Capture of terrestrial-sized moons by gas giant planets.

Science.gov (United States)

Williams, Darren M

2013-04-01

Terrestrial moons with masses >0.1 M (symbol in text) possibly exist around extrasolar giant planets, and here we consider the energetics of how they might form. Binary-exchange capture can occur if a binary-terrestrial object (BTO) is tidally disrupted during a close encounter with a giant planet and one of the binary members is ejected while the other remains as a moon. Tidal disruption occurs readily in the deep gravity wells of giant planets; however, the large encounter velocities in the wells make binary exchange more difficult than for planets of lesser mass. In addition, successful capture favors massive binaries with large rotational velocities and small component mass ratios. Also, since the interaction tends to leave the captured moons on highly elliptical orbits, permanent capture is only possible around planets with sizable Hill spheres that are well separated from their host stars.

TERRESTRIAL PLANET FORMATION FROM AN ANNULUS

Energy Technology Data Exchange (ETDEWEB)

Walsh, Kevin J.; Levison, Harold F., E-mail: kwalsh@boulder.swri.edu [Southwest Research Institute, 1050 Walnut St. Suite 300, Boulder, CO 80302 (United States)

2016-09-01

It has been shown that some aspects of the terrestrial planets can be explained, particularly the Earth/Mars mass ratio, when they form from a truncated disk with an outer edge near 1.0 au. This has been previously modeled starting from an intermediate stage of growth utilizing pre-formed planetary embryos. We present simulations that were designed to test this idea by following the growth process from km-sized objects located between 0.7 and 1.0 au up to terrestrial planets. The simulations explore initial conditions where the solids in the disk are planetesimals with radii initially between 3 and 300 km, alternately including effects from a dissipating gaseous solar nebula and collisional fragmentation. We use a new Lagrangian code known as LIPAD, which is a particle-based code that models the fragmentation, accretion, and dynamical evolution of a large number of planetesimals, and can model the entire growth process from km-sizes up to planets. A suite of large (∼ Mars mass) planetary embryos is complete in only ∼1 Myr, containing most of the system mass. A quiescent period then persists for 10–20 Myr characterized by slow diffusion of the orbits and continued accretion of the remaining planetesimals. This is interrupted by an instability that leads to embryos crossing orbits and embryo–embryo impacts that eventually produce the final set of planets. While this evolution is different than that found in other works exploring an annulus, the final planetary systems are similar, with roughly the correct number of planets and good Mars-analogs.

Filled aperture concepts for the Terrestrial Planet Finder

Science.gov (United States)

Ridgway, Stephen T.

2003-02-01

Filled aperture telescopes can deliver a real, high Strehl image which is well suited for discrimination of faint planets in the vicinity of bright stars and against an extended exo-zodiacal light. A filled aperture offers a rich variety of PSF control and diffraction suppression techniques. Filled apertures are under consideration for a wide spectral range, including visible and thermal-IR, each of which offers a significant selection of biomarker molecular bands. A filled aperture visible TPF may be simpler in several respects than a thermal-IR nuller. The required aperture size (or baseline) is much smaller, and no cryogenic systems are required. A filled aperture TPF would look and act like a normal telescope - vendors and users alike would be comfortable with its design and operation. Filled aperture telescopes pose significant challenges in production of large primary mirrors, and in very stringent wavefront requirements. Stability of the wavefront control, and hence of the PSF, is a major issue for filled aperture systems. Several groups have concluded that these and other issues can be resolved, and that filled aperture options are competitive for a TPF precursor and/or for the full TPF mission. Ball, Boeing-SVS and TRW have recently returned architecture reviews on filled aperture TPF concepts. In this paper, I will review some of the major considerations underlying these filled aperture concepts, and suggest key issues in a TPF Buyers Guide.

Tc Trends and Terrestrial Planet Formation: The Case of Zeta Reticuli

Science.gov (United States)

Adibekyan, Vardan; Delgado-Mena, Elisa; Figueira, Pedro; Sousa, Sergio; Santos, Nuno; Faria, Joao; González Hernández, Jonay; Israelian, Garik; Harutyunyan, Gohar; Suárez-Andrés, Lucia; Hakobyan, Artur

2016-11-01

During the last decade astronomers have been trying to search for chemical signatures of terrestrial planet formation in the atmospheres of the hosting stars. Several studies suggested that the chemical abundance trend with the condensation temperature, Tc, is a signature of rocky planet formation. In particular, it was suggested that the Sun shows 'peculiar' chemical abundances due to the presence of the terrestrial planets in our solar-system. However, the rocky material accretion or the trap of rocky materials in terrestrial planets is not the only explanation for the chemical 'peculiarity' of the Sun, or other Sun-like stars with planets. In this talk I madea very brief review of this topic, and presented our last results for the particular case of Zeta Reticuli binary system: A very interesting and well-known system (known in science fiction and ufology as the world of Grey Aliens, or Reticulans) where one of the components hosts an exo-Kuiper belt, and the other component is a 'single', 'lonely' star.

Debris disks as signposts of terrestrial planet formation. II. Dependence of exoplanet architectures on giant planet and disk properties

Science.gov (United States)

Raymond, S. N.; Armitage, P. J.; Moro-Martín, A.; Booth, M.; Wyatt, M. C.; Armstrong, J. C.; Mandell, A. M.; Selsis, F.; West, A. A.

2012-05-01

We present models for the formation of terrestrial planets, and the collisional evolution of debris disks, in planetary systems that contain multiple marginally unstable gas giants. We previously showed that in such systems, the dynamics of the giant planets introduces a correlation between the presence of terrestrial planets and cold dust, i.e., debris disks, which is particularly pronounced at λ ~ 70 μm. Here we present new simulations that show that this connection is qualitatively robust to a range of parameters: the mass distribution of the giant planets, the width and mass distribution of the outer planetesimal disk, and the presence of gas in the disk when the giant planets become unstable. We discuss how variations in these parameters affect the evolution. We find that systems with equal-mass giant planets undergo the most violent instabilities, and that these destroy both terrestrial planets and the outer planetesimal disks that produce debris disks. In contrast, systems with low-mass giant planets efficiently produce both terrestrial planets and debris disks. A large fraction of systems with low-mass (M ≲ 30 M⊕) outermost giant planets have final planetary separations that, scaled to the planets' masses, are as large or larger than the Saturn-Uranus and Uranus-Neptune separations in the solar system. We find that the gaps between these planets are not only dynamically stable to test particles, but are frequently populated by planetesimals. The possibility of planetesimal belts between outer giant planets should be taken into account when interpreting debris disk SEDs. In addition, the presence of ~ Earth-mass "seeds" in outer planetesimal disks causes the disks to radially spread to colder temperatures, and leads to a slow depletion of the outer planetesimal disk from the inside out. We argue that this may explain the very low frequency of >1 Gyr-old solar-type stars with observed 24 μm excesses. Our simulations do not sample the full range of

Origin and evolution of life on terrestrial planets.

Science.gov (United States)

Brack, A; Horneck, G; Cockell, C S; Bérces, A; Belisheva, N K; Eiroa, Carlos; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Léger, Alain; Liseau, Réne; Lammer, Helmut; Selsis, Franck; Beichman, Charles; Danchi, William; Fridlund, Malcolm; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

2010-01-01

The ultimate goal of terrestrial planet-finding missions is not only to discover terrestrial exoplanets inside the habitable zone (HZ) of their host stars but also to address the major question as to whether life may have evolved on a habitable Earth-like exoplanet outside our Solar System. We note that the chemical evolution that finally led to the origin of life on Earth must be studied if we hope to understand the principles of how life might evolve on other terrestrial planets in the Universe. This is not just an anthropocentric point of view: the basic ingredients of terrestrial life, that is, reduced carbon-based molecules and liquid H(2)O, have very specific properties. We discuss the origin of life from the chemical evolution of its precursors to the earliest life-forms and the biological implications of the stellar radiation and energetic particle environments. Likewise, the study of the biological evolution that has generated the various life-forms on Earth provides clues toward the understanding of the interconnectedness of life with its environment.

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.

DECIPHERING THERMAL PHASE CURVES OF DRY, TIDALLY LOCKED TERRESTRIAL PLANETS

Energy Technology Data Exchange (ETDEWEB)

Koll, Daniel D. B.; Abbot, Dorian S., E-mail: dkoll@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States)

2015-03-20

Next-generation space telescopes will allow us to characterize terrestrial exoplanets. To do so effectively it will be crucial to make use of all available data. We investigate which atmospheric properties can, and cannot, be inferred from the broadband thermal phase curve of a dry and tidally locked terrestrial planet. First, we use dimensional analysis to show that phase curves are controlled by six nondimensional parameters. Second, we use an idealized general circulation model to explore the relative sensitivity of phase curves to these parameters. We find that the feature of phase curves most sensitive to atmospheric parameters is the peak-to-trough amplitude. Moreover, except for hot and rapidly rotating planets, the phase amplitude is primarily sensitive to only two nondimensional parameters: (1) the ratio of dynamical to radiative timescales and (2) the longwave optical depth at the surface. As an application of this technique, we show how phase curve measurements can be combined with transit or emission spectroscopy to yield a new constraint for the surface pressure and atmospheric mass of terrestrial planets. We estimate that a single broadband phase curve, measured over half an orbit with the James Webb Space Telescope, could meaningfully constrain the atmospheric mass of a nearby super-Earth. Such constraints will be important for studying the atmospheric evolution of terrestrial exoplanets as well as characterizing the surface conditions on potentially habitable planets.

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 PROJECT: an Observatory / Transport Spaceship for Discovering and Populating Habitable Extrasolar Terrestrial Planets

Science.gov (United States)

Kilston, S.

1998-12-01

Recent extrasolar planet discoveries and related progress in astrophysics have refined our knowledge of the implications of the Drake equation. The Space Interferometry Mission and the planned Terrestrial Planet Finder will deepen this understanding, and begin pointing the way to places we need to explore at closer range. If the correct resolution of the Fermi paradox regarding intelligent extraterrestrials (``where are they?") is found to lie in the actual scarcity of such beings, it may turn out that we are more advanced than most other life-forms in our galaxy. In this case, a main purpose in finding planets may be to find places for us to go: astronomy will once again play a major role in human navigation and migration. We describe a strawman design concept for an astronomical observatory ship designed for launch beyond our solar system within several hundred years. This ship design would employ plausible physics, biology, technology, sociology, and economics to carry one million passengers in a one-G environment shielded from space radiation. A cruising speed under 0.01 c, slower than in many science-fiction concepts, minimizes power requirements and the danger from collisional impacts. The ship would contain all subsystems needed to sustain multi-generational life on a voyage of thousands of years, as well as the observatories to identify for human settlement a habitable extrasolar planet. Even the modestly advanced technology described here could spread intelligent life throughout our galaxy within 40 million years, a very small fraction of the galaxy's age. Motivation for such an ambitious project is three-fold: expanding our knowledge of the universe, enlisting the efforts and enthusiasms of humankind toward a very grand goal which will stimulate progress in all aspects of our cultures and technologies, and participating in the process of spreading life so its survivability and fruition are enhanced.

EFFECTS OF DYNAMICAL EVOLUTION OF GIANT PLANETS ON SURVIVAL OF TERRESTRIAL PLANETS

International Nuclear Information System (INIS)

Matsumura, Soko; Ida, Shigeru; Nagasawa, Makiko

2013-01-01

The orbital distributions of currently observed extrasolar giant planets allow marginally stable orbits for hypothetical, terrestrial planets. In this paper, we propose that many of these systems may not have additional planets on these ''stable'' orbits, since past dynamical instability among giant planets could have removed them. We numerically investigate the effects of early evolution of multiple giant planets on the orbital stability of the inner, sub-Neptune-like planets which are modeled as test particles, and determine their dynamically unstable region. Previous studies have shown that the majority of such test particles are ejected out of the system as a result of close encounters with giant planets. Here, we show that secular perturbations from giant planets can remove test particles at least down to 10 times smaller than their minimum pericenter distance. Our results indicate that, unless the dynamical instability among giant planets is either absent or quiet like planet-planet collisions, most test particles down to ∼0.1 AU within the orbits of giant planets at a few AU may be gone. In fact, out of ∼30% of survived test particles, about three quarters belong to the planet-planet collision cases. We find a good agreement between our numerical results and the secular theory, and present a semi-analytical formula which estimates the dynamically unstable region of the test particles just from the evolution of giant planets. Finally, our numerical results agree well with the observations, and also predict the existence of hot rocky planets in eccentric giant planet systems.

Strategies for Constraining the Atmospheres of Temperate Terrestrial Planets with JWST

Science.gov (United States)

Batalha, Natasha E.; Lewis, Nikole K.; Line, Michael R.; Valenti, Jeff; Stevenson, Kevin

2018-04-01

The Transiting Exoplanet Survey Satellite (TESS) is expected to discover dozens of temperate terrestrial planets orbiting M-dwarfs with atmospheres that could be followed up with the James Webb Space Telescope (JWST). Currently, the TRAPPIST-1 system serves as a benchmark for determining the feasibility and resources required to yield atmospheric constraints. We assess these questions and leverage an information content analysis to determine observing strategies for yielding high-precision spectroscopy in transmission and emission. Our goal is to guide observing strategies of temperate terrestrial planets in preparation for the early JWST cycles. First, we explore JWST’s current capabilities and expected spectral precision for targets near the saturation limits of specific modes. In doing so, we highlight the enhanced capabilities of high-efficiency readout patterns that are being considered for implementation in Cycle 2. We propose a partial saturation strategy to increase the achievable precision of JWST's NIRSpec Prism. We show that JWST has the potential to detect the dominant absorbing gas in the atmospheres of temperate terrestrial planets by the 10th transit using transmission spectroscopy techniques in the near-infrared (NIR). We also show that stacking ⪆10 transmission spectroscopy observations is unlikely to yield significant improvements in determining atmospheric composition. For emission spectroscopy, we show that the MIRI Low Resolution Spectroscopy (LRS) is unlikely to provide robust constraints on the atmospheric composition of temperate terrestrial planets. Higher-precision emission spectroscopy at wavelengths longward of those accessible to MIRI LRS, as proposed in the Origins Space Telescope concept, could help improve the constraints on molecular abundances of temperate terrestrial planets orbiting M-dwarfs.

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.

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.

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.

Terrestrial Planet Formation: Dynamical Shake-up and the Low Mass of Mars

Science.gov (United States)

Bromley, Benjamin C.; Kenyon, Scott J.

2017-05-01

We consider a dynamical shake-up model to explain the low mass of Mars and the lack of planets in the asteroid belt. In our scenario, a secular resonance with Jupiter sweeps through the inner solar system as the solar nebula depletes, pitting resonant excitation against collisional damping in the Sun’s protoplanetary disk. We report the outcome of extensive numerical calculations of planet formation from planetesimals in the terrestrial zone, with and without dynamical shake-up. If the Sun’s gas disk within the terrestrial zone depletes in roughly a million years, then the sweeping resonance inhibits planet formation in the asteroid belt and substantially limits the size of Mars. This phenomenon likely occurs around other stars with long-period massive planets, suggesting that asteroid belt analogs are common.

Lunar and terrestrial planet formation in the Grand Tack scenario

Science.gov (United States)

Jacobson, S. A.; Morbidelli, A.

2014-01-01

We present conclusions from a large number of N-body simulations of the giant impact phase of terrestrial planet formation. We focus on new results obtained from the recently proposed Grand Tack model, which couples the gas-driven migration of giant planets to the accretion of the terrestrial planets. The giant impact phase follows the oligarchic growth phase, which builds a bi-modal mass distribution within the disc of embryos and planetesimals. By varying the ratio of the total mass in the embryo population to the total mass in the planetesimal population and the mass of the individual embryos, we explore how different disc conditions control the final planets. The total mass ratio of embryos to planetesimals controls the timing of the last giant (Moon-forming) impact and its violence. The initial embryo mass sets the size of the lunar impactor and the growth rate of Mars. After comparing our simulated outcomes with the actual orbits of the terrestrial planets (angular momentum deficit, mass concentration) and taking into account independent geochemical constraints on the mass accreted by the Earth after the Moon-forming event and on the time scale for the growth of Mars, we conclude that the protoplanetary disc at the beginning of the giant impact phase must have had most of its mass in Mars-sized embryos and only a small fraction of the total disc mass in the planetesimal population. From this, we infer that the Moon-forming event occurred between approximately 60 and approximately 130 Myr after the formation of the first solids and was caused most likely by an object with a mass similar to that of Mars. PMID:25114304

Conditions of Passage and Entrapment of Terrestrial Planets in Spin-Orbit Resonances

Science.gov (United States)

2012-06-10

May 25 ABSTRACT The dynamical evolution of terrestrial planets resembling Mercury in the vicinity of spin-orbit resonances is investigated using... planet and assuming a zero obliquity. We find that a Mercury -like planet with a current value of orbital eccentricity (0.2056) is always captured in... Mercury rarely fails to align itself into this state of unstable equilibrium before it traverses 2:1 resonance. Key words: celestial mechanics – planets

Workshop on Oxygen in the Terrestrial Planets

Science.gov (United States)

2004-01-01

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in

The origin of methane and biomolecules from a CO2 cycle on terrestrial planets

Science.gov (United States)

Civiš, Svatopluk; Knížek, Antonín; Ivanek, Ondřej; Kubelík, Petr; Zukalová, Markéta; Kavan, Ladislav; Ferus, Martin

2017-10-01

Understanding the chemical evolution of newly formed terrestrial planets involves uncertainties in atmospheric chemical composition and assessing the plausibility of biomolecule synthesis. In this study, an original scenario for the origin of methane on Mars and terrestrial planets is suggested. Carbon dioxide in Martian and other planetary atmospheres can be abiotically converted into a mixture of methane and carbon monoxide by `methanogenesis' on porous mineral photoactive surfaces under soft ultraviolet irradiation. On young planets exposed to heavy bombardment by interplanetary matter, this process can be followed by biomolecule synthesis through the reprocessing of reactive reducing atmospheres by impact-induced shock waves. The proposed mechanism of methanogenesis may help to answer the question concerning the formation of methane and carbon monoxide by photochemical processes, the formation of biomolecules on early Earth and other terrestrial planets, and the source and seasonal variation of methane concentrations on Mars.

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

ON THE MIGRATION OF JUPITER AND SATURN: CONSTRAINTS FROM LINEAR MODELS OF SECULAR RESONANT COUPLING WITH THE TERRESTRIAL PLANETS

International Nuclear Information System (INIS)

Agnor, Craig B.; Lin, D. N. C.

2012-01-01

We examine how the late divergent migration of Jupiter and Saturn may have perturbed the terrestrial planets. Using a modified secular model we have identified six secular resonances between the ν 5 frequency of Jupiter and Saturn and the four apsidal eigenfrequencies of the terrestrial planets (g 1-4 ). We derive analytic upper limits on the eccentricity and orbital migration timescale of Jupiter and Saturn when these resonances were encountered to avoid perturbing the eccentricities of the terrestrial planets to values larger than the observed ones. Because of the small amplitudes of the j = 2, 3 terrestrial eigenmodes the g 2 – ν 5 and g 3 – ν 5 resonances provide the strongest constraints on giant planet migration. If Jupiter and Saturn migrated with eccentricities comparable to their present-day values, smooth migration with exponential timescales characteristic of planetesimal-driven migration (τ ∼ 5-10 Myr) would have perturbed the eccentricities of the terrestrial planets to values greatly exceeding the observed ones. This excitation may be mitigated if the eccentricity of Jupiter was small during the migration epoch, migration was very rapid (e.g., τ ∼< 0.5 Myr perhaps via planet-planet scattering or instability-driven migration) or the observed small eccentricity amplitudes of the j = 2, 3 terrestrial modes result from low probability cancellation of several large amplitude contributions. Results of orbital integrations show that very short migration timescales (τ < 0.5 Myr), characteristic of instability-driven migration, may also perturb the terrestrial planets' eccentricities by amounts comparable to their observed values. We discuss the implications of these constraints for the relative timing of terrestrial planet formation, giant planet migration, and the origin of the so-called Late Heavy Bombardment of the Moon 3.9 ± 0.1 Ga ago. We suggest that the simplest way to satisfy these dynamical constraints may be for the bulk of any giant

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…

Chemistry in an evolving protoplanetary disk: Effects on terrestrial planet composition

International Nuclear Information System (INIS)

Moriarty, John; Fischer, Debra; Madhusudhan, Nikku

2014-01-01

The composition of planets is largely determined by the chemical and dynamical evolution of the disk during planetesimal formation and growth. To predict the diversity of exoplanet compositions, previous works modeled planetesimal composition as the equilibrium chemical composition of a protoplanetary disk at a single time. However, planetesimals form over an extended period of time, during which elements sequentially condense out of the gas as the disk cools and are accreted onto planetesimals. To account for the evolution of the disk during planetesimal formation, we couple models of disk chemistry and dynamics with a prescription for planetesimal formation. We then follow the growth of these planetesimals into terrestrial planets with N-body simulations of late-stage planet formation to evaluate the effect of sequential condensation on the bulk composition of planets. We find that our model produces results similar to those of earlier models for disks with C/O ratios close to the solar value (0.54). However, in disks with C/O ratios greater than 0.8, carbon-rich planetesimals form throughout a much larger radial range of the disk. Furthermore, our model produces carbon-rich planetesimals in disks with C/O ratios as low as ∼0.65, which is not possible in the static equilibrium chemistry case. These results suggest that (1) there may be a large population of short-period carbon-rich planets around moderately carbon-enhanced stars (0.65 < C/O < 0.8) and (2) carbon-rich planets can form throughout the terrestrial planet region around carbon-rich stars (C/O > 0.8).

ANALYSIS OF TERRESTRIAL PLANET FORMATION BY THE GRAND TACK MODEL: SYSTEM ARCHITECTURE AND TACK LOCATION

Energy Technology Data Exchange (ETDEWEB)

Brasser, R.; Ida, S. [Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550 (Japan); Matsumura, S. [School of Science and Engineering, Division of Physics, Fulton Building, University of Dundee, Dundee DD1 4HN (United Kingdom); Mojzsis, S. J. [Collaborative for Research in Origins (CRiO), Department of Geological Sciences, University of Colorado, UCB 399, 2200 Colorado Avenue, Boulder, Colorado 80309-0399 (United States); Werner, S. C. [The Centre for Earth Evolution and Dynamics, University of Oslo, Sem Saelandsvei 24, NO-0371 Oslo (Norway)

2016-04-20

The Grand Tack model of terrestrial planet formation has emerged in recent years as the premier scenario used to account for several observed features of the inner solar system. It relies on the early migration of the giant planets to gravitationally sculpt and mix the planetesimal disk down to ∼1 au, after which the terrestrial planets accrete from material remaining in a narrow circumsolar annulus. Here, we investigate how the model fares under a range of initial conditions and migration course-change (“tack”) locations. We run a large number of N-body simulations with tack locations of 1.5 and 2 au and test initial conditions using equal-mass planetary embryos and a semi-analytical approach to oligarchic growth. We make use of a recent model of the protosolar disk that takes into account viscous heating, includes the full effect of type 1 migration, and employs a realistic mass–radius relation for the growing terrestrial planets. Our results show that the canonical tack location of Jupiter at 1.5 au is inconsistent with the most massive planet residing at 1 au at greater than 95% confidence. This favors a tack farther out at 2 au for the disk model and parameters employed. Of the different initial conditions, we find that the oligarchic case is capable of statistically reproducing the orbital architecture and mass distribution of the terrestrial planets, while the equal-mass embryo case is not.

Large impacts around a solar-analog star in the era of terrestrial planet formation.

Science.gov (United States)

Meng, Huan Y A; Su, Kate Y L; Rieke, George H; Stevenson, David J; Plavchan, Peter; Rujopakarn, Wiphu; Lisse, Carey M; Poshyachinda, Saran; Reichart, Daniel E

2014-08-29

The final assembly of terrestrial planets occurs via massive collisions, which can launch copious clouds of dust that are warmed by the star and glow in the infrared. We report the real-time detection of a debris-producing impact in the terrestrial planet zone around a 35-million-year-old solar-analog star. We observed a substantial brightening of the debris disk at a wavelength of 3 to 5 micrometers, followed by a decay over a year, with quasi-periodic modulations of the disk flux. The behavior is consistent with the occurrence of a violent impact that produced vapor out of which a thick cloud of silicate spherules condensed that were then ground into dust by collisions. These results demonstrate how the time domain can become a new dimension for the study of terrestrial planet formation. Copyright © 2014, American Association for the Advancement of Science.

EFFECTS OF DYNAMICAL EVOLUTION OF GIANT PLANETS ON THE DELIVERY OF ATMOPHILE ELEMENTS DURING TERRESTRIAL PLANET FORMATION

Energy Technology Data Exchange (ETDEWEB)

Matsumura, Soko [School of Engineering, Physics, and Mathematics, University of Dundee, DD1 4HN, Scotland (United Kingdom); Brasser, Ramon; Ida, Shigeru, E-mail: s.matsumura@dundee.ac.uk [Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550 (Japan)

2016-02-10

Recent observations started revealing the compositions of protostellar disks and planets beyond the solar system. In this paper, we explore how the compositions of terrestrial planets are affected by the dynamical evolution of giant planets. We estimate the initial compositions of the building blocks of these rocky planets by using a simple condensation model, and numerically study the compositions of planets formed in a few different formation models of the solar system. We find that the abundances of refractory and moderately volatile elements are nearly independent of formation models, and that all the models could reproduce the abundances of these elements of the Earth. The abundances of atmophile elements, on the other hand, depend on the scattering rate of icy planetesimals into the inner disk, as well as the mixing rate of the inner planetesimal disk. For the classical formation model, neither of these mechanisms are efficient and the accretion of atmophile elements during the final assembly of terrestrial planets appears to be difficult. For the Grand Tack model, both of these mechanisms are efficient, which leads to a relatively uniform accretion of atmophile elements in the inner disk. It is also possible to have a “hybrid” scenario where the mixing is not very efficient but the scattering is efficient. The abundances of atmophile elements in this case increase with orbital radii. Such a scenario may occur in some of the extrasolar planetary systems, which are not accompanied by giant planets or those without strong perturbations from giants. We also confirm that the Grand Tack scenario leads to the distribution of asteroid analogues where rocky planetesimals tend to exist interior to icy ones, and show that their overall compositions are consistent with S-type and C-type chondrites, respectively.

EFFECTS OF DYNAMICAL EVOLUTION OF GIANT PLANETS ON THE DELIVERY OF ATMOPHILE ELEMENTS DURING TERRESTRIAL PLANET FORMATION

International Nuclear Information System (INIS)

Matsumura, Soko; Brasser, Ramon; Ida, Shigeru

2016-01-01

Recent observations started revealing the compositions of protostellar disks and planets beyond the solar system. In this paper, we explore how the compositions of terrestrial planets are affected by the dynamical evolution of giant planets. We estimate the initial compositions of the building blocks of these rocky planets by using a simple condensation model, and numerically study the compositions of planets formed in a few different formation models of the solar system. We find that the abundances of refractory and moderately volatile elements are nearly independent of formation models, and that all the models could reproduce the abundances of these elements of the Earth. The abundances of atmophile elements, on the other hand, depend on the scattering rate of icy planetesimals into the inner disk, as well as the mixing rate of the inner planetesimal disk. For the classical formation model, neither of these mechanisms are efficient and the accretion of atmophile elements during the final assembly of terrestrial planets appears to be difficult. For the Grand Tack model, both of these mechanisms are efficient, which leads to a relatively uniform accretion of atmophile elements in the inner disk. It is also possible to have a “hybrid” scenario where the mixing is not very efficient but the scattering is efficient. The abundances of atmophile elements in this case increase with orbital radii. Such a scenario may occur in some of the extrasolar planetary systems, which are not accompanied by giant planets or those without strong perturbations from giants. We also confirm that the Grand Tack scenario leads to the distribution of asteroid analogues where rocky planetesimals tend to exist interior to icy ones, and show that their overall compositions are consistent with S-type and C-type chondrites, respectively

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.

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.

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.

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.

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 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.)

Water loss from terrestrial planets with CO{sub 2}-rich atmospheres

Energy Technology Data Exchange (ETDEWEB)

Wordsworth, R. D.; Pierrehumbert, R. T., E-mail: rwordsworth@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, 60637 IL (United States)

2013-12-01

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{sub 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{sub 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{sub 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{sup –2} (global mean) unlikely to lose more than one Earth ocean of H{sub 2}O over their lifetimes unless they lose all their atmospheric N{sub 2}/CO{sub 2} early on. Because of the variability of H{sub 2}O delivery during accretion, our results suggest that many 'Earth-like' exoplanets in the habitable zone may have ocean-covered surfaces, stable CO{sub 2}/H{sub 2}O-rich atmospheres, and high mean surface temperatures.

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.

Accurate Treatment of Collisions and Water-Delivery in Models of Terrestrial Planet Formation

Science.gov (United States)

Haghighipour, Nader; Maindl, Thomas; Schaefer, Christoph

2017-10-01

It is widely accepted that collisions among solid bodies, ignited by their interactions with planetary embryos is the key process in the formation of terrestrial planets and transport of volatiles and chemical compounds to their accretion zones. Unfortunately, due to computational complexities, these collisions are often treated in a rudimentary way. Impacts are considered to be perfectly inelastic and volatiles are considered to be fully transferred from one object to the other. This perfect-merging assumption has profound effects on the mass and composition of final planetary bodies as it grossly overestimates the masses of these objects and the amounts of volatiles and chemical elements transferred to them. It also entirely neglects collisional-loss of volatiles (e.g., water) and draws an unrealistic connection between these properties and the chemical structure of the protoplanetary disk (i.e., the location of their original carriers). We have developed a new and comprehensive methodology to simulate growth of embryos to planetary bodies where we use a combination of SPH and N-body codes to accurately model collisions as well as the transport/transfer of chemical compounds. Our methodology accounts for the loss of volatiles (e.g., ice sublimation) during the orbital evolution of their careers and accurately tracks their transfer from one body to another. Results of our simulations show that traditional N-body modeling of terrestrial planet formation overestimates the amount of the mass and water contents of the final planets by over 60% implying that not only the amount of water they suggest is far from being realistic, small planets such as Mars can also form in these simulations when collisions are treated properly. We will present details of our methodology and discuss its implications for terrestrial planet formation and water delivery to Earth.

Refractory Abundances of Terrestrial Planets and Their Stars: Testing [Si/Fe] Correlations with TESS and PLATO

Science.gov (United States)

Wolfgang, Angie; Fortney, Jonathan

2018-01-01

In standard models for planet formation, solid material in protoplanetary disks coagulate and collide to form rocky bodies. It therefore seems reasonable to assume that their chemical composition will follow the abundances of refractory elements, such as Si and Fe, in the host star, which has also accreted material from the disk. Backed by planet formation simulations which validate this assumption, planetary internal structure models have begun to use stellar abundances to break degeneracies in low-mass planet compositions inferred only from mass and radius. Inconveniently, our own Solar System contradicts this approach, as its terrestrial bodies exhibit a range of rock/iron ratios and the Sun's [Si/Fe] ratio is offset from the mean planetary [Si/Fe]. In this work, we explore what number and quality of observations we need to empirically measure the exoplanet-star [Si/Fe] correlation, given future transit missions, RV follow-up, and stellar characterization. Specifically, we generate synthetic datasets of terrestrial planet masses and radii and host star abundances assuming that the planets’ bulk [Si/Fe] ratio exactly tracks that of their host stars. We assign measurement uncertainties corresponding to expected precisions for TESS, PLATO, Gaia, and future RV instrumentation, and then invert the problem to infer the planet-star [Si/Fe] correlation given these observational constraints. Comparing the result to the generated truth, we find that 1% precision on the planet radii is needed to test whether [Si/Fe] ratios are correlated between exoplanet and host star. On the other hand, lower precisions can test for systematic offsets between planet and star [Si/Fe], which can constrain the importance of giant impacts for extrasolar terrestrial planet formation.

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.

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.

Comet and Asteroid Hazard to the Terrestrial Planets

Science.gov (United States)

Ipatov, S. I.; Mather, J. C.; Oegerle, William (Technical Monitor)

2002-01-01

We made computer simulations of orbital evolution for intervals of at least 5-10 Myr of N=2000 Jupiter-crossing objects (JCOs) with initial orbits close to those of real comets with period P less than 10 yr, 500 objects with orbits close to that of Comet 10P, and the asteroids initially located at the 3:1 and 5:2 resonances with Jupiter at initial eccentricity e(sub 0)=0.15 and initial inclination i(sub 0)=10(sup 0). The gravitational influence of all planets, except for Mercury and Pluto, was taken into account (without dissipative factors). We calculated the probabilities of collisions of bodies with the terrestrial planets, using orbital elements obtained with a step equal to 500 yr, and then summarized the results for all bodies, obtaining, the total probability Psigma of collisions with a planet and the total time interval Tsigma during which perihelion distance q of bodies was less than a semimajor axis of the planet. The values of p(sub r) =10(exp 6)Psigma/N and T(sub r)=T/1000 yr (where T=Tsigma/N) are presented in a table together with the ratio r of the total time interval when orbits were of Apollo type (at a greater than 1 AU, q less than 1.017 AU, e less than 0.999) to that of Amor type (1.017 less than q less than 1.33 AU), r(sub 2) is the same as r but for Apollo objects with e less than 0.9. For asteroids we present only results obtained by direct integration, as a symplectic method can give large errors for these resonances.

Atmospheric constraints for the CO2 partial pressure on terrestrial planets near the outer edge of the habitable zone

OpenAIRE

von Paris, P.; Grenfell, J. L.; Hedelt, P.; Rauer, H.; Selsis, F.; Stracke, B.

2013-01-01

In recent years, several potentially habitable, probably terrestrial exoplanets and exoplanet candidates have been discovered. The amount of CO2 in their atmosphere is of great importance for surface conditions and habitability. In the absence of detailed information on the geochemistry of the planet, this amount could be considered as a free parameter. Up to now, CO2 partial pressures for terrestrial planets have been obtained assuming an available volatile reservoir and outgassing scenarios...

Geology and Habitability of Terrestrial Planets

CERN Document Server

Fishbaugh, Kathryn E; Raulin, François; Marais, David J; Korablev, Oleg

2007-01-01

Given the fundamental importance of and universal interest in whether extraterrestrial life has developed or could eventually develop in our solar system and beyond, it is vital that an examination of planetary habitability goes beyond simple assumptions such as, "Where there is water, there is life." This book has resulted from a workshop at the International Space Science Institute (ISSI) in Bern, Switzerland (5-9 September 2005) that brought together planetary geologists, geophysicists, atmospheric scientists, and biologists to discuss the multi-faceted problem of how the habitability of a planet co-evolves with the geology of the surface and interior, the atmosphere, and the magnetosphere. Each of the six chapters has been written by authors with a range of expertise so that each chapter is itself multi-disciplinary, comprehensive, and accessible to scientists in all disciplines. These chapters delve into what life needs to exist and ultimately to thrive, the early environments of the young terrestrial pl...

Stellar aspects of habitability--characterizing target stars for terrestrial planet-finding missions.

Science.gov (United States)

Kaltenegger, Lisa; Eiroa, Carlos; Ribas, Ignasi; Paresce, Francesco; Leitzinger, Martin; Odert, Petra; Hanslmeier, Arnold; Fridlund, Malcolm; Lammer, Helmut; Beichman, Charles; Danchi, William; Henning, Thomas; Herbst, Tom; Léger, Alain; Liseau, René; Lunine, Jonathan; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

2010-01-01

We present and discuss the criteria for selecting potential target stars suitable for the search for Earth-like planets, with a special emphasis on the stellar aspects of habitability. Missions that search for terrestrial exoplanets will explore the presence and habitability of Earth-like exoplanets around several hundred nearby stars, mainly F, G, K, and M stars. The evaluation of the list of potential target systems is essential in order to develop mission concepts for a search for terrestrial exoplanets. Using the Darwin All Sky Star Catalogue (DASSC), we discuss the selection criteria, configuration-dependent subcatalogues, and the implication of stellar activity for habitability.

The Potential for Volcanism and Tectonics on Extrasolar Terrestrial Planets

Science.gov (United States)

Quick, Lynnae C.; Roberge, Aki

2018-01-01

JWST and other next-generation space telescopes (e.g., LUVOIR, HabEx, & OST) will usher in a new era of exoplanet characterization that may lead to the identification of habitable, Earth-like worlds. Like the planets and moons in our solar system, the surfaces and interiors of terrestrial exoplanets may be shaped by volcanism and tectonics (Fu et al., 2010; van Summeren et al., 2011; Henning and Hurford, 2014). The magnitude and rate of occurrence of these dynamic processes can either facilitate or preclude the existence of habitable environments. Likewise, it has been suggested that detections of cryovolcanism on icy exoplanets, in the form of geyser-like plumes, could indicate the presence of subsurface oceans (Quick et al., 2017).The presence of volcanic and tectonic activity on solid exoplanets will be intimately linked to planet size and heat output in the form of radiogenic and/or tidal heating. In order to place bounds on the potential for such activity, we estimated the heat output of a variety of exoplanets observed by Kepler. We considered planets whose masses and radii range from 0.067 ME (super-Ganymede) to 8 ME (super-Earth), and 0.5 to 1.8 RE, respectively. These heat output estimates were then compared to those of planets, moons, and dwarf planets in our solar system for which we have direct evidence for the presence/absence of volcanic and tectonic activity. After exoplanet heating rates were estimated, depths to putative molten layers in their interiors were also calculated. For planets such as TRAPPIST-1h, whose densities, orbital parameters, and effective temperatures are consistent with the presence of significant amounts of H2O (Luger et al., 2017), these calculations reveal the depths to internal oceans which may serve as habitable niches beneath surface ice layers.

What Should the FeO Content of a Terrestrial Planet Be?

Science.gov (United States)

Jones, John H.

2013-01-01

Basalts from the Earth, the Moon, Mars, and Vesta are strongly depleted in elements that prefer to reside in the metallic state (siderophile elements). Therefore, it is believed that all these bodies have metallic cores. We do not yet have siderophile element analyses of venusian or mercurian basalts, but we assume that Venus, too, as a terrestrial planet, has a metallic core. For the Earth, Moon, Mercury, and Mars, the moments-of-inertia of these bodies are consistent with metallic cores of various sizes. Because Venus rotates so slowly, it may be difficult to determine the moment-of-inertia of Venus in order to confirm this assumption. However, despite many possible complexities, it seems likely that most of the major and minor terrestrial planets have experienced some sort of metal/silicate equilibration, and we will use this as a boundary condition. One immediate contrast between the Earth and Moon is the difference in FeO content between lunar and terrestrial basalts. Both bodies presumably formed near 1 AU and formed from the same feeding zone of planetesimals, judging by their oxygen isotopes [13]. If, for example, the Moon formed from the Earth by a giant impact, then this event must have occurred before high-pressure equilibria had the opportunity to deplete the Earth s mantle in FeO. Alternatively, the bulk silicate Moon may be dominated by material from the impactor. Regardless, it would be useful to know the pressures where FeO incorporation into a metallic core is not of interest. If the Giant Impact hypothesis is correct, this should set an upper limit for the size of the proto-Earth at the time of the impact.

ON THE EFFECT OF GIANT PLANETS ON THE SCATTERING OF PARENT BODIES OF IRON METEORITE FROM THE TERRESTRIAL PLANET REGION INTO THE ASTEROID BELT: A CONCEPT STUDY

International Nuclear Information System (INIS)

Haghighipour, Nader; Scott, Edward R. D.

2012-01-01

In their model for the origin of the parent bodies of iron meteorites, Bottke et al. proposed differentiated planetesimals, formed in 1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these objects and their fragments were scattered into the asteroid belt as a result of interactions with planetary embryos. Although viable, this model does not include the effect of a giant planet that might have existed or been growing in the outer regions. We present the results of a concept study where we have examined the effect of a planetary body in the orbit of Jupiter on the early scattering of planetesimals from the terrestrial region into the asteroid belt. We integrated the orbits of a large battery of planetesimals in a disk of planetary embryos and studied their evolutions for different values of the mass of the planet. Results indicate that when the mass of the planet is smaller than 10 M ⊕ , its effects on the interactions among planetesimals and planetary embryos are negligible. However, when the planet mass is between 10 and 50 M ⊕ , simulations point to a transitional regime with ∼50 M ⊕ being the value for which the perturbing effect of the planet can no longer be ignored. Simulations also show that further increase of the mass of the planet strongly reduces the efficiency of the scattering of planetesimals from the terrestrial planet region into the asteroid belt. We present the results of our simulations and discuss their possible implications for the time of giant planet formation.

3D Indoor Building Environment Reconstruction using calibration of Range finder Data

DEFF Research Database (Denmark)

Jamali, Ali; Anton, François; Rahman, Alias Abdul

2015-01-01

Measurement (EDM) and Terrestrial Laser Scanner (TLS) are mostly used. In this paper, several techniques for indoor 3D building data acquisition have been investigated. For reducing the time and cost of indoor building data acquisition process, the Trimble LaserAce 1000 range finder is used. The accuracy...

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.

LOW Mg/Si PLANETARY HOST STARS AND THEIR Mg-DEPLETED TERRESTRIAL PLANETS

Energy Technology Data Exchange (ETDEWEB)

Carter-Bond, Jade C.; O' Brien, David P. [Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719 (United States); Delgado Mena, Elisa; Israelian, Garik; Gonzalez Hernandez, Jonay I. [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife (Spain); Santos, Nuno C., E-mail: j.bond@unsw.edu.au [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

2012-03-15

Simulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group of systems. Planets simulated as forming within these systems are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various feldspars. Planetary carbon abundances also vary in accordance with the host star C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs, lending validity to this approach. Further studies are required to determine the full planetary impacts of the bulk compositions predicted here.

CONDITIONS OF PASSAGE AND ENTRAPMENT OF TERRESTRIAL PLANETS IN SPIN-ORBIT RESONANCES

International Nuclear Information System (INIS)

Makarov, Valeri V.

2012-01-01

The dynamical evolution of terrestrial planets resembling Mercury in the vicinity of spin-orbit resonances is investigated using comprehensive harmonic expansions of the tidal torque taking into account the frequency-dependent quality factors and Love numbers. The torque equations are integrated numerically with a small step in time, including the oscillating triaxial torque components but neglecting the layered structure of the planet and assuming a zero obliquity. We find that a Mercury-like planet with a current value of orbital eccentricity (0.2056) is always captured in 3:2 resonance. The probability of capture in the higher 2:1 resonance is approximately 0.23. These results are confirmed by a semi-analytical estimation of capture probabilities as functions of eccentricity for both prograde and retrograde evolutions of spin rate. As follows from analysis of equilibrium torques, entrapment in 3:2 resonance is inevitable at eccentricities between 0.2 and 0.41. Considering the phase space parameters at the times of periastron, the range of spin rates and phase angles for which an immediate resonance passage is triggered is very narrow, and yet a planet like Mercury rarely fails to align itself into this state of unstable equilibrium before it traverses 2:1 resonance.

N-body simulations of terrestrial planet formation under the influence of a hot Jupiter

International Nuclear Information System (INIS)

Ogihara, Masahiro; Kobayashi, Hiroshi; Inutsuka, Shu-ichiro

2014-01-01

We investigate the formation of multiple-planet systems in the presence of a hot Jupiter (HJ) using extended N-body simulations that are performed simultaneously with semianalytic calculations. Our primary aims are to describe the planet formation process starting from planetesimals using high-resolution simulations, and to examine the dependences of the architecture of planetary systems on input parameters (e.g., disk mass, disk viscosity). We observe that protoplanets that arise from oligarchic growth and undergo type I migration stop migrating when they join a chain of resonant planets outside the orbit of an HJ. The formation of a resonant chain is almost independent of our model parameters, and is thus a robust process. At the end of our simulations, several terrestrial planets remain at around 0.1 AU. The formed planets are not equal mass; the largest planet constitutes more than 50% of the total mass in the close-in region, which is also less dependent on parameters. In the previous work of this paper, we have found a new physical mechanism of induced migration of the HJ, which is called a crowding-out. If the HJ opens up a wide gap in the disk (e.g., owing to low disk viscosity), crowding-out becomes less efficient and the HJ remains. We also discuss angular momentum transfer between the planets and disk.

Terrestrial planet formation in a protoplanetary disk with a local mass depletion: A successful scenario for the formation of Mars

Energy Technology Data Exchange (ETDEWEB)

Izidoro, A.; Winter, O. C. [UNESP, Univ. Estadual Paulista - Grupo de Dinâmica Orbital and Planetologia, Guaratinguetá, CEP 12.516-410, São Paulo (Brazil); Haghighipour, N. [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Tsuchida, M., E-mail: izidoro@feg.unesp.br, E-mail: nader@ifa.hawaii.edu [UNESP, Univ. Estadual Paulista, DCCE-IBILCE, São José do Rio Preto, CEP 15.054-000, São Paulo (Brazil)

2014-02-10

Models of terrestrial planet formation for our solar system have been successful in producing planets with masses and orbits similar to those of Venus and Earth. However, these models have generally failed to produce Mars-sized objects around 1.5 AU. The body that is usually formed around Mars' semimajor axis is, in general, much more massive than Mars. Only when Jupiter and Saturn are assumed to have initially very eccentric orbits (e ∼ 0.1), which seems fairly unlikely for the solar system, or alternately, if the protoplanetary disk is truncated at 1.0 AU, simulations have been able to produce Mars-like bodies in the correct location. In this paper, we examine an alternative scenario for the formation of Mars in which a local depletion in the density of the protosolar nebula results in a non-uniform formation of planetary embryos and ultimately the formation of Mars-sized planets around 1.5 AU. We have carried out extensive numerical simulations of the formation of terrestrial planets in such a disk for different scales of the local density depletion, and for different orbital configurations of the giant planets. Our simulations point to the possibility of the formation of Mars-sized bodies around 1.5 AU, specifically when the scale of the disk local mass-depletion is moderately high (50%-75%) and Jupiter and Saturn are initially in their current orbits. In these systems, Mars-analogs are formed from the protoplanetary materials that originate in the regions of disk interior or exterior to the local mass-depletion. Results also indicate that Earth-sized planets can form around 1 AU with a substantial amount of water accreted via primitive water-rich planetesimals and planetary embryos. We present the results of our study and discuss their implications for the formation of terrestrial planets in our solar system.

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.

Evolving dynamical regimes during secular cooling of terrestrial planets : insights and inferences from numerical models

NARCIS (Netherlands)

Thienen, Peter van

2003-01-01

Although plate tectonics is the present-day mode of geodynamics on Earth, it is not so on Mars and Venus, and probably also not during the early history of the Earth. In this thesis, the conditions under which plate tectonics may operate on terrestrial planets are investigated. Numerical model

The Phase-Induced Amplitude Apodization Coronagraph (PIAAC): Performance for Imaging of Earth-like Exoplanets.

Science.gov (United States)

Martinache, F.; Guyon, O.; Pluzhnik, E.; Ridgway, S.; Galicher, R.

2004-12-01

PIAA is one of the powerful applications of pupil remapping. A set of two aspheric mirrors changes the distribution of light and provides an apodized pupil, suitable for coronagraphy, without light loss on an absorbing mask. Deployed on to a space telescope with coronagraphic quality optics, it may allow planet detection from a 1.2 λ /d inner working distance and a full working field. We describe the performance of a PIAA version of NASA's Terrestrial Planet Finder (TPF) in terms of Signal to Noise Ratio and compare it to Classical Pupil Apodization (CPA) performance. We also discuss the necessity of using different occulting masks and give an estimate of the total exposure time for the planet detection phase of the TPF mission. This study is based on realistic Monte Carlo simulations of terrestrial planets orbiting around F, G, K stars within 30 pc around the solar system and includes planet phase and angular separation probabilities. This work was carried out under JPL contract numbers 1254445 and 1257767 for Development of Technologies for the Terrestrial Planet Finder Mission, with the support and hospitality of the National Astronomical Observatory of Japan.

Relative locations of the bow shocks of the terrestrial planets

International Nuclear Information System (INIS)

Russell, C.T.

1977-01-01

The observed bow shock encounters at Mercury, Venus and Mars are least square fit using the same technique so that their sizes and shapes can be intercompared. The shock front of Mercury most resembles the terrestrial shock in shape, and the shock stand off distance is consistent with the observed moment. The shapes of the Venus and Mars shock fronts more resemble each other than the earth's and the stand off distances are consistent with direct interaction of the solar wind with the ionosphere on the dayside. The Venus shock is closer to the planet than the Mars shock suggesting more absorption of the solar wind at Venus

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.

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.)

Demarcating Circulation Regimes of Synchronously Rotating Terrestrial Planets within the Habitable Zone

Science.gov (United States)

Haqq-Misra, Jacob; Wolf, Eric. T.; Joshi, Manoj; Zhang, Xi; Kopparapu, Ravi Kumar

2018-01-01

We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model. The surface temperature contrast between the day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen in gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from the day to the night sides, which occurs for planets around stars with effective temperatures of 3300–4500 K (rotation period > 20 days), with both the Rossby deformation radius and the Rhines length exceeding the planetary radius. Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period days), with the Rossby deformation radius less than the planetary radius. In between is the Rhines rotation regime, which retains a thermally direct circulation from the day side to the night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000–3300 K (rotation period ∼5–20 days), where the Rhines length is greater than the planetary radius but the Rossby deformation radius is less than the planetary radius. The dynamical state can be observationally inferred from a comparison of the morphologies of the thermal emission phase curves of synchronously rotating planets.

The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

Science.gov (United States)

Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

2012-06-01

Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

Formation of the terrestrial planets in the solar system around 1 au via radial concentration of planetesimals

Science.gov (United States)

Ogihara, Masahiro; Kokubo, Eiichiro; Suzuki, Takeru K.; Morbidelli, Alessandro

2018-05-01

Context. No planets exist inside the orbit of Mercury and the terrestrial planets of the solar system exhibit a localized configuration. According to thermal structure calculation of protoplanetary disks, a silicate condensation line ( 1300 K) is located around 0.1 au from the Sun except for the early phase of disk evolution, and planetesimals could have formed inside the orbit of Mercury. A recent study of disk evolution that includes magnetically driven disk winds showed that the gas disk obtains a positive surface density slope inside 1 au from the central star. In a region with positive midplane pressure gradient, planetesimals undergo outward radial drift. Aims: We investigate the radial drift of planetesimals and type I migration of planetary embryos in a disk that viscously evolves with magnetically driven disk winds. We show a case in which no planets remain in the close-in region. Methods: Radial drifts of planetesimals are simulated using a recent disk evolution model that includes effects of disk winds. The late stage of planet formation is also examined by performing N-body simulations of planetary embryos. Results: We demonstrate that in the middle stage of disk evolution, planetesimals can undergo convergent radial drift in a magnetorotational instability (MRI)-inactive disk, in which the pressure maximum is created, and accumulate in a narrow ring-like region with an inner edge at 0.7 au from the Sun. We also show that planetary embryos that may grow from the narrow planetesimal ring do not exhibit significant type I migration in the late stage of disk evolution. Conclusions: The origin of the localized configuration of the terrestrial planets of the solar system, in particular the deficit of close-in planets, can be explained by the convergent radial drift of planetesimals in disks with a positive pressure gradient in the close-in region.

Skin Condition Finder

Science.gov (United States)

... SKIN CONDITIONS HEALTH TOPICS FOR PROFESSIONALS Rash and Skin Condition Finder 1 Select Age Group Infant Child ... Toe Toe Webspace Toe Nail CLOSE About the Skin Condition Finder Have a health question or concern? ...

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.

Integrated Wavefront Corrector, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — One of the critical issues for NASA missions requiring high contrast astrophysical imaging such as Terrestrial Planet Finder (TPF) is wavefront control. Without use...

The origin of methane and biomolecules from a CO2 cycle on terrestrial planets

Czech Academy of Sciences Publication Activity Database

Civiš, Svatopluk; Knížek, Antonín; Ivanek, Ondřej; Kubelík, Petr; Zukalová, Markéta; Kavan, Ladislav; Ferus, Martin

2017-01-01

Roč. 1, č. 10 (2017), s. 721-726 E-ISSN 2397-3366 R&D Projects: GA ČR GA17-05076S; GA ČR GA13-07724S Grant - others:Akademie věd - GA AV ČR(CZ) R200401721; Akademie věd - GA AV ČR(CZ) R200401521 Institutional support: RVO:61388955 Keywords : biomolecules * CO2 cycle on terrestrial planets * Mars Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry

Polyamorphic Transformations in Fe-Ni-C Liquids: Implications for Chemical Evolution of Terrestrial Planets: Fe-Ni-C liquid structural change

Energy Technology Data Exchange (ETDEWEB)

Lai, Xiaojing [Department of Geology and Geophysics, University of Hawai‘i at Mānoa, Honolulu HI USA; Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Chen, Bin [Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Wang, Jianwei [Department of Geology and Geophysics, Center for Computation and Technology, Louisiana State University, Baton Rouge LA USA; Kono, Yoshio [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL USA; Zhu, Feng [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor MI USA

2017-12-01

During the formation of the Earth's core, the segregation of metallic liquids from silicate mantle should have left behind evident geochemical imprints on both the mantle and the core. Some distinctive geochemical signatures of the mantle-derived rocks likely own their origin to the metal-silicate differentiation of the primitive Earth, setting our planet apart from undifferentiated meteorites as well as terrestrial planets or moons isotopically and compositionally. Understanding the chemical evolution of terrestrial planetary bodies requires knowledge on properties of both liquid iron alloys and silicates equilibrating under physicochemical conditions pertinent to the deep magma ocean. Here we report experimental and computational results on the pressure-induced structural evolution of iron-nickel liquids alloyed with carbon. Our X-ray diffraction experiments up to 7.3 gigapascals (GPa) demonstrate that Fe-Ni (Fe90Ni10) liquids alloyed with 3 and 5 wt % carbon undergo a polyamorphic liquid structure transition at approximately 5 GPa. Corroborating the experimental observations, our first-principles molecular dynamic calculations reveal that the structural transitions result from the marked prevalence of three-atom face-sharing polyhedral connections in the liquids at >5 GPa. The structure and polyamorphic transitions of liquid iron-nickel-carbon alloys govern their physical and chemical properties and may thus cast fresh light on the chemical evolution of terrestrial planets and moons.

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

Climatic Evolution and Habitability of Terrestrial Planets: Perspectives from Coupled Atmosphere-Mantle Systems

Science.gov (United States)

Basu Sarkar, D.; Moore, W. B.

2016-12-01

A multitude of factors including the distance from the host star and the stage of planetary evolution affect planetary climate and habitability. The complex interactions between the atmosphere and dynamics of the deep interior of the planets along with stellar fluxes present a formidable challenge. This work employs simplified approaches to address these complex issues in a systematic way. To be specific, we are investigating the coupled evolution of atmosphere and mantle dynamics. The overarching goal here is to simulate the evolutionary history of the terrestrial planets, for example Venus, Earth and Mars. This research also aims at deciphering the history of Venus-like runaway greenhouse and thus explore the possibility of cataclysmic shifts in climate of Earth-like planets. We focus on volatile cycling within the solid planets to understand the role of carbon/water in climatic and tectonic outcomes of such planets. In doing so, we are considering the feedbacks in the coupled mantle-atmosphere system. The primary feedback between the atmosphere and mantle is the surface temperature established by the greenhouse effect, which regulates the temperature gradient that drives the mantle convection and controls the rate at which volatiles are exchanged through weathering. We start our models with different initial assumptions to determine the final climate outcomes within a reasonable parameter space. Currently, there are very few planetary examples, to sample the climate outcomes, however this will soon change as exoplanets are discovered and examined. Therefore, we will be able to work with a significant number of potential candidates to answer questions like this one: For every Earth is there one Venus? ten? a thousand?

Predicting the Atmospheric Composition of Extrasolar Giant Planets

Science.gov (United States)

Sharp, A. G.; Moses, J. I.; Friedson, A. J.; Fegley, B., Jr.; Marley, M. S.; Lodders, K.

2004-01-01

To date, approximately 120 planet-sized objects have been discovered around other stars, mostly through the radial-velocity technique. This technique can provide information about a planet s minimum mass and its orbital period and distance; however, few other planetary data can be obtained at this point in time unless we are fortunate enough to find an extrasolar giant planet that transits its parent star (i.e., the orbit is edge-on as seen from Earth). In that situation, many physical properties of the planet and its parent star can be determined, including some compositional information. Our prospects of directly obtaining spectra from extrasolar planets may improve in the near future, through missions like NASA's Terrestrial Planet Finder. Most of the extrasolar giant planets (EGPs) discovered so far have masses equal to or greater than Jupiter's mass, and roughly 16% have orbital radii less than 0.1 AU - extremely close to the parent star by our own Solar-System standards (note that Mercury is located at a mean distance of 0.39 AU and Jupiter at 5.2 AU from the Sun). Although all EGPs are expected to have hydrogen-dominated atmospheres similar to Jupiter, the orbital distance can strongly affect the planet's temperature, physical, chemical, and spectral properties, and the abundance of minor, detectable atmospheric constituents. Thermochemical equilibrium models can provide good zero-order predictions for the atmospheric composition of EGPs. However, both the composition and spectral properties will depend in large part on disequilibrium processes like photochemistry, chemical kinetics, atmospheric transport, and haze formation. We have developed a photochemical kinetics, radiative transfer, and 1-D vertical transport model to study the atmospheric composition of EGPs. The chemical reaction list contains H-, C-, O-, and N-bearing species and is designed to be valid for atmospheric temperatures ranging from 100-3000 K and pressures up to 50 bar. Here we examine

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.

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.

Late Impacts and the Origins of the Atmospheres on the Terrestrial Planets

Science.gov (United States)

Mukhopadhyay, S.; Stewart, S. T.; Lock, S. J.; Parai, R.; Tucker, J. M.

2014-12-01

Models for the origin of terrestrial atmospheres typically require an intricate sequence of events, including hydrodynamic escape, outgassing of mantle volatiles and late delivery. Here we discuss the origin of the atmospheres on the terrestrial planets in light of new ideas about the formation of the Moon, giant impact induced atmospheric loss and recent noble gas measurements. Our new measurements indicate that noble gases in the Earth's atmosphere cannot be derived from any combination of fractionation of a nebular-derived atmosphere followed by outgassing of deep or shallow mantle volatiles. While Ne in the mantle retains a nebular component, the present-day atmosphere has no memory of nebular gases. Rather, atmospheric noble gases have a close affinity to chondrites. On the other hand, Venus's atmosphere has 20 and 70 times higher abundance of 20Ne and 36Ar, respectively, and a 20Ne/22Ne ratio closer to the solar value than Earth's atmosphere. While the present atmosphere of Mars is significantly fractionated in the lighter noble gases due to long term atmospheric escape, the Kr isotopic ratios in Martian atmosphere are identical to solar. Thus, while Earth's atmosphere has no memory of accretion of nebular gases, atmospheres on both Venus and Mars preserve at least a component of nebular gases. To explain the above observations, we propose that a common set of processes operated on the terrestrial planets, and that their subsequent evolutionary divergence is simply explained by planetary size and the stochastic nature of giant impacts. We present geochemical observations and simulations of giant impacts to show that most of Earth's mantle was degassed and the outgassed volatiles were largely lost during the final sequence of giant impacts onto Earth. Earth's noble gases were therefore dominantly derived from late-accreting planetesimals. In contrast, Venus did not suffer substantial atmospheric loss by a late giant impact and retains a higher abundance of

Abiotic nitrogen fixation on terrestrial planets: reduction of NO to ammonia by FeS.

Science.gov (United States)

Summers, David P; Basa, Ranor C B; Khare, Bishun; Rodoni, David

2012-02-01

Understanding the abiotic fixation of nitrogen and how such fixation can be a supply of prebiotic nitrogen is critical for understanding both the planetary evolution of, and the potential origin of life on, terrestrial planets. As nitrogen is a biochemically essential element, sources of biochemically accessible nitrogen, especially reduced nitrogen, are critical to prebiotic chemistry and the origin of life. Loss of atmospheric nitrogen can result in loss of the ability to sustain liquid water on a planetary surface, which would impact planetary habitability and hydrological processes that shape the surface. It is known that NO can be photochemically converted through a chain of reactions to form nitrate and nitrite, which can be subsequently reduced to ammonia. Here, we show that NO can also be directly reduced, by FeS, to ammonia. In addition to removing nitrogen from the atmosphere, this reaction is particularly important as a source of reduced nitrogen on an early terrestrial planet. By converting NO directly to ammonia in a single step, ammonia is formed with a higher product yield (~50%) than would be possible through the formation of nitrate/nitrite and subsequent conversion to ammonia. In conjunction with the reduction of NO, there is also a catalytic disproportionation at the mineral surface that converts NO to NO₂ and N₂O. The NO₂ is then converted to ammonia, while the N₂O is released back in the gas phase, which provides an abiotic source of nitrous oxide.

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.

IdentiFINDER Laboratory Exercise

Energy Technology Data Exchange (ETDEWEB)

Weinmann-Smith, Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-09-21

The identiFINDER2 is an easily portable handheld NaI gamma detector. The IAEA uses the safeguards version of the identiFINDER2 and calls it the HM-5. The HM-5 has built in software to analyze the detection signal specifically for IAEA verification applications.

Time-Dependent Simulations of the Formation and Evolution of Disk-Accreted Atmospheres Around Terrestrial Planets

Science.gov (United States)

Stoekl, Alexander; Dorfi, Ernst

2014-05-01

In the early, embedded phase of evolution of terrestrial planets, the planetary core accumulates gas from the circumstellar disk into a planetary envelope. This atmosphere is very significant for the further thermal evolution of the planet by forming an insulation around the rocky core. The disk-captured envelope is also the staring point for the atmospheric evolution where the atmosphere is modified by outgassing from the planetary core and atmospheric mass loss once the planet is exposed to the radiation field of the host star. The final amount of persistent atmosphere around the evolved planet very much characterizes the planet and is a key criterion for habitability. The established way to study disk accumulated atmospheres are hydrostatic models, even though in many cases the assumption of stationarity is unlikely to be fulfilled. We present, for the first time, time-dependent radiation hydrodynamics simulations of the accumulation process and the interaction between the disk-nebula gas and the planetary core. The calculations were performed with the TAPIR-Code (short for The adaptive, implicit RHD-Code) in spherical symmetry solving the equations of hydrodynamics, gray radiative transport, and convective energy transport. The models range from the surface of the solid core up to the Hill radius where the planetary envelope merges into the surrounding protoplanetary disk. Our results show that the time-scale of gas capturing and atmospheric growth strongly depends on the mass of the solid core. The amount of atmosphere accumulated during the lifetime of the protoplanetary disk (typically a few Myr) varies accordingly with the mass of the planet. Thus, a core with Mars-mass will end up with about 10 bar of atmosphere while for an Earth-mass core, the surface pressure reaches several 1000 bar. Even larger planets with several Earth masses quickly capture massive envelopes which in turn become gravitationally unstable leading to runaway accretion and the eventual

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Thermal models of Mercury. Ph.D. Thesis

Science.gov (United States)

Leake, M. A.

1982-01-01

Recent and more complex thermal models of Mercury and the terrestrial planets are discussed or noted. These models isolate a particular aspect of the planet's thermal history in an attempt to understand that parameter. Among these topics are thermal conductivity, convection, radiogenic sources of heat, other heat sources, and the problem of the molten core and regenerative dynamo.

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)

The chemical composition of the cores of the terrestrial planets and the moon

Science.gov (United States)

Kuskov, O. L.; Khitarov, N. I.

1977-01-01

Using models of the quasi-chemical theory of solutions, the activity coefficients of silicon are calculated in the melts Fe-Si, Ni-Si, and Fe-Ni-Si. The calculated free energies of solution of liquid nickel and silicon in liquid iron in the interval 0 to 1400 kbar and 1500 to 4000 K, shows that Fe-Ni-Si alloy is stable under the conditions of the outer core of the earth and the cores of the terrestrial planets. The oxidation-reduction conditions are studied, and the fugacity of oxygen in the mantles of the planets and at the core-mantle boundary are calculated. The mechanism of reduction of silicon is analyzed over a broad interval of p and T. The interaction between the matter of the core and mantle is studied, resulting in the extraction of silicon from the mantle and its solution in the material of the core. It is concluded that silicon can enter into the composition of the outer core of the earth and Venus, but probably does not enter into the composition of the cores of Mercury, Mars, and the moon, if in fact the latter possesses one.

Energy Balance Models of planetary climate as a tool for investigating the habitability of terrestrial planets and its evolution

Science.gov (United States)

Ferri, G.; Murante, G.; Provenzale, A.; Silva, L.; Vladilo, G.

2012-04-01

The study of the habitability and potential for life formation of terrestrial planets requires a considerable work of modelization owing to the limited amount of experimental constraints typical of this type of research. As an example, the paucity of experimental Archean data severely limits the study of the habitability of the primitive Earth at the epoch of the origin of life. In the case of exoplanets the amount of experimental information available is quite limited and the need for modelization strong. Here we focus on the modelization of the surface planetary temperature, a key thermodynamical quantity used to define the habitability. Energy Balance Models (EBM) of planetary climate provide a simple way to calculate the temperature-latitude profile of terrestrial planets with a small amount of computing resources. Thanks to this fact EBMs offer an excellent tool to exploring a wide range of parameter space and therefore testing the effects of variations of physical/chemical quantities unconstrained by experimental data. In particular, one can easily probe possible scenarios of habitability at different stages of planetary evolution. We have recently implemented one-dimensional EBMs featuring the possibility of probing variations of astronomical and geophysical parameters, such as stellar luminosity, orbital semi-major axis and eccentricity, obliquity of the planetary axis, planet rotational velocity, land/ocean surface fractions and thermal capacities, and latitudinal heat diffusion. After testing our models against results obtained in previous work (Williams & Kasting 1997, Icarus, 129, 254; Spiegel et al. 2008, ApJ, 681, 1609), we introduced a novel parametrization of the diffusion coefficient as a function of the stellar zenith distance. Our models have been validated using the mean temperature-latitude profiles of the present Earth and its seasonal variations; the global albedo has been used as an additional constraint. In this work we present specific

Introduction to IdentiFINDERs

Energy Technology Data Exchange (ETDEWEB)

Rees, Brian G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2018-02-05

These are slides from a presentation. The identiFINDER provides information on radiation levels. It can automatically identify isotopes in its library. It can save spectra for transfer to a computer, and has a 4-8 hour battery life. The following is covered: an overview, operating modes, getting started, finder mode, search, identification mode, dose & rate, warning & alarm, options (ultra LGH), options (identifinder2), and general procedure.

BS-virus-finder

DEFF Research Database (Denmark)

Gao, Shengjie; Hu, Xuesong; Xu, Fengping

2018-01-01

Background: DNA methylation plays a key role in the regulation of gene expression and carcinogenesis. Bisulfite sequencing studies mainly focus on calling SNP, DMR, and ASM. Until now, only a few software tools focus on virus integration using bisulfite sequencing data. Findings: We have developed...... a new and easy-to-use software tool, named BS-virus-finder (BSVF, RRID:SCR_015727), to detect viral integration breakpoints in whole human genomes. The tool is hosted at https://github.com/BGI-SZ/BSVF. Conclusions: BS-virus-finder demonstrates high sensitivity and specificity. It is useful in epigenetic...

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution: Introduction. Ph.D. Thesis

Science.gov (United States)

Leake, M. A.

1982-01-01

The relative ages of various geologic units and structures place tight constraints on the origin of the Moon and the planet Mercury, and thus provide a better understanding of the geologic histories of these bodies. Crater statistics, a reexamination of lunar geologic maps, and the compilation of a geologic map of a quarter of Mercury's surface based on plains units dated relative to crater degradation classes were used to determine relative ages. This provided the basis for deducing the origin of intercrater plains and their role in terrestrial planet evolution.

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

Planets a very short introduction

CERN Document Server

Rothery, David A

2010-01-01

Planets: A Very Short Introduction demonstrates the excitement, uncertainties, and challenges faced by planetary scientists, and provides an overview of our Solar System and its origins, nature, and evolution. Terrestrial planets, giant planets, dwarf planets and various other objects such as satellites (moons), asteroids, trans-Neptunian objects, and exoplanets are discussed. Our knowledge about planets has advanced over the centuries, and has expanded at a rapidly growing rate in recent years. Controversial issues are outlined, such as What qualifies as a planet? What conditions are required for a planetary body to be potentially inhabited by life? Why does Pluto no longer have planet status? And Is there life on other planets?

Directional Wide-Angle Range Finder (DWARF)

Data.gov (United States)

National Aeronautics and Space Administration — The proposed innovation, the Directional Wide-Angle Range Finder (DWARF) is the creation of a laser range-finder with a wide field-of-view (FOV) and a directional...

Classifying Planets: Nature vs. Nurture

Science.gov (United States)

Beichman, Charles A.

2009-05-01

The idea of a planet was so simple when we learned about the solar system in elementary school. Now students and professional s alike are faced with confusing array of definitions --- from "Brown Dwarfs” to "Super Jupiters", from "Super Earths” to "Terrestrial Planets", and from "Planets” to "Small, Sort-of Round Things That Aren't Really Planets". I will discuss how planets might be defined by how they formed, where they are found, or by the life they might support.

Abiotic production of methane in terrestrial planets.

Science.gov (United States)

Guzmán-Marmolejo, Andrés; Segura, Antígona; Escobar-Briones, Elva

2013-06-01

On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×10(8) and 1.3×10(9) molecules cm(-2) s(-1) for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life.

Tectonic history of the terrestrial planets. Final technical report, 1 October 1976-30 September 1989

International Nuclear Information System (INIS)

Solomon, S.C.

1990-02-01

It is impossible in a single brief summary to convey the full range of research results that have come from this project over the last 13 years. The sweep of subjects covered ranges widely over the broad areas of the thermal and tectonic evolution of the terrestrial planets. A full list of all publications supported by this grant is presented. The list includes 48 published journal articles, 2 papers currently in press, 3 chapters of books, 4 M.I.T. theses, 1 technical report, and 107 published abstracts and extended abstracts. All of these publications were submitted separately to NASA at the time of publication or submission

A low-order model of water vapor, clouds, and thermal emission for tidally locked terrestrial planets

Energy Technology Data Exchange (ETDEWEB)

Yang, Jun; Abbot, Dorian S., E-mail: junyang28@uchicago.edu [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

2014-04-01

In the spirit of minimal modeling of complex systems, we develop an idealized two-column model to investigate the climate of tidally locked terrestrial planets with Earth-like atmospheres in the habitable zone of M-dwarf stars. The model is able to approximate the fundamental features of the climate obtained from three-dimensional (3D) atmospheric general circulation model (GCM) simulations. One important reason for the two-column model's success is that it reproduces the high cloud albedo of the GCM simulations, which reduces the planet's temperature and delays the onset of a runaway greenhouse state. The two-column model also clearly illustrates a secondary mechanism for determining the climate: the nightside acts as a 'radiator fin' through which infrared energy can be lost to space easily. This radiator fin is maintained by a temperature inversion and dry air on the nightside, and plays a similar role to the subtropics on modern Earth. Since one-dimensional radiative-convective models cannot capture the effects of the cloud albedo and radiator fin, they are systematically biased toward a narrower habitable zone. We also show that cloud parameters are the most important in the two-column model for determining the day-night thermal emission contrast, which decreases and eventually reverses as the stellar flux increases. This reversal is important because it could be detected by future extrasolar planet characterization missions, which would suggest that the planet has Earth-like water clouds and is potentially habitable.

Radio images of the planets

International Nuclear Information System (INIS)

De Pater, I.

1990-01-01

Observations at radio wavelengths make possible detailed studies of planetary atmospheres, magnetospheres, and surface layers. The paper addresses the question of what can be learned from interferometric radio images of planets. Results from single-element radio observations are also discussed. Observations of both the terrestrial and the giant planets are considered. 106 refs

Abiotic Production of Methane in Terrestrial Planets

Science.gov (United States)

Guzmán-Marmolejo, Andrés; Escobar-Briones, Elva

2013-01-01

Abstract On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×108 and 1.3×109 molecules cm−2 s−1 for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life. Key Words: Serpentinization—Exoplanets—Biosignatures—Planetary atmospheres. Astrobiology 13, 550–559. PMID:23742231

Water and the Interior Structure of Terrestrial Planets and Icy Bodies

Science.gov (United States)

Monteux, J.; Golabek, G. J.; Rubie, D. C.; Tobie, G.; Young, E. D.

2018-02-01

Water content and the internal evolution of terrestrial planets and icy bodies are closely linked. The distribution of water in planetary systems is controlled by the temperature structure in the protoplanetary disk and dynamics and migration of planetesimals and planetary embryos. This results in the formation of planetesimals and planetary embryos with a great variety of compositions, water contents and degrees of oxidation. The internal evolution and especially the formation time of planetesimals relative to the timescale of radiogenic heating by short-lived 26Al decay may govern the amount of hydrous silicates and leftover rock-ice mixtures available in the late stages of their evolution. In turn, water content may affect the early internal evolution of the planetesimals and in particular metal-silicate separation processes. Moreover, water content may contribute to an increase of oxygen fugacity and thus affect the concentrations of siderophile elements within the silicate reservoirs of Solar System objects. Finally, the water content strongly influences the differentiation rate of the icy moons, controls their internal evolution and governs the alteration processes occurring in their deep interiors.

The Planetary Terrestrial Analogues Library (PTAL)

Science.gov (United States)

Werner, S. C.; Dypvik, H.; Poulet, F.; Rull Perez, F.; Bibring, J.-P.; Bultel, B.; Casanova Roque, C.; Carter, J.; Cousin, A.; Guzman, A.; Hamm, V.; Hellevang, H.; Lantz, C.; Lopez-Reyes, G.; Manrique, J. A.; Maurice, S.; Medina Garcia, J.; Navarro, R.; Negro, J. I.; Neumann, E. R.; Pilorget, C.; Riu, L.; Sætre, C.; Sansano Caramazana, A.; Sanz Arranz, A.; Sobron Grañón, F.; Veneranda, M.; Viennet, J.-C.; PTAL Team

2018-04-01

The Planetary Terrestrial Analogues Library project aims to build and exploit a spectral data base for the characterisation of the mineralogical and geological evolution of terrestrial planets and small solar system bodies.

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Discussion of the nature, origin and role of the intercrater plains of Mercury and the Moon. Ph.D. Thesis

Science.gov (United States)

Leake, M. A.

1982-01-01

The nature and origin of the intercrater plains of Mercury and the Moon as determined through geologic mapping, crater statistics, and remotely sensed data are summarized. Implications of these results regarding scarp formation, absolute ages, and terrestrial planet surfaces are included. The role of the intercrater plains is defined and future work which might lead to a better understanding of these units and terrestrial planet evolution is outlined.

Characterizing Terrestrial Exoplanets

Science.gov (United States)

Meadows, V. S.; Lustig-Yaeger, J.; Lincowski, A.; Arney, G. N.; Robinson, T. D.; Schwieterman, E. W.; Deming, L. D.; Tovar, G.

2017-11-01

We will provide an overview of the measurements, techniques, and upcoming missions required to characterize terrestrial planet environments and evolution, and search for signs of habitability and life.

The persistent and pernicious myth of the early CO2-N2 atmospheres of terrestrial planets

Science.gov (United States)

Shaw, G. H.

2009-12-01

The accepted model for early atmospheres of terrestrial planets has settled on a CO2-N2 composition. Unfortunately, while it is largely based on a brilliant geological analysis by Rubey, there is no compelling evidence whatsoever for such a composition as the first “permanent” atmosphere for Earth or any other planet. In fact, geological discoveries of the past 50+ years reveal several problems with a CO2-N2 atmosphere, some of which Rubey recognized in his own analysis. He clearly addressed the problem of timing of degassing, concluding that early massive degassing of CO2 would produce readily observed and profound effects, which are not evident. Modeling and constraints on the timing of planetary accretion and core formation indicate massive early degassing. If early degassing emitted CO2-N2, the effects are concealed. Plate tectonic recycling is not a solution, as conditions would have persisted beyond the time of the earliest rocks, which do not show the effects. Attempts to return degassed CO2 to the mantle are not only ad hoc, but inconsistent with early thermal structure of the Earth. Second, production of prebiotic organic compounds from a CO2-N2 atmosphere has been a nagging problem. At best this has been addressed by invoking hydrogen production from the mantle to provide reducing capacity. While hydrogen may be emitted in volcanic eruptions, it is exceedingly difficult to imagine this process generating enough organics to yield high concentrations in a global ocean. The recent fashion of invoking organic synthesis at deep-sea vents suffers from the same problem: how to achieve sufficient concentrations of organics in a global ocean by abiotic synthesis when hydrothermal activity stirs the solution and carries the prebiotic products off to great dilution? Suggesting life began at deep-sea vents, and continues to carry on chemosynthesis there, begs the question. Unless you get high enough concentrations of prebiotics by abiotic processes, you simply

MICROLENS TERRESTRIAL PARALLAX MASS MEASUREMENTS: A RARE PROBE OF ISOLATED BROWN DWARFS AND FREE-FLOATING PLANETS

International Nuclear Information System (INIS)

Gould, Andrew; Yee, Jennifer C.

2013-01-01

Terrestrial microlens parallax is one of the very few methods that can measure the mass and number density of isolated dark low-mass objects, such as old free-floating planets and brown dwarfs. Terrestrial microlens parallax can be measured whenever a microlensing event differs substantially as observed from two or more well-separated sites. If the lens also transits the source during the event, then its mass can be measured. We derive an analytic expression for the expected rate of such events and then use this to derive two important conclusions. First, the rate is directly proportional to the number density of a given population, greatly favoring low-mass populations relative to their contribution to the general microlensing rate, which further scales as M 1/2 where M is the lens mass. Second, the rate rises sharply as one probes smaller source stars, despite the fact that the probability of transit falls directly with source size. We propose modifications to current observing strategies that could yield a factor of 100 increase in sensitivity to these rare events.

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

Science.gov (United States)

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

Healthcare Finder API

Data.gov (United States)

U.S. Department of Health & Human Services — All of the data used on the Finder.HealthCare.gov web application is available through this API. There are multiple collections of data available through the API. 1....

CROWDING-OUT OF GIANTS BY DWARFS: AN ORIGIN FOR THE LACK OF COMPANION PLANETS IN HOT JUPITER SYSTEMS

International Nuclear Information System (INIS)

Ogihara, Masahiro; Inutsuka, Shu-ichiro; Kobayashi, Hiroshi

2013-01-01

We investigate the formation of close-in terrestrial planets from planetary embryos under the influence of a hot Jupiter (HJ) using gravitational N-body simulations that include gravitational interactions between the gas disk and the terrestrial planet (e.g., type I migration). Our simulations show that several terrestrial planets efficiently form outside the orbit of the HJ, making a chain of planets, and all of them gravitationally interact directly or indirectly with the HJ through resonance, which leads to inward migration of the HJ. We call this mechanism of induced migration of the HJ ''crowding-out''. The HJ is eventually lost through collision with the central star, and only several terrestrial planets remain. We also find that the efficiency of the crowding-out effect depends on the model parameters; for example, the heavier the disk is, the more efficient the crowding-out is. When planet formation occurs in a massive disk, the HJ can be lost to the central star and is never observed. On the other hand, for a less massive disk, the HJ and terrestrial planets can coexist; however, the companion planets may be below the detection limit of current observations. In both cases, systems with a HJ and terrestrial planets have little chance of detection. Therefore, our model naturally explains the lack of companion planets in HJ systems regardless of the disk mass. In effect, our model provides a theoretical prediction for future observations; additional planets can be discovered just outside the HJ, and their masses should generally be small

TERRESTRIAL, HABITABLE-ZONE EXOPLANET FREQUENCY FROM KEPLER

International Nuclear Information System (INIS)

Traub, Wesley A.

2012-01-01

Data from Kepler's first 136 days of operation are analyzed to determine the distribution of exoplanets with respect to radius, period, and host-star spectral type. The analysis is extrapolated to estimate the percentage of terrestrial, habitable-zone (HZ) exoplanets. The Kepler census is assumed to be complete for bright stars (magnitude 0.5 Earth radius and periods β–1 , with β ≅ 0.71 ± 0.08; and an extrapolation to longer periods gives the frequency of terrestrial planets in the HZs of FGK stars as η ⊕ ≅ (34 ± 14)%. Thus about one-third of FGK stars are predicted to have at least one terrestrial, HZ planet.

Symbolic PathFinder v7

DEFF Research Database (Denmark)

Luckow, Kasper Søe; Păsăreanu, Corina

2014-01-01

We describe Symbolic PathFinder v7 in terms of its updated design addressing the changes of Java PathFinder v7 and of its new optimization when computing path conditions. Furthermore, we describe the Symbolic Execution Tree Extension; a newly added feature that allows for outputting the symbolic...... execution tree that characterizes the execution paths covered during symbolic execution. The new extension can be tailored to the needs of subsequent analyses/processing facilities, and we demonstrate this by presenting SPF-Visualizer, which is a tool for customizable visualization of the symbolic execution...

Terrestrial Zone Exoplanets and Life

Science.gov (United States)

Matthews, Brenda

2018-01-01

One of the most exciting results from ALMA has been the detection of significant substructure within protoplanetary disks that can be linked to planet formation processes. For the first time, we are able to observe the process of assembly of material into larger bodies within such disks. It is not possible, however, for ALMA to probe the growth of planets in protoplanetary disks at small radii, i.e., in the terrestrial zone, where we expect rocky terrestrial planets to form. In this regime, the optical depths prohibit observation at the high frequencies observed by ALMA. To probe the effects of planet building processes and detect telltale gaps and signatures of planetary mass bodies at such small separations from the parent star, we require a facility of superior resolution and sensitivity at lower frequencies. The ngVLA is just such a facility. We will present the fundamental science that will be enabled by the ngVLA in protoplanetary disk structure and the formation of planets. In addition, we will discuss the potential for an ngVLA facility to detect the molecules that are the building blocks of life, reaching limits well beyond those reachable with the current generation of telescopes, and also to determine whether such planets will be habitable based on studies of the impact of stars on their nearest planetary neighbours.

Friend Finder (Game)

Science.gov (United States)

... for a spot on the Friend Finder All-Star List. Earn your spot by showing you're savvy when it comes to making friends online . Downloads Please download and share our ... Email Updates Blog Feed Facebook YouTube Twitter The Federal Trade Commission (FTC) is the ...

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.).

Prospects for Detecting Thermal Emission from Terrestrial Exoplanets with JWST

Science.gov (United States)

Kreidberg, Laura

2018-01-01

A plethora of nearby, terrestrial exoplanets has been discovered recently by ground-based surveys. Excitingly, some of these are in the habitable zones of their host stars, and may be hospitable for life. However, all the planets orbit small, cool stars and have considerably different irradiation environments from the Earth, making them vulnerable to atmospheric escape, erosion and collapse. Atmosphere characterization is therefore critical to assessing the planets' habitability. I will discuss possible JWST thermal emission measurements to determine the atmospheric properties of nearby terrestrial planets. I will focus on prospects for detecting physically motivated atmospheres for planets orbiting LHS 1140, GJ 1132, and TRAPPIST-1. I will also discuss the potential for using phase curve observations to determine whether an atmosphere has survived on the non-transiting planet Proxima b.

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.

Water Loss from Young Planets

Science.gov (United States)

Tian, Feng; Güdel, Manuel; Johnstone, Colin P.; Lammer, Helmut; Luger, Rodrigo; Odert, Petra

2018-04-01

Good progress has been made in the past few years to better understand the XUV evolution trend of Sun-like stars, the capture and dissipation of hydrogen dominant envelopes of planetary embryos and protoplanets, and water loss from young planets around M dwarfs. This chapter reviews these recent developments. Observations of exoplanets and theoretical works in the near future will significantly advance our understanding of one of the fundamental physical processes shaping the evolution of solar system terrestrial planets.

Volatile components and continental material of planets

International Nuclear Information System (INIS)

Florenskiy, K.P.; Nikolayeva, O.V.

1984-01-01

It is shown that the continental material of the terrestrial planets varies in composition from planet to planet according to the abundances and composition of true volatiles (H 2 0, CO 2 , etc.) in the outer shells of the planets. The formation of these shells occurs very early in a planet's evolution when the role of endogenous processes is indistinct and continental materials are subject to melting and vaporizing in the absence of an atmosphere. As a result, the chemical properties of continental materials are related not only to fractionation processes but also to meltability and volatility. For planets retaining a certain quantity of true volatile components, the chemical transformation of continental material is characterized by a close interaction between impact melting vaporization and endogeneous geological processes

Studies of Planet Formation using a Hybrid N-body + Planetesimal Code

Science.gov (United States)

Kenyon, Scott J.; Bromley, Benjamin C.; Salamon, Michael (Technical Monitor)

2005-01-01

The goal of our proposal was to use a hybrid multi-annulus planetesimal/n-body code to examine the planetesimal theory, one of the two main theories of planet formation. We developed this code to follow the evolution of numerous 1 m to 1 km planetesimals as they collide, merge, and grow into full-fledged planets. Our goal was to apply the code to several well-posed, topical problems in planet formation and to derive observational consequences of the models. We planned to construct detailed models to address two fundamental issues: 1) icy planets - models for icy planet formation will demonstrate how the physical properties of debris disks, including the Kuiper Belt in our solar system, depend on initial conditions and input physics; and 2) terrestrial planets - calculations following the evolution of 1-10 km planetesimals into Earth-mass planets and rings of dust will provide a better understanding of how terrestrial planets form and interact with their environment. During the past year, we made progress on each issue. Papers published in 2004 are summarized. Summaries of work to be completed during the first half of 2005 and work planned for the second half of 2005 are included.

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 DLR AsteroidFinder for NEOs

Science.gov (United States)

Mottola, Stefano; Kuehrt, Ekkehard; Michaelis, Harald; Hoffmann, Harald; Spietz, Peter; Jansen, Frank; Thimo Grundmann, Jan; Hahn, Gerhard; Montenegro, Sergio; Findlay, Ross; Boerner, Anko; Messina, Gabriele; Behnke, Thomas; Tschentscher, Matthias; Scheibe, Karsten; Mertens, Volker; Heidecke, Ansgar

Potential Earth-impacting asteroids that spend most of their time interior to Earth's orbit are extremely difficult to be observed from the ground and remain largely undetected. Firstly, they are mostly located at small solar elongations, where the sky brightness and their faintness due to the large phase angle prevents their discovery. Secondly, these objects tend to have very long synodic orbital periods, which makes observation opportunities rare and impact warning times short. Because of these limitations, even the advent of next generation ground-based asteroid surveys is not likely to radically improve the situation (Veres et al. Icarus 203, p472, 2009). On the other hand, a small satellite with a suitable design can observe close to the Sun and detect these objects efficiently against a dark sky background. For this reason, DLR, the German Aerospace Center, has selected AsteroidFinder as the first experiment to be launched under its new compact satellite national program. The primary goal of the mission is to detect and characterize Near Earth Objects (NEOs), with a particular focus on the population of objects completely contained within Earth's orbit (IEOs or Inner Earth Objects). Current dynamical models predict the existence of more than 1000 such objects down to a size of 100m, of which, due to the abovementioned observation difficulties, only 10 have been discovered to date. Benefitting from the vantage point of a Low Earth Orbit (LEO), AsteroidFinder makes use of a small optical telescope to scan those regions of the sky that are close to the Sun, and therefore beyond the reach of ground based observatories. By estimating the population, the size and the orbital distribution of IEOs, AsteroidFinder will contribute to our knowledge of the inner Solar System, and to the assessment of the impact hazard for the Earth. A secondary goal of the mission is to demonstrate techniques that enable the space-based detection of space debris in the cm size range

Collisional erosion and the non-chondritic composition of the terrestrial planets.

Science.gov (United States)

O'Neill, Hugh St C; Palme, Herbert

2008-11-28

The compositional variations among the chondrites inform us about cosmochemical fractionation processes during condensation and aggregation of solid matter from the solar nebula. These fractionations include: (i) variable Mg-Si-RLE ratios (RLE: refractory lithophile element), (ii) depletions in elements more volatile than Mg, (iii) a cosmochemical metal-silicate fractionation, and (iv) variations in oxidation state. Moon- to Mars-sized planetary bodies, formed by rapid accretion of chondrite-like planetesimals in local feeding zones within 106 years, may exhibit some of these chemical variations. However, the next stage of planetary accretion is the growth of the terrestrial planets from approximately 102 embryos sourced across wide heliocentric distances, involving energetic collisions, in which material may be lost from a growing planet as well as gained. While this may result in averaging out of the 'chondritic' fractionations, it introduces two non-chondritic chemical fractionation processes: post-nebular volatilization and preferential collisional erosion. In the latter, geochemically enriched crust formed previously is preferentially lost. That post-nebular volatilization was widespread is demonstrated by the non-chondritic Mn/Na ratio in all the small, differentiated, rocky bodies for which we have basaltic samples, including the Moon and Mars. The bulk silicate Earth (BSE) has chondritic Mn/Na, but shows several other compositional features in its pattern of depletion of volatile elements suggestive of non-chondritic fractionation. The whole-Earth Fe/Mg ratio is 2.1+/-0.1, significantly greater than the solar ratio of 1.9+/-0.1, implying net collisional erosion of approximately 10 per cent silicate relative to metal during the Earth's accretion. If this collisional erosion preferentially removed differentiated crust, the assumption of chondritic ratios among all RLEs in the BSE would not be valid, with the BSE depleted in elements according to their

THE STRUCTURE OF SURFACE H{sub 2}O LAYERS OF ICE-COVERED PLANETS WITH HIGH-PRESSURE ICE

Energy Technology Data Exchange (ETDEWEB)

Ueta, S.; Sasaki, T., E-mail: ueta@geo.titech.ac.jp, E-mail: takanori@geo.titech.ac.jp [Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

2013-10-01

Many extrasolar (bound) terrestrial planets and free-floating (unbound) planets have been discovered. While the existence of bound and unbound terrestrial planets with liquid water is an important question, of particular importance is the question of these planets' habitability. Even for a globally ice-covered planet, geothermal heat from the planetary interior may melt the interior ice, creating an internal ocean covered by an ice shell. In this paper, we discuss the conditions that terrestrial planets must satisfy for such an internal ocean to exist on the timescale of planetary evolution. The question is addressed in terms of planetary mass, distance from a central star, water abundance, and abundance of radiogenic heat sources. In addition, we investigate the structure of the surface H{sub 2}O layers of ice-covered planets by considering the effects of ice under high pressure (high-pressure ice). As a fiducial case, a 1 M{sub ⊕} planet at 1 AU from its central star and with 0.6-25 times the H{sub 2}O mass of the Earth could have an internal ocean. We find that high-pressure ice layers may appear between the internal ocean and the rock portion on a planet with an H{sub 2}O mass over 25 times that of the Earth. The planetary mass and abundance of surface water strongly restrict the conditions under which an extrasolar terrestrial planet may have an internal ocean with no high-pressure ice under the ocean. Such high-pressure ice layers underlying the internal ocean are likely to affect the habitability of the planet.

Radioactivity of the moon, planets, and meteorites

Science.gov (United States)

Surkou, Y. A.; Fedoseyev, G. A.

1977-01-01

Analytical data is summarized for the content of natural radioactive elements in meteorites, eruptive terrestrial rocks, and also in lunar samples returned by Apollo missions and the Luna series of automatic stations. The K-U systematics of samples analyzed in the laboratory are combined with data for orbital gamma-ray measurements for Mars (Mars 5) and with the results of direct gamma-ray measurements of the surface of Venus by the Venera 8 lander. Using information about the radioactivity of solar system bodies and evaluations of the content of K, U, and Th in the terrestrial planets, we examine certain aspects of the evolution of material in the protoplanetary gas-dust cloud and then in the planets of the solar system.

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...

47 CFR 80.289 - Requirements for radio direction finder.

Science.gov (United States)

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Requirements for radio direction finder. 80.289... Requirements for radio direction finder. (a) The radio direction finding apparatus must: (1) Be capable of...) Possess a sensitivity, sufficient to permit the taking of bearings on a signal having a field strength of...

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.

THE MASS OF Kepler-93b AND THE COMPOSITION OF TERRESTRIAL PLANETS

Energy Technology Data Exchange (ETDEWEB)

Dressing, Courtney D.; Charbonneau, David; Dumusque, Xavier; Gettel, Sara; Latham, David W.; Buchhave, Lars A.; Johnson, John Asher; Lopez-Morales, Mercedes [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Pepe, Francesco; Udry, Stéphane; Lovis, Christophe [Observatoire Astronomique de l' Université de Genève, 51 ch. des Maillettes, 1290 Versoix (Switzerland); Collier Cameron, Andrew; Haywood, Raphaëlle D. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews Fife KY16 9SS (United Kingdom); Molinari, Emilio; Cosentino, Rosario; Fiorenzano, Aldo F. M.; Harutyunyan, Avet [INAF - Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja (Spain); Affer, Laura [INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90124 Palermo (Italy); Bonomo, Aldo S. [INAF - Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese (Italy); Figueira, Pedro, E-mail: cdressing@cfa.harvard.edu [Centro de Astrofìsica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); and others

2015-02-20

Kepler-93b is a 1.478 ± 0.019 R {sub ⊕} planet with a 4.7 day period around a bright (V = 10.2), astroseismically characterized host star with a mass of 0.911 ± 0.033 M {sub ☉} and a radius of 0.919 ± 0.011 R {sub ☉}. Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02 ± 0.68 M {sub ⊕}. The corresponding high density of 6.88 ± 1.18 g cm{sup –3} is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1 and 6 M {sub ⊕}, all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses >6 M {sub ⊕}. All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1-6 M {sub ⊕} planets.

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.

Surface history of Mercury - Implications for terrestrial planets

Science.gov (United States)

Murray, B. C.; Strom, R. G.; Trask, N. J.; Gault, D. E.

1975-01-01

A plausible surface history of Mercury is presented which is suggested by Mariner 10 television pictures. Five periods are postulated which are delineated by successive variations in the modification of the surface by external and internal processes: accretion and differentiation, terminal heavy bombardment, formation of the Caloris basin, flooding of that basin and other areas, and light cratering accumulated on the smooth plains. Each period is described in detail; the overall history is compared with the surface histories of Venus, Mars, and the moon; and the implications of this history for earth are discussed. It is tentatively concluded that: Mercury is a differentiated planet most likely composed of a large iron core enclosed by a relatively thin silicate layer; heavy surface bombardment occurred about four billion years ago, which probably affected all the inner planets, and was followed by a period of volcanic activity; no surface modifications caused by tectonic, volcanic, or atmospheric processes took place after the volcanic period.

Negotiation of Legitimacy of Witch-Finders in Lusaka

Directory of Open Access Journals (Sweden)

Mildnerová Kateřina

2017-12-01

Full Text Available The article aims at legal and illegal activities of Lusaka´s traditional healers within the system of traditional medicine which is primarily anchored in the constitution of traditional healers´ associations. It primarily focuses on witch-finders, whose social status, professional position and authority is constantly negotiated within the formal and informal sector of traditional medicine. Since the late 1990s, the quest for services of traditional healers specialised in witch-finding has gained popularity, particularly amongst the impoverished Lusaka compound-dwellers. Due to the increasing public violence against those denoted as witches, the activities of witch-finders were officially banned by the Witchcraft Act in 1995 and this profession is not officially recognised by the Constitution of Traditional Health Practitioners Association of Zambia (THAPAZ. In spite of the prohibition, there remain many witch-finders in Lusaka who practise witch-finding secretly, in order not to commit an offence they do not openly denounce the name of an alleged witch. Their authority and credibility is threatened by many “official” as well as “unofficial” competitors in the city and it must be constantly reaffirmed and negotiated by introducing innovations. The ability to keep clients and to gain a good reputation thus depends on the originality of their diagnostic and therapeutic procedures. At the same time witch-finders must counter diverse obstacles and uncertainties resulting from their illegal status within the sector of traditional medicine. The author analyses tactics that Lusaka´s witch-finders have developed and employed to negotiate their social status, credibility and authority visà-vis the competition from the “official” traditional healers.

Twitter Finder

OpenAIRE

Gil Blazquez, Lander

2016-01-01

La aplicación web a desarrollar se llama Twitter Finder. Se trata de una página web en la que cabe destacar como partes más importantes un buscador y un mapa. El usuario podrá hacer búsquedas de una o varias palabras clave a través del buscador. Con la búsqueda realizada y con la ayuda de la API de Twitter, se obtendrán los últimos tweets escritos que contengan el texto de la búsqueda,almacenándolos en la base de datos.

Fault finder

Science.gov (United States)

Bunch, Richard H.

1986-01-01

A fault finder for locating faults along a high voltage electrical transmission line. Real time monitoring of background noise and improved filtering of input signals is used to identify the occurrence of a fault. A fault is detected at both a master and remote unit spaced along the line. A master clock synchronizes operation of a similar clock at the remote unit. Both units include modulator and demodulator circuits for transmission of clock signals and data. All data is received at the master unit for processing to determine an accurate fault distance calculation.

Continuous reorientation of synchronous terrestrial planets due to mantle convection

Science.gov (United States)

Leconte, Jérémy

2018-02-01

Many known rocky exoplanets are thought to have been spun down by tidal interactions to a state of synchronous rotation, in which a planet's period of rotation is equal to that of its orbit around its host star. Investigations into atmospheric and surface processes occurring on such exoplanets thus commonly assume that day and night sides are fixed with respect to the surface over geological timescales. Here we use an analytical model to show that true polar wander—where a planetary body's spin axis shifts relative to its surface because of changes in mass distribution—can continuously reorient a synchronous rocky exoplanet. As occurs on Earth, we find that even weak mantle convection in a rocky exoplanet can produce density heterogeneities within the mantle sufficient to reorient the planet. Moreover, we show that this reorientation is made very efficient by the slower rotation rate of a synchronous planet when compared with Earth, which limits the stabilizing effect of rotational and tidal deformations. Furthermore, a relatively weak lithosphere limits its ability to support remnant loads and stabilize against reorientation. Although uncertainties exist regarding the mantle and lithospheric evolution of these worlds, we suggest that the axes of smallest and largest moment of inertia of synchronous exoplanets with active mantle convection change continuously over time, but remain closely aligned with the star-planet and orbital axes, respectively.

BookFinder.com

CERN Document Server

BookFinder.com is produced by the bibliophiles at 13th Generation Media of Berkeley, California. Our goal is to provide fellow readers unbiased realtime information about books available online. Rather than selling books ourselves (does the world rea Amazon.com wannabe?), we've teamed up with over 15,000 of the finest booksellers online to bring you the largest book catalog available anywhere, either online or offline.

Comparative ionospheres: Terrestrial and giant planets

Science.gov (United States)

Mendillo, Michael; Trovato, Jeffrey; Moore, Luke; Müller-Wodarg, Ingo

2018-03-01

The study of planetary ionospheres within our solar system offers a variety of settings to probe mechanisms of photo-ionization, chemical loss, and plasma transport. Ionospheres are a minor component of upper atmospheres, and thus their mix of ions observed depends on the neutral gas composition of their parent atmospheres. The same solar irradiance (x-rays and extreme-ultra-violet vs. wavelength) impinges upon each of these atmospheres, with solar flux magnitudes changed only by the inverse square of distance from the Sun. If all planets had the same neutral atmosphere-with ionospheres governed by photochemical equilibrium (production = loss)-their peak electron densities would decrease as the inverse of distance from the Sun, and any changes in solar output would exhibit coherent effects throughout the solar system. Here we examine the outer planet with the most observations of its ionosphere (Saturn) and compare its patterns of electron density with those at Earth under the same-day solar conditions. We show that, while the average magnitudes of the major layers of molecular ions at Earth and Saturn are approximately in accord with distance effects, only minor correlations exist between solar effects and day-to-day electron densities. This is in marked contrast to the strong correlations found between the ionospheres of Earth and Mars. Moreover, the variability observed for Saturn's ionosphere (maximum electron density and total electron content) is much larger than found at Earth and Mars. With solar irradiance changes far too small to cause such effects, we use model results to explore the roles of other agents. We find that water sources from Enceladus at low latitudes, and 'ring rain' at middle latitudes, contribute substantially to variability via water ion chemistry. Thermospheric winds and electrodynamics generated at auroral latitudes are suggested causes of high latitude ionospheric variability, but remain inconclusive due to the lack of relevant

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.

Accretion of Planetesimals and the Formation of Rocky Planets

Science.gov (United States)

Chambers, John E.; O'Brien, David P.; Davis, Andrew M.

2010-02-01

Here we describe the formation of rocky planets and asteroids in the context of the planetesimal hypothesis. Small dust grains in protoplanetary disks readily stick together forming mm-to-cm-sized aggregates, many of which experience brief heating episodes causing melting. Growth to km-sized planetesimals might proceed via continued pairwise sticking, turbulent concentration, or gravitational instability of a thin particle layer. Gravitational interactions between planetesimals lead to rapid runaway and oligarchic growth forming lunar-to-Mars-sized protoplanets in 10^5 to 10^6 years. Giant impacts between protoplanets form Earth-mass planets in 10^7 to 10^8 years, and occasionally lead to the formation of large satellites. Protoplanets may migrate far from their formation locations due to tidal interactions with the surrounding disk. Radioactive decay and impact heating cause melting and differentiation of planetesimals and protoplanets, forming iron-rich cores and silicate mantles, and leading to some loss of volatiles. Dynamical perturbations from giant planets eject most planetesimals and protoplanets from regions near orbital resonances, leading to asteroid-belt formation. Some of this scattered material will collide with growing terrestrial planets, altering their composition as a result. Numerical simulations and radioisotope dating indicate that the terrestrial planets of the Solar System were essentially fully formed in 100-200 million years.

Characterizing Cool Giant Planets in Reflected Light

Science.gov (United States)

Marley, Mark

2016-01-01

While the James Webb Space Telescope will detect and characterize extrasolar planets by transit and direct imaging, a new generation of telescopes will be required to detect and characterize extrasolar planets by reflected light imaging. NASA's WFIRST space telescope, now in development, will image dozens of cool giant planets at optical wavelengths and will obtain spectra for several of the best and brightest targets. This mission will pave the way for the detection and characterization of terrestrial planets by the planned LUVOIR or HabEx space telescopes. In my presentation I will discuss the challenges that arise in the interpretation of direct imaging data and present the results of our group's effort to develop methods for maximizing the science yield from these planned missions.

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.

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.

Planets, stars and stellar systems

CERN Document Server

Bond, Howard; McLean, Ian; Barstow, Martin; Gilmore, Gerard; Keel, William; French, Linda

2013-01-01

This is volume 3 of Planets, Stars and Stellar Systems, a six-volume compendium of modern astronomical research covering subjects of key interest to the main fields of contemporary astronomy. This volume on “Solar and Stellar Planetary Systems” edited by Linda French and Paul Kalas presents accessible review chapters From Disks to Planets, Dynamical Evolution of Planetary Systems, The Terrestrial Planets, Gas and Ice Giant Interiors, Atmospheres of Jovian Planets, Planetary Magnetospheres, Planetary Rings, An Overview of the Asteroids and Meteorites, Dusty Planetary Systems and Exoplanet Detection Methods. All chapters of the handbook were written by practicing professionals. They include sufficient background material and references to the current literature to allow readers to learn enough about a specialty within astronomy, astrophysics and cosmology to get started on their own practical research projects. In the spirit of the series Stars and Stellar Systems published by Chicago University Press in...

Large-scale impact cratering on the terrestrial planets

International Nuclear Information System (INIS)

Grieve, R.A.F.

1982-01-01

The crater densities on the earth and moon form the basis for a standard flux-time curve that can be used in dating unsampled planetary surfaces and constraining the temporal history of endogenic geologic processes. Abundant evidence is seen not only that impact cratering was an important surface process in planetary history but also that large imapact events produced effects that were crucial in scale. By way of example, it is noted that the formation of multiring basins on the early moon was as important in defining the planetary tectonic framework as plate tectonics is on the earth. Evidence from several planets suggests that the effects of very-large-scale impacts go beyond the simple formation of an impact structure and serve to localize increased endogenic activity over an extended period of geologic time. Even though no longer occurring with the frequency and magnitude of early solar system history, it is noted that large scale impact events continue to affect the local geology of the planets. 92 references

Physical and Mathematical Questions on Signal Processing in Multibase Phase Direction Finders

Science.gov (United States)

Denisov, V. P.; Dubinin, D. V.; Meshcheryakov, A. A.

2018-02-01

Questions on improving the accuracy of multiple-base phase direction finders by rejecting anomalously large errors in the process of resolving the measurement ambiguities are considered. A physical basis is derived and calculated relationships characterizing the efficiency of the proposed solutions are obtained. Results of a computer simulation of a three-base direction finder are analyzed, along with field measurements of a three-base direction finder along near-ground paths.

The metallicities of stars with and without transiting planets

DEFF Research Database (Denmark)

Buchhave, Lars A.; Latham, David W.

2015-01-01

Host star metallicities have been used to infer observational constraints on planet formation throughout the history of the exoplanet field. The giant planet metallicity correlation has now been widely accepted, but questions remain as to whether the metallicity correlation extends to the small...... terrestrial-sized planets. Here, we report metallicities for a sample of 518 stars in the Kepler field that have no detected transiting planets and compare their metallicity distribution to a sample of stars that hosts small planets (). Importantly, both samples have been analyzed in a homogeneous manner...... using the same set of tools (Stellar Parameters Classification tool). We find the average metallicity of the sample of stars without detected transiting planets to be and the sample of stars hosting small planets to be . The average metallicities of the two samples are indistinguishable within...

MIGRATION OF PLANETS EMBEDDED IN A CIRCUMSTELLAR DISK

International Nuclear Information System (INIS)

Bromley, Benjamin C.; Kenyon, Scott J.

2011-01-01

Planetary migration poses a serious challenge to theories of planet formation. In gaseous and planetesimal disks, migration can remove planets as quickly as they form. To explore migration in a planetesimal disk, we combine analytic and numerical approaches. After deriving general analytic migration rates for isolated planets, we use N-body simulations to confirm these results for fast and slow migration modes. Migration rates scale as m -1 (for massive planets) and (1 + (e H /3) 3 ) -1 , where m is the mass of a planet and e H is the eccentricity of the background planetesimals in Hill units. When multiple planets stir the disk, our simulations yield the new result that large-scale migration ceases. Thus, growing planets do not migrate through planetesimal disks. To extend these results to migration in gaseous disks, we compare physical interactions and rates. Although migration through a gaseous disk is an important issue for the formation of gas giants, we conclude that migration has little impact on the formation of terrestrial planets.

Mercury - Introduction to an end-member planet

International Nuclear Information System (INIS)

Chapman, C.R.

1988-01-01

This chapter introduces the major themes of this book. In many ways, Mercury is an extreme planet, and thus it provides a unique benchmark for testing our theories about the origin and evolution of other (particularly terrestrial) planets. Emphasis is given to synthesizing and critiquing the book's chapters on the planet's origin, its metal-rich composition, its thermal and geophysical evolution, and its cratering history; these topics are complex and controversial, and this book contains a variety of new perspectives on them. Mercury's geology, atmosphere and magnetosphere are discussed more briefly. The study of Mercury is placed in its historical context and in the context of the spacecraft exploration program, both past and future

The occurrence of Jovian planets and the habitability of planetary systems

OpenAIRE

Lunine, Jonathan I.

2001-01-01

Planets of mass comparable to or larger than Jupiter's have been detected around over 50 stars, and for one such object a definitive test of its nature as a gas giant has been accomplished with data from an observed planetary transit. By virtue of their strong gravitational pull, giant planets define the dynamical and collisional environment within which terrestrial planets form. In our solar system, the position and timing of the formation of Jupiter determined the am...

First Light from Extrasolar Planets and Implications for Astrobiology

Science.gov (United States)

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

2005-01-01

The first light from an extrasolar planet was recently detected. These results, obtained for two transiting extrasolar planets at different infrared wavelengths, open a new era in the field of extrasolar planet detection and characterization because for the first time we can now detect planets beyond the solar system directly. Using the Spitzer Space Telescope at 24 microns, we observed the modulation of combined light (star plus planet) from the HD 209458 system as the planet disappeared behind the star during secondary eclipse and later re-emerged, thereby isolating the light from the planet. We obtained a planet-to-star ratio of 0.26% at 24 microns, corresponding to a brightness temperature of 1130 + / - 150 K. We will describe this result in detail, explain what it can tell us about the atmosphere of HD 209458 b, and discuss implications for the field of astrobiology. These results represent a significant step on the path to detecting terrestrial planets around other stars and in understanding their atmospheres in terms of composition and temperature.

The PIAA Coronagraph: Optical design and Diffraction Effects

Science.gov (United States)

Pluzhnik, E. A.; Guyon, O.; Ridgway, S.; Martinache, F.; Woodruff, R.; Blain, C.; Galicher, R.

2005-12-01

Properly apodized pupils are suitable for high dynamical range imaging of extrasolar terrestrial planets. Phase-induced amplitude apodization (PIAA) of the telescope pupil (Guyon 2003) combines the advantages of classical pupil apodization with full throughput, no loss of angular resolution and low chromaticity. Diffraction propagation effects can decrease both the achieved contrast and the spectral bandwidth of the coronagraph. We show here how the diffraction effects in the PIAA optics can be corrected by an appropriate optical design. The proposed hybrid coronagraph design preserves the 10-10 PSF contrast at ≈ 1.5 λ /d required for efficient exoplanet imaging over the whole visible spectrum. This work was carried out under JPL contract numbers 1254445 and 1257767 for Development of Technologies for the Terrestrial Planet Finder Mission, with the support and hospitality of the National Astronomical Observatory of Japan.

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...

FORMING HABITABLE PLANETS AROUND DWARF STARS: APPLICATION TO OGLE-06-109L

International Nuclear Information System (INIS)

Wang Su; Zhou Jilin

2011-01-01

Dwarf stars are believed to have a small protostar disk where planets may grow up. During the planet formation stage, embryos undergoing type I migration are expected to be stalled at an inner edge of the magnetically inactive disk (a crit ∼ 0.2-0.3 AU). This mechanism makes the location around a crit a 'sweet spot' for forming planets. In dwarf stars with masses ∼0.5 M sun , a crit is roughly inside the habitable zone of the system. In this paper, we study the formation of habitable planets due to this mechanism using model system OGLE-06-109L, which has a 0.51 M sun dwarf star with two giant planets in 2.3 and 4.6 AU observed by microlensing. We model the embryos undergoing type I migration in the gas disk with a constant disk-accretion rate ( M-dot ). Giant planets in outside orbits affect the formation of habitable planets through secular perturbations at the early stage and secular resonance at the late stage. We find that the existence and the masses of the habitable planets in the OGLE-06-109L system depend on both M-dot and the speed of type I migration. If planets are formed earlier, so that M-dot is larger (∼10 -7 M sun yr -1 ), terrestrial planets cannot survive unless the type I migration rate is an order of magnitude less. If planets are formed later, so that M-dot is smaller (∼10 -8 M sun yr -1 ), single and high-mass terrestrial planets with high water contents (∼5%) will be formed by inward migration of outer planet cores. A slower-speed migration will result in several planets via collisions of embryos, and thus their water contents will be low (∼2%). Mean motion resonances or apsidal resonances among planets may be observed if multiple planets survive in the inner system.

YOUNG SOLAR SYSTEM's FIFTH GIANT PLANET?

International Nuclear Information System (INIS)

Nesvorný, David

2011-01-01

Studies of solar system formation suggest that the solar system's giant planets formed and migrated in the protoplanetary disk to reach the resonant orbits with all planets inside ∼15 AU from the Sun. After the gas disk's dispersal, Uranus and Neptune were likely scattered by the gas giants, and approached their current orbits while dispersing the transplanetary disk of planetesimals, whose remains survived to this time in the region known as the Kuiper Belt. Here we performed N-body integrations of the scattering phase between giant planets in an attempt to determine which initial states are plausible. We found that the dynamical simulations starting with a resonant system of four giant planets have a low success rate in matching the present orbits of giant planets and various other constraints (e.g., survival of the terrestrial planets). The dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, and leads to final systems with fewer than four planets. Several initial states stand out in that they show a relatively large likelihood of success in matching the constraints. Some of the statistically best results were obtained when assuming that the solar system initially had five giant planets and one ice giant, with the mass comparable to that of Uranus and Neptune, and which was ejected to interstellar space by Jupiter. This possibility appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, which indicates that planet ejection should be common.

Young Solar System's Fifth Giant Planet?

Science.gov (United States)

Nesvorný, David

2011-12-01

Studies of solar system formation suggest that the solar system's giant planets formed and migrated in the protoplanetary disk to reach the resonant orbits with all planets inside ~15 AU from the Sun. After the gas disk's dispersal, Uranus and Neptune were likely scattered by the gas giants, and approached their current orbits while dispersing the transplanetary disk of planetesimals, whose remains survived to this time in the region known as the Kuiper Belt. Here we performed N-body integrations of the scattering phase between giant planets in an attempt to determine which initial states are plausible. We found that the dynamical simulations starting with a resonant system of four giant planets have a low success rate in matching the present orbits of giant planets and various other constraints (e.g., survival of the terrestrial planets). The dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, and leads to final systems with fewer than four planets. Several initial states stand out in that they show a relatively large likelihood of success in matching the constraints. Some of the statistically best results were obtained when assuming that the solar system initially had five giant planets and one ice giant, with the mass comparable to that of Uranus and Neptune, and which was ejected to interstellar space by Jupiter. This possibility appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, which indicates that planet ejection should be common.

RxnFinder: biochemical reaction search engines using molecular structures, molecular fragments and reaction similarity.

Science.gov (United States)

Hu, Qian-Nan; Deng, Zhe; Hu, Huanan; Cao, Dong-Sheng; Liang, Yi-Zeng

2011-09-01

Biochemical reactions play a key role to help sustain life and allow cells to grow. RxnFinder was developed to search biochemical reactions from KEGG reaction database using three search criteria: molecular structures, molecular fragments and reaction similarity. RxnFinder is helpful to get reference reactions for biosynthesis and xenobiotics metabolism. RxnFinder is freely available via: http://sdd.whu.edu.cn/rxnfinder. qnhu@whu.edu.cn.

Comparison of three multiplex PCR assays for the detection of respiratory viral infections: evaluation of xTAG respiratory virus panel fast assay, RespiFinder 19 assay and RespiFinder SMART 22 assay

Directory of Open Access Journals (Sweden)

Dabisch-Ruthe Mareike

2012-07-01

Full Text Available Abstract Background A broad spectrum of pathogens is causative for respiratory tract infections, but symptoms are mostly similar. Therefore, the identification of the causative viruses and bacteria is only feasible using multiplex PCR or several monoplex PCR tests in parallel. Methods The analytical sensitivity of three multiplex PCR assays, RespiFinder-19, RespiFinder-SMART-22 and xTAG-Respiratory-Virus-Panel-Fast-Assay (RVP, were compared to monoplex real-time PCR with quantified standardized control material. All assays include the most common respiratory pathogens. Results To compare the analytical sensitivity of the multiplex assays, samples were inoculated with 13 different quantified viruses in the range of 101 to 105 copies/ml. Concordant results were received for rhinovirus, whereas the RVP detected influenzavirus, RSV and hMPV more frequently in low concentrations. The RespiFinder-19 and the RespiFinder-SMART-22 showed a higher analytical sensitivity for adenoviruses and coronaviruses, whereas the RVP was incapable to detect adenovirus and coronavirus in concentrations of 104 copies/ml. The RespiFinder-19 and RespiFinder-SMART-22A did not detect influenzaviruses (104 copies/ml and RSV (103 copies/ml. The detection of all 13 viruses in one sample was only achieved using monoplex PCR. To analyze possible competitive amplification reactions between the different viruses, samples were further inoculated with only 4 different viruses in one sample. Compared to the detection of 13 viruses in parallel, only a few differences were found. The incidence of respiratory viruses was compared in tracheal secretion (TS samples (n = 100 of mechanically ventilated patients in winter (n = 50 and summer (n = 50. In winter, respiratory viruses were detected in 32 TS samples (64% by RespiFinder-19, whereas the detection rate with RVP was only 22%. The most frequent viruses were adenovirus (32% and PIV-2 (20%. Multiple infections were detected

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.

PathogenFinder - Distinguishing Friend from Foe Using Bacterial Whole Genome Sequence Data

DEFF Research Database (Denmark)

Cosentino, Salvatore; Larsen, Mette Voldby; Aarestrup, Frank Møller

2013-01-01

approaches. We describe PathogenFinder (http://cge.cbs.dtu.dk/services/PathogenFinder/), a web-server for the prediction of bacterial pathogenicity by analysing the input proteome, genome, or raw reads provided by the user. The method relies on groups of proteins, created without regard to their annotated...

Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

OpenAIRE

Yang, Jun; Cowan, Nicolas B.; Abbot, Dorian S.

2013-01-01

The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to sho...

A Versatile Technique to Enable Sub-milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-zone Planet Finder

Science.gov (United States)

Stefansson, Gudmundur; Hearty, Frederick; Robertson, Paul; Mahadevan, Suvrath; Anderson, Tyler; Levi, Eric; Bender, Chad; Nelson, Matthew; Monson, Andrew; Blank, Basil; Halverson, Samuel; Henderson, Chuck; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan

2016-12-01

Insufficient instrument thermomechanical stability is one of the many roadblocks for achieving 10 cm s-1 Doppler radial velocity precision, the precision needed to detect Earth-twins orbiting solar-type stars. Highly temperature and pressure stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing instrumental noise from astrophysical stellar signals. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared (NIR) spectrograph for the 10 {{m}} Hobby-Eberly Telescope at McDonald Observatory. HPF will operate at 180 {{K}}, driven by the choice of an H2RG NIR detector array with a 1.7 μ {{m}} cutoff. This ECS has demonstrated 0.6 {mK} rms stability over 15 days at both 180 and 300 {{K}}, and maintained high-quality vacuum (\\lt {10}-7 {Torr}) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high-precision Doppler instruments over a wide temperature range from ˜77 {{K}} to elevated room temperatures. A similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 {{m}} WIYN telescope at Kitt Peak, operating at 300 {{K}}. A [full SolidWorks 3D-CAD model] and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community. Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment

LISA and LISA PathFinder, the endeavour to detect low frequency GWs

Energy Technology Data Exchange (ETDEWEB)

Araujo, H [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Boatella, C [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Chmeissani, M [Institut de Fisica d' Altes Energies (IFAE), Edifici C, Universitat Autonoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Conchillo, A [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Garcia-Berro, E [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Grimani, C [Universita degli Studi di Urbino, and INFN Florence, Istituto di Fisica, Via Santa Chiara 27, 61029 Urbino (Italy); Hajdas, W [Department of Particles and Matter, Paul Scherrer Institut, ODRA 120, 5232 Villigen (Switzerland); Lobo, A [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Martinez, L [AtIpic, Parc Tecnologic del Valles, 08290 Cerdanyola del Valles, Barcelona (Spain); Nofrarias, M [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Ortega, J A [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Puigdengoles, C [Institut de Fisica d' Altes Energies (IFAE), Edifici C, Universitat Autonoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Ramos-Castro, J [Departament d' Enginyeria Electronica, UPC, Campus Nord, Edif. C4, Jordi Girona 1-3, 08034 Barcelona (Spain); Sanjuan, J [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain); Wass, P [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Xirgu, X [Institut d' Estudis Espacials de Catalunya (IEEC), Edifici Nexus, Gran Capita 2-4, 08034 Barcelona (Spain)

2007-05-15

This is a review about LISA and its technology demonstrator, LISAPathFinder. We first describe the conceptual problems which need to be overcome in order to set up a working interferometric detector of low frequency Gravitational Waves (GW), then summarise the solutions to them as currently conceived by the LISA mission team. This will show that some of these solutions require new technological abilities which are still under development, and which need proper test before being fully implemented. LISAPathFinder (LPF) is the the testbed for such technologies. The final part of the paper will address the ideas and concepts behind the PathFinder as well as their impact on LISA.

LISA and LISA PathFinder, the endeavour to detect low frequency GWs

International Nuclear Information System (INIS)

Araujo, H; Boatella, C; Chmeissani, M; Conchillo, A; Garcia-Berro, E; Grimani, C; Hajdas, W; Lobo, A; Martinez, L; Nofrarias, M; Ortega, J A; Puigdengoles, C; Ramos-Castro, J; Sanjuan, J; Wass, P; Xirgu, X

2007-01-01

This is a review about LISA and its technology demonstrator, LISAPathFinder. We first describe the conceptual problems which need to be overcome in order to set up a working interferometric detector of low frequency Gravitational Waves (GW), then summarise the solutions to them as currently conceived by the LISA mission team. This will show that some of these solutions require new technological abilities which are still under development, and which need proper test before being fully implemented. LISAPathFinder (LPF) is the the testbed for such technologies. The final part of the paper will address the ideas and concepts behind the PathFinder as well as their impact on LISA

Parallel 4-dimensional cellular automaton track finder for the CBM experiment

Energy Technology Data Exchange (ETDEWEB)

Akishina, Valentina [Goethe-Universitaet Frankfurt am Main, Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); JINR Joint Institute for Nuclear Research, Dubna (Russian Federation); Kisel, Ivan [Goethe-Universitaet Frankfurt am Main, Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Collaboration: CBM-Collaboration

2016-07-01

The CBM experiment at FAIR will focus on the measurement of rare probes at interaction rates up to 10 MHz. The beam will provide free stream of particles, so that information about different collisions may overlap in time. It requires the full online event reconstruction not only in space, but also in time, so-called 4D (4-dimensional) event building. This is a task of the First-Level Event Selection (FLES) package. The FLES reconstruction package consists of several modules: track finding, track fitting, short-lived particles finding, event building and selection. The Silicon Tracking System (STS) time measurement information was included into the Cellular Automaton (CA) track finder algorithm. The 4D track finder algorithm speed (8.5 ms per event in a time-slice) and efficiency is comparable with the event-based analysis. The CA track finder was fully parallelised inside the time-slice. The parallel version achieves a speed-up factor of 10.6 while parallelising between 10 Intel Xeon physical cores with a hyper-threading. The first version of event building based on 4D track finder was implemented.

The hardware track finder processor in CMS at CERN

CERN Document Server

Kluge, A

1997-01-01

The work covers the design of the Track Finder Processor in the high energy experiment CMS (Compact Muon Solenoid, planned for 2005) at CERN/Geneva. The task of this processor is to identify muons and measure their transverse momentum. The track finder processor makes it possible to determine the physical relevance of each high energetic collision and to forward only interesting data to the data an alysis units. Data of more than two hundred thousand detector cells are used to determine the location of muons and measure their transverse momentum. Each 25 ns a new data set is generated. Measurem ent of location and transverse momentum of the muons can be terminated within 350 ns by using an ASIC (Application Specific Integrated Circuit). A pipeline architecture processes new data sets with th e required data rate of 40 MHz to ensure dead time free operation. In the framework of this study specifications and the overall concept of the track finder processor were worked out in detail. Simul ations were performed...

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.

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...

RETRATAMENTO ENDODÔNTICO: ESTUDO COMPARATIVO ENTRE TÉCNICA MANUAL, ULTRA-SOM E CANAL FINDER ENDODONTIC RETREATMENT: COMPARATIVE STUDY BETWEEN MANUAL TECHNIQUE, ULTRASONIC SCALER, AND CANAL FINDER

Directory of Open Access Journals (Sweden)

Clovis Monteiro BRAMANTE

1998-01-01

Full Text Available Instrumentações manual, ultra-sônica e com Canal Finder foram utilizadas para retratamento de 30 dentes com canais obturados com guta-percha e óxido de zinco e eugenol. Avaliaram-se: 1. tempo gasto para a penetração inicial até o ápice; 2. tempo para completar a limpeza; 3. extrusão de material e 4. limpeza dos canais. O Canal Finder foi a técnica que propiciou melhor limpeza, seguida da manual e da ultra-sônica. A parede palatina do canal foi constantemente mais limpa do que a vestibular. Quanto à extrusão, a técnica de ultra-som foi a que propiciou mais extravasamento de material obturador.Endodontic retreatment of 30 teeth filled with guta percha and zinc oxide-eugenol was carried out using manual instrumentation, ultrasonic scaler, and the Canal Finder System. The following variables were evaluated: time spent to reach the apex; time spent to complete cleaning of the canal; apical extrusion of material; and cleanliness of the canals. Results showed the Canal Finder System as providing the highest level of cleanliness of the canal system; lingual walls were constantly cleaner than buccal walls; ultrasonic technique presented a greater degree of apical extrusion of filling material.

Planet Formation

Science.gov (United States)

Podolak, Morris

2018-04-01

Modern observational techniques are still not powerful enough to directly view planet formation, and so it is necessary to rely on theory. However, observations do give two important clues to the formation process. The first is that the most primitive form of material in interstellar space exists as a dilute gas. Some of this gas is unstable against gravitational collapse, and begins to contract. Because the angular momentum of the gas is not zero, it contracts along the spin axis, but remains extended in the plane perpendicular to that axis, so that a disk is formed. Viscous processes in the disk carry most of the mass into the center where a star eventually forms. In the process, almost as a by-product, a planetary system is formed as well. The second clue is the time required. Young stars are indeed observed to have gas disks, composed mostly of hydrogen and helium, surrounding them, and observations tell us that these disks dissipate after about 5 to 10 million years. If planets like Jupiter and Saturn, which are very rich in hydrogen and helium, are to form in such a disk, they must accrete their gas within 5 million years of the time of the formation of the disk. Any formation scenario one proposes must produce Jupiter in that time, although the terrestrial planets, which don't contain significant amounts of hydrogen and helium, could have taken longer to build. Modern estimates for the formation time of the Earth are of the order of 100 million years. To date there are two main candidate theories for producing Jupiter-like planets. The core accretion (CA) scenario supposes that any solid materials in the disk slowly coagulate into protoplanetary cores with progressively larger masses. If the core remains small enough it won't have a strong enough gravitational force to attract gas from the surrounding disk, and the result will be a terrestrial planet. If the core grows large enough (of the order of ten Earth masses), and the disk has not yet dissipated, then

Basic Testing of the DUCHAMP Source Finder

Science.gov (United States)

Westmeier, T.; Popping, A.; Serra, P.

2012-01-01

This paper presents and discusses the results of basic source finding tests in three dimensions (using spectroscopic data cubes) with DUCHAMP, the standard source finder for the Australian Square Kilometre Array Pathfinder. For this purpose, we generated different sets of unresolved and extended Hi model sources. These models were then fed into DUCHAMP, using a range of different parameters and methods provided by the software. The main aim of the tests was to study the performance of DUCHAMP on sources with different parameters and morphologies and assess the accuracy of DUCHAMP's source parametrisation. Overall, we find DUCHAMP to be a powerful source finder capable of reliably detecting sources down to low signal-to-noise ratios and accurately measuring their position and velocity. In the presence of noise in the data, DUCHAMP's measurements of basic source parameters, such as spectral line width and integrated flux, are affected by systematic errors. These errors are a consequence of the effect of noise on the specific algorithms used by DUCHAMP for measuring source parameters in combination with the fact that the software only takes into account pixels above a given flux threshold and hence misses part of the flux. In scientific applications of DUCHAMP these systematic errors would have to be corrected for. Alternatively, DUCHAMP could be used as a source finder only, and source parametrisation could be done in a second step using more sophisticated parametrisation algorithms.

trieFinder: an efficient program for annotating Digital Gene Expression (DGE) tags.

Science.gov (United States)

Renaud, Gabriel; LaFave, Matthew C; Liang, Jin; Wolfsberg, Tyra G; Burgess, Shawn M

2014-10-13

Quantification of a transcriptional profile is a useful way to evaluate the activity of a cell at a given point in time. Although RNA-Seq has revolutionized transcriptional profiling, the costs of RNA-Seq are still significantly higher than microarrays, and often the depth of data delivered from RNA-Seq is in excess of what is needed for simple transcript quantification. Digital Gene Expression (DGE) is a cost-effective, sequence-based approach for simple transcript quantification: by sequencing one read per molecule of RNA, this technique can be used to efficiently count transcripts while obviating the need for transcript-length normalization and reducing the total numbers of reads necessary for accurate quantification. Here, we present trieFinder, a program specifically designed to rapidly map, parse, and annotate DGE tags of various lengths against cDNA and/or genomic sequence databases. The trieFinder algorithm maps DGE tags in a two-step process. First, it scans FASTA files of RefSeq, UniGene, and genomic DNA sequences to create a database of all tags that can be derived from a predefined restriction site. Next, it compares the experimental DGE tags to this tag database, taking advantage of the fact that the tags are stored as a prefix tree, or "trie", which allows for linear-time searches for exact matches. DGE tags with mismatches are analyzed by recursive calls in the data structure. We find that, in terms of alignment speed, the mapping functionality of trieFinder compares favorably with Bowtie. trieFinder can quickly provide the user an annotation of the DGE tags from three sources simultaneously, simplifying transcript quantification and novel transcript detection, delivering the data in a simple parsed format, obviating the need to post-process the alignment results. trieFinder is available at http://research.nhgri.nih.gov/software/trieFinder/.

Flood Finder: Mobile-based automated water level estimation and mapping during floods

International Nuclear Information System (INIS)

Pongsiriyaporn, B; Jariyavajee, C; Laoharawee, N; Narkthong, N; Pitichat, T; Goldin, S E

2014-01-01

Every year, Southeast Asia faces numerous flooding disasters, resulting in very high human and economic loss. Responding to a sudden flood is difficult due to the lack of accurate and up-to- date information about the incoming water status. We have developed a mobile application called Flood Finder to solve this problem. Flood Finder allows smartphone users to measure, share and search for water level information at specified locations. The application uses image processing to compute the water level from a photo taken by users. The photo must be of a known reference object with a standard size. These water levels are more reliable and consistent than human estimates since they are derived from an algorithmic measuring function. Flood Finder uploads water level readings to the server, where they can be searched and mapped by other users via the mobile phone app or standard browsers. Given the widespread availability of smartphones in Asia, Flood Finder can provide more accurate and up-to-date information for better preparation for a flood disaster as well as life safety and property protection

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.

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 formation of planets by disc fragmentation

Directory of Open Access Journals (Sweden)

Stamatellos Dimitris

2013-04-01

Full Text Available I discuss the role that disc fragmentation plays in the formation of gas giant and terrestrial planets, and how this relates to the formation of brown dwarfs and low-mass stars, and ultimately to the process of star formation. Protostellar discs may fragment, if they are massive enough and can cool fast enough, but most of the objects that form by fragmentation are brown dwarfs. It may be possible that planets also form, if the mass growth of a proto-fragment is stopped (e.g. if this fragment is ejected from the disc, or suppressed and even reversed (e.g by tidal stripping. I will discuss if it is possible to distinguish whether a planet has formed by disc fragmentation or core accretion, and mention of a few examples of observed exoplanets that are suggestive of formation by disc fragmentation.

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;

Crustal development in the terrestrial planets

Science.gov (United States)

Taylor, S. R.

1985-01-01

The development of planetary crusts may be divided into primary, resulting from melting during accretion, and secondary crusts developed by partial melting from planetary mantles. The Mercurian crust is probably primary with no compelling evidence of later basaltic extrusions. Reflectance spectral evidence for the existence Fe2(+) is equivocal. The Viking Lander XRF data on Mars indicate basaltic material at both sites 4,000 km apart. Surface aeolian processes would be expected to provide a homogeneous average of the crust, but no evidence of more siliceous material is present. This conclusion is weakly supported by the Russian gamma ray data. No evidence for granite appears from the Russian Venera XRF data which indicates MORB-type and alkali basalt (4% K2O) surface compositions. The highlands of Ishtar Terra and Aphrodite probably owe their elevation to tectonic processes rather than compositional effects. Venus may thus resemble the early Archean Earth. The terrestrial granitic continental crust is a product of episodic multiple partial melting events, probably a consequence of the presence of surface water.

Tidally Heated Terrestrial Exoplanets

Science.gov (United States)

Henning, Wade Garrett

This work models the surface and internal temperatures for hypothetical terrestrial planets in situations involving extreme tidal heating. The feasibility of such planets is evaluated in terms of the orbital perturbations that may give rise to them, their required proximity to a hoststar, and the potential for the input tidal heating to cause significant partial melting of the mantle. Trapping terrestrial planets into 2:1 resonances with migrating Hot Jupiters is considered as a reasonable way for Earth-like worlds to both maintain high eccentricities and to move to short enough orbital periods (1-20 days) for extreme tidal heating to occur. Secular resonance and secular orbital perturbations may support moderate tidal heating at a low equilibrium eccentricity. At orbital periods below 10-30 days, with eccentricities from 0.01 to 0.1, tidal heat may greatly exceed radiogenic heat production. It is unlikely to exceed insolation, except when orbiting very low luminosity hosts, and thus will have limited surface temperature expression. Observations of such bodies many not be able to detect tidal surface enhancements given a few percent uncertainty in albedo, except on the nightside of spin synchronous airless objects. Otherwise detection may occur via spectral detection of hotspots or high volcanic gas concentrations including sulfur dioxide and hydrogen sulfide. The most extreme cases may be able to produce magma oceans, or magma slush mantles with up to 40-60% melt fractions. Tides may alter the habitable zones for smaller red dwarf stars, but are generally detrimental. Multiple viscoelastic models, including the Maxwell, Voigt-Kelvin, Standard Anelastic Solid, and Burgers rheologies are explored and applied to objects such as Io and the super-Earth planet GJ 876d. The complex valued Love number for the Burgers rheology is derived and found to be a useful improvement when modeling the low temperature behavior of tidal bodies, particularly during low eccentricity

SearchResultFinder: federated search made easy

NARCIS (Netherlands)

Trieschnigg, Rudolf Berend; Tjin-Kam-Jet, Kien; Hiemstra, Djoerd

Building a federated search engine based on a large number existing web search engines is a challenge: implementing the programming interface (API) for each search engine is an exacting and time-consuming job. In this demonstration we present SearchResultFinder, a browser plugin which speeds up

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

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

The Moon is a Planet Too: Lunar Science and Robotic Exploration

Science.gov (United States)

Cohen, Barbara A.

2009-01-01

This slide presentation reviews some of what is known about the moon, and draws parallels between the moon and any other terrestrial planet. The Moon is a cornerstone for all rocky planets The Moon is a terrestrial body, formed and evolved similarly to Earth, Mars, Mercury, Venus, and large asteroids The Moon is a differentiated body, with a layered internal structure (crust, mantle, and core) The Moon is a cratered body, preserving a record of bombardment history in the inner solar system The Moon is an active body, experiencing moonquakes, releasing primordial heat, conducting electricity, sustaining bombardment, and trapping volatile molecules Lunar robotic missions provide early science return to obtain important science and engineering objectives, rebuild a lunar science community, and keep our eyes on the Moon. These lunar missions, both past and future are reviewed.

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.

Automatic generation of gene finders for eukaryotic species

DEFF Research Database (Denmark)

Terkelsen, Kasper Munch; Krogh, A.

2006-01-01

and quality of reliable gene annotation grows. Results We present a procedure, Agene, that automatically generates a species-specific gene predictor from a set of reliable mRNA sequences and a genome. We apply a Hidden Markov model (HMM) that implements explicit length distribution modelling for all gene......Background The number of sequenced eukaryotic genomes is rapidly increasing. This means that over time it will be hard to keep supplying customised gene finders for each genome. This calls for procedures to automatically generate species-specific gene finders and to re-train them as the quantity...... structure blocks using acyclic discrete phase type distributions. The state structure of the each HMM is generated dynamically from an array of sub-models to include only gene features represented in the training set. Conclusion Acyclic discrete phase type distributions are well suited to model sequence...

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.

Harmonic development of tide-generating potential of terrestrial planets

Science.gov (United States)

Kudryavtsev, Sergey M.

2008-08-01

The aim of this study is to obtain high-accurate harmonic developments of the tide-generating potential (TGP) of Mercury, Venus and Mars. The planets’ TGP values have been first calculated on the base of DE/LE-406 numerical planetary/lunar ephemerides over a long period of time and then processed by a new spectral analysis method. According to this method the development is directly made to Poisson series where both amplitudes and arguments of the series’ terms are high-degree polynomials of time. A new harmonic development of Mars TGP is made over the time period 1900 AD 2100 AD and includes 767 second-order Poisson series’ terms of minimum amplitude equal to 10-7 m2 s-2. Analogous series composing both Mercury and Venus TGP harmonic models are built over the time period 1000 AD 3000 AD and include 1,061 and 693 terms, respectively. A modification of the standard HW95 format for representation of the terrestrial planets’ TGP is proposed. The number of terms in the planets’ TGP models transformed to the modified HW95 format is 650 for Mercury, 422 for Venus, and 480 for Mars. The quality of the new developments of the terrestrial planets’ TGP is better than that of the similar developments obtained earlier.

Very high-density planets: a possible remnant of gas giants.

Science.gov (United States)

Mocquet, A; Grasset, O; Sotin, C

2014-04-28

Data extracted from the Extrasolar Planets Encyclopaedia (see http://exoplanet.eu) show the existence of planets that are more massive than iron cores that would have the same size. After meticulous verification of the data, we conclude that the mass of the smallest of these planets is actually not known. However, the three largest planets, Kepler-52b, Kepler-52c and Kepler-57b, which are between 30 and 100 times the mass of the Earth, have indeed density larger than an iron planet of the same size. This observation triggers this study that investigates under which conditions these planets could represent the naked cores of gas giants that would have lost their atmospheres during their migration towards the star. This study shows that for moderate viscosity values (10(25) Pa s or lower), large values of escape rate and associated unloading stress rate during the atmospheric loss process lead to the explosion of extremely massive planets. However, for moderate escape rate, the bulk viscosity and finite-strain incompressibility of the cores of giant planets can be large enough to retain a very high density during geological time scales. This would make those a new kind of planet, which would help in understanding the interior structure of the gas giants. However, this new family of exoplanets adds some degeneracy for characterizing terrestrial exoplanets.

Biology on the outer planets. [life possibility in atmospheres and moons

Science.gov (United States)

Young, R. S.; Macelroy, R. D.

1976-01-01

A brief review is given of information on the structure and composition of the outer planets and the organic reactions that may be occurring on them. The possibility of life arising or surviving in the atmospheres of these planets is considered, and the problem of contamination during future unmanned missions is assessed. Atmospheric models or available atmospheric data are reviewed for Jupiter, Saturn, Uranus, Neptune, Pluto, the Galilean satellites, and Titan. The presence of biologically interesting gases on Jupiter and Saturn is discussed, requirements for life on Jupiter are summarized, and possible sources of biological energy are examined. Proposals are made for protecting these planets and satellites from biological contamination by spacecraftborne terrestrial organisms.

A New Data Concentrator for the CMS Muon Barrel Track Finder

CERN Document Server

Triossi, Andrea

2014-01-01

The CMS muon trigger will undergo considerable enhancements in preparation for the LHC \\mbox{run-2}. In order to improve rate reduction and efficiency the full muon trigger chain will be completely redesigned: the plan is to move from a redundant scheme, where the three subdetectors (CSC, DT, RPC) have a separate track finder, to three geographical track finders (barrel, endcap and overlap) that combine trigger primitives of each sub-detector. In particular, the muon barrel track finder (MBTF) will host a new algorithm, that aggregating DT and RPC trigger data, will be able to improve the fake rejection and the muon momentum measurement.This report will focus on the adaptive layer of the MBTF called TwinMux. Its primary role will be to merge, arrange and fan-out the slow optical links from the chambers in faster links (10 Gbps). It will realize a full connectivity matrix between the on-detector electronics and the MBTF allowing for different processing schemes. The TwinMux will be implemented in $\\mu$TCA for...

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 new general purpose event horizon finder for 3D numerical spacetimes

International Nuclear Information System (INIS)

Diener, Peter

2003-01-01

I present a new general purpose event horizon finder for full 3D numerical spacetimes. It works by evolving a complete null surface backwards in time. The null surface is described as the zero-level set of a scalar function, which in principle is defined everywhere. This description of the surface allows the surface, trivially, to change topology, making this event horizon finder able to handle numerical spacetimes where two (or more) black holes merge into a single final black hole

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.

Validation of the Applied Biosystems RapidFinder Shiga Toxin-Producing E. coli (STEC) Detection Workflow.

Science.gov (United States)

Cloke, Jonathan; Matheny, Sharon; Swimley, Michelle; Tebbs, Robert; Burrell, Angelia; Flannery, Jonathan; Bastin, Benjamin; Bird, Patrick; Benzinger, M Joseph; Crowley, Erin; Agin, James; Goins, David; Salfinger, Yvonne; Brodsky, Michael; Fernandez, Maria Cristina

2016-11-01

The Applied Biosystems™ RapidFinder™ STEC Detection Workflow (Thermo Fisher Scientific) is a complete protocol for the rapid qualitative detection of Escherichia coli (E. coli) O157:H7 and the "Big 6" non-O157 Shiga-like toxin-producing E. coli (STEC) serotypes (defined as serogroups: O26, O45, O103, O111, O121, and O145). The RapidFinder STEC Detection Workflow makes use of either the automated preparation of PCR-ready DNA using the Applied Biosystems PrepSEQ™ Nucleic Acid Extraction Kit in conjunction with the Applied Biosystems MagMAX™ Express 96-well magnetic particle processor or the Applied Biosystems PrepSEQ Rapid Spin kit for manual preparation of PCR-ready DNA. Two separate assays comprise the RapidFinder STEC Detection Workflow, the Applied Biosystems RapidFinder STEC Screening Assay and the Applied Biosystems RapidFinder STEC Confirmation Assay. The RapidFinder STEC Screening Assay includes primers and probes to detect the presence of stx1 (Shiga toxin 1), stx2 (Shiga toxin 2), eae (intimin), and E. coli O157 gene targets. The RapidFinder STEC Confirmation Assay includes primers and probes for the "Big 6" non-O157 STEC and E. coli O157:H7. The use of these two assays in tandem allows a user to detect accurately the presence of the "Big 6" STECs and E. coli O157:H7. The performance of the RapidFinder STEC Detection Workflow was evaluated in a method comparison study, in inclusivity and exclusivity studies, and in a robustness evaluation. The assays were compared to the U.S. Department of Agriculture (USDA), Food Safety and Inspection Service (FSIS) Microbiology Laboratory Guidebook (MLG) 5.09: Detection, Isolation and Identification of Escherichia coli O157:H7 from Meat Products and Carcass and Environmental Sponges for raw ground beef (73% lean) and USDA/FSIS-MLG 5B.05: Detection, Isolation and Identification of Escherichia coli non-O157:H7 from Meat Products and Carcass and Environmental Sponges for raw beef trim. No statistically significant

Taking the Temperature of a Lava Planet

Science.gov (United States)

Kreidberg, Laura; Lopez, Eric; Cowan, Nick; Lupu, Roxana; Stevenson, Kevin; Louden, Tom; Malavolta, Luca

2018-05-01

Ultra-short period rocky planets (USPs) are an exotic class of planet found around less than 1% of stars. With orbital periods shorter than 24 hours, these worlds are blasted with stellar radiation that is expected to obliterate any traces of a primordial atmosphere and melt the dayside surface into a magma ocean. Observations of USPs have yielded several surprising results, including the measurement of an offset hotspot in the thermal phase curve of 55 Cancri e (which may indicate a thick atmosphere has survived), and a high Bond albedo for Kepler-10b, which suggests the presence of unusually reflective lava on its surface. To further explore the properties of USPs and put these results in context, we propose to observe a thermal phase curve of the newly discovered USP K2- 141b. This planet is a rocky world in a 6.7 hour orbit around a bright, nearby star. When combined with optical phase curve measured by K2, our observations will uniquely determine the planet's Bond albedo, precisely measure the offset of the thermal curve, and determine the temperature of the dayside surface. These results will cement Spitzer's role as a pioneer in the study of terrestrial planets beyond the Solar System, and provide a critical foundation for pursuing the optimal follow-up strategy for K2-141b with JWST.

Report on the FINDER Experiment at the HIgS Facility

International Nuclear Information System (INIS)

Hagmann, C.A.; Johnson, M.S; McNabb, D.P.; Tonchev, A.P.; Angell, C.; Hammond, S.; Howell, C.; Hutcheson, A.; Karwowski, H.; Kelley, J.; Kwan, E.; Rusev, G.; Tornow, W.

2008-01-01

Homeland Security programs are developing systems that use nuclear resonance fluorescence (NRF) to isotopically map a container. One such system being developed at LLNL is FINDER (Fluorescence Imaging in the Nuclear Domain with Extreme Radiation). The proposed FINDER system works by impinging a tunable monoenergetic gamma ray beam onto a container under investigation. The photons pass through the container and a fraction of them scatter off of the interior components through various electromagnetic processes. One of these processes is NRF. At specific resonance energies, incident photons interact directly with the nuclei of special nuclear material (SNM) or other materials in the container. The incident beam is absorbed and scattered into all directions, depleting the spectrum at the resonant energy. The transmitted gamma ray beam accrues a notch a few eV in width after passing through the material of interest. This notched spectrum will impinge on a witness foil placed on the opposite side of the container relative to the gamma ray source. The witness foil will be made of material identical to the one being sought after. If there is a notch in the spectrum then there will be no NRF photons scattered from the witness foil. The corollary is that if there is no notch in the transmitted spectrum then there will be NRF photons scattered from the witness foil. A simple arrangement of gamma-ray detectors focused on the witness foil, are used to measure the NRF photons. If the detectors see NRF scatter then there was no NRF scatter within the container; therefore, no material of the nature being sought after was in that container. Conversely, if there was no NRF scatter from the witness foil, then the NRF scatter took place from within the container; therefore, the material of interest is inside of the container. Recently, initial feasibility tests of FINDER was performed at the HIgS (High-Intensity Gamma Source) located at Duke University (1]. The preliminary results of

Intrinsic luminosities of the Jovian planets

International Nuclear Information System (INIS)

Hubbard, W.B.

1980-01-01

We review available data and theories on the size and nature of interior power sources in the Jovian planets. Broad band infrared measurements indicate that Jupiter and Saturn have interior heat fluxes about 150 and 50 times larger, respectively, than the terrestrial value. While Neptune has a modest heat flux (approx.5 times terrestrial), it is clearly detected by earth-based measurements. Only Uranus seems to lack a detectable interior heat flow. Various models, ranging from simple cooling to gravitational layering to radioactivity, are discussed. Current evidence seems to favor a cooling model in which the escape of heat is regulated by the atmosphere. This model seems capable of explaining phenomena such as the uniformity of effective temperature over Jupiter's surface and the different emission rates of Uranus and Neptune. In such a model the heat radiated from the atmosphere may derived from depletion of a thermal reservoir in the interior, or it may derive from separation of chemical elements during formation of a core. Calculations indicate that in the earlier stages of cooling, Jupiter and Saturn may have more homogeneous abundances of hydrogen and helium and radiate energy derived from simple cooling. At a subsequent phase (which may be later than the present time), hydrogen and helium will separate and supply grativational energy. Either model is consistent with a hot, high-luminosity origin for the Jovian Planets

MESSENGER, MErcury: Surface, Space ENvironment, GEochemistry, and Ranging; A Mission to Orbit and Explore the Planet Mercury

Science.gov (United States)

1999-01-01

MESSENGER is a scientific mission to Mercury. Understanding this extraordinary planet and the forces that have shaped it is fundamental to understanding the processes that have governed the formation, evolution, and dynamics of the terrestrial planets. MESSENGER is a MErcury Surface, Space ENvironment, GEochemistry and Ranging mission to orbit Mercury for one Earth year after completing two flybys of that planet following two flybys of Venus. The necessary flybys return significant new data early in the mission, while the orbital phase, guided by the flyby data, enables a focused scientific investigation of this least-studied terrestrial planet. Answers to key questions about Mercury's high density, crustal composition and structure, volcanic history, core structure, magnetic field generation, polar deposits, exosphere, overall volatile inventory, and magnetosphere are provided by an optimized set of miniaturized space instruments. Our goal is to gain new insight into the formation and evolution of the solar system, including Earth. By traveling to the inner edge of the solar system and exploring a poorly known world, MESSENGER fulfills this quest.

The CMS Level-1 Trigger Barrel Track Finder

International Nuclear Information System (INIS)

Ero, J.; Wulz, C.; Evangelou, I.; Flouris, G.; Foudas, C.; Loukas, N.; Manthos, N.; Papadopoulos, I.; Paradas, E.; Guiducci, L.; Sotiropoulos, S.; Sphicas, P.; Triossi, A.

2016-01-01

The design and performance of the upgraded CMS Level-1 Trigger Barrel Muon Track Finder (BMTF) is presented. Monte Carlo simulation data as well as cosmic ray data from a CMS muon detector slice test have been used to study in detail the performance of the new track finder. The design architecture is based on twelve MP7 cards each of which uses a Xilinx Virtex-7 FPGA and can receive and transmit data at 10 Gbps from 72 input and 72 output fibers. According to the CMS Trigger Upgrade TDR the BMTF receives trigger primitive data which are computed using both RPC and DT data and transmits data from a number of muon candidates to the upgraded Global Muon Trigger. Results from detailed studies of comparisons between the BMTF algorithm results and the results of a C++ emulator are also presented. The new BMTF will be commissioned for data taking in 2016

Definition of Physical Height Systems for Telluric Planets and Moons

Science.gov (United States)

Tenzer, Robert; Foroughi, Ismael; Sjöberg, Lars E.; Bagherbandi, Mohammad; Hirt, Christian; Pitoňák, Martin

2018-01-01

In planetary sciences, the geodetic (geometric) heights defined with respect to the reference surface (the sphere or the ellipsoid) or with respect to the center of the planet/moon are typically used for mapping topographic surface, compilation of global topographic models, detailed mapping of potential landing sites, and other space science and engineering purposes. Nevertheless, certain applications, such as studies of gravity-driven mass movements, require the physical heights to be defined with respect to the equipotential surface. Taking the analogy with terrestrial height systems, the realization of height systems for telluric planets and moons could be done by means of defining the orthometric and geoidal heights. In this case, however, the definition of the orthometric heights in principle differs. Whereas the terrestrial geoid is described as an equipotential surface that best approximates the mean sea level, such a definition for planets/moons is irrelevant in the absence of (liquid) global oceans. A more natural choice for planets and moons is to adopt the geoidal equipotential surface that closely approximates the geometric reference surface (the sphere or the ellipsoid). In this study, we address these aspects by proposing a more accurate approach for defining the orthometric heights for telluric planets and moons from available topographic and gravity models, while adopting the average crustal density in the absence of reliable crustal density models. In particular, we discuss a proper treatment of topographic masses in the context of gravimetric geoid determination. In numerical studies, we investigate differences between the geodetic and orthometric heights, represented by the geoidal heights, on Mercury, Venus, Mars, and Moon. Our results reveal that these differences are significant. The geoidal heights on Mercury vary from - 132 to 166 m. On Venus, the geoidal heights are between - 51 and 137 m with maxima on this planet at Atla Regio and Beta

Characterizing the X-ray Radiation Field in the Earth-like Planet Forming ExoSystem HD 113766

Science.gov (United States)

Lisse, Carey

2010-09-01

We propose a 100 ksec ACIS-S observation of the 12 Myr old system HD 113766, the site of on-going terrestrial planet formation (Lisse et al. 2008), in order to determine the spectrum of x-ray radiation in the fledgling system, its origin in the stellar coronae and proto-planetary disk, and its potential impact on the nascent planet.

DecoyFinder: an easy-to-use python GUI application for building target-specific decoy sets.

Science.gov (United States)

Cereto-Massagué, Adrià; Guasch, Laura; Valls, Cristina; Mulero, Miquel; Pujadas, Gerard; Garcia-Vallvé, Santiago

2012-06-15

Decoys are molecules that are presumed to be inactive against a target (i.e. will not likely bind to the target) and are used to validate the performance of molecular docking or a virtual screening workflow. The Directory of Useful Decoys database (http://dud.docking.org/) provides a free directory of decoys for use in virtual screening, though it only contains a limited set of decoys for 40 targets.To overcome this limitation, we have developed an application called DecoyFinder that selects, for a given collection of active ligands of a target, a set of decoys from a database of compounds. Decoys are selected if they are similar to active ligands according to five physical descriptors (molecular weight, number of rotational bonds, total hydrogen bond donors, total hydrogen bond acceptors and the octanol-water partition coefficient) without being chemically similar to any of the active ligands used as an input (according to the Tanimoto coefficient between MACCS fingerprints). To the best of our knowledge, DecoyFinder is the first application designed to build target-specific decoy sets. A complete description of the software is included on the application home page. A validation of DecoyFinder on 10 DUD targets is provided as Supplementary Table S1. DecoyFinder is freely available at http://URVnutrigenomica-CTNS.github.com/DecoyFinder.

Clouds in the atmospheres of extrasolar planets. V. The impact of CO2 ice clouds on the outer boundary of the habitable zone

OpenAIRE

Kitzmann, Daniel

2017-01-01

Clouds have a strong impact on the climate of planetary atmospheres. The potential scattering greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars. Here, the impact of CO2 ice clouds on the surface temperatures of terrestrial planets with CO2 dominated atmospheres, orbiting different types of...

Modeling and Implementation of Multi-Position Non-Continuous Rotation Gyroscope North Finder

Directory of Open Access Journals (Sweden)

Jun Luo

2016-09-01

Full Text Available Even when the Global Positioning System (GPS signal is blocked, a rate gyroscope (gyro north finder is capable of providing the required azimuth reference information to a certain extent. In order to measure the azimuth between the observer and the north direction very accurately, we propose a multi-position non-continuous rotation gyro north finding scheme. Our new generalized mathematical model analyzes the elements that affect the azimuth measurement precision and can thus provide high precision azimuth reference information. Based on the gyro’s principle of detecting a projection of the earth rotation rate on its sensitive axis and the proposed north finding scheme, we are able to deduct an accurate mathematical model of the gyro outputs against azimuth with the gyro and shaft misalignments. Combining the gyro outputs model and the theory of propagation of uncertainty, some approaches to optimize north finding are provided, including reducing the gyro bias error, constraining the gyro random error, increasing the number of rotation points, improving rotation angle measurement precision, decreasing the gyro and the shaft misalignment angles. According them, a north finder setup is built and the azimuth uncertainty of 18” is obtained. This paper provides systematic theory for analyzing the details of the gyro north finder scheme from simulation to implementation. The proposed theory can guide both applied researchers in academia and advanced practitioners in industry for designing high precision robust north finder based on different types of rate gyroscopes.

The Voronoi Tessellation cluster finder in 2+1 dimensions

Energy Technology Data Exchange (ETDEWEB)

Soares-Santos, Marcelle; /Fermilab /Sao Paulo U.; de Carvalho, Reinaldo R.; /Sao Jose, INPE; Annis, James; /Fermilab; Gal, Roy R.; /Hawaii U.; La Barbera, Francesco; /Capodimonte Observ.; Lopes, Paulo A.A.; /Valongo Observ.; Wechsler, Risa H.; Busha, Michael T.; Gerke, Brian F.; /SLAC /KIPAC, Menlo Park

2010-11-01

We present a detailed description of the Voronoi Tessellation (VT) cluster finder algorithm in 2+1 dimensions, which improves on past implementations of this technique. The need for cluster finder algorithms able to produce reliable cluster catalogs up to redshift 1 or beyond and down to 10{sup 13.5} solar masses is paramount especially in light of upcoming surveys aiming at cosmological constraints from galaxy cluster number counts. We build the VT in photometric redshift shells and use the two-point correlation function of the galaxies in the field to both determine the density threshold for detection of cluster candidates and to establish their significance. This allows us to detect clusters in a self-consistent way without any assumptions about their astrophysical properties. We apply the VT to mock catalogs which extend to redshift 1.4 reproducing the {Lambda}CDM cosmology and the clustering properties observed in the Sloan Digital Sky Survey data. An objective estimate of the cluster selection function in terms of the completeness and purity as a function of mass and redshift is as important as having a reliable cluster finder. We measure these quantities by matching the VT cluster catalog with the mock truth table. We show that the VT can produce a cluster catalog with completeness and purity >80% for the redshift range up to {approx}1 and mass range down to {approx}10{sup 13.5} solar masses.

The Voronoi Tessellation Cluster Finder in 2 1 Dimensions

Energy Technology Data Exchange (ETDEWEB)

Soares-Santos, Marcelle; /Fermilab /Sao Paulo U.; de Carvalho, Reinaldo R.; /Sao Jose, INPE; Annis, James; /Fermilab; Gal, Roy R.; /Hawaii U.; La Barbera, Francesco; /Capodimonte Observ.; Lopes, Paulo A.A.; /Valongo Observ.; Wechsler, Risa H.; Busha, Michael T.; Gerke, Brian F.; /SLAC /KIPAC, Menlo Park

2011-06-23

We present a detailed description of the Voronoi Tessellation (VT) cluster finder algorithm in 2+1 dimensions, which improves on past implementations of this technique. The need for cluster finder algorithms able to produce reliable cluster catalogs up to redshift 1 or beyond and down to 10{sup 13.5} solar masses is paramount especially in light of upcoming surveys aiming at cosmological constraints from galaxy cluster number counts. We build the VT in photometric redshift shells and use the two-point correlation function of the galaxies in the field to both determine the density threshold for detection of cluster candidates and to establish their significance. This allows us to detect clusters in a self-consistent way without any assumptions about their astrophysical properties. We apply the VT to mock catalogs which extend to redshift 1.4 reproducing the ?CDM cosmology and the clustering properties observed in the Sloan Digital Sky Survey data. An objective estimate of the cluster selection function in terms of the completeness and purity as a function of mass and redshift is as important as having a reliable cluster finder. We measure these quantities by matching the VT cluster catalog with the mock truth table. We show that the VT can produce a cluster catalog with completeness and purity >80% for the redshift range up to {approx}1 and mass range down to {approx}10{sup 13.5} solar masses.

THE VORONOI TESSELLATION CLUSTER FINDER IN 2+1 DIMENSIONS

International Nuclear Information System (INIS)

Soares-Santos, Marcelle; Annis, James; De Carvalho, Reinaldo R.; Gal, Roy R.; La Barbera, Francesco; Lopes, Paulo A. A.; Wechsler, Risa H.; Busha, Michael T.; Gerke, Brian F.

2011-01-01

We present a detailed description of the Voronoi Tessellation (VT) cluster finder algorithm in 2+1 dimensions, which improves on past implementations of this technique. The need for cluster finder algorithms able to produce reliable cluster catalogs up to redshift 1 or beyond and down to 10 13.5 solar masses is paramount especially in light of upcoming surveys aiming at cosmological constraints from galaxy cluster number counts. We build the VT in photometric redshift shells and use the two-point correlation function of the galaxies in the field to both determine the density threshold for detection of cluster candidates and to establish their significance. This allows us to detect clusters in a self-consistent way without any assumptions about their astrophysical properties. We apply the VT to mock catalogs which extend to redshift 1.4 reproducing the ΛCDM cosmology and the clustering properties observed in the Sloan Digital Sky Survey data. An objective estimate of the cluster selection function in terms of the completeness and purity as a function of mass and redshift is as important as having a reliable cluster finder. We measure these quantities by matching the VT cluster catalog with the mock truth table. We show that the VT can produce a cluster catalog with completeness and purity >80% for the redshift range up to ∼1 and mass range down to ∼10 13.5 solar masses.

The hardware track finder processor in CMS at CERN

International Nuclear Information System (INIS)

Kluge, A.

1997-07-01

The work covers the design of the Track Finder Processor in the high energy experiment CMS at CERN/Geneva. The task of this processor is to identify muons and to measure their transverse momentum. The Track Finder makes it possible to determine the physical relevance of each high energetic collision and to forward only interesting data to the data analysis units. Data of more than two hundred thousand detector cells are used to determine the location of muons and to measure their transverse momentum. Each 25 ns a new data set is generated. Measurement of location and transverse momentum of the muons can be terminated within 350 ns by using an ASIC. The classical method in high energy physics experiments is to employ a pattern comparison method. The predefined patterns are compared to the found patterns. The high number of data channels and the complex requirements to the spatial detector resolution do not permit to employ a pattern comparison method. A so called track following algorithm was designed, which is able to assemble complete tracks through the whole detector starting from single track segments. Instead of storing a high number of track patterns the problem is brought back to the algorithm level. Comprehensive simulations, employing the hardware simulation language VHDL, were conducted in order to optimize the algorithm and its hardware implementation. A FPGA (field program able gate array)-prototype was designed. A feasibility study to implement the track finder processor employing ASICs was conducted. (author)

Development and implementation of a 'Mental Health Finder' software tool within an electronic medical record system.

Science.gov (United States)

Swan, D; Hannigan, A; Higgins, S; McDonnell, R; Meagher, D; Cullen, W

2017-02-01

In Ireland, as in many other healthcare systems, mental health service provision is being reconfigured with a move toward more care in the community, and particularly primary care. Recording and surveillance systems for mental health information and activities in primary care are needed for service planning and quality improvement. We describe the development and initial implementation of a software tool ('mental health finder') within a widely used primary care electronic medical record system (EMR) in Ireland to enable large-scale data collection on the epidemiology and management of mental health and substance use problems among patients attending general practice. In collaboration with the Irish Primary Care Research Network (IPCRN), we developed the 'Mental Health Finder' as a software plug-in to a commonly used primary care EMR system to facilitate data collection on mental health diagnoses and pharmacological treatments among patients. The finder searches for and identifies patients based on diagnostic coding and/or prescribed medicines. It was initially implemented among a convenience sample of six GP practices. Prevalence of mental health and substance use problems across the six practices, as identified by the finder, was 9.4% (range 6.9-12.7%). 61.9% of identified patients were female; 25.8% were private patients. One-third (33.4%) of identified patients were prescribed more than one class of psychotropic medication. Of the patients identified by the finder, 89.9% were identifiable via prescribing data, 23.7% via diagnostic coding. The finder is a feasible and promising methodology for large-scale data collection on mental health problems in primary care.

THE PECULIAR SOLAR COMPOSITION AND ITS POSSIBLE RELATION TO PLANET FORMATION

International Nuclear Information System (INIS)

Melendez, J.; Asplund, M.; Gustafsson, B.; Yong, D.

2009-01-01

We have conducted a differential elemental abundance analysis of unprecedented accuracy (∼0.01 dex) of the Sun relative to 11 solar twins from the Hipparcos catalog and 10 solar analogs from planet searches. We find that the Sun shows a characteristic signature with a ∼20% depletion of refractory elements relative to the volatile elements in comparison with the solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. This peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs found not to have such giant planets in radial velocity monitoring show the solar abundance pattern. We discuss various explanations for this peculiarity, including the possibility that the differences in abundance patterns are related to the formation of planetary systems like our own, in particular to the existence of terrestrial planets.

Automated finder for the critical condition on the linear stability of fluid motions

International Nuclear Information System (INIS)

Fujimura, Kaoru

1990-03-01

An automated finder routine for the critical condition on the linear stability of fluid motions is proposed. The Newton-Raphson method was utilized for an iteration to solve nonlinear eigenvalue problems appeared in the analysis. The routine was applied to linear stability problem of a free convection between vertical parallel plates with different non-uniform temperatures as well as a plane Poiseuille flow. An efficiency of the finder routine is demonstrated for several parameter sets, numerically. (author)

GLS-Finder: A Platform for Fast Profiling of Glucosinolates in Brassica Vegetables.

Science.gov (United States)

Sun, Jianghao; Zhang, Mengliang; Chen, Pei

2016-06-01

Mass spectrometry combined with related tandem techniques has become the most popular method for plant secondary metabolite characterization. We introduce a new strategy based on in-database searching, mass fragmentation behavior study, formula predicting for fast profiling of glucosinolates, a class of important compounds in brassica vegetables. A MATLAB script-based expert system computer program, "GLS-Finder", was developed. It is capable of qualitative and semi-quantitative analyses of glucosinolates in samples using data generated by ultrahigh-performance liquid chromatography-high-resolution accurate mass with multi-stage mass fragmentation (UHPLC-HRAM/MS(n)). A suite of bioinformatic tools was integrated into the "GLS-Finder" to perform raw data deconvolution, peak alignment, glucosinolate putative assignments, semi-quantitation, and unsupervised principal component analysis (PCA). GLS-Finder was successfully applied to identify intact glucosinolates in 49 commonly consumed Brassica vegetable samples in the United States. It is believed that this work introduces a new way of fast data processing and interpretation for qualitative and quantitative analyses of glucosinolates, where great efficacy was improved in comparison to identification manually.

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.

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.

The STAR cluster-finder ASIC

Energy Technology Data Exchange (ETDEWEB)

Botlo, M.; LeVine, M.J.; Scheetz, R.A.; Schulz, M.W. [Brookhaven National Lab., Upton, NY (United States); Short, P.; Woods, J. [InnovASIC, Inc., Albuquerque, NM (United States); Crosetto, D. [Rice Univ., Houston, TX (United States). Bonner Nuclear Lab.

1997-12-01

STAR is a large TPC-based experiment at RHIC, the relativistic heavy ion collider at Brookhaven National Laboratory. The STAR experiment reads out a TPC and an SVT (silicon vertex tracker), both of which require in-line pedestal subtraction, compression of ADC values from 10-bit to 8-bit, and location of time sequences representing responses to charged-particle tracks. The STAR cluster finder ASIC responds to all of these needs. Pedestal subtraction and compression are performed using lookup tables in attached RAM. The authors describe its design and implementation, as well as testing methodology and results of tests performed on foundry prototypes.

A reappraisal of the habitability of planets around M dwarf stars.

Science.gov (United States)

Tarter, Jill C; Backus, Peter R; Mancinelli, Rocco L; Aurnou, Jonathan M; Backman, Dana E; Basri, Gibor S; Boss, Alan P; Clarke, Andrew; Deming, Drake; Doyle, Laurance R; Feigelson, Eric D; Freund, Friedmann; Grinspoon, David H; Haberle, Robert M; Hauck, Steven A; Heath, Martin J; Henry, Todd J; Hollingsworth, Jeffery L; Joshi, Manoj M; Kilston, Steven; Liu, Michael C; Meikle, Eric; Reid, I Neill; Rothschild, Lynn J; Scalo, John; Segura, Antigona; Tang, Carol M; Tiedje, James M; Turnbull, Margaret C; Walkowicz, Lucianne M; Weber, Arthur L; Young, Richard E

2007-02-01

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute.

The PIAA Coronagraph Prototype: First Laboratory Results.

Science.gov (United States)

Pluzhnik, Eugene; Guyon, O.; Colley, S.; Gallet, B.; Ridgway, S.; Woodruff, R.; Tanaka, S.; Warren, M.

2006-12-01

The phase-induced amplitude apodization (PIAA) coronagraph combines the main advantages of classical pupil apodization with high throughput ( 100%), high angular resolution ( 2λ/D) and low chromaticity. These advantages can allow direct imaging of nearby extrasolar planets with a 4-meter telescope. The PIAA coronagraph laboratory prototype has been successfully manufactured and starts to operate at the Subary Telescope facility. We present here our first laboratory results with this prototype where we have achieved 2x10-6 contrast within 2 λ/D. We also discuss the main constrains limiting the contrast and describe our future efforts. This work was carried out under JPL contract numbers 1254445 and 1257767 for Development of Technologies for the Terrestrial Planet Finder Mission, with the support and hospitality of the National Astronomical Observatory of Japan.

Extrasolar binary planets. I. Formation by tidal capture during planet-planet scattering

International Nuclear Information System (INIS)

Ochiai, H.; Nagasawa, M.; Ida, S.

2014-01-01

We have investigated (1) the formation of gravitationally bounded pairs of gas-giant planets (which we call 'binary planets') from capturing each other through planet-planet dynamical tide during their close encounters and (2) the subsequent long-term orbital evolution due to planet-planet and planet-star quasi-static tides. For the initial evolution in phase 1, we carried out N-body simulations of the systems consisting of three Jupiter-mass planets taking into account the dynamical tide. The formation rate of the binary planets is as much as 10% of the systems that undergo orbital crossing, and this fraction is almost independent of the initial stellarcentric semimajor axes of the planets, while ejection and merging rates sensitively depend on the semimajor axes. As a result of circularization by the planet-planet dynamical tide, typical binary separations are a few times the sum of the physical radii of the planets. After the orbital circularization, the evolution of the binary system is governed by long-term quasi-static tide. We analytically calculated the quasi-static tidal evolution in phase 2. The binary planets first enter the spin-orbit synchronous state by the planet-planet tide. The planet-star tide removes angular momentum of the binary motion, eventually resulting in a collision between the planets. However, we found that the binary planets survive the tidal decay for the main-sequence lifetime of solar-type stars (∼10 Gyr), if the binary planets are beyond ∼0.3 AU from the central stars. These results suggest that the binary planets can be detected by transit observations at ≳ 0.3 AU.

MacSyFinder: a program to mine genomes for molecular systems with an application to CRISPR-Cas systems.

Directory of Open Access Journals (Sweden)

Sophie S Abby

Full Text Available Biologists often wish to use their knowledge on a few experimental models of a given molecular system to identify homologs in genomic data. We developed a generic tool for this purpose.Macromolecular System Finder (MacSyFinder provides a flexible framework to model the properties of molecular systems (cellular machinery or pathway including their components, evolutionary associations with other systems and genetic architecture. Modelled features also include functional analogs, and the multiple uses of a same component by different systems. Models are used to search for molecular systems in complete genomes or in unstructured data like metagenomes. The components of the systems are searched by sequence similarity using Hidden Markov model (HMM protein profiles. The assignment of hits to a given system is decided based on compliance with the content and organization of the system model. A graphical interface, MacSyView, facilitates the analysis of the results by showing overviews of component content and genomic context. To exemplify the use of MacSyFinder we built models to detect and class CRISPR-Cas systems following a previously established classification. We show that MacSyFinder allows to easily define an accurate "Cas-finder" using publicly available protein profiles.MacSyFinder is a standalone application implemented in Python. It requires Python 2.7, Hmmer and makeblastdb (version 2.2.28 or higher. It is freely available with its source code under a GPLv3 license at https://github.com/gem-pasteur/macsyfinder. It is compatible with all platforms supporting Python and Hmmer/makeblastdb. The "Cas-finder" (models and HMM profiles is distributed as a compressed tarball archive as Supporting Information.

A simplified Track Assembler I/O for the Muon Trigger Track Finder

CERN Document Server

Dallavalle, Gaetano-Marco; Genchev, Vladimir; Grandi, Claudio; Neumeister, Norbert; Porth, Paul; Rohringer, Herbert

1998-01-01

One of the architectural concerns in the present design of the Muon Trigger Track Finder ( MTTF) is the large number of inputs to the Track Assembler ( TA). In the TA block, input track segment pairs from many Extrapolation Units ( EU) are associated into tracks. The relative contribution of these inputs to the assembled tracks is studied with simulated track patterns for low and high pt muons over the entire eta, phi acceptance of the CMS barrel. A pruning of the EUs is proposed which does not alter the performance of the Track Finder and minimizes the interconnections between azimuthal wedges.

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.

The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation

International Nuclear Information System (INIS)

Meng, Huan Y. A.; Rieke, George H.; Su, Kate Y. L.; Gáspár, András

2017-01-01

We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to ∼40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, IC 4665, Chamaeleon I, Orion OB1a and OB1b, Taurus, the β Pictoris Moving Group, ρ Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius–Centaurus, and Tucana–Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P ( D ), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 μ m decays relatively slowly initially and then much more rapidly by ∼10 Myr. However, there is a continuing component until ∼35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12–20 Myr, including ∼13% of the original population, and with a post-peak mean duration of 10–20 Myr.

The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation

Science.gov (United States)

Meng, Huan Y. A.; Rieke, George H.; Su, Kate Y. L.; Gáspár, András

2017-02-01

We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to ˜40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, IC 4665, Chamaeleon I, Orion OB1a and OB1b, Taurus, the β Pictoris Moving Group, ρ Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius-Centaurus, and Tucana-Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P(D), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 μm decays relatively slowly initially and then much more rapidly by ˜10 Myr. However, there is a continuing component until ˜35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12-20 Myr, including ˜13% of the original population, and with a post-peak mean duration of 10-20 Myr.

The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation

Energy Technology Data Exchange (ETDEWEB)

Meng, Huan Y. A.; Rieke, George H.; Su, Kate Y. L.; Gáspár, András, E-mail: hyameng@lpl.arizona.edu [Steward Observatory, Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2017-02-10

We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to ∼40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, IC 4665, Chamaeleon I, Orion OB1a and OB1b, Taurus, the β Pictoris Moving Group, ρ Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius–Centaurus, and Tucana–Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P ( D ), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 μ m decays relatively slowly initially and then much more rapidly by ∼10 Myr. However, there is a continuing component until ∼35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12–20 Myr, including ∼13% of the original population, and with a post-peak mean duration of 10–20 Myr.

Density is not Destiny: Characterizing Terrestrial Exoplanet Geology from Stellar Compositional Abundances

Science.gov (United States)

Unterborn, Cayman T.

2018-01-01

A planet’s mass-radius relationship alone is not a good indicator for its potential to be "Earth-like." While useful in coarse characterizations for distinguishing whether an exoplanet is water/atmosphere- or rock/iron-dominated, there is considerable degeneracy in using the mass-radius relation to determine the mineralogy and structure of a purely terrestrial planet like the Earth. The chemical link between host-stars and rocky planets and the utility of this connection in breaking the degeneracy in the mass-radius relationship is well documented. Given the breadth of observed stellar compositions, modeling the complex effects of these compositional variations on a terrestrial planet’s mineralogy, structure and temperature profile, and the potential pitfalls therein, falls within the purview of the geosciences.I will demonstrate here, the utility in adopting the composition of a terrestrial planet’s host star for contextualizing individual systems (e.g. TRAPPIST-1), as well as for the more general case of quantifying the geophysical consequences of stellar compositional diversity. This includes the potential for a host-star to produce planets able to undergo mantle convection, surface-to-interior degassing and long-term plate tectonics. As we search for truly “Earth-like” planets, we must move away from the simple density-driven definition of “Earth-like” and towards a more holistic view that includes both geochemistry and geophysics. Combining geophysical models and those of planetary formation with host-star abundance data, then, is of paramount importance. This will aid not only in our understanding of the mass-radius relationship but also provide foundational results necessary interpreting future atmospheric observations through the lens of surface-interior interactions (e.g. volcanism) and planetary evolution as a whole.

Efficient cooling of rocky planets by intrusive magmatism

Science.gov (United States)

Lourenço, Diogo L.; Rozel, Antoine B.; Gerya, Taras; Tackley, Paul J.

2018-05-01

The Earth is in a plate tectonics regime with high surface heat flow concentrated at constructive plate boundaries. Other terrestrial bodies that lack plate tectonics are thought to lose their internal heat by conduction through their lids and volcanism: hotter planets (Io and Venus) show widespread volcanism whereas colder ones (modern Mars and Mercury) are less volcanically active. However, studies of terrestrial magmatic processes show that less than 20% of melt volcanically erupts, with most melt intruding into the crust. Signatures of large magmatic intrusions are also found on other planets. Yet, the influence of intrusive magmatism on planetary cooling remains unclear. Here we use numerical magmatic-thermo-mechanical models to simulate global mantle convection in a planetary interior. In our simulations, warm intrusive magmatism acts to thin the lithosphere, leading to sustained recycling of overlying crustal material and cooling of the mantle. In contrast, volcanic eruptions lead to a thick lithosphere that insulates the upper mantle and prevents efficient cooling. We find that heat loss due to intrusive magmatism can be particularly efficient compared to volcanic eruptions if the partitioning of heat-producing radioactive elements into the melt phase is weak. We conclude that the mode of magmatism experienced by rocky bodies determines the thermal and compositional evolution of their interior.

THE ANGLO-AUSTRALIAN PLANET SEARCH. XXI. A GAS-GIANT PLANET IN A ONE YEAR ORBIT AND THE HABITABILITY OF GAS-GIANT SATELLITES

International Nuclear Information System (INIS)

Tinney, C. G.; Wittenmyer, Robert A.; Bailey, Jeremy A.; Horner, J.; Butler, R. Paul; Jones, Hugh R. A.; O'Toole, Simon J.; Carter, Brad D.

2011-01-01

We have detected the Doppler signature of a gas-giant exoplanet orbiting the star HD 38283, in an eccentric orbit with a period of almost exactly one year (P = 363.2 ± 1.6 d, m sin i = 0.34 ± 0.02 M Jup , e = 0.41 ± 0.16). The detection of a planet with period very close to one year critically relied on year-round observation of this circumpolar star. Discovering a planet in a 1 AU orbit around a G dwarf star has prompted us to look more closely at the question of the habitability of the satellites of such planets. Regular satellites orbit all the giant planets in our solar system, suggesting that their formation is a natural by-product of the planet formation process. There is no reason for exomoon formation not to be similarly likely in exoplanetary systems. Moreover, our current understanding of that formation process does not preclude satellite formation in systems where gas giants undergo migration from their formation locations into the terrestrial planet habitable zone. Indeed, regular satellite formation and Type II migration are both linked to the clearing of a gap in the protoplanetary disk by a planet, and so may be inextricably linked. Migration would also multiply the chances of capturing both irregular satellites and Trojan companions sufficiently massive to be habitable. The habitability of such exomoons and exo-Trojans will critically depend on their mass, whether or not they host a magnetosphere, and (for the exomoon case) their orbital radius around the host exoplanet.

Gas in the Terrestrial Planet Region of Disks: CO Fundamental Emission from T Tauri Stars

Science.gov (United States)

2003-06-01

planetary systems: protoplanetary disks — stars: variables: other 1. INTRODUCTION As the likely birthplaces of planets, the inner regions of young...both low column density regions, such as disk gaps , and temperature inversion regions in disk atmospheres can produce significant emission. The esti...which planetary systems form. The moti- vation to study inner disks is all the more intense today given the discovery of planets outside the solar system

A STELLAR-MASS-DEPENDENT DROP IN PLANET OCCURRENCE RATES

International Nuclear Information System (INIS)

Mulders, Gijs D.; Pascucci, Ilaria; Apai, Dániel

2015-01-01

The Kepler spacecraft has discovered a large number of planets with up to one-year periods and down to terrestrial sizes. While the majority of the target stars are main-sequence dwarfs of spectral type F, G, and K, Kepler covers stars with effective temperatures as low as 2500 K, which corresponds to M stars. These cooler stars allow characterization of small planets near the habitable zone, yet it is not clear if this population is representative of that around FGK stars. In this paper, we calculate the occurrence of planets around stars of different spectral types as a function of planet radius and distance from the star and show that they are significantly different from each other. We further identify two trends. First, the occurrence of Earth- to Neptune-sized planets (1-4 R ⊕ ) is successively higher toward later spectral types at all orbital periods probed by Kepler; planets around M stars occur twice as frequently as around G stars, and thrice as frequently as around F stars. Second, a drop in planet occurrence is evident at all spectral types inward of a ∼10 day orbital period, with a plateau further out. By assigning to each spectral type a median stellar mass, we show that the distance from the star where this drop occurs is stellar mass dependent, and scales with semi-major axis as the cube root of stellar mass. By comparing different mechanisms of planet formation, trapping, and destruction, we find that this scaling best matches the location of the pre-main-sequence co-rotation radius, indicating efficient trapping of migrating planets or planetary building blocks close to the star. These results demonstrate the stellar-mass dependence of the planet population, both in terms of occurrence rate and of orbital distribution. The prominent stellar-mass dependence of the inner boundary of the planet population shows that the formation or migration of planets is sensitive to the stellar parameters

K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf

DEFF Research Database (Denmark)

Smith, A. M. S.; Cabrera, J.; Csizmadia, Sz

2018-01-01

We report the discovery in K2's Campaign 10 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf. K2-137 b completes an orbit in only 4.3 h, the second shortest orbital period of any known planet, just 4 min longer than that of KOI 1843.03, which also orbits an M-d...

Darwin--a mission to detect and search for life on extrasolar planets.

Science.gov (United States)

Cockell, C S; Léger, A; Fridlund, M; Herbst, T M; Kaltenegger, L; Absil, O; Beichman, C; Benz, W; Blanc, M; Brack, A; Chelli, A; Colangeli, L; Cottin, H; Coudé du Foresto, F; Danchi, W C; Defrère, D; den Herder, J-W; Eiroa, C; Greaves, J; Henning, T; Johnston, K J; Jones, H; Labadie, L; Lammer, H; Launhardt, R; Lawson, P; Lay, O P; LeDuigou, J-M; Liseau, R; Malbet, F; Martin, S R; Mawet, D; Mourard, D; Moutou, C; Mugnier, L M; Ollivier, M; Paresce, F; Quirrenbach, A; Rabbia, Y D; Raven, J A; Rottgering, H J A; Rouan, D; Santos, N C; Selsis, F; Serabyn, E; Shibai, H; Tamura, M; Thiébaut, E; Westall, F; White, G J

2009-01-01

The discovery of extrasolar planets is one of the greatest achievements of modern astronomy. The detection of planets that vary widely in mass demonstrates that extrasolar planets of low mass exist. In this paper, we describe a mission, called Darwin, whose primary goal is the search for, and characterization of, terrestrial extrasolar planets and the search for life. Accomplishing the mission objectives will require collaborative science across disciplines, including astrophysics, planetary sciences, chemistry, and microbiology. Darwin is designed to detect rocky planets similar to Earth and perform spectroscopic analysis at mid-infrared wavelengths (6-20 mum), where an advantageous contrast ratio between star and planet occurs. The baseline mission is projected to last 5 years and consists of approximately 200 individual target stars. Among these, 25-50 planetary systems can be studied spectroscopically, which will include the search for gases such as CO(2), H(2)O, CH(4), and O(3). Many of the key technologies required for the construction of Darwin have already been demonstrated, and the remainder are estimated to be mature in the near future. Darwin is a mission that will ignite intense interest in both the research community and the wider public.

STABILITY OF ADDITIONAL PLANETS IN AND AROUND THE HABITABLE ZONE OF THE HD 47186 PLANETARY SYSTEM

International Nuclear Information System (INIS)

Kopparapu, Ravi Kumar; Raymond, Sean N.; Barnes, Rory

2009-01-01

We study the dynamical stability of an additional, potentially habitable planet in the HD 47186 planetary system. Two planets are currently known in this system: a 'hot Neptune' with a period of 4.08 days and a Saturn-mass planet with a period of 3.7 years. Here we consider the possibility that one or more undetected planets exist between the two known planets and possibly within the habitable zone (HZ) in this system. Given the relatively low masses of the known planets, additional planets could have masses ∼ + , and hence be terrestrial-like and further improving potential habitability. We perform N-body simulations to identify the stable zone between planets b and c and find that much of the inner HZ can harbor a 10 M + planet. With the current radial velocity threshold of ∼1 m s -1 , an additional planet should be detectable if it lies at the inner edge of the habitable zone at 0.8 AU. We also show that the stable zone could contain two additional planets of 10 M + each if their eccentricities are lower than ∼0.3.

The prominent 1.6-year periodicity in solar motion due to the inner planets

Directory of Open Access Journals (Sweden)

I. Charvátová

2007-06-01

Full Text Available The solar motion due to the inner (terrestrial planets (Mercury, Me; Venus, V; Earth, E; Mars, Ma has been calculated (here for the years 1868–2030. The author found these basic properties of this motion: the toroidal volume in which the Sun moves has the inner radius of 101.3 km and the outer radius of 808.2 km. The solar orbit due to the inner (terrestrial planets is "heart-shaped". The orbital points which are the closest to the centre lie at the time distance of 1.6 years (584 days, on the average, and approximately coincide with the moments of the oppositions of V and E. The spectrum of periods shows the dominant period of 1.6 years (V-E and further periods of 2.13 years (E-Ma (25.6 months, QBO, 0.91 years (V-Ma, 0.8 years ((V-E/2 and 6.4 years. All the periods are above the 99% confidence level. A possible connection of this solar motion with the mid-term quasi-periodicities (MTQP, i.e. 1.5–1.7 years in solar and solar-terrestrial indices can be proposed.

PLANET-PLANET SCATTERING IN PLANETESIMAL DISKS

International Nuclear Information System (INIS)

Raymond, Sean N.; Armitage, Philip J.; Gorelick, Noel

2009-01-01

We study the final architecture of planetary systems that evolve under the combined effects of planet-planet and planetesimal scattering. Using N-body simulations we investigate the dynamics of marginally unstable systems of gas and ice giants both in isolation and when the planets form interior to a planetesimal belt. The unstable isolated systems evolve under planet-planet scattering to yield an eccentricity distribution that matches that observed for extrasolar planets. When planetesimals are included the outcome depends upon the total mass of the planets. For M tot ∼> 1 M J the final eccentricity distribution remains broad, whereas for M tot ∼ J a combination of divergent orbital evolution and recircularization of scattered planets results in a preponderance of nearly circular final orbits. We also study the fate of marginally stable multiple planet systems in the presence of planetesimal disks, and find that for high planet masses the majority of such systems evolve into resonance. A significant fraction leads to resonant chains that are planetary analogs of Jupiter's Galilean satellites. We predict that a transition from eccentric to near-circular orbits will be observed once extrasolar planet surveys detect sub-Jovian mass planets at orbital radii of a ≅ 5-10 AU.

Survival of extrasolar giant planet moons in planet-planet scattering

Science.gov (United States)

CIAN HONG, YU; Lunine, Jonathan; Nicholson, Phillip; Raymond, Sean

2015-12-01

Planet-planet scattering is the best candidate mechanism for explaining the eccentricity distribution of exoplanets. Here we study the survival and dynamics of exomoons under strong perturbations during giant planet scattering. During close encounters, planets and moons exchange orbital angular momentum and energy. The most common outcomes are the destruction of moons by ejection from the system, collision with the planets and the star, and scattering of moons onto perturbed but still planet-bound orbits. A small percentage of interesting moons can remain bound to ejected (free-floating) planets or be captured by a different planet. Moons' survival rate is correlated with planet observables such as mass, semi-major axis, eccentricity and inclination, as well as the close encounter distance and the number of close encounters. In addition, moons' survival rate and dynamical outcomes are predetermined by the moons' initial semi-major axes. The survival rate drops quickly as moons' distances increase, but simulations predict a good chance of survival for the Galilean moons. Moons with different dynamical outcomes occupy different regions of orbital parameter space, which may enable the study of moons' past evolution. Potential effects of planet obliquity evolution caused by close encounters on the satellites’ stability and dynamics will be reported, as well as detailed and systematic studies of individual close encounter events.

TESTING THE METAL OF LATE-TYPE KEPLER PLANET HOSTS WITH IRON-CLAD METHODS

Energy Technology Data Exchange (ETDEWEB)

Mann, Andrew W.; Hilton, Eric J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr, Honolulu, HI 96822 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 (United States); Kraus, Adam [Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States)

2013-06-10

It has been shown that F, G, and early K dwarf hosts of Neptune-sized planets are not preferentially metal-rich. However, it is less clear whether the same holds for late K and M dwarf planet hosts. We report metallicities of Kepler targets and candidate transiting planet hosts with effective temperatures below 4500 K. We use new metallicity calibrations to determine [Fe/H] from visible and near-infrared spectra. We find that the metallicity distribution of late K and M dwarfs monitored by Kepler is consistent with that of the solar neighborhood. Further, we show that hosts of Earth- to Neptune-sized planets have metallicities consistent with those lacking detected planets and rule out a previously claimed 0.2 dex offset between the two distributions at 6{sigma} confidence. We also demonstrate that the metallicities of late K and M dwarfs hosting multiple detected planets are consistent with those lacking detected planets. Our results indicate that multiple terrestrial and Neptune-sized planets can form around late K and M dwarfs with metallicities as low as 0.25 solar. The presence of Neptune-sized planets orbiting such low-metallicity M dwarfs suggests that accreting planets collect most or all of the solids from the disk and that the potential cores of giant planets can readily form around M dwarfs. The paucity of giant planets around M dwarfs compared to solar-type stars must be due to relatively rapid disk evaporation or a slower rate of planet accretion, rather than insufficient solids to form a core.

TESTING THE METAL OF LATE-TYPE KEPLER PLANET HOSTS WITH IRON-CLAD METHODS

International Nuclear Information System (INIS)

Mann, Andrew W.; Hilton, Eric J.; Gaidos, Eric; Kraus, Adam

2013-01-01

It has been shown that F, G, and early K dwarf hosts of Neptune-sized planets are not preferentially metal-rich. However, it is less clear whether the same holds for late K and M dwarf planet hosts. We report metallicities of Kepler targets and candidate transiting planet hosts with effective temperatures below 4500 K. We use new metallicity calibrations to determine [Fe/H] from visible and near-infrared spectra. We find that the metallicity distribution of late K and M dwarfs monitored by Kepler is consistent with that of the solar neighborhood. Further, we show that hosts of Earth- to Neptune-sized planets have metallicities consistent with those lacking detected planets and rule out a previously claimed 0.2 dex offset between the two distributions at 6σ confidence. We also demonstrate that the metallicities of late K and M dwarfs hosting multiple detected planets are consistent with those lacking detected planets. Our results indicate that multiple terrestrial and Neptune-sized planets can form around late K and M dwarfs with metallicities as low as 0.25 solar. The presence of Neptune-sized planets orbiting such low-metallicity M dwarfs suggests that accreting planets collect most or all of the solids from the disk and that the potential cores of giant planets can readily form around M dwarfs. The paucity of giant planets around M dwarfs compared to solar-type stars must be due to relatively rapid disk evaporation or a slower rate of planet accretion, rather than insufficient solids to form a core.

PROBABILISTIC MODEL OF LASER RANGE FINDER FOR THREE DIMENSIONAL GRID CELL IN CLOSE RANGE ENVIRONMENT

Directory of Open Access Journals (Sweden)

Hafiz b Iman

2016-04-01

Full Text Available The probabilistic model of a laser scanner presents an important aspect for simultaneous localization and map-building (SLAM. However, the characteristic of the beam of the laser range finder under extreme incident angles approaching 900 has not been thoroughly investigated. This research paper reports the characteristic of the density of the range value coming from a laser range finder under close range circumstances where the laser is imposed with a high incident angle. The laser was placed in a controlled environment consisting of walls at a close range and 1000 iteration of scans was collected. The assumption of normal density of the metrical data collapses when the beam traverses across sharp edges in this environment. The data collected also shows multimodal density at instances where the range has discontinuity. The standard deviation of the laser range finder is reported to average at 10.54 mm, with 0.96 of accuracy. This significance suggests that under extreme incident angles, a laser range finder reading behaves differently compared to normal distribution. The use of this information is crucial for SLAM activity in enclosed environments such as inside piping grid or other cluttered environments.KEYWORDS:   Hokuyo UTM-30LX; kernel density estimation; probabilistic model  

MobilomeFINDER: web-based tools for in silico and experimental discovery of bacterial genomic islands

OpenAIRE

Ou, Hong-Yu; He, Xinyi; Harrison, Ewan M.; Kulasekara, Bridget R.; Thani, Ali Bin; Kadioglu, Aras; Lory, Stephen; Hinton, Jay C. D.; Barer, Michael R.; Deng, Zixin; Rajakumar, Kumar

2007-01-01

MobilomeFINDER (http://mml.sjtu.edu.cn/MobilomeFINDER) is an interactive online tool that facilitates bacterial genomic island or ‘mobile genome’ (mobilome) discovery; it integrates the ArrayOme and tRNAcc software packages. ArrayOme utilizes a microarray-derived comparative genomic hybridization input data set to generate ‘inferred contigs’ produced by merging adjacent genes classified as ‘present’. Collectively these ‘fragments’ represent a hypothetical ‘microarray-visualized genome (MVG)’....

Searching for life with the Terrestrial Planet Finder: Lagrange point options for a formation flying interferometer

Science.gov (United States)

Beichman, C.; Gomez, G.; Lo, M.; Masdemont, J.; Romans, L.

2002-01-01

In this paper, we describe the mission design for TPF assuming a distributed spacecraft concept using formation flight around both a halo orbit around L2 as well as a heliocentric orbit. Although the mission architecture is still under study, the next two years will include study of four design cncepts and a downselect to two concepts around 2005.

The Bulk Elemental Composition of any Terrestrial Planets in the Alpha Centauri System

Science.gov (United States)

Lineweaver, C. H.; Schonberger, B. F. G.; Robles, J. A.

2010-04-01

Based on the devolatilization patterns in the solar system, and on the differences in the chemical compositions of the Sun and Alpha Centauri, we make estimates of the chemical composition of any Earth-like planets in the Alpha Centauri system.

From Disks to Planets: The Making of Planets and Their Early Atmospheres. An Introduction

Science.gov (United States)

Lammer, Helmut; Blanc, Michel

2018-03-01

This paper is an introduction to volume 56 of the Space Science Series of ISSI, "From disks to planets—the making of planets and their proto-atmospheres", a key subject in our quest for the origins and evolutionary paths of planets, and for the causes of their diversity. Indeed, as exoplanet discoveries progressively accumulated and their characterization made spectacular progress, it became evident that the diversity of observed exoplanets can in no way be reduced to the two classes of planets that we are used to identify in the solar system, namely terrestrial planets and gas or ice giants: the exoplanet reality is just much broader. This fact is no doubt the result of the exceptional diversity of the evolutionary paths linking planetary systems as a whole as well as individual exoplanets and their proto-atmospheres to their parent circumstellar disks: this diversity and its causes are exactly what this paper explores. For each of the main phases of the formation and evolution of planetary systems and of individual planets, we summarize what we believe we understand and what are the important open questions needing further in-depth examination, and offer some suggestions on ways towards solutions. We start with the formation mechanisms of circumstellar disks, with their gas and disk components in which chemical composition plays a very important role in planet formation. We summarize how dust accretion within the disk generates planet cores, while gas accretion on these cores can lead to the diversity of their fluid envelopes. The temporal evolution of the parent disk itself, and its final dissipation, put strong constraints on how and how far planetary formation can proceed. The radiation output of the central star also plays an important role in this whole story. This early phase of planet evolution, from disk formation to dissipation, is characterized by a co-evolution of the disk and its daughter planets. During this co-evolution, planets and their

ON THE VALIDITY OF THE 'HILL RADIUS CRITERION' FOR THE EJECTION OF PLANETS FROM STELLAR HABITABLE ZONES

International Nuclear Information System (INIS)

Cuntz, M.; Yeager, K. E.

2009-01-01

We challenge the customary assumption that the entering of an Earth-mass planet into the Hill radius (or multiples of the Hill radius) of a giant planet is a valid criterion for its ejection from the star-planet system. This assumption has widely been used in previous studies, especially those with an astrobiological focus. As intriguing examples, we explore the dynamics of the systems HD 20782 and HD 188015. Each system possesses a giant planet that remains in or crosses into the stellar habitable zone, thus effectively thwarting the possibility of habitable terrestrial planets. In the case of HD 188015, the orbit of the giant planet is almost circular, whereas in the case of HD 20782, it is extremely elliptical. Although it is found that Earth-mass planets are eventually ejected from the habitable zones of these systems, the 'Hill Radius Criterion' is identified as invalid for the prediction of when the ejection is actually occurring.

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.

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.

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

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.

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.

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.

Kepler’s DR25 Most Earth-like Planet Candidates: What To Know Before You Go

Science.gov (United States)

Thompson, Susan E.; Kepler Team

2018-01-01

The Kepler mission’s latest catalog of planet candidates (data release 25 KOI catalog at the NASA exoplanet archive) was released in June of 2017. The catalog contains 4034 candidates including a significant population of terrestrial-size planets in the habitable zone of FGK dwarf stars. I will highlight what we know about these planet candidates in the DR25 catalog and discuss some of the caveats when working with these detections. Specifically, I will discuss how the noise in the Kepler light curves (from both the instrument and the stars) is known to occasionally produce weak, transit-like signals. We use simulations of this noise to measure how often these signals sneak into the catalog. I will also demonstrate ways to select a high-reliability sample using information available in the catalog. Such considerations may prove useful for anyone planning to use these planet candidates for occurrence rate calculations, choosing targets for follow-up, or deciding which planet to visit on his/her next holiday.

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.

Applications of the Integrated High-Performance CMOS Image Sensor to Range Finders — from Optical Triangulation to the Automotive Field

Directory of Open Access Journals (Sweden)

Joe-Air Jiang

2008-03-01

Full Text Available With their significant features, the applications of complementary metal-oxidesemiconductor (CMOS image sensors covers a very extensive range, from industrialautomation to traffic applications such as aiming systems, blind guidance, active/passiverange finders, etc. In this paper CMOS image sensor-based active and passive rangefinders are presented. The measurement scheme of the proposed active/passive rangefinders is based on a simple triangulation method. The designed range finders chieflyconsist of a CMOS image sensor and some light sources such as lasers or LEDs. Theimplementation cost of our range finders is quite low. Image processing software to adjustthe exposure time (ET of the CMOS image sensor to enhance the performance oftriangulation-based range finders was also developed. An extensive series of experimentswere conducted to evaluate the performance of the designed range finders. From theexperimental results, the distance measurement resolutions achieved by the active rangefinder and the passive range finder can be better than 0.6% and 0.25% within themeasurement ranges of 1 to 8 m and 5 to 45 m, respectively. Feasibility tests onapplications of the developed CMOS image sensor-based range finders to the automotivefield were also conducted. The experimental results demonstrated that our range finders arewell-suited for distance measurements in this field.

Possible climates on terrestrial exoplanets.

Science.gov (United States)

Forget, F; Leconte, J

2014-04-28

What kind of environment may exist on terrestrial planets around other stars? In spite of the lack of direct observations, it may not be premature to speculate on exoplanetary climates, for instance, to optimize future telescopic observations or to assess the probability of habitable worlds. To begin with, climate primarily depends on (i) the atmospheric composition and the volatile inventory; (ii) the incident stellar flux; and (iii) the tidal evolution of the planetary spin, which can notably lock a planet with a permanent night side. The atmospheric composition and mass depends on complex processes, which are difficult to model: origins of volatiles, atmospheric escape, geochemistry, photochemistry, etc. We discuss physical constraints, which can help us to speculate on the possible type of atmosphere, depending on the planet size, its final distance for its star and the star type. Assuming that the atmosphere is known, the possible climates can be explored using global climate models analogous to the ones developed to simulate the Earth as well as the other telluric atmospheres in the solar system. Our experience with Mars, Titan and Venus suggests that realistic climate simulators can be developed by combining components, such as a 'dynamical core', a radiative transfer solver, a parametrization of subgrid-scale turbulence and convection, a thermal ground model and a volatile phase change code. On this basis, we can aspire to build reliable climate predictors for exoplanets. However, whatever the accuracy of the models, predicting the actual climate regime on a specific planet will remain challenging because climate systems are affected by strong positive feedbacks. They can drive planets with very similar forcing and volatile inventory to completely different states. For instance, the coupling among temperature, volatile phase changes and radiative properties results in instabilities, such as runaway glaciations and runaway greenhouse effect.

Acquisition Of Three-Dimensional Image Data By A Scanning Laser Range Finder

Science.gov (United States)

Moring, I.; Heikkinen, T.; Myllyla, R.; Kilpela, A. T.

1989-08-01

We describe a 3-D vision system designed and constructed at the Technical Research Centre of Finland in cooperation with the University of Oulu. The system was developed chiefly for geometric measurements of large objects. The system has been operative for about one year, and its performance has been extensively tested. The system consists of three main units: the range finder, the scanner, and the computer. The range finder is based on the direct measurement of the time-of-flight of a laser pulse. The scanner consists of two mirrors driven by moving iron galvanometers; this unit is controlled by servo amplifiers. The computer controls the scanner, transforms the measured coordinates into a Cartesian coordinate system, and serves as a user interface and postprocessing environment.

Characterizing the Variable Dust Permeability of Planet-induced Gaps

Science.gov (United States)

Weber, Philipp; Benítez-Llambay, Pablo; Gressel, Oliver; Krapp, Leonardo; Pessah, Martin E.

2018-02-01

Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can significantly alter the dust dynamics. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle size for retention outside a gap as a function of particle size, as well as various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet’s orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains—potentially limiting the accretion of solids onto forming terrestrial planets.

High-contrast coronagraph performance in the presence of DM actuator defects

Science.gov (United States)

Sidick, Erkin; Shaklan, Stuart; Cady, Eric

2015-09-01

Deformable Mirrors (DMs) are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Occasionally DM actuators or their associated cables or electronics fail, requiring a wavefront control algorithm to compensate for actuators that may be displaced from their neighbors by hundreds of nanometers. We have carried out experiments on our High-Contrast Imaging Testbed (HCIT) to study the impact of failed actuators in partial fulfilment of the Terrestrial Planet Finder Coronagraph optical model validation milestone. We show that the wavefront control algorithm adapts to several broken actuators and maintains dark-hole contrast in broadband light.

High-Contrast Coronagraph Performance in the Presence of DM Actuator Defects

Science.gov (United States)

Sidick, Erkin; Shaklan, Stuart; Cady, Eric

2015-01-01

Deformable Mirrors (DMs) are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Occasionally DM actuators or their associated cables or electronics fail, requiring a wavefront control algorithm to compensate for actuators that may be displaced from their neighbors by hundreds of nanometers. We have carried out experiments on our High-Contrast Imaging Testbed (HCIT) to study the impact of failed actuators in partial fulfillment of the Terrestrial Planet Finder Coronagraph optical model validation milestone. We show that the wavefront control algorithm adapts to several broken actuators and maintains dark-hole contrast in broadband light.

High Ph, Ammonia Toxicity, and the Search for Life on the Jovian Planets

Science.gov (United States)

Deal, P. H.; Souza, K. A.; Mack, H. M.

1975-01-01

The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, urvival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is two to three orders of magnitude longer than for E. coli. Results support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

Optimization high vortex finder of cyclone separator with computational fluids dynamics simulation

Directory of Open Access Journals (Sweden)

Ni Ketut Caturwati

2017-01-01

Full Text Available Cyclone separator is an equipment that separates particles contained in the fluid without using filters. The dust particles in the flue gases can be separated by utilizing centrifugal forces and different densities of particles, so that the exhaust gases to be cleaner before discharged into the environment. In this paper carried out a simulation by Computational of Fluids Dynamics to determine the number of particles that can be separated in several cyclone separator which has a ratio body diameter against vortex finder high varied as : 1:0.5 ; 1:0.75 ; 1:1 ; 1:1.25 and 1:1.5. Fluid inlet are air with antrachite impurity particles that are commonly found in the exhaust gases from tire manufacturers with inlet velocities varied as: 15 m/s and 30 m/s. The results of simulation show the fluids with 15 m/s of inlet velocity is generate particle separation value is higher than the fluids with 30 m/s inlet velocity for ratio of body diameter and height vortex finder a: 1:0.5 and 1:1.5. For both of inlet velocities the best ratio of body diameter and height vortex finder is 1:1.25, where it has the highest values of percentage trapped particles about 86% for 30 m/s input velocity and also for 15 m/s input velocity.

PointFinder: a novel web tool for WGS-based detection of antimicrobial resistance associated with chromosomal point mutations in bacterial pathogens

DEFF Research Database (Denmark)

Zankari, Ea; Allesøe, Rosa Lundbye; Joensen, Katrine Grimstrup

2017-01-01

enterica, Escherichia coli and Campylobacter jejuni. The web-server ResFinder-2.1 was used to identify acquired antimicrobial resistance genes and two methods, the novel PointFinder (using BLAST) and an in-house method (mapping of raw WGS reads), were used to identify chromosomal point mutations. Results...... or when mapping the reads. Conclusions PointFinder proved, with high concordance between phenotypic and predicted antimicrobial susceptibility, to be a user-friendly web tool for detection of chromosomal point mutations associated with antimicrobial resistance....

MobilomeFINDER: web-based tools for in silico and experimental discovery of bacterial genomic islands

Science.gov (United States)

Ou, Hong-Yu; He, Xinyi; Harrison, Ewan M.; Kulasekara, Bridget R.; Thani, Ali Bin; Kadioglu, Aras; Lory, Stephen; Hinton, Jay C. D.; Barer, Michael R.; Rajakumar, Kumar

2007-01-01

MobilomeFINDER (http://mml.sjtu.edu.cn/MobilomeFINDER) is an interactive online tool that facilitates bacterial genomic island or ‘mobile genome’ (mobilome) discovery; it integrates the ArrayOme and tRNAcc software packages. ArrayOme utilizes a microarray-derived comparative genomic hybridization input data set to generate ‘inferred contigs’ produced by merging adjacent genes classified as ‘present’. Collectively these ‘fragments’ represent a hypothetical ‘microarray-visualized genome (MVG)’. ArrayOme permits recognition of discordances between physical genome and MVG sizes, thereby enabling identification of strains rich in microarray-elusive novel genes. Individual tRNAcc tools facilitate automated identification of genomic islands by comparative analysis of the contents and contexts of tRNA sites and other integration hotspots in closely related sequenced genomes. Accessory tools facilitate design of hotspot-flanking primers for in silico and/or wet-science-based interrogation of cognate loci in unsequenced strains and analysis of islands for features suggestive of foreign origins; island-specific and genome-contextual features are tabulated and represented in schematic and graphical forms. To date we have used MobilomeFINDER to analyse several Enterobacteriaceae, Pseudomonas aeruginosa and Streptococcus suis genomes. MobilomeFINDER enables high-throughput island identification and characterization through increased exploitation of emerging sequence data and PCR-based profiling of unsequenced test strains; subsequent targeted yeast recombination-based capture permits full-length sequencing and detailed functional studies of novel genomic islands. PMID:17537813

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.

Target & Propagation Models for the FINDER Radar

Science.gov (United States)

Cable, Vaughn; Lux, James; Haque, Salmon

2013-01-01

Finding persons still alive in piles of rubble following an earthquake, a severe storm, or other disaster is a difficult problem. JPL is currently developing a victim detection radar called FINDER (Finding Individuals in Emergency and Response). The subject of this paper is directed toward development of propagation & target models needed for simulation & testing of such a system. These models are both physical (real rubble piles) and numerical. Early results from the numerical modeling phase show spatial and temporal spreading characteristics when signals are passed through a randomly mixed rubble pile.

Planet Detectability in the Alpha Centauri System

Science.gov (United States)

Zhao, Lily; Fischer, Debra A.; Brewer, John; Giguere, Matt; Rojas-Ayala, Bárbara

2018-01-01

We use more than a decade of radial-velocity measurements for α {Cen} A, B, and Proxima Centauri from the High Accuracy Radial Velocity Planet Searcher, CTIO High Resolution Spectrograph, and the Ultraviolet and Visual Echelle Spectrograph to identify the M\\sin i and orbital periods of planets that could have been detected if they existed. At each point in a mass–period grid, we sample a simulated, Keplerian signal with the precision and cadence of existing data and assess the probability that the signal could have been produced by noise alone. Existing data places detection thresholds in the classically defined habitable zones at about M\\sin i of 53 {M}\\oplus for α {Cen} A, 8.4 {M}\\oplus for α {Cen} B, and 0.47 {M}\\oplus for Proxima Centauri. Additionally, we examine the impact of systematic errors, or “red noise” in the data. A comparison of white- and red-noise simulations highlights quasi-periodic variability in the radial velocities that may be caused by systematic errors, photospheric velocity signals, or planetary signals. For example, the red-noise simulations show a peak above white-noise simulations at the period of Proxima Centauri b. We also carry out a spectroscopic analysis of the chemical composition of the α {Centauri} stars. The stars have super-solar metallicity with ratios of C/O and Mg/Si that are similar to the Sun, suggesting that any small planets in the α {Cen} system may be compositionally similar to our terrestrial planets. Although the small projected separation of α {Cen} A and B currently hampers extreme-precision radial-velocity measurements, the angular separation is now increasing. By 2019, α {Cen} A and B will be ideal targets for renewed Doppler planet surveys.

Multilingual Maps of the Terrestrial Planets and their Moons: the East and Central European Edition

Science.gov (United States)

Hargitai, H.; Berczi, Sz.

added more details. We also look for a new color-code, since the natural terrestrial map colors scheme can not be used here: colors like blue or green can be misinterpreted easily. The colors on a terrestrial topographic map use a color system that reflects general vegetation cover (green) and the hydrologic system (blue). Part of this color system, however, can also be found in nature: in yellowing leaves (green-yellow-brown). On Mars or the Moon we try to find a color system that reflect the general colors of these planets but also allows discretion of the colors that reflect height or/and terrain type. The maps are available via internet for free pdf download at http://planetologia.elte.hu. References: Hargitai H. I., Rükl A., Gabzdyl P., Roša D., Kundera T., Marjanac T., Ozimkowsky W., Peneva E., Bandrova T., Oreshina L. S., Baeva L. Y, Krasnopevtseva B. V, Shingareva K. B. (2001-2006) Maps of Mars, Venus, Mercury, Moon, Phobos and Deimos, Central European Edition. Budapest 2 Shingareva K. B., J. Zimbelman, M. Buchroithner, H. I. Hargitai (2006): The Realization of ICA Commission Projects on Planetary Cartography Cartographica Volume 40, issue 4. 3

Thermal-orbital coupled tidal heating and habitability of Martian-sized extrasolar planets around M stars

International Nuclear Information System (INIS)

Shoji, D.; Kurita, K.

2014-01-01

M-type stars are good targets in the search for habitable extrasolar planets. Due to their low effective temperatures, the habitable zone of M stars is very close to the stars themselves. For planets that are close to their stars, tidal heating plays an important role in thermal and orbital evolutions, especially when the planet's orbit has a relatively large eccentricity. Although tidal heating interacts with the thermal state and the orbit of the planet, such coupled calculations for extrasolar planets around M stars have not been conducted. We perform coupled calculations using simple structural and orbital models and analyze the thermal state and habitability of a terrestrial planet. Considering this planet to be Martian-sized, the tide heats up and partially melts the mantle, maintaining an equilibrium state if the mass of the star is less than 0.2 times the mass of the Sun and the initial eccentricity of the orbit is more than 0.2. The reduction of heat dissipation due to the melted mantle allows the planet to stay in the habitable zone for more than 10 Gyr even though the orbital distance is small. The surface heat flux at the equilibrium state is between that of Mars and Io. The thermal state of the planet mainly depends on the initial value of the eccentricity and the mass of the star.

Thermal-orbital coupled tidal heating and habitability of Martian-sized extrasolar planets around M stars

Energy Technology Data Exchange (ETDEWEB)

Shoji, D.; Kurita, K. [Earthquake Research Institute, University of Tokyo, Tokyo (Japan)

2014-07-01

M-type stars are good targets in the search for habitable extrasolar planets. Due to their low effective temperatures, the habitable zone of M stars is very close to the stars themselves. For planets that are close to their stars, tidal heating plays an important role in thermal and orbital evolutions, especially when the planet's orbit has a relatively large eccentricity. Although tidal heating interacts with the thermal state and the orbit of the planet, such coupled calculations for extrasolar planets around M stars have not been conducted. We perform coupled calculations using simple structural and orbital models and analyze the thermal state and habitability of a terrestrial planet. Considering this planet to be Martian-sized, the tide heats up and partially melts the mantle, maintaining an equilibrium state if the mass of the star is less than 0.2 times the mass of the Sun and the initial eccentricity of the orbit is more than 0.2. The reduction of heat dissipation due to the melted mantle allows the planet to stay in the habitable zone for more than 10 Gyr even though the orbital distance is small. The surface heat flux at the equilibrium state is between that of Mars and Io. The thermal state of the planet mainly depends on the initial value of the eccentricity and the mass of the star.

CRISPRCasFinder, an update of CRISRFinder, includes a portable version, enhanced performance and integrates search for Cas proteins.

Science.gov (United States)

Couvin, David; Bernheim, Aude; Toffano-Nioche, Claire; Touchon, Marie; Michalik, Juraj; Néron, Bertrand; C Rocha, Eduardo P; Vergnaud, Gilles; Gautheret, Daniel; Pourcel, Christine

2018-05-22

CRISPR (clustered regularly interspaced short palindromic repeats) arrays and their associated (Cas) proteins confer bacteria and archaea adaptive immunity against exogenous mobile genetic elements, such as phages or plasmids. CRISPRCasFinder allows the identification of both CRISPR arrays and Cas proteins. The program includes: (i) an improved CRISPR array detection tool facilitating expert validation based on a rating system, (ii) prediction of CRISPR orientation and (iii) a Cas protein detection and typing tool updated to match the latest classification scheme of these systems. CRISPRCasFinder can either be used online or as a standalone tool compatible with Linux operating system. All third-party software packages employed by the program are freely available. CRISPRCasFinder is available at https://crisprcas.i2bc.paris-saclay.fr.

STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS

International Nuclear Information System (INIS)

Yang Jun; Abbot, Dorian S.; Cowan, Nicolas B.

2013-01-01

The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope.

Forecasting the detectability of known radial velocity planets with the upcoming CHEOPS mission

Science.gov (United States)

Yi, Joo Sung; Chen, Jingjing; Kipping, David

2018-04-01

The CHaracterizing ExOPlanets Satellite (CHEOPS) mission is planned for launch next year with a major objective being to search for transits of known radial velocity (RV) planets, particularly those orbiting bright stars. Since the RV method is only sensitive to planetary mass, the radii, transit depths and transit signal-to-noise values of each RV planet are, a priori, unknown. Using an empirically calibrated probabilistic mass-radius relation, forecaster, we address this by predicting a catalogue of homogeneous credible intervals for these three keys terms for 468 planets discovered via RVs. Of these, we find that the vast majority should be detectable with CHEOPS, including terrestrial bodies, if they have the correct geometric alignment. In particular, we predict that 22 mini-Neptunes and 82 Neptune-sized planets would be suitable for detection and that more than 80 per cent of these will have apparent magnitude of V work. Our work aims to assist the CHEOPS team in scheduling efforts and highlights the great value of quantifiable, statistically robust estimates for upcoming exoplanetary missions.

A SEARCH FOR SHORT-PERIOD ROCKY PLANETS AROUND WDs WITH THE COSMIC ORIGINS SPECTROGRAPH (COS)

Energy Technology Data Exchange (ETDEWEB)

Sandhaus, Phoebe H.; Debes, John H.; Ely, Justin; Hines, Dean C.; Bourque, Matthew [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)

2016-05-20

The search for transiting habitable exoplanets has broadened to include several types of stars that are smaller than the Sun in an attempt to increase the observed transit depth and hence the atmospheric signal of the planet. Of all spectral types, white dwarfs (WDs) are the most favorable for this type of investigation. The fraction of WDs that possess close-in rocky planets is unknown, but several large angle stellar surveys have the photometric precision and cadence to discover at least one if they are common. Ultraviolet observations of WDs may allow for detection of molecular oxygen or ozone in the atmosphere of a terrestrial planet. We use archival Hubble Space Telescope data from the Cosmic Origins Spectrograph to search for transiting rocky planets around UV-bright WDs. In the process, we discovered unusual variability in the pulsating WD GD 133, which shows slow sinusoidal variations in the UV. While we detect no planets around our small sample of targets, we do place stringent limits on the possibility of transiting planets, down to sub-lunar radii. We also point out that non-transiting small planets in thermal equilibrium are detectable around hotter WDs through infrared excesses, and identify two candidates.

Studies of volatiles and organic materials in early terrestrial and present-day outer solar system environments

Science.gov (United States)

Sagan, Carl; Thompson, W. Reid; Chyba, Christopher F.; Khare, B. N.

1991-01-01

A review and partial summary of projects within several areas of research generally involving the origin, distribution, chemistry, and spectral/dielectric properties of volatiles and organic materials in the outer solar system and early terrestrial environments are presented. The major topics covered include: (1) impact delivery of volatiles and organic compounds to the early terrestrial planets; (2) optical constants measurements; (3) spectral classification, chemical processes, and distribution of materials; and (4) radar properties of ice, hydrocarbons, and organic heteropolymers.

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

Providing a USSD location based clinic finder in South Africa: did it work?

Science.gov (United States)

Parsons, Annie Neo; Timler, Dagmar

2014-01-01

A new mHealth service, Clinic Finder, was designed to provide a location-based service for any cellphone user in South Africa dialing a dedicated USSD string to find the nearest public primary health care facility. The service was funded by a European Union grant to Cell-Life to support the National Department of Health. Clinic Finder's aims were to provide a reliable and accurate service, and to assess both the most effective means of advertising the service as well as interest in the service. Users dialing the USSD string are asked to agree to geo-location (Vodacom and MTN users) or asked to enter their province, town and street (virtual network users and those choosing not to geo-locate). The service provider, AAT, sends the data to Cell-Life where an SMS with details of the nearest public primary health care facility is sent to the user by Cell-Life's open-source Communicate platform. The service was advertised on 3 days in 2014 using two different means: a newspaper ad on 20 May 2014 and Please Call Me ads on 30 July 2014 and 14 August 2014. 28.2% of unique users on 20 May 2014, 10.5% of unique users on 30 July 2014 and 92.8% of unique users on 14 August 2014 who agreed to geo-location successfully received SMSs. However, only 4.2%, 0.5%, and 2.4% of unique users responding to each advertisement who did not geo-locate then received an SMS. A small survey of users following the 20 May 2014 newspaper ad found overall interest in the idea of Clinic Finder, though unsuccessful users were more likely to dislike the service. The overall experience of using location based services and USSD for Clinic Finder suggests a need in the field of mHealth for wider availability of data on service usability and effectiveness.

The Relationship between Kolb's Learning Styles and StrengthsFinder's Talent Themes

Science.gov (United States)

Caldwell, Adonna B.

2009-01-01

The purpose of this study was to investigate if there were relationships between college students' talent themes as defined by the Clifton StrengthsFinder(TM) Instrument and their learning style as defined by Kolb Learning Styles Inventory. Logistical regression methodology was utilized to assess the relationship between learning styles and talent…

Seeding life on the moons of the outer planets via lithopanspermia.

Science.gov (United States)

Worth, R J; Sigurdsson, Steinn; House, Christopher H

2013-12-01

Material from the surface of a planet can be ejected into space by a large impact and could carry primitive life-forms with it. We performed n-body simulations of such ejecta to determine where in the Solar System rock from Earth and Mars may end up. We found that, in addition to frequent transfer of material among the terrestrial planets, transfer of material from Earth and Mars to the moons of Jupiter and Saturn is also possible, but rare. We expect that such transfers were most likely to occur during the Late Heavy Bombardment or during the ensuing 1-2 billion years. At this time, the icy moons were warmer and likely had little or no ice shell to prevent meteorites from reaching their liquid interiors. We also note significant rates of re-impact in the first million years after ejection. This could re-seed life on a planet after partial or complete sterilization by a large impact, which would aid the survival of early life during the Late Heavy Bombardment.

XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape.

Science.gov (United States)

Kislyakova, Kristina G; Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V; Leitzinger, Martin; Khodachenko, Maxim L; Kulikov, Yuri N; Güdel, Manuel; Hanslmeier, Arnold

2013-11-01

We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates.

XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape

Science.gov (United States)

Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel; Hanslmeier, Arnold

2013-01-01

Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s−1 to ∼5.3×1030 s−1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1030–1048. PMID:24283926

ALMOST ALL OF KEPLER'S MULTIPLE-PLANET CANDIDATES ARE PLANETS

International Nuclear Information System (INIS)

Lissauer, Jack J.; Rowe, Jason F.; Bryson, Stephen T.; Howell, Steve B.; Jenkins, Jon M.; Kinemuchi, Karen; Koch, David G.; Marcy, Geoffrey W.; Adams, Elisabeth; Fressin, Francois; Geary, John; Holman, Matthew J.; Ragozzine, Darin; Buchhave, Lars A.; Ciardi, David R.; Cochran, William D.; Fabrycky, Daniel C.; Ford, Eric B.; Morehead, Robert C.; Gilliland, Ronald L.

2012-01-01

We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.

Significance of large Neptune-crossing objects for terrestrial catastrophism

Science.gov (United States)

Steel, D.

2014-07-01

Over the past few decades a substantial number of objects have been discovered on orbits beyond Neptune (i.e. transneptunian objects, in various sub-classes), crossing Neptune's orbit (here: the Neptune-crossers of interest), and also others crossing the orbits of any or all of the jovian planets (i.e. Centaurs). These range in size from tens of kilometres across to hundreds of kilometres and more. Although formally classified as minor planets/asteroids, plus a few dwarf planets, the physical reality of these objects is that they are giant comets. That is, they seem to be composed largely of ices and if they were to enter the inner solar system then they would demonstrate the commonly-observed behaviour of comets such as outgassing, and the formation of ion and dust tails. Commonly-observed cometary behaviour, however, also includes fragmentation events and sometimes complete disintegration for no apparent cause (such as tidal disruption or thermal stresses). One might therefore wonder what the implications would be for life on Earth and terrestrial catastrophism if and when one of these objects, say 100 to 500 kilometres in size, dropped into a short-period orbit with perihelion distance (q) less than 1 au; or even q ˜ 5 au, given what Jupiter's gravity might do to it. How often might such events occur? One way to address that question would be to conduct numerical integrations of suitable test orbits and identify how often small-q orbits result, but this comes up against the problem of identifying very-infrequent events (with annual probabilities per object perhaps of order 10^{-12}-10^{-10}. For example, Emel'yanenko et al. [1] recently followed test orbits for approximately 5 × 10^{14} particle-years (8,925 objects with 200 clones of each, for 300 Myr) but because these were selected on the basis of initial values of q only below 36 (rather than ˜30) au many were not immediately Neptune-crossers; however, many test particles did eventually migrate into small

Ancient Terrestrial Carbon: Lost and Found

Science.gov (United States)

Freeman, K. H.

2017-12-01

terrestrial archives. Mechanistic-based understanding of climate's role in the extensive loss of carbon within both deep and shallow ancient soil horizons has implications for predicting modern carbon budgets on a rapidly warming planet.

Impact of an asteroid or comet in the ocean and extinction of terrestrial life

Science.gov (United States)

Ahrens, T. J.; Okeefe, J. D.

1982-01-01

Finite difference calculations describing the impact mechanics associated with a 10 to 30 km diameter silicate or water object impacting a 5 km deep ocean overlying a silicate solid planet demonstrate that from 12 to 15% of the bolide energy resides in the water. It is speculated that minimal global tsunami run-up heights on the continents would be 300-400 meters, and that such waves would inundate all low altitude continental areas, and strip and silt-over virtually all vegetation. As a result the terrestrial animal food chain would be seriously perturbed. This could in turn cause extinction of large terrestrial animals.

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

Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

Science.gov (United States)

Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

2017-12-01

Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

BioJava-ModFinder: identification of protein modifications in 3D structures from the Protein Data Bank.

Science.gov (United States)

Gao, Jianjiong; Prlic, Andreas; Bi, Chunxiao; Bluhm, Wolfgang F; Dimitropoulos, Dimitris; Xu, Dong; Bourne, Philip E; Rose, Peter W

2017-07-01

We developed a new software tool, BioJava-ModFinder, for identifying protein modifications observed in 3D structures archived in the Protein Data Bank (PDB). Information on more than 400 types of protein modifications were collected and curated from annotations in PDB, RESID, and PSI-MOD. We divided these modifications into three categories: modified residues, attachment modifications, and cross-links. We have developed a systematic method to identify these modifications in 3D protein structures. We have integrated this package with the RCSB PDB web application and added protein modification annotations to the sequence diagram and structure display. By scanning all 3D structures in the PDB using BioJava-ModFinder, we identified more than 30 000 structures with protein modifications, which can be searched, browsed, and visualized on the RCSB PDB website. BioJava-ModFinder is available as open source (LGPL license) at ( https://github.com/biojava/biojava/tree/master/biojava-modfinder ). The RCSB PDB can be accessed at http://www.rcsb.org . pwrose@ucsd.edu. © The Author 2017. Published by Oxford University Press.

High Resolution N-Body Simulations of Terrestrial Planet Growth

Science.gov (United States)

Clark Wallace, Spencer; Quinn, Thomas R.

2018-04-01

We investigate planetesimal accretion with a direct N-body simulation of an annulus at 1 AU around a 1 M_sun star. The planetesimal ring, which initially contains N = 106 bodies is evolved through the runaway growth stage into the phase of oligarchic growth. We find that the mass distribution of planetesimals develops a bump around 1022 g shortly after the oligarchs form. This feature is absent in previous lower resolution studies. We find that this bump marks a boundary between growth modes. Below the bump mass, planetesimals are packed tightly enough together to populate first order mean motion resonances with the oligarchs. These resonances act to heat the tightly packed, low mass planetesimals, inhibiting their growth. We examine the eccentricity evolution of a dynamically hot planetary embryo embedded in an annulus of planetesimals and find that dynamical friction acts more strongly on the embryo when the planetesimals are finely resolved. This effect disappears when the annulus is made narrow enough to exclude most of the mean motion resonances. Additionally, we find that the 1022 g bump is significantly less prominent when we follow planetesimal growth with a skinny annulus.This feature, which is reminiscent of the power law break seen in the size distribution of asteroid belt objects may be an important clue for constraining the initial size of planetesimals in planet formation models.

Exploring procedures for the rapid assessment of optically stimulated luminescence range-finder ages

International Nuclear Information System (INIS)

Roberts, Helen M.; Durcan, Julie A.; Duller, Geoff A.T.

2009-01-01

Optically stimulated luminescence (OSL) dating of sediments is a lengthy, labour-intensive, and time-consuming procedure. However, in some situations a rough approximation of the OSL age is all that is necessary e.g. for a pilot field campaign, to plan a sampling strategy, or to determine the resolution required for a dating campaign. Thus, it would be useful to establish an approximate OSL age without the lengthy and involved processes normally used. This paper explores how the standard procedures involved in OSL age determinations can be simplified to yield range-finder ages. Three areas are examined, namely, laboratory preparation, D e estimation, and dose-rate determination. The consequences of circumventing some of the preparation and measurement steps of conventional OSL dating are examined for a variety of sediments, by comparing the OSL range-finder ages to those obtained using full quartz OSL preparation and measurement procedures.

SynergyFinder: a web application for analyzing drug combination dose-response matrix data.

Science.gov (United States)

Ianevski, Aleksandr; He, Liye; Aittokallio, Tero; Tang, Jing

2017-08-01

Rational design of drug combinations has become a promising strategy to tackle the drug sensitivity and resistance problem in cancer treatment. To systematically evaluate the pre-clinical significance of pairwise drug combinations, functional screening assays that probe combination effects in a dose-response matrix assay are commonly used. To facilitate the analysis of such drug combination experiments, we implemented a web application that uses key functions of R-package SynergyFinder, and provides not only the flexibility of using multiple synergy scoring models, but also a user-friendly interface for visualizing the drug combination landscapes in an interactive manner. The SynergyFinder web application is freely accessible at https://synergyfinder.fimm.fi ; The R-package and its source-code are freely available at http://bioconductor.org/packages/release/bioc/html/synergyfinder.html . jing.tang@helsinki.fi. © The Author(s) 2017. Published by Oxford University Press.

PPI finder: a mining tool for human protein-protein interactions.

Directory of Open Access Journals (Sweden)

Min He

Full Text Available BACKGROUND: The exponential increase of published biomedical literature prompts the use of text mining tools to manage the information overload automatically. One of the most common applications is to mine protein-protein interactions (PPIs from PubMed abstracts. Currently, most tools in mining PPIs from literature are using co-occurrence-based approaches or rule-based approaches. Hybrid methods (frame-based approaches by combining these two methods may have better performance in predicting PPIs. However, the predicted PPIs from these methods are rarely evaluated by known PPI databases and co-occurred terms in Gene Ontology (GO database. METHODOLOGY/PRINCIPAL FINDINGS: We here developed a web-based tool, PPI Finder, to mine human PPIs from PubMed abstracts based on their co-occurrences and interaction words, followed by evidences in human PPI databases and shared terms in GO database. Only 28% of the co-occurred pairs in PubMed abstracts appeared in any of the commonly used human PPI databases (HPRD, BioGRID and BIND. On the other hand, of the known PPIs in HPRD, 69% showed co-occurrences in the literature, and 65% shared GO terms. CONCLUSIONS: PPI Finder provides a useful tool for biologists to uncover potential novel PPIs. It is freely accessible at http://liweilab.genetics.ac.cn/tm/.

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/.

SciRide Finder: a citation-based paradigm in biomedical literature search.

Science.gov (United States)

Volanakis, Adam; Krawczyk, Konrad

2018-04-18

There are more than 26 million peer-reviewed biomedical research items according to Medline/PubMed. This breadth of information is indicative of the progress in biomedical sciences on one hand, but an overload for scientists performing literature searches on the other. A major portion of scientific literature search is to find statements, numbers and protocols that can be cited to build an evidence-based narrative for a new manuscript. Because science builds on prior knowledge, such information has likely been written out and cited in an older manuscript. Thus, Cited Statements, pieces of text from scientific literature supported by citing other peer-reviewed publications, carry significant amount of condensed information on prior art. Based on this principle, we propose a literature search service, SciRide Finder (finder.sciride.org), which constrains the search corpus to such Cited Statements only. We demonstrate that Cited Statements can carry different information to this found in titles/abstracts and full text, giving access to alternative literature search results than traditional search engines. We further show how presenting search results as a list of Cited Statements allows researchers to easily find information to build an evidence-based narrative for their own manuscripts.

Energy Dissipation in the Upper Atmospheres of TRAPPIST-1 Planets

Science.gov (United States)

Cohen, Ofer; Glocer, Alex; Garraffo, Cecilia; Drake, Jeremy J.; Bell, Jared M.

2018-03-01

We present a method to quantify the upper limit of the energy transmitted from the intense stellar wind to the upper atmospheres of three of the TRAPPIST-1 planets (e, f, and g). We use a formalism that treats the system as two electromagnetic regions, where the efficiency of the energy transmission between one region (the stellar wind at the planetary orbits) to the other (the planetary ionospheres) depends on the relation between the conductances and impedances of the two regions. Since the energy flux of the stellar wind is very high at these planetary orbits, we find that for the case of high transmission efficiency (when the conductances and impedances are close in magnitude), the energy dissipation in the upper planetary atmospheres is also very large. On average, the Ohmic energy can reach 0.5–1 W m‑2, about 1% of the stellar irradiance and 5–15 times the EUV irradiance. Here, using constant values for the ionospheric conductance, we demonstrate that the stellar wind energy could potentially drive large atmospheric heating in terrestrial planets, as well as in hot Jupiters. More detailed calculations are needed to assess the ionospheric conductance and to determine more accurately the amount of heating the stellar wind can drive in close-orbit planets.

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

Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary

Science.gov (United States)

Heller, René

2013-01-01

Abstract White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10−6. Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 104 K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable. Key Words: Extrasolar terrestrial planets—Habitability—Habitable zone—Tides—Exoplanets. Astrobiology 13, 279–291. PMID:23537137

Optimal Strategies for Probing Terrestrial Exoplanet Atmospheres with JWST

Science.gov (United States)

Batalha, Natasha E.; Lewis, Nikole K.; Line, Michael

2018-01-01

It is imperative that the exoplanet community determines the feasibility and the resources needed to yield high fidelity atmospheric compositions from terrestrial exoplanets. In particular, LHS 1140b and the TRAPPIST-1 system, already slated for observations by JWST’s Guaranteed Time Observers, will be the first two terrestrial planets observed by JWST. I will discuss optimal observing strategies for observing these two systems, focusing on the NIRSpec Prism (1-5μm) and the combination of NIRISS SOSS (1-2.7μm) and NIRSpec G395H (3-5μm). I will also introduce currently unsupported JWST readmodes that have the potential to greatly increase the precision on our atmospheric spectra. Lastly, I will use information content theory to compute the expected confidence interval on the retrieved abundances of key molecular species and temperature profiles as a function of JWST observing cycles.

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.

PLANET HUNTERS: ASSESSING THE KEPLER INVENTORY OF SHORT-PERIOD PLANETS

International Nuclear Information System (INIS)

Schwamb, Megan E.; Lintott, Chris J.; Lynn, Stuart; Smith, Arfon M.; Simpson, Robert J.; Fischer, Debra A.; Giguere, Matthew J.; Brewer, John M.; Parrish, Michael; Schawinski, Kevin

2012-01-01

We present the results from a search of data from the first 33.5 days of the Kepler science mission (Quarter 1) for exoplanet transits by the Planet Hunters citizen science project. Planet Hunters enlists members of the general public to visually identify transits in the publicly released Kepler light curves via the World Wide Web. Over 24,000 volunteers reviewed the Kepler Quarter 1 data set. We examine the abundance of ≥2 R ⊕ planets on short-period ( ⊕ Planet Hunters ≥85% efficient at identifying transit signals for planets with periods less than 15 days for the Kepler sample of target stars. Our high efficiency rate for simulated transits along with recovery of the majority of Kepler ≥4 R ⊕ planets suggests that the Kepler inventory of ≥4 R ⊕ short-period planets is nearly complete.

LC-IMS-MS Feature Finder: detecting multidimensional liquid chromatography, ion mobility and mass spectrometry features in complex datasets.

Science.gov (United States)

Crowell, Kevin L; Slysz, Gordon W; Baker, Erin S; LaMarche, Brian L; Monroe, Matthew E; Ibrahim, Yehia M; Payne, Samuel H; Anderson, Gordon A; Smith, Richard D

2013-11-01

The addition of ion mobility spectrometry to liquid chromatography-mass spectrometry experiments requires new, or updated, software tools to facilitate data processing. We introduce a command line software application LC-IMS-MS Feature Finder that searches for molecular ion signatures in multidimensional liquid chromatography-ion mobility spectrometry-mass spectrometry (LC-IMS-MS) data by clustering deisotoped peaks with similar monoisotopic mass, charge state, LC elution time and ion mobility drift time values. The software application includes an algorithm for detecting and quantifying co-eluting chemical species, including species that exist in multiple conformations that may have been separated in the IMS dimension. LC-IMS-MS Feature Finder is available as a command-line tool for download at http://omics.pnl.gov/software/LC-IMS-MS_Feature_Finder.php. The Microsoft.NET Framework 4.0 is required to run the software. All other dependencies are included with the software package. Usage of this software is limited to non-profit research to use (see README). rds@pnnl.gov. Supplementary data are available at Bioinformatics online.

APF-The Lick Observatory Automated Planet Finder

Science.gov (United States)

2014-04-01

WILLIAM DEICH,1 BRIAN DUPRAW,1 WAYNE EARTHMAN,1 HARLAND EPPS,1 SANDRA FABER,1 DEBRA FISCHER ,3 ELINOR GATES,1 DAVID HILYARD,1 BRAD HOLDEN,1 KEN JOHNSTON,4...SANDY KEISER,2 DICK KANTO,1 MYRA KATSUKI,1 LEE LAITERMAN,1 KYLE LANCLOS,1 GREG LAUGHLIN,1 JEFF LEWIS,1 CHRIS LOCKWOOD,1,5 PAUL LYNAM,1 GEOFFREY MARCY,6...with S. Vogt as principal investigator, G. Marcy and D. Fischer as coinvestgators, and M. Radovan as project manager and principal engineer. A large

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

The Direct Detection and Characterization of M-dwarf Planets Using Light Echoes

Science.gov (United States)

Sparks, William B.; White, Richard L.; Lupu, Roxana E.; Ford, Holland C.

2018-02-01

Exoplanets orbiting M-dwarf stars are a prime target in the search for life in the universe. M-dwarf stars are active, with powerful flares that could adversely impact prospects for life, though there are counter-arguments. Here, we turn flaring to advantage and describe ways in which it can be used to enhance the detectability of planets, in the absence of transits or a coronagraph, significantly expanding the accessible discovery and characterization space. Flares produce brief bursts of intense luminosity, after which the star dims. Due to the light travel time between the star and planet, the planet receives the high-intensity pulse, which it re-emits through scattering (a light echo) or intrinsic emission when the star is much fainter, thereby increasing the planet’s detectability. The planet’s light-echo emission can potentially be discriminated from that of the host star by means of a time delay, Doppler shift, spatial shift, and polarization, each of which can improve the contrast of the planet to the star. Scattered light can reveal the albedo spectrum of the planet to within a size scale factor, and is likely to be polarized. Intrinsic emission mechanisms include fluorescent pumping of multiple molecular hydrogen and neutral oxygen lines by intense Lyα and Lyβ flare emission, recombination radiation of ionized and photodissociated species, and atmospheric processes such as terrestrial upper atmosphere airglow and near-infrared hydroxyl emission. We discuss the feasibility of detecting light echoes and find that light echo detection is possible under favorable circumstances.

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.

ALMOST ALL OF KEPLER'S MULTIPLE-PLANET CANDIDATES ARE PLANETS

Energy Technology Data Exchange (ETDEWEB)

Lissauer, Jack J.; Rowe, Jason F.; Bryson, Stephen T.; Howell, Steve B.; Jenkins, Jon M.; Kinemuchi, Karen; Koch, David G. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Marcy, Geoffrey W. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Adams, Elisabeth; Fressin, Francois; Geary, John; Holman, Matthew J.; Ragozzine, Darin [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Buchhave, Lars A. [Niels Bohr Institute, University of Copenhagen, DK-2100, Copenhagen (Denmark); Ciardi, David R. [Exoplanet Science Institute/Caltech, Pasadena, CA 91125 (United States); Cochran, William D. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Ford, Eric B.; Morehead, Robert C. [University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Gilliland, Ronald L., E-mail: Jack.Lissauer@nasa.gov [Space Telescope Science Institute, Baltimore, MD 21218 (United States); and others

2012-05-10

We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.

Observsational Planet Formation

Science.gov (United States)

Dong, Ruobing; Zhu, Zhaohuan; Fung, Jeffrey

2017-06-01

Planets form in gaseous protoplanetary disks surrounding newborn stars. As such, the most direct way to learn how they form from observations, is to directly watch them forming in disks. In the past, this was very difficult due to a lack of observational capabilities; as such, planet formation was largely a subject of pure theoretical astrophysics. Now, thanks to a fleet of new instruments with unprecedented resolving power that have come online recently, we have just started to unveil features in resolve images of protoplanetary disks, such as gaps and spiral arms, that are most likely associated with embedded (unseen) planets. By comparing observations with theoretical models of planet-disk interactions, the masses and orbits of these still forming planets may be constrained. Such planets may help us to directly test various planet formation models. This marks the onset of a new field — observational planet formation. I will introduce the current status of this field.

White dwarf planets

Directory of Open Access Journals (Sweden)

Bonsor Amy

2013-04-01

Full Text Available The recognition that planets may survive the late stages of stellar evolution, and the prospects for finding them around White Dwarfs, are growing. We discuss two aspects governing planetary survival through stellar evolution to the White Dwarf stage. First we discuss the case of a single planet, and its survival under the effects of stellar mass loss, radius expansion, and tidal orbital decay as the star evolves along the Asymptotic Giant Branch. We show that, for stars initially of 1 − 5 M⊙, any planets within about 1 − 5 AU will be engulfed, this distance depending on the stellar and planet masses and the planet's eccentricity. Planets engulfed by the star's envelope are unlikely to survive. Hence, planets surviving the Asymptotic Giant Branch phase will probably be found beyond ∼ 2 AU for a 1  M⊙ progenitor and ∼ 10 AU for a 5 M⊙ progenitor. We then discuss the evolution of two-planet systems around evolving stars. As stars lose mass, planet–planet interactions become stronger, and many systems stable on the Main Sequence become destabilised following evolution of the primary. The outcome of such instabilities is typically the ejection of one planet, with the survivor being left on an eccentric orbit. These eccentric planets could in turn be responsible for feeding planetesimals into the neighbourhood of White Dwarfs, causing observed pollution and circumstellar discs.

Tidal Heating in Multilayered Terrestrial Exoplanets

Science.gov (United States)

Henning, Wade G.; Hurford, Terry

2014-01-01

The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R(sub E) is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

Tidal heating in multilayered terrestrial exoplanets

Energy Technology Data Exchange (ETDEWEB)

Henning, Wade G.; Hurford, Terry, E-mail: wade.g.henning@nasa.gov [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

2014-07-01

The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R{sub E} is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

Tidal heating in multilayered terrestrial exoplanets

International Nuclear Information System (INIS)

Henning, Wade G.; Hurford, Terry

2014-01-01

The internal pattern and overall magnitude of tidal heating for spin-synchronous terrestrial exoplanets from 1 to 2.5 R E is investigated using a propagator matrix method for a variety of layer structures. Particular attention is paid to ice-silicate hybrid super-Earths, where a significant ice mantle is modeled to rest atop an iron-silicate core, and may or may not contain a liquid water ocean. We find multilayer modeling often increases tidal dissipation relative to a homogeneous model, across multiple orbital periods, due to the ability to include smaller volume low viscosity regions, and the added flexure allowed by liquid layers. Gradations in parameters with depth are explored, such as allowed by the Preliminary Earth Reference Model. For ice-silicate hybrid worlds, dramatically greater dissipation is possible beyond the case of a silicate mantle only, allowing non-negligible tidal activity to extend to greater orbital periods than previously predicted. Surface patterns of tidal heating are found to potentially be useful for distinguishing internal structure. The influence of ice mantle depth and water ocean size and position are shown for a range of forcing frequencies. Rates of orbital circularization are found to be 10-100 times faster than standard predictions for Earth-analog planets when interiors are moderately warmer than the modern Earth, as well as for a diverse range of ice-silicate hybrid super-Earths. Circularization rates are shown to be significantly longer for planets with layers equivalent to an ocean-free modern Earth, as well as for planets with high fractions of either ice or silicate melting.

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.

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.

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

The Scattering Outcomes of Kepler Circumbinary Planets: Planet Mass Ratio

Energy Technology Data Exchange (ETDEWEB)

Gong, Yan-Xiang; Ji, Jianghui, E-mail: yxgong@pmo.ac.cn, E-mail: jijh@pmo.ac.cn [CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2017-11-01

Recent studies reveal that the free eccentricities of Kepler-34b and Kepler-413b are much larger than their forced eccentricities, implying that scattering events may take place in their formation. The observed orbital configuration of Kepler-34b cannot be well reproduced in disk-driven migration models, whereas a two-planet scattering scenario can play a significant role of shaping the planetary configuration. These studies indicate that circumbinary planets discovered by Kepler may have experienced scattering process. In this work, we extensively investigate the scattering outcomes of circumbinary planets focusing on the effects of planet mass ratio . We find that the planetary mass ratio and the the initial relative locations of planets act as two important parameters that affect the eccentricity distribution of the surviving planets. As an application of our model, we discuss the observed orbital configurations of Kepler-34b and Kepler-413b. We first adopt the results from the disk-driven models as the initial conditions, then simulate the scattering process that occurs in the late evolution stage of circumbinary planets. We show that the present orbital configurations of Kepler-34b and Kepler-413b can be well reproduced when considering a two unequal-mass planet ejection model. Our work further suggests that some of the currently discovered circumbinary single-planet systems may be survivors of original multiple-planet systems. The disk-driven migration and scattering events occurring in the late stage both play an irreplaceable role in sculpting the final systems.

A half-century of terrestrial analog studies: From craters on the Moon to searching for life on Mars

Science.gov (United States)

Léveillé, Richard

2010-03-01

Terrestrial analogs to the Moon and Mars have been used to advance knowledge in planetary science for over a half-century. They are useful in studies of comparative geology of the terrestrial planets and rocky moons, in astronaut training and testing of exploration technologies, and in developing hypotheses and exploration strategies in astrobiology. In fact, the use of terrestrial analogs can be traced back to the origins of comparative geology and astrobiology, and to the early phases of the Apollo astronaut program. Terrestrial analog studies feature prominently throughout the history of both NASA and the USGS' Astrogeology Research Program. In light of current international plans for a return missions to the Moon, and eventually to send sample return and manned missions to Mars, as well as the recent creation of various analog research and development programs, this historical perspective is timely.

SCCmecFinder, a Web-Based Tool for Typing of Staphylococcal Cassette Chromosome mec in Staphylococcus aureus Using Whole-Genome Sequence Data

DEFF Research Database (Denmark)

Kaya, Hülya; Hasman, Henrik; Larsen, Jesper

2018-01-01

Typing of methicillin-resistant Staphylococcus aureus (MRSA) is important in infection control and surveillance. The current nomenclature of MRSA includes the genetic background of the S. aureus strain determined by multilocus sequence typing (MLST) or equivalent methods like spa typing and typing...... of the genetic background and SCCmec, but so far, no bioinformatic tools for SCCmec typing have been available. Here, we report the development and evaluation of SCCmecFinder for characterization of the SCCmec element from S. aureus WGS data. SCCmecFinder is able to identify all SCCmec element types, designated...... a diverse collection of clinical isolates (n = 93) showed a high typeability level of 96.7%, which increased to 98.9% upon modification of the default settings. In conclusion, SCCmecFinder can be an alternative to more laborious SCCmec typing methods and is freely available at https...

EFFECTS OF STELLAR FLUX ON TIDALLY LOCKED TERRESTRIAL PLANETS: DEGREE-1 MANTLE CONVECTION AND LOCAL MAGMA PONDS

International Nuclear Information System (INIS)

Gelman, S. E.; Elkins-Tanton, L. T.; Seager, S.

2011-01-01

We model the geodynamical evolution of super-Earth exoplanets in synchronous rotation about their star. While neglecting the effects of a potential atmosphere, we explore the parameter spaces of both the Rayleigh number and intensity of incoming stellar flux, and identify two main stages of mantle convection evolution. The first is a transient stage in which a lithospheric temperature and thickness dichotomy emerges between the substellar and the antistellar hemispheres, while the style of mantle convection is dictated by the Rayleigh number. The second stage is the development of degree-1 mantle convection. Depending on mantle properties, the timescale of onset of this second stage of mantle evolution varies from order 1 to 100 billion years of simulated planetary evolution. Planets with higher Rayleigh numbers (due to, for instance, larger planetary radii than the Earth) and planets whose incoming stellar flux is high (likely for most detectable exoplanets) will develop degree-1 mantle convection most quickly, on the order of 1 billion years, which is within the age of many planetary systems. Surface temperatures range from 220 K to 830 K, implying the possibility of liquid water in some regions near the surface. These results are discussed in the context of stable molten magma ponds on hotter planets, and the habitability of super-Earths which may lie outside the Habitable Zone.

Extrasolar planets: constraints for planet formation models.

Science.gov (United States)

Santos, Nuno C; Benz, Willy; Mayor, Michel

2005-10-14

Since 1995, more than 150 extrasolar planets have been discovered, most of them in orbits quite different from those of the giant planets in our own solar system. The number of discovered extrasolar planets demonstrates that planetary systems are common but also that they may possess a large variety of properties. As the number of detections grows, statistical studies of the properties of exoplanets and their host stars can be conducted to unravel some of the key physical and chemical processes leading to the formation of planetary systems.

Knickpoint finder: A software tool that improves neotectonic analysis

Science.gov (United States)

Queiroz, G. L.; Salamuni, E.; Nascimento, E. R.

2015-03-01

This work presents a new software tool for morphometric analysis of drainage networks based on the methods of Hack (1973) and Etchebehere et al. (2004). This tool is applicable to studies of morphotectonics and neotectonics. The software used a digital elevation model (DEM) to identify the relief breakpoints along drainage profiles (knickpoints). The program was coded in Python for use on the ArcGIS platform and is called Knickpoint Finder. A study area was selected to test and evaluate the software's ability to analyze and identify neotectonic morphostructures based on the morphology of the terrain. For an assessment of its validity, we chose an area of the James River basin, which covers most of the Piedmont area of Virginia (USA), which is an area of constant intraplate seismicity and non-orogenic active tectonics and exhibits a relatively homogeneous geodesic surface currently being altered by the seismogenic features of the region. After using the tool in the chosen area, we found that the knickpoint locations are associated with the geologic structures, epicenters of recent earthquakes, and drainages with rectilinear anomalies. The regional analysis demanded the use of a spatial representation of the data after processing using Knickpoint Finder. The results were satisfactory in terms of the correlation of dense areas of knickpoints with active lineaments and the rapidity of the identification of deformed areas. Therefore, this software tool may be considered useful in neotectonic analyses of large areas and may be applied to any area where there is DEM coverage.

SOLUBILITY OF IRON IN METALLIC HYDROGEN AND STABILITY OF DENSE CORES IN GIANT PLANETS

International Nuclear Information System (INIS)

Wahl, Sean M.; Wilson, Hugh F.; Militzer, Burkhard

2013-01-01

The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is most commonly explained by the accretion of nebular hydrogen and helium onto a large core of terrestrial-like composition. The fate of this core has important consequences for the evolution of the interior structure of the planet. It has recently been shown that H 2 O, MgO, and SiO 2 dissolve in liquid metallic hydrogen at high temperature and pressure. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find dissolution of iron to be strongly favored above 2000 K over the entire pressure range (0.4-4 TPa) considered. We compare with and summarize the results for solubilities on other probable core constituents. The calculations imply that giant planet cores are in thermodynamic disequilibrium with surrounding layers, promoting erosion and redistribution of heavy elements. Differences in solubility behavior between iron and rock may influence evolution of interiors, particularly for Saturn-mass planets. Understanding the distribution of iron and other heavy elements in gas giants may be relevant in understanding mass-radius relationships, as well as deviations in transport properties from pure hydrogen-helium mixtures

Origins and Destinations: Tracking Planet Composition through Planet Formation Simulations

Science.gov (United States)

Chance, Quadry; Ballard, Sarah

2018-01-01

There are now several thousand confirmed exoplanets, a number which far exceeds our resources to study them all in detail. In particular, planets around M dwarfs provide the best opportunity for in-depth study of their atmospheres by telescopes in the near future. The question of which M dwarf planets most merit follow-up resources is a pressing one, given that NASA’s TESS mission will soon find hundreds of such planets orbiting stars bright enough for both ground and spaced-based follow-up.Our work aims to predict the approximate composition of planets around these stars through n-body simulations of the last stage of planet formation. With a variety of initial disk conditions, we investigate how the relative abundances of both refractory and volatile compounds in the primordial planetesimals are mapped to the final planet outcomes. These predictions can serve to provide a basis for making an educated guess about (a) which planets to observe with precious resources like JWST and (b) how to identify them based on dynamical clues.

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

SCCmecFinder, a Web-Based Tool for Typing of Staphylococcal Cassette Chromosome mec in Staphylococcus aureus Using Whole-Genome Sequence Data.

Science.gov (United States)

Kaya, Hülya; Hasman, Henrik; Larsen, Jesper; Stegger, Marc; Johannesen, Thor Bech; Allesøe, Rosa Lundbye; Lemvigh, Camilla Koldbæk; Aarestrup, Frank Møller; Lund, Ole; Larsen, Anders Rhod

2018-01-01

Typing of methicillin-resistant Staphylococcus aureus (MRSA) is important in infection control and surveillance. The current nomenclature of MRSA includes the genetic background of the S. aureus strain determined by multilocus sequence typing (MLST) or equivalent methods like spa typing and typing of the mobile genetic element staphylococcal cassette chromosome mec (SCC mec ), which carries the mecA or mecC gene. Whereas MLST and spa typing are relatively simple, typing of SCC mec is less trivial because of its heterogeneity. Whole-genome sequencing (WGS) provides the essential data for typing of the genetic background and SCC mec , but so far, no bioinformatic tools for SCC mec typing have been available. Here, we report the development and evaluation of SCC mec Finder for characterization of the SCC mec element from S. aureus WGS data. SCC mec Finder is able to identify all SCC mec element types, designated I to XIII, with subtyping of SCC mec types IV (2B) and V (5C2). SCC mec elements are characterized by two different gene prediction approaches to achieve correct annotation, a Basic Local Alignment Search Tool (BLAST)-based approach and a k -mer-based approach. Evaluation of SCC mec Finder by using a diverse collection of clinical isolates ( n = 93) showed a high typeability level of 96.7%, which increased to 98.9% upon modification of the default settings. In conclusion, SCC mec Finder can be an alternative to more laborious SCC mec typing methods and is freely available at https://cge.cbs.dtu.dk/services/SCCmecFinder. IMPORTANCE SCC mec in MRSA is acknowledged to be of importance not only because it contains the mecA or mecC gene but also for staphylococcal adaptation to different environments, e.g., in hospitals, the community, and livestock. Typing of SCC mec by PCR techniques has, because of its heterogeneity, been challenging, and whole-genome sequencing has only partially solved this since no good bioinformatic tools have been available. In this

Human Splicing Finder: an online bioinformatics tool to predict splicing signals

OpenAIRE

Desmet, Francois-Olivier; Hamroun, Dalil; Lalande, Marine; Collod-Beroud, Gwenaelle; Claustres, Mireille; Beroud, Christophe

2009-01-01

International audience; Thousands of mutations are identified yearly. Although many directly affect protein expression, an increasing proportion of mutations is now believed to influence mRNA splicing. They mostly affect existing splice sites, but synonymous, non-synonymous or nonsense mutations can also create or disrupt splice sites or auxiliary cis-splicing sequences. To facilitate the analysis of the different mutations, we designed Human Splicing Finder (HSF), a tool to predict the effec...

Simulated JWST/NIRISS Transit Spectroscopy of Anticipated Tess Planets Compared to Select Discoveries from Space-based and Ground-based Surveys

Science.gov (United States)

Louie, Dana R.; Deming, Drake; Albert, Loic; Bouma, L. G.; Bean, Jacob; Lopez-Morales, Mercedes

2018-04-01

The Transiting Exoplanet Survey Satellite (TESS) will embark in 2018 on a 2 year wide-field survey mission, discovering over a thousand terrestrial, super-Earth and sub-Neptune-sized exoplanets ({R}pl}≤slant 4 {R}\\oplus ) potentially suitable for follow-up observations using the James Webb Space Telescope (JWST). This work aims to understand the suitability of anticipated TESS planet discoveries for atmospheric characterization by JWST’s Near InfraRed Imager and Slitless Spectrograph (NIRISS) by employing a simulation tool to estimate the signal-to-noise (S/N) achievable in transmission spectroscopy. We applied this tool to Monte Carlo predictions of the TESS expected planet yield and then compared the S/N for anticipated TESS discoveries to our estimates of S/N for 18 known exoplanets. We analyzed the sensitivity of our results to planetary composition, cloud cover, and presence of an observational noise floor. We find that several hundred anticipated TESS discoveries with radii 1.5 {R}\\oplus R}pl}≤slant 2.5 {R}\\oplus will produce S/N higher than currently known exoplanets in this radius regime, such as K2-3b or K2-3c. In the terrestrial planet regime, we find that only a few anticipated TESS discoveries will result in higher S/N than currently known exoplanets, such as the TRAPPIST-1 planets, GJ1132b, and LHS1140b. However, we emphasize that this outcome is based upon Kepler-derived occurrence rates, and that co-planar compact multi-planet systems (e.g., TRAPPIST-1) may be under-represented in the predicted TESS planet yield. Finally, we apply our calculations to estimate the required magnitude of a JWST follow-up program devoted to mapping the transition region between hydrogen-dominated and high molecular weight atmospheres. We find that a modest observing program of between 60 and 100 hr of charged JWST time can define the nature of that transition (e.g., step function versus a power law).

Types of Information Expected from a Photometric Search for Extra-Solar Planets

Science.gov (United States)

Borucki, William; Koch, David; Bell, James, III; Cuzzi, Jeffrey N. (Technical Monitor)

1994-01-01

The current theory postulates that planets are a consequence of the formation of stars from viscous accretion disks. Condensation from the hotter, inner portion of the accretion disk favors the formation of small rocky planets in the inner portion and the formation of gas giants in the cuter, cooler part. Consequently, terrestrial-type planets in inner orbits must be commonplace (Wetheril 1991). From the geometry of the situation (Borucki and Summers 1984), it can be shown that 1% of those planetary systems that resemble our solar system should show transits for Earth-sized (or larger) planets. Thus a photometric satellite that uses a wide field of view telescope and a large CCD array to simultaneously monitor 5000 target stars should detect 50 planetary systems. To verify that regularly recurring transits are occurring rather than statistical fluctuations of the stellar flux, demands observations that extend over several orbital periods so that the constancy of the orbital period, signal amplitude, and duration can be measured. Therefore, to examine the region from Mercury's orbit to that of the Earth requires a duration of three years whereas a search out to the orbit of mars requires about six years. The results of the observations should provide estimates of the distributions of planetary size and orbital radius, and the frequency of planetary systems that have Earth-sized planets in inner orbits. Because approximately one half of the star systems observed will be binary systems, the frequency of planetary systems orbit ' ing either one or both of the stars can also be determined. Furthermore, the complexity of the photometric signature of a planet transiting a pair of stars provides enough information to estimate the eccentricities of the planetary orbits. In summary, the statistical evidence from a photometric search of solar-like stars should be able to either confirm or deny the applicability of the current theory of planet formation and provide new

A terrestrial planet candidate in a temperate orbit around Proxima Centauri.

Science.gov (United States)

Anglada-Escudé, Guillem; Amado, Pedro J; Barnes, John; Berdiñas, Zaira M; Butler, R Paul; Coleman, Gavin A L; de la Cueva, Ignacio; Dreizler, Stefan; Endl, Michael; Giesers, Benjamin; Jeffers, Sandra V; Jenkins, James S; Jones, Hugh R A; Kiraga, Marcin; Kürster, Martin; López-González, Marίa J; Marvin, Christopher J; Morales, Nicolás; Morin, Julien; Nelson, Richard P; Ortiz, José L; Ofir, Aviv; Paardekooper, Sijme-Jan; Reiners, Ansgar; Rodríguez, Eloy; Rodrίguez-López, Cristina; Sarmiento, Luis F; Strachan, John P; Tsapras, Yiannis; Tuomi, Mikko; Zechmeister, Mathias

2016-08-25

At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.

Extra Solar Planetary Imaging Coronagraph and Science Requirements for the James Webb Telescope Observatory

Science.gov (United States)

Clampin, Mark

2004-01-01

1) Extra solar planetary imaging coronagraph. Direct detection and characterization of Jovian planets, and other gas giants, in orbit around nearby stars is a necessary precursor to Terrestrial Planet Finder 0 in order to estimate the probability of Terrestrial planets in our stellar neighborhood. Ground based indirect methods are biased towards large close in Jovian planets in solar systems unlikely io harbor Earthlike planets. Thus to estimate the relative abundances of terrestrial planets and to determine optimal observing strategies for TPF a pathfinder mission would be desired. The Extra-Solar Planetary Imaging Coronagraph (EPIC) is such a pathfinder mission. Upto 83 stellar systems are accessible with a 1.5 meter unobscured telescope and coronagraph combination located at the Earth-Sun L2 point. Incorporating radiometric and angular resolution considerations show that Jovians could be directly detected (5 sigma) in the 0.5 - 1.0 micron band outside of an inner working distance of 5/D with integration times of -10 - 100 hours per observation. The primary considerations for a planet imager are optical wavefront quality due to manufacturing, alignment, structural and thermal considerations. pointing stability and control, and manufacturability of coronagraphic masks and stops to increase the planetary-to- stellar contrast and mitigate against straylight. Previously proposed coronagraphic concepts are driven to extreme tolerances. however. we have developed and studied a mission, telescope and coronagraphic detection concept, which is achievable in the time frame of a Discovery class NASA mission. 2) Science requirements for the James Webb Space Telescope observatory. The James Webb Space Observatory (JWST) is an infrared observatory, which will be launched in 201 1 to an orbit at L2. JWST is a segmented, 18 mirror segment telescope with a diameter of 6.5 meters, and a clear aperture of 25 mA2. The telescope is designed to conduct imaging and spectroscopic

A neural network gravitational arc finder based on the Mediatrix filamentation method

Science.gov (United States)

Bom, C. R.; Makler, M.; Albuquerque, M. P.; Brandt, C. H.

2017-01-01

Context. Automated arc detection methods are needed to scan the ongoing and next-generation wide-field imaging surveys, which are expected to contain thousands of strong lensing systems. Arc finders are also required for a quantitative comparison between predictions and observations of arc abundance. Several algorithms have been proposed to this end, but machine learning methods have remained as a relatively unexplored step in the arc finding process. Aims: In this work we introduce a new arc finder based on pattern recognition, which uses a set of morphological measurements that are derived from the Mediatrix filamentation method as entries to an artificial neural network (ANN). We show a full example of the application of the arc finder, first training and validating the ANN on simulated arcs and then applying the code on four Hubble Space Telescope (HST) images of strong lensing systems. Methods: The simulated arcs use simple prescriptions for the lens and the source, while mimicking HST observational conditions. We also consider a sample of objects from HST images with no arcs in the training of the ANN classification. We use the training and validation process to determine a suitable set of ANN configurations, including the combination of inputs from the Mediatrix method, so as to maximize the completeness while keeping the false positives low. Results: In the simulations the method was able to achieve a completeness of about 90% with respect to the arcs that are input into the ANN after a preselection. However, this completeness drops to 70% on the HST images. The false detections are on the order of 3% of the objects detected in these images. Conclusions: The combination of Mediatrix measurements with an ANN is a promising tool for the pattern-recognition phase of arc finding. More realistic simulations and a larger set of real systems are needed for a better training and assessment of the efficiency of the method.

CONSTRAINING THE RADIATION AND PLASMA ENVIRONMENT OF THE KEPLER CIRCUMBINARY HABITABLE-ZONE PLANETS

Energy Technology Data Exchange (ETDEWEB)

Zuluaga, Jorge I. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Mason, Paul A. [New Mexico State University—DACC, Las Cruces, NM 88003 (United States); Cuartas-Restrepo, Pablo A. [FACom—Instituto de Física—FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellín (Colombia)

2016-02-20

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.

CONSTRAINING THE RADIATION AND PLASMA ENVIRONMENT OF THE KEPLER CIRCUMBINARY HABITABLE-ZONE PLANETS

International Nuclear Information System (INIS)

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

2016-01-01

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net

PLANET-PLANET SCATTERING IN PLANETESIMAL DISKS. II. PREDICTIONS FOR OUTER EXTRASOLAR PLANETARY SYSTEMS

International Nuclear Information System (INIS)

Raymond, Sean N.; Armitage, Philip J.; Gorelick, Noel

2010-01-01

We develop an idealized dynamical model to predict the typical properties of outer extrasolar planetary systems, at radii comparable to the Jupiter-to-Neptune region of the solar system. The model is based upon the hypothesis that dynamical evolution in outer planetary systems is controlled by a combination of planet-planet scattering and planetary interactions with an exterior disk of small bodies ('planetesimals'). Our results are based on 5000 long duration N-body simulations that follow the evolution of three planets from a few to 10 AU, together with a planetesimal disk containing 50 M + from 10 to 20 AU. For large planet masses (M ∼> M Sat ), the model recovers the observed eccentricity distribution of extrasolar planets. For lower-mass planets, the range of outcomes in models with disks is far greater than that which is seen in isolated planet-planet scattering. Common outcomes include strong scattering among massive planets, sudden jumps in eccentricity due to resonance crossings driven by divergent migration, and re-circularization of scattered low-mass planets in the outer disk. We present the distributions of the eccentricity and inclination that result, and discuss how they vary with planet mass and initial system architecture. In agreement with other studies, we find that the currently observed eccentricity distribution (derived primarily from planets at a ∼ -1 and periods in excess of 10 years will provide constraints on this regime. Finally, we present an analysis of the predicted separation of planets in two-planet systems, and of the population of planets in mean-motion resonances (MMRs). We show that, if there are systems with ∼ Jupiter-mass planets that avoid close encounters, the planetesimal disk acts as a damping mechanism and populates MMRs at a very high rate (50%-80%). In many cases, resonant chains (in particular the 4:2:1 Laplace resonance) are set up among all three planets. We expect such resonant chains to be common among massive

K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf

Science.gov (United States)

Smith, A. M. S.; Cabrera, J.; Csizmadia, Sz; Dai, F.; Gandolfi, D.; Hirano, T.; Winn, J. N.; Albrecht, S.; Alonso, R.; Antoniciello, G.; Barragán, O.; Deeg, H.; Eigmüller, Ph; Endl, M.; Erikson, A.; Fridlund, M.; Fukui, A.; Grziwa, S.; Guenther, E. W.; Hatzes, A. P.; Hidalgo, D.; Howard, A. W.; Isaacson, H.; Korth, J.; Kuzuhara, M.; Livingston, J.; Narita, N.; Nespral, D.; Nowak, G.; Palle, E.; Pätzold, M.; Persson, C. M.; Petigura, E.; Prieto-Arranz, J.; Rauer, H.; Ribas, I.; Van Eylen, V.

2018-03-01

We report the discovery in K2's Campaign 10 of a transiting terrestrial planet in an ultra-short-period orbit around an M3-dwarf. K2-137 b completes an orbit in only 4.3 h, the second shortest orbital period of any known planet, just 4 min longer than that of KOI 1843.03, which also orbits an M-dwarf. Using a combination of archival images, adaptive optics imaging, radial velocity measurements, and light-curve modelling, we show that no plausible eclipsing binary scenario can explain the K2 light curve, and thus confirm the planetary nature of the system. The planet, whose radius we determine to be 0.89 ± 0.09 R⊕, and which must have an iron mass fraction greater than 0.45, orbits a star of mass 0.463 ± 0.052 M⊙ and radius 0.442 ± 0.044 R⊙.

Locating Direction Finders in a Generalized Search and Rescue Network

Science.gov (United States)

1991-03-01

David A . Drake and Alfred B. Marsb. Conv-ersation at NationalI Security Agenc, 29 September 1990. 7. Daskin , Mark S. " A M-admum Fpeced Co-:efing...91 7 19 134 .flT/GORjEnSj9I-M LOCATING DIRECTION FIND’RS IN A GENERALIZED SEARCH AND RESCUE NETWORK THESIS Jean M. Steppe Captain, USAF AFIT/GOR/EN S...91-Mk-7 APPROVED FOR PUBLIC RELI ASE: DISTRIBUTION UNLIMITED. 1191-05734 .. 91.. .7 19 134 i i . nMIGOR4M.S/91-MI LOCATING DIRECTION FINDERS IW A

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.

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.

High pH ammonia toxicity, and the search for life on the Jovian planets.

Science.gov (United States)

Deal, P H; Souza, K A; Mack, H M

1975-10-01

Jovian plants have enviroments apparently suitable for the evolution of life, but nevertheless, present severe challenges to organisms. One such challenge arises from the presence of ammonia. Ammonia is an efficient biocide, its effect being dependent on pH as well as on concentration. The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural enviornments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, survival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is, nevertheless, two to three orders of magnitude longer than for E. coli. Our data support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

Eye safe laser range finders

International Nuclear Information System (INIS)

Snir, M.; Margaliot, M.; Amitzi, A.

2004-01-01

During the 1970's, Ruby (Q switched) laser based range finders with a wavelength of 694nm were first used. These lasers operated in a pulse mode within the visible light range and produced a risk for the eye retina. The laser beam striking the macula could damage the eye and might cause blindness. Over the years, Nd:YAG (Q switched) lasers were developed (operating at 1064nm) for range finding and designation uses. The wavelength of these lasers, operating in the near Infra-Red range (invisible), is also focused tightly on the retina. The human eye does not respond to the invisible light so there is no natural protection (eye blink reflex) as in the visible light. The operation of these lasers worldwide, especially when the laser beam is exposed, causes occasional eye accidents. Another risk is stemming from the use of observation systems with a high optical gain, in the laser operation areas, which enlarge the range of risk quite significantly. Therefore, research and development efforts were invested in order to introduce eye safe lasers. One of the solutions for this problem is presented in following document

PLANET-PLANET SCATTERING LEADS TO TIGHTLY PACKED PLANETARY SYSTEMS

International Nuclear Information System (INIS)

Raymond, Sean N.; Barnes, Rory; Veras, Dimitri; Armitage, Philip J.; Gorelick, Noel; Greenberg, Richard

2009-01-01

The known extrasolar multiple-planet systems share a surprising dynamical attribute: they cluster just beyond the Hill stability boundary. Here we show that the planet-planet scattering model, which naturally explains the observed exoplanet eccentricity distribution, can reproduce the observed distribution of dynamical configurations. We calculated how each of our scattered systems would appear over an appropriate range of viewing geometries; as Hill stability is weakly dependent on the masses, the mass-inclination degeneracy does not significantly affect our results. We consider a wide range of initial planetary mass distributions and find that some are poor fits to the observed systems. In fact, many of our scattering experiments overproduce systems very close to the stability boundary. The distribution of dynamical configurations of two-planet systems may provide better discrimination between scattering models than the distribution of eccentricity. Our results imply that, at least in their inner regions which are weakly affected by gas or planetesimal disks, planetary systems should be 'packed', with no large gaps between planets.

Planet-planet scattering leads to tightly packed planetary systems

OpenAIRE

Raymond, Sean N.; Barnes, Rory; Veras, Dimitri; Armitage, Philip J.; Gorelick, Noel; Greenberg, Richard

2009-01-01

The known extrasolar multiple-planet systems share a surprising dynamical attribute: they cluster just beyond the Hill stability boundary. Here we show that the planet-planet scattering model, which naturally explains the observed exoplanet eccentricity distribution, can reproduce the observed distribution of dynamical configurations. We calculated how each of our scattered systems would appear over an appropriate range of viewing geometries; as Hill stability is weakly dependent on the masse...

Influence of stellar multiplicity on planet formation. I. Evidence of suppressed planet formation due to stellar companions within 20 au and validation of four planets from the Kepler multiple planet candidates

International Nuclear Information System (INIS)

Wang, Ji; Fischer, Debra A.; Xie, Ji-Wei; Barclay, Thomas

2014-01-01

The planet occurrence rate for multiple stars is important in two aspects. First, almost half of stellar systems in the solar neighborhood are multiple systems. Second, the comparison of the planet occurrence rate for multiple stars to that for single stars sheds light on the influence of stellar multiplicity on planet formation and evolution. We developed a method of distinguishing planet occurrence rates for single and multiple stars. From a sample of 138 bright (K P < 13.5) Kepler multi-planet candidate systems, we compared the stellar multiplicity rate of these planet host stars to that of field stars. Using dynamical stability analyses and archival Doppler measurements, we find that the stellar multiplicity rate of planet host stars is significantly lower than field stars for semimajor axes less than 20 AU, suggesting that planet formation and evolution are suppressed by the presence of a close-in companion star at these separations. The influence of stellar multiplicity at larger separations is uncertain because of search incompleteness due to a limited Doppler observation time baseline and a lack of high-resolution imaging observation. We calculated the planet confidence for the sample of multi-planet candidates and find that the planet confidences for KOI 82.01, KOI 115.01, KOI 282.01, and KOI 1781.02 are higher than 99.7% and thus validate the planetary nature of these four planet candidates. This sample of bright Kepler multi-planet candidates with refined stellar and orbital parameters, planet confidence estimation, and nearby stellar companion identification offers a well-characterized sample for future theoretical and observational study.

FINDING EXTRATERRESTRIAL LIFE USING GROUND-BASED HIGH-DISPERSION SPECTROSCOPY

International Nuclear Information System (INIS)

Snellen, I. A. G.; Le Poole, R.; Brogi, M.; Birkby, J.; De Kok, R. J.

2013-01-01

Exoplanet observations promise one day to unveil the presence of extraterrestrial life. Atmospheric compounds in strong chemical disequilibrium would point to large-scale biological activity just as oxygen and methane do in the Earth's atmosphere. The cancellation of both the Terrestrial Planet Finder and Darwin missions means that it is unlikely that a dedicated space telescope to search for biomarker gases in exoplanet atmospheres will be launched within the next 25 years. Here we show that ground-based telescopes provide a strong alternative for finding biomarkers in exoplanet atmospheres through transit observations. Recent results on hot Jupiters show the enormous potential of high-dispersion spectroscopy to separate the extraterrestrial and telluric signals, making use of the Doppler shift of the planet. The transmission signal of oxygen from an Earth-twin orbiting a small red dwarf star is only a factor of three smaller than that of carbon monoxide recently detected in the hot Jupiter τ Boötis b, albeit such a star will be orders of magnitude fainter. We show that if Earth-like planets are common, the planned extremely large telescopes can detect oxygen within a few dozen transits. Ultimately, large arrays of dedicated flux-collector telescopes equipped with high-dispersion spectrographs can provide the large collecting area needed to perform a statistical study of life-bearing planets in the solar neighborhood.

Design Enhancements of the Fourier Kelvin Stellar Interferometer to Enable Detection of Earth Twins

Science.gov (United States)

Barry, Richard K.; Danchi, William C.; Lopez, Bruno; Rinehart, Stephan; Augereau, Jean-Charles; Beust, Herve; Bonfils, Xavier; Borde, Pascal; Kern, Pierre; Leger, Alain;

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.

Consequences of intense intermittent astrophysical radiation sources for terrestrial planets

Science.gov (United States)

Melott, Adrian

2011-11-01

Life on Earth has developed in the context of cosmic radiation backgrounds. This in turn can be a base for comparison with other potential life-bearing planets. Many kinds of strong radiation bursts are possible by astrophysical entities ranging from gamma-ray bursts at cosmological distances to the Sun itself. Many of these present potential hazards to the biosphere: on timescales long compared with human history, the probability of an event intense enough to disrupt life on the land surface or in the oceans becomes large. One of the mechanisms which comes into play even at moderate intensities is the ionization of the Earth's atmosphere, which leads through chemical changes (specifically, depletion of stratospheric ozone) to increased ultraviolet-B flux from the Sun reaching the surface. UVB is extremely hazardous to most life due to its strong absorption by the genetic material DNA and subsequent breaking of chemical bonds. We characterize intensities at the Earth and rates or upper limits on rates. We estimate how often a major extinction-level event is probable given the current state of knowledge. Moderate level events are dominated by the Sun, but the far more severe infrequent events are dominated by gamma-ray bursts and supernovae. So-called ``short-hard'' gamma-ray bursts are a substantial threat, comparable in magnitude to supernovae and greater than that of the higher-luminosity long bursts considered in most past work. Short bursts may come with little or no warning.

TF-finder: A software package for identifying transcription factors involved in biological processes using microarray data and existing knowledge base

Directory of Open Access Journals (Sweden)

Cui Xiaoqi

2010-08-01

Full Text Available Abstract Background Identification of transcription factors (TFs involved in a biological process is the first step towards a better understanding of the underlying regulatory mechanisms. However, due to the involvement of a large number of genes and complicated interactions in a gene regulatory network (GRN, identification of the TFs involved in a biology process remains to be very challenging. In reality, the recognition of TFs for a given a biological process can be further complicated by the fact that most eukaryotic genomes encode thousands of TFs, which are organized in gene families of various sizes and in many cases with poor sequence conservation except for small conserved domains. This poses a significant challenge for identification of the exact TFs involved or ranking the importance of a set of TFs to a process of interest. Therefore, new methods for recognizing novel TFs are desperately needed. Although a plethora of methods have been developed to infer regulatory genes using microarray data, it is still rare to find the methods that use existing knowledge base in particular the validated genes known to be involved in a process to bait/guide discovery of novel TFs. Such methods can replace the sometimes-arbitrary process of selection of candidate genes for experimental validation and significantly advance our knowledge and understanding of the regulation of a process. Results We developed an automated software package called TF-finder for recognizing TFs involved in a biological process using microarray data and existing knowledge base. TF-finder contains two components, adaptive sparse canonical correlation analysis (ASCCA and enrichment test, for TF recognition. ASCCA uses positive target genes to bait TFS from gene expression data while enrichment test examines the presence of positive TFs in the outcomes from ASCCA. Using microarray data from salt and water stress experiments, we showed TF-finder is very efficient in recognizing

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

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.

Decrease in Hysteresis of Planetary Climate for Planets with Long Solar Days

Science.gov (United States)

Abbot, Dorian S.; Bloch-Johnson, Jonah; Checlair, Jade; Farahat, Navah X.; Graham, R. J.; Plotkin, David; Popovic, Predrag; Spaulding-Astudillo, Francisco

2018-02-01

The ice-albedo feedback on rapidly rotating terrestrial planets in the habitable zone can lead to abrupt transitions (bifurcations) between a warm and a snowball (ice-covered) state, bistability between these states, and hysteresis in planetary climate. This is important for planetary habitability because snowball events may trigger rises in the complexity of life, but could also endanger complex life that already exists. Recent work has shown that planets tidally locked in synchronous rotation states will transition smoothly into the snowball state rather than experiencing bifurcations. Here we investigate the structure of snowball bifurcations on planets that are tidally influenced, but not synchronously rotating, so that they experience long solar days. We use PlaSIM, an intermediate-complexity global climate model, with a thermodynamic mixed layer ocean and the Sun’s spectrum. We find that the amount of hysteresis (the range in stellar flux for which there is bistability in climate) is significantly reduced for solar days with lengths of tens of Earth days, and disappears for solar days of hundreds of Earth days. These results suggest that tidally influenced planets orbiting M and K stars that are not synchronously rotating could have much less hysteresis associated with the snowball bifurcations than they would if they were rapidly rotating. This implies that the amount of time it takes them to escape a snowball state via CO2 outgassing would be greatly reduced, as would the period of cycling between the warm and snowball state if they have low CO2 outgassing rates.

COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION

International Nuclear Information System (INIS)

Stewart, Sarah T.; Leinhardt, Zoë M.

2012-01-01

Numerical simulations of the stochastic end stage of planet formation typically begin with a population of embryos and planetesimals that grow into planets by merging. We analyzed the impact parameters of collisions leading to the growth of terrestrial planets from recent N-body simulations that assumed perfect merging and calculated more realistic outcomes using a new analytic collision physics model. We find that collision outcomes are diverse and span all possible regimes: hit-and-run, merging, partial accretion, partial erosion, and catastrophic disruption. The primary outcomes of giant impacts between planetary embryos are approximately evenly split between partial accretion, graze-and-merge, and hit-and-run events. To explore the cumulative effects of more realistic collision outcomes, we modeled the growth of individual planets with a Monte Carlo technique using the distribution of impact parameters from N-body simulations. We find that fewer planets reached masses >0.7 M Earth using the collision physics model compared to simulations that assumed every collision results in perfect merging. For final planets with masses >0.7 M Earth , 60% are enriched in their core-to-mantle mass fraction by >10% compared to the initial embryo composition. Fragmentation during planet formation produces significant debris (∼15% of the final mass) and occurs primarily by erosion of the smaller body in partial accretion and hit-and-run events. In partial accretion events, the target body grows by preferentially accreting the iron core of the projectile and the escaping fragments are derived primarily from the silicate mantles of both bodies. Thus, the bulk composition of a planet can evolve via stochastic giant impacts.

Magic Planet

DEFF Research Database (Denmark)

Jacobsen, Aase Roland

2009-01-01

Med den digitale globe som omdrejningspunkt bestemmer publikum, hvilken planet, der er i fokus. Vores solsystem udforskes interaktivt. Udgivelsesdato: november......Med den digitale globe som omdrejningspunkt bestemmer publikum, hvilken planet, der er i fokus. Vores solsystem udforskes interaktivt. Udgivelsesdato: november...

Dance of the Planets

Science.gov (United States)

Riddle, Bob

2005-01-01

As students continue their monthly plotting of the planets along the ecliptic they should start to notice differences between inner and outer planet orbital motions, and their relative position or separation from the Sun. Both inner and outer planets have direct eastward motion, as well as retrograde motion. Inner planets Mercury and Venus,…

Exploring Disks Around Planets

Science.gov (United States)

Kohler, Susanna

2017-07-01

Giant planets are thought to form in circumstellar disks surrounding young stars, but material may also accrete into a smaller disk around the planet. Weve never detected one of these circumplanetary disks before but thanks to new simulations, we now have a better idea of what to look for.Image from previous work simulating a Jupiter-mass planet forming inside a circumstellar disk. The planet has its own circumplanetary disk of accreted material. [Frdric Masset]Elusive DisksIn the formation of giant planets, we think the final phase consists of accretion onto the planet from a disk that surrounds it. This circumplanetary disk is important to understand, since it both regulates the late gas accretion and forms the birthplace of future satellites of the planet.Weve yet to detect a circumplanetary disk thus far, because the resolution needed to spot one has been out of reach. Now, however, were entering an era where the disk and its kinematics may be observable with high-powered telescopes (like the Atacama Large Millimeter Array).To prepare for such observations, we need models that predict the basic characteristics of these disks like the mass, temperature, and kinematic properties. Now a researcher at the ETH Zrich Institute for Astronomy in Switzerland, Judit Szulgyi, has worked toward this goal.Simulating CoolingSzulgyi performs a series of 3D global radiative hydrodynamic simulations of 1, 3, 5, and 10 Jupiter-mass (MJ) giant planets and their surrounding circumplanetary disks, embedded within the larger circumstellar disk around the central star.Density (left column), temperature (center), and normalized angular momentum (right) for a 1 MJ planet over temperatures cooling from 10,000 K (top) to 1,000 K (bottom). At high temperatures, a spherical circumplanetary envelope surrounds the planet, but as the planet cools, the envelope transitions around 64,000 K to a flattened disk. [Szulgyi 2017]This work explores the effects of different planet temperatures and

MHD effects of the solar wind flow around planets

Directory of Open Access Journals (Sweden)

H. K. Biernat

2000-01-01

Full Text Available The study of the interaction of the solar wind with magnetized and unmagnetized planets forms a central topic of space research. Focussing on planetary magnetosheaths, we review some major developments in this field. Magnetosheath structures depend crucially on the orientation of the interplanetary magnetic field, the solar wind Alfvén Mach number, the shape of the obstacle (axisymmetric/non-axisymmetric, etc., the boundary conditions at the magnetopause (low/high magnetic shear, and the degree of thermal anisotropy of the plasma. We illustrate the cases of Earth, Jupiter and Venus. The terrestrial magnetosphere is axisymmetric and has been probed in-situ by many spacecraft. Jupiter's magnetosphere is highly non-axisymmetric. Furthermore, we study magnetohydrodynamic effects in the Venus magnetosheath.

The Trojan minor planets

Science.gov (United States)

Spratt, Christopher E.

1988-08-01

There are (March, 1988) 3774 minor planets which have received a permanent number. Of these, there are some whose mean distance to the sun is very nearly equal to that of Jupiter, and whose heliocentric longitudes from that planet are about 60°, so that the three bodies concerned (sun, Jupiter, minor planet) make an approximate equilateral triangle. These minor planets, which occur in two distinct groups, one preceding Jupiter and one following, have received the names of the heroes of the Trojan war. This paper concerns the 49 numbered minor planets of this group.

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

Inside-out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales

Science.gov (United States)

Hu, Xiao; Tan, Jonathan C.; Zhu, Zhaohuan; Chatterjee, Sourav; Birnstiel, Tilman; Youdin, Andrew N.; Mohanty, Subhanjoy

2018-04-01

Systems with tightly packed inner planets (STIPs) are very common. Chatterjee & Tan proposed Inside-out Planet Formation (IOPF), an in situ formation theory, to explain these planets. IOPF involves sequential planet formation from pebble-rich rings that are fed from the outer disk and trapped at the pressure maximum associated with the dead zone inner boundary (DZIB). Planet masses are set by their ability to open a gap and cause the DZIB to retreat outwards. We present models for the disk density and temperature structures that are relevant to the conditions of IOPF. For a wide range of DZIB conditions, we evaluate the gap-opening masses of planets in these disks that are expected to lead to the truncation of pebble accretion onto the forming planet. We then consider the evolution of dust and pebbles in the disk, estimating that pebbles typically grow to sizes of a few centimeters during their radial drift from several tens of astronomical units to the inner, ≲1 au scale disk. A large fraction of the accretion flux of solids is expected to be in such pebbles. This allows us to estimate the timescales for individual planet formation and the entire planetary system formation in the IOPF scenario. We find that to produce realistic STIPs within reasonable timescales similar to disk lifetimes requires disk accretion rates of ∼10‑9 M ⊙ yr‑1 and relatively low viscosity conditions in the DZIB region, i.e., a Shakura–Sunyaev parameter of α ∼ 10‑4.

Use of an online portal to facilitate clinical trial recruitment: a preliminary analysis of Fox Trial Finder.

Science.gov (United States)

Rocker, Charlotte; Cappelletti, Lily; Marshall, Claudia; Meunier, Claire C; Brooks, Deborah W; Sherer, Todd; Chowdhury, Sohini

2015-01-01

As in other therapeutic areas, clinical studies in Parkinson's disease (PD) face significant recruitment challenges. However, qualitative surveys suggest that individuals with PD are willing to participate in clinical research. The Michael J. Fox Foundation therefore established Fox Trial Finder in 2011 to facilitate connection between PD research teams and volunteers. Characterize the research volunteers (with and without PD) registered on Fox Trial Finder as of June 2014, and the published, recruiting studies to identify trends and highlight gaps between research requirements and available volunteers. Profiles of volunteers with and without PD were analyzed to explore trends in geography, demographics, family history and, for those volunteers with PD, disease progression and treatment history. Clinical study profiles were analyzed to determine study type, phase, sponsor, focus, location and eligibility criteria. The analysis focused on volunteers and studies based in the United States. The database contained 26,261 US-based volunteers, including 19,243 volunteers (73%) with PD and 7,018 (27%) controls without PD. The average time since diagnosis for PD volunteers was 5.7 years and the average age at diagnosis was 58 years. Control volunteers were more likely than volunteers with PD to be female (67% vs. 35%) and to have a family history of PD (49% vs. 12%). Fox Trial Finder's registration history to date demonstrates the high level of willingness among individuals affected by PD to participate in clinical research and provide a significant amount of personal health information to facilitate that participation.

GEMINI PLANET IMAGER SPECTROSCOPY OF THE HR 8799 PLANETS c AND d

International Nuclear Information System (INIS)

Ingraham, Patrick; Macintosh, Bruce; Marley, Mark S.; Saumon, Didier; Marois, Christian; Dunn, Jennifer; Erikson, Darren; Barman, Travis; Bauman, Brian; Burrows, Adam; Chilcote, Jeffrey K.; Fitzgerald, Michael P.; De Rosa, Robert J.; Dillon, Daren; Gavel, Donald; Doyon, René; Goodsell, Stephen J.; Hartung, Markus; Hibon, Pascale; Graham, James R.

2014-01-01

During the first-light run of the Gemini Planet Imager we obtained K-band spectra of exoplanets HR 8799 c and d. Analysis of the spectra indicates that planet d may be warmer than planet c. Comparisons to recent patchy cloud models and previously obtained observations over multiple wavelengths confirm that thick clouds combined with horizontal variation in the cloud cover generally reproduce the planets' spectral energy distributions. When combined with the 3 to 4 μm photometric data points, the observations provide strong constraints on the atmospheric methane content for both planets. The data also provide further evidence that future modeling efforts must include cloud opacity, possibly including cloud holes, disequilibrium chemistry, and super-solar metallicity

Inside-out planet formation

International Nuclear Information System (INIS)

Chatterjee, Sourav; Tan, Jonathan C.

2014-01-01

The compact multi-transiting planet systems discovered by Kepler challenge planet formation theories. Formation in situ from disks with radial mass surface density, Σ, profiles similar to the minimum mass solar nebula but boosted in normalization by factors ≳ 10 has been suggested. We propose that a more natural way to create these planets in the inner disk is formation sequentially from the inside-out via creation of successive gravitationally unstable rings fed from a continuous stream of small (∼cm-m size) 'pebbles', drifting inward via gas drag. Pebbles collect at the pressure maximum associated with the transition from a magnetorotational instability (MRI)-inactive ('dead zone') region to an inner MRI-active zone. A pebble ring builds up until it either becomes gravitationally unstable to form an ∼1 M ⊕ planet directly or induces gradual planet formation via core accretion. The planet may undergo Type I migration into the active region, allowing a new pebble ring and planet to form behind it. Alternatively, if migration is inefficient, the planet may continue to accrete from the disk until it becomes massive enough to isolate itself from the accretion flow. A variety of densities may result depending on the relative importance of residual gas accretion as the planet approaches its isolation mass. The process can repeat with a new pebble ring gathering at the new pressure maximum associated with the retreating dead-zone boundary. Our simple analytical model for this scenario of inside-out planet formation yields planetary masses, relative mass scalings with orbital radius, and minimum orbital separations consistent with those seen by Kepler. It provides an explanation of how massive planets can form with tightly packed and well-aligned system architectures, starting from typical protoplanetary disk properties.

Formation of S-type planets in close binaries: scattering induced tidal capture of circumbinary planets

Science.gov (United States)

Gong, Yan-Xiang; Ji, Jianghui

2018-05-01

Although several S-type and P-type planets in binary systems were discovered in past years, S-type planets have not yet been found in close binaries with an orbital separation not more than 5 au. Recent studies suggest that S-type planets in close binaries may be detected through high-accuracy observations. However, nowadays planet formation theories imply that it is difficult for S-type planets in close binaries systems to form in situ. In this work, we extensively perform numerical simulations to explore scenarios of planet-planet scattering among circumbinary planets and subsequent tidal capture in various binary configurations, to examine whether the mechanism can play a part in producing such kind of planets. Our results show that this mechanism is robust. The maximum capture probability is ˜10%, which can be comparable to the tidal capture probability of hot Jupiters in single star systems. The capture probability is related to binary configurations, where a smaller eccentricity or a low mass ratio of the binary will lead to a larger probability of capture, and vice versa. Furthermore, we find that S-type planets with retrograde orbits can be naturally produced via capture process. These planets on retrograde orbits can help us distinguish in situ formation and post-capture origin for S-type planet in close binaries systems. The forthcoming missions (PLATO) will provide the opportunity and feasibility to detect such planets. Our work provides several suggestions for selecting target binaries in search for S-type planets in the near future.

STABLE CONIC-HELICAL ORBITS OF PLANETS AROUND BINARY STARS: ANALYTICAL RESULTS

Energy Technology Data Exchange (ETDEWEB)

Oks, E. [Physics Department, 206 Allison Lab., Auburn University, Auburn, AL 36849 (United States)

2015-05-10

Studies of planets in binary star systems are especially important because it was estimated that about half of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges. One-planet binary star systems (OBSS) have a limited analogy to objects studied in atomic/molecular physics: one-electron Rydberg quasimolecules (ORQ). Specifically, ORQ, consisting of two fully stripped ions of the nuclear charges Z and Z′ plus one highly excited electron, are encountered in various plasmas containing more than one kind of ion. Classical analytical studies of ORQ resulted in the discovery of classical stable electronic orbits with the shape of a helix on the surface of a cone. In the present paper we show that despite several important distinctions between OBSS and ORQ, it is possible for OBSS to have stable planetary orbits in the shape of a helix on a conical surface, whose axis of symmetry coincides with the interstellar axis; the stability is not affected by the rotation of the stars. Further, we demonstrate that the eccentricity of the stars’ orbits does not affect the stability of the helical planetary motion if the center of symmetry of the helix is relatively close to the star of the larger mass. We also show that if the center of symmetry of the conic-helical planetary orbit is relatively close to the star of the smaller mass, a sufficiently large eccentricity of stars’ orbits can switch the planetary motion to the unstable mode and the planet would escape the system. We demonstrate that such planets are transitable for the overwhelming majority of inclinations of plane of the stars’ orbits (i.e., the projections of the planet and the adjacent start on the plane of the sky coincide once in a while). This means that conic-helical planetary orbits at binary stars can be detected photometrically. We consider, as an example, Kepler-16 binary stars to provide illustrative numerical data on the possible parameters and the

Forecast-based Integrated Flood Detection System for Emergency Response and Disaster Risk Reduction (Flood-FINDER)

Science.gov (United States)

Arcorace, Mauro; Silvestro, Francesco; Rudari, Roberto; Boni, Giorgio; Dell'Oro, Luca; Bjorgo, Einar

2016-04-01

Most flood prone areas in the globe are mainly located in developing countries where making communities more flood resilient is a priority. Despite different flood forecasting initiatives are now available from academia and research centers, what is often missing is the connection between the timely hazard detection and the community response to warnings. In order to bridge the gap between science and decision makers, UN agencies play a key role on the dissemination of information in the field and on capacity-building to local governments. In this context, having a reliable global early warning system in the UN would concretely improve existing in house capacities for Humanitarian Response and the Disaster Risk Reduction. For those reasons, UNITAR-UNOSAT has developed together with USGS and CIMA Foundation a Global Flood EWS called "Flood-FINDER". The Flood-FINDER system is a modelling chain which includes meteorological, hydrological and hydraulic models that are accurately linked to enable the production of warnings and forecast inundation scenarios up to three weeks in advance. The system is forced with global satellite derived precipitation products and Numerical Weather Prediction outputs. The modelling chain is based on the "Continuum" hydrological model and risk assessments produced for GAR2015. In combination with existing hydraulically reconditioned SRTM data and 1D hydraulic models, flood scenarios are derived at multiple scales and resolutions. Climate and flood data are shared through a Web GIS integrated platform. First validation of the modelling chain has been conducted through a flood hindcasting test case, over the Chao Phraya river basin in Thailand, using multi temporal satellite-based analysis derived for the exceptional flood event of 2011. In terms of humanitarian relief operations, the EO-based services of flood mapping in rush mode generally suffer from delays caused by the time required for their activation, programming, acquisitions and

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

Surging Seas Risk Finder: A Tool for Local-Scale Flood Risk Assessments in Coastal Cities

Science.gov (United States)

Kulp, S. A.; Strauss, B.

2015-12-01

Local decision makers in coastal cities require accurate, accessible, and thorough assessments of flood exposure risk within their individual municipality, in their efforts to mitigate against damage due to future sea level rise. To fill this need, we have developed Climate Central's Surging Seas Risk Finder, an interactive data toolkit which presents our sea level rise and storm surge analysis for every coastal town, city, county, and state within the USA. Using this tool, policy makers can easily zoom in on their local place of interest to receive a detailed flood risk assessment, which synthesizes a wide range of features including total population, socially vulnerable population, housing, property value, road miles, power plants, schools, hospitals, and many other critical facilities. Risk Finder can also be used to identify specific points of interest in danger of exposure at different flood levels. Additionally, this tool provides localized storm surge probabilities and sea level rise projections at tidal gauges along the coast, so that users can quickly understand the risk of flooding in their area over the coming decades.

Life Finder Detectors: An Overview of Detector Technologies for Detecting Life on Other Worlds

Science.gov (United States)

Rauscher, Bernard J.; Domagal-Goldman, Shawn; Greenhouse, Matthew A.; Hsieh, Wen-Ting; McElwain, Michael W.; Moseley, Samuel H.; Noroozian, Omid; Norton, Tim; Kutyrev, Alexander; Rinehart, Stephen; stock, Joseph

2015-01-01

Future large space telescopes will seek evidence for life on other worlds by searching for spectroscopic biosignatures. Atmospheric biosignature gases include oxygen, ozone, water vapor, and methane. Non-biological gases, including carbon monoxide and carbon dioxide, are important for discriminating false positives. All of these gases imprint spectroscopic features in the UV through mid-IR that are potentially detectable using future space based coronagraphs or star shades for starlight suppression.Direct spectroscopic biosignature detection requires sensors capable of robustly measuring photon arrival rates on the order of 10 per resolution element per hour. Photon counting is required for some wavefront sensing and control approaches to achieve the requisite high contrast ratios. We review life finder detector technologies that either exist today, or are under development, that have the potential to meet these challenging requirements. We specifically highlight areas where more work or development is needed.Life finder detectors will be invaluable for a wide variety of other major science programs. Because of its cross cutting nature; UV, optical, and infrared (UVOIR) detector development features prominently in the 2010 National Research Council Decadal Survey, 'New Worlds, New Horizons in Astronomy and Astrophysics', and the NASA Cosmic Origins Program Technology Roadmap.

Terrestrial atmosphere, water and astrobiology

Directory of Open Access Journals (Sweden)

Coradini M.

2010-12-01

Full Text Available Primitive life, defined as a chemical system capable to transfer its molecular information via self-replication and also capable to evolve, originated about 4 billion years ago from the processing of organic molecules by liquid water. Terrestrial atmosphere played a key role in the process by allowing the permanent presence of liquid water and by participating in the production of carbon-based molecules. Water molecules exhibit specific properties mainly due to a dense network of hydrogen bonds. The carbon-based molecules were either home made in the atmosphere and/or in submarine hydrothermal systems or delivered by meteorites and micrometeorites. The search for possible places beyond the earth where the trilogy atmosphere/water/life could exist is the main objective of astrobiology. Within the Solar System, exploration missions are dedicated to Mars, Europa, Titan and the icy bodies. The discovery of several hundreds of extrasolar planets opens the quest to the whole Milky Way.

ABIOTIC O2 LEVELS ON PLANETS AROUND F, G, K, AND M STARS: POSSIBLE FALSE POSITIVES FOR LIFE?

International Nuclear Information System (INIS)

Harman, C. E.; Kasting, J. F.; Schwieterman, E. W.; Schottelkotte, J. C.

2015-01-01

In the search for life on Earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. Of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. The easiest of these species to observe in Earth's atmosphere is O 2 (and its photochemical byproduct, O 3 ). However, O 2 can also be produced abiotically by photolysis of CO 2 , followed by recombination of O atoms with each other. CO is produced in stoichiometric proportions. Whether O 2 and CO can accumulate to appreciable concentrations depends on the ratio of far-ultraviolet (FUV) to near-ultraviolet (NUV) radiation coming from the planet's parent star and on what happens to these gases when they dissolve in a planet's oceans. Using a one-dimensional photochemical model, we demonstrate that O 2 derived from CO 2 photolysis should not accumulate to measurable concentrations on planets around F- and G-type stars. K-star, and especially M-star planets, however, may build up O 2 because of the low NUV flux from their parent stars, in agreement with some previous studies. On such planets, a “false positive” for life is possible if recombination of dissolved CO and O 2 in the oceans is slow and if other O 2 sinks (e.g., reduced volcanic gases or dissolved ferrous iron) are small. O 3 , on the other hand, could be detectable at UV wavelengths (λ < 300 nm) for a much broader range of boundary conditions and stellar types

PADME – new code for modeling of planet georesources formation on heterogeneous computing systems

Directory of Open Access Journals (Sweden)

Protasov Viktor

2018-01-01

Full Text Available Many planets were detected in last few years, but there is no clear understanding of how they are formed. The fairly clear understanding of Solar system formation was founded with time, but there are some doubts yet because we don’t know what was at the beginning of the process, and what was acquired afterward. Moreover, formed ideas often couldn’t explain some features of other systems. Searching for Earth-like terrestrial planets is another very important problem. Even if any of found exoplanets will be similar to Earth, we couldn’t say that it is a “second Earth” exactly because its internal, geological, composition could be different – Venus is a vivid example. A new method for modelling of the planet formation process in a 3D2V formulation based on two-phase approach is presented in the paper. Fluids-in-cells method by Belotserkovskii-Davydov, modified with using the Godunov’s scheme, is used to model the gas component. The dust component is described by N-body system solved with the Particle-Mesh method. The method was accelerated by using of Nvidia CUDA technology. Gas-dust disk modelling results with the formation of sealing of gas and dust that could be interpreted as potential exoplanet are given.

Chemical signatures of planets: beyond solar-twins

Science.gov (United States)

Ramírez, I.; Meléndez, J.; Asplund, M.

2014-01-01

Context. Elemental abundance studies of solar twin stars suggest that the solar chemical composition contains signatures of the formation of terrestrial planets in the solar system, namely small but significant depletions of the refractory elements. Aims: To test whether these chemical signatures of planets are real, we study stars which, compared to solar twins, have less massive convective envelopes (therefore increasing the amplitude of the predicted effect) or are, arguably, more likely to host planets (thus increasing the frequency of signature detections). Methods: We measure relative atmospheric parameters and elemental abundances of two groups of stars: a "warm" late-F type dwarf sample (52 stars), and a sample of "metal-rich" solar analogs (59 stars). The strict differential approach that we adopt allows us to determine with high precision (errors ~0.01 dex) the degree of refractory element depletion in our stars independently of Galactic chemical evolution. By examining relative abundance ratio versus condensation temperature plots we are able to identify stars with "pristine" composition in each sample and to determine the degree of refractory-element depletion for the rest of our stars. We calculate what mixture of Earth-like and meteorite-like material corresponds to these depletions. Results: We detect refractory-element depletions with amplitudes up to about 0.15 dex. The distribution of depletion amplitudes for stars known to host gas giant planets is not different from that of the rest of stars. The maximum amplitude of depletion increases with effective temperature from 5650 K to 5950 K, while it appears to be constant for warmer stars (up to 6300 K). The depletions observed in solar twin stars have a maximum amplitude that is very similar to that seen here for both of our samples. Conclusions: Gas giant planet formation alone cannot explain the observed distributions of refractory-element depletions, leaving the formation of rocky material as a

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.

SECULAR BEHAVIOR OF EXOPLANETS: SELF-CONSISTENCY AND COMPARISONS WITH THE PLANET-PLANET SCATTERING HYPOTHESIS

Energy Technology Data Exchange (ETDEWEB)

Timpe, Miles; Barnes, Rory [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195 (United States); Kopparapu, Ravikumar; Raymond, Sean N. [Virtual Planetary Laboratory, Seattle, WA 98195 (United States); Greenberg, Richard [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Gorelick, Noel, E-mail: apskier@astro.washington.edu [Google, Inc., 1600 Amphitheater Parkway, Mountain View, CA 94043 (United States)

2013-09-15

If mutual gravitational scattering among exoplanets occurs, then it may produce unique orbital properties. For example, two-planet systems that lie near the boundary between circulation and libration of their periapses could result if planet-planet scattering ejected a former third planet quickly, leaving one planet on an eccentric orbit and the other on a circular orbit. We first improve upon previous work that examined the apsidal behavior of known multiplanet systems by doubling the sample size and including observational uncertainties. This analysis recovers previous results that demonstrated that many systems lay on the apsidal boundary between libration and circulation. We then performed over 12,000 three-dimensional N-body simulations of hypothetical three-body systems that are unstable, but stabilize to two-body systems after an ejection. Using these synthetic two-planet systems, we test the planet-planet scattering hypothesis by comparing their apsidal behavior, over a range of viewing angles, to that of the observed systems and find that they are statistically consistent regardless of the multiplicity of the observed systems. Finally, we combine our results with previous studies to show that, from the sampled cases, the most likely planetary mass function prior to planet-planet scattering follows a power law with index -1.1. We find that this pre-scattering mass function predicts a mutual inclination frequency distribution that follows an exponential function with an index between -0.06 and -0.1.

ATMOSPHERIC DYNAMICS OF TERRESTRIAL EXOPLANETS OVER A WIDE RANGE OF ORBITAL AND ATMOSPHERIC PARAMETERS

Energy Technology Data Exchange (ETDEWEB)

Kaspi, Yohai [Department of Earth and Planetary Sciences, Weizmann Institute of Science, 234 Herzl st., 76100, Rehovot (Israel); Showman, Adam P., E-mail: yohai.kaspi@weizmann.ac.il [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, 1629 University Blvd., Tucson, AZ 85721 (United States)

2015-05-01

The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.

ATMOSPHERIC DYNAMICS OF TERRESTRIAL EXOPLANETS OVER A WIDE RANGE OF ORBITAL AND ATMOSPHERIC PARAMETERS

International Nuclear Information System (INIS)

Kaspi, Yohai; Showman, Adam P.

2015-01-01

The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate

ColoFinder: a prognostic 9-gene signature improves prognosis for 871 stage II and III colorectal cancer patients

Directory of Open Access Journals (Sweden)

Mingguang Shi

2016-03-01

Full Text Available Colorectal cancer (CRC is a heterogeneous disease with a high mortality rate and is still lacking an effective treatment. Our goal is to develop a robust prognosis model for predicting the prognosis in CRC patients. In this study, 871 stage II and III CRC samples were collected from six gene expression profilings. ColoFinder was developed using a 9-gene signature based Random Survival Forest (RSF prognosis model. The 9-gene signature recurrence score was derived with a 5-fold cross validation to test the association with relapse-free survival, and the value of AUC was gained with 0.87 in GSE39582(95% CI [0.83–0.91]. The low-risk group had a significantly better relapse-free survival (HR, 14.8; 95% CI [8.17–26.8]; P < 0.001 than the high-risk group. We also found that the 9-gene signature recurrence score contributed more information about recurrence than standard clinical and pathological variables in univariate and multivariate Cox analyses when applied to GSE17536(p = 0.03 and p = 0.01 respectively. Furthermore, ColoFinder improved the predictive ability and better stratified the risk subgroups when applied to CRC gene expression datasets GSE14333, GSE17537, GSE12945and GSE24551. In summary, ColoFinder significantly improves the risk assessment in stage II and III CRC patients. The 9-gene prognostic classifier informs patient prognosis and treatment response.

Faint-Source-Star Planetary Microlensing: The Discovery of the Cold Gas-Giant Planet OGLE-2014-BLG-0676Lb

Science.gov (United States)

Rattenbury, N. J.; Bennett, D. P.; Sumi, T.; Koshimoto, N.; Bond, I. A.; Udalski, A.; Shvartzvald, Y.; Maoz, D.; Jorgensen, U. G.; Barry, R.;

Planets in Binary Star Systems

CERN Document Server

Haghighipour, Nader

2010-01-01

The discovery of extrasolar planets over the past decade has had major impacts on our understanding of the formation and dynamical evolution of planetary systems. There are features and characteristics unseen in our solar system and unexplainable by the current theories of planet formation and dynamics. Among these new surprises is the discovery of planets in binary and multiple-star systems. The discovery of such "binary-planetary" systems has confronted astrodynamicists with many new challenges, and has led them to re-examine the theories of planet formation and dynamics. Among these challenges are: How are planets formed in binary star systems? What would be the notion of habitability in such systems? Under what conditions can binary star systems have habitable planets? How will volatiles necessary for life appear on such planets? This volume seeks to gather the current research in the area of planets in binary and multistar systems and to familiarize readers with its associated theoretical and observation...

THE ORBITAL PHASES AND SECONDARY TRANSITS OF KEPLER-10b. A PHYSICAL INTERPRETATION BASED ON THE LAVA-OCEAN PLANET MODEL

International Nuclear Information System (INIS)

Rouan, D.; Deeg, H. J.; Demangeon, O.; Samuel, B.; Cavarroc, C.; Léger, A.; Fegley, B.

2011-01-01

The Kepler mission has made an important observation: the first detection of photons from a terrestrial planet by observing its phase curve (Kepler-10b). This opens a new field in exoplanet science: the possibility of obtaining information about the atmosphere and surface of rocky planets, objects of prime interest. In this Letter, we apply the Lava-ocean model to interpret the observed phase curve. The model, a planet without atmosphere and a surface partially made of molten rocks, has been proposed for planets of the class of CoRoT-7b, i.e., rocky planets very close to their star (at a few stellar radii). Kepler-10b is a typical member of this family. It predicts that the light from the planet has an important emission component in addition to the reflected one, even in the Kepler spectral band. Assuming an isotropical reflection of light by the planetary surface (Lambertian-like approximation), we find that a Bond albedo of ∼50% can account for the observed amplitude of the phase curve, as opposed to a first attempt where an unusually high value was found. We propose a physical process to explain this still large value of the albedo. The overall interpretation can be tested in the future with instruments such as the James Webb Space Telescope or the Exoplanet Characterization Observatory. Our model predicts a spectral dependence that is clearly distinguishable from that of purely reflected light and from that of a planet at a uniform temperature.

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.

Large impact events and atmospheric evolution on the terrestrial planets

International Nuclear Information System (INIS)

Grinspoon, D.H.

1989-01-01

The first task undertaken is the characterization of the impact rates in the inner solar system during the present time, and during the first billion years of Solar System history when the flux was changing rapidly. Once defined, these fluxes are used to model the long term cumulative effect of multiple impacts on planetary atmospheres. The implications of cometary impacts on evolution of the water and deuterium abundances on Venus are examined. The short lifetime of water on Venus suggests that the water abundance is in quasi-steady-state balance between loss by escape and replenishment by infall. In addition, the observed deuterium-to-hydrogen ratio on Venus is consistent with a steady state and does not necessarily imply a past water excess. Results are presented of a model incorporating a stochastic cometary source and nonthermal escape of hydrogen that produces the observed water abundance and D/H ratio. The stochastic variability of each of these quantities is shown to be large. Water on Venus is likely to be in a near steady state mediated by large comet impacts. The early history of water on the planet has been obscured by a history of random impacts. A study of the effects of impact-generated dust clouds on the primitive Earth leads to the conclusion that such clouds were significant perturbers of the early climate. The Earth was shrouded by an optically-thick dust cloud for ∼150-250 m.y.. During this time the surface temperature was equal to the planetary equilibrium temperature unless significant heating by impacts or surface heat flow existed beneath the dust cloud. The epoch of continuous dust shrouding was followed by a period of stochastically intermittent dust clouds occurring at greater intervals as the early intense bombardment subsided towards the present day flux

Partitioning of water between surface and mantle on terrestrial exoplanets: effect of surface-mantle water exchange parameterizations on ocean depth

Science.gov (United States)

Komacek, T. D.; Abbot, D. S.

2016-12-01

Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to their volatile delivery rate via planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld". The habitable zone for waterworlds is likely smaller than that for planets with partial land coverage because waterworlds lack the stabilizing silicate-weathering feedback. On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. We have explored how the incorporation of different mechanisms for the outgassing and regassing of water changes the volatile evolution of a planet. Specifically, we have examined three models for volatile cycling: a model with degassing and regassing both determined by the seafloor pressure, one with mantle temperature-dependent degassing and regassing rates, and a hybrid model that has the degassing rate driven by seafloor pressure and the regassing rate determined by the mantle temperature. We find that the volatile cycling in all three of these scenarios reaches a steady-state after a few billion years. Using these steady-states, we can make predictions from each model for how much water is needed to flood the surface and make a waterworld. We find that if volatile cycling is either solely temperature-dependent or pressure-dependent, exoplanets require a high abundance (more than 0.3% by mass) of water to have fully inundated surfaces. This is because the waterworld boundary for these models is regulated by how much water can be stuffed into the mantle. However, if degassing is more dependent on the seafloor pressure and regassing mainly dependent on mantle temperature, super-Earth mass planets with a total water fraction similar to that of the Earth (approximately 0.05% by mass) can become waterworlds. As a result, further understanding of the

The Project Of Another Low-Cost Metaphase Finder

International Nuclear Information System (INIS)

Furukawa, Akira

2016-01-01

The most popular and 'gold standard' phenomenon in Biological dosimetry is the appearance of dicentric chromosomes in metaphase in white blood cells. The metaphase finder is a tool for biological dosimetry that finds metaphase cells on slide glasses. The author and a software company were using new special software that was faster than conventional systems. A Nikon Eclipse Ni-E microscope with motorised X-Y stage, 4x objective lens and 1920 x 1024 pixels colour camera for hardware were used. The software uses mathematical morphology filters. The new system was compact and low-priced. And the remarkable point is, this system can be applicable not only to human blood, but also to non-human samples. The speed was 208-236 s per 5 x 20 mm area, while capturing 378 images, which achieved the aim of the project. The false-positive ratio achieved below 5% in some slides. (author)

In campus location finder using mobile application services

Science.gov (United States)

Fai, Low Weng; Audah, Lukman

2017-09-01

Navigation services become very common in this era, the application include Google Map, Waze and etc. Although navigation application contains the main routing service in open area but not all of the buildings are recorded in the database. In this project, an application is made for the indoor and outdoor navigation in Universiti Tun Hussein Onn Malaysia (UTHM). It is used to help outsider and new incoming students by navigating them from their current location to destination using mobile application name "U Finder". Thunkable website has been used to build the application for outdoor and indoor navigation. Outdoor navigation is linked to the Google Map and indoor navigation is using the QR code for positioning and routing picture for navigation. The outdoor navigation can route user to the main faculties in UTHM and indoor navigation is only done for the G1 building in UTHM.

The Star–Planet Connection. I. Using Stellar Composition to Observationally Constrain Planetary Mineralogy for the 10 Closest Stars

Science.gov (United States)

Hinkel, Natalie R.; Unterborn, Cayman T.

2018-01-01

The compositions of stars and planets are connected, but the definition of “habitability” and the “habitable zone” only take into account the physical relationship between the star and planet. Planets, however, are made truly habitable by both chemical and physical processes that regulate climatic and geochemical cycling between atmosphere, surface, and interior reservoirs. Despite this, an “Earth-like” planet is often defined as a planet made of a mixture of rock and Fe that is roughly 1 Earth-density. To understand the interior of a terrestrial planet, the stellar abundances of planet-building elements (e.g., Mg, Si, and Fe) can be used as a proxy for the planet’s composition. We explore the planetary mineralogy and structure for fictive planets around the 10 stars closest to the Sun using stellar abundances from the Hypatia Catalog. Although our sample contains stars that are both sub- and super-solar in their abundances, we find that the mineralogies are very similar for all 10 planets—since the error or spread in the stellar abundances create significant degeneracy in the models. We show that abundance uncertainties need to be on the order of [Fe/H] < 0.02 dex, [Si/H] < 0.01 dex, [Al/H] < 0.002 dex, while [Mg/H] and [Ca/H] < 0.001 dex in order to distinguish two unique planetary populations in our sample of 10 stars. While these precisions are high, we believe that they are possible given certain abundance techniques, in addition to methodological transparency, that have recently been demonstrated in the literature. However, without these precisions, the uncertainty in planetary structures will be so high that we will be unable to confidently state that a planet is like the Earth, or unlike anything we have ever seen. We made some cuts and ruled out a number of stars, but these 10 are still rather nearby.

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....

Alpha Elements' Effects on Planet Formation and the Hunt for Extragalactic Planets

Science.gov (United States)

Penny, Matthew; Rodriguez, Joseph E.; Beatty, Thomas; Zhou, George

2018-01-01

A star's likelihood of hosting a giant planet is well known to be strongly dependent on metallicity. However, little is known about what elements cause this correlation (e.g. bulk metals, iron, or alpha elements such as silicon and oxygen). This is likely because most planet searches target stars in the Galactic disk, and due to Galactic chemical evolution, alpha element abundances are themselves correlated with metallicity within a population. We investigate the feasibility of simultaneous transiting planet search towards the alpha-poor Sagittarius dwarf galaxy and alpha-rich Galactic bulge in a single field of view of DECam, that would enable a comparative study of planet frequency over an [alpha/Fe] baseline of ~0.4 dex. We show that a modestly sized survey could detect planet candidates in both populations, but that false positive rejection in Sgr Dwarf may be prohibitively expensive. Conversely, two-filter survey observations alone would be sufficient to rule out a large fraction of bulge false positives, enabling statistical validation of candidates with a modest follow-up investment. Although over a shorter [alpha/Fe] baseline, this survey would provide a test of whether it is alpha or iron that causes the planet metallicity correlation.

The inclusion of RPC only segments in the Barrel Muon Track Finder

CERN Document Server

CMS Collaboration

2018-01-01

On November 3, 2017 during the LHC fill 6360 and from the run number 306121 RPC-only segments were enable to trigger. In this document we show the impact of the RPC-only segments in the Barrel Muon Track Finder efficiency performance. The efficiency measurement was done with Tag and Probe cut and count following the Muon POG working point recommendations (tight ID and Particle Flow isolation requirements more details can be found in https://cds.cern.ch/record/2054113). The used dataset was ZMuMu corresponding to each period.

Hydrothermal simulation experiments as a tool for studies of the origin of life on Earth and other terrestrial planets: a review.

Science.gov (United States)

Holm, Nils G; Andersson, Eva

2005-08-01

life on Earth and probably also to the other terrestrial planets.

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.

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}.

A near infrared laser frequency comb for high precision Doppler planet surveys

Directory of Open Access Journals (Sweden)

Bally J.

2011-07-01

Full Text Available Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV measurements, with the most stable visible light spectrographs reporting RV results the order of 1 m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

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.

Search for a planet

International Nuclear Information System (INIS)

Tokovinin, A.A.

1986-01-01

The problem of search for star planets is discussed in a popular form. Two methods of search for planets are considered: astrometric and spectral. Both methods complement one another. An assumption is made that potential possessors of planets are in the first place yellow and red dwarfs with slow axial rotation. These stars are the most numerous representatives of Galaxy population

The Fate of Unstable Circumbinary Planets

Science.gov (United States)

Kohler, Susanna

2016-03-01

What happens to Tattooine-like planets that are instead in unstable orbits around their binary star system? A new study examines whether such planets will crash into a host star, get ejected from the system, or become captured into orbit around one of their hosts.Orbit Around a DuoAt this point we have unambiguously detected multiple circumbinary planets, raising questions about these planets formation and evolution. Current models suggest that it is unlikely that circumbinary planets would be able to form in the perturbed environment close their host stars. Instead, its thought that the planets formed at a distance and then migrated inwards.One danger such planets face when migrating is encountering ranges of radii where their orbits become unstable. Two scientists at the University of Chicago, Adam Sutherland and Daniel Fabrycky, have studied what happens when circumbinary planets migrate into such a region and develop unstable orbits.Producing Rogue PlanetsTime for planets to either be ejected or collide with one of the two stars, as a function of the planets starting distance (in AU) from the binary barycenter. Colors represent different planetary eccentricities. [Sutherland Fabrycky 2016]Sutherland and Fabrycky used N-body simulations to determine the fates of planets orbiting around a star system consisting of two stars a primary like our Sun and a secondary roughly a tenth of its size that are separated by 1 AU.The authors find that the most common fate for a circumbinary planet with an unstable orbit is ejection from the system; over 80% of unstable planets were ejected. This has interesting implications: if the formation of circumbinary planets is common, this mechanism could be filling the Milky Way with a population of free-floating, rogue planets that no longer are associated with their host star.The next most common outcome for unstable planets is collision with one of their host stars (most often the secondary), resulting inaccretion of the planet

The Digital Dividend of Terrestrial Broadcasting

CERN Document Server

Beutler, Roland

2012-01-01

The “digital revolution” of the last two decades has pervaded innumerable aspects of our daily lives and changed our planet irreversibly. The shift from analog to digital broadcasting has facilitated a seemingly infinite variety of new applications—audience interactivity being but one example. The greater efficiency and compression of digital media have endowed broadcasters with a “digital dividend” of spare transmission capacity over and above the requirements of terrestrial broadcasting. The question is, who will use it, and how? Comparing the European experience with that of broadcasters elsewhere in the world, the author sketches the current status of international frequency management, quantifies the value of the “dividend” itself, analyzes the details of the analog-to-digital switchovers already completed, and posits what the future holds for the sector. As we grapple with new devices, inconceivable a mere generation ago, that allow us to access digital media instantly, anywhere and at any...

The origin of high eccentricity planets: The dispersed planet formation regime for weakly magnetized disks

Directory of Open Access Journals (Sweden)

Yusuke Imaeda

2017-03-01

Full Text Available In the tandem planet formation regime, planets form at two distinct sites where solid particles are densely accumulated due to the on/off state of the magnetorotational instability (MRI. We found that tandem planet formation can reproduce the solid component distribution of the Solar System and tends to produce a smaller number of large planets through continuous pebble flow into the planet formation sites. In the present paper, we investigate the dependence of tandem planet formation on the vertical magnetic field of the protoplanetary disk. We calculated two cases of Bz=3.4×10−3 G and Bz=3.4×10−5 G at 100 AU as well as the canonical case of Bz=3.4×10−4 G. We found that tandem planet formation holds up well in the case of the strong magnetic field (Bz=3.4×10−3 G. On the other hand, in the case of a weak magnetic field (Bz=3.4×10−5 G at 100 AU, a new regime of planetary growth is realized: the planets grow independently at different places in the dispersed area of the MRI-suppressed region of r=8−30 AU at a lower accretion rate of M˙<10−7.4 M⊙yr−1. We call this the “dispersed planet formation” regime. This may lead to a system with a larger number of smaller planets that gain high eccentricity through mutual collisions.

Determining Symmetry Properties of Gravitational Fields of Terrestrial Group Planets

Directory of Open Access Journals (Sweden)

R.A. Kascheev

2016-09-01

Full Text Available Numerous models of gravity fields of the Solar system bodies have been constructed recently owing to successful space missions. These models are sets of harmonic coefficients of gravity potential expansion in series of spherical functions, which is Laplace series. The sets of coefficients are different in quantity of numerical parameters, sources and composition of the initial observational data, methods to obtain and process them, and, consequently, in a variety of properties and accuracy characteristics. For this reason, the task of comparison of different models of celestial bodies considered in the paper is of interest and relevant. The main purpose of this study is comparison of the models of gravitational potential of the Earth, Moon, Mars, and Venus with the quantitative criteria of different types of symmetries developed by us. It is assumed that some particular symmetry of the density distribution function of the planetary body causes similar symmetry of its gravitational potential. The symmetry of gravitational potential, in its turn, imposes additional conditions (restrictions, which must be satisfied by the harmonic coefficients. The paper deals with seven main types of symmetries: central, axial, two symmetries specular relative to the equatorial planes and prime meridian, as well as three rotational symmetries (at π angle around the coordinate system axes. According to the results of calculations carried out for the Earth, Moon, Mars, and Venus, the values of the criteria vary considerably for different types of symmetries and for different planets. It means that the specific value of each criterion corresponding to a particular celestial body is indicative of the properties and internal structure characteristics of the latter and, therefore, it can be used as a tool for comparative planetology. On the basis of the performed calculations, it is possible to distinguish two groups of celestial bodies having similar properties of

THREE PLANETS ORBITING WOLF 1061

Energy Technology Data Exchange (ETDEWEB)

Wright, D. J.; Wittenmyer, R. A.; Tinney, C. G.; Bentley, J. S.; Zhao, Jinglin, E-mail: duncan.wright@unsw.edu.au [Department of Astronomy and Australian Centre for Astrobiology, School of Physics, University of New South Wales, NSW 2052 (Australia)

2016-02-01

We use archival HARPS spectra to detect three planets orbiting the M3 dwarf Wolf 1061 (GJ 628). We detect a 1.36 M{sub ⊕} minimum-mass planet with an orbital period P = 4.888 days (Wolf 1061b), a 4.25 M{sub ⊕} minimum-mass planet with orbital period P = 17.867 days (Wolf 1061c), and a likely 5.21 M{sub ⊕} minimum-mass planet with orbital period P = 67.274 days (Wolf 1061d). All of the planets are of sufficiently low mass that they may be rocky in nature. The 17.867 day planet falls within the habitable zone for Wolf 1061 and the 67.274 day planet falls just outside the outer boundary of the habitable zone. There are no signs of activity observed in the bisector spans, cross-correlation FWHMs, calcium H and K indices, NaD indices, or Hα indices near the planetary periods. We use custom methods to generate a cross-correlation template tailored to the star. The resulting velocities do not suffer the strong annual variation observed in the HARPS DRS velocities. This differential technique should deliver better exploitation of the archival HARPS data for the detection of planets at extremely low amplitudes.

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.

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

International Deep Planet Survey, 317 stars to determine the wide-separated planet frequency

Science.gov (United States)

Galicher, R.; Marois, C.; Macintosh, B.; Zuckerman, B.; Song, I.; Barman, T.; Patience, J.

2013-09-01

Since 2000, more than 300 nearby young stars were observed for the International Deep Planet Survey with adaptive optics systems at Gemini (NIRI/NICI), Keck (Nirc2), and VLT (Naco). Massive young AF stars were included in our sample whereas they have generally been neglected in first generation surveys because the contrast and target distances are less favorable to image substellar companions. The most significant discovery of the campaign is the now well-known HR 8799 multi-planet system. This remarkable finding allows, for the first time, an estimate of the Jovians planet population at large separations (further than a few AUs) instead of deriving upper limits. During my presentation, I will present the survey showing images of multiple stars and planets. I will then propose a statistic study of the observed stars deriving constraints on the Jupiter-like planet frequency at large separations.

ABIOTIC O{sub 2} LEVELS ON PLANETS AROUND F, G, K, AND M STARS: POSSIBLE FALSE POSITIVES FOR LIFE?

Energy Technology Data Exchange (ETDEWEB)

Harman, C. E.; Kasting, J. F. [Geosciences Department, Pennsylvania State University, University Park, PA 16802 (United States); Schwieterman, E. W. [NASA Astrobiology Institute—Virtual Planetary Laboratory (United States); Schottelkotte, J. C., E-mail: ceharmanjr@psu.edu [Astronomy Department, Pennsylvania State University, University Park, PA 16802 (United States)

2015-10-20

In the search for life on Earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. Of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. The easiest of these species to observe in Earth's atmosphere is O{sub 2} (and its photochemical byproduct, O{sub 3}). However, O{sub 2} can also be produced abiotically by photolysis of CO{sub 2}, followed by recombination of O atoms with each other. CO is produced in stoichiometric proportions. Whether O{sub 2} and CO can accumulate to appreciable concentrations depends on the ratio of far-ultraviolet (FUV) to near-ultraviolet (NUV) radiation coming from the planet's parent star and on what happens to these gases when they dissolve in a planet's oceans. Using a one-dimensional photochemical model, we demonstrate that O{sub 2} derived from CO{sub 2} photolysis should not accumulate to measurable concentrations on planets around F- and G-type stars. K-star, and especially M-star planets, however, may build up O{sub 2} because of the low NUV flux from their parent stars, in agreement with some previous studies. On such planets, a “false positive” for life is possible if recombination of dissolved CO and O{sub 2} in the oceans is slow and if other O{sub 2} sinks (e.g., reduced volcanic gases or dissolved ferrous iron) are small. O{sub 3}, on the other hand, could be detectable at UV wavelengths (λ < 300 nm) for a much broader range of boundary conditions and stellar types.

High-Voltage Clock Driver for Photon-Counting CCD Characterization

Science.gov (United States)

Baker, Robert

2013-01-01

A document discusses the CCD97 from e2v technologies as it is being evaluated at Goddard Space Flight Center's Detector Characterization Laboratory (DCL) for possible use in ultra-low background noise space astronomy applications, such as Terrestrial Planet Finder Coronagraph (TPF-C). The CCD97 includes a photoncounting mode where the equivalent output noise is less than one electron. Use of this mode requires a clock signal at a voltage level greater than the level achievable by the existing CCD (charge-coupled-device) electronics. A high-voltage waveform generator has been developed in code 660/601 to support the CCD97 evaluation. The unit generates required clock waveforms at voltage levels from -20 to +50 V. It deals with standard and arbitrary waveforms and supports pixel rates from 50 to 500 kHz. The system is designed to interface with existing Leach CCD electronics.

The weak force and SETH: The search for Extra-Terrestrial Homochirality

Science.gov (United States)

MacDermott, Alexandra J.

1996-07-01

We propose that a search for extra-terrestrial life can be approached as a Search for Extra-Terrestrial Homochirality-SETH. Homochirality is probably a pre-condition for life, so a chiral influence may be required to get life started. We explain how the weak force mediated by the Z0 boson gives rise to a small parity-violating energy difference (PVED) between enantiomers, and discuss how the resulting small excess of the more stable enantiomer may be amplified to homochirality. Titan and comets are good places to test for emerging pre-biotic homochirality, while on Mars there may be traces of homochirality as a relic of extinct life. Our calculations of the PVED show that the natural L-amino acids are indeed more stable than their enantiomers, as are several key D-sugars and right-hand helical DNA. Thiosubstituted DNA analogues show particularly large PVEDs. L-quartz is also more stable than D-quartz, and we believe that further crystal counts should be carried out to establish whether reported excesses of L quartz are real. Finding extra-terrestrial molecules of the same hand as on Earth would lend support to the universal chiral influence of the weak force. We describe a novel miniaturized space polarimeter, called the SETH Cigar, which we hope to use to detect optical rotation on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. Even if we do not find the same hand as on Earth, finding extra-terrestrial optical rotation would be of enormous importance as it would still be the homochiral signature of life.

Modulation of Terrestrial Convection by Tropospheric Humidity, and Implications for Other Planets

Science.gov (United States)

Genio, Anthony Del

2013-01-01

For decades, deep cumulus convection was viewed as consisting partly of undilute plumes that do not interact with their surrounding environment in order to explain their observed tendency to reach or penetrate the tropical tropopause. This behavior was built into all cumulus parameterizations used in terrestrial global climate and numerical weather prediction models, and it still persists in some models today. In the past decade, though, some embarrassing failures of global models have come to light, notably their tendency to rain over land near noon rather than in late afternoon or evening as observed, and the absence in the models of the Madden-Julian Oscillation (MJO), the major source of intraseasonal (30-90 day) precipitation variability in the Indian Ocean, West Pacific, and surrounding continental regions. In the past decade it has become clear that an important missing component of parameterizations is strong turbulent entrainment of drier environmental air into cumulus updrafts, which reduces the buoyancy of the updrafts and thus limits their vertical development. Tropospheric humidity thus serves as a throttle on convective penetration to high altitudes and delays the convective response to large-scale destabilizing influences in the environment.

Towards Understanding the Climate of Venus Applications of Terrestrial Models to Our Sister Planet

CERN Document Server

Bonnet, Roger-Maurice; Grinspoon, David; Koumoutsaris, Symeon; Lebonnois, Sebastien; Titov, Dmitri

2013-01-01

ESA’s Venus Express Mission has monitored Venus since April 2006, and scientists worldwide have used mathematical models to investigate its atmosphere and model its circulation. This book summarizes recent work to explore and understand the climate of the planet through a research program under the auspices of the International Space Science Institute (ISSI) in Bern, Switzerland. Some of the unique elements that are discussed are the anomalies with Venus’ surface temperature (the huge greenhouse effect causes the surface to rise to 460°C, without which would plummet as low as -40°C), its unusual lack of solar radiation (despite being closer to the Sun, Venus receives less solar radiation than Earth due to its dense cloud cover reflecting 76% back) and the juxtaposition of its atmosphere and planetary rotation (wind speeds can climb up to 200 m/s, much faster than Venus’ sidereal day of 243 Earth-days).

Gravitational Microlensing of Earth-mass Planets

DEFF Research Database (Denmark)

Harpsøe, Kennet Bomann West

It was only 17 years ago that the first planet outside of our own solar system was detected in the form of 51 Pegasi b. This planet is unlike anything in our own solar system. In fact, this planet was the first representative of a class of planets later known as “hot Jupiters”– gas giants......, i.e. it is much easier to detect high mass planets in close orbits. With these two methods it is hard to detect planets in an exo-solar system with a structure similar to our own solar system; specifically, it is hard to detect Earth-like planets in Earth-like orbits. It is presently unknown how...... common such planets are in our galaxy. There are a few other known methods for detecting exoplanets which have very different bias patterns. This thesis has been divided into two parts, treating two of these other methods. Part I is dedicated to the method of gravitational microlensing, a method...

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

On the Effect of Planetary Stable Isotope Compositions on Growth and Survival of Terrestrial Organisms.

Directory of Open Access Journals (Sweden)

Xueshu Xie

Full Text Available Isotopic compositions of reactants affect the rates of chemical and biochemical reactions. Usually it is assumed that heavy stable isotope enrichment leads to progressively slower reactions. Yet the effect of stable isotopes may be nonlinear, as exemplified by the "isotopic resonance" phenomenon. Since the isotopic compositions of other planets of Solar system, including Mars and Venus, are markedly different from terrestrial (e.g., deuterium content is ≈5 and ≈100 times higher, respectively, it is far from certain that terrestrial life will thrive in these isotopic conditions. Here we found that Martian deuterium content negatively affected survival of shrimp in semi-closed biosphere on a year-long time scale. Moreover, the bacterium Escherichia coli grows slower at Martian isotopic compositions and even slower at Venus's compositions. Thus, the biological impact of varying stable isotope compositions needs to be taken into account when planning interplanetary missions.

Planet formation in Binaries

OpenAIRE

Thebault, Ph.; Haghighipour, N.

2014-01-01

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review her...

Planets in a Room

Science.gov (United States)

Giacomini, l.; Aloisi, F.; De Angelis, I.

2017-09-01

Teaching planetary science using a spherical projector to show the planets' surfaces is a very effective but usually very expensive idea. Whatsmore, it usually assumes the availability of a dedicated space and a trained user. "Planets in a room" is a prototypal low cost version of a small, spherical projector that teachers, museum, planetary scientists and other individuals can easily build and use on their own, to show and teach the planets The project of "Planets in a Room" was made by the italian non-profit association Speak Science with the collaboration of INAF-IAPS of Rome and the Roma Tre University (Dipartimento di Matematica e Fisica). This proposal was funded by the Europlanet Outreach Funding Scheme in 2016. "Planets in a room" will be presented during EPSC 2017 to give birth to the second phase of the project, when the outreach and research community will be involved and schools from all over Europe will be invited to participate with the aim of bringing planetary science to a larger audience.

The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Alternative thermal histories. Ph.D. Thesis

Science.gov (United States)

Leake, M. A.

1982-01-01

Interpretations supporting a differentiated, once active Mercury are listed. Alternative scenarios of the planet's thermal history involve: different distributions of accreted materials, including uranium and thorium-rich materials; variations of early melting; and different modes of plains and scarp formation. Arguments are advanced which strongly favor plains formation by volcanism, lack of a primordial surface, and possible identification of remnant tensional features. Studies of remotely sensed data which strongly suggest a modestly homogeneous surface of silicates imply core separation. Reasons for accepting or rejecting various hypotheses for thermal histories of the planet are mentioned.

Trapping planets in an evolving protoplanetary disk: preferred time, locations and planet mass

OpenAIRE

Baillié, Kévin; Charnoz, Sébastien; Pantin, Éric

2016-01-01

Planet traps are necessary to prevent forming planets from falling onto their host star by type I migration. Surface mass density and temperature gradient irregularities favor the apparition of traps and deserts. Such features are found at the dust sublimation lines and heat transition barriers. We study how planets may remain trapped or escape as they grow and as the disk evolves. We model the temporal viscous evolution of a protoplanetary disk by coupling its dynamics, thermodynamics, geome...

THE PAN-PACIFIC PLANET SEARCH. II. CONFIRMATION OF A TWO-PLANET SYSTEM AROUND HD 121056

Energy Technology Data Exchange (ETDEWEB)

Wittenmyer, Robert A.; Tinney, C. G. [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Wang, Liang [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012 (China); Liu, Fan [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Horner, Jonathan [Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW 2052 (Australia); Endl, Michael [McDonald Observatory, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States); Johnson, John Asher [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Carter, B. D., E-mail: rob@unsw.edu.au [Computational Engineering and Science Research Centre, University of Southern Queensland, Toowoomba, Queensland 4350 (Australia)

2015-02-10

Precise radial velocities from the Anglo-Australian Telescope (AAT) confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P = 89.1 ± 0.1 days, and m sin i = 1.35 ± 0.17 M{sub Jup}. These data also confirm the planetary nature of the outer companion, with m sin i = 3.9 ± 0.6 M{sub Jup} and a = 2.96 ± 0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.

THE PAN-PACIFIC PLANET SEARCH. II. CONFIRMATION OF A TWO-PLANET SYSTEM AROUND HD 121056

International Nuclear Information System (INIS)

Wittenmyer, Robert A.; Tinney, C. G.; Wang, Liang; Liu, Fan; Horner, Jonathan; Endl, Michael; Johnson, John Asher; Carter, B. D.

2015-01-01

Precise radial velocities from the Anglo-Australian Telescope (AAT) confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P = 89.1 ± 0.1 days, and m sin i = 1.35 ± 0.17 M Jup . These data also confirm the planetary nature of the outer companion, with m sin i = 3.9 ± 0.6 M Jup and a = 2.96 ± 0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet

Physics and Chemistry of Star and Planet Formation in the Alma ERA

Science.gov (United States)

Bergin, Edwin

2014-06-01

ALMA will open up new avenues of exploration encompassing the wide range of star formation in our galaxy and peering into the central heart of planet-forming circumstellar disks. As we seek to explore the origins of stars and planets molecular emission will be at the front and center of many studies probing gas physics and chemistry. In this talk I will discus some of the areas where we can expect significant advances due to the increased sensitivity and superb spatial resolution of ALMA. In star-forming cores, a rich chemistry is revealed that may be the simpler molecular precursors to more complex organics, such as amino acids, seen within primitive rocks in our own solar system. ALMA will provide new information regarding the relative spatial distribution within a given source for a host of organics, sampling tens to hundreds of transitions of a variety of molecules, including presumably new ones. In this area there is a rich synergy with existing ground and space-based data, including Herschel/Spitzer. Here the increased sampling of sources to be enabled by ALMA should bring greater clarity toward the key products of interstellar chemistry and further constrain processes. On smaller Solar System scales, for over a decade most observations of planet-forming disks focused on the dust thermal continuum emission as a probe of the gas content and structure. ALMA will enable reliable and direct studies of gas to explore the evolving physics of planet-formation, the gas dissipation timescales (i.e. the upper limit to the timescale for giant planet birth), and also the chemistry. It is this chemistry that sets the composition of gas giants and also influences the ultimate composition of water and organic materials that are delivered to terrestrial worlds. Here I will show how we can use molecular emission to determine the gas thermal structure of a disk system and the total gas content - key astrophysical quantities. This will also enable more constrained chemical

Thermal expansion and thermal stress in the moon and terrestrial planets - Clues to early thermal history

Science.gov (United States)

Solomon, S. C.; Chaiken, J.

1976-01-01

The paper discusses how features of the surface geology of the moon and also Mars and Mercury impose constraints on the volumetric expansion or contraction of a planet and consequently provide a test of thermal history models. The moon has changed very little in volume over the last 3.8 b.y. Thermal models satisfying this constraint involve early heating and perhaps melting of the outer 200 km of the moon and an initially cold interior. Mercury has contracted by about 2 km in radius since emplacement of its present surface, so core formation must predate that surface. A hot initial temperature distribution is implied.