. Baross; 11. Evolution of metabolism and early microbial communities J. A. Leigh, D. A. Stahl and J. T. Staley; 12. The earliest records of life on Earth R. Buick; 13. The origin and diversification of eukaryotes M. L. Sogin, D. J. Patterson and A. McArthur; 14. Limits of carbon life on Earth and elsewhere J. A. Baross, J. Huber and M. Schrenk; 15. Life in ice J. W. Deming and H. Eicken; 16. The evolution and diversification of life S. Awramik and K. J. McNamara; 17. Mass extinctions P. D. Ward; Part V. Potentially Habitable Worlds: 18. Mars B. M. Jakosky, F. Westall and A. Brack; 19. Europa C. F. Chyba and C. B. Phillips; 20. Titan J. I. Lunine and B. Rizk; 21. Extrasolar planets P. Butler; Part VI. Searching for Extraterrestrial Life: 22. How to search for life on other worlds C. P. McKay; 23. Instruments and strategies for detecting extraterrestrial life P. G. Conrad; 24. Societial and ethical concerns M. S. Race; 25. Planetary protection J. D. Rummel; 26. Searching for extraterrestrial intelligence J. C. Tarter; 27. Alien biochemistries P. D. Ward and S. A. Benner; Part VII. Future of the Field: 28. Disciplinary and educational opportunities L. Wells, J. Armstrong and J. Huber; Epilogue C. F. Chyba; Appendixes: A. Units and usages; B. Planetary

A detailed view of Earth across space and time: our changing planet through a 32-year global Landsat and Sentinel-2 timelapse video

Science.gov (United States)

Herwig, C.

2017-12-01

The Landsat program offers an unparalleled record of our changing planet, with satellites that have been observing the Earth since 1972 to the present day. However, clouds, seasonal variation, and technical challenges around access to large volumes of data make it difficult for researchers and the public to understand global and regional scale changes across time through the planetary dataset. Earth Timelapse is a global, zoomable video that has helped revolutionize how users - millions of which have never been capable of utilizing Landsat data before - monitor and understand a changing planet. It is made from 33 cloud-free annual mosaics, one for each year from 1984 to 2016, which are made interactively explorable by Carnegie Mellon University CREATE Lab's Time Machine library, a technology for creating and viewing zoomable and pannable timelapses over space and time. Using Earth Engine, we combined over 5 million satellite images acquired over the past three decades by 5 different satellites. The majority of the images come from Landsat, a joint USGS/NASA Earth observation program that has observed the Earth since the 1970s. For 2015 and 2016, we combined Landsat 8 imagery with imagery from Sentinel-2A, part of the European Commission and European Space Agency's Copernicus Earth observation program. Along with the interactive desktop Timelapse application, we created a 200-video YouTube playlist highlighting areas across the world exhibiting change in the dataset.Earth Timelapse is an example that illustrates the power of Google Earth Engine's cloud-computing platform, which enables users such as scientists, researchers, and journalists to detect changes, map trends, and quantify differences on the Earth's surface using Google's computational infrastructure and the multi-petabyte Earth Engine data catalog. Earth Timelapse also highlights the value of data visualization to communicate with non-scientific audiences with varied technical and internet connectivity

Planet Detection: The Kepler Mission

Science.gov (United States)

Jenkins, Jon M.; Smith, Jeffrey C.; Tenenbaum, Peter; Twicken, Joseph D.; Van Cleve, Jeffrey

2012-03-01

The search for exoplanets is one of the hottest topics in astronomy and astrophysics in the twenty-first century, capturing the public's attention as well as that of the astronomical community. This nascent field was conceived in 1989 with the discovery of a candidate planetary companion to HD114762 [35] and was born in 1995 with the discovery of the first extrasolar planet 51 Peg-b [37] orbiting a main sequence star. As of March, 2011, over 500 exoplanets have been discovered* and 106 are known to transit or cross their host star, as viewed from Earth. Of these transiting planets, 15 have been announced by the Kepler Mission, which was launched into an Earth-trailing, heliocentric orbit in March, 2009 [1,4,6,15,18,20,22,31,32,34,36,43]. In addition, over 1200 candidate transiting planets have already been detected by Kepler [5], and vigorous follow-up observations are being conducted to vet these candidates. As the false-positive rate for Kepler is expected to be quite low [39], Kepler has effectively tripled the number of known exoplanets. Moreover, Kepler will provide an unprecedented data set in terms of photometric precision, duration, contiguity, and number of stars. Kepler's primary science objective is to determine the frequency of Earth-size planets transiting their Sun-like host stars in the habitable zone, that range of orbital distances for which liquid water would pool on the surface of a terrestrial planet such as Earth, Mars, or Venus. This daunting task demands an instrument capable of measuring the light output from each of over 100,000 stars simultaneously with an unprecedented photometric precision of 20 parts per million (ppm) at 6.5-h intervals. The large number of stars is required because the probability of the geometrical alignment of planetary orbits that permit observation of transits is the ratio of the size of the star to the size of the planetary orbit. For Earth-like planets in 1-astronomical unit (AU) orbits† about sun-like stars

In search of future earths: assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes.

Science.gov (United States)

O'Malley-James, Jack T; Greaves, Jane S; Raven, John A; Cockell, Charles S

2015-05-01

Earth will become uninhabitable within 2-3 Gyr as a result of the increasing luminosity of the Sun changing the boundaries of the habitable zone (HZ). Predictions about the future of habitable conditions on Earth include declining species diversity and habitat extent, ocean loss, and changes to geochemical cycles. Testing these predictions is difficult, but the discovery of a planet that is an analogue to future Earth could provide the means to test them. This planet would need to have an Earth-like biosphere history and to be approaching the inner edge of the HZ at present. Here, we assess the possibility of finding such a planet and discuss the benefits of analyzing older Earths. Finding an old-Earth analogue in nearby star systems would be ideal, because this would allow for atmospheric characterization. Hence, as an illustrative example, G stars within 10 pc of the Sun are assessed as potential old-Earth-analog hosts. Six of these represent good potential hosts. For each system, a hypothetical Earth analogue is placed at locations within the continuously habitable zone (CHZ) that would allow enough time for Earth-like biosphere development. Surface temperature evolution over the host star's main sequence lifetime (assessed by using a simple climate model) is used to determine whether the planet would be in the right stage of its late-habitable lifetime to exhibit detectable biosignatures. The best candidate, in terms of the chances of planet formation in the CHZ and of biosignature detection, is 61 Virginis. However, planet formation studies suggest that only a small fraction (0.36%) of G stars in the solar neighborhood could host an old-Earth analogue. If the development of Earth-like biospheres is rare, requiring a sequence of low-probability events to occur, biosphere evolution models suggest they are rarer still, with only thousands being present in the Galaxy as a whole.

ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS

International Nuclear Information System (INIS)

Wordsworth, Robin; Pierrehumbert, Raymond

2014-01-01

Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is an atmosphere where oxygen is a major constituent. Here we show that lifeless habitable zone terrestrial planets around any star type may develop oxygen-dominated atmospheres as a result of water photolysis, because the cold trap mechanism that protects H 2 O on Earth is ineffective when the atmospheric inventory of non-condensing gases (e.g., N 2 , Ar) is low. Hence the spectral features of O 2 and O 3 alone cannot be regarded as robust signs of extraterrestrial life

Impact on the earth, ocean and atmosphere

International Nuclear Information System (INIS)

Ahrens, T.J.; O'Keefe, J.D.

1987-01-01

Several hundred impact craters produced historically and at times as early as 1.9 x 10/sup 9/ years ago with diameters in the range 10/sup -2/ to 10/sup 2/ km are observed on the surface of the earth. Earth-based and spacecraft observations of the surfaces of all the terrestrial planets and their satellites, as well as many of the icy satellites of the outer planets, indicated that impact cratering was a dominant process on planetary surfaces during the early history of the solar system. Moreover, the recent observation of a circumstellar disk around the nearby star, β-Pictoris, appears to be similar to the authors' own hypothesized protosolar disk. A disk of material around our sun has been hypothesized to have been the source of the solid planetesimals from which the earth and the other planets accreted by infall and capture. Thus it appears that the earth and the other terrestrial planets formed as a result of infall and impact of planetesimals. Although the present planets grew rapidly via accretion to their present size (in --10/sup 7/ years), meteorite impacts continue to occur on the earth and other planets. Until recently meteorite impact has been considered to be a process that was important on the earth and the other planets only early in the history of the solar system. This is no longer true. The Alvarez hypothesis suggests that the extinction of some 90% of all species, including 17 classes of dinosaurs, is associated with the 1 to 150 cm thick layer of noble-element rich dust which is found all over the earth exactly at the Cretaceous-Tertiary boundary. The enrichment of noble elements in this dust is in meteorite-like proportions. This dust is thought to represent the fine impact ejecta from a --10 km diameter asteroid interacting with the solid earth. The Alvarez hypothesis associates the extinction with the physics of a giant impact on the earth

Migration of accreting giant planets

Science.gov (United States)

Crida, A.; Bitsch, B.; Raibaldi, A.

2016-12-01

We present the results of 2D hydro simulations of giant planets in proto-planetary discs, which accrete gas at a more or less high rate. First, starting from a solid core of 20 Earth masses, we show that as soon as the runaway accretion of gas turns on, the planet is saved from type I migration : the gap opening mass is reached before the planet is lost into its host star. Furthermore, gas accretion helps opening the gap in low mass discs. Consequently, if the accretion rate is limited to the disc supply, then the planet is already inside a gap and in type II migration. We further show that the type II migration of a Jupiter mass planet actually depends on its accretion rate. Only when the accretion is high do we retrieve the classical picture where no gas crosses the gap and the planet follows the disc spreading. These results impact our understanding of planet migration and planet population synthesis models. The e-poster presenting these results in French can be found here: L'e-poster présentant ces résultats en français est disponible à cette adresse: http://sf2a.eu/semaine-sf2a/2016/posterpdfs/156_179_49.pdf.

Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1.

Science.gov (United States)

Gillon, Michaël; Triaud, Amaury H M J; Demory, Brice-Olivier; Jehin, Emmanuël; Agol, Eric; Deck, Katherine M; Lederer, Susan M; de Wit, Julien; Burdanov, Artem; Ingalls, James G; Bolmont, Emeline; Leconte, Jeremy; Raymond, Sean N; Selsis, Franck; Turbet, Martin; Barkaoui, Khalid; Burgasser, Adam; Burleigh, Matthew R; Carey, Sean J; Chaushev, Aleksander; Copperwheat, Chris M; Delrez, Laetitia; Fernandes, Catarina S; Holdsworth, Daniel L; Kotze, Enrico J; Van Grootel, Valérie; Almleaky, Yaseen; Benkhaldoun, Zouhair; Magain, Pierre; Queloz, Didier

2017-02-22

One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star-named TRAPPIST-1-makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.

H-atmospheres of Icy Super-Earths Formed In Situ in the Outer Solar System: An Application to a Possible Planet Nine

Science.gov (United States)

Levi, A.; Kenyon, S. J.; Podolak, M.; Prialnik, D.

2017-04-01

We examine the possibility that icy super-Earth mass planets, formed over long timescales (0.1-1 Gyr) at large distances (˜200-1000 au) from their host stars, will develop massive H-rich atmospheres. Within the interior of these planets, high pressure converts CH4 into ethane, butane, or diamond and releases H2. Using simplified models that capture the basic physics of the internal structure, we show that the physical properties of the atmosphere depend on the outflux of H2 from the mantle. When this outflux is ≲ {10}10 molec cm-2 s-1, the outgassed atmosphere has a base pressure of ≲1 bar. Larger outflows result in a substantial atmosphere where the base pressure may approach 103-104 bar. For any pressure, the mean density of these planets, 2.4-3 g cm-3, is much larger than the mean density of Uranus and Neptune, 1.3-1.6 g cm-3. Thus, observations can distinguish between a Planet Nine with a primordial H/He-rich atmosphere accreted from the protosolar nebula and one with an atmosphere outgassed from the core.

THE NASA-UC ETA-EARTH PROGRAM. I. A SUPER-EARTH ORBITING HD 7924

International Nuclear Information System (INIS)

Howard, Andrew W.; Marcy, Geoffrey W.; Johnson, John Asher; Fischer, Debra A.; Giguere, Matthew J.; Isaacson, Howard; Wright, Jason T.; Henry, Gregory W.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.

2009-01-01

We report the discovery of the first low-mass planet to emerge from the NASA-UC Eta-Earth Program, a super-Earth orbiting the K0 dwarf HD 7924. Keplerian modeling of precise Doppler radial velocities reveals a planet with minimum mass M P sin i = 9.26 M + in a P = 5.398 d orbit. Based on Keck-HIRES measurements from 2001 to 2008, the planet is robustly detected with an estimated false alarm probability of less than 0.001. Photometric observations using the Automated Photometric Telescopes at Fairborn Observatory show that HD 7924 is photometrically constant over the radial velocity period to 0.19 mmag, supporting the existence of the planetary companion. No transits were detected down to a photometric limit of ∼0.5 mmag, eliminating transiting planets with a variety of compositions. HD 7924b is one of only eight planets detected by the radial velocity technique with M P sin i + and as such is a member of an emerging family of low-mass planets that together constrain theories of planet formation.

Secondary components, integral multiplicity factor and coupling coefficients of cosmic rays in the Earth atmosphere and other planets

International Nuclear Information System (INIS)

Dorman, L.I.; Yanke, V.G.

1979-01-01

Integral multiples of cosmic rays in Earth and other planets atmospheres have been determined. Kinetic equations describing the evolution of hadronic cascade in atmosphere using modern accelerating data have been solved with that end in view. Bond coefficients for nucleonic, muonic and electronic components of secondary cosmic radiation have been built using integral multiples. Normalized bond coefficients for three components obtained for maximum solar activity are presented. Integral muon and nucleon generation and bond coefficients have also been given for Mars

The earth planet as a repository of life: a common planet or a rarity in the universe?

International Nuclear Information System (INIS)

Portilla, Jose Gregorio

2011-01-01

Life is based on elements that have their origins within the centers of stars. Then organic molecules are formed in the interstellar medium. They can make part of planets some of them appropriate for the origin and prosperity of life. Extra solar planets are currently discovered and observed by astronomers and are abundant, but extraterrestrial life or at least complex life

Habitability of planets around red dwarf stars.

Science.gov (United States)

Heath, M J; Doyle, L R; Joshi, M M; Haberle, R M

1999-08-01

Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible.

Why Earth Science?

Science.gov (United States)

Smith, Michael J.

2004-01-01

This article briefly describes Earth science. The study of Earth science provides the foundation for an understanding of the Earth, its processes, its resources, and its environment. Earth science is the study of the planet in its entirety, how its lithosphere, atmosphere, hydrosphere, and biosphere work together as systems and how they affect…

Primary school children and teachers discover the nature and science of planet Earth and Mars

Science.gov (United States)

Kleinhans, Maarten; Verkade, Alex; Bastings, Mirjam; Reichwein, Maarten

2016-04-01

For various reasons primary schools emphasise language and calculus rather than natural sciences. When science is taught at all, examination systems often favour technological tricks and knowledge of the 'right' answer over the process of investigation and logical reasoning towards that answer. Over the long term, this is not conducive to curiosity and scientific attitude in large parts of the population. Since the problem is more serious in primary than in secondary education, and as children start their school career with a natural curiosity and great energy to explore their world, we focus our efforts on primary school teachers in close collaboration with teachers and researchers. Our objective was to spark children's curiosity and their motivation to learn and discover, as well as to help teachers develop self-afficacy in science education. To this end we developed a three-step program with a classroom game and sand-box experiments related to planet Earth and Mars. The classroom game Expedition Mundus simulates science in its focus on asking questions, reasoning towards answers on the basis of multiple sources and collaboration as well as growth of knowledge. Planet Mundus is entirely fictitional to avoid differences in foreknowledge between pupils. The game was tested in hundreds of classes in primary schools and the first years of secondary education and was printed (in Dutch) and distributed over thousands of schools as part of teacher education through university science hubs. Expedition Mundus was developed by the Young Academy of the Royal Netherlands Academy of Arts and Sciences and De Praktijk. The tested translations in English and German are available on http://www.expeditionmundus.org. Following the classroom game, we conducted simple landscape experiments in sand boxes supported by google earth imagery of real rivers, fans and deltas on Earth and Mars. This was loosely based on our fluvial morphodynamics research. This, in the presence of a

On the existence of another source of heat production for the earth and planets, and its connection with gravitomagnetism.

Science.gov (United States)

Elbeze, Alexandre Chaloum

2013-01-01

Recent revised estimates of the Earth's surface heat flux are in the order of 47 TW. Given that its internal radiogenic (mantle and crust) heat production is estimated to be around 20 TW, the Earth has a thermal deficit of around 27 TW. This article will try to show that the action of the gravitational field of the Sun on the rotating masses of the Earth is probably the source of another heat production in order of 54TW, which would satisfy the thermal balance of our celestial body and probably explain the reduced heat flow Qo. We reach this conclusion within the framework of gravitation implied by Einstein's special and general relativity theory (SR, GR). Our results show that it might possible, in principle, to calculate the heat generated by the action of the gravitational field of celestial bodies on the Earth and planets of the Solar System (a phenomenon that is different to that of the gravitational tidal effect from the Sun and the Moon). This result should help physicists to improve and develop new models of the Earth's heat balance, and suggests that contrary to cooling, the Earth is in a phase of thermal balance, or even reheating.

Atmospheres of the terrestrial planets

International Nuclear Information System (INIS)

Kivelson, M.G.; Schubert, G.

1986-01-01

Properties of the planets are identified - such as size, spin rate, and distance from the sun - that are important in understanding the characteristics of their atmospheres. Venus, earth and Mars have surface-temperature differences only partly explained by the decrease of solar radiation flux with distance from the sun. More significant effects arise from the variations in the degree to which the atmospheres act as absorbers of planetary thermal reradiation. Atmospheric circulation on a global scale also varies markedly among the three planets. 5 references

The Threatening Magnetic and Plasma Environment of the TRAPPIST-1 Planets

Energy Technology Data Exchange (ETDEWEB)

Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer; Alvarado-Gómez, Julian D.; Moschou, Sofia P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2017-07-10

Recently, four additional Earth-mass planets were discovered orbiting the nearby ultracool M8 dwarf, TRAPPIST-1, making a remarkable total of seven planets with equilibrium temperatures compatible with the presence of liquid water on their surface. Temperate terrestrial planets around an M-dwarf orbit close to their parent star, rendering their atmospheres vulnerable to erosion by the stellar wind and energetic electromagnetic and particle radiation. Here, we use state-of-the-art 3D magnetohydrodynamic models to simulate the wind around TRAPPIST-1 and study the conditions at each planetary orbit. All planets experience a stellar wind pressure between 10{sup 3} and 10{sup 5} times the solar wind pressure on Earth. All orbits pass through wind pressure changes of an order of magnitude and most planets spend a large fraction of their orbital period in the sub-Alfvénic regime. For plausible planetary magnetic field strengths, all magnetospheres are greatly compressed and undergo much more dynamic change than that of the Earth. The planetary magnetic fields connect with the stellar radial field over much of the planetary surface, allowing the direct flow of stellar wind particles onto the planetary atmosphere. These conditions could result in strong atmospheric stripping and evaporation and should be taken into account for any realistic assessment of the evolution and habitability of the TRAPPIST-1 planets.

THE SYNERGY OF DIRECT IMAGING AND ASTROMETRY FOR ORBIT DETERMINATION OF EXO-EARTHS

International Nuclear Information System (INIS)

Shao, Michael; Catanzarite, Joseph; Pan Xiaopei

2010-01-01

The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone (HZ) around a nearby star. Mass is one of the most important characteristics of a planet and can only be measured by observing the motion of the star around the planet-star center of gravity. The planet's orbit can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exoplanet's orbit by direct imaging is complicated by a number of factors. One is the inner working angle (IWA). A space coronagraph or interferometer imaging an exo-Earth can separate the light from the planet from the light from the star only when the star-planet separation is larger than the IWA. Second, the apparent brightness of a planet depends on the orbital phase. A single image of a planet cannot tell us whether the planet is in the HZ or distinguish whether it is an exo-Earth or a Neptune-mass planet. Third is the confusion that may arise from the presence of multiple planets. With two images of a multiple planet system, it is not possible to assign a dot to a planet based only on the photometry and color of the planet. Finally, the planet-star contrast must exceed a certain minimum value in order for the planet to be detected. The planet may be unobservable even when it is outside the IWA, such as when the bright side of the planet is facing away from us in a 'crescent' phase. In this paper we address the question: 'Can a prior astrometric mission that can identify which stars have Earth-like planets significantly improve the science yield of a mission to image exo-Earths?' In the case of the Occulting Ozone Observatory, a small external occulter mission that cannot measure spectra, we find that the occulter mission could confirm the orbits of ∼4 to ∼5 times as many exo-Earths if an astrometric mission preceded it to identify which stars had such planets. In the case of an

Giant Planets: Good Neighbors for Habitable Worlds?

Science.gov (United States)

Georgakarakos, Nikolaos; Eggl, Siegfried; Dobbs-Dixon, Ian

2018-04-01

The presence of giant planets influences potentially habitable worlds in numerous ways. Massive celestial neighbors can facilitate the formation of planetary cores and modify the influx of asteroids and comets toward Earth analogs later on. Furthermore, giant planets can indirectly change the climate of terrestrial worlds by gravitationally altering their orbits. Investigating 147 well-characterized exoplanetary systems known to date that host a main-sequence star and a giant planet, we show that the presence of “giant neighbors” can reduce a terrestrial planet’s chances to remain habitable, even if both planets have stable orbits. In a small fraction of systems, however, giant planets slightly increase the extent of habitable zones provided that the terrestrial world has a high climate inertia. In providing constraints on where giant planets cease to affect the habitable zone size in a detrimental fashion, we identify prime targets in the search for habitable worlds.

Observations at the planet Mercury by the plasma electron experiment, Mariner 10

Science.gov (United States)

Ogilvie, K. W.; Scudder, J. D.; Vasyliunas, V. M.; Hartle, R. E.; Siscoe, G. L.

1976-01-01

Plasma electron observations made onboard Mariner 10 are reported. Three encounters with the planet Mercury show that the planet interacts with the solar wind to form a bow shock and a permanent magnetosphere. The observations provide a determination of the dimensions and properties of the magnetosphere, independently of and in general agreement with magnetometer observations. The magnetosphere of Mercury appears to be similar in shape to that of the Earth but much smaller in relation to the size of the planet. Electron populations similar to those found in the Earth's magnetotail, within the plasma sheet and adjacent regions, were observed at Mercury; both their spatial location and the electron energy spectra within them bear qualitative and quantitative resemblance to corresponding observations at the Earth. The magnetosphere of Mercury resembles to a marked degree a reduced version of that of the Earth, with no significant differences of structure.

Observations at the planet Mercury by the plasma electron experiment, Mariner 10

International Nuclear Information System (INIS)

Ogilvie, K.W.; Scudder, J.D.; Vasyliunas, V.M.; Hartle, R.E.; Siscoe, G.L.

1976-09-01

Plasma electron observations made onboard Mariner 10 are reported. Three encounters with the planet Mercury show that the planet interacts with the solar wind to form a bow shock and a permanent magnetosphere. The observations provide a determination of the dimensions and properties of the magnetosphere, independently of and in general agreement with magnetometer observations. The magnetosphere of Mercury appears to be similar in shape to that of the Earth but much smaller in relation to the size of the planet. Electron populations similar to those found in the Earth's magnetotail, within the plasma sheet and adjacent regions, were observed at Mercury; both their spatial location and the electron energy spectra within them bear qualitative and quantitative resemblance to corresponding observations at the Earth. The magnetosphere of Mercury resembles to a marked degree a reduced version of that of the Earth, with no significant differences of structure

Building a Dashboard of the Planet with Google Earth and Earth Engine

Science.gov (United States)

Moore, R. T.; Hancher, M.

2016-12-01

In 2005 Google Earth, a popular 3-D virtual globe, was first released. Scientists immediately recognized how it could be used to tell stories about the Earth. From 2006 to 2009, the "Virtual Globes" sessions of AGU included innovative examples of scientists and educators using Google Earth, and since that time it has become a commonplace tool for communicating scientific results. In 2009 Google Earth Engine, a cloud-based platform for planetary-scale geospatial analysis, was first announced. Earth Engine was initially used to extract information about the world's forests from raw Landsat data. Since then, the platform has proven highly effective for general analysis of georeferenced data, and users have expanded the list of use cases to include high-impact societal issues such as conservation, drought, disease, food security, water management, climate change and environmental monitoring. To support these use cases, the platform has continuously evolved with new datasets, analysis functions, and user interface tools. This talk will give an overview of the latest Google Earth and Earth Engine functionality that allow partners to understand, monitor and tell stories about of our living, breathing Earth. https://earth.google.com https://earthengine.google.com

Predictions of Planet Detections with Near-infrared Radial Velocities in the Upcoming SPIRou Legacy Survey-planet Search

Science.gov (United States)

Cloutier, Ryan; Artigau, Étienne; Delfosse, Xavier; Malo, Lison; Moutou, Claire; Doyon, René; Donati, Jean-Francois; Cumming, Andrew; Dumusque, Xavier; Hébrard, Élodie; Menou, Kristen

2018-02-01

The SPIRou near-infrared spectropolarimeter is destined to begin science operations at the Canada–France–Hawaii Telescope in mid-2018. One of the instrument’s primary science goals is to discover the closest exoplanets to the solar system by conducting a three- to five-year long radial velocity survey of nearby M dwarfs at an expected precision of ∼1 m s‑1, the SPIRou Legacy Survey-Planet Search (SLS-PS). In this study, we conduct a detailed Monte Carlo simulation of the SLS-PS using our current understanding of the occurrence rate of M dwarf planetary systems and physical models of stellar activity. From simultaneous modeling of planetary signals and activity, we predict the population of planets to be detected in the SLS-PS. With our fiducial survey strategy and expected instrument performance over a nominal survey length of ∼3 years, we expect SPIRou to detect {85.3}-12.4+29.3 planets including {20.0}-7.2+16.8 habitable-zone planets and {8.1}-3.2+7.6 Earth-like planets from a sample of 100 M1–M8.5 dwarfs out to 11 pc. By studying mid-to-late M dwarfs previously inaccessible to existing optical velocimeters, SPIRou will put meaningful constraints on the occurrence rate of planets around those stars including the value of {η }\\oplus at an expected level of precision of ≲ 45 % . We also predict that a subset of {46.7}-6.0+16.0 planets may be accessible with dedicated high-contrast imagers on the next generation of extremely large telescopes including {4.9}-2.0+4.7 potentially imagable Earth-like planets. Lastly, we compare the results of our fiducial survey strategy to other foreseeable survey versions to quantify which strategy is optimized to reach the SLS-PS science goals. The results of our simulations are made available to the community on GitHub (https://github.com/r-cloutier/SLSPS_Simulations).

Stars Influence on the Earth in Maya Culture: Stars and Planets in Maya Culture

Directory of Open Access Journals (Sweden)

Emanuel George Oprea

2015-11-01

Full Text Available The Mesoamerican Culture of Maya’s was one of the ancient and advanced cultures of the American continent and they influenced other Amerindian peoples. The life of Maya people, of the Earth itself and of the Universe is set and constructed around Maya Calendar and has a cyclic character as a direct influence of the stars. Many centuries the Western civilization with the its linear Calendar had not accepted the ideas of the possible influence of the stars and planets to peoples lives. The end of the last century and the beginning of XXI’s had started to demonstrate the opposite. The present work tries to show the process of meeting and intersection of the ancient ideas of Maya civilization and some of new ideas from the modern sciences.

The "Week Of Planet Earth" Italy Discovering Geosciences: a More Informed Society is a More Engaged Society.

Science.gov (United States)

Seno, S.; Coccioni, R.

2016-12-01

The "Week of Planet Earth" (www.settimanaterra.org) is a science festival that involves the whole of the Italian Regions: founded in 2012, it has become the largest event of Italian Geosciences and one of the biggest European science festivals. During a week in October several locations distributed throughout the Country are animated by events, called "Geoeventi", to disseminate geosciences to the masses and deliver science education by means of a wide range of activities: hiking, walking in city and town centers, open-door at museums and research centers, guided tours, exhibitions, educational and experimental workshops for children and young people, music and art performances, food and wine events, lectures, conferences, round tables. Universities and colleges, research centers, local Authorities, cultural and scientific associations, parks and museums, professionals organize the Geoeventi. The festival aims at bringing adults and young people to Geosciences, conveying enthusiasm for scientific research and discoveries, promoting sustainable cultural tourism, aware of environmental values and distributed all over Italy. The Geoeventi shed light both on the most spectacular and on the less known geological sites, which are often a stone's throw from home. The Week of Planet Earth is growing year after year: the 2016 edition proposes 310 Geoeventi, 70 more than in 2015. The number of places involved in the project also increased and rose from 180 in 2015 to 230 in 2016. This initiative, that is also becoming a significant economic driver for many small companies active in the field of science divulgation, is analyzed, evaluated and put in a transnational network perspective.

Sensing Planet Earth - Chalmers' MOOCs on Earth observation

Science.gov (United States)

Hobiger, Thomas; Stöhr, Christian; Murtagh, Donal; Forkman, Peter; Galle, Bo; Mellquist, Johan; Soja, Maciej; Berg, Anders; Carvajal, Gisela; Eriksson, Leif; Haas, Rüdiger

2016-04-01

An increasing number of universities around the globe produce and conduct Massive Open Online Courses (MOOCs). In the beginning of 2016, Chalmers University of Technology ran two MOOCs on the topic of Earth observations on the edX platform. Both four week long courses were at introductory level and covered topics related to solid Earth, atmosphere, biosphere, hydrosphere and cryosphere. It was discussed how one can measure and trace global change and use remote sensing tools for disaster monitoring. Research has attempted to assess the learners' motivations to participate in MOOCs, but there is a need for further case studies about motivations, opportunities and challenges for teachers engaging in MOOC development. In our presentation, we are going to report about the experiences gained from both the MOOC production and the actual course run from the instructors' perspective. After brief introduction to MOOCs in general and at Chalmers in particular, we share experiences and challenges of developing lecture and assessment material, the video production and coordination efforts between and within different actors involved in the production process. Further, we reflect upon the actual run of the course including course statistics and feedback from the learners. We discuss issues such as learner activation and engagement with the material, teacher-learner and student-student interaction as well as the scalability of different learning activities. Finally, we will present our lessons-learned and conclusions on the applicability of MOOCs in the field of Earth science teaching.

Views from EPOXI: Colors in Our Solar System as an Analog for Extrasolar Planets

Science.gov (United States)

Crow, Carolyn A.; McFadden, L. A.; Robinson, T.; Meadows, V. S.; Livengood, T. A.; Hewagama, T.; Barry, R. K.; Deming, L. D.; Lisse, C. M.; Wellnitz, Dennis

2011-01-01

The first visible-light studies of Earth-sized extrasolar planets will employ photometry or low-resolution spectroscopy. This work uses EPOCh medium-hand filter photometry between 150 and 950 nm obtained with the Deep Impact (DI) High Resolution Instrument (HRI) of Earth, the Moon, and Mars in addition to previous full-disk observations of the other six solar system planets and Titan to analyze the limitations of using photometric colors to characterize extrasolar planets. We determined that the HRI 350, 550, and 850 nm filters are optimal for distinguishing Earth from the other planets and separating planets to first order based on their atmospheric and surface properties. Detailed conclusions that can be drawn about exoplanet atmospheres simply from a color-color plot are limited due to potentially competing physical processes in the atmosphere. The presence of a Rayleigh scattering atmosphere can be detected by an increase in the 350-550 nm brightness ratio, but the absence of Rayleigh scattering cannot be confirmed due to the existence of atmospheric and surface absorbing species in the UV. Methane and ammonia are the only species responsible for strong absorption in the 850 nm filter in our solar system. The combination of physical processes present on extrasolar planets may differ from those we see locally. Nevertheless, a generation of telescopes capable of collecting such photometric observations can serve a critical role in first-order characterization and constraining the population of Earth-like extrasolar planets.

Stellar variability and its implications for photometric planet detection with Kepler

Science.gov (United States)

Batalha, N. M.; Jenkins, J.; Basri, G. S.; Borucki, W. J.; Koch, D. G.

2002-01-01

Kepler is one of three candidates for the next NASA Discovery Mission and will survey the extended solar neighborhood to detect and characterize hundreds of terrestrial (and larger) planets in or near the habitable zone. Its strength lies in its ability to detect large numbers of Earth-sized planets - planets which produced a 10-4 change in relative stellar brightness during a transit across the disk of a sun-like parent star. Such a detection requires high instrumental relative precision and is facilitated by observing stars which are photometrically quiet on hourly timescales. Probing stellar variability across the HR diagram, one finds that many of the photometrically quietest stars are the F and G dwarfs. The Hipparcos photometric database shows the lowest photometric variances among stars of this spectral class. Our own Sun is a prime example with RMS variations over a few rotational cycles of typically (3 - 4)×10-4 (computed from VIRGO/DIARAD data taken Jan-Mar 2001). And variability on the hourly time scales crucial for planet detection is significantly smaller: just (2 - 5)×10-5. This bodes well for planet detection programs such as Kepler and Eddington. With significant numbers of photometrically quiet solar-type stars, Earth-sized planets should be readily identified provided they are abundant in the solar neighborhood. In support of the Kepler science objectives, we have initiated a study of stellar variability and its implications for planet detection. Herein, we summarize existing observational and theoretrical work with the objective of determining the percentage of stars in the Kepler field of view expected to be photometrically stable at a level which allows for Earth-sized planet detection.

The HARPS-N Rocky Planet Search

DEFF Research Database (Denmark)

Motalebi, F.; Udry, S.; Gillon, M.

2015-01-01

We know now from radial velocity surveys and transit space missions that planets only a few times more massive than our Earth are frequent around solar-type stars. Fundamental questions about their formation history, physical properties, internal structure, and atmosphere composition are, however......, still to be solved. We present here the detection of a system of four low-mass planets around the bright (V = 5.5) and close-by (6.5 pc) star HD 219134. This is the first result of the Rocky Planet Search programme with HARPS-N on the Telescopio Nazionale Galileo in La Palma. The inner planet orbits...... on a close-in, quasi-circular orbit with a period of 6.767 ± 0.004 days. The third planet in the system has a period of 46.66 ± 0.08 days and a minimum-mass of 8.94 ± 1.13 M⊕, at 0.233 ± 0.002 AU from the star. Its eccentricity is 0.46 ± 0.11. The period of this planet is close to the rotational period...

TWO SMALL PLANETS TRANSITING HD 3167

International Nuclear Information System (INIS)

Vanderburg, Andrew; Bieryla, Allyson; Latham, David W.; Mayo, Andrew W.; Berlind, Perry; Duev, Dmitry A.; Jensen-Clem, Rebecca; Kulkarni, Shrinivas; Riddle, Reed; Baranec, Christoph; Law, Nicholas M.; Nieberding, Megan N.; Salama, Maïssa

2016-01-01

We report the discovery of two super-Earth-sized planets transiting the bright (V = 8.94, K = 7.07) nearby late G-dwarf HD 3167, using data collected by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6 R ⊕ and an ultra-short orbital period of only 0.96 days. The outer planet, HD 3167 c, has a radius of 2.9 R ⊕ and orbits its host star every 29.85 days. At a distance of just 45.8 ± 2.2 pc, HD 3167 is one of the closest and brightest stars hosting multiple transiting planets, making HD 3167 b and c well suited for follow-up observations. The star is chromospherically inactive with low rotational line-broadening, ideal for radial velocity observations to measure the planets’ masses. The outer planet is large enough that it likely has a thick gaseous envelope that could be studied via transmission spectroscopy. Planets transiting bright, nearby stars like HD 3167 are valuable objects to study leading up to the launch of the James Webb Space Telescope .

Migration of planetesimals during last stages of giant planet accumulation

International Nuclear Information System (INIS)

Ipatov, S.I.

1989-01-01

The migration and accumulation of bodies from the giant planet's feeding zones are investigated after the main part of mass of these planets had been formed. These investigations are based on the computer simulation results for the evolving spatial disks which initially consisted of a few almost formed planets and hundreds of identical bodies in Uranus and Neptune zone. It is shown that the total mass of bodies penetrated in the asteroid zone from the giant planet zones could be ten times as large as the Earth mass. The beyond-Neptune belt could form during accumulation of the giant planets. Evolution of the planet orbits under encounters of planets with planetesimals is investigated

Migration-driven diversity of super-Earth compositions

Science.gov (United States)

Raymond, Sean N.; Boulet, Thibault; Izidoro, Andre; Esteves, Leandro; Bitsch, Bertram

2018-06-01

A leading model for the origin of super-Earths proposes that planetary embryos migrate inward and pile up on close-in orbits. As large embryos are thought to preferentially form beyond the snow line, this naively predicts that most super-Earths should be very water-rich. Here we show that the shortest-period planets formed in the migration model are often purely rocky. The inward migration of icy embryos through the terrestrial zone accelerates the growth of rocky planets via resonant shepherding. We illustrate this process with a simulation that provided a match to the Kepler-36 system of two planets on close orbits with very different densities. In the simulation, two super-Earths formed in a Kepler-36-like configuration; the inner planet was pure rock while the outer one was ice-rich. We conclude from a suite of simulations that the feeding zones of close-in super-Earths are likely to be broad and disconnected from their final orbital radii.

Detecting Water on Super-Earths Using JAVST

Science.gov (United States)

Deming, D.

2010-01-01

Nearby lower train sequence stars host a class of planets known as Super-Earths, that have no analog in our own solar system. Super-Earths are rocky and/or icy planets with masses up to about 10 Earth masses, They are expected to host atmospheres generated by a number of processes including accretion of chondritic material. Water vapor should be a common constituent of super-Earth atmospheres, and may be detectable in transiting super-Earths using transmission spectroscopy during primar y eclipse, and emission spectroscopy at secondary eclipse. I will discuss the prospects for super-Earth atmospheric measurements using JWST.

A probabilistic approach towards understanding how planet composition affects plate tectonics - through time and space.

Science.gov (United States)

Stamenkovic, V.

2017-12-01

We focus on the connections between plate tectonics and planet composition — by studying how plate yielding is affected by surface and mantle water, and by variable amounts of Fe, SiC, or radiogenic heat sources within the planet interior. We especially explore whether we can make any robust conclusions if we account for variable initial conditions, current uncertainties in model parameters and the pressure dependence of the viscosity, as well as uncertainties on how a variable composition affects mantle rheology, melting temperatures, and thermal conductivities. We use a 1D thermal evolution model to explore with more than 200,000 simulations the robustness of our results and use our previous results from 3D calculations to help determine the most likely scenario within the uncertainties we still face today. The results that are robust in spite of all uncertainties are that iron-rich mantle rock seems to reduce the efficiency of plate yielding occurring on silicate planets like the Earth if those planets formed along or above mantle solidus and that carbon planets do not seem to be ideal candidates for plate tectonics because of slower creep rates and generally higher thermal conductivities for SiC. All other conclusions depend on not yet sufficiently constrained parameters. For the most likely case based on our current understanding, we find that, within our range of varied planet conditions (1-10 Earth masses), planets with the greatest efficiency of plate yielding are silicate rocky planets of 1 Earth mass with large metallic cores (average density 5500-7000 kg m-3) with minimal mantle concentrations of iron (as little as 0% is preferred) and radiogenic isotopes at formation (up to 10 times less than Earth's initial abundance; less heat sources do not mean no heat sources). Based on current planet formation scenarios and observations of stellar abundances across the Galaxy as well as models of the evolution of the interstellar medium, such planets are

Infrared radiation from an extrasolar planet.

Science.gov (United States)

Deming, Drake; Seager, Sara; Richardson, L Jeremy; Harrington, Joseph

2005-04-07

A class of extrasolar giant planets--the so-called 'hot Jupiters' (ref. 1)--orbit within 0.05 au of their primary stars (1 au is the Sun-Earth distance). These planets should be hot and so emit detectable infrared radiation. The planet HD 209458b (refs 3, 4) is an ideal candidate for the detection and characterization of this infrared light because it is eclipsed by the star. This planet has an anomalously large radius (1.35 times that of Jupiter), which may be the result of ongoing tidal dissipation, but this explanation requires a non-zero orbital eccentricity (approximately 0.03; refs 6, 7), maintained by interaction with a hypothetical second planet. Here we report detection of infrared (24 microm) radiation from HD 209458b, by observing the decrement in flux during secondary eclipse, when the planet passes behind the star. The planet's 24-microm flux is 55 +/- 10 microJy (1sigma), with a brightness temperature of 1,130 +/- 150 K, confirming the predicted heating by stellar irradiation. The secondary eclipse occurs at the midpoint between transits of the planet in front of the star (to within +/- 7 min, 1sigma), which means that a dynamically significant orbital eccentricity is unlikely.

The Kepler Mission: A Search for Terrestrial Planets - Development Status

Science.gov (United States)

Koch, David; Borucki, W.; Mayer, D.; Caldwell, D.; Jenkens, J.; Dunham, E.; Geary, J.; Bachtell, E.; Deininger, W.; Philbrick, R.

2003-01-01

We have embarked on a mission to detect terrestrial planets. The space mission has been optimized to search for earth-size planets (0.5 to 10 earth masses) in the habitable zone (HZ) of solar-like stars. Given this design, the mission will necessarily be capable of not only detecting Earth analogs, but a wide range of planetary types and characteristics ranging from Mercury-size objects with orbital periods of days to gas-giants in decade long orbits that have undeniable signatures even with only one transit detected. The mission is designed to survey the full range of spectral-type dwarf stars. The approach is to detect the periodic signal of transiting planets. Three or more transits of a star exceeding a combined threshold of eight sigma with a statistically consistent period, brightness change and duration provide a rigorous method of detection. From the relative brightness change the planet size can be calculated. From the period the orbital size can be calculated and its location relative to the HZ determined. Presented here are: the mission goals, the top level system design requirements derived from these goals that drive the flight system design, a number of the trades that have lead to the mission concept, expected photometric performance dependence on stellar brightness and spectral type based on the system 'noise tree' analysis. Updated estimates are presented of the numbers of detectable planets versus size, orbit, stellar spectral type and distances based on a planet frequency hypothesis. The current project schedule and organization are given.

Geo-neutrinos and earth's interior

International Nuclear Information System (INIS)

Fiorentini, Gianni; Lissia, Marcello; Mantovani, Fabio

2007-01-01

The deepest hole that has ever been dug is about 12 km deep. Geochemists analyze samples from the Earth's crust and from the top of the mantle. Seismology can reconstruct the density profile throughout all Earth, but not its composition. In this respect, our planet is mainly unexplored. Geo-neutrinos, the antineutrinos from the progenies of U, Th and 40 K decays in the Earth, bring to the surface information from the whole planet, concerning its content of natural radioactive elements. Their detection can shed light on the sources of the terrestrial heat flow, on the present composition, and on the origins of the Earth. Geo-neutrinos represent a new probe of our planet, which can be exploited as a consequence of two fundamental advances that occurred in the last few years: the development of extremely low background neutrino detectors and the progress on understanding neutrino propagation. We review the status and the prospects of the field

Venus: The Atmosphere, Climate, Surface, Interior and Near-Space Environment of an Earth-Like Planet

Science.gov (United States)

Taylor, Fredric W.; Svedhem, Håkan; Head, James W.

2018-02-01

This is a review of current knowledge about Earth's nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a summary of previous Venus observations. The scientific discussions which follow are divided into three main sections: on the surface and interior; the atmosphere and climate; and the thermosphere, exosphere and magnetosphere. These reports are intended to provide an overview for the general reader, and also an introduction to the more detailed topical surveys in the following articles in this issue, where full references to original material may be found.

Colors of extreme exo-Earth environments.

Science.gov (United States)

Hegde, Siddharth; Kaltenegger, Lisa

2013-01-01

The search for extrasolar planets has already detected rocky planets and several planetary candidates with minimum masses that are consistent with rocky planets in the habitable zone of their host stars. A low-resolution spectrum in the form of a color-color diagram of an exoplanet is likely to be one of the first post-detection quantities to be measured for the case of direct detection. In this paper, we explore potentially detectable surface features on rocky exoplanets and their connection to, and importance as, a habitat for extremophiles, as known on Earth. Extremophiles provide us with the minimum known envelope of environmental limits for life on our planet. The color of a planet reveals information on its properties, especially for surface features of rocky planets with clear atmospheres. We use filter photometry in the visible as a first step in the characterization of rocky exoplanets to prioritize targets for follow-up spectroscopy. Many surface environments on Earth have characteristic albedos and occupy a different color space in the visible waveband (0.4-0.9 μm) that can be distinguished remotely. These detectable surface features can be linked to the extreme niches that support extremophiles on Earth and provide a link between geomicrobiology and observational astronomy. This paper explores how filter photometry can serve as a first step in characterizing Earth-like exoplanets for an aerobic as well as an anaerobic atmosphere, thereby prioritizing targets to search for atmospheric biosignatures.

The Aqua-Planet Experiment (APE): CONTROL SST Simulation

Science.gov (United States)

Blackburn, Michael; Williamson, David L.; Nakajima, Kensuke; Ohfuchi, Wataru; Takahashi, Yoshiyuki O.; Hayashi, Yoshi-Yuki; Nakamura, Hisashi; Ishiwatari, Masaki; Mcgregor, John L.; Borth, Hartmut;

Astronomers find distant planet like Jupiter

CERN Multimedia

2003-01-01

Astronomers searching for planetary systems like our solar system have found a planet similar to Jupiter orbiting a nearby star similar to our Sun, about 90 light-years from Earth, according to researchers (1/2 page).

Tandem planet formation for solar system-like planetary systems

Directory of Open Access Journals (Sweden)

Yusuke Imaeda

2017-03-01

Full Text Available We present a new united theory of planet formation, which includes magneto-rotational instability (MRI and porous aggregation of solid particles in a consistent way. We show that the “tandem planet formation” regime is likely to result in solar system-like planetary systems. In the tandem planet formation regime, planetesimals form at two distinct sites: the outer and inner edges of the MRI suppressed region. The former is likely to be the source of the outer gas giants, and the latter is the source for the inner volatile-free rocky planets. Our study spans disks with a various range of accretion rates, and we find that tandem planet formation can occur for M˙=10−7.3-10−6.9M⊙yr−1. The rocky planets form between 0.4–2 AU, while the icy planets form between 6–30 AU; no planets form in 2–6 AU region for any accretion rate. This is consistent with the gap in the solid component distribution in the solar system, which has only a relatively small Mars and a very small amount of material in the main asteroid belt from 2–6 AU. The tandem regime is consistent with the idea that the Earth was initially formed as a completely volatile-free planet. Water and other volatile elements came later through the accretion of icy material by occasional inward scattering from the outer regions. Reactions between reductive minerals, such as schreibersite (Fe3P, and water are essential to supply energy and nutrients for primitive life on Earth.

Terrestrial Planet Formation from an Annulus -- Revisited

Science.gov (United States)

Deienno, Rogerio; Walsh, Kevin J.; Kretke, Katherine A.; Levison, Harold F.

2018-04-01

Numerous recent theories of terrestrial planet formation suggest that, in order to reproduce the observed large Earth to Mars mass ratio, planets formed from an annulus of material within 1 au. The success of these models typically rely on a Mars sized embryo being scattered outside 1 au (to ~1.5 au) and starving, while those remaining inside 1 au continue growing, forming Earth and Venus. In some models the scattering is instigated by the migration of giant planets, while in others an embryo-instability naturally occurs due to the dissipation of the gaseous solar nebula. While these models can typically succeed in reproducing the overall mass ratio among the planets, the final angular momentum deficit (AMD) of the present terrestrial planets in our Solar System, and their radial mass concentration (RMC), namely the position where Mars end up in the simulations, are not always well reproduced. Assuming that the gas nebula may not be entirely dissipated when such an embryo-instability happens, here, we study the effects that the time of such an instability can have on the final AMD and RMC. In addition, we also included energy dissipation within embryo-embryo collisions by assuming a given coefficient of restitution for collisions. Our results show that: i) dissipation within embryo-embryo collisions do not play any important role in the final terrestrial planetary system; ii) the final AMD decreases only when the number of final planets formed increases; iii) the RMC tends to always be lower than the present value no matter the number of final planets; and iv) depending on the time that the embryo-instability happen, if too early, with too much gas still present, a second instability will generally happen after the dissipation of the gas nebula.

Precise Masses & Radii of the Planets Orbiting K2-3 and GJ3470

Science.gov (United States)

Kosiarek, Molly; Crossfield, Ian; Hardegree-Ullman, Kevin; Livingston, John; Howard, Andrew; Fulton, Benjamin; Hirsch, Lea; Isaacson, Howard; Petigura, Erik; Sinukoff, Evan; Weiss, Lauren; Knutson, Heather; Bonfils, Xavier; Benneke, Björn; Beichman, Charles; Dressing, Courtney

2018-01-01

We report improved masses, radii, and densities for two planetary systems, K2-3 and GJ3470, derived from a combination of new radial velocity and transit observations. Both stars are nearby, early M dwarfs. K2-3 hosts three super-Earth planets between 1.5 and 2 Earth-radii at orbital periods between 10 and 45 days, while GJ 3470 hosts one 4 Earth-radii planet with a period of 3.3 days. Furthermore, we confirmed GJ3470's rotation period through multi-year ground-based photometry; RV analysis must account for this rotation signature. Due to the planets' low densities (all stars, they are among the best candidates for transmission spectroscopy with JWST and HST in order to characterize their atmospheric compositions.

The effect of planets beyond the ice line on the accretion of volatiles by habitable-zone rocky planets

International Nuclear Information System (INIS)

Quintana, Elisa V.; Lissauer, Jack J.

2014-01-01

Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M ⊕ to 1 M J ) in Jupiter's orbit at ∼5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.

The effect of planets beyond the ice line on the accretion of volatiles by habitable-zone rocky planets

Energy Technology Data Exchange (ETDEWEB)

Quintana, Elisa V. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Lissauer, Jack J., E-mail: elisa.quintana@nasa.gov [Space Science and Astrobiology Division 245-3, NASA Ames Research Center, Moffett Field, CA 94035 (United States)

2014-05-01

Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M {sub ⊕} to 1 M {sub J}) in Jupiter's orbit at ∼5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.

Planet traps and planetary cores: origins of the planet-metallicity correlation

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, Yasuhiro [Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), P.O. Box 23-141, Taipei 10641, Taiwan (China); Pudritz, Ralph E., E-mail: yasu@asiaa.sinica.edu.tw, E-mail: pudritz@physics.mcmaster.ca [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)

2014-10-10

Massive exoplanets are observed preferentially around high metallicity ([Fe/H]) stars while low-mass exoplanets do not show such an effect. This so-called planet-metallicity correlation generally favors the idea that most observed gas giants at r < 10 AU are formed via a core accretion process. We investigate the origin of this phenomenon using a semi-analytical model, wherein the standard core accretion takes place at planet traps in protostellar disks where rapid type I migrators are halted. We focus on the three major exoplanetary populations—hot Jupiters, exo-Jupiters located at r ≅ 1 AU, and the low-mass planets. We show using a statistical approach that the planet-metallicity correlations are well reproduced in these models. We find that there are specific transition metallicities with values [Fe/H] = –0.2 to –0.4, below which the low-mass population dominates, and above which the Jovian populations take over. The exo-Jupiters significantly exceed the hot Jupiter population at all observed metallicities. The low-mass planets formed via the core accretion are insensitive to metallicity, which may account for a large fraction of the observed super-Earths and hot-Neptunes. Finally, a controlling factor in building massive planets is the critical mass of planetary cores (M {sub c,} {sub crit}) that regulates the onset of rapid gas accretion. Assuming the current data is roughly complete at [Fe/H] > –0.6, our models predict that the most likely value of the 'mean' critical core mass of Jovian planets is (M {sub c,} {sub crit}) ≅ 5 M {sub ⊕} rather than 10 M {sub ⊕}. This implies that grain opacities in accreting envelopes should be reduced in order to lower M {sub c,} {sub crit}.

Discovery of two planets around a millisecond pulsar

Science.gov (United States)

Wolszczan, A.

1992-01-01

By timing the arrival of radio signals from a rapidly spinning pulsar at the Arecibo Observatory's radio/radar telescope, the most convincing evidence so far for a planetary system outside our own has been found: two or possibly three planets that orbit the neutron star called PSR1257+12. This finding indicates that planet formation may be a more common process than previously anticipated and that the formation of disks of gas and dust that are sufficiently massive to condense into Earth-sized planets orbiting their central bodies can take place under surprisingly diverse conditions.

SEARCHING FOR THE SIGNATURES OF TERRESTRIAL PLANETS IN SOLAR ANALOGS

International Nuclear Information System (INIS)

Gonzalez Hernandez, J. I.; Israelian, G.; Delgado-Mena, E.; Santos, N. C.; Sousa, S.; Neves, V.; Udry, S.

2010-01-01

We present a fully differential chemical abundance analysis using very high resolution (λ/δλ ∼> 85, 000) and very high signal-to-noise (S/N ∼800 on average) HARPS and UVES spectra of 7 solar twins and 95 solar analogs, of which 24 are planet hosts and 71 are stars without detected planets. The whole sample of solar analogs provides very accurate Galactic chemical evolution trends in the metallicity range -0.3 < [Fe/H] < 0.5. Solar twins with and without planets show similar mean abundance ratios. We have also analyzed a sub-sample of 28 solar analogs, 14 planet hosts, and 14 stars without known planets, with spectra at S/N ∼850 on average, in the metallicity range 0.14 < [Fe/H] < 0.36, and find the same abundance pattern for both samples of stars with and without planets. This result does not depend on either the planet mass, from 7 Earth masses to 17.4 Jupiter masses, or the orbital period of the planets, from 3 to 4300 days. In addition, we have derived the slope of the abundance ratios as a function of the condensation temperature for each star and again find similar distributions of the slopes for both stars with and without planets. In particular, the peaks of these two distributions are placed at a similar value but with the opposite sign to that expected from a possible signature of terrestrial planets. In particular, two of the planetary systems in this sample, each of them containing a super-Earth-like planet, show slope values very close to these peaks, which may suggest that these abundance patterns are not related to the presence of terrestrial planets.

WATER TRAPPING ON TIDALLY LOCKED TERRESTRIAL PLANETS REQUIRES SPECIAL CONDITIONS

Energy Technology Data Exchange (ETDEWEB)

Yang, Jun; Abbot, Dorian S. [Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Liu, Yonggang [Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544 (United States); Hu, Yongyun, E-mail: junyang28@uchicago.edu [Laboratory for Climate and Atmosphere-Ocean Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing (China)

2014-12-01

Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld, we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, nightside sea ice remains O(10 m) thick and nightside water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete dayside dessiccation. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth's would be susceptible to complete water trapping.

Formation of telluric planets and the origin of terrestrial water

Directory of Open Access Journals (Sweden)

Raymond Sean

2014-02-01

Full Text Available Simulations of planet formation have failed to reproduce Mars’ small mass (compared with Earth for 20 years. Here I will present a solution to the Mars problem that invokes large-scale migration of Jupiter and Saturn while they were still embedded in the gaseous protoplanetary disk. Jupiter first migrated inward, then “tacked” and migrated back outward when Saturn caught up to it and became trapped in resonance. If this tack occurred when Jupiter was at 1.5 AU then the inner disk of rocky planetesimals and embryos is truncated and the masses and orbits of all four terrestrial planet are quantitatively reproduced. As the giant planets migrate back outward they re-populate the asteroid belt from two different source populations, matching the structure of the current belt. C-type material is also scattered inward to the terrestrial planet-forming zone, delivering about the right amount of water to Earth on 10-50 Myr timescales.

Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler

OpenAIRE

Howard, Andrew W.; Marcy, Geoffrey W.; Bryson, Stephen T.; Jenkins, Jon M.; Rowe, Jason F.; Batalha, Natalie M.; Borucki, William J.; Koch, David G.; Dunham, Edward W.; Gautier III, Thomas N.; Van Cleve, Jeffrey; Cochran, William D.; Latham, David W.; Lissauer, Jack J.; Torres, Guillermo

2011-01-01

We report the distribution of planets as a function of planet radius (R_p), orbital period (P), and stellar effective temperature (Teff) for P < 50 day orbits around GK stars. These results are based on the 1,235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 Earth radii (Re). For each of the 156,000 target stars we assess the detectability of planets as a function of R_p and P. We also correct for the geomet...

THE INFLUENCE OF THERMAL EVOLUTION IN THE MAGNETIC PROTECTION OF TERRESTRIAL PLANETS

Energy Technology Data Exchange (ETDEWEB)

Zuluaga, Jorge I.; Bustamante, Sebastian; Cuartas, Pablo A. [Instituto de Fisica-FCEN, Universidad de Antioquia, Calle 67 No. 53-108, Medellin (Colombia); Hoyos, Jaime H., E-mail: jzuluaga@fisica.udea.edu.co, E-mail: sbustama@pegasus.udea.edu.co, E-mail: p.cuartas@fisica.udea.edu.co, E-mail: jhhoyos@udem.edu.co [Departamento de Ciencias Basicas, Universidad de Medellin, Carrera 87 No. 30-65, Medellin (Colombia)

2013-06-10

Magnetic protection of potentially habitable planets plays a central role in determining their actual habitability and/or the chances of detecting atmospheric biosignatures. Here we develop a thermal evolution model of potentially habitable Earth-like planets and super-Earths (SEs). Using up-to-date dynamo-scaling laws, we predict the properties of core dynamo magnetic fields and study the influence of thermal evolution on their properties. The level of magnetic protection of tidally locked and unlocked planets is estimated by combining simplified models of the planetary magnetosphere and a phenomenological description of the stellar wind. Thermal evolution introduces a strong dependence of magnetic protection on planetary mass and rotation rate. Tidally locked terrestrial planets with an Earth-like composition would have early dayside magnetopause distances between 1.5 and 4.0 R{sub p} , larger than previously estimated. Unlocked planets with periods of rotation {approx}1 day are protected by magnetospheres extending between 3 and 8 R{sub p} . Our results are robust in comparison with variations in planetary bulk composition and uncertainties in other critical model parameters. For illustration purposes, the thermal evolution and magnetic protection of the potentially habitable SEs GL 581d, GJ 667Cc, and HD 40307g were also studied. Assuming an Earth-like composition, we found that the dynamos of these planets are already extinct or close to being shut down. While GL 581d is the best protected, the protection of HD 40307g cannot be reliably estimated. GJ 667Cc, even under optimistic conditions, seems to be severely exposed to the stellar wind, and, under the conditions of our model, has probably suffered massive atmospheric losses.

The "Earth Physics" Workshops Offered by the Earth Science Education Unit

Science.gov (United States)

Davies, Stephen

2012-01-01

Earth science has a part to play in broadening students' learning experience in physics. The Earth Science Education Unit presents a range of (free) workshops to teachers and trainee teachers, suggesting how Earth-based science activities, which show how we understand and use the planet we live on, can easily be slotted into normal science…

The Search for Another Earth

Indian Academy of Sciences (India)

2016-08-26

/fulltext/reso/021/07/0641-0652. Keywords. Stars, planets, planetary systems, detection. Abstract. Is there life anywhere else in the vast cosmos?Are there planets similar to the Earth? For centuries,these questions baffled ...

TWO SMALL PLANETS TRANSITING HD 3167

Energy Technology Data Exchange (ETDEWEB)

Vanderburg, Andrew; Bieryla, Allyson; Latham, David W.; Mayo, Andrew W.; Berlind, Perry [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Duev, Dmitry A.; Jensen-Clem, Rebecca; Kulkarni, Shrinivas; Riddle, Reed [California Institute of Technology, Pasadena, CA 91125 (United States); Baranec, Christoph [University of Hawai‘i at Mānoa, Hilo, HI 96720 (United States); Law, Nicholas M. [University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Nieberding, Megan N. [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Salama, Maïssa, E-mail: avanderburg@cfa.harvard.edu [University of Hawai‘i at Mānoa, Honolulu, HI 96822 (United States)

2016-09-20

We report the discovery of two super-Earth-sized planets transiting the bright (V = 8.94, K = 7.07) nearby late G-dwarf HD 3167, using data collected by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6 R {sub ⊕} and an ultra-short orbital period of only 0.96 days. The outer planet, HD 3167 c, has a radius of 2.9 R {sub ⊕} and orbits its host star every 29.85 days. At a distance of just 45.8 ± 2.2 pc, HD 3167 is one of the closest and brightest stars hosting multiple transiting planets, making HD 3167 b and c well suited for follow-up observations. The star is chromospherically inactive with low rotational line-broadening, ideal for radial velocity observations to measure the planets’ masses. The outer planet is large enough that it likely has a thick gaseous envelope that could be studied via transmission spectroscopy. Planets transiting bright, nearby stars like HD 3167 are valuable objects to study leading up to the launch of the James Webb Space Telescope .

XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

Science.gov (United States)

Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

2013-11-01

The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general.

WHERE TO FIND HABITABLE ''EARTHS'' IN CIRCUMBINARY SYSTEMS

International Nuclear Information System (INIS)

Liu Huigen; Zhang Hui; Zhou Jilin

2013-01-01

Six P-type planets have been found thus far around five binary systems, i.e., Kepler-16b, 34b, 35b, 38b, and 47b and c, which are all Neptune- or Jupiter-like planets. The stability of planets and the habitable zones are influenced by the gravitational and radiative perturbations of binary companions. In this Letter, we check the stability of an additional habitable Earth-mass planet in each system. Based on our simulations in 10 Myr, a habitable ''Earth'' is hardly stable in Kepler-16, while a stable ''Earth'' in Kepler-47 close to the boundaries of the habitable zone is possible. In contrast, Kepler-34, 35, and 38 seem to have high probabilities of being able to tolerante a stable ''Earth'' in their habitable zones. The affects of transit time variations are quite small due to the small mass of an undetected ''Earth,'' except that of Kepler-16b. With a time precision of 10 –3 day (∼88 s), an ''Earth'' in the corotational resonance with Kepler-16b can be detected in three years, while habitable ''Earths'' in the Kepler-34 and 38 systems can be detected in 10 yr. Habitable ''Earths'' in Kepler-35 and 47 are not likely to be detected in 10 yr under this precision.

Extreme Water Loss and Abiotic O2 Buildup on Planets Throughout the Habitable Zones of M Dwarfs

Science.gov (United States)

Barnes, R.

2015-01-01

Abstract We show that terrestrial planets in the habitable zones of M dwarfs older than ∼1 Gyr could have been in runaway greenhouses for several hundred million years following their formation due to the star's extended pre-main sequence phase, provided they form with abundant surface water. Such prolonged runaway greenhouses can lead to planetary evolution divergent from that of Earth. During this early runaway phase, photolysis of water vapor and hydrogen/oxygen escape to space can lead to the loss of several Earth oceans of water from planets throughout the habitable zone, regardless of whether the escape is energy-limited or diffusion-limited. We find that the amount of water lost scales with the planet mass, since the diffusion-limited hydrogen escape flux is proportional to the planet surface gravity. In addition to undergoing potential desiccation, planets with inefficient oxygen sinks at the surface may build up hundreds to thousands of bar of abiotically produced O2, resulting in potential false positives for life. The amount of O2 that builds up also scales with the planet mass; we find that O2 builds up at a constant rate that is controlled by diffusion: ∼5 bar/Myr on Earth-mass planets and up to ∼25 bar/Myr on super-Earths. As a result, some recently discovered super-Earths in the habitable zone such as GJ 667Cc could have built up as many as 2000 bar of O2 due to the loss of up to 10 Earth oceans of water. The fate of a given planet strongly depends on the extreme ultraviolet flux, the duration of the runaway regime, the initial water content, and the rate at which oxygen is absorbed by the surface. In general, we find that the initial phase of high luminosity may compromise the habitability of many terrestrial planets orbiting low-mass stars. Key Words: Astrobiology—Biosignatures—Extrasolar terrestrial planets—Habitability—Planetary atmospheres. Astrobiology 15, 119–143. PMID:25629240

Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs.

Science.gov (United States)

Luger, R; Barnes, R

2015-02-01

We show that terrestrial planets in the habitable zones of M dwarfs older than ∼1 Gyr could have been in runaway greenhouses for several hundred million years following their formation due to the star's extended pre-main sequence phase, provided they form with abundant surface water. Such prolonged runaway greenhouses can lead to planetary evolution divergent from that of Earth. During this early runaway phase, photolysis of water vapor and hydrogen/oxygen escape to space can lead to the loss of several Earth oceans of water from planets throughout the habitable zone, regardless of whether the escape is energy-limited or diffusion-limited. We find that the amount of water lost scales with the planet mass, since the diffusion-limited hydrogen escape flux is proportional to the planet surface gravity. In addition to undergoing potential desiccation, planets with inefficient oxygen sinks at the surface may build up hundreds to thousands of bar of abiotically produced O2, resulting in potential false positives for life. The amount of O2 that builds up also scales with the planet mass; we find that O2 builds up at a constant rate that is controlled by diffusion: ∼5 bar/Myr on Earth-mass planets and up to ∼25 bar/Myr on super-Earths. As a result, some recently discovered super-Earths in the habitable zone such as GJ 667Cc could have built up as many as 2000 bar of O2 due to the loss of up to 10 Earth oceans of water. The fate of a given planet strongly depends on the extreme ultraviolet flux, the duration of the runaway regime, the initial water content, and the rate at which oxygen is absorbed by the surface. In general, we find that the initial phase of high luminosity may compromise the habitability of many terrestrial planets orbiting low-mass stars.

Titan and habitable planets around M-dwarfs.

Science.gov (United States)

Lunine, Jonathan I

2010-01-01

The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.

Views from EPOXI. Colors in Our Solar System as an Analog for Extrasolar Planets

Science.gov (United States)

Crow, Carolyn A.; McFadden, L. A.; Robinson, T.; Livengood, T. A.; Hewagama, T.; Barry, R. K.; Deming, L. D.; Meadows, V.; Lisse, C. M.

2010-01-01

With extrasolar planet detection becoming more common place, the frontiers of extrasolar planet science have moved beyond detection to the observations required to determine planetary properties. Once the existing observational challenges have been overcome, the first visible-light studies of extrasolar Earth-sized planets will likely employ filter photometry or low-resolution. spectroscopy to observe disk-integrated radiation from the unresolved planet. While spectroscopy of these targets is highly desirable, and provides the most robust form of characterization. S/N considerations presently limit spectroscopic measurements of extrasolar worlds. Broadband filter photometry will thus serve as a first line of characterization. In this paper we use Extrasolar Observation and Characterization (EPOCh) filter photometry of the Earth. Moon and Mars model spectra. and previous photometric and spectroscopic observations of a range the solar system planets. Titan, and Moon to explore the limitations of using color as a baseline for understanding extrasolar planets

Habitability Properties of Circumbinary Planets

Science.gov (United States)

Shevchenko, Ivan I.

2017-06-01

It is shown that several habitability conditions (in fact, at least seven such conditions) appear to be fulfilled automatically by circumbinary planets of main-sequence stars (CBP-MS), whereas on Earth, these conditions are fulfilled only by chance. Therefore, it looks natural that most of the production of replicating biopolymers in the Galaxy is concentrated on particular classes of CBP-MS, and life on Earth is an outlier, in this sense. In this scenario, Lathe’s mechanism for the tidal “chain reaction” abiogenesis on Earth is favored as generic for CBP-MS, due to photo-tidal synchronization inherent to them. Problems with this scenario are discussed in detail.

HABEBEE: habitability of eyeball-exo-Earths.

Science.gov (United States)

Angerhausen, Daniel; Sapers, Haley; Citron, Robert; Bergantini, Alexandre; Lutz, Stefanie; Queiroz, Luciano Lopes; da Rosa Alexandre, Marcelo; Araujo, Ana Carolina Vieira

2013-03-01

Extrasolar Earth and super-Earth planets orbiting within the habitable zone of M dwarf host stars may play a significant role in the discovery of habitable environments beyond Earth. Spectroscopic characterization of these exoplanets with respect to habitability requires the determination of habitability parameters with respect to remote sensing. The habitable zone of dwarf stars is located in close proximity to the host star, such that exoplanets orbiting within this zone will likely be tidally locked. On terrestrial planets with an icy shell, this may produce a liquid water ocean at the substellar point, one particular "Eyeball Earth" state. In this research proposal, HABEBEE: exploring the HABitability of Eyeball-Exo-Earths, we define the parameters necessary to achieve a stable icy Eyeball Earth capable of supporting life. Astronomical and geochemical research will define parameters needed to simulate potentially habitable environments on an icy Eyeball Earth planet. Biological requirements will be based on detailed studies of microbial communities within Earth analog environments. Using the interdisciplinary results of both the physical and biological teams, we will set up a simulation chamber to expose a cold- and UV-tolerant microbial community to the theoretically derived Eyeball Earth climate states, simulating the composition, atmosphere, physical parameters, and stellar irradiation. Combining the results of both studies will enable us to derive observable parameters as well as target decision guidance and feasibility analysis for upcoming astronomical platforms.

A Maximum Radius for Habitable Planets.

Science.gov (United States)

Alibert, Yann

2015-09-01

We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope.

Detecting tree-like multicellular life on extrasolar planets.

Science.gov (United States)

Doughty, Christopher E; Wolf, Adam

2010-11-01

Over the next two decades, NASA and ESA are planning a series of space-based observatories to find Earth-like planets and determine whether life exists on these planets. Previous studies have assessed the likelihood of detecting life through signs of biogenic gases in the atmosphere or a red edge. Biogenic gases and the red edge could be signs of either single-celled or multicellular life. In this study, we propose a technique with which to determine whether tree-like multicellular life exists on extrasolar planets. For multicellular photosynthetic organisms on Earth, competition for light and the need to transport water and nutrients has led to a tree-like body plan characterized by hierarchical branching networks. This design results in a distinct bidirectional reflectance distribution function (BRDF) that causes differing reflectance at different sun/view geometries. BRDF arises from the changing visibility of the shadows cast by objects, and the presence of tree-like structures is clearly distinguishable from flat ground with the same reflectance spectrum. We examined whether the BRDF could detect the existence of tree-like structures on an extrasolar planet by using changes in planetary albedo as a planet orbits its star. We used a semi-empirical BRDF model to simulate vegetation reflectance at different planetary phase angles and both simulated and real cloud cover to calculate disk and rotation-averaged planetary albedo for a vegetated and non-vegetated planet with abundant liquid water. We found that even if the entire planetary albedo were rendered to a single pixel, the rate of increase of albedo as a planet approaches full illumination would be comparatively greater on a vegetated planet than on a non-vegetated planet. Depending on how accurately planetary cloud cover can be resolved and the capabilities of the coronagraph to resolve exoplanets, this technique could theoretically detect tree-like multicellular life on exoplanets in 50 stellar systems.

Atmospheres of partially differentiated super-Earth exoplanets

Science.gov (United States)

Schaefer, Laura; Sasselov, Dimitar

2015-11-01

Terrestrial exoplanets have been discovered in a range of sizes, densities and orbital locations that defy our expectations based upon the Solar System. Planets discovered to date with radii less than ~1.5-1.6 Earth radii all seem to fall on an iso-density curve with the Earth [1]. However, mass and radius determinations, which depend on the known properties of the host star, are not accurate enough to distinguish between a fully differentiated three-layer planet (core, mantle, ocean/atmosphere) and an incompletely differentiated planet [2]. Full differentiation of a planet will depend upon the conditions at the time of accretion, including the abundance of short-lived radioisotopes, which will vary from system to system, as well as the number of giant impacts the planet experiences. Furthermore, separation of metal and silicates at the much larger pressures found inside super-Earths will depend on how the chemistry of these materials change at high pressures. There are therefore hints emerging that not all super-Earths will be fully differentiated. Incomplete differentiation will result in a more reduced mantle oxidation state and may have implications for the composition of an outgassed atmosphere. Here we will present the first results from a chemical equilibrium model of the composition of such an outgassed atmosphere and discuss the possibility of distinguishing between fully and incompletely differentiated planets through atmospheric observations.[1] Rogers, L. 2015. ApJ, 801, 41. [2] Zeng, L. & Sasselov, D. 2013. PASP, 125, 227.

Whole planet cooling and the radiogenic heat source contents of the earth and moon

International Nuclear Information System (INIS)

Schubert, G.; Stevenson, D.

1980-01-01

It is widely believed that the surface heat flows of the earth and moon provide good measures of the total amounts of radioactives in these bodies. Simple thermal evolution models, based on subsolidus whole mantle convection, indicate that this may not be the case. These models have been constructed assuming an initially hot state, but with a wide variety of choices for the parameters characterizing the rheology and convective vigor. All models are constrained to be consistent with present-day surface heat fluxes, and many of the terrestrial models are consistent with the mantle viscosities indicated by post-glacial rebound. For the earth the acceptable models give a radiogenic heat production that is only 65--85% of the surface heat output, the difference being due to secular cooling of the earth (about 50 0 --100 0 C per 10 9 years in the upper mantle). It is argued that the actual heat generation may be substantially less, since the models omit core heat, upward migration of heat sources, possible layering of the mantle, and deviations from steady convection. Geochemical models which are near to chondritic (apart from potassium depletion) are marginally consistent with surface heat flow. In the lunar models, heat generation is typically only 70--80% of the surface heat flow, even with allowance for the strong near-surface enhancement of radioactives. Despite the simplicity of the models the persistence of a significant difference between heat generation and heat output for a wide range of parameter choices indicates that this difference is real and should be incorporated in geochemical modeling of the planets

The ocean planet.

Science.gov (United States)

Hinrichsen, D

1998-01-01

The Blue Planet is 70% water, and all but 3% of it is salt water. Life on earth first evolved in the primordial soup of ancient seas, and though today's seas provide 99% of all living space on the planet, little is known about the world's oceans. However, the fact that the greatest threats to the integrity of our oceans come from land-based activities is becoming clear. Humankind is in the process of annihilating the coastal and ocean ecosystems and the wealth of biodiversity they harbor. Mounting population and development pressures have taken a grim toll on coastal and ocean resources. The trend arising from such growth is the chronic overexploitation of marine resources, whereby rapidly expanding coastal populations and the growth of cities have contributed to a rising tide of pollution in nearly all of the world's seas. This crisis is made worse by government inaction and a frustrating inability to enforce existing coastal and ocean management regulations. Such inability is mainly because concerned areas contain so many different types of regulations and involve so many levels of government, that rational planning and coordination of efforts are rendered impossible. Concerted efforts are needed by national governments and the international community to start preserving the ultimate source of all life on earth.

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Science.gov (United States)

Way, M. J.; Aleinov, I.; Amundsen, David S.; Chandler, M. A.; Clune, T. L.; Del Genio, A.; Fujii, Y.; Kelley, M.; Kiang, N. Y.; Sohl, L.;

Giant Impacts on Earth-Like Worlds

Science.gov (United States)

Kohler, Susanna

2016-05-01

Earth has experienced a large number of impacts, from the cratering events that may have caused mass extinctions to the enormous impact believed to have formed the Moon. A new study examines whether our planets impact history is typical for Earth-like worlds.N-Body ChallengesTimeline placing the authors simulations in context of the history of our solar system (click for a closer look). [Quintana et al. 2016]The final stages of terrestrial planet formation are thought to be dominated by giant impacts of bodies in the protoplanetary disk. During this stage, protoplanets smash into one another and accrete, greatly influencing the growth, composition, and habitability of the final planets.There are two major challenges when simulating this N-body planet formation. The first is fragmentation: since computational time scales as N^2, simulating lots of bodies that split into many more bodies is very computationally intensive. For this reason, fragmentation is usually ignored; simulations instead assume perfect accretion during collisions.Total number of bodies remaining within the authors simulations over time, with fragmentation included (grey) and ignored (red). Both simulations result in the same final number of bodies, but the ones that include fragmentation take more time to reach that final number. [Quintana et al. 2016]The second challengeis that many-body systems are chaotic, which means its necessary to do a large number of simulations to make statistical statements about outcomes.Adding FragmentationA team of scientists led by Elisa Quintana (NASA NPP Senior Fellow at the Ames Research Center) has recently pushed at these challenges by modeling inner-planet formation using a code that does include fragmentation. The team ran 140 simulations with and 140 without the effects of fragmentation using similar initial conditions to understand how including fragmentation affects the outcome.Quintana and collaborators then used the fragmentation-inclusive simulations to

Possibilities for the detection of microbial life on extrasolar planets.

Science.gov (United States)

Knacke, Roger F

2003-01-01

We consider possibilities for the remote detection of microbial life on extrasolar planets. The Darwin/Terrestrial Planet Finder (TPF) telescope concepts for observations of terrestrial planets focus on indirect searches for life through the detection of atmospheric gases related to life processes. Direct detection of extraterrestrial life may also be possible through well-designed searches for microbial life forms. Satellites in Earth orbit routinely monitor colonies of terrestrial algae in oceans and lakes by analysis of reflected ocean light in the visible region of the spectrum. These remote sensing techniques suggest strategies for extrasolar searches for signatures of chlorophylls and related photosynthetic compounds associated with life. However, identification of such life-related compounds on extrasolar planets would require observations through strong, interfering absorptions and scattering radiances from the remote atmospheres and landmasses. Techniques for removal of interfering radiances have been extensively developed for remote sensing from Earth orbit. Comparable techniques would have to be developed for extrasolar planet observations also, but doing so would be challenging for a remote planet. Darwin/TPF coronagraph concepts operating in the visible seem to be best suited for searches for extrasolar microbial life forms with instruments that can be projected for the 2010-2020 decades, although resolution and signal-to-noise ratio constraints severely limit detection possibilities on terrestrial-type planets. The generation of telescopes with large apertures and extremely high spatial resolutions that will follow Darwin/TPF could offer striking possibilities for the direct detection of extrasolar microbial life.

Climate of an Earth-Like World with Changing Eccentricity

Science.gov (United States)

Kohler, Susanna

2017-02-01

Having a giant planet like Jupiter next door can really wreak havoc on your orbit! A new study examines what such a bad neighbor might mean for the long-term climate of an Earth-like planet.Influence of a Bad NeighborThe presence of a Jupiter-like giant planet in a nearby orbit can significantly affect how terrestrial planets evolve dynamically, causing elements like the planets orbital eccentricities and axial tilts to change over time. Earth is saved this inconvenience Jupiter isnt close enough to significantly influence us, and our large moon stabilizes our orbit against Jupiters tugs.Top panels: Authors simulationoutcomes for Case1, in which the planets eccentricity varies from 0 to 0.283 over 6500 years. Bottom panels: Outcomes for Case 2, in which the planets eccentricity varies from 0 to 0.066 over 4500 years. The highereccentricities reached in Case 1 causes the climate parameters to vary more widely. Click for a better look! [Way Georgakarakos 2017]Mars, on the other hand, isnt as lucky: its possible that Jupiters gravitational pull causes Marss axial tilt, for instance, to evolve through a range as large as 0 to 60 degrees on timescales of millions of years! Marss orbital eccentricity is similarly thought to vary due to Jupiters influence, and both of these factors play a major role in determining Marss climate.As exoplanet missions discover more planets many of which are Earth-like we must carefully consider which among these are most likely to be capable of sustaining life. If having a nearby neighbor like a Jupiter can tug an Earth-like world into an orbit with varying eccentricity, how does this affect the planets climate? Will the planet remain temperate? Or will it develop a runaway heating or cooling effect as it orbits, rendering it uninhabitable?Oceans and OrbitsTo examine these questions, two scientists have built the first ever 3D global climate model simulations of an Earth-like world using a fully coupled ocean (necessary for understanding

Effect of sun and planet-bound dark matter on planet and satellite dynamics in the solar system

International Nuclear Information System (INIS)

Iorio, L.

2010-01-01

We apply our recent results on orbital dynamics around a mass-varying central body to the phenomenon of accretion of Dark Matter-assumed not self-annihilating-on the Sun and the major bodies of the solar system due to its motion throughout the Milky Way halo. We inspect its consequences on the orbits of the planets and their satellites over timescales of the order of the age of the solar system. It turns out that a solar Dark Matter accretion rate of ≈ 10 −12 yr −1 , inferred from the upper limit ΔM/M = 0.02−0.05 on the Sun's Dark Matter content, assumed somehow accumulated during last 4.5 Gyr, would have displaced the planets faraway by about 10 −2 −10 1 au 4.5 Gyr ago. Another consequence is that the semimajor axis of the Earth's orbit, approximately equal to the Astronomical Unit, would undergo a secular increase of 0.02-0.05 m yr −1 , in agreement with the latest observational determinations of the Astronomical Unit secular increase of 0.07±0.02 m yr −1 and 0.05 m yr −1 . By assuming that the Sun will continue to accrete Dark Matter in the next billions year at the same rate as putatively done in the past, the orbits of its planets will shrink by about 10 −1 −10 1 au ( ≈ 0.2−0.5 au for the Earth), with consequences for their fate, especially of the inner planets. On the other hand, lunar and planetary ephemerides set upper bounds on the secular variation of the Sun's gravitational parameter GM which are one one order of magnitude smaller than ≈ 10 −12 yr −1 . Dark Matter accretion on planets has, instead, less relevant consequences for their satellites. Indeed, 4.5 Gyr ago their orbits would have been just 10 −2 −10 1 km wider than now. Dark Matter accretion is not able to explain the observed accelerations of the orbits of some of the Galilean satellites of Jupiter, the secular decrease of the semimajor axis of the Earth's artificial satellite LAGEOS and the secular increase of the Moon's orbit eccentricity

Primordial atmosphere incorporation in planetary embryos and the origin of Neon in terrestrial planets

Science.gov (United States)

Jaupart, Etienne; Charnoz, Sebatien; Moreira, Manuel

2017-09-01

The presence of Neon in terrestrial planet mantles may be attributed to the implantation of solar wind in planetary precursors or to the dissolution of primordial solar gases captured from the accretionary disk into an early magma ocean. This is suggested by the Neon isotopic ratio similar to those of the Sun observed in the Earth mantle. Here, we evaluate the second hypothesis. We use general considerations of planetary accretion and atmospheric science. Using current models of terrestrial planet formation, we study the evolution of standard planetary embryos with masses in a range of 0.1-0.2 MEarth, where MEarth is the Earth's mass, in an annular region at distances between 0.5 and 1.5 Astronomical Units from the star. We determine the characteristics of atmospheres that can be captured by such embryos for a wide range of parameters and calculate the maximum amount of Neon that can be dissolved in the planet. Our calculations may be directly transposed to any other planet. However, we only know of the amount of Neon in the Earth's solid mantle. Thus we use Earth to discuss our results. We find that the amount of dissolved Neon is too small to account for the present-day Neon contents of the Earth's mantle, if the nebular gas disk completely disappears before the largest planetary embryos grow to be ∼0.2 MEarth. This leaves solar irradiation as the most likely source of Neon in terrestrial planets for the most standard case of planetary formation models.

Water loss from terrestrial planets with CO2-rich atmospheres

International Nuclear Information System (INIS)

Wordsworth, R. D.; Pierrehumbert, R. T.

2013-01-01

Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO 2 can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO 2 atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO 2 -rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m –2 (global mean) unlikely to lose more than one Earth ocean of H 2 O over their lifetimes unless they lose all their atmospheric N 2 /CO 2 early on. Because of the variability of H 2 O delivery during accretion, our results suggest that many 'Earth-like' exoplanets in the habitable zone may have ocean-covered surfaces, stable CO 2 /H 2 O-rich atmospheres, and high mean surface temperatures.

Assessment of spatiotemporal fusion algorithms for Planet and Worldview images

Science.gov (United States)

Although Worldview (WV) images (non-pansharpened) have 2-meter resolution, the re-visit times for the same areas may be 7 days or more. In contrast, Planet images using small satellites can cover the whole Earth almost daily. However, the resolution of Planet images is 3.125 m. It will be ideal to f...

Earth's transmission spectrum from lunar eclipse observations.

Science.gov (United States)

Pallé, Enric; Osorio, María Rosa Zapatero; Barrena, Rafael; Montañés-Rodríguez, Pilar; Martín, Eduardo L

2009-06-11

Of the 342 planets so far discovered orbiting other stars, 58 'transit' the stellar disk, meaning that they can be detected through a periodic decrease in the flux of starlight. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration for the characterization of extrasolar planetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obtained during a lunar eclipse. Some biologically relevant atmospheric features that are weak in the reflection spectrum (such as ozone, molecular oxygen, water, carbon dioxide and methane) are much stronger in the transmission spectrum, and indeed stronger than predicted by modelling. We also find the 'fingerprints' of the Earth's ionosphere and of the major atmospheric constituent, molecular nitrogen (N(2)), which are missing in the reflection spectrum.

ON THE SURVIVABILITY AND METAMORPHISM OF TIDALLY DISRUPTED GIANT PLANETS: THE ROLE OF DENSE CORES

Energy Technology Data Exchange (ETDEWEB)

Liu, Shang-Fei; Lin, Douglas N. C. [Kavli Institute for Astronomy and Astrophysics and Department of Astronomy, Peking University, Beijing 100871 (China); Guillochon, James; Ramirez-Ruiz, Enrico, E-mail: liushangfei@pku.edu.cn [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2013-01-01

A large population of planetary candidates in short-period orbits have been found recently through transit searches, mostly with the Kepler mission. Radial velocity surveys have also revealed several Jupiter-mass planets with highly eccentric orbits. Measurements of the Rossiter-McLaughlin effect indicate that the orbital angular momentum vector of some planets is inclined relative to the spin axis of their host stars. This diversity could be induced by post-formation dynamical processes such as planet-planet scattering, the Kozai effect, or secular chaos which brings planets to the vicinity of their host stars. In this work, we propose a novel mechanism to form close-in super-Earths and Neptune-like planets through the tidal disruption of gas giant planets as a consequence of these dynamical processes. We model the core-envelope structure of gas giant planets with composite polytropes which characterize the distinct chemical composition of the core and envelope. Using three-dimensional hydrodynamical simulations of close encounters between Jupiter-like planets and their host stars, we find that the presence of a core with a mass more than 10 times that of the Earth can significantly increase the fraction of envelope which remains bound to it. After the encounter, planets with cores are more likely to be retained by their host stars in contrast with previous studies which suggested that coreless planets are often ejected. As a substantial fraction of their gaseous envelopes is preferentially lost while the dense incompressible cores retain most of their original mass, the resulting metallicity of the surviving planets is increased. Our results suggest that some gas giant planets can be effectively transformed into either super-Earths or Neptune-like planets after multiple close stellar passages. Finally, we analyze the orbits and structure of known planets and Kepler candidates and find that our model is capable of producing some of the shortest-period objects.

Modeling Kepler Transit Light Curves as False Positives: Rejection of Blend Scenarios for Kepler-9, and Validation of Kepler-9 d, a Super-Earth-Size Planet in a Multiple System

Science.gov (United States)

Torres, Guillermo; Fressin, Francois; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Bryson, Stephen T.; Buchhave, Lars A.; Charbonneau, David; Ciardi, David R.; Dunham, Edward W.;

Abiotic production of nitrous oxide by lightning. Implications for a false positive identification of life on Earth-Like Planets around quiescent M Dwarfs

Science.gov (United States)

Navarro, Karina F.; Navarro-Gonzalez, Rafael; McKay, Christopher P.

Nitrous oxide (N _{2}O) is uniformly mixed in the troposphere with a concentration of about 310 ppb but disappears in the stratosphere (Prinn et al., 1990); N _{2}O is mostly emitted at a rate of 1x10 (13) g yr (-1) as a byproduct of microbial activity in soils and in the ocean by two processes: a) denitrification (reduction of nitrate and nitrite), and b) nitrification (oxidation of ammonia) (Maag and Vinther, 1996). The abiotic emission of N _{2}O in the contemporaneous Earth is small, mostly arising from lightning activity (2x10 (9) g yr (-1) , Hill et al., 1984) and by reduction of nitrite by Fe(II)-minerals in soils in Antarctica (Samarkin et al., 2010). Since N _{2}O has absorption bands in the mid-IR (7.8, 8.5, and 17 mumm) that makes it detectable by remote sensing (Topfer et al., 1997; Des Marais et al., 2002), it has been suggested as a potential biosignature in the search for life in extrasolar planets (Churchill and Kasting, 2000). However, the minimum required concentration for positive identification is 10,000 ppb with missions like Terrestrial Planet Finder and Darwin (Churchill and Kasting, 2000). Therefore, it is not a suitable biomarker for extrasolar Earth-like planets orbiting stars similar to the Sun. Because N _{2}O is protected in the troposphere from UV photolysis by the stratospheric ozone layer, its concentration would decrease with decreasing oxygen (O _{2}) concentrations, if the biological source strength remains constant (Kasting and Donahue, 1980). For a primitive Earth-like (Hadean) atmosphere dominated by CO _{2}, and no free O _{2}, the expected N _{2}O concentration would be about 3 ppb with the current microbial N _{2}O flux (Churchill and Kasting, 2000). The resulting N _{2}O spectral signature of this atmosphere would be undetectable unless the N _{2}O microbial flux would be 10 (4) greater than its present value (Churchill and Kasting, 2000). Since this flux is unlikely, it is impossible to use it as a biomarker in anoxic CO

Ensemble Atmospheric Properties of Small Planets around M Dwarfs

Science.gov (United States)

Guo, Xueying; Ballard, Sarah; Dragomir, Diana

2018-01-01

With the growing number of planets discovered by the Kepler mission and ground-base surveys, people start to try to understand the atmospheric features of those uncovered new worlds. While it has been found that hot Jupiters exhibit diverse atmosphere composition with both clear and cloudy/hazy atmosphere possible, similar studies on ensembles of smaller planets (Earth analogs) have been held up due to the faintness of most of their host stars. In this work, a sample of 20 Earth analogs of similar periods around M dwarfs with existing Kepler transit information and Spitzer observations is composed, complemented with previously studies GJ1214b and GJ1132b, as well as the recently announced 7 small planets in the TRAPPIST-1 system. We evaluate their transit depths with uncertainties on the Spitzer 4.5 micron band using the “pixel-level decorrelation” method, and together with their well analyzed Kepler data and Hubble data, we put constraints on their atmosphere haze slopes and cloud levels. Aside from improving the understanding of ensemble properties of small planets, this study will also provide clues of potential targets for detailed atmospheric studies using the upcoming James Webb Telescope.

Kepler-68: Three Planets, One with a Density between that of Earth and Ice Giants

NARCIS (Netherlands)

Gilliland, R.L.; Marcy, G.W.; Rowe, J.F.; Rogers, L.; Torres, G.; Fressin, F.; Lopez, E.D.; Buchhave, L.A.; Christensen-Dalsgaard, J.; Désert, J.M.; Henze, C.E.; Isaacson, H.; Jenkins, J.M.; Lissauer, J.J.; Chaplin, W.J.; Basu, S.; Metcalfe, T.S.; Elsworth, Y.; Handberg, R.; Hekker, S.; Huber, D.; Karoff, C.; Kjeldsen, H.; Lund, M.N.; Lundkvist, M.; Miglio, A.; Charbonneau, D.; Ford, E.B.; Fortney, J.J.; Haas, M.R.; Howard, A.W.; Howell, S.B.; Ragozzine, D.; Thompson, S.E.

2013-01-01

NASA's Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third Jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit, has Mp_{\\rm

The effect of M dwarf starspot activity on low-mass planet

NARCIS (Netherlands)

Barnes, J.R.; Jeffers, S.V.; Jones, H.R.A.

2011-01-01

In light of the growing interest in searching for low mass, rocky planets, we investigate the impact of starspots on radial velocity searches for earth-mass planets in orbit about M dwarf stars. Since new surveys targeting M dwarfs will likely be carried out at infrared wavelengths, a comparison

ON THE NOTION OF WELL-DEFINED TECTONIC REGIMES FOR TERRESTRIAL PLANETS IN THIS SOLAR SYSTEM AND OTHERS

International Nuclear Information System (INIS)

Lenardic, A.; Crowley, J. W.

2012-01-01

A model of coupled mantle convection and planetary tectonics is used to demonstrate that history dependence can outweigh the effects of a planet's energy content and material parameters in determining its tectonic state. The mantle convection-surface tectonics system allows multiple tectonic modes to exist for equivalent planetary parameter values. The tectonic mode of the system is then determined by its specific geologic and climatic history. This implies that models of tectonics and mantle convection will not be able to uniquely determine the tectonic mode of a terrestrial planet without the addition of historical data. Historical data exists, to variable degrees, for all four terrestrial planets within our solar system. For the Earth, the planet with the largest amount of observational data, debate does still remain regarding the geologic and climatic history of Earth's deep past but constraints are available. For planets in other solar systems, no such constraints exist at present. The existence of multiple tectonic modes, for equivalent parameter values, points to a reason why different groups have reached different conclusions regarding the tectonic state of extrasolar terrestrial planets larger than Earth ( s uper-Earths ) . The region of multiple stable solutions is predicted to widen in parameter space for more energetic mantle convection (as would be expected for larger planets). This means that different groups can find different solutions, all potentially viable and stable, using identical models and identical system parameter values. At a more practical level, the results argue that the question of whether extrasolar terrestrial planets will have plate tectonics is unanswerable and will remain so until the temporal evolution of extrasolar planets can be constrained.

Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.

Science.gov (United States)

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-08-03

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.

The Fate of Close-in Planets: Tidal or Magnetic Migration?

Energy Technology Data Exchange (ETDEWEB)

Strugarek, A.; Bolmont, E.; Mathis, S.; Brun, A. S.; Réville, V. [Laboratoire AIM Paris-Saclay, CEA/Irfu Université Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette (France); Gallet, F.; Charbonnel, C., E-mail: antoine.strugarek@cea.fr [Department of Astronomy, University of Geneva, Chemin des Maillettes 51, 1290 Versoix (Switzerland)

2017-10-01

Planets in close-in orbits interact magnetically and tidally with their host stars. These interactions lead to a net torque that makes close-in planets migrate inward or outward depending on their orbital distance. We systematically compare the strength of magnetic and tidal torques for typical observed star–planet systems (T-Tauri and hot Jupiter, M-dwarf and Earth-like planet, K star and hot Jupiter) based on state-of-the-art scaling laws. We find that depending on the characteristics of the system, tidal or magnetic effects can dominate. For very close-in planets, we find that both torques can make a planet migrate on a timescale as small as 10–100 thousands of years. Both effects thus have to be taken into account when predicting the evolution of compact systems.

Kepler planet-detection mission: introduction and first results.

Science.gov (United States)

Borucki, William J; Koch, David; Basri, Gibor; Batalha, Natalie; Brown, Timothy; Caldwell, Douglas; Caldwell, John; Christensen-Dalsgaard, Jørgen; Cochran, William D; DeVore, Edna; Dunham, Edward W; Dupree, Andrea K; Gautier, Thomas N; Geary, John C; Gilliland, Ronald; Gould, Alan; Howell, Steve B; Jenkins, Jon M; Kondo, Yoji; Latham, David W; Marcy, Geoffrey W; Meibom, Søren; Kjeldsen, Hans; Lissauer, Jack J; Monet, David G; Morrison, David; Sasselov, Dimitar; Tarter, Jill; Boss, Alan; Brownlee, Don; Owen, Toby; Buzasi, Derek; Charbonneau, David; Doyle, Laurance; Fortney, Jonathan; Ford, Eric B; Holman, Matthew J; Seager, Sara; Steffen, Jason H; Welsh, William F; Rowe, Jason; Anderson, Howard; Buchhave, Lars; Ciardi, David; Walkowicz, Lucianne; Sherry, William; Horch, Elliott; Isaacson, Howard; Everett, Mark E; Fischer, Debra; Torres, Guillermo; Johnson, John Asher; Endl, Michael; MacQueen, Phillip; Bryson, Stephen T; Dotson, Jessie; Haas, Michael; Kolodziejczak, Jeffrey; Van Cleve, Jeffrey; Chandrasekaran, Hema; Twicken, Joseph D; Quintana, Elisa V; Clarke, Bruce D; Allen, Christopher; Li, Jie; Wu, Haley; Tenenbaum, Peter; Verner, Ekaterina; Bruhweiler, Frederick; Barnes, Jason; Prsa, Andrej

2010-02-19

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

KEPLER PLANETS: A TALE OF EVAPORATION

International Nuclear Information System (INIS)

Owen, James E.; Wu, Yanqin

2013-01-01

Inspired by the Kepler mission's planet discoveries, we consider the thermal contraction of planets close to their parent star, under the influence of evaporation. The mass-loss rates are based on hydrodynamic models of evaporation that include both X-ray and EUV irradiation. We find that only low mass planets with hydrogen envelopes are significantly affected by evaporation, with evaporation being able to remove massive hydrogen envelopes inward of ∼0.1 AU for Neptune-mass objects, while evaporation is negligible for Jupiter-mass objects. Moreover, most of the evaporation occurs in the first 100 Myr of stars' lives when they are more chromospherically active. We construct a theoretical population of planets with varying core masses, envelope masses, orbital separations, and stellar spectral types, and compare this population with the sizes and densities measured for low-mass planets, both in the Kepler mission and from radial velocity surveys. This exercise leads us to conclude that evaporation is the driving force of evolution for close-in Kepler planets. In fact, some 50% of the Kepler planet candidates may have been significantly eroded. Evaporation explains two striking correlations observed in these objects: a lack of large radius/low density planets close to the stars and a possible bimodal distribution in planet sizes with a deficit of planets around 2 R ⊕ . Planets that have experienced high X-ray exposures are generally smaller than this size, and those with lower X-ray exposures are typically larger. A bimodal planet size distribution is naturally predicted by the evaporation model, where, depending on their X-ray exposure, close-in planets can either hold on to hydrogen envelopes ∼0.5%-1% in mass or be stripped entirely. To quantitatively reproduce the observed features, we argue that not only do low-mass Kepler planets need to be made of rocky cores surrounded with hydrogen envelopes, but few of them should have initial masses above 20 M ⊕ and

KEPLER PLANETS: A TALE OF EVAPORATION

Energy Technology Data Exchange (ETDEWEB)

Owen, James E. [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Wu, Yanqin, E-mail: jowen@cita.utoronto.ca, E-mail: wu@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)

2013-10-01

Inspired by the Kepler mission's planet discoveries, we consider the thermal contraction of planets close to their parent star, under the influence of evaporation. The mass-loss rates are based on hydrodynamic models of evaporation that include both X-ray and EUV irradiation. We find that only low mass planets with hydrogen envelopes are significantly affected by evaporation, with evaporation being able to remove massive hydrogen envelopes inward of ∼0.1 AU for Neptune-mass objects, while evaporation is negligible for Jupiter-mass objects. Moreover, most of the evaporation occurs in the first 100 Myr of stars' lives when they are more chromospherically active. We construct a theoretical population of planets with varying core masses, envelope masses, orbital separations, and stellar spectral types, and compare this population with the sizes and densities measured for low-mass planets, both in the Kepler mission and from radial velocity surveys. This exercise leads us to conclude that evaporation is the driving force of evolution for close-in Kepler planets. In fact, some 50% of the Kepler planet candidates may have been significantly eroded. Evaporation explains two striking correlations observed in these objects: a lack of large radius/low density planets close to the stars and a possible bimodal distribution in planet sizes with a deficit of planets around 2 R{sub ⊕}. Planets that have experienced high X-ray exposures are generally smaller than this size, and those with lower X-ray exposures are typically larger. A bimodal planet size distribution is naturally predicted by the evaporation model, where, depending on their X-ray exposure, close-in planets can either hold on to hydrogen envelopes ∼0.5%-1% in mass or be stripped entirely. To quantitatively reproduce the observed features, we argue that not only do low-mass Kepler planets need to be made of rocky cores surrounded with hydrogen envelopes, but few of them should have initial masses above

A REVISED ESTIMATE OF THE OCCURRENCE RATE OF TERRESTRIAL PLANETS IN THE HABITABLE ZONES AROUND KEPLER M-DWARFS

International Nuclear Information System (INIS)

Kopparapu, Ravi Kumar

2013-01-01

Because of their large numbers, low-mass stars may be the most abundant planet hosts in our Galaxy. Furthermore, terrestrial planets in the habitable zones (HZs) around M-dwarfs can potentially be characterized in the near future and hence may be the first such planets to be studied. Recently, Dressing and Charbonneau used Kepler data and calculated the frequency of terrestrial planets in the HZ of cool stars to be 0.15 +0.13 -0.06 per star for Earth-size planets (0.5-1.4 R ⊕ ). However, this estimate was derived using the Kasting et al. HZ limits, which were not valid for stars with effective temperatures lower than 3700 K. Here we update their result using new HZ limits from Kopparapu et al. for stars with effective temperatures between 2600 K and 7200 K, which includes the cool M stars in the Kepler target list. The new HZ boundaries increase the number of planet candidates in the HZ. Assuming Earth-size planets as 0.5-1.4 R ⊕ , when we reanalyze their results, we obtain a terrestrial planet frequency of 0.48 +0.12 -0.24 and 0.53 +0.08 -0.17 planets per M-dwarf star for conservative and optimistic limits of the HZ boundaries, respectively. Assuming Earth-size planets as 0.5-2 R ⊕ , the frequency increases to 0.51 +0.10 -0.20 per star for the conservative estimate and to 0.61 +0.07 -0.15 per star for the optimistic estimate. Within uncertainties, our optimistic estimates are in agreement with a similar optimistic estimate from the radial velocity survey of M-dwarfs (0.41 +0.54 -0.13 ). So, the potential for finding Earth-like planets around M stars may be higher than previously reported.

Understanding Super-Earths with MINERVA-Australis at USQ's Mount Kent Observatory

Science.gov (United States)

Wittenmyer, Robert; Horner, Jonathan; Kane, Stephen; Plavchan, Peter; Ciardi, David; Eastman, Jason; Johnson, John Asher; Wright, Jason; McCrady, Nate; MINERVA Collaboration

2018-01-01

Super Earths, planets between 5-10 Earth masses, are the most common types of planets known, yet are completely absent from our Solar system. As a result, their detailed properties, compositions, and formation mechanisms are poorly understood. NASA's Transiting Exoplanet Survey Satellite (TESS) will identify hundreds of Super-Earths orbiting bright stars, for the first time allowing in-depth characterisation of these planets. At the University of Southern Queensland, we are host to the MINERVA-Australis project, dedicated wholly to the follow-up characterisation and mass measurement of TESS planets. We give an update on the status of MINERVA-Australis and our expected performance. We also present results from the fully operational Northern MINERVA array, with the primary mission of discovering rocky planets orbiting 80 nearby bright stars.

Extrasolar Planets: Towards Comparative Planetology beyond the Solar System

Science.gov (United States)

Khan, A. H.

2012-09-01

Today Scenario planet logy is a very important concept because now days the scientific research finding new and new planets and our work's range becoming too long. In the previous study shows about 10-12 years the research of planet logy now has changed . Few years ago we was talking about Sun planet, Earth planet , Moon ,Mars Jupiter & Venus etc. included but now the time has totally changed the recent studies showed that mono lakes California find the arsenic food use by micro organism that show that our study is very tiny as compare to planet long areas .We have very well known that arsenic is the toxic agent's and the toxic agent's present in the lakes and micro organism developing and life going on it's a unbelievable point for us but nature always play a magical games. In few years ago Aliens was the story no one believe the Aliens origin but now the aliens showed catch by our space craft and shuttle and every one believe that Aliens origin but at the moment's I would like to mention one point's that we have too more work required because our planet logy has a vast field. Most of the time our scientific mission shows that this planet found liquid oxygen ,this planet found hydrogen .I would like to clear that point's that all planet logy depend in to the chemical and these chemical gave the indication of the life but we are not abele to developed the adaptation according to the micro organism . Planet logy compare before study shows that Sun it's a combination of the various gases combination surrounded in a round form and now the central Sun Planets ,moons ,comets and asteroids In other word we can say that Or Sun has a wide range of the physical and Chemical properties in the after the development we can say that all chemical and physical property engaged with a certain environment and form a various contains like asteroids, moon, Comets etc. Few studies shows that other planet life affected to the out living planet .We can assure with the example the life

Identifying Exoplanets with Deep Learning: A Five-planet Resonant Chain around Kepler-80 and an Eighth Planet around Kepler-90

Science.gov (United States)

Shallue, Christopher J.; Vanderburg, Andrew

2018-02-01

NASA’s Kepler Space Telescope was designed to determine the frequency of Earth-sized planets orbiting Sun-like stars, but these planets are on the very edge of the mission’s detection sensitivity. Accurately determining the occurrence rate of these planets will require automatically and accurately assessing the likelihood that individual candidates are indeed planets, even at low signal-to-noise ratios. We present a method for classifying potential planet signals using deep learning, a class of machine learning algorithms that have recently become state-of-the-art in a wide variety of tasks. We train a deep convolutional neural network to predict whether a given signal is a transiting exoplanet or a false positive caused by astrophysical or instrumental phenomena. Our model is highly effective at ranking individual candidates by the likelihood that they are indeed planets: 98.8% of the time it ranks plausible planet signals higher than false-positive signals in our test set. We apply our model to a new set of candidate signals that we identified in a search of known Kepler multi-planet systems. We statistically validate two new planets that are identified with high confidence by our model. One of these planets is part of a five-planet resonant chain around Kepler-80, with an orbital period closely matching the prediction by three-body Laplace relations. The other planet orbits Kepler-90, a star that was previously known to host seven transiting planets. Our discovery of an eighth planet brings Kepler-90 into a tie with our Sun as the star known to host the most planets.

The Search for Another Earth – Part II

Indian Academy of Sciences (India)

In this part, we will describe various kinds of ... the Earth will also be discussed. 1. .... life. system is oxygen rich because the interstellar cloud from which the Sun and the solar planets were born .... a habitable planet must be rocky in order to sustain liquid ... helped in keeping the atmosphere of the Earth habitable for a long.

Bioremediation at a global scale: from the test tube to planet Earth.

Science.gov (United States)

de Lorenzo, Víctor; Marlière, Philippe; Solé, Ricard

2016-09-01

Planet Earth's biosphere has evolved over billions of years as a balanced bio-geological system ultimately sustained by sunpower and the large-scale cycling of elements largely run by the global environmental microbiome. Humans have been part of this picture for much of their existence. But the industrial revolution started in the XIX century and the subsequent advances in medicine, chemistry, agriculture and communications have impacted such balances to an unprecedented degree - and the problem has nothing but exacerbated in the last 20 years. Human overpopulation, industrial growth along with unsustainable use of natural resources have driven many sites and perhaps the planetary ecosystem as a whole, beyond recovery by spontaneous natural means, even if the immediate causes could be stopped. The most conspicuous indications of such a state of affairs include the massive change in land use, the accelerated increase in the levels of greenhouse gases, the frequent natural disasters associated to climate change and the growing non-recyclable waste (e.g. plastics and recalcitrant chemicals) that we release to the Environment. While the whole planet is afflicted at a global scale by chemical pollution and anthropogenic emissions, the ongoing development of systems and synthetic biology, metagenomics, modern chemistry and some key concepts from ecological theory allow us to tackle this phenomenal challenge and propose large-scale interventions aimed at reversing and even improving the situation. This involves (i) identification of key reactions or processes that need to be re-established (or altogether created) for ecosystem reinstallation, (ii) implementation of such reactions in natural or designer hosts able to self-replicate and deliver the corresponding activities when/where needed in a fashion guided by sound ecological modelling, (iii) dispersal of niche-creating agents at a global scale and (iv) containment, monitoring and risk assessment of the whole process

Atmospheric Circulations of Rocky Planets as Heat Engines

Science.gov (United States)

Koll, D. D. B.

2017-12-01

Rocky planets are extremely common in the galaxy and include Earth, Mars, Venus, and hundreds of exoplanets. To understand and compare the climates of these planets, we need theories that are general enough to accommodate drastically different atmospheric and planetary properties. Unfortunately, few such theories currently exist.For Earth, there is a well-known principle that its atmosphere resembles a heat engine - the atmosphere absorbs heat near the surface, at a hot temperature, and emits heat to space in the upper troposphere, at a cold temperature, which allows it to perform work and balance dissipative processes such as friction. However, previous studies also showed that Earth's hydrological cycle uses up a large fraction of the heat engine's work output, which makes it difficult to view other atmospheres as heat engines.In this work I extend the heat engine principle from Earth towards other rocky planets. I explore both dry and moist atmospheres in an idealized general circulation model (GCM), and quantify their work output using entropy budgets. First, I show that convection and turbulent heat diffusion are important entropy sources in dry atmospheres. I develop a scaling that accounts for its effects, which allows me to predict the strength of frictional dissipation in dry atmospheres. There are strong parallels between my scaling and so-called potential intensity theory, which is a seminal theory for understanding tropical cyclones on Earth. Second, I address how moisture affects atmospheric heat engines. Moisture modifies both the thermodynamic properties of air and releases latent heat when water vapor condenses. I explore the impact of both effects, and use numerical simulations to explore the difference between dry and moist atmospheric circulations across a wide range of climates.

Water cycling between ocean and mantle: Super-earths need not be waterworlds

International Nuclear Information System (INIS)

Cowan, Nicolas B.; Abbot, Dorian S.

2014-01-01

Large terrestrial planets are expected to have muted topography and deep oceans, implying that most super-Earths should be entirely covered in water, so-called waterworlds. This is important because waterworlds lack a silicate weathering thermostat so their climate is predicted to be less stable than that of planets with exposed continents. In other words, the continuously habitable zone for waterworlds is much narrower than for Earth-like planets. A planet's water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on geological timescales. Degassing of melt at mid-ocean ridges and serpentinization of oceanic crust depend negatively and positively on seafloor pressure, respectively, providing a stabilizing feedback on long-term ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere and derive steady-state solutions to the water partitioning on terrestrial planets. Critically, hydrostatic seafloor pressure is proportional to surface gravity, so super-Earths with a deep water cycle will tend to store more water in the mantle. We conclude that a tectonically active terrestrial planet of any mass can maintain exposed continents if its water mass fraction is less than ∼0.2%, dramatically increasing the odds that super-Earths are habitable. The greatest source of uncertainty in our study is Earth's current mantle water inventory: the greater its value, the more robust planets are to inundation. Lastly, we discuss how future missions can test our hypothesis by mapping the oceans and continents of massive terrestrial planets.

Water cycling between ocean and mantle: Super-earths need not be waterworlds

Energy Technology Data Exchange (ETDEWEB)

Cowan, Nicolas B. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Department of Earth and Planetary Sciences, Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Abbot, Dorian S., E-mail: n-cowan@northwestern.edu [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

2014-01-20

Large terrestrial planets are expected to have muted topography and deep oceans, implying that most super-Earths should be entirely covered in water, so-called waterworlds. This is important because waterworlds lack a silicate weathering thermostat so their climate is predicted to be less stable than that of planets with exposed continents. In other words, the continuously habitable zone for waterworlds is much narrower than for Earth-like planets. A planet's water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on geological timescales. Degassing of melt at mid-ocean ridges and serpentinization of oceanic crust depend negatively and positively on seafloor pressure, respectively, providing a stabilizing feedback on long-term ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere and derive steady-state solutions to the water partitioning on terrestrial planets. Critically, hydrostatic seafloor pressure is proportional to surface gravity, so super-Earths with a deep water cycle will tend to store more water in the mantle. We conclude that a tectonically active terrestrial planet of any mass can maintain exposed continents if its water mass fraction is less than ∼0.2%, dramatically increasing the odds that super-Earths are habitable. The greatest source of uncertainty in our study is Earth's current mantle water inventory: the greater its value, the more robust planets are to inundation. Lastly, we discuss how future missions can test our hypothesis by mapping the oceans and continents of massive terrestrial planets.

Evolution of the giant planets

International Nuclear Information System (INIS)

Bodenheimer, P.

1985-01-01

The theory of the evolution of the giant planets is discussed with emphasis on detailed numerical calculations in the spherical approximation. Initial conditions are taken to be those provided by the two main hypotheses for the origin of the giant planets. If the planets formed by gravitational instability in the solar nebula, the initial mass is comparable to the present mass or larger. The evolution then goes through the following phases: (1) an initial contraction phase in hydrostatic equilibrium; (2) a hydrodynamic collapse induced by molecular dissociation; and (3) a second equilibrium phase involving contraction and cooling to the present state. During phase (1) a rock-ice core must form by precipitation or accretion. If, on the other hand, the giant planets formed by first accreting a solid core and then capturing gas from the surrounding nebula, then the evolutionary phases are as follows: (1) a period during which planetesimals accrete to form a core of about one earth mass, composed of rock and ice; (2) a gas accretion phase, during which a relatively low-mass gaseous envelope in hydrostatic equilibrium exists around the core, which itself continues to grow to 10 to 20 Earth masses; (3) the point of arrival at the ''critical'' core mass at which point the accretion of gas is much faster than the accretion of the core, and the envelope contracts rapidly; (4) continuation of accretion of gas from the nebula and buildup of the envelope mass to its present value (for the case of Jupiter or Saturn); and (5) a final phase, after termination of accretion, during which the protoplanet contracts and cools to its present state. Some observational constraints are described, and some problems with the two principal hypotheses are discussed

Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities

Energy Technology Data Exchange (ETDEWEB)

Carter, J. A.; Agol, E.; Chaplin, W. J.; Basu, S.; Bedding, T. R.; Buchhave, L. A.; Christensen-Dalsgaard, J.; Deck, K. M.; Elsworth, Y.; Fabrycky, D. C.; Ford, E. B.; Fortney, J. J.; Hale, S. J.; Handberg, R.; Hekker, S.; Holman, M. J.; Huber, D.; Karoff, C.; Kawaler, S. D.; Kjeldsen, H.; Lissauer, J. J.; Lopez, E. D.; Lund, M. N.; Lundkvist, M.; Metcalfe, T. S.; Miglio, A.; Rogers, L. A.; Stello, D.; Borucki, W. J.; Bryson, S.; Christiansen, J. L.; Cochran, W. D.; Geary, J. C.; Gilliland, R. L.; Haas, M. R.; Hall, J.; Howard, A. W.; Jenkins, J. M.; Klaus, T.; Koch, D. G.; Latham, D. W.; MacQueen, P. J.; Sasselov, D.; Steffen, J. H.; Twicken, J. D.; Winn, J. N.

2012-06-21

In the Solar system the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal, and that planets' orbits can change substantially after their formation. Here we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10%, and densities differing by a factor of 8. One planet is likely a rocky `super-Earth', whereas the other is more akin to Neptune. These planets are thirty times more closely spaced--and have a larger density contrast--than any adjacent pair of planets in the Solar system.

Pervasive orbital eccentricities dictate the habitability of extrasolar earths.

Science.gov (United States)

Kita, Ryosuke; Rasio, Frederic; Takeda, Genya

2010-09-01

The long-term habitability of Earth-like planets requires low orbital eccentricities. A secular perturbation from a distant stellar companion is a very important mechanism in exciting planetary eccentricities, as many of the extrasolar planetary systems are associated with stellar companions. Although the orbital evolution of an Earth-like planet in a stellar binary system is well understood, the effect of a binary perturbation on a more realistic system containing additional gas-giant planets has been very little studied. Here, we provide analytic criteria confirmed by a large ensemble of numerical integrations that identify the initial orbital parameters leading to eccentric orbits. We show that an extrasolar earth is likely to experience a broad range of orbital evolution dictated by the location of a gas-giant planet, which necessitates more focused studies on the effect of eccentricity on the potential for life.

Stable Hydrogen-rich Atmospheres of Young Rocky Planets

Science.gov (United States)

Zahnle, K. J.; Catling, D. C.; Gacesa, M.

2016-12-01

SourceURL:file://localhost/Volumes/Lexar/Zahnle_AGU_2016.docx Understanding hydrogen escape is essential to understanding the limits to habitability, both for liquid water where the Sun is bright, but also to assess the true potential of H2 as a greenhouse gas where the Sun is faint. Hydrogen-rich primary atmospheres of Earth-like planets can result either from gravitational capture of solar nebular gases (with helium), or from impact shock processing of a wide variety of volatile-rich planetesimals (typically accompanied by H2O, CO2, and under the right circumstances, CH4). Most studies of hydrogen escape from planets focus on determining how fast the hydrogen escapes. In general this requires solving hydrodynamic equations that take into account the acceleration of hydrogen through a critical transonic point and an energy budget that should include radiative heating and cooling, thermal conduction, the work done in lifting the hydrogen against gravity, and the residual heat carried by the hydrogen as it leaves. But for planets from which hydrogen escape is modest or insignificant, the atmosphere can be approximated as hydrostatic, which is much simpler, and for which a relatively full-featured treatment of radiative cooling by embedded molecules, atoms, and ions such as CO2 and H3+ is straightforward. Previous work has overlooked the fact that the H2 molecule is extremely efficient at exciting non-LTE CO2 15 micron emission, and thus that radiative cooling can be markedly more efficient when H2 is abundant. We map out the region of phase space in which terrestrial planets keep hydrogen-rich atmospheres, which is what we actually want to know for habitability. We will use this framework to reassess Tian et al's (Science 308, pp. 1014-1017, 2005) hypothesis that H2-rich atmospheres may have been rather long-lived on Earth itself. Finally, we will address the empirical observation that rocky planets with thin or negligible atmospheres are rarely or never bigger than

Optimizing the TESS Planet Finding Pipeline

Science.gov (United States)

Chitamitara, Aerbwong; Smith, Jeffrey C.; Tenenbaum, Peter; TESS Science Processing Operations Center

2017-10-01

The Transiting Exoplanet Survey Satellite (TESS) is a new NASA planet finding all-sky survey that will observe stars within 200 light years and 10-100 times brighter than that of the highly successful Kepler mission. TESS is expected to detect ~1000 planets smaller than Neptune and dozens of Earth size planets. As in the Kepler mission, the Science Processing Operations Center (SPOC) processing pipeline at NASA Ames Research center is tasked with calibrating the raw pixel data, generating systematic error corrected light curves and then detecting and validating transit signals. The Transiting Planet Search (TPS) component of the pipeline must be modified and tuned for the new data characteristics in TESS. For example, due to each sector being viewed for as little as 28 days, the pipeline will be identifying transiting planets based on a minimum of two transit signals rather than three, as in the Kepler mission. This may result in a significantly higher false positive rate. The study presented here is to measure the detection efficiency of the TESS pipeline using simulated data. Transiting planets identified by TPS are compared to transiting planets from the simulated transit model using the measured epochs, periods, transit durations and the expected detection statistic of injected transit signals (expected MES). From the comparisons, the recovery and false positive rates of TPS is measured. Measurements of recovery in TPS are then used to adjust TPS configuration parameters to maximize the planet recovery rate and minimize false detections. The improvements in recovery rate between initial TPS conditions and after various adjustments will be presented and discussed.

MIGRATION THEN ASSEMBLY: FORMATION OF NEPTUNE-MASS PLANETS INSIDE 1 AU

International Nuclear Information System (INIS)

Hansen, Brad M. S.; Murray, Norm

2012-01-01

We demonstrate that the observed distribution of 'hot Neptune'/'super-Earth' systems is well reproduced by a model in which planet assembly occurs in situ, with no significant migration post-assembly. This is achieved only if the amount of mass in rocky material is ∼50-100 M ⊕ interior to 1 AU. Such a reservoir of material implies that significant radial migration of solid material takes place, and that it occurs before the stage of final planet assembly. The model not only reproduces the general distribution of mass versus period but also the detailed statistics of multiple planet systems in the sample. We furthermore demonstrate that cores of this size are also likely to meet the criterion to gravitationally capture gas from the nebula, although accretion is rapidly limited by the opening of gaps in the gas disk. If the mass growth is limited by this tidal truncation, then the scenario sketched here naturally produces Neptune-mass objects with substantial components of both rock and gas, as is observed. The quantitative expectations of this scenario are that most planets in the 'hot Neptune/super-Earth' class inhabit multiple-planet systems, with characteristic orbital spacings. The model also provides a natural division into gas-rich (hot Neptune) and gas-poor (super-Earth) classes at fixed period. The dividing mass ranges from ∼3 M ⊕ at 10 day orbital periods to ∼10 M ⊕ at 100 day orbital periods. For orbital periods <10 days, the division is less clear because a gas atmosphere may be significantly eroded by stellar radiation.

The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Near the Habitable Zone of a Wide Range of Stars

Science.gov (United States)

Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.

1997-01-01

The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change. in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours. From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg. field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.

The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Neat the Habitable Zone of a Wide Range of Stars

Science.gov (United States)

Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.; Young, Richard E. (Technical Monitor)

1997-01-01

The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours, From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.

TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS

International Nuclear Information System (INIS)

Agol, Eric

2011-01-01

To date the search for habitable Earth-like planets has primarily focused on nuclear burning stars. I propose that this search should be expanded to cool white dwarf stars that have expended their nuclear fuel. I define the continuously habitable zone of white dwarfs and show that it extends from ∼0.005 to 0.02 AU for white dwarfs with masses from 0.4 to 0.9 M sun , temperatures less than ∼10 4 K, and habitable durations of at least 3 Gyr. As they are similar in size to Earth, white dwarfs may be deeply eclipsed by terrestrial planets that orbit edge-on, which can easily be detected with ground-based telescopes. If planets can migrate inward or reform near white dwarfs, I show that a global robotic telescope network could carry out a transit survey of nearby white dwarfs placing interesting constraints on the presence of habitable Earths. If planets were detected, I show that the survey would favor detection of planets similar to Earth: similar size, temperature, and rotation period, and host star temperatures similar to the Sun. The Large Synoptic Survey Telescope could place even tighter constraints on the frequency of habitable Earths around white dwarfs. The confirmation and characterization of these planets might be carried out with large ground and space telescopes.

How life shaped Earth.

Science.gov (United States)

Gross, Michael

2015-10-05

Earth is much more complex than all the other solar system objects that we know. Thanks to its rich and diverse geology, our planet can offer habitats to a wide range of living species. Emerging insights suggest that this is not just a happy coincidence, but that life itself has in many ways helped to shape the planet.