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1

HI Detection of an ExtraSolar Planetary Atmosphere  

Microsoft Academic Search

The extra-solar planet discovered around HD 209458 is the unique one also detected through occultation. During its transit, we will obtain spectra of the HI and DI Lyman-Alpha line at 1215 Angstrom. The extremely extended planetary exosphere is expected to produce an absorption line against the stellar chromospheric Lyman-Alpha emission. Because hydrogen is the most abundant element and its scale

Alfred Vidal-Madjar

2001-01-01

2

Polarimetry Of Planetary Atmospheres: From The Solar System Gas Giants To Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The polarization of light reflected from a planet provides unique information on the atmosphere structure and scattering properties of particles in the upper atmosphere. The solar system planets show a large variety of atmospheric polarization properties, from the thick, highly polarizing haze on Titan and the poles of Jupiter, Rayleigh scattering by molecules on Uranus and Neptune, to clouds in the equatorial region of Jupiter or on Venus. Polarimetry is also a promising differential technique to search for and characterize extra-solar planets, e.g. with the future VLT planet finder instrument SPHERE. For the preparation of the SPHERE planet search program we have made a suite of polarimetric observations and models for the solar system gas giants. The phase angles for the outer planets are small for Earth bound observations and the integrated polarization is essentially zero due to the symmetric backscattering situation. However, a second order scattering effect produces a measurable limb polarization for resolved planetary disks. We have made a detailed model for the spectropolarimetric signal of the limb polarization of Uranus between 520 and 935 nm to derive scattering properties of haze and cloud particles and to predict the polarization signal from an extra-solar point of view. We are also investigating imaging polarimetry of the thick haze layers on Titan and the poles of Jupiter. Additionally, we have calculated a large grid of intensity and polarization phase curves for simpler atmosphere models of extrasolar planets.

Buenzli, Esther; Bazzon, A.; Schmid, H. M.

2011-09-01

3

Extrasolar Planetary Systems Near a Secular Separatrix  

Microsoft Academic Search

Extrasolar planetary systems display a range of behavior that can be understood in terms of the secular theory of classical celestial mechanics, including the motions of the major axes. Four planet pairs in the seventeen known extrasolar planetary systems with multiple planets (upsilo And, 47 UMa, 55 Cnc, and HD 128311), have trajectories in orbital element space that lie close

Rory Barnes; Richard Greenberg

2006-01-01

4

Dynamical Habitability of Known Extrasolar Planetary Systems  

Microsoft Academic Search

Habitability is usually defined as the requirement for a terrestrial planet's atmosphere to sustain liquid water. This definition can be complemented by the dynamical requirement that other planets in the system do not gravitationally perturb terrestrial planets outside of their habitable zone, the orbital region allowing the existence of liquid water. We quantify the dynamical habitability of 85 known extrasolar

Kristen Menou; Serge Tabachnik

2003-01-01

5

The chemistry of extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

This work examines the chemical nature of extrasolar planetary systems, considering both the host star and any potential terrestrial planets located within the system. Extrasolar planetary host stars are found to be enriched over non-host stars in several r- and s-process elements. These enrichments, however, are in keeping with general galactic chemical evolution trends. This implies that host stars have not experienced any unusual chemical processing or pollution and that the observed enrichments are primordial in nature. When combined with detailed chemical models, the dynamical models of O'Brien et al. (2006) are found to produce terrestrial planets with bulk elemental abundances in excellent agreement with observed planetary values. This clearly indicates that the combination of dynamical and chemical modeling applied here is successfully reproducing the terrestrial planets of the Solar System to the first order. Furthermore, these planets are found to form with a considerable amount of water, negating the need for large amounts of exogenous delivery. Little dependence on the orbital properties of Jupiter and Saturn is observed for the main rock-forming elements due to the largely homogenous disk composition calculated. The same modeling approach is applied to known extrasolar planetary systems. Terrestrial planets were found to be ubiquitous, forming in all simulations. Generally, small (< 1[Special characters omitted.] ) terrestrial planets are produced close to their host star with little radial mixing occurring. Planetary compositions are found to be diverse, ranging from Earth-like to refractory dominated and C-dominated, containing significant amounts of carbide material. Based on these simulations, stars with Solar elemental ratios are the best place to focus future Earth-like planet searches as these systems are found to produce the most Earthlike terrestrial planets which are located within the habitable zones of their systems and containing a significant amount of water. C-rich planets, although unusual, are expected to exist in ~20% of known extrasolar planetary systems based on their host star photospheric compositions. These planets are unlike any body we have previously observed and provide an exciting avenue for future observation and simulation.

Bond, Jade Chantelle

2008-06-01

6

The progress of exploring extra-solar planetary systems  

NASA Astrophysics Data System (ADS)

With the advance of the space exploring, the study of the extra-solar planetary systems becomes an interesting topic since such system may exist the life or even the modern civilization. In this paper we give a brief introduction on the discovery of extra-solar planetary systems, and discuss the feasibility of detection techniques and methods developed in recent years. In particular, we present detailed interpretations of the results by the radial velocity method. With the launch of some specific small satellites, we can predict the discovery of a large number of candidates of the extra-solar planetary systems. We can expect that the exploring of extra-solar planetary systems will have a prospective era in the near future.

Liu, Yu-Juan; Zhao, Gang

2005-09-01

7

Photochemistry of Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The Space Age started half a century ago. Today, with the completion of a fairly detailed study of the planets of the Solar System, we have begun studying exoplanets (or extrasolar planets). The overriding question in is to ask whether an exoplanet is habitable and harbors life, and if so, what the biosignatures ought to be. This forces us to confront the fundamental question of what controls the composition of an atmosphere. The composition of a planetary atmosphere reflects a balance between thermodynamic equilibrium chemistry (as in the interior of giant planets) and photochemistry (as in the atmosphere of Mars). The terrestrial atmosphere has additional influence from life (biochemistry). The bulk of photochemistry in planetary atmospheres is driven by UV radiation. Photosynthesis may be considered an extension of photochemistry by inventing a molecule (chlorophyll) that can harvest visible light. Perhaps the most remarkable feature of photochemistry is catalytic chemistry, the ability of trace amounts of gases to profoundly affect the composition of the atmosphere. Notable examples include HOx (H, OH and HO2) chemistry on Mars and chlorine chemistry on Earth and Venus. Another remarkable feature of photochemistry is organic synthesis in the outer solar system. The best example is the atmosphere of Titan. Photolysis of methane results in the synthesis of more complex hydrocarbons. The hydrocarbon chemistry inevitably leads to the formation of high molecular weight products, giving rise to aerosols when the ambient atmosphere is cool enough for them to condense. These results are supported by the findings of the recent Cassini mission. Lastly, photochemistry leaves a distinctive isotopic signature that can be used to trace back the evolutionary history of the atmosphere. Examples include nitrogen isotopes on Mars and sulfur isotopes on Earth. Returning to the question of biosignatures on an exoplanet, our Solar System experience tells us to look for speciation that reveals the reaction pathways, disequilibrium forcing (what portion of the irradiance of the central star is harvested?) and isotopic signatures that are fingerprints of photochemistry and biochemistry.

Yung, Y. L.

2005-12-01

8

Hydrodynamic escape from planetary atmospheres  

NASA Astrophysics Data System (ADS)

Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Due to the existence of a singularity point near the transonic point, it is difficult to find transonic steady state solutions by solving the time-independent hydrodynamic equations. In addition to that, most previous works assume that all energy driving the escape flow is deposited in one narrow layer. This assumption not only results in less accurate solutions to the hydrodynamic escape problem, but also makes it difficult to include other chemical and physical processes in the hydrodynamic escape models. In this work, a numerical model describing the transonic hydrodynamic escape from planetary atmospheres is developed. A robust solution technique is used to solve the time dependent hydrodynamic equations. The method has been validated in an isothermal atmosphere where an analytical solution is available. The hydrodynamic model is applied to 3 cases: hydrogen escape from small orbit extrasolar planets, hydrogen escape from a hydrogen rich early Earth's atmosphere, and nitrogen/methane escape from Pluto's atmosphere. Results of simulations on extrasolar planets are in good agreement with the observations of the transiting extrasolar planet HD209458b. Hydrodynamic escape of hydrogen from other hypothetical close-in extrasolar planets are simulated and the influence of hydrogen escape on the long-term evolution of these extrasolar planets are discussed. Simulations on early Earth suggest that hydrodynamic escape of hydrogen from a hydrogen rich early Earth's atmosphere is about two orders magnitude slower than the diffusion limited escape rate. A hydrogen rich early Earth's atmosphere could have been maintained by the balance between the hydrogen escape and the supply of hydrogen into the atmosphere by volcanic outgassing. Origin of life may have occurred in the organic soup ocean created by the efficient formation of prebiotic molecules in the hydrogen rich early Earth's atmosphere. Simulations show that hydrodynamic escape of nitrogen from Pluto is able to remove a ~3 km layer of ice over the age of the solar system. The escape flux of neutral nitrogen may interact with the solar wind at Pluto's orbit and may be detected by the New Horizon mission.

Tian, Feng

9

Extrasolar Planetary Habitable Zones and the Number of Gaias  

NASA Astrophysics Data System (ADS)

We present a general modelling scheme for assessing the suitability for life on any Earth-like extrasolar planet by calculating the habitable zone (HZ) in main-sequence-star planetary systems. Our approach is based on an integrated Earth system analysis that relates the boundaries of the HZ to the limits of C4-photosynthesis processes. Within this model, the evolution of the HZ for any main-sequence-star planetary system can be calculated straightforwardly, and a convenient filter can be constructed that picks the candidates for photosynthesis-based life from all the extrasolar planets discovered by novel observational methods. These results can be used to determine the average number of planets per planetary system that are within the HZ. With the help of a segment of the Drake equation, the number of ``Gaias'' (i.e., extrasolar terrestrial planets with a globally acting biosphere) can be estimated. Our calculation gives about half a million Gaias in the Milky Way.

von Bloh, W.; Franck, S.; Bounama, C.; Steffen, M.; Schönberner, D.; Schellnhuber, H.-J.

10

Atmospheric circulation of eccentric extrasolar giant planets  

NASA Astrophysics Data System (ADS)

This dissertation explores the three-dimensional coupling between radiative and dynamical processes in the atmospheres of eccentric extrasolar giant planets GJ436b, HAT-P-2b, and HD80606b. Extrasolar planets on eccentric orbits are subject to time-variable heating and probable non-synchronous rotation, which results in significant variations in global circulation and thermal patterns as a function of orbital phase. Atmospheric simulations for the low eccentricity (e=0.15) Neptune sized planet GJ436b reveal that when Neptune-like atmospheric compositions are assumed day/night temperature contrasts and equatorial jet speeds are significantly increased relative to models that assume a solar-like composition. Comparisons between our theoretical light curves and recent observations support a high metallicity atmosphere with disequilibrium carbon chemistry for GJ436b. The analysis of full-orbit light curve observations at 3.6 and 4.5 microns of the HAT-P-2 system reveal swings in the planet's temperature of more than 900 K during its significantly eccentric ( e=0.5) orbit with a four to six hour offset between periapse passage and the peak of the planet's observed flux. Comparisons between our atmospheric model of HAT-P-2b and the observed light curves indicate an increased carbon to oxygen ratio in HAT-P-2b's atmosphere compared to solar values. Atmospheric simulations of the highly eccentric (e=0.9) HD80606b show that flash-heating events completely alter planetary thermal and jet structures and that assumptions about the rotation period of this planet could affect the shape of light curve observations near periapse. Our simulations of HD80606b also show the development an atmospheric shock on the nightside of the planet that is associated with an observable thermal signature in our theoretical light curves. The simulations and observations presented in this dissertation mark an important step in the exploration of atmospheric circulation on the more than 300 exoplanets known to posses significantly non-zero eccentricities.

Lewis, Nikole Kae

11

Identifying Atomic and Molecular Absorption in an Extrasolar Planet Atmosphere  

NASA Astrophysics Data System (ADS)

A significant amount of Hubble Space Telescope time has been spent observing a normal bright main-sequence star, HD209458, which happens to also be home to one of the few transiting extrasolar planets. Time-series spectroscopic data taken with STIS and ASC are available in the archive covering numerous planetary transits over the past 7 years. These data have allowed the discovery of sodium absorption in HD209458b's atmosphere along with a hydrogen-rich extended exosphere. There is great potential for significant new discoveries with these data that could further constrain the chemical composition and chemical evolution of HD209458b. This proposal outlines steps toward improving our understanding of the chemical composition of extrasolar giant planet atmospheres by developing new models for the wavelength-dependent eclipse depth that may be directly compared to archival Hubble Space Telescope observations.;

Barman, Travis

2007-07-01

12

Extrasolar Planetary Habitable Zones and the Number of Gaias  

Microsoft Academic Search

We present a general modelling scheme for assessing the suitability for life on any Earth-like extrasolar planet by calculating the habitable zone (HZ) in main-sequence-star planetary systems. Our approach is based on an integrated Earth system analysis that relates the boundaries of the HZ to the limits of C4-photosynthesis processes. Within this model, the evolution of the HZ for any

W. von Bloh; S. Franck; C. Bounama; M. Steffen; D. Schönberner; H.-J. Schellnhuber

2001-01-01

13

Resonant Periodic Motion and the Stability of Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

Families of nearly circular periodic orbits of the planetary type are studied, close to the 3/1 mean motion resonance of the two planets, considered both with finite masses. Large regions of instability appear, depending on the total mass of the planets and on the ratio of their masses. Also, families of resonant periodic orbits at the 2/1 resonance have been studied, for a planetary system where the total mass of the planets is the 4% of the mass of the sun. In particular, the effect of the ratio of the masses on the stability is studied. It is found that a planetary system at this resonance is unstable if the mass of the outer planet is smaller than the mass of the inner planet. Finally, an application has been made for the stability of the observed extrasolar planetary systems HD82943 and Gliese 876, trapped at the 2/1 resonance.

Hadjidemetriou, John D.

2002-05-01

14

Modeling and Observing Extrasolar Planetary Transits  

NASA Astrophysics Data System (ADS)

A computer model, called the Exoplanetary Pixelization Transit Model (EPTM), is developed to calculate exoplanetary transit light curves and determine exoplanet properties from an observed transit light curve. To establish and test the accuracy of the model, an observation of XO-2 was conducted on 2008 Mar 17 where time-series photometry of the transit of XO-2b was collected. Based on the EPTM, XO-2 hosts a planet, XO-2b, with a planetary radius of R = 1.043 RJ, in a near circular orbit with semimajor axis a = 0.0360 AU and inclination angle i = 89.67. The EPTM also determined the length of the transit and the approximate start and end time of the ingress and egress. Here we describe how the EPTM works: (1) a theoretical light curve is calculated for an initial set of planetary parameters, RP , a, and i; (2) an observed light curve is used to calculate ?2 for that theoretical curve; (3) the planetary parameters are varied in a grid about their initial values to produce a multidimensional array of ?2 values; and (4) the minimum valley in this ?2 array is used to select most probable values and confidence intervals of the planetary parameters. We conclude with future prospects for studying light curve anomalies in exoplanetary transits.

Addison, Brett C.; Durrance, Samuel T.; Schwieterman, Edward W.

2010-02-01

15

The Atmospheres of Extrasolar Super-Earths  

Microsoft Academic Search

Extrasolar super-Earths (1-10 M?) are likely to exist with a wide range of atmospheres. While a number of these planets have already been discovered through radial velocities and microlensing, it will be the discovery of the first transiting super-Earths that will open the door to a variety of follow-up observations aimed at characterizing their atmospheres. Super-Earths may fill a large

Eliza Miller-Ricci; Sara Seager; Dimitar Sasselov

2009-01-01

16

A stability catalogue of the habitable zones in extrasolar planetary systems  

Microsoft Academic Search

In the near future, space missions will be launched (e.g. COROT, KEPLER) to detect Earth-like extrasolar planets. The orbital elements of these (still hypothetic) planets will contain some uncertainties that can only be eliminated by careful dynamical investigations of the hosting planetary systems. The proportion of extrasolar planetary systems with one known giant planet is high (~90 per cent). Therefore,

Zs. Sándor; Á. Süli; B. Érdi; E. Pilat-Lohinger; R. Dvorak

2007-01-01

17

A stability catalogue of the habitable zones in extrasolar planetary systems  

Microsoft Academic Search

In the near future there will be launched space missions (e.g. COROT, KEPLER), designed to detect Earth-like extrasolar planets. The orbital elements of these (still hypothetic) planets will contain some uncertainties, that can only be eliminated by careful dynamical investigations of the hosting planetary systems. The proportion of extrasolar planetary systems with one known giant planet is high ($\\\\sim 90

Zs. Sándor; Á. Süli; B. Érdi; E. Pilat-Lohinger; R. Dvorak

2007-01-01

18

Atmospheric Chemistry in Extrasolar Giant Planets or The Cosmic Shoreline  

NASA Astrophysics Data System (ADS)

Title: Atmospheric Chemistry in Extrasolar Giant Planets. Metallicity and C/O ratio are potential observables in spectra of EGPs. Both address the mode of planetary formation. Metallicity reveals itself best in molecules composed of more than one “metal” atom, such as CO2. C/O ratio is more complicated. There are parallels between the chemistry generated by 1994’s SL9 impacts on Jupiter and the chemistry of EGPs. In both, a hot gas quenches by cooling and rarefaction. In SL9, the impact-heated gas exploded, expanded, and cooled. In EGPs, quenching is a consequence of vertical mixing. Products of SL9 included S2, CS2, HCN, C2H4, CO, CO2, and carbonaceous hazes. All of these might be expected in EGPs. Close-in planets differ from SL9 in the photochemical consequences of stellar UV. Primary photolysis of H2S, NH3, and H2O creates free radicals that react with H2 to make atomic H. Abundant H attacks CH4 and promotes formation of C2H2 and HCN, which readily polymerize to make hazes. It is likely that such a haze is observed in HD 189733b. Title: Cosmic Shoreline. Volatile escape is the classic existential problem of planetary atmospheres. The problem has gained new currency now that we can begin to study escape, or the cumulative effects of escape, from extrasolar planets seen in transit. Already some intriguing patterns have emerged. In particular, transiting EGPs appear to fit a pattern seen in our own Solar System. The data show that atmospheres are found where escape velocity is high and (i) solar heating is low or (ii) impact velocities are low. In either case, the boundary between planets with and without atmospheres --- the cosmic shoreline, as it were --- is a simple power law that extends from Pluto to Jupiters and beyond.

Zahnle, Kevin

2011-09-01

19

Chemical Composition of Stars with Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

In this article we review surface abundances in stars which host planetary systems. Recent spectroscopic studies of stars with and without planetary systems have concluded that stars which host giant planets are more metal-rich than those without planets. We discover more subtle trends of different chemical elements as the number of detected exoplanets continues to grow. In particular, Li seems to be depleted in planet host stars. Knowledge of precise abundances of oxygen and carbon may help to understand the structure of extrasolar planets. However, in most cases, the abundance trends of planet-host stars are very similar to those of the comparison sample. Possible explanations for the abundance anomalies or the correlation between [Fe/H] and the presence of giant planets have certain implications for planetary formation and evolution theory, Galactic chemical evolution, and astrobiology. The latest results indicate that some metals other than iron may also have an important contribution to planet formation if the amount of iron is low. Stars that host terrestrial planets, that can be found at low-iron regime, are mostly enhanced by ?-elements.

Israelian, G.; Delgado-Mena, E.; Adibekyan, V.

2013-04-01

20

Extra-solar Oort cloud encounters and planetary impact rates  

SciTech Connect

Upper limits are estimated to the number density of extra-solar Oort clouds (ESOC) through which the solar system might pass and to the probable number of attendant planetary impacts by comets. All stars are assumed to have Oort clouds. The model is based on the observed stellar spatial density and the ratio of the total number density to the observed number density. It is estimated that 486 close stellar passages and 12,160 ESOC encounters may have occurred. Each encounter would have produced a shower of hyperbolic comets, with the results of 1-3 ESOC impacts with the earth. It is concluded that the great majority of terrestrial cratering events by comets have and will come from solar Oort cloud comets. 19 references.

Stern, A.

1987-01-01

21

Remote Sensing of Planetary Properties and Biosignatures on Extrasolar Terrestrial Planets  

NASA Astrophysics Data System (ADS)

The major goals of NASA's Terrestrial Planet Finder (TPF) and the European Space Agency's Darwin missions are to detect terrestrial-sized extrasolar planets directly and to seek spectroscopic evidence of habitable conditions and life. Here we recommend wavelength ranges and spectral features for these missions. We assess known spectroscopic molecular band features of Earth, Venus, and Mars in the context of putative extrasolar analogs. The preferred wavelength ranges are 7-25 ?m in the mid-IR and 0.5 to ~1.1 ?m in the visible to near-IR. Detection of O2 or its photolytic product O3 merits highest priority. Liquid H2O is not a bioindicator, but it is considered essential to life. Substantial CO2 indicates an atmosphere and oxidation state typical of a terrestrial planet. Abundant CH4 might require a biological source, yet abundant CH4 also can arise from a crust and upper mantle more reduced than that of Earth. The range of characteristics of extrasolar rocky planets might far exceed that of the Solar System. Planetary size and mass are very important indicators of habitability and can be estimated in the mid-IR and potentially also in the visible to near-IR. Additional spectroscopic features merit study, for example, features created by other biosignature compounds in the atmosphere or on the surface and features due to Rayleigh scattering. In summary, we find that both the mid-IR and the visible to near-IR wavelength ranges offer valuable information regarding biosignatures and planetary properties; therefore both merit serious scientific consideration for TPF and Darwin.

Des Marais, David J.; Harwit, Martin O.; Jucks, Kenneth W.; Kasting, James F.; Lin, Douglas N. C.; Lunine, Jonathan I.; Schneider, Jean; Seager, Sara; Traub, Wesley A.; Woolf, Neville J.

2002-06-01

22

TAU: 1D radiative transfer code for transmission spectroscopy of extrasolar planet atmospheres  

NASA Astrophysics Data System (ADS)

TAU is a 1D line-by-line radiative transfer code for modeling transmission spectra of close-in extrasolar planets. The code calculates the optical path through the planetary atmosphere of the radiation from the host star and quantifies the absorption due to the modeled composition in a transmission spectrum of transit depth as a function of wavelength. The code is written in C++ and is parallelized using OpenMP.

Hollis, M. D. J.; Tessenyi, M.; Tinetti, G.

2013-05-01

23

Probing extrasolar planet atmospheres through transits  

Microsoft Academic Search

A revolution is taking place in the research of extra-solar planets with the discovery of the first exoplanets only a decade ago to the more than 100 systems known to date. Almost all of these extrasolar planets have been discovered using the radial velocity technique. Unfortunately, this limits the amount of information which can be obtain from these systems, with

Ignas Snellen

2005-01-01

24

Snowball Planets: A Possible Type of Water-Rich Terrestrial Planet in Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

Existence of liquid water on the planetary surface is essential for life. However, terrestrial planets with abundant water have multiple climate modes, including an ice-free, a partially ice-covered, and a globally ice- covered state, even when the incident flux from the central star and the abundance of greenhouse gasses in the atmosphere are the same. This multiplicity of climate mode is derived from large difference in the albedo of ice and water. Recent geological studies have revealed that the Earth experienced global glaciations ("snowball Earth" events) in its history. In the snowball glaciations, liquid water is thought to have existed under the ice shell because of geothermal heat flow from the Earth"fs interior. By analogy with the snowball glaciations, I discuss the conditions for an extrasolar terrestrial planet which is covered with ice but has an internal ocean for the timescale of planetary evolution owing to geothermal heat flow from the planetary interior. I show that liquid water can exist if the planetary mass and the water abundance are comparable to the Earth, although a planet with a mass of <0.4 Me (Me is the Earth's mass) would not be able to maintain the internal ocean. Liquid water would be absolutely stable for a planet with a mass of >4 Me (i.e., super- Earth), irrespective of planetary orbit and luminosity of the central star. It is therefore implied that super-Earth inevitably have liquid water either on its surface (for the ice-freee or partially ice-covered modes) or beneath the ice (for the globally ice-covered mode). Searches for terrestrial planets in extrasolar planetary systems should consider such a "snowball planet", which is a possible type of water-rich terrestrial planet other than an Earth-like "ocean planet". Because a snowball planet is much brighter than (more than twice) an ocean planet with the same size, it would be a good target for the astronomical observation in the future.

Tajika, E.

2008-12-01

25

Hypersonic waveriders for planetary atmospheres  

NASA Astrophysics Data System (ADS)

The concept of a hypersonic waverider for application in foreign planetary atmospheres is explored, particularly in regard to aero-assist for space vehicle trajectory modification. The overall concept of hypersonic waveriders is discussed in tutorial fashion. A review of past work is given, and the role of a new family of waveriders - the viscous optimized waveriders generated at the University of Maryland - is highlighted. The mechanics of trajectory modification by aerodynamic vehicles with high lift-to-drag ratios in planetary atmospheres is explored. Actual hypersonic waverider designs for Mars and Venus atmospheres are presented. These are the first waveriders ever presented for foreign planetary atmospheres. Moreover, they exhibit very high lift-to-drag ratios, as high as 15 in the Venus atmosphere. These results graphically demonstrate that a hypersonic waverider is a viable candidate for aero-assist maneuvers in foreign planetary atmospheres.

Anderson, John D., Jr.; Lewis, Mark J.; Kothari, Ajay P.; Corda, Stephen

1990-01-01

26

Terrestrial planet formation in extra-solar planetary systems  

NASA Astrophysics Data System (ADS)

Terrestrial planets form in a series of dynamical steps from the solid component of circumstellar disks. First, km-sized planetesimals form likely via a combination of sticky collisions, turbulent concentration of solids, and gravitational collapse from micron-sized dust grains in the thin disk midplane. Second, planetesimals coalesce to form Moon- to Mars-sized protoplanets, also called “planetary embryos”. Finally, full-sized terrestrial planets accrete from protoplanets and planetesimals. This final stage of accretion lasts about 10-100 Myr and is strongly affected by gravitational perturbations from any gas giant planets, which are constrained to form more quickly, during the 1-10 Myr lifetime of the gaseous component of the disk. It is during this final stage that the bulk compositions and volatile (e.g., water) contents of terrestrial planets are set, depending on their feeding zones and the amount of radial mixing that occurs. The main factors that influence terrestrial planet formation are the mass and surface density profile of the disk, and the perturbations from giant planets and binary companions if they exist. Simple accretion models predicts that low-mass stars should form small, dry planets in their habitable zones. The migration of a giant planet through a disk of rocky bodies does not completely impede terrestrial planet growth. Rather, “hot Jupiter” systems are likely to also contain exterior, very water-rich Earth-like planets, and also “hot Earths”, very close-in rocky planets. Roughly one third of the known systems of extra-solar (giant) planets could allow a terrestrial planet to form in the habitable zone.

Raymond, Sean N.

2008-05-01

27

Radiation Transfer Through an Extended Planetary Atmosphere  

NASA Astrophysics Data System (ADS)

A transit of a planet in front of its parent star nowadays provides the best possibility to gain detailed insight into extrasolar planet atmosphere. Experiences with the difficult detection of possible features of an extended atmosphere (``exosphere'') indicate the need for theoretical guidance through the wealth of weak absorption lines on top of the parent star spectrum. The work presented here is a first attempt to discuss molecular features possibly observable during an extrasolar planetary transit event. Utilizing the HITRAN (e.g. CO2, O2, CH4, NH4, OH) and the Copenhagen (e.g. CO, TiO, SiO, H2O) data base for 25 molecular species as well as continuum cross sections, a radiative transfer along characteristic rays through a simplified exosphere has been calculated. The evaluation of the optical depth shows, that the planet atmosphere is optically thick in inner adiabatic layers. The evaluation of number densities and cross sections in the optically thin upper regions identified six molecules (CO, O2, SiO, TiO, CO2, OH) as the main opacity contributers of the planetary gas. The line dominated part of the composed planet-star spectrum is mainly influenced by the four molecules O2, CO2, TiO, and SiO in the range ? 0.25 ldots 1 ?m. The absorption bands in this range can be assigned to these molecules. In the range from 1 to 10 ?m all six above mentioned molecules show more or less strong and significant absorption bands.

Schnabel, K.; Helling, Ch.; Woitke, P.; Sedlmayr, E.

28

Planetary WRF: A multiscale, planetary, atmospheric model  

NASA Astrophysics Data System (ADS)

The NCAR terrestrial Weather Research and Forecast WRF atmospheric model has been converted into a global planetary model Planetary WRF is the first truly multi-scale numerical model having the ability to run on scales from meters to global and with 2-way interactivity The model is fully compressible has 3D Coriolis and curvature treatment and has hydrostatic and non-hydrostatic options The model has initially been converted for use on Mars and Titan with future applications to other planets planned The dynamical core has been validated using the Held and Suarez 1994 generalized test and comparison of 1D and 3D Martian versions with existing models The conversion process and preliminary results at a variety of scales including validation will be presented

Toigo, A.; Richardson, M.; Newman, C.; Mischna, M.; Inada, A.

29

Equations for the analysis of the light curves of extra-solar planetary transits  

Microsoft Academic Search

Easy to use analytical formulae are presented for the computation the of light curves of extra-solar planetary transits. The equations are a function of the fractional radii of the planet and the parent star, the inclination of the orbit, and the limb-darkening coefficients of the star. Light curves can be solved for these parameters depending on the precision of the

A. Giménez

2006-01-01

30

The Prospects for Earth-Like Planets within Known Extrasolar Planetary Systems  

Microsoft Academic Search

We consider the possible existence of habitable Earth-like planets in four recently discovered extrasolar planetary systems. Such prospective planets must have orbits that are (1) dynamically stable, and (2) allow for surface temperatures compatible with liquid water. We find that three of the four new systems (51 Peg, rho^1 Cnc, and 47 UMa) are easily capable of supporting habitable planets.

Curtis S. Gehman; Fred C. Adams; Gregory Laughlin

1996-01-01

31

The Orbits of Terrestrial Planets in the Habitable Zones of Known Extrasolar Planetary Systems  

Microsoft Academic Search

We show that terrestrial planets could survive in variously restricted regions of the habitable zones of 47 Ursae Majoris, ? Eridani, and ? Coronae Borealis, but nowhere in the habitable zones of Gliese 876 and ? Andromedae. The first three systems between them are representative of a large proportion of the 90 or so extrasolar planetary systems discovered by mid-2002,

Barrie W Jones; P. Nick Sleep

32

The Orbits of Terrestrial Planets in the Habitable Zones of Known Extrasolar Planetary Systems  

Microsoft Academic Search

We show that terrestrial planets could survive in variously restricted regions of the habitable zones of 47 Ursae Majoris, Epsilon Eridani, and Rho Coronae Borealis, but nowhere in the habitable zones of Gliese 876 and Upsilon Andromedae. The first three systems between them are representative of a large proportion of the 90 or so extrasolar planetary systems discovered by mid-2002,

B. W. Jones; P. N. Sleep

2003-01-01

33

Understanding the Atmospheres of Transiting Extrasolar Planets  

Microsoft Academic Search

Transiting planets, those which just happen to lie in near edge-on orbits and pass periodically between Earth and their parent star, are quite rare. Of those discovered so far, only a few have been found within 100 pc. These objects are critically important for understanding extrasolar planets, given the variety of observational approaches that are made available by their transiting

Travis Barman

2007-01-01

34

PLANETARY CORONAE AND ATMOSPHERIC EVAPORATION  

Microsoft Academic Search

9 ; : = 7 > : ; = : 7 8 8 4 planetary ; atmosphere where collisions are rare and where the controlling factors are ; gravitational attraction and thermal energy conducted from below. The classic ; assumption of a sharply defined critical level above which the atmosphere is ; completely free of collisions is used initially. Throughout,

J CHAMBERLAIN

1963-01-01

35

TAU: A 1D radiative transfer code for transmission spectroscopy of extrasolar planet atmospheres  

NASA Astrophysics Data System (ADS)

The TAU code is a 1D line-by-line radiative transfer code, which is generally applicable for modelling transmission spectra of close-in extrasolar planets. The inputs are the assumed pressure–temperature profile of the planetary atmosphere, the continuum absorption coefficients and the absorption cross-sections for the trace molecular absorbers present in the model, as well as the fundamental system parameters taken from the published literature. The program then calculates the optical path through the planetary atmosphere of the radiation from the host star, and quantifies the absorption due to the modelled composition in a transmission spectrum of transit depth as a function of wavelength. The code is written in C++, parallelised using OpenMP, and is available for public download and use from http://www.ucl.ac.uk/exoplanets/.

Hollis, M. D. J.; Tessenyi, M.; Tinetti, G.

2013-10-01

36

Studies of Tenuous Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

In order to understand the physical and chemical processes which produce the dust comae in comets and various tenuous planetary and planetary satellite (upper) atmospheres through interactions with their particle, field, and radiation environs, it is necessary analyze remotely observed and spacecraft data with physically meaningful models. With this in mind, we have undertaken a coupled program of theoretical modeling and complementary data analysis regarding the distribution of dust in comets, and the global distributions of neutral and ionized gases in, and escape from, tenuous planetary atmospheres. The nature of the atmospheres and ionospheres of Jupiter's natural satellites Io and Europa and their interactions with their surrounding radiation, and particles and fields environments is a very active and timely field of study. Various kinds of work, depending on different regime-dependent approaches have been adopted in recent years, with the hope of understanding the basic global structure of the atmospheres, and their interactions with solar radiation and with the Jovian plasma torus environment. Io's interaction with Jupiter's corotating plasma torus has been studied for over 25 years. Io has a neutral atmosphere which is probably locally thick but rather uneven across its surface. (See Lellouch 1996 for an excellent review of pre-1996 literature.) The ultimate source for atmospheric gases appears to be the numerous active volcanoes on the surface, moderated by condensation and sublimation from the surface. The energetic particle environment near Io is responsible for the balance of the plasma heating, Joule heating, ionization, and surface d responsible I an atmospheric sputtering, and in some form drives the escape of the neutral atmosphere. The tenuous atmosphere portion of our work involves developing and applying coupled three-dimensional magnetohydrodynamic (MHD) and fully kinetic ion and neutral Direct Simulation Monte Carlo models to describe the upper atmospheres and ionosphere of Jupiter's planetary satellites and their interaction with the corotating plasma torus. This is first being done for Jupiter's moon Io and then for Europa.

Combi, Michael R.

1997-01-01

37

Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres  

Microsoft Academic Search

Atmospheres of transiting extrasolar giant planets (EGPs) such as HD 209458b must impose features on the spectra of their parent stars during transits; these features contain information about the physical conditions and chemical composition of the atmospheres. The most convenient observational index showing these features is the ``spectrum ratio'' R(lambda), defined as the wavelength-dependent ratio of spectra taken in and

Timothy M. Brown

2001-01-01

38

Actions of Magnetospheres on Planetary Atmospheres.  

National Technical Information Service (NTIS)

The review summarizes the observed characteristics of the interactions of the magnetospheres on the planetary atmospheres of Earth, Mars, Jupiter, Saturn and Uranus. The planetary atmospheres bring the ionospheres to corotation by frictional force. Deviat...

B. Hultqvist

1989-01-01

39

Hydrodynamic escape from planetary atmospheres  

Microsoft Academic Search

Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Due to the existence of a singularity point near the transonic point, it is difficult to find transonic steady state solutions by solving the time-independent hydrodynamic equations. In addition to that, most previous works assume that all energy driving the escape flow is deposited in one

Feng Tian

2005-01-01

40

Light scattering in planetary atmospheres  

Microsoft Academic Search

This paper reviews scattering theory required for analysis of light reflected by planetary atmospheres. Section 1 defines the radiative quantities which are observed. Section 2 demonstrates the dependence of single-scattered radiation on the physical properties of the scatterers. Section 3 describes several methods to compute the effects of multiple scattering on the reflected light.

James E. Hansen; Larry D. Travis

1974-01-01

41

Hypersonic waveriders for planetary atmospheres  

Microsoft Academic Search

The concept of a hypersonic waverider for application in foreign planetary atmospheres is explored, particularly in regard to aero-assist for space vehicle trajectory modification. The overall concept of hypersonic waveriders is discussed in tutorial fashion. A review of past work is given, and the role of a new family of waveriders - the viscous optimized waveriders generated at the University

John D. Anderson Jr.; Mark J. Lewis; Ajay P. Kothari; Stephen Corda

1990-01-01

42

Sprites in other planetary atmospheres  

NASA Astrophysics Data System (ADS)

Lightning have been detected in clouds on other planets either by direct imaging of the optical emissions from flashes emanating through the atmosphere or else by remote sensing of electromagnetic signals such as sferics or whistlers guided by the planet's magnetosphere. While the intensity of the electrical activity on Venus may be still inconclusive, there is little doubt, based on the Voyager, Galileo and Cassini missions, that lightning are prevalent on Jupiter and Saturn, and that their total power is much stronger than on Earth (Desch et al., 2002; Gurnett et al., 2005). Sprites are a type of a transient luminous emission which accompanies powerful lightning flashes (Lyons et al. 2001). They are caused the quasi-electrostatic electric field between the charged cloud top and the planetary ionosphere. They can take weird and magnificent shapes resembling jelly-fish, carrot heads, pearls or columns. On Earth, they emit in red and blue wavelengths, mostly from molecular Nitrogen species, and span a vertical range between 50 and 90 km. The emission spectra of sprites, their height and occurrence frequency reflect the properties of the planetary atmosphere and are directly related to the intensity of the parent lightning. We present results of theoretical calculations of the expected emissions in sprites, occurring above thunderstorms in the CO2 atmosphere of Venus and the Hydrogen-Helium atmospheres of Jupiter and Saturn. Detection methodology of sprites in planetary atmospheres by orbiting spacecraft will be discussed

Yair, Y.; Yaniv, R.

43

Detection of an Extrasolar Planet Atmosphere  

Microsoft Academic Search

We report high precision spectrophotometric observations of four planetary\\u000atransits of HD 209458, in the region of the sodium resonance doublet at 589.3\\u000anm. We find that the photometric dimming during transit in a bandpass centered\\u000aon the sodium feature is deeper by (2.32 +\\/- 0.57) x 10^{-4} relative to\\u000asimultaneous observations of the transit in adjacent bands. We interpret

David Charbonneau; Timothy M. Brown; Robert W. Noyes; Ronald L. Gilliland

2001-01-01

44

Radial Velocity Detection of Extra-Solar Planetary Systems.  

National Technical Information Service (NTIS)

This NASA Origins Program grant supported four closely related research programs at The University of Texas at Austin: (1) The McDonald Observatory Planetary Search (MOPS) Program, using the McDonald Observatory 2.7m Harlan Smith telescope and its 2dcoud6...

W. D. Cochran

2004-01-01

45

Radial Velocity Detection of Extra-Solar Planetary Systems.  

National Technical Information Service (NTIS)

The McDonald Observatory Planetary Search (MOPS) was designed to search for Jovian-mass planets in orbit around solar-type stars by making high-precision measurements of the Radial Velocity (RV) of a star, to attempt to detect the reflex orbital motion of...

W. D. Cochran

1998-01-01

46

Resonant Periodic Motion and the Stability of Extrasolar Planetary Systems  

Microsoft Academic Search

Families of nearly circular periodic orbits of the planetary type are studied, close to the 3\\/1 mean motion resonance of the two planets, considered both with finite masses. Large regions of instability appear, depending on the total mass of the planets and on the ratio of their masses. Also, families of resonant periodic orbits at the 2\\/1 resonance have been

John D. Hadjidemetriou

2002-01-01

47

Introduction - Solar and ExtraSolar Planetary Systems  

Microsoft Academic Search

Over the last decade, there have been many exciting advances in all fields relating to our understanding of planetary systems. There has been a significant increase in our understanding of the general process of star formation, leading to an expectation that matter will be captured in a flattened envelope or nebula surrounding the young Sun. Theoretical models had predicted this

Iwan P. Williams

2001-01-01

48

Introduction — Solar and ExtraSolar Planetary Systems  

Microsoft Academic Search

Over the last decade, there have been many exciting advances in all fields relating to our understanding of planetary systems.\\u000a There has been a significant increase in our understanding of the general process of star formation, leading to an expectation\\u000a that matter will be captured in a flattened envelope or nebula surrounding the young Sun. Theoretical models had predicted\\u000a this

Iwan Williams

49

An extrasolar planetary system with three Neptune-mass planets.  

PubMed

Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called 'hot Neptunes' or 'super-Earths' around Sun-like stars. These planets have masses 5-20 times larger than the Earth and are mainly found on close-in orbits with periods of 2-15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun-Earth distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star. PMID:16710412

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

2006-05-18

50

Modelling the formation of atmospheric dust in brown dwarfs and planetary atmospheres.  

PubMed

Atmospheric dust from volcanoes, sand storms and biogenic products provides condensation seeds for water cloud formation on the Earth. Extrasolar planetary objects such as brown dwarfs and extrasolar giant planets have no comparable sources of condensation seeds. Hence, understanding cloud formation and further its implications for the climate requires a modelling effort that includes the treatment of seed formation (nucleation), growth and evaporation, in addition to rain-out, mixing and gas-phase depletion. This paper discusses nucleation in the ultra-cool atmospheres of brown dwarfs and extrasolar giant planets whose chemical gas-phase composition differs largely from the terrestrial atmosphere. A kinetic model for atmospheric dust formation is described, which, in recent work, has become part of a cloud-formation model. For the first time, diffusive replenishment of the upper atmosphere is introduced as a source term into our model equations. This paper further aims to show how experimental and computational chemistry work links into our dust-formation model, which is driven by applications in extraterrestrial environments. PMID:23734048

Helling, Christiane; Fomins, Aleksejs

2013-06-03

51

The Orbits of Terrestrial Planets in the Habitable Zones of Known Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

We show that terrestrial planets could survive in variously restricted regions of the habitable zones of 47 Ursae Majoris, Epsilon Eridani, and Rho Coronae Borealis, but nowhere in the habitable zones of Gliese 876 and Upsilon Andromedae. The first three systems between them are representative of a large proportion of the 90 or so extrasolar planetary systems discovered by mid-2002, and thus there are many known systems worth searching for terrestrial planets in habitable zones. We reach our conclusions by launching putative Earth-mass planets in various orbits and following their fate with a mixed-variable symplectic integrator.

Jones, B. W.; Sleep, P. N.

52

Planetary Atmospheres at High Resolution  

NASA Astrophysics Data System (ADS)

The long millimeter through submillimeter bands are particularly well suited for studying the wide variety of planetary atmospheres in our solar system. Temperatures ranging from a few 10s to hundreds of degrees, coupled with typically high densities (relative to the ISM) mean that thermal ‘continuum’ emission can be strong and molecular rotational transitions can be well-populated. Large bodies (Jovian and terrestrial planets) can be reasonably well studied by current interferometers such as the Submillimeter Array, IRAM Plateau de Bure Interferometer, and Combined Array for Research in Millimeter-wave Astronomy, yet many smaller bodies with atmospheres can only be crudely studied, primarily due to lack of sensitivity on baselines long enough to well resolve the object. Newly powerful interferometers such as the Atacama Large Millimeter/Submillimeter Array will usher in a new era of planetary atmospheric exploration. The vast sensitivity and spatial resolution of these arrays will increase our ability to image all bodies with extremely fine fidelity (due to the large number of antennas), and for study of smaller objects by resolving their disks into many pixels while providing the sensitivity necessary to detect narrow and/or weak line emission. New science topics will range from detailed mapping of HDO, ClO, and sulfur species in the mesosphere of Venus and PH3 and H2S in the upper tropospheres of the gas and ice giants, high SNR mapping of winds on Mars, Neptune and Titan, down to spectroscopic imaging of volcanic eruptions within the tenuous atmosphere on Io, resolved imaging of CO and other species in the atmosphere of Pluto, and even potentially detection of gases within the plumes of Enceladus.

Gurwell, M.; Butler, B.; Moullet, A.

2013-10-01

53

Isotopic ratios in planetary atmospheres.  

PubMed

Recent progress on measurements of isotopic ratios in planetary or satellite atmospheres include measurements of the D/H ratio in the methane of Uranus, Neptune and Titan and in the water of Mars and Venus. Implications of these measurements on our understanding of the formation and evolution of the planets and satellite are discussed. Our current knowledge of the carbon, nitrogen and oxygen isotopic ratios in the atmospheres of these planets, as well as on Jupiter and Saturn, is also reviewed. We finally show what progress can be expected in the very near future due to some new ground-based instrumentation particularly well suited to such studies, and to forthcoming space missions. PMID:11539257

de Bergh, C

1995-03-01

54

Symmetric and asymmetric librations in extrasolar planetary systems: a global view  

NASA Astrophysics Data System (ADS)

We present a global view of the resonant structure of the phase space of a planetary system with two planets, moving in the same plane, as obtained from the set of the families of periodic orbits. An important tool to understand the topology of the phase space is to determine the position and the stability character of the families of periodic orbits. The region of the phase space close to a stable periodic orbit corresponds to stable, quasi periodic librations. In these regions it is possible for an extrasolar planetary system to exist, or to be trapped following a migration process due to dissipative forces. The mean motion resonances are associated with periodic orbits in a rotating frame, which means that the relative configuration is repeated in space. We start the study with the family of symmetric periodic orbits with nearly circular orbits of the two planets. Along this family the ratio of the periods of the two planets varies, and passes through rational values, which correspond to resonances. At these resonant points we have bifurcations of families of resonant elliptic periodic orbits. There are three topologically different resonances: (1) the resonances (n + 1):n, (2:1, 3:2, ...), (2) the resonances (2n + 1):(2n-1), (3:1, 5:3, ...) and (3) all other resonances. The topology at each one of the above three types of resonances is studied, for different values of the sum and of the ratio of the planetary masses. Both symmetric and asymmetric resonant elliptic periodic orbits exist. In general, the symmetric elliptic families bifurcate from the circular family, and the asymmetric elliptic families bifurcate from the symmetric elliptic families. The results are compared with the position of some observed extrasolar planetary systems. In some cases (e.g., Gliese 876) the observed system lies, with a very good accuracy, on the stable part of a family of resonant periodic orbits.

Hadjidemetriou, John D.

2006-05-01

55

Infrared remote sensing of planetary atmospheres  

Microsoft Academic Search

Infrared remote sensing is a powerful tool for studying the chemical composition and the thermal structure of planetary atmospheres. Infrared spectra, in particular, are used to derive molecular abundances and to infer elemental and isotopic ratios, which allow to constrain theoretical models of the formation and early evolution of the solar system, as well as the history of planetary atmospheres.

Thérèse Encrenaz

2000-01-01

56

The HARPS search for southern extra-solar planets. XXVII. Seven new planetary systems  

NASA Astrophysics Data System (ADS)

We are conducting a planet search survey with HARPS since seven years. The volume-limited stellar sample includes all F2 to M0 main-sequence stars within 57.5 pc, where extrasolar planetary signatures are systematically searched for with the radial-velocity technics. In this paper, we report the discovery of new substellar companions of seven main-sequence stars and one giant star, detected through multiple Doppler measurements with the instrument HARPS installed on the ESO 3.6 m telescope, La Silla, Chile. These extrasolar planets orbit the stars HD 1690, HD 25171, HD 33473A, HD 89839, HD 113538, HD 167677, and HD 217786. The already-published giant planet around HD 72659 is also analysed here, and its elements are better determined by the addition of HARPS and Keck data. The other discoveries are giant planets in distant orbits, ranging from 0.3 to 29 MJup in mass and between 0.7 and 10 years in orbital period. The low metallicity of most of these new planet-hosting stars reinforces the current trend for long-distance planets around metal-poor stars. Long-term radial-velocity surveys allow probing the outskirts of extrasolar planetary systems, although confidence in the solution may be low until more than one orbital period is fully covered by the observations. For many systems discussed in this paper, longer baselines are necessary to refine the radial-velocity fit and derive planetary parameters. The radial-velocity time series of stars BD -114672 and HIP 21934 are also analysed and their behaviour interpreted in terms of the activity cycle of the star, rather than long-period planetary companions. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory under programme IDs 072.C-0488(E) and 085.C-0019.RV data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/527/A63

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

2011-03-01

57

Mean Motion Resonances in Extrasolar Planetary Systems With Turbulence, Interactions, and Damping  

NASA Astrophysics Data System (ADS)

This paper continues our previous exploration of the effects of turbulence on mean motion resonances in extrasolar planetary systems. Turbulence is expected to be present in the circumstellar disks that give rise to planets, and these fluctuations act to compromise resonant configurations. This paper extends previous work by considering how interactions between the planets and possible damping effects imposed by the disk affect the outcomes. These physical processes are studied using three related approaches: direct numerical integrations of the three-body problem with additional forcing due to turbulence, model equations that reduce the problem to stochastically driven oscillators, and Fokker-Planck equations that describe the time evolution of an ensemble of such systems. With this combined approach, we elucidate the basic physics of how turbulence can remove extrasolar planetary systems from mean motion resonance. As expected, systems with sufficiently large damping (dissipation) can maintain resonance, in spite of turbulent forcing. In the absence of strong damping, ensembles of these systems exhibit two regimes of behavior, where the fraction of the bound states decreases as a power law or as an exponential. Both types of behavior can be understood through the model developed herein. For systems that have weak interactions between the planets, the model reduces to that of a stochastic pendulum, and the fraction of bound states decreases as a power law P b vprop t -1/2. For highly interactive systems, however, the dynamics are more complicated and the fraction of bound states decreases exponentially with time. We show how planetary interactions lead to drift terms in the Fokker-Planck equation and account for this exponential behavior. In addition to clarifying the physical processes involved, this paper strengthens our original finding that turbulence implies that mean motion resonances should be rare.

Lecoanet, Daniel; Adams, Fred C.; Bloch, Anthony M.

2009-02-01

58

New in the physics of planetary atmosphere  

Microsoft Academic Search

We present here an overview of the results of Russian investigations of planetary atmospheres in 2003–2006 prepared by the\\u000a Commission on Planetary Atmospheres of the National Geophysical Committee for the National Report on Meteorology and Atmospheric\\u000a Sciences to the 24th General Assembly of the International Union of Geodesy and Geophysics (Perugia, June 2–13, 2007).

O. I. Korablev; L. V. Zasova; A. A. Fedorova; A. V. Rodin; N. I. Ignatiev; T. K. Breus; M. N. Izakov; B. S. Maiorov; A. A. Krivolutsky; E. V. Petrova; A. Yu. Ivanov; A. Yu. Trokhimovskii

2009-01-01

59

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

SciTech Connect

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{sub +} from 10 to 20 AU. For large planet masses (M {approx}> M{sub 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 {approx}< 3 AU) is consistent with isolated planet-planet scattering. We explain the observed mass dependence-which is in the opposite sense from that predicted by the simplest scattering models-as a consequence of strong correlations between planet masses in the same system. At somewhat larger radii, initial planetary mass correlations and disk effects can yield similar modest changes to the eccentricity distribution. Nonetheless, strong damping of eccentricity for low-mass planets at large radii appears to be a secure signature of the dynamical influence of disks. Radial velocity measurements capable of detecting planets with K {approx} 5 m s{sup -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 {approx} 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 planets in outer planetary systems.

Raymond, Sean N. [Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France); Armitage, Philip J. [JILA, University of Colorado, Boulder, CO 80309 (United States); Gorelick, Noel, E-mail: pja@jilau1.colorado.ed [Google, Inc., 1600 Amphitheatre Parkway, Mountain View, CA 94043 (United States)

2010-03-10

60

Long-Period Objects in the Extrasolar Planetary Systems 47 Ursae Majoris and 14 Herculis  

NASA Astrophysics Data System (ADS)

The possible existence of additional long-period planetary-mass objects in the extrasolar planetary systems 47 UMa and 14 Her is investigated. We combine all available radial velocity data on these stars, spanning up to 18 yr. For the 47 UMa system, we show that while a second planet improves the fit to all available data, there is still substantial ambiguity as to the orbital parameters of the proposed planetary companion 47 UMa c. We also present new observations that clearly support a long-period companion in the 14 Her system. With a period of 6906+/-70 days, 14 Her c may be in a 4:1 resonance with the inner planet. We also present revised orbital solutions for seven previously known planets, incorporating recent additional data obtained with the 2.7 m Harlan J. Smith Telescope at McDonald Observatory. Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Wittenmyer, Robert A.; Endl, Michael; Cochran, William D.

2007-01-01

61

Brightness and Polarization of Extrasolar Planet Oceans and Atmospheres  

NASA Astrophysics Data System (ADS)

We have developed a model to determine if orbital variation in reflected starlight from extrasolar planets could eventually be used to detect surface oceans on Earth-like planets. We then used this model to simulate the orbital variation in brightness and polarization of light scattered by different types of exoplanets, including ocean planets. The hypothetical exoplanets we modeled are Earth-sized planets orbiting a Sun-like star at 1 AU; we assume orbits that are edge-on to our line of sight, because this geometry maximizes the water signatures we seek. The modeled planets have Earth-like atmospheres (including Rayleigh scattering, absorption, aerosols, and clouds) and surfaces that are either ocean-covered or diffusely scattering (similar to Earth deserts). We confirm earlier findings that ocean planets with thin atmospheres exhibit a brightness peak before and after transit (near orbital longitude = 30 degrees), and show a strong polarization peak near orbital longitude = 74 degrees. However, we also show that, on an exoplanet with Earth-like Rayleigh scattering, these signatures are almost completely hidden by the atmosphere when observing in the waveband 0.5 to 1.0 um. At longer wavelengths out to 2.3 um, Rayleigh scattering can be essentially eliminated, but aerosol scattering tends to obscure both the polarization signature and the brightness peak, unless aerosols are very thin by Earth standards. Clouds and wind-driven waves on an ocean surface can also mask water signatures, and atmospheric scattering on dry planets can create a polarization signature similar to that from an ocean planet. In summary, our model shows that detecting a water ocean on an Earth-like planet using polarized and unpolarized glint from the water surface may be more difficult than expected. However polarization adds another dimension which can be used, in combination with variations in orbital brightness and polarization, to seek oceans, atmospheric water aerosols, and water clouds on extrasolar planets. Additionally, the presence and direction of the polarization vector could be used to determine if an observed object is a planet or a background stair, and constrain the planet's orbital inclination.

Zugger, M.; Kasting, J. F.; Williams, D.; Kane, T. J.; Philbrick, C. R.

2011-12-01

62

Spectral Signatures of Photosynthesis. II. Coevolution with Other Stars And The Atmosphere on Extrasolar Worlds  

NASA Astrophysics Data System (ADS)

As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take previously simulated planetary atmospheric compositions for Earth-like planets around observed F2V and K2V, modeled M1V and M5V stars, and around the active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as well as very low O2 content in case anoxygenic photosynthesis dominates. With a line-by-line radiative transfer model, we calculate the incident spectral photon flux densities at the surface of the planet and under water. We identify bands of available photosynthetically relevant radiation and find that photosynthetic pigments on planets around F2V stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in the near-infrared, in bands at 0.93-1.1 ?m, 1.1-1.4 ?m, 1.5-1.8 ? m, and 1.8-2.5 ?m. However, underwater organisms will be restricted to wavelengths shorter than 1.4 ?m and more likely below 1.1 ?m. M star planets without oxygenic photosynthesis will have photon fluxes above 1.6 ?m curtailed by methane. Longer-wavelength, multi-photo-system series would reduce the quantum yield but could allow for oxygenic photosystems at longer wavelengths. A wavelength of 1.1 ?m is a possible upper cutoff for electronic transiprotions versus only vibrational energy; however, this cutoff is not strict, since such energetics depend on molecular configuration. M star planets could be a half to a tenth as productive as Earth in the visible, but exceed Earth if useful photons extend to 1.1 ?m for anoxygenic photosynthesis. Under water, organisms would still be able to survive ultraviolet flares from young M stars and acquire adequate light for growth. Key Words: Photosynthesis-Astrobiology - Photosynthetic pigments - Oxygenic photosynthesis - Anoxygenic photosynthesis - Atmospheric photochemistry - F stars-G stars - Sun - K stars - M stars - AD Leo - Atmospheric oxygen - Atmospheric radiative transfer - Chlorophyll - Bacteriochlorophyll - Photosystems - Radiation spectrum - Photosynthetically active radiation - Light harvesting - Modeling - Extrasolar planets - Earth like planets - Virtual Planetary Laboratory - Biosignatures. Astrobiology 7(1), 252 - 274.

Kiang, Nancy Y.; Segura, Antígona; Tinetti, Giovanna; Govindjee; Blankenship, Robert E.; Cohen, Martin; Siefert, Janet; Crisp, David; Meadows, Victoria S.

2007-02-01

63

ISO observations of planetary atmospheres  

NASA Astrophysics Data System (ADS)

The Infrared Space Observatory (ISO) satellite, operated by ESA in 1995-1998, has provided a very significant contribution to our knowledge of planetary atmospheres. The main results of ISO observations of the giant planets and Titan can be summarized as follows: (1) a new determination of the D/H ratio; (2) the discovery of an external source of water, and the detection of CO2 in the stratospheres of Saturn, Neptune and Jupiter; (3) the detection of new hydrocarbons in the stratospheres of Saturn (CH3C2H, C4H2, C6H6, CH3), Jupiter (CH3C2H, C6H6) and Neptune (CH3, C2H4); (4) the study of NH3 and PH3 in Jupiter and Saturn, and the determination of 14N/15N in Jupiter; (5) the detection of H2O in the deep troposphere of Saturn; (6) the observation of H3+ in Uranus. ISO spectra of Mars have provided information about the water vapor content and the composition of aerosols.

Encrenaz, Th.

64

Water vapour in the atmosphere of a transiting extrasolar planet.  

PubMed

Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets ('hot Jupiters'). Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution. Here we report an analysis of recent observations of the hot Jupiter HD 189733b (ref. 6) taken during the transit, when the planet passed in front of its parent star. We find that absorption by water vapour is the most likely cause of the wavelength-dependent variations in the effective radius of the planet at the infrared wavelengths 3.6 mum, 5.8 mum (both ref. 7) and 8 mum (ref. 8). The larger effective radius observed at visible wavelengths may arise from either stellar variability or the presence of clouds/hazes. We explain the report of a non-detection of water on HD 189733b (ref. 4) as being a consequence of the nearly isothermal vertical profile of the planet's atmosphere. PMID:17625559

Tinetti, Giovanna; Vidal-Madjar, Alfred; Liang, Mao-Chang; Beaulieu, Jean-Philippe; Yung, Yuk; Carey, Sean; Barber, Robert J; Tennyson, Jonathan; Ribas, Ignasi; Allard, Nicole; Ballester, Gilda E; Sing, David K; Selsis, Franck

2007-07-12

65

Exploring Extra-Solar Planetary Interiors: New Chemistry at Extreme Conditions  

NASA Astrophysics Data System (ADS)

The physical and transport properties of silicate and oxide melts at extreme pressures and temperatures are critical for understanding early planetary evolution and the aftermath of late-stage giant impacts such as that believed to have formed the Moon. Here we report on a suite of laser-driven shock experiments on major mineral phases of significance to the terrestrial mantle and extra-solar rocky planets SiO2, MgO and MgSiO3. Experiments on two polymorphs of SiO2 were used to validate experimental technique and are compared to previous results. We extend Hugoniot equation of state measurements for MgO and MgSiO3 to 6.4 and 9.5 Mbar, respectively, constraining controversial predications for the ultra-high pressure melt curves. Experiments on amorphous and crystalline MgSiO3 starting materials show the first evidence of a liquid-liquid phase transition with a volume reduction of 5-8% near 3.5 Mbar and over a range of temperature of at least 7000 K, suggesting the potential for unexpectedly complex chemistry in silicate liquids. Transport properties are extracted from time-resolved optical reflectivity data and imply that the distinction between silicate and metallic constituents are blurred in deep planetary interiors with potential implications for coupling across the present-day core-mantle boundary.

Spaulding, Dylan

2011-06-01

66

Origin and evolution of planetary atmospheres  

Microsoft Academic Search

This report concerns several research tasks related to the origin and evolution of planetary atmospheres and the large-scale distribution of volatile elements in the Solar System. These tasks and their present status are as follows: (1) we have conducted an analysis of the volatility and condensation behavior of compounds of iron, aluminum, and phosphorus in the atmosphere of Venus in

John S. Lewis

1992-01-01

67

Franklin Lecture: Lightning in Planetary Atmospheres  

Microsoft Academic Search

A broad overview is given of lightning in planetary atmospheres. Searches for lightning using spacecraft-borne instrumentation have now been conducted at almost all of the planets in the solar system, the exceptions being Mercury, which has no appreciable atmosphere, and Pluto which has not yet been visited by a spacecraft. The techniques used include (1) imaging observations to detect optical

D. A. Gurnett

2006-01-01

68

Models of Polarized Light from Oceans and Atmospheres of Earth-like Extrasolar Planets  

Microsoft Academic Search

Specularly reflected light, or glint, from an ocean surface may provide a useful observational tool for studying extrasolar terrestrial planets. Detection of sea-surface glints would differentiate ocean-bearing terrestrial planets, i.e. those similar to Earth, from other terrestrial extrasolar planets. The brightness and degree of polarization of both sea-surface glints and atmospheric Rayleigh scattering are strong functions of the phase angle

P. R. McCullough

2006-01-01

69

Equations for the analysis of the light curves of extra-solar planetary transits  

NASA Astrophysics Data System (ADS)

Easy to use analytical formulae are presented for the computation the of light curves of extra-solar planetary transits. The equations are a function of the fractional radii of the planet and the parent star, the inclination of the orbit, and the limb-darkening coefficients of the star. Light curves can be solved for these parameters depending on the precision of the available observations. When the radial velocity curve is also available, as is normally the case to ensure the nature of the system, the masses, radii, and average density of both the star and the planet can be determined. The equations are valid for any degree of limb darkening, as well as for any type of transit. The cases of eccentric orbits, third light, or a non-zero relative luminosity of the planet can be easily taken into account. The basic assumption is that the projections of both the star and the planet on the plane of the sky are well represented by circular discs. The effects in case this assumption is not valid are also discussed. Practical applications are shown, beginning with the light curve of the photometrically discovered planet OGLE-TR-113, obtained with a ground-based telescope. As a second example, results are shown from the study of the light curve obtained for the transit of the giant planet in HD 209458 with the Hubble Space Telescope. Procedures to get the best fit parameters are briefly discussed.

Giménez, A.

2006-05-01

70

Work on Planetary Atmospheres and Planetary Atmosphere Probes  

NASA Astrophysics Data System (ADS)

A summary final report of work accomplished is presented. Work was performed in the following areas: (1) Galileo Probe science analysis, (2) Galileo probe Atmosphere Structure Instrument, (3) Mars Pathfinder Atmosphere Structure/Meteorology instrument, (4) Mars Pathfinder data analysis, (5) Science Definition for future Mars missions, (6) Viking Lander data analysis, (7) winds in Mars atmosphere Venus atmospheric dynamics, (8) Pioneer Venus Probe data analysis, (9) Pioneer Venus anomaly analysis, (10) Discovery Venus Probe Titan probe instrument design, and (11) laboratory studies of Titan probe impact phenomena. The work has resulted in more than 10 articles published in archive journals, 2 encyclopedia articles, and many working papers. This final report is organized around the four planets on which there was activity, Jupiter, Mars, Venus, and Titan, with a closing section on Miscellaneous Activities. A major objective was to complete the fabrication, test, and evaluation of the atmosphere structure experiment on the Galileo probe, and to receive, analyze and interpret data received from the spacecraft. The instrument was launched on April 14, 1989. Calibration data were taken for all experiment sensors. The data were analyzed, fitted with algorithms, and summarized in a calibration report for use in analyzing and interpreting data returned from Jupiter's atmosphere. The sensors included were the primary science pressure, temperature and acceleration sensors, and the supporting engineering temperature sensors. Computer programs were written to decode the Experiment Data Record and convert the digital numbers to physical quantities, i.e., temperatures, pressures, and accelerations. The project office agreed to obtain telemetry of checkout data from the probe. Work to extend programs written for use on the Pioneer Venus project included: (1) massive heat shield ablation leading to important mass loss during entry; and (2) rapid planet rotation, which introduced terms of motion not needed on Venus. When the Galileo Probe encountered Jupiter, analysis and interpretation of data commenced. The early contributions of the experiment were to define (1) the basic structure of the deep atmosphere, (2) the stability of the atmosphere, (3) the upper atmospheric profiles of density, pressure, and temperature. The next major task in the Galileo Probe project was to refine, verify and extend the analysis of the data. It was the verified, and corrected data, which indicated a dry abiabatic atmosphere within measurement accuracy. Temperature in the thermosphere was measured at 900 K. Participation in the Mars atmospheric research included: (1) work as a team member of the Mars Atmosphere Working Group, (2) contribution to the Mars Exobiology Instrument workshop, (3) asssistance in planning the Mars global network and (4) assitance in planning the Soviet-French Mars mission in 1994. This included a return to the Viking Lander parachute data to refine and improve the definition of winds between 1.5 and 4 kilometer altitude at the two entry sites. The variability of the structure of Mars atmosphere was addressed, which is known to vary with season, latitude, hemisphere and dust loading of the atmosphere. This led to work on the Pathfinder project. The probe had a deployable meteorology mast that had three temperature sensors, and a wind sensor at the tip of the mast. Work on the Titan atmospheric probe was also accomplished. This included developing an experiment proposal to the European Space Agency (ESA), which was not selected. However, as an advisor in the design and preparation of the selected experiment the researcher interacted with scientist on the Huygens Probe Atmosphere Structure Experiment. The researcher also participated in the planning for the Venus Chemical Probe. The science objectives of the probe were to resolve unanswered questions concerning the minor species chemistry of Venus' atmosphere that control cloud formation, greenhouse effectiveness, and the thermal structure. The researcher also reviewed problems with the

Lester, Peter

1999-01-01

71

Planetary WRF: a Multi-Scale, Planetary, Atmospheric Model  

NASA Astrophysics Data System (ADS)

The NCAR terrestrial Weather Research and Forecast (WRF) atmospheric model has been converted into a global, planetary model. Planetary WRF is the first truly multi-scale numerical model having the ability to run on scales from meters to global, and with 2-way interactivity. The model is fully compressible, has 3D Coriolis and curvature treatment and has hydrostatic and non-hydrostatic options. The model has initially been converted for use on Mars and Titan with future applications to other planets planned. The dynamical core has been validated using the Held and Suarez (1994) generalized test, and comparison of 1D and 3D Martian versions with existing models. The conversion process and preliminary results at a variety of scales including validation will be presented.

Toigo, A.; Richardson, M.; Newman, C.

2005-08-01

72

Planetary WRF: a Multi-Scale, Planetary, Atmospheric Model  

NASA Astrophysics Data System (ADS)

The NCAR terrestrial Weather Research and Forecast (WRF) atmospheric model has been converted into a global, planetary model. Planetary WRF is the first truly multi-scale numerical model having the ability to run on scales from meters to global, and with 2-way domain nesting interactivity. The model is fully compressible, has 3D Coriolis and curvature treatment and has hydrostatic and non-hydrostatic options. The model has initially been converted for use on Mars and Titan with future applications to other planets planned. The dynamical core has been validated using the standardized forcing and setup described in Held and Suarez (1994), and comparison of 1D and 3D Martian and 1D Titan versions with existing models. The conversion process and preliminary results at a variety of scales including validation will be presented.

Toigo, A.; Richardson, M. I.; Newman, C. E.

2005-12-01

73

Atmospheric escape, redox evolution, and planetary habitability  

NASA Astrophysics Data System (ADS)

Through the greenhouse effect, the presence and composition of an atmosphere is critical for defining a (conventional) circumstellar habitable zone in terms of planetary surface temperatures suitable for liquid water. Lack of knowledge of planetary atmospheres is likely to frustrate attempts to say with any certainty whether detected terrestrial-sized exoplanets may or may not be habitable. Perhaps an underappreciated role in such considerations is the evolutionary effect of atmospheric escape for determining atmospheric composition or whether an atmosphere exists in the first place. Whether atmospheres exist at all on planets is demonstrably connected to the effect of integrated atmospheric escape. When we observe our own Solar System and transiting exoplanets, the existence of an atmosphere is clearly delineated by a relative vulnerability to thermal escape and impact erosion. The prevalence of thermal escape as a key evolutionary determinant for the presence of planetary atmosphere is shown by a relationship between the relative solar (or stellar) heating and the escape velocity. Those bodies with too much stellar heating and too smaller escape velocity end up devoid of atmospheres. Impact erosion is evident in the relationship between impact velocity and escape velocity. Escape due to impacts is particularly important for understanding the large differences in the atmospheres of giant planet moons, such as Ganymede versus Titan. It is also significant for Mars-sized planets. The oxidation state of atmospheres is important for some theories of the origin of life (where an early reducing atmosphere is helpful for organic synthesis) and the evolution of advanced life (where free molecular oxygen is the best source of high energy metabolism). Surfaces on some relatively small planets and moons are observed to have evolved to an oxidized state, which theory and observation can explain through atmospheric escape. There are several examples in the Solar System where a net escape of hydrogen relative to heavier oxygen is the generally accepted explanation for the present oxidation state: Venus and Mars amongst the planets, and Ganymede, Europa, and Rhea amongst bodies with extremely tenuous atmospheres. We also argue that hydrogen escape was the key factor for oxidizing the Earth and facilitating the increase of photosynthetically-produced oxygen in the Proterozoic atmosphere. Our view about the primacy of hydrogen escape with regard to the Earth's atmospheric oxygenation is perhaps less widely accepted. However, it was inevitable that hydrogen escaped from Earth's early anoxic atmosphere at a significant rate. The result was a very big integrated oxidation consistent with what is observed in the Earth's crust in addition to some export to the mantle. In conclusion, a better understanding of atmospheric escape processes appears critical for understanding the suitability of planets for harboring life from simple to advanced forms.

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

2011-12-01

74

Characterizing extrasolar planets  

NASA Astrophysics Data System (ADS)

Transiting extrasolar planets provide the best current opportunities for characterizing the physical properties of extrasolar planets. In this review, I first describe the geometry of planetary transits, and methods for detecting and refining the observations of such transits. I derive the methods by which transit light curves and radial velocity data can be analyzed to yield estimates of the planetary radius, mass, and orbital parameters. I also show how visible-light and infrared spectroscopy can be valuable tools for understanding the composition, temperature, and dynamics of the atmospheres of transiting planets. Finally, I relate the outcome of a participatory lecture-hall exercise relating to one term in the Drake equation, namely the lifetime of technical civilizations.

Brown, Timothy M.

75

Dynamics and stability of telluric planets within the habitable zone of extrasolar planetary systems. Numerical simulations of test particles within the HD 4208 and HD 70642 systems  

Microsoft Academic Search

Aims: We study gravitational perturbation effects of observed giant extrasolar planets on hypothetical Earth-like planets in the context of the three-body problem. This paper considers a large parameter survey of different orbital configuration of two extrasolar giant planets (HD 70642b and HD 4208b) and compares their dynamical effect on Earth-mass planetary orbits initially located within the respective habitable terrestrial region.

T. C. Hinse; R. Michelsen; U. G. Jørgensen; K. Gozdziewski; S. Mikkola

2008-01-01

76

Cryptic photosynthesis--extrasolar planetary oxygen without a surface biological signature.  

PubMed

On Earth, photosynthetic organisms are responsible for the production of virtually all the oxygen in the atmosphere. On land, vegetation reflects in the visible and leads to a "red edge," which developed about 450 million years ago on Earth and has been proposed as a biosignature for life on extrasolar planets. However, in many regions on Earth, particularly where surface conditions are extreme--in hot and cold deserts, for example--photosynthetic organisms can be driven into and under substrates where light is still sufficient for photosynthesis. These communities exhibit no detectable surface spectral signature to indicate life. The same is true of the assemblages of photosynthetic organisms at more than a few meters' depth in water bodies. These communities are widespread and dominate local photosynthetic productivity. We review known cryptic photosynthetic communities and their productivity. We have linked geomicrobiology with observational astronomy by calculating the disk-averaged spectra of cryptic habitats and identifying detectable features on an exoplanet dominated by such a biota. The hypothetical cryptic photosynthesis worlds discussed here are Earth analogues that show detectable atmospheric biosignatures like our own planet but do not exhibit a discernable biological surface feature in the disc-averaged spectrum. PMID:19778274

Cockell, Charles S; Kaltenegger, Lisa; Raven, John A

2009-09-01

77

Cosmic Rays and Terrestrial Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Planetary atmospheres are constantly irradiated by both photon and particle radiation sources. These high-energy particles strike the Earth's atmosphere, initiating an extensive air shower. As the air shower propagates deeper, it ionizes the atmosphere by producing charged secondary particles and photons. Increased ionization leads to changes in atmospheric chemistry, resulting in ozone depletion. This increases the flux of solar UVB radiation at the surface, which is potentially harmful to living organisms. Increased ionization affects the global electrical circuit, which could enhance the low-altitude cloud formation rate. Secondary particles such as muons and thermal neutrons produced as a result of hadronic interactions of the primary cosmic rays with the atmosphere are able to reach the ground, enhancing the biological radiation dose. I will present results obtained from a massive computer simulation using a Monte Carlo code CORSIKA to quantify these effects. Results are available in form of look-up tables for use by the scientific community.

Atri, D.

2011-12-01

78

High-Oxygen Planetary Atmospheres and the Existence of Intelligent Life in the Universe  

NASA Astrophysics Data System (ADS)

The existence of a high partial pressure of oxygen in planetary atmospheres elsewhere in the universe is a likely prerequisite for the existence of animal-like life and hence the existence of intelligent life. Whether a planet develops such an atmosphere is influenced by planetary parameters including the composition and size of the planet. The transition to a high oxygen atmosphere would depend on the ability of plate tectonics to provide for organic carbon burial that prohibits back-reaction with photosynthesized atmospheric oxygen. On Earth, plate tectonics accompanied by the oxygen production of photosynthetic bacteria in the Precambrian oceans led to the growth in the level of atmospheric oxygen detectable around 2.0 Gyr ago. Thus, there is a minimum size for an extrasolar planet that develops a high oxygen atmosphere based on the requirement to sustain plate tectonics. On the other hand, if the planet were too big, the loss of early hydrogen may be too slow on the timescale of solar evolution. The timing of the accumulation of atmospheric oxygen, which on Earth resulted in the biological evolution of eukaryotes (eventually including oxygen-utilizing metazoans such as ourselves), would thus appear to depend on geophysics. This may imply a relationship between planetary size and possible degree of biological complexity through time on terrestrial-type planets elsewhere in the Universe.

Catling, D. C.; McKay, C. P.

1999-09-01

79

Models of Polarized Light from Oceans and Atmospheres of Earth-like Extrasolar Planets  

Microsoft Academic Search

Specularly reflected light, or glint, from an ocean surface may provide a\\u000auseful observational tool for studying extrasolar terrestrial planets.\\u000aDetection of sea-surface glints would differentiate ocean-bearing terrestrial\\u000aplanets, i.e. those similar to Earth, from other terrestrial extrasolar\\u000aplanets. The brightness and degree of polarization of both sea-surface glints\\u000aand atmospheric Rayleigh scattering are strong functions of the phase angle

P. R. McCullough

2006-01-01

80

Characterizing extrasolar planets  

Microsoft Academic Search

Transiting extrasolar planets provide the best current opportunities for characterizing the physical properties of extrasolar planets. In this review, I first describe the geometry of planetary transits, and methods for detecting and refining the observations of such transits. I derive the methods by which transit light curves and radial velocity data can be analyzed to yield estimates of the planetary

Timothy M. Brown

2008-01-01

81

Extrasolar planets  

PubMed Central

The first known extrasolar planet in orbit around a Sun-like star was discovered in 1995. This object, as well as over two dozen subsequently detected extrasolar planets, were all identified by observing periodic variations of the Doppler shift of light emitted by the stars to which they are bound. All of these extrasolar planets are more massive than Saturn is, and most are more massive than Jupiter. All orbit closer to their stars than do the giant planets in our Solar System, and most of those that do not orbit closer to their star than Mercury is to the Sun travel on highly elliptical paths. Prevailing theories of star and planet formation, which are based on observations of the Solar System and of young stars and their environments, predict that planets should form in orbit about most single stars. However, these models require some modifications to explain the properties of the observed extrasolar planetary systems.

Lissauer, Jack J.; Marcy, Geoffrey W.; Ida, Shigeru

2000-01-01

82

Extrasolar planets.  

PubMed

The first known extrasolar planet in orbit around a Sun-like star was discovered in 1995. This object, as well as over two dozen subsequently detected extrasolar planets, were all identified by observing periodic variations of the Doppler shift of light emitted by the stars to which they are bound. All of these extrasolar planets are more massive than Saturn is, and most are more massive than Jupiter. All orbit closer to their stars than do the giant planets in our Solar System, and most of those that do not orbit closer to their star than Mercury is to the Sun travel on highly elliptical paths. Prevailing theories of star and planet formation, which are based on observations of the Solar System and of young stars and their environments, predict that planets should form in orbit about most single stars. However, these models require some modifications to explain the properties of the observed extrasolar planetary systems. PMID:11035782

Lissauer, J J; Marcy, G W; Ida, S

2000-11-01

83

Studies of the planetary atmospheres in Russia (2007-2010)  

NASA Astrophysics Data System (ADS)

An overview of results obtained in the field of planetary atmosphere studies in Russia in 2007-2010 prepared by the Commission on Planetary Atmospheres of the National Geophysical Committee for the National Report on Meteorology and Atmospheric Sciences to the XXV General Assembly of the International Union of Geodesy and Geophysics (Melbourne, 28 June-7 July 2011) [1, 2] is presented.

Korablev, O. I.; Zasova, L. V.; Fedorova, A. A.; Titov, D. V.; Ignatiev, N. I.; Rodin, A. V.; Shematovich, V. I.; Belyaev, D. A.; Khatuntsev, I. V.; Izakov, M. N.; Shakun, A. V.; Burlakov, A. V.; Mayorov, B. S.

2012-05-01

84

Updated Review of Planetary Atmospheric Electricity  

NASA Astrophysics Data System (ADS)

This paper reviews the progress achieved in planetary atmospheric electricity, with focus on lightning observations by present operational spacecraft, aiming to fill the hiatus from the latest review published by Desch et al. (Rep. Prog. Phys. 65:955 997, 2002). The information is organized according to solid surface bodies (Earth, Venus, Mars and Titan) and gaseous planets (Jupiter, Saturn, Uranus and Neptune), and each section presents the latest results from space-based and ground-based observations as well as laboratory experiments. Finally, we review planned future space missions to Earth and other planets that will address some of the existing gaps in our knowledge.

Yair, Y.; Fischer, G.; Simões, F.; Renno, N.; Zarka, P.

2008-06-01

85

Updated Review of Planetary Atmospheric Electricity  

NASA Astrophysics Data System (ADS)

This paper reviews the progress achieved in planetary atmospheric electricity, with focus on lightning observations by present operational spacecraft, aiming to fill the hiatus from the latest review published by Desch et al. (Rep. Prog. Phys. 65:955-997, 2002). The information is organized according to solid surface bodies (Earth, Venus, Mars and Titan) and gaseous planets (Jupiter, Saturn, Uranus and Neptune), and each section presents the latest results from space-based and ground-based observations as well as laboratory experiments. Finally, we review planned future space missions to Earth and other planets that will address some of the existing gaps in our knowledge.

Yair, Y.; Fischer, G.; Simões, F.; Renno, N.; Zarka, P.

86

Research Paper Remote Sensing of Planetary Properties and Biosignatures on Extrasolar Terrestrial Planets  

Microsoft Academic Search

The major goals of NASA' s Terrestrial Planet Finder (TPF) and the European Space Agency' s Darwin missions are to detect terrestrial-sized extrasolar planets directly and to seek spec- troscopic evidence of habitable conditions and life. Here we recommend wavelength ranges and spectral features for these missions. We assess known spectroscopic molecular band fea- tures of Earth, Venus, and Mars

DAVID J. DES MARAIS; MARTIN O. HARWIT; KENNETH W. JUCKS; JAMES F. KASTING; DOUGLAS N. C. LIN; JONATHAN I. LUNINE; JEAN SCHNEIDER; SARA SEAGER; WESLEY A. TRAUB; NEVILLE J. WOOLF

87

Spectral signatures of photosynthesis. II. Coevolution with other stars and the atmosphere on extrasolar worlds.  

PubMed

As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take previously simulated planetary atmospheric compositions for Earth-like planets around observed F2V and K2V, modeled M1V and M5V stars, and around the active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as well as very low O2 content in case anoxygenic photosynthesis dominates. With a line-by-line radiative transfer model, we calculate the incident spectral photon flux densities at the surface of the planet and under water. We identify bands of available photosynthetically relevant radiation and find that photosynthetic pigments on planets around F2V stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in the near-infrared, in bands at 0.93-1.1 microm, 1.1-1.4 microm, 1.5-1.8 microm, and 1.8-2.5 microm. However, underwater organisms will be restricted to wavelengths shorter than 1.4 microm and more likely below 1.1 microm. M star planets without oxygenic photosynthesis will have photon fluxes above 1.6 microm curtailed by methane. Longer-wavelength, multi-photo-system series would reduce the quantum yield but could allow for oxygenic photosystems at longer wavelengths. A wavelength of 1.1 microm is a possible upper cutoff for electronic transitions versus only vibrational energy; however, this cutoff is not strict, since such energetics depend on molecular configuration. M star planets could be a half to a tenth as productive as Earth in the visible, but exceed Earth if useful photons extend to 1.1 microm for anoxygenic photosynthesis. Under water, organisms would still be able to survive ultraviolet flares from young M stars and acquire adequate light for growth. PMID:17407410

Kiang, Nancy Y; Segura, Antígona; Tinetti, Giovanna; Govindjee; Blankenship, Robert E; Cohen, Martin; Siefert, Janet; Crisp, David; Meadows, Victoria S

2007-02-01

88

The Compositional Diversity of Extrasolar Terrestrial Planets  

NASA Astrophysics Data System (ADS)

The details of the formation of the terrestrial planets are long-standing questions in the geological, planetary and astronomical sciences, with the discovery of extrasolar planetary systems placing even greater emphasis on these questions. Here we present simulations of the bulk compositions of simulated terrestrial planets in extrasolar planetary systems. These simulations incorporate both giant planet migration into the dynamical simulations and a variety of ices, clathrates and hydrates into the chemical modeling, providing us with a more inclusive view of extrasolar terrestrial planet formation. We find that a diverse range of extrasolar terrestrial planets are produced, ranging from bulk elemental compositions similar to that of Earth to those that are enriched in elements such as C and Si, producing planets with compositions unlike anything we have previously observed. Giant planet migration significantly alters the composition of the final terrestrial planet by redistributing material throughout the system. Simulated terrestrial planets produced within the migration simulations are found to contain larger amounts of Mg-silicate species and hydrous material. These variations in composition will greatly influence planetary processes such as plate tectonics, planetary interior structure and the primary atmospheric composition.

Carter-Bond, J. C.; O'Brien, D. P.

2011-12-01

89

Moon formation and orbital evolution in extrasolar planetary systems - A literature review  

NASA Astrophysics Data System (ADS)

With over 450 extrasolar planets detected, the possibility of searching for moons of these planets is starting to be investigated. In order to make efficient use of limited observing resources, it would be useful if the types of moons that a given planet is likely to host was known prior to detection. Fortunately, informed by simulations of moon formation in our own solar system, as well as more general theoretical investigations of moon orbital evolution, such information is now available. I present a review of literature results concerning the likely physical and orbital properties of extra-solar moons, and how these properties are predicted to vary with the properties of their host planet.

Lewis, K.

2011-02-01

90

Tidal Acceleration, Rotation and Apses Alignment in Resonant ExtraSolar Planetary Systems  

Microsoft Academic Search

The action of a semi-diurnal planetary tidal bulge, on the evolution of a 2-planet system, was studied in several circumstances. The main consequence is the synchronisation of one close planet in a timescale which, for typical values of the tidal time lag, is of the order of 107 years. During this time, the planetary rotation is the only parameter significantly

S. Ferraz-Mello

2002-01-01

91

The search for extra-solar terrestrial planets: techniques and technology. Proceedings. Conference, Boulder, CO (USA), 14 - 17 May 1995  

Microsoft Academic Search

The following topics were dealt with: search for extrasolar terrestrial planets, techniques, technology, planetary atmosphere evolution, solar system evolution, photometric search, radial velocity searches, photon-noise limit, astrometric searches, OSI mission, GAIA mission, ground-based interferometry, FRESIP mission, DARWIN project, and public involvement in extrasolar planet detection.

J. M. Shull; H. A. Thronson Jr.; S. A. Stern

1996-01-01

92

Millimagnitude photometry for transiting extrasolar planetary candidates . V. Follow-up of 30 OGLE transits. New candidates  

NASA Astrophysics Data System (ADS)

Aims: We used VLT/VIMOS images in the V band to obtain light curves of the extrasolar planetary transits OGLE-TR-111 and OGLE-TR-113 and the candidate planetary transits: OGLE-TR-82, OGLE-TR-86, OGLE-TR-91, OGLE-TR-106, OGLE-TR-109, OGLE-TR-110, OGLE-TR-159, OGLE-TR-167, OGLE-TR-170, OGLE-TR-171. Methods: Using difference imaging photometry, we were able to achieve millimagnitude errors in the individual data points. We present the analysis of the data and the light curves by measuring transit amplitudes and ephemerides and by calculating geometrical parameters for some of the systems. Results: We observed nine OGLE objects at the predicted transit moments. Two other transits were shifted in time by a few hours. For another seven objects we expected to observe transits during the VIMOS run, but they were not detected. Conclusions: The stars OGLE-TR-111 and OGLE-TR-113 are probably the only OGLE objects in the observed sample to host planets, with the other objects being very likely eclipsing binaries or multiple systems. In this paper we also report on four new transiting candidates which we have found in the data. ARRAY(0x42d0300)

Pietrukowicz, P.; Minniti, D.; Díaz, R. F.; Fernández, J. M.; Zoccali, M.; Gieren, W.; Pietrzy?ski, G.; Ruíz, M. T.; Udalski, A.; Szeifert, T.; Hempel, M.

2010-01-01

93

The HARPS search for southern extra-solar planets. XXVIII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems  

Microsoft Academic Search

Context. Low-mass extrasolar planets are presently being discovered at an increased pace by radial velocity and transit surveys, which opens a new window on planetary systems. Aims: We are conducting a high-precision radial velocity survey with the HARPS spectrograph, which aims at characterizing the population of ice giants and super-Earths around nearby solar-type stars. This will lead to a better

C. Lovis; D. Ségransan; M. Mayor; S. Udry; W. Benz; J.-L. Bertaux; F. Bouchy; A. C. M. Correia; J. Laskar; G. Lo Curto; C. Mordasini; F. Pepe; D. Queloz; N. C. Santos

2011-01-01

94

Infrared spectroscopic measurements on planetary atmospheric gases  

SciTech Connect

Infrared spectroscopic measurements were performed on trace gas molecules known to be infrared-active in the atmospheres of Earth and the Outer Planets. The measurements were performed at low temperatures relevant to the planetary atmospheres employing the high spectral resolution attainable with a tunable diode laser spectrometer. Accurate data on the intensities, N(2-), O(2-), and air-broadened half-widths of lines in the nu(sub 1)-fundamental band (7.78 microns) of 14-N2O-16 were obtained at several temperatures between 185 and 296 K. These data are needed in remote sensing, ozone depletion, and climate modeling studies of the terrestrial atmosphere. The pressure-induced shifts of some 14-N2O-16 lines were also measured. Intensity data in the 10(sup 0)0-01(sup 1)0 band (13.87 microns) of 12-C16-O2 at 295 K which are useful in studies of the thermal structure of the Earth's atmosphere were measured. They differ significantly from previously published and cataloged data. Measurements of the absolute intensities and the H2-broadened half-widths of several spectral lines in the nu(sub 3) band of GeH4, which was detected in the atmospheres of the Outer Planets, were performed at low temperatures between 94 and 300 K. The combined intensity of the nu(sub 3) bands of all of the five isotopic species of GeH4 as well as that of the Q-branches alone were measured independently at 294 using the Wilson-Wells-Penner-Weber Technique. Absolute intensities, collision-broadened half-widths, and pressure-induced shifts of several lines in the nu(sub 4)-fundamental bands of 12-CH4 and 13-CH4 around 7.70 microns, the nu(sub 2)-fundamantal band of 12-CH3D at 4.55 microns, the nu(sub 3)-fundamental band of 12-CH3D at 7.76 microns, the nu(sub 6)-fundamental band of 12-CH3D at 8.61 microns, and the CO fundamental at 4.67 microns, all of which appear in the spectra of the Outer Planets, were measured at low temperatures.

Chudamani, S.

1989-01-01

95

Extrasolar Planet Research at Universidad de Chile  

NASA Astrophysics Data System (ADS)

I will present the latest publications and current status on projects lead by researchers and doctoral candidates at Universidad de Chile in the area of extrasolar planets. Making use of the privileged access to world-class telescopes, the research efforts are focused in ground-based observations. Long- and short-term projects are currently underway: (1) exoplanetary atmospheric characterization, (2) monitoring of southern transiting planets searching for transit-timing variations, (3) the Calan-Hertfordshire Extrasolar planet RV search (CHEPS), and (4) study of post main-sequence planetary hosts.

Rojo, Patricio; Hoyer, S.; Jenkins, J.; Jones, M.

2010-10-01

96

Planetary Atmospheres: Probing Structures Through Millimeterwave Observations of Carbon Monoxide  

Microsoft Academic Search

Millimeter interferometric spectroscopy of planetary bodies provides unique and important ways to study their atmospheres. Carbon monoxide provides significant spectral features on Titan, Mars, and Venus. Observations of carbon monoxide from the atmospheres of these bodies were obtained with the Owens Valley Radio Observatory Millimeter Array in order to address specific questions about the state and structure of their atmospheres.

Mark Andrew Gurwell

1996-01-01

97

Chemical and dynamical processes in the atmospheres of, I. Ancient and present-day earth, II. Jupiter and Galilean satellites, III. Extrasolar "Hot Jupiters"  

NASA Astrophysics Data System (ADS)

When exposed to stellar UV radiation, chemical processes will be governed not only by temperature/pressure but also the spectrum of the incoming dissociative photon flux; the system will approach kinetic, or photochemical, equilibrium, instead of thermochemical equilibrium. Over the previous decades, photochemistry has proven to be a powerful tool for predicting the chemical composition in the atmospheres of solar planets and their satellites. For example, the ozone layer in our own atmosphere (stratosphere) is a photochemical product of oxygen. In this thesis, I apply a photochemical model to the study of a variety of astronomical objects: the Earth, Jupiter, the Galilean satellite Callisto, and extrasolar "hot Jupiters" (HD 209458b). For the Earth, a method for utilizing the isotopic composition of CO 2 and N 2 O to monitor global changes due to these two greenhouse gases is developed. For objects other than the Earth, the model facilitates in the interpretation of data acquired by remote (telescopic) and in situ (spacecraft) measurements. The ultimate goal is to understand the conditions of chemical and physical environments in protoplanetary nebulae, which will provide clues as to the formation of planetary systems; the synthesis of organic compounds which could lead to the appearance of life; and the evolution of planetary atmospheres such as the formation of Titan's nitrogen-rich atmosphere.

Liang, Mao-Chang

98

Symmetric and asymmetric librations in extrasolar planetary systems: a global view  

Microsoft Academic Search

We present a global view of the resonant structure of the phase space of a planetary system with two planets, moving in the same plane, as obtained from the set of the families of periodic orbits. An important tool to understand the topology of the phase space is to determine the position and the stability character of the families of

John D. Hadjidemetriou

2006-01-01

99

AN ALUMINUM/CALCIUM-RICH, IRON-POOR, WHITE DWARF STAR: EVIDENCE FOR AN EXTRASOLAR PLANETARY LITHOSPHERE?  

SciTech Connect

The presence of elements heavier than helium in white dwarf atmospheres is often a signpost for the existence of rocky objects that currently or previously orbited these stars. We have measured the abundances of various elements in the hydrogen-atmosphere white dwarfs G149-28 and NLTT 43806. In comparison with other white dwarfs with atmospheres polluted by heavy elements, NLTT 43806 is substantially enriched in aluminum but relatively poor in iron. We compare the relative abundances of Al and eight other heavy elements seen in NLTT 43806 with the elemental composition of bulk Earth, with simulated extrasolar rocky planets, with solar system meteorites, with the atmospheric compositions of other polluted white dwarfs, and with the outer layers of the Moon and Earth. The best agreement is found with a model that involves accretion of a mixture of terrestrial crust and upper mantle material onto NLTT 43806. The implication is that NLTT 43806 is orbited by a differentiated rocky planet, perhaps quite similar to Earth, that has suffered a collision that stripped away some of its outer layers.

Zuckerman, B.; Klein, B.; Jura, M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Koester, D. [Institut fur Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel (Germany); Dufour, P. [Departement de Physique, Universite de Montreal, Montreal, QC H3C 3J7 (Canada); Melis, Carl [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093-0424 (United States)

2011-10-01

100

Symmetric and asymmetric librations in extrasolar planetary systems: a global view  

Microsoft Academic Search

We present a global view of the resonant structure of the phase space of a planetary system with two planets, moving in the\\u000a same plane, as obtained from the set of the families of periodic orbits. An important tool to understand the topology of the\\u000a phase space is to determine the position and the stability character of the families of

John D. Hadjidemetriou

101

MEP and planetary climates: insights from a two-box climate model containing atmospheric dynamics  

PubMed Central

A two-box model for equator-to-pole planetary heat transport is extended to include simple atmospheric dynamics. The surface drag coefficient CD is treated as a free parameter and solutions are calculated analytically in terms of the dimensionless planetary parameters ? (atmospheric thickness), ? (rotation rate) and ? (advective capability). Solutions corresponding to maximum entropy production (MEP) are compared with solutions previously obtained from dynamically unconstrained two-box models. As long as the advective capability ? is sufficiently large, dynamically constrained MEP solutions are identical to dynamically unconstrained MEP solutions. Consequently, the addition of a dynamical constraint does not alter the previously obtained MEP results for Earth, Mars and Titan, and an analogous result is presented here for Venus. The rate of entropy production in an MEP state is shown to be independent of rotation rate if the advective capability ? is sufficiently large (as for the four examples in the solar system), or if the rotation rate ? is sufficiently small. The model indicates, however, that the dynamical constraint does influence the MEP state when ? is small, which might be the case for some extrasolar planets. Finally, results from the model developed here are compared with previous numerical simulations in which the effect of varying surface drag coefficient on entropy production was calculated.

Jupp, Tim E.; Cox, Peter M.

2010-01-01

102

Tidal Acceleration, Rotation and Apses Alignment in Resonant Extra-Solar Planetary Systems.  

NASA Astrophysics Data System (ADS)

The action of a semi-diurnal planetary tidal bulge, on the evolution of a 2-planet system, was studied in several circumstances. The main consequence is the synchronisation of one close planet in a timescale which, for typical values of the tidal time lag, is of the order of 107 years. During this time, the planetary rotation is the only parameter significantly affected. In the case of an isolated planet, the orbit circularizes and the tidal action tends to zero. In 2-planet resonant systems (as Gliese 876), however, the eccentricities are not damped by the tides, and the tidal bulge oscillates around the noon direction. This oscillation and an imperfect synchronisation allow the continuation of the energy dissipation. Since the system can no longer pump energy from the planet rotation, because of the synchronisation, the planet orbit decays. The actual decay is, however, very slow. The general study of an adiabatically perturbed 2:1-resonant system has shown periastrons alignment (? ? ~ 0o) and counter-alignment (? ? ~ 180o). (As in the case of the 5:2 planetary resonance cf. Michtchenko and Ferraz-Mello, Icarus 149, 357, 2001.) Periastrons alignment happens roughly when e1 > 0.1 and counter-alignment when e1 < 0.1. However, these cases are not the only possible stationary solutions in the 2:1 resonance. When the innermost planet is more massive than the outermost one, for a wide range of eccentricities, stationary solutions are found where the distance between the periastrons is fixed, but at values of ? ? which are not 0o or 180o. In these asymmetric libration states, ? ? takes a value between 0o and 180o, which depends on the ratio of the planet masses and on the eccentricities. These new solutions result from a bifurcation of the stable stationary orbit and occur in pairs, one on each side of 0o (or 180o). Acknowledgements: FAPESP and CNPq.

Ferraz-Mello, S.

2002-09-01

103

Shallow-Water Turbulence Simulations of Solar and Extrasolar Giant Planetary Atmsopheres  

NASA Astrophysics Data System (ADS)

The banded appearance and zonal winds of the giant planets in our Solar System have been demonstrated to be well-modeled by a shallow layer of divergent turbulent fluid on a rotating sphere [Cho & Polvani, Science (1996)]. In this study, we re-address the problem of jet/band morphology with a simple extension of the above model, which includes variable mass thickness to represent prescribed heating in an equivalent barotropic formulation. Similar models have been previously used to study the role of adiabatic and diabatic forcing on the dynamics of stratospheric polar vortex in a non-turbulent context [e.g., Juckes, JAS (1989); Salby, JAS (1991); Norton, JAS (1994); Polvani et al., JAS (1994)]. Here, we combine the two approaches and address the question of the appearance of the recently-detected close-in extrasolar giant planets (CEGPs) --- Jupiter-like objects which orbit ~0.05 AU from their primary stars. We present results from a series of high-resolution, fully turbulent simulations of the planet HD 209458 b, a transiting CEGP which is expected to be tidally locked, possessing permanent day/night hemispheres and a rotation period equaling its orbital period of 3.5 days. In our study, we find in most cases ~4 quasi-steady jets, and their corresponding weak banding, due to the slower (than Jupiter) rotation rate and a displaced circumpolar vortex on each of the rotation (north and south) poles. In general, when the day/night temperature difference is small (less than ~10% of the average layer temperature), a rotating quadrupolar ``thermal spot'' structure emerges in the flow. In contrast, at Jupiter-like rotation rate and orbital distance, the thermal structure becomes strongly zonally-symmetric, alternating in latitude, as seen in the 5 micron images of Jupiter. Our findings suggest the possibility of variabilities in the flux measurements of CEGP's that will be obtained in the future.

Cho, J. Y.; Menou, K.; Hansen, B.; Seager, S.

2002-05-01

104

The EDISON infrared space observatory and the study of extra-solar planetary material  

NASA Astrophysics Data System (ADS)

Edison is a proposed large-aperture, radiatively-cooled space observatory planned to operate at wavelengths between 2 and 130 micrometers or longer. Current estimates for the telescope allow an aperture of 1.7 m which will achieve a final equilibrium temperature of about 30 K, although use of cryocoolers may permit temperatures below 20 K. Edison will be a powerful tool to investigate our Solar System, as well as planetary material around distant stars. At near- and mid-infrared wavelengths, where planetary material emits most of its radiation, Edison will be the most sensitive photometric and spectroscopic observatory under current consideration by the space agencies. With its large aperture, Edison will be able both to resolve the structure in nearby circumstellar 'Vega disks' and to discriminate faint IR emission in the crowded environment of the galactic plane. With its long lifetime, Edison will allow extensive follow-up observations and increase the likelihood of catching transient events. We propose Edison as a precursor to elements of a future space-based IR interferometer.

Thronson, H. A., Jr.; Hawarden, T. G.; Bally, J.; Rapp, D.; Stern, S. A.

1994-02-01

105

Profiles of Ion and Aerosol Interactions in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

In planetary atmospheres the nature of the aerosols varies, as does the relative importance of different sources of ion production. The nature of the aerosol and ion production is briefly reviewed here for the atmospheres of Venus, Mars, Jupiter and Titan using the concepts established for the terrestrial atmosphere. Interactions between the ions formed and aerosols present cause (1) charge exchange, which can lead to substantial aerosol charge and (2) ion removal. Consequences of (1) are that (a) charged aerosol are more effectively removed by conducting liquid droplets than uncharged aerosol and (b) particle particle coagulation rates are modified, influencing particle residence times in the relevant atmosphere. Consequences of (2) are that ions are removed in regions with abundant aerosol, which may preclude charge flow in an atmosphere, such as that associated with an atmospheric electrical circuit. In general, charge should be included in microphysical modeling of the properties of planetary aerosols.

Tripathi, S. N.; Michael, M.; Harrison, R. G.

2008-06-01

106

Profiles of Ion and Aerosol Interactions in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

In planetary atmospheres the nature of the aerosols varies, as does the relative importance of different sources of ion production. The nature of the aerosol and ion production is briefly reviewed here for the atmospheres of Venus, Mars, Jupiter and Titan using the concepts established for the terrestrial atmosphere. Interactions between the ions formed and aerosols present cause (1) charge exchange, which can lead to substantial aerosol charge and (2) ion removal. Consequences of (1) are that (a) charged aerosol are more effectively removed by conducting liquid droplets than uncharged aerosol and (b) particle-particle coagulation rates are modified, influencing particle residence times in the relevant atmosphere. Consequences of (2) are that ions are removed in regions with abundant aerosol, which may preclude charge flow in an atmosphere, such as that associated with an atmospheric electrical circuit. In general, charge should be included in microphysical modeling of the properties of planetary aerosols.

Tripathi, S. N.; Michael, M.; Harrison, R. G.

107

Evaporation of extrasolar planets  

Microsoft Academic Search

This article presents a review on the observations and theoretical modeling of the evaporation of extrasolar planets. The observations and the resulting constraints on the upper atmosphere (thermosphere and exosphere) of the ``hot-Jupiters'' are described. The early observations of the first discovered transiting extrasolar planet, HD209458b, allowed the discovery that this planet has an extended atmosphere of escaping hydrogen. Subsequent

A. Lecavelier Des Etangs

2010-01-01

108

Observations of Planetary and Satellite Atmospheres and Surfaces  

NASA Astrophysics Data System (ADS)

The full opening of the submillimeter range with the operation of Herschel is expected to prove very useful for the study of planetary atmospheres and surfaces. Areas of anticipated progress include: (i) the origin and evolution of the Giant Planets, from improved determinations of the abundance of deuterium and helium (ii) the origin of the external source of oxygen in the Giant Planets and Titan (iii) several compositional and physical aspects of planetary atmospheres, especially the issue of vertical transport in Uranus and Neptune and the martian photochemistry and (iv) the thermophysical and compositional properties of planetary surfaces, including the size distribution of transneptunian objects. The high sensitivity of all instruments and the diversity of their spectral resolutions is well suited to the diversity of size and atmospheric pressure within the bodies of the Solar System.

Lellouch, E.

2001-07-01

109

Star-planet magnetic interaction and evaporation of planetary atmospheres  

NASA Astrophysics Data System (ADS)

Context. Stars interact with their close-in planets through radiation, gravitation and magnetic fields. Aims: We investigate the energy input to a planetary atmosphere by reconnection between stellar and planetary magnetic fields and compare it to the energy input of the extreme ultraviolet (EUV) radiation field of the star. Methods: We quantify the power released by magnetic reconnection at the boundary of the planetary magnetosphere that is conveyed to the atmosphere by accelerated electrons. We introduce simple models to evaluate the energy spectrum of the accelerated electrons and the energy dissipated in the atmospheric layers in the polar region of the planet upon which they impinge. A simple transonic isothermal wind flow along field lines is considered to estimate the increase in mass loss rate in comparison with a planet irradiated only by the EUV flux of its host star. Results: We find that energetic electrons can reach levels down to column densities of 1023-1025 m-2, comparable with or deeper than EUV photons, and increase the mass loss rate up to a factor of 30-50 in close-in (< 0.10 AU), massive (?1.5 Jupiter masses) planets. Mass loss rates up to (0.5-1.0) × 109 kg s-1 are found for atmospheres heated by electrons accelerated by magnetic reconnection at the boundary of planetary magnetospheres. On the other hand, average mass loss rates up to (0.3-1.0) × 1010 kg s-1 are found in the case of magnetic loops interconnecting the planet with the star. Conclusions: The star-planet magnetic interaction provides a remarkable source of energy for planetary atmospheres, generally comparable with or exceeding that of stellar EUV radiation for close-in planets. Therefore, it must be included in models of chemical evolution or evaporation of planetary atmospheres as well as in modelling of light curves of transiting planets at UV wavelengths.

Lanza, A. F.

2013-09-01

110

Periastron precession measurements in transiting extrasolar planetary systems at the level of general relativity  

NASA Astrophysics Data System (ADS)

Transiting exoplanetary systems are surpassingly important among the planetary systems since they provide the widest spectrum of information for both the planet and the host star. If a transiting planet is on an eccentric orbit, the duration of transits TD is sensitive to the orientation of the orbital ellipse relative to the line of sight. The precession of the orbit results in a systematic variation in both the duration of individual transit events and the observed period between successive transits, Pobs. The periastron of the ellipse slowly precesses due to general relativity and possibly the presence of other planets in the system. This secular precession can be detected through the long-term change in Pobs (transit timing variations, TTV) or in TD (transit duration variations, TDV). We estimate the corresponding precession measurement precision for repeated future observations of the known eccentric transiting exoplanetary systems (XO-3b, HD 147506b, GJ 436b and HD 17156b) using existing or planned space-borne instruments. The TDV measurement improves the precession detection sensitivity by orders of magnitude over the TTV measurement. We find that TDV measurements over a approximately 4yr period can typically detect the precession rate to a precision well exceeding the level predicted by general relativity.

Pál, András; Kocsis, Bence

2008-09-01

111

Characterisation of extrasolar planetary transit candidates. II. The companions to late M-type stars  

NASA Astrophysics Data System (ADS)

We present a second paper of a complete characterization of stars whose low-depth transits were discovered by the OGLE-III campaign to select the most promising candidates for spectroscopic confirmation. This paper follows a similar analysis to one previously performed in Gallardo et al. (2005, A&A, 431, 707). We present new optical and near-IR photometry and derive physical parameters such as effective temperature (Teff), distance (d), the stellar radii (R_ast), and the companion radii (Rc). We selected eight M (2800 K ? Teff ? 3850 K) or K (3850 K ? Teff ? 5150 K) stellar objects as potential candidates to host exoplanets, even though, considering the radii of their companions, only the stars OGLE-TR-61, OGLE-TR-74, OGLE-TR-123, and OGLE-TR-173 are the most promising M-type transit candidates to host planets. A confirmation of the planetary nature of any of these objects would be extremely valuable in providing a means of characterizing planets transiting M-type dwarfs with effective temperatures down to only 2900 K.

Gallardo, J.; Silva, S.; Ramírez Alegría, S.; Minniti, D.; Pietrukowicz, P.

2010-11-01

112

The presence of methane in the atmosphere of an extrasolar planet.  

PubMed

Molecules present in the atmospheres of extrasolar planets are expected to influence strongly the balance of atmospheric radiation, to trace dynamical and chemical processes, and to indicate the presence of disequilibrium effects. As molecules have the potential to reveal atmospheric conditions and chemistry, searching for them is a high priority. The rotational-vibrational transition bands of water, carbon monoxide and methane are anticipated to be the primary sources of non-continuum opacity in hot-Jupiter planets. As these bands can overlap in wavelength, and the corresponding signatures from them are weak, decisive identification requires precision infrared spectroscopy. Here we report a near-infrared transmission spectrum of the planet HD 189733b that shows the presence of methane. Additionally, a resolved water vapour band at 1.9 mum confirms the recent claim of water in this object. On thermochemical grounds, carbon monoxide is expected to be abundant in the upper atmosphere of hot-Jupiter planets, but is not identifiable here; therefore the detection of methane rather than carbon monoxide in such a hot planet could signal the presence of a horizontal chemical gradient away from the permanent dayside, or it may imply an ill-understood photochemical mechanism that leads to an enhancement of methane. PMID:18354477

Swain, Mark R; Vasisht, Gautam; Tinetti, Giovanna

2008-03-20

113

Planetary Atmospheres and the Search for Life.  

ERIC Educational Resources Information Center

|Different ways in which the atmospheres of different planets have originated and evolved are discussed. Includes tables on the atmospheric composition of: (1) Earth; (2) Mars; (3) Venus; (4)Titan (Saturn's Satellite); and (5) the outer planets. (SK)|

Owen, Tobias

1982-01-01

114

The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres.  

PubMed

The ultimate climate emergency is a 'runaway greenhouse': a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming. Warming ceases only after the surface reaches approximately 1400 K and emits radiation in the near-infrared, where water is not a good greenhouse gas. This would evaporate the entire ocean and exterminate all planetary life. Venus experienced a runaway greenhouse in the past, and we expect that the Earth will in around 2 billion years as solar luminosity increases. But could we bring on such a catastrophe prematurely, by our current climate-altering activities? Here, we review what is known about the runaway greenhouse to answer this question, describing the various limits on outgoing radiation and how climate will evolve between these. The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one. High climate sensitivity might provide a warning. If we, or more likely our remote descendants, are threatened with a runaway greenhouse, then geoengineering to reflect sunlight might be life's only hope. Injecting reflective aerosols into the stratosphere would be too short-lived, and even sunshades in space might require excessive maintenance. In the distant future, modifying Earth's orbit might provide a sustainable solution. The runaway greenhouse also remains relevant in planetary sciences and astrobiology: as extrasolar planets smaller and nearer to their stars are detected, some will be in a runaway greenhouse state. PMID:22869797

Goldblatt, Colin; Watson, Andrew J

2012-09-13

115

In situ observations of the atmospheres of terrestrial planetary bodies  

NASA Astrophysics Data System (ADS)

Direct observations of planetary atmospheres are scarce and significantly more data are needed for the understanding of their behavior. The principal theme of this dissertation is the exploration of planetary atmospheres by means of in situ observations, focusing on investigations performed by payloads operating on the planetary surface. The contextual frame includes the whole palette of planetary exploration including definition of scientific objectives, observational strategies, scientific payload and data analysis, as well as development of technological solutions and simulation models for planetary missions. Thus approach also led to the initiation of the planetary missions MetNet and NetLander to Mars. This work contributes to both in situ atmospheric observations and atmospheric modeling, which are strongly intertwined. Modeling efforts require observations to give solid background and foundation for the simulations, and on the other hand, definition of observational strategies and instrumentation gets guidance from modeling efforts to optimize the use of mission resources, as is successfully demonstrated in this dissertation. The dissertation consists of Summary and nine original scientific publications. Publications 1 to 7 and Summary address the development of new atmospheric science payloads for exploration missions to Mars and Titan, a Saturnian moon. Actual and planned missions included are the Mars-96 Program and its Small Surface Stations and Penetrators during the years 1988-1996, PPI/HASI onboard the Cassini/Huygens spacecraft to Saturn and its moon Titan in 1989-2005, the MET-P payload onboard the Mars Polar Lander in 1997-1999, the BAROBIT instrument for the Beagle 2 lander in 2001-2003, the NetLander Mars Mission in 1997-2001 and the ongoing Mars MetNet Mission, started in 2000. Specifically, Publication 4 reviews the sensor qualification process that facilitated the use of new type of atmospheric sensors at Mars, while Publications 2 and 7, as well as Summary, address the highly successful determination of the Titan atmospheric pressure profile. Publication 8 combines in situ observations and simulations by analyzing Mars Pathfinder measurements with the help of a Martian mesoscale atmospheric model. Finally, in Publication 9 the effect of airborne dust and CO 2 on the radiative transfer in the Martian atmosphere is assessed and a new radiative transfer paramerization scheme for the mesoscale model is introduced.

Harri, Ari-Matti

2005-11-01

116

Consequences of planetary migration: Kuiper belt dynamics and atmospheric escape from hot Jupiters  

NASA Astrophysics Data System (ADS)

The current resonance structure of the Kuiper belt suggests that during the late stages of planet formation, Neptune migrated outward as it scattered residual planetesimal debris. Extrasolar planetary systems also show evidence for planetary migration. Approximately 1/5 of the extrasolar planets discovered to date are "hot Jupiters," which likely exchanged angular momentum with gas disks, migrating large distances inward to reach their current semi-major axes of ~0.05 AU. In this thesis, I discuss three consequences of planetary migration. (1) During its migration, Neptune captured Kuiper belt objects (KBOs) into mean motion resonances. The current spatial distribution of KBOs in a particular resonance, the 2:1, acts as a celestial speedometer--fast planetary migration generates a larger population of 2:1 resonant KBOs trailing rather than leading Neptune on the sky. We provide an explanation of this phenomenon for the first time. Central to our understanding is how planetary migration shifts the equilibrium points of the superposed direct and indirect potentials felt by a KBO. The currently observed distribution of 2:1 KBOs excludes total migration times < 20 Myr with >99.65% confidence and is statistically consistent with the even population generated by slow migration. However, these observations are beset by systematic uncertainties. Observations with new telescopes such as PanSTARRS or LSST will tell us how quickly Neptune could have migrated. (2) Neptune's migration, powered by scattering planetesimal debris, was stochastic ("noisy"). Extreme stochasticity defeats resonance capture. We construct a theory analogous to Brownian motion for how a planet's orbital semi-major axis fluctuates in response to random planetesimal scatterings. The degree of stochasticity in Neptune's migration depends both on the sizes of the planetesimals driving migration and on their orbital elements and cannot currently be computed using N-body simulations. We find that capture of resonant Kuiper belt objects by a migrating Neptune remains effective if the bulk of the primordial disk was locked in bodies having sizes [Special characters omitted.] km and if the fraction of disk mass in objects with sizes [Special characters omitted.] 1000 km was less than a few percent. Coagulation simulations produce a size distribution of primordial planetesimals that easily satisfies these constraints. We conclude that stochasticity did not interfere with Neptune's ability to capture and retain KBOs in first-order resonances during its migration. (3) Photoionization heating from UV radiation incident on the atmospheres of hot Jupiters drives planetary mass loss. Observations of stellar Lyman- a absorption at high velocities (±100 km s -1 ) have suggested that the hot Jupiter HD 209458b is losing atomic hydrogen. We show that mass loss takes the form of a hydrodynamic ("Parker") wind, emitted either from the planet's dayside during lulls in the stellar wind, or from the nightside when heat is transported there by horizontal flows. A hot Jupiter loses at most ~0.06% of its mass during its host star's pre-main-sequence phase and ~0.6% of its mass during the star's main sequence lifetime. At no stage do planetary winds reach velocities of ±100 km s -1 . We conclude that while UV radiation does indeed drive winds from hot Jupiters, such winds cannot significantly alter planet ary masses during any evolutionary stage, nor can they generate the observed decrements in Lya flux in HD 209458b.

Murray-Clay, Ruth Ann

117

A Novel Diagnosis of Chemical Disequilibrium in Extrasolar Planet and Substellar Object Atmospheres  

NASA Astrophysics Data System (ADS)

With recent advancements in spectroscopic capabilities, characterization of the temperatures and compositions of extra-solar planets is becoming more prevalent. One outstanding issue one can address with temperature and abundance determinations is the role that disequilibrium plays in sculpting the atmospheric compositions. A variety of disequilibrium models now exist in the literature to explore various planets and the effects that photochemistry and vertical mixing have on the molecular abundances. In this investigation we introduce a novel approach to diagnosing disequilibrium without the need of sophisticated photochemical/kinetics models. In short, we define an “equilibrium” line as a function of a representative planet temperature. If we can determine the abundances of H2O, CH4, CO, and H2, we can evaluate a simple analytic formula to quickly assess whether or not the atmospheric composition is in disequilibrium. We verify the usefulness of this approach with state-of-the-art chemistry-transport models and find that, as expected, cooler planets tend to show the strongest signs of disequilibrium.

Line, Michael R.; Yung, Y. L.

2013-10-01

118

The greenhouse effect of planetary atmospheres  

Microsoft Academic Search

Summary  The greenhouse effect of the atmosphere is the main factor of possible climate changes of anthropogenic origin. The growing\\u000a pollution of the atmosphere leads to an increase of the concentration of such gaseous components as sulphur and carbon dioxides,\\u000a carbon oxide, halocarbons, nitrous oxides, etc. Of great importance is also the consideration of the aerosols, both injected\\u000a directly into the

K. Ya. Kondratyev; N. I. Moskalenko

1980-01-01

119

Chemical Characterization of Extrasolar Super-Earths - Interiors, Atmospheres, and Formation Conditions  

NASA Astrophysics Data System (ADS)

Recent observations are allowing unprecedented measurements of masses and radii of low-mass transiting extrasolar planets, particularly super-Earths which are defined as planets with masses between 1 and 10 Earth masses. The observed masses, radii, and temperatures of super-Earths provide constraints on their interior structures, geophysical conditions, as well as their atmospheric compositions. Some of the most recently detected super-Earths span a wide gamut of possible compositions, from super-Mercuries and lava planets to water worlds with thick volatile envelopes. In this work, we report joint constraints on the interior and atmospheric compositions of several super-Earths and discuss their possible formation scenarios using new and comprehensive hybrid models of their interiors, non-gray atmospheres, and formation conditions. Our model constraints are based on the masses and visible radii, as well as the latest infrared measurements of transmission and emission spectrophotometry where available, in addition to revised estimates of the stellar parameters. We will present a comparative analysis of several transiting super-Earths currently known and will discuss in detail two super-Earths (GJ 1214b and 55 Cancri e) which have atmospheric data available and which represent two distinct end members in the thermo-chemical phase space of super-Earth conditions. We will also discuss the implications of our results for the diversity of geochemical and geophysical conditions on super-Earths. We will conclude with comments on new observational, theoretical, and experimental efforts that are critical to detailed characterization of super-Earths.

Madhusudhan, Nikku; Lee, K.; Uts, I.; Mousis, O.

2013-01-01

120

Understanding the formation and composition of hazes in planetary atmospheres that contain carbon monoxide  

NASA Astrophysics Data System (ADS)

Measurements from the Cassini Plasma Spectrometer (CAPS) have revealed the presence of molecules in Titan's ionosphere with masses in excess of hundreds of amu. Negative ions with mass/charge (m/z) up to 10,000 amu/q [1] and positive ions with m/z up to 400 amu/q [2] have been detected. CAPS has also observed O+ flowing into Titan's upper atmosphere [3], which appears to originate from Enceladus and is likely the source of oxygen bearing molecules in Titan's atmosphere [4]. The observed O+ is deposited in the region now known to contain large organic molecules. A recent Titan atmosphere simulation experiment has shown that incorporation of oxygen into Titan aerosol analogues results in the formation of all five nucleotide bases and the two smallest amino acids, glycine and alanine [5]. Similar chemical processes may have occurred in the atmosphere of the early Earth, or in the atmospheres of extrasolar planets; atmospheric aerosols may be an important source of the building blocks of life. Atmospheric aerosols play an important role in determining the radiation budget of an atmosphere and can also provide a wealth of organic material to the surface. The presence of atmospheric aerosols has been invoked to explain the relatively featureless spectrum of HD 189773b, including the lack of predicted atmospheric Na and K spectral lines [9]. The majority of the O+ precipitating into Titan's atmosphere forms CO (O(3P)+CH3 -> CO+H2+H) [4]. CO has also been detected in the atmospheres of a number of exoplanets including HD 189733b, HD 209458b, and WASP-12b [6-8]. It is therefore important to understand the role CO plays in the formation and composition of hazes in planetary atmospheres. Using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) (see e.g. [10]) we have obtained in situ composition measurements of aerosol particles (so-called "tholins") produced in N2/CH4/CO gas mixtures subjected to either FUV radiation (deuterium lamp, 115-400 nm) or a spark discharge for a range of initial CO mixing ratios. A comparison of the composition of tholins produced using the two different energy sources will be presented. The effect of variation of CO mixing ratio on aerosol production and composition will also be discussed.

Hörst, S. M.; Yoon, Y. H.; Hicks, R. K.; Tolbert, M. A.

2012-09-01

121

Conservation of total escape from hydrodynamic planetary atmospheres  

NASA Astrophysics Data System (ADS)

Atmosphere escape is one key process controlling the evolution of planets. However, estimating the escape rate in any detail is difficult because there are many physical processes contributing to the total escape rate. Here we show that as a result of energy conservation the total escape rate from hydrodynamic planetary atmospheres where the outflow remains subsonic is nearly constant under the same stellar XUV photon flux when increasing the escape efficiency from the exobase level, consistent with the energy-limited escape approximation. Thus the estimate of atmospheric escape in a planet's evolution history can be greatly simplified.

Tian, Feng

2013-10-01

122

Clouds in the atmospheres of extrasolar planets. II. Thermal emission spectra of Earth-like planets influenced by low and high-level clouds  

NASA Astrophysics Data System (ADS)

Aims: We study the impact of multi-layered clouds (low-level water and high-level ice clouds) on the thermal emission spectra of Earth-like planets orbiting different types of stars. Clouds have an important influence on such planetary emission spectra due to their wavelength dependent absorption and scattering properties. We also investigate the influence of clouds on the ability to derive information about planetary surface temperatures from low-resolution spectra. Methods: We use a previously developed parametric cloud model based on observations in the Earth's atmosphere, coupled to a one-dimensional radiative-convective steady state climate model. This model is applied here to study the effect of clouds on the thermal emission spectra of Earth-like extrasolar planets in dependence of the type of central star. Results: The presence of clouds lead in general to a decrease of the planetary IR spectrum associated with the dampening of spectral absorption features such as the 9.6 ?m absorption band of O3 for example. This dampening is not limited to absorption features originating below the cloud layers but was also found for features forming above the clouds. When only single cloud layers are considered, both cloud types exhibit basically the same effects on the spectrum but the underlying physical processes are clearly different. For model scenarios where multi-layered clouds have been considered with coverages which yield mean Earth surface temperatures, the low-level clouds have only a small influence on the thermal emission spectra. In these cases the major differences are caused by high-level ice clouds. The largest effect was found for a planet orbiting the F-type star, where no absorption features can be distinguished in the low-resolution emission spectrum for high cloud coverages. However, for most central stars, planetary atmospheric absorption bands are present even at high cloud coverages. Clouds also affect the derivation of surface temperatures from low-resolution spectra when fitting black-body radiation curves to the spectral shape of the IR emission spectra. With increasing amount of high-level clouds the derived temperatures increasingly under-estimate the real planetary surface temperatures. Consequently, clouds can alter significantly the measured apparent temperature of a planet as well as the detectability of the characteristic spectral signatures in the infrared. Therefore, planets with observationally derived somewhat lower surface temperatures should not be discarded too quickly from the list of potential habitable planets before further investigations on the presence of clouds have been made.

Kitzmann, D.; Patzer, A. B. C.; von Paris, P.; Godolt, M.; Rauer, H.

2011-07-01

123

A Department of Atmospheric and Planetary Sciences at Hampton University  

NASA Astrophysics Data System (ADS)

With this presentation we discuss the status of plans for a Department of Atmospheric and Planetary Sciences at Hampton University. Hampton University is a privately endowed, non-profit, non-sectarian, co-educational, and historically black university with 38 baccalaureate, 14 masters, and 4 doctoral degree programs. The graduate program in physics currently offers advanced degrees with concentration in Atmospheric Science. The 10 students now enrolled benefit substantially from the research experience and infrastructure resident in the university's Center for Atmospheric Sciences (CAS), which is celebrating its tenth anniversary. Promoting a greater diversity of participants in geosciences is an important objective for CAS. To accomplish this, we require reliable pipelines of students into the program. One such pipeline is our undergraduate minor in Space, Earth, and Atmospheric Sciences (SEAS minor). This minor concentraton of study is contributing to awareness of geosciences on the Hampton University campus, and beyond, as our students matriculate and join the workforce, or pursue higher degrees. However, the current graduate program, with its emphasis on physics, is not necessarily optimal for atmospheric scientists, and it limits our ability to recruit students who do not have a physics degree. To increase the base of candidate students, we have proposed creation of a Department of Atmospheric and Planetary Sciences, which could attract students from a broader range of academic disciplines. The revised curriculum would provide for greater concentration in atmospheric and planetary sciences, yet maintain a degree of flexibility to allow for coursework in physics or other areas to meet the needs of individual students. The department would offer the M.S. and Ph.D. degrees, and maintain the SEAS minor. The university's administration and faculty have approved our plan for this new department pending authorization by the university's board of trustees, which will consider the matter during their October, 2006 meeting.

Paterson, W. R.; McCormick, M. P.; Russell, J. M.; Anderson, J.; Kireev, S.; Loughman, R. P.; Smith, W. L.

2006-12-01

124

Characterizing a Newly-Found Extrasolar Planet  

NASA Astrophysics Data System (ADS)

We propose to observe transits of the newly-discovered extrasolar planet TRES-1 using {1} ACS/HRC to obtain precise time-series photometry of the transit, and {2} NICMOS to measure the strength of water vapor absorption in the planetary atmosphere. The visible light curve will permit an accurate estimate of the planet's diameter by resolving uncertainty concerning the diameter of the parent star, and the water vapor observation can be used to test models of the structure, clouds and composition in the planet's upper atmosphere.

Brown, Timothy

2004-07-01

125

A spectrum of an extrasolar planet.  

PubMed

Of the over 200 known extrasolar planets, 14 exhibit transits in front of their parent stars as seen from Earth. Spectroscopic observations of the transiting planets can probe the physical conditions of their atmospheres. One such technique can be used to derive the planetary spectrum by subtracting the stellar spectrum measured during eclipse (planet hidden behind star) from the combined-light spectrum measured outside eclipse (star + planet). Although several attempts have been made from Earth-based observatories, no spectrum has yet been measured for any of the established extrasolar planets. Here we report a measurement of the infrared spectrum (7.5-13.2 microm) of the transiting extrasolar planet HD 209458b. Our observations reveal a hot thermal continuum for the planetary spectrum, with an approximately constant ratio to the stellar flux over this wavelength range. Superposed on this continuum is a broad emission peak centred near 9.65 microm that we attribute to emission by silicate clouds. We also find a narrow, unidentified emission feature at 7.78 microm. Models of these 'hot Jupiter' planets predict a flux peak near 10 microm, where thermal emission from the deep atmosphere emerges relatively unimpeded by water absorption, but models dominated by water fit the observed spectrum poorly. PMID:17314975

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

2007-02-22

126

Formation of Charge Layers in the Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

This section focuses on the physical phenomena, leading to large-scale space-charge and electric field generation (electric dynamo) in the planetary atmospheres, and ways of their theoretical description. The main attention is paid to charge-layer formation in atmospheres. Under terrestrial conditions, a problem of charge-layer formation in the atmosphere is important from the viewpoint of both thunderstorm and fair weather electricity. It is important also for the problems of intense layer generation under perturbed ionization conditions, charge layer formation over deserts, high field generation in the mesosphere etc. On the other hand, charge-layer treatment allows verifying electrification theories being applied to more or less simple 1D conditions such as the electrode effect, cloud screening layers, long-term charge layers in mesoscale convective systems. The paper reviews the results of recent research in this field. General conditions of the electro-hydro-dynamic description and their applications to the planetary atmospheres are discussed in terms of the Debye length, mean free path length of charged particles, Langmuir frequency and electrical conductivity. In terms of electrostatic interaction energy, it is found that three phases for charge carriers co-exist in strongly electrified clouds in the Earth's atmosphere. Crucial role of turbulent motion of conducting media for electric dynamo realization is revealed. The results of recent research in the modeling of the electrode effect, fog electrodynamics, screening layers in clouds and aerosol/dust structures, long-term charge layers in mesoscale convective systems are presented. Nonlinear solutions, demonstrating the formation of charge layers in planetary atmospheres, are examined.

Mareev, Evgeny A.

127

Formation of Charge Layers in the Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

This section focuses on the physical phenomena, leading to large-scale space-charge and electric field generation (electric dynamo) in the planetary atmospheres, and ways of their theoretical description. The main attention is paid to charge-layer formation in atmospheres. Under terrestrial conditions, a problem of charge-layer formation in the atmosphere is important from the viewpoint of both thunderstorm and fair weather electricity. It is important also for the problems of intense layer generation under perturbed ionization conditions, charge layer formation over deserts, high field generation in the mesosphere etc. On the other hand, charge-layer treatment allows verifying electrification theories being applied to more or less simple 1D conditions such as the electrode effect, cloud screening layers, long-term charge layers in mesoscale convective systems. The paper reviews the results of recent research in this field. General conditions of the electro-hydro-dynamic description and their applications to the planetary atmospheres are discussed in terms of the Debye length, mean free path length of charged particles, Langmuir frequency and electrical conductivity. In terms of electrostatic interaction energy, it is found that three phases for charge carriers co-exist in strongly electrified clouds in the Earth’s atmosphere. Crucial role of turbulent motion of conducting media for electric dynamo realization is revealed. The results of recent research in the modeling of the electrode effect, fog electrodynamics, screening layers in clouds and aerosol/dust structures, long-term charge layers in mesoscale convective systems are presented. Nonlinear solutions, demonstrating the formation of charge layers in planetary atmospheres, are examined.

Mareev, Evgeny A.

2008-06-01

128

Dynamics and stability of telluric planets within the habitable zone of extrasolar planetary systems. Numerical simulations of test particles within the HD 4208 and HD 70642 systems  

NASA Astrophysics Data System (ADS)

Aims: We study gravitational perturbation effects of observed giant extrasolar planets on hypothetical Earth-like planets in the context of the three-body problem. This paper considers a large parameter survey of different orbital configuration of two extrasolar giant planets (HD 70642b and HD 4208b) and compares their dynamical effect on Earth-mass planetary orbits initially located within the respective habitable terrestrial region. We are interested in determining giant-planet orbit (and mass) parameters that favor the condition to render an Earth-mass planet to remain on a stable and bounded orbit within the continuous habitable zone. Methods: We applied symplectic numerical integration techniques to studying the short and long term time evolution of hypothetical Earth-mass planets that are treated as particles. In addition, we adopt the MEGNO technique to obtain a complete dynamical picture of the terrestrial phase space environment. Both multi-particle and single-particle simulations were performed to follow an Earth-mass planet in the habitable region and its subsequent long term evolution. Results: Our numerical simulations show that giant planets should be on circular orbits to minimize the perturbative effect on terrestrial orbits. The orbit eccentricity (and hence proximity) is the most important orbital parameter of dynamical significance. The most promising candidate for maintaining an Earth-mass planet on a stable and bounded orbit well-confined to the continuous habitable zone is HD 70642b. Even the large planetary mass of HD 70642b renders an Earth-mass planet habitable during the complete lifetime of the host star. The results allow us to extrapolate similar observed systems and points the necessity further constraining the uncertainty range in giant planet orbital eccentricity by future follow-up observations.

Hinse, T. C.; Michelsen, R.; Jørgensen, U. G.; Go?dziewski, K.; Mikkola, S.

2008-09-01

129

Solar photo rates for planetary atmospheres and atmospheric pollutants  

Microsoft Academic Search

Unattenuated solar photo rate coefficients and excess energies for dissociation, ionization, and dissociative ionization are presented for atomic and molecular species that have been identified or are suspected to exist in the atmospheres of planets, satellites (moons), comets, or as pollutants in the Earth atmosphere. The branching ratios and cross sections with resonances have been tabulated to the greatest detail

W. F. Huebner; J. J. Keady; S. P. Lyon

1992-01-01

130

Dications and thermal ions in planetary atmospheric escape  

NASA Astrophysics Data System (ADS)

In the recent years, the presence of dications in the atmospheres of Mars, Venus, Earth and Titan has been modeled and assessed. These studies also suggested that these ions could participate to the escape of the planetary atmospheres because a large fraction of them is unstable and highly energetic. When they dissociate, their internal energy is transformed into kinetic energy which may be larger than the escape energy. The goal of this study is to assess the impact of the doubly-charged ions in the escape of CO2-dominated planetary atmospheres and to compare it to the escape of thermal photo-ions. We solve a Boltzmann transport equation at daytime taking into account the dissociative states of CO2++ for a simplified single constituent atmosphere of a case-study planet. We compute the escape of fast ions using a Beer-Lambert approach. We study three test-cases. On a Mars-analog planet in today's conditions, we retrieve the measured electron escape flux. When comparing the two mechanisms (i.e. excluding solar wind effects, sputtering, etc.), the escape due to the fast ions issuing from the dissociation of dications may account for up to 6% of the total and the escape of thermal ions for the remaining. We show that these two mechanisms cannot explain the escape of the atmosphere since the magnetic field vanished and even contribute only marginally to this loss. We show that with these two mechanisms, the atmosphere of a Mars analog planet would empty in another giga years and a half. At Venus orbit, the contribution of the dications in the escape rate is negligible. When simulating the hot Jupiter HD 209458 b, the two processes cannot explain the measured escape flux of C+. This study shows that the dications may constitute a source of the escape of planetary atmospheres which had not been taken into account until now. This source, although marginal, is not negligible. The influence of the photoionization is of course large, but cannot explain alone the loss of Mars' atmosphere nor the atmospheric escape of HD 209458 b.

Lilensten, J.; Simon Wedlund, C.; Barthélémy, M.; Thissen, R.; Ehrenreich, D.; Gronoff, G.; Witasse, O.

2013-01-01

131

The Sodium Hydride Line Opacity for Brown Dwarf and Extra-solar Giant Planet Atmospheres  

NASA Astrophysics Data System (ADS)

Atomic sodium is an important opacity in the spectra of brown dwarfs and is the only atmospheric constituent to date that has been detected in an extrasolar giant planet (EGP). For temperatures between ˜1000 and 2000 K, NaH and NaCl are the next most abundant sodium species (Lodders, 1999, ApJ, 519, 793). Due to the lack of opacity data for these molecules, they have not been considered in brown dwarf and EGP synthetic spectra models. In this work, we consider NaH and present comprehensive theoretical molecular line lists for rovibrational transitions in the ground X state and for the electronic transition between the A and X states. The list contains the transition energies and oscillator strengths for all allowed rotational and vibrational transitions. The calculations use hybrid potential curves based on experimental data, the theoretical X state potential and dipole moment function of Taylor & Newman (2003, J. Chem. Phys., 118, 8770), and the theoretical A state potential and X-A transition moment function of Leininger et al. (2000, J. Phys. B, 33, 1805). Using the Numerov-Cooley method, we find that there are 860 and 1824 rovibrational levels in the X and A states, respectively, which give rise to a large number of rotational transitions. Pure rotational, rovibrational, and A<-X electronic LTE spectra are presented for temperatures typical of brown dwarfs and EGPs. The bandheads occur at 8.8 ? and 3990 Å for the fundamental vibrational and A<-X electronic transitions, respectively. This work was supported in part by the NSF REU Program at UGA and NASA grant NAG5-10551.

Horvath, A.; Stancil, P. C.; Taylor, B. K.; Leininger, T.; Gadéa, F. X.

2003-12-01

132

Two-Way Atmospheric Radio Occultation: a Powerful New Technique For Probing Tenuous Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The Radio Science Atmospheric Occultation (RSAO) technique has a history of producing excellent science results for a wide range of denser planetary atmospheres. Overwhelmingly, the specific technique used so far has been the ``downlink" technique, whereby a spacecraft transmits one or more USO-referenced signals through a planetary atmosphere to a ground station, where the signals are referenced to an extremely stable oscillator and recorded for later data reduction. Doppler signatures and phase perturbations recorded in the data yield vertical profiles of ionospheric electron densities, and neutral atmospheric densities from which temperature-pressure profiles can be inferred. Results from occultations of tenuous atmospheres (surface pressures of a few microbars) are much sparser, partly due to not encountering many such bodies, and partly to limitations associated with the downlink RSAO method. We will discuss a new RSAO technique, ``Two-way atmospheric radio occultation", applicable to bodies with tenuous atmospheres such as Triton, Pluto, and possibly Io and Charon. Similar to radio occultation solar conjunction experiments, it relies on the small perturbations from a tenuous atmosphere, and the extreme stability of ground-based frequency references for both the initial transmitted signal and the information-carrying returned signal. The high-power uplink signals (two widely-separated frequencies are best) pass through the subject atmosphere, are received and transponded at the spacecraft, then pass again through the atmosphere and back to the ground station. Using the ground-based oscillator for both the initial and final frequency references, and doubling the amplitude of the perturbations induced by the planetary atmosphere, yields a far higher SNR than one-way techniques. This work was performed at the Jet Propulsion Laboratory / California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Spilker, T. R.; Rappaport, N. J.; Archer, E. D.

2003-05-01

133

An approach for the search of extra-solar system planets taking advantage of the simultaneous wide spectral range and high resolution of a future planetary observatory in earth orbit  

NASA Astrophysics Data System (ADS)

A new observational approach to the search for extra-solar planetary systems is presented which is based on high resolution spectroscopy, high coronographic efficiency, and long integration time. It is proposed to look for maxima in the cross-correlation function between the spectra of selected stars and their surrounding space. The Orbiting Planetary Telescope mission should be capable of meeting the following requirements: high rejection rate of the direct flux from the central star by coronographic techniques and the simultaneous access to a wide spectral range and a high spectral resolution.

Bruston, P.

1992-11-01

134

Composition/Structure/Dynamics of comet and planetary satellite atmospheres  

NASA Astrophysics Data System (ADS)

This research program addresses two cases of tenuous planetary atmospheres: comets and Io. The comet atmospheric research seeks to analyze a set of spatial profiles of CN in comet Halley taken in a 7.4-day period in April 1986; to apply a new dust coma model to various observations; and to analyze observations of the inner hydrogen coma, which can be optically thick to the resonance scattering of Lyman-alpha radiation, with the newly developed approach that combines a spherical radiative transfer model with our Monte Carlo H coma model. The Io research seeks to understand the atmospheric escape from Io with a hybrid-kinetic model for neutral gases and plasma given methods and algorithms developed for the study of neutral gas cometary atmospheres and the earth's polar wind and plasmasphere. Progress is reported on cometary Hydrogen Lyman-alpha studies; time-series analysis of cometary spatial profiles; model analysis of the dust comae of comets; and a global kinetic atmospheric model of Io.

Combi, Michael R.

1995-12-01

135

On the Insignificance of Photochemical Hydrocarbon Aerosols in the Atmospheres of Close-in Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

The close-in extrasolar giant planets (CEGPs) reside in irradiated environments much more intense than that of the giant planets in our solar system. The high UV irradiance strongly influences their photochemistry, and the general current view believed that this high UV flux will greatly enhance photochemical production of hydrocarbon aerosols. In this Letter, we investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find that the abundances of hydrocarbons in the atmospheres of CEGPs are significantly less than that of Jupiter except for models in which the CH4 abundance is unreasonably high (as high as CO) for the hot (effective temperatures >~1000 K) atmospheres. Moreover, the hydrocarbons will be condensed out to form aerosols only when the temperature-pressure profiles of the species intersect with the saturation profiles-a case almost certainly not realized in the hot CEGPs' atmospheres. Hence our models show that photochemical hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon aerosols in their atmospheres that are responsible for strong absorption shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon aerosols in the atmospheres of CEGPs rules out one class of models with low albedos and featureless spectra shortward of 600 nm.

Liang, Mao-Chang; Seager, Sara; Parkinson, Christopher D.; Lee, Anthony Y.-T.; Yung, Yuk L.

2004-04-01

136

Characterization and evolution of distant planetary atmospheres using stellar occultations  

NASA Astrophysics Data System (ADS)

Ground-based or near-Earth (e.g., HST) stellar occultations of every atmosphere in our solar system has been observed: Venus, Mars, Jupiter, Saturn, Titan, Uranus, Neptune, Triton, and Pluto [1]. These observations probe the atmospheres at roughly 0.1 to 100 microbar. I will talk about three aspects of stellar occultations: one-dimensional vertical profiles of the atmosphere, two- or three-dimensional atmospheric states, and the time evolution of atmosphere. In all three, I will draw on recent observations, with an emphasis on Pluto. Occultations are particularly important for the study of Pluto's atmosphere, which is impossible to study with imaging, and extremely difficult to study with spectroscopy. It was discovered by stellar occultation in 1988 [2]. No subsequent Pluto occultations were observed until two events in 2002 [3]. Pluto is now crossing the galactic plane, and there have been several additional occultations observed since 2006. These include a high signal-to-noise observation from the Anglo Australian Observatory in 2006 [4] (Fig 1), densely spaced visible and infrared observations of Pluto's upper atmosphere from telescopes in the US and Mexico in March, 2007 [5] (Fig. 2), and a dualwavelength central flash observation from Mt. John in July, 2007 [6] (Fig 3). The flux from a star occulted by an atmosphere diminishes primarily due to the increase in refraction with depth in the atmosphere, defocusing the starlight, although absorption and tangential focusing can also contribute. Because the atmospheric density, to first order, follows an exponential, it is feasible to derive a characteristic pressure and temperature from isothermal fits to even low-quality occultation light curves. Higher quality light curves allow fits with more flexible models, or light curve inversions that derive temperatures limited by the resolution of the data. These allow the derivation of one-dimensional profiles of temperature and pressure vs. altitude, which are critical for understanding the energy balance in upper atmospheres, interpreting thermal emission, and studying dynamics. These vertical profiles include small-scale fluctuations generally associated with gravity waves. While the 1988 Pluto occultation light curve was remarkably smooth, more recent Pluto occultations show spikes indicative of these small-scale dynamics. When an atmospheric occultation is observed from several sites, or when a single site is near enough to the shadow center to observe solar flux refracted from multiple locations in the occulting atmosphere, it is possible to study the two- or three-dimensional structure of an atmosphere. The simplest example is the oblateness of the atmosphere derived from the shape of an isobar [7], but more complex analyses are also possible. A comparison of the temperatures at different latitudes or local times of day can shed light on the relative importance of radiative equilibrium and dynamics to the energetics of an atmosphere, as has been done for the 2006 June 12 occultation by Pluto [4]. Closely spaced sites can be used to derive the two-dimensional shape and aspect ratio of temperature and density fluctuations [5,8], aiding the identification of the generating sources of these fluctuations. Occultation observations over a long time span are used to study the long-term evolution of an atmosphere. Both Triton and Pluto have shown large changes in their pressures since the late 1980's that is almost certainly related to changes in the temperature of their surface ices. The temperatures in the Uranian upper atmosphere increased before the previous solstice, and reverted to cooler temperatures a decade later, perhaps indicative of adiabatic cooling [9]. Recent improvements in astrometric catalogs, occultation-capable cameras (with low read noise, high readout rates, and little or no dead time), and easy access to accurate timing can greatly improve the quality, spatial sampling, and frequency of occultations by planetary atmospheres.

Young, L. A.

2008-09-01

137

Theory for the Secondary Eclipse Fluxes, Spectra, Atmospheres, and Light Curves of Transiting Extrasolar Giant Planets  

Microsoft Academic Search

We have created a general methodology for calculating the wavelength-dependent light curves of close-in extrasolar giant planets (EGPs) as they traverse their orbits. Focusing on the transiting EGPs HD 189733b, TrES-1, and HD 209458b, we calculate planet\\/star flux ratios during secondary eclipse and compare them with the Spitzer data points obtained so far in the mid-infrared. We introduce a simple

A. Burrows; D. Sudarsky; I. Hubeny

2006-01-01

138

The HARPS search for southern extra-solar planets. XXVIII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems  

NASA Astrophysics Data System (ADS)

Context. Low-mass extrasolar planets are presently being discovered at an increased pace by radial velocity and transit surveys, which opens a new window on planetary systems. Aims: We are conducting a high-precision radial velocity survey with the HARPS spectrograph, which aims at characterizing the population of ice giants and super-Earths around nearby solar-type stars. This will lead to a better understanding of their formation and evolution, and will yield a global picture of planetary systems from gas giants down to telluric planets. Methods: Progress has been possible in this field thanks in particular to the sub-m s-1 radial velocity precision achieved by HARPS. We present here new high-quality measurements from this instrument. Results: We report the discovery of a planetary system comprising at least five Neptune-like planets with minimum masses ranging from 12 to 25 M?, orbiting the solar-type star HD 10180 at separations between 0.06 and 1.4 AU. A sixth radial velocity signal is present at a longer period, probably caused by a 65-M? object. Moreover, another body with a minimum mass as low as 1.4 M? may be present at 0.02 AU from the star. This is the most populated exoplanetary system known to date. The planets are in a dense but still well separated configuration, with significant secular interactions. Some of the orbital period ratios are fairly close to integer or half-integer values, but the system does not exhibit any mean-motion resonances. General relativity effects and tidal dissipation play an important role to stabilize the innermost planet and the system as a whole. Numerical integrations show long-term dynamical stability provided true masses are within a factor ~3 from minimum masses. We further note that several low-mass planetary systems exhibit a rather "packed" orbital architecture with little or no space left for additional planets. In several cases, semi-major axes are fairly regularly spaced on a logarithmic scale, giving rise to approximate Titius-Bode-like (i.e. exponential) laws. These dynamical architectures can be interpreted as the signature of formation scenarios where type I migration and interactions between protoplanets play a major role. However, it remains challenging to explain the presence of so many Neptunes and super-Earths on non-resonant, well-ordered orbits within ~1-2 AU of the central star. Finally, we also confirm the marked dependence of planet formation on both metallicity and stellar mass. Very massive systems are all found around metal-rich stars more massive than the Sun, while low-mass systems are only found around metal-deficient stars less massive than the Sun. Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at La Silla Observatory (Chile), under program IDs 072.C-0488 and 183.C-0972.Radial velocities are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/528/A112

Lovis, C.; Ségransan, D.; Mayor, M.; Udry, S.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Correia, A. C. M.; Laskar, J.; Lo Curto, G.; Mordasini, C.; Pepe, F.; Queloz, D.; Santos, N. C.

2011-04-01

139

Planetary Magnetic Fields and Solar Forcing: Implications for Atmospheric Evolution  

NASA Astrophysics Data System (ADS)

The solar wind and the solar XUV/EUV radiation constitute a permanent forcing of the upper atmosphere of the planets in our solar system, thereby affecting the habitability and chances for life to emerge on a planet. The forcing is essentially inversely proportional to the square of the distance to the Sun and, therefore, is most important for the innermost planets in our solar system—the Earth-like planets. The effect of these two forcing terms is to ionize, heat, chemically modify, and slowly erode the upper atmosphere throughout the lifetime of a planet. The closer to the Sun, the more efficient are these process. Atmospheric erosion is due to thermal and non-thermal escape. Gravity constitutes the major protection mechanism for thermal escape, while the non-thermal escape caused by the ionizing X-rays and EUV radiation and the solar wind require other means of protection. Ionospheric plasma energization and ion pickup represent two categories of non-thermal escape processes that may bring matter up to high velocities, well beyond escape velocity. These energization processes have now been studied by a number of plasma instruments orbiting Earth, Mars, and Venus for decades. Plasma measurement results therefore constitute the most useful empirical data basis for the subject under discussion. This does not imply that ionospheric plasma energization and ion pickup are the main processes for the atmospheric escape, but they remain processes that can be most easily tested against empirical data. Shielding the upper atmosphere of a planet against solar XUV, EUV, and solar wind forcing requires strong gravity and a strong intrinsic dipole magnetic field. For instance, the strong dipole magnetic field of the Earth provides a “magnetic umbrella”, fending of the solar wind at a distance of 10 Earth radii. Conversely, the lack of a strong intrinsic magnetic field at Mars and Venus means that the solar wind has more direct access to their topside atmosphere, the reason that Mars and Venus, planets lacking strong intrinsic magnetic fields, have so much less water than the Earth? Climatologic and atmospheric loss process over evolutionary timescales of planetary atmospheres can only be understood if one considers the fact that the radiation and plasma environment of the Sun has changed substantially with time. Standard stellar evolutionary models indicate that the Sun after its arrival at the Zero-Age Main Sequence (ZAMS) 4.5 Gyr ago had a total luminosity of ?70% of the present Sun. This should have led to a much cooler Earth in the past, while geological and fossil evidence indicate otherwise. In addition, observations by various satellites and studies of solar proxies (Sun-like stars with different age) indicate that the young Sun was rotating more than 10 times its present rate and had correspondingly strong dynamo-driven high-energy emissions which resulted in strong X-ray and extreme ultraviolet (XUV) emissions, up to several 100 times stronger than the present Sun. Further, evidence of a much denser early solar wind and the mass loss rate of the young Sun can be determined from collision of ionized stellar winds of the solar proxies, with the partially ionized gas in the interstellar medium. Empirical correlations of stellar mass loss rates with X-ray surface flux values allows one to estimate the solar wind mass flux at earlier times, when the solar wind may have been more than 1000 times more massive. The main conclusions drawn on basis of the Sun-in-time-, and a time-dependent model of plasma energization/escape is that: 1. Solar forcing is effective in removing volatiles, primarily water, from planets,

Lundin, Rickard; Lammer, Helmut; Ribas, Ignasi

2007-03-01

140

Water Planetary and Cometary Atmospheres: H2O/HDO Transmittance and Fluorescence Models.  

National Technical Information Service (NTIS)

We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. Based on a greatly expanded set of s...

B. P. Bonev G. L. Villanueva M. A. DiSanti M. J. Mumma R. E. Novak R. J. Barber

2012-01-01

141

Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres.  

National Technical Information Service (NTIS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based radio astronomical observations can be used to infer abundances of microwave absorb...

P. G. Steffes

1998-01-01

142

Discovery of Planetary Systems With SIM.  

National Technical Information Service (NTIS)

We are witnessing the birth of a new observational science: the discovery and characterization of extrasolar planetary systems. In the past five years, over 70 extrasolar planets have been discovered by precision Doppler surveys, most by members of this S...

G. W. Marcy P. R. Butler S. Frink D. Fischer B. Oppenheimer D. G. Monet A. Quirrenbach J. D. Scargle

2004-01-01

143

Exploring Extrasolar Worlds Today and Tomorrow  

NASA Astrophysics Data System (ADS)

More than 440 extrasolar planets have been found since the discovery of 51 Peg b by (1995). The traditional field of planetology has thus expanded its frontiers to include planetary environments not represented in our Solar System. We expect that in the next five years space missions (CoRoT, Kepler, and GAIA) or ground-based detection techniques will both increase exponentially the number of new planets discovered and lower the present limit of a ˜1.9 Earth-mass object (Mayor et al. 2009). While the search for an Earth-twin orbiting a Sun-twin has been one of the major goals pursued by the exoplanet community in the past years, the possibility of sounding the atmospheric composition and structure of an increasing sample of exoplanets with current telescopes has opened new opportunities, unthinkable just a few years ago. As a result, it is possible now not only to determine the orbital characteristics of the new bodies, but moreover to study the exotic environments that lie tens of parsecs away from us. The analysis of the starlight not intercepted by the thin atmospheric limb of its planetary companion (transit spectroscopy), or of the light emitted/reflected by the exoplanet itself, will guide our understanding of the atmospheres and the surfaces of these extrasolar worlds in the next few years. We discuss in this manuscript the preliminary results obtained by interpreting current observations of the atmospheres of transiting Gas giants and Neptunes. While the full characterisation of an Earth-twin might require a technological leap, our understanding of large terrestrial planets (so called Super-Earths) orbiting bright, later-type stars is within reach by current space and ground telescopes.

Tinetti, G.; Griffith, C. A.

2010-10-01

144

SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems  

NASA Astrophysics Data System (ADS)

Continuing the extraordinary legacy of the Sloan Digital Sky Survey (SDSS), SDSS-III will use the wide-field spectroscopic capabilities of the APO 2.5-meter telescope to carry out four surveys on three scientific themes: dark energy and cosmological parameters; the structure, dynamics, and chemical evolution of the Milky Way; and the structure of giant planet systems. The Baryon Oscillation Spectroscopic Survey (BOSS) will measure redshifts of 1.5 million luminous red galaxies and Lyman-alpha absorption towards 160,000 high redshift quasars. By using the baryon acoustic oscillation scale as a physically calibrated ruler, BOSS will determine the cosmic distance scale with percent-level precision at z=0.2-0.7 and z=2-3. SEGUE-2, an extension of the SDSS-II program SEGUE (Sloan Extension for Galactic Understanding and Exploration), will obtain optical spectra of 350,000 stars (resolution R=2,000, typical S/N=25) to probe the kinematics and chemical evolution of the outer Galaxy. The APO Galactic Evolution Experiment (APOGEE) will use high-resolution (R=20,000, S/N=100) H-band spectroscopy to penetrate interstellar dust obscuration, measuring radial velocities and detailed elemental abundance patterns of 100,000 red giant stars across the full range of the Galactic bulge, bar, disk, and halo. Together, SEGUE-2 and APOGEE will provide a picture of the Milky Way that is unprecedented in scope, richness, and detail. The Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will use fiber-fed interferometric spectrographs to monitor the radial velocities of 11,000 bright stars with the precision and cadence needed to detect gas giant planets having orbital periods from several hours to two years. MARVELS will provide a critical statistical data set for testing theories of the formation and dynamical evolution of planetary systems. The six-year SDSS-III program (2008-2014) is international in scope, with participating institutions from the U.S., Europe, and Asia.

Weinberg, David H.; Beers, T.; Blanton, M.; Eisenstein, D.; Ford, H.; Ge, J.; Gillespie, B.; Gunn, J.; Klaene, M.; Knapp, G.; Kron, R.; Majewski, S.; Nichol, R.; O'Connell, R. W.; Raddick, M. J.; Rockosi, C.; Roe, N.; Schiavon, R.; Schneider, D.; Schlegel, D.; Skrutskie, M.; Snedden, S.; Strauss, M.; Wan, X.; White, M.

2007-12-01

145

Nonthermal atoms in planetary, satellite, and cometary atmospheres  

NASA Astrophysics Data System (ADS)

The effect of nonthermal atoms is investigated in planetary, satellite, and cometary atmospheres. In the Earth's lower thermosphere, it is demonstrated that nonthermal N(4S) and O(3P) atoms increase the peak NO density, bringing closer model and observational (108 cm-3) densities. However, they are insufficient to remove the total NO deficit and only result in a peak NO density of approximately 3 × 107 cm-3 at 105 km. The loss of nonthermal N(4S) atoms from Titan and Triton are found to be 9 × 1024 and 1.5 × 1024 N atoms s-1, respectively. We find that the observational estimates of Strobel et al. [1992] are consistent with our modeling of escape from Titan. The loss of O atoms from Mars by nonthermal processes is a vital part of understanding the H2O and CO2 budgets in respect to how the Martian atmosphere has evolved. Anderson and Hord [1971] inferred the H escape flux to be approximately 1.8 × 108 cm -2 s-1 from Mariner 6 and 7 ultraviolet data. McElroy et al. [1977] initially calculated an 0 atom escape rate that was approximately half the H escape rate. However, with more sophisticated modeling this result was shown to be an order of magnitude too large [Lammer and Bauer, 1991; Fox, 1993; Luhmann, 1997]. In this work, we demonstrate that the O escape rate due to dissociative recombination of O2 + can be in stoichiometric balance with H escape over a solar cycle. Observations of comet Hale-Bopp reveal a third type of tail consisting of neutral sodium atoms. Using a point source of atomic sodium to model the observed tail, the sodium production is found to be 3.5 × 10 25 atoms s-1. This result suggests that the source of the sodium is either from the nucleus or inner coma. The production rates of water and carbon monoxide near perihelion are found to be 1031 s-1 and 2.7 × 1030 s-1 , respectively. The abundance of observed Na in the tail is inconsistent with cosmic abundances, suggesting that the majority of the sodium is trapped in the comet nucleus or dust grains.

Kupperman, David Gerson

1999-08-01

146

Atmospheric Eclipses Now and Then: Probes of Stellar and Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Eclipses have played major roles in the development of Astronomy from antiquity up the present time. Lunar eclipses first showed that the Earth is sphere and solar eclipses revealed the Sun's chromosphere and corona. More recently a wealth of important astrophysical data has been gleamed from eclipsing binary stars and from planetary transits and occultations within our solar system and from transiting exoplanets orbiting other stars. Since the 1930s a small number of long-period eclipsing binary systems consisting of supergiant (or giant) primary stars and smaller hotter (typically B-type) companions - such as zeta Aur, 31 Cyg ,32 Cyg & VV Cep were found to undergo "atmospheric" eclipses. Atmospheric eclipses arise as the light of the small hot stars passes through the extended outer atmospheres of their K - M supergiant companions shortly before and after the primary eclipses. Also included with these systems is the 27-yr eclipsing binary eps Aur which consists of an F-supergiant and large, cool disk object. These stars are important astrophysical laboratories in which the atmospheric eclipses permit the extent and structure of the outer atmospheres of cool supergiants to be probed. In more recent years the powerful technique of atmospheric eclipses has been extended to short period white dwarf/cool star eclipsing binaries (e.g.-V471 Tau) as well as rare eclipsing binary systems with Cepheid components. Also during the last decade, the technique has been extended to transiting exoplanets in which the "transmission spectrum" of the exoplanet is studied as the light of star passes through the planet's atmosphere during the transit eclipse. These studies have revealed water vapor, CH4, CO2 and Na and other elements and molecules in exoplanet's atmospheres. An overview will be given with emphasis on some recent developments. This research is supported by grants from NSF/RUI and HST/NASA.

Guinan, Edward F.; Engle, S. G.; Recker, G.; Kullberg, E.

2013-07-01

147

The role of planetary waves in the atmosphere-ionosphere interactions  

NASA Astrophysics Data System (ADS)

The main mechanism of interaction between lower neutral atmosphere and ionosphere are the upward propagating atmospheric planetary waves. In the Institute of Solar-Terrestrial Physics RAS the experimental investigations of the interaction between different atmospheric layers from the stratosphere up to ionospheric E- and F-regions were carried out. The long-term database of some midlatitude upper atmosphere parameters was used (the horizontal thermosphere/ionosphere wind, the minimal vertically reflected from the ionosphere radio-frequency fmin, total ozone content, stratospheric temperature). The seasonal variations and significant non-zonality (longitudinal dependence) of the quasi-periodical structure were revealed. The influence of solar and geomagnetic activity periodicities from above and stratospheric thermo-baric field from below on the upper atmosphere processes is evaluated. In spite of significant changeability of planetary waves in the atmosphere-ionosphere system (from day to day, seasonal, from year to year, with solar cycle etc.) there are some similarities for the different atmospheric layers. The empirical model for the lower thermosphere wind field quasi-periodical structure was constructed. It is shown that increasing of planetary waves (wave-numbers 1 and 2) activity leads to the decreasing of the prevailing zonal wind velocity. We consider the atmosphere-ionosphere planetary waves as indicators of the complex disturbances in the Sun-Earth system and important element of upper atmosphere climate.

Kokourov, Victor D.; Vergasova, Galina V.; Kazimirovsky, Edward S.

2004-12-01

148

Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements completed under this grant (NAGW-533), have shown that the opacity from, SO2 under simulated Venus conditions is best described by a different lineshape than was previously used in theoretical predictions. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Steffes, Paul G.

1997-03-01

149

An extended upper atmosphere around the extrasolar planet HD209458b  

Microsoft Academic Search

The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed. Together with radial velocity measurements, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature, only the dense lower atmosphere of HD209458b

A. Vidal-Madjar; A. Lecavelier des Etangs; J.-M. Désert; G. E. Ballester; R. Ferlet; G. Hébrard; M. Mayor

2003-01-01

150

Microwave Remote Sensing of Planetary Atmospheres: From Staelin and Barrett to the Nasa Juno Mission  

Microsoft Academic Search

Early seminal contributions by Staelin helped initiate the field of microwave remote sensing as a key tool for the study of planetary atmospheres. Recent studies of the microwave emission from the neutral atmosphere of Venus have been used to identify the abundance and spatial distribution of microwave absorbing constituents such as sulfuric acid vapor and sulfur dioxide. A new mission

Paul G. Steffes; Bryan M. Karpowicz

2008-01-01

151

Robotic Airships for Exploration of Planetary Bodies with an Atmosphere: Autonomy Challenges  

Microsoft Academic Search

Robotic unmanned aerial vehicles have great potential as surveying and instrument deployment platforms in the exploration of planets and moons with an atmosphere. Among the various types of planetary aerovehicles proposed, lighter-than-atmosphere (LTA) systems are of particular interest because of their extended mission duration and long traverse capabilities. In this paper, we argue that the unique characteristics of robotic airships

Alberto Elfes; Samuel S. Bueno; Marcel Bergerman; Ely C. de Paiva; José R. Azinheira

2003-01-01

152

Extrasolar planets in the classroom  

NASA Astrophysics Data System (ADS)

The field of extrasolar planets is still, in comparison with other astrophysical topics, in its infancy. There have been about 300 or so extrasolar planets detected and their detection has been accomplished by various different techniques. Here we present a simple laboratory experiment to show how planets are detected using the transit technique. Following the simple analysis procedure describe we are able to determine the planetary radius to be 1.27 ± 0.20RJ which, within errors, agrees with the established value of 1.32 ± 0.25RJ.

George, Samuel J.

2011-07-01

153

Near-IR Spectrophotometry of 2MASSWJ 1207334-393254B - An Extra-Solar Planetary Mass Companion to a Young Brown Dwarf  

NASA Astrophysics Data System (ADS)

We propose to obtain "short" wavelength near-IR diagnostic and characterizing spectra of the very high probability candidate extra-solar giant planet {EGP} companion to 2MASSWJ 1207334-393254 {2M1207}, a young brown dwarf and TW Hydrae Association member. Recent NICMOS camera 1 multi-band photometric imaging of the companion candidate, 0.77" {54 AU projected} from 2M1207 - initially detected at longer wavelengths with VLT/NACO - implicate an object of several Jupiter masses based on cooling models of EGPs and the likely age of 2M1207 { 8 Myr}. Physical companionship of the EGP candidate with 2M1207 has been established at the 99.1% level of confidence via second-epoch NICMOS astrometric observations. Diagnostic spectra in the 0.8 to 1.9 micron region {unobtainable from the ground and overlapping the NICMOS imaging observations} will {a} critically inform on the physical nature of the EGP, {b} provide currently non-existing information to test/constrain theoretical models of EGP properties and evolution, and {c} unequivocally confirm the imaging of a bone fide EGP. Background light from 2M1207 would normally swamp the EGP spectrum with direct spectral imaging. To obviate this, we propose PSF-subtracted grism spectra of the EGP using 2M1207 as its own spectral template via two-orientation high-contrast image subtraction. The temporal stability of the HST+NICMOS PSF enables self-subtractions of targets at different field orientations resulting in contrast enhancements of 5 to 6 stellar magnitudes in the circumstellar background at 0.8" at these wavelengths. With the grism field oriented to place the EGP "above" and "below" 2M1207 {at two observational epochs} two independent spectra of the EGP will emerge from a difference image. This prototypical spectrum will serve to test and improve upon current models of young EGPs which predict flux suppression by molecular absorption in their atmospheres.

Schneider, Glenn

2005-07-01

154

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets. IV. The Effect of Cosmic Rays  

NASA Astrophysics Data System (ADS)

Cosmic rays provide an important source for free electrons in Earth's atmosphere and also in dense interstellar regions where they produce a prevailing background ionization. We utilize a Monte Carlo cosmic ray transport model for particle energies of 106 eV atmospheres of free-floating objects. The cosmic ray calculations are applied to DRIFT-PHOENIX model atmospheres of an example brown dwarf with effective temperature T eff = 1500 K, and two example giant gas planets (T eff = 1000 K, 1500 K). For the model brown dwarf atmosphere, the electron fraction is enhanced significantly by cosmic rays when the pressure p gas < 10-2 bar. Our example giant gas planet atmosphere suggests that the cosmic ray enhancement extends to 10-4-10-2 bar, depending on the effective temperature. For the model atmosphere of the example giant gas planet considered here (T eff = 1000 K), cosmic rays bring the degree of ionization to fe >~ 10-8 when p gas < 10-8 bar, suggesting that this part of the atmosphere may behave as a weakly ionized plasma. Although cosmic rays enhance the degree of ionization by over three orders of magnitude in the upper atmosphere, the effect is not likely to be significant enough for sustained coupling of the magnetic field to the gas.

Rimmer, P. B.; Helling, Ch.

2013-09-01

155

Seeing the Invisible: Educating the Public on Planetary Magnetic Fields and How they Affect Atmospheres  

NASA Astrophysics Data System (ADS)

Magnetic fields and charged particles are difficult for school children, the general public, and scientists alike to visualize. But studies of planetary magnetospheres and ionospheres have broad implications for planetary evolution, from the deep interior to the ancient climate, that are important to communicate to each of these audiences. This presentation will highlight the visualization materials that we are developing to educate audiences on the magnetic fields of planets and how they affect the atmosphere. The visualization materials that we are developing consist of simplified data sets that can be displayed on spherical projection systems and portable 3-D rigid models of planetary magnetic fields.

Fillingim, M. O.; Brain, D. A.; Peticolas, L. M.; Schultz, G.; Yan, D.; Guevara, S.; Randol, S.

2010-08-01

156

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets. V. Alfvén Ionization  

NASA Astrophysics Data System (ADS)

Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (>=10-7) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10-6-1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H2, or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks.

Stark, C. R.; Helling, Ch.; Diver, D. A.; Rimmer, P. B.

2013-10-01

157

PLANETARY CORE FORMATION WITH COLLISIONAL FRAGMENTATION AND ATMOSPHERE TO FORM GAS GIANT PLANETS  

SciTech Connect

Massive planetary cores ({approx}10 Earth masses) trigger rapid gas accretion to form gas giant planets such as Jupiter and Saturn. We investigate the core growth and the possibilities for cores to reach such a critical core mass. At the late stage, planetary cores grow through collisions with small planetesimals. Collisional fragmentation of planetesimals, which is induced by gravitational interaction with planetary cores, reduces the amount of planetesimals surrounding them, and thus the final core masses. Starting from small planetesimals that the fragmentation rapidly removes, less massive cores are formed. However, planetary cores acquire atmospheres that enlarge their collisional cross section before rapid gas accretion. Once planetary cores exceed about Mars mass, atmospheres significantly accelerate the growth of cores. We show that, taking into account the effects of fragmentation and atmosphere, initially large planetesimals enable formation of sufficiently massive cores. On the other hand, because the growth of cores is slow for large planetesimals, a massive disk is necessary for cores to grow enough within a disk lifetime. If the disk with 100 km sized initial planetesimals is 10 times as massive as the minimum mass solar nebula, planetary cores can exceed 10 Earth masses in the Jovian planet region (>5 AU).

Kobayashi, Hiroshi; Krivov, Alexander V. [Astrophysical Institute and University Observatory, Friedrich Schiller University, Schillergaesschen 2-3, 07745 Jena (Germany); Tanaka, Hidekazu, E-mail: hkobayas@astro.uni-jena.de [Institute of Low Temperature Science, Hokkaido University, Kita-Ku Kita 19 Nishi 8, Sapporo 060-0819 (Japan)

2011-09-01

158

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. II. DUST-INDUCED COLLISIONAL IONIZATION  

SciTech Connect

Observations have shown that continuous radio emission and also sporadic H{alpha} and X-ray emission are prominent in singular, low-mass objects later than spectral class M. These activity signatures are interpreted as being caused by coupling of an ionized atmosphere to the stellar magnetic field. What remains a puzzle, however, is the mechanism by which such a cool atmosphere can produce the necessary level of ionization. At these low temperatures, thermal gas processes are insufficient, but the formation of clouds sets in. Cloud particles can act as seeds for electron avalanches in streamers that ionize the ambient gas, and can lead to lightning and indirectly to magnetic field coupling, a combination of processes also expected for protoplanetary disks. However, the precondition is that the cloud particles are charged. We use results from DRIFT-PHOENIX model atmospheres to investigate collisional processes that can lead to the ionization of dust grains inside clouds. We show that ionization by turbulence-induced dust-dust collisions is the most efficient kinetic process. The efficiency is highest in the inner cloud where particles grow quickly and, hence, the dust-to-gas ratio is high. Dust-dust collisions alone are not sufficient to improve the magnetic coupling of the atmosphere inside the cloud layers, but the charges supplied either on grains or within the gas phase as separated electrons can trigger secondary nonlinear processes. Cosmic rays are likely to increase the global level of ionization, but their influence decreases if a strong, large-scale magnetic field is present as on brown dwarfs. We suggest that although thermal gas ionization declines in objects across the fully convective boundary, dust charging by collisional processes can play an important role in the lowest mass objects. The onset of atmospheric dust may therefore correlate with the anomalous X-ray and radio emission in atmospheres that are cool, but charged more than expected by pure thermal ionization.

Helling, Ch.; Jardine, M. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom); Mokler, F., E-mail: ch80@st-andrews.ac.uk [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany)

2011-08-10

159

PLATO: PLAnetary Transits and Oscillations of stars  

NASA Astrophysics Data System (ADS)

This decade is witnessing a rapid increase in our understanding of the nature of extra-solar planet systems and their host stars. Missions such as Corot and Kepler have confirmed that not only are extra-solar planets a common occurrence, but that multiple planetary systems are also the norm. Whilst there has been significant progress in discovery and to some extent understanding of extra solar planets and their host star(s), major questions remain as we seek to reveal the presence of extra-solar planets harbouring life. PLATO is a proposed ESA M3 mission which will revolutionise our understanding of extra-solar planets, through its discovery of planets around hundreds of thousands of stars, orders of magnitudes more than previously known. Its exquisite sensitivity will ensure that it detects planets to Earth masses and within the 'habitable' zone. PLATO will probe the interiors of both the host star(s) and their orbiting planetary systems. This presentation will describe the PLATO science yield: detecting Earth-sized planets in the habitable zone with known radii and masses, including planets orbiting solar-like stars; obtaining statistically significant numbers of characterized small planets at different orbits, around various star types; thus providing a set of well characterised small terrestrial planets around bright stars as constraints to planet formation theories and as targets for future atmosphere spectroscopy.

Rauer, Heike

2013-04-01

160

Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b  

SciTech Connect

Using the integral field spectrograph OSIRIS, on the Keck II telescope, broad near-infrared H and K-band spectra of the young exoplanet HR8799b have been obtained. In addition, six new narrow-band photometric measurements have been taken across the H and K bands. These data are combined with previously published photometry for an analysis of the planet's atmospheric properties. Thick photospheric dust cloud opacity is invoked to explain the planet's red near-IR colors and relatively smooth near-IR spectrum. Strong water absorption is detected, indicating a Hydrogen-rich atmosphere. Only weak CH{sub 4} absorption is detected at K band, indicating efficient vertical mixing and a disequilibrium CO/CH{sub 4} ratio at photospheric depths. The H-band spectrum has a distinct triangular shape consistent with low surface gravity. New giant planet atmosphere models are compared to these data with best fitting bulk parameters, T{sub eff} = 1100K {+-} 100 and log(g) = 3.5 {+-} 0.5 (for solar composition). Given the observed luminosity (log L{sub obs}/L{sub {circle_dot}} {approx} -5.1), these values correspond to a radius of 0.75 R{sub Jup{sub 0.12}{sup +0.17}} and mass {approx} 0.72 M{sub Jup{sub -0.6}{sup +2.6}} - strikingly inconsistent with interior/evolution models. Enhanced metallicity (up to {approx} 10 x that of the Sun) along with thick clouds and non-equilibrium chemistry are likely required to reproduce the complete ensemble of spectroscopic and photometric data and the low effective temperatures (< 1000K) required by the evolution models.

Barman, T S; Macintosh, B A; Konopacky, Q M; Marois, C

2011-03-21

161

The Extrasolar Planets Encyclopaedia  

NSDL National Science Digital Library

A full list of currently known Extrasolar Planets with frequently updated information on detection methods, current searches, and the Extrasolar Planets themselves. The site also includes information on reports and meetings concerning Extrasolar Planets.

Schneider, Jean

2005-06-07

162

New criterion for sediment suspension and wind-speed proxy in planetary atmospheres  

Microsoft Academic Search

Sediment suspension is a common and important phenomenon in planetary atmospheres. A widely-used suspension criterion, also a proxy boundary layer wind-speed indicator, was discredited by Mars Exploration Rover Mission results concerning sediment particle sizes in active surface bed forms. Parameterisation of a new dynamic suspension criterion based upon turbulent stress yields predicted suspension threshold conditions consistent with those inferred for

M. R. Leeder

2007-01-01

163

Laboratory Measurements and Modeling of Molecular Photoabsorption Cross Sections in the Ultraviolet for Planetary Atmospheres Applications  

Microsoft Academic Search

Our research program is dedicated to the measurement and modeling of vacuum ultraviolet and UV molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on molecular nitrogen, carbon dioxide, sulfur dioxide, and diatomic sulfur are in progress. N2: We focus on the measurement of line

Glenn Stark; P. L. Smith; B. R. Lewis; A. N. Heays; J. Pickering; R. Blackwell-Whitehead; D. Blackie

2008-01-01

164

The ultraviolet absorption spectrum of CO - Applications to planetary atmospheres  

NASA Astrophysics Data System (ADS)

Laboratory gas-phase photoabsorption cross sections of the CO Cameron 0-0 band and the underlying pseudocontinuum have been measured at a temperature of 147 K and pressures of about 200 mbar, conditions similar to ambient in various planetary and satellite stratospheres in the solar system. A theoretical modeling program has also been used to calculate the band's spectrum. Agreement between the theoretical and the experimental spectra is very good. Models suggest that the observations of the CO Cameron band using the Hubble Space Telescope will be straightforward for Mars, but marginal for Titan.

White, H. P.; Hua, X.-M.; Caldwell, J.; Chen, F. Z.; Judge, D. L.; Wu, C. Y. R.

1993-03-01

165

3.6 and 4.5 ?m Phase Curves and Evidence for Non-equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b  

NASA Astrophysics Data System (ADS)

We present new, full-orbit observations of the infrared phase variations of the canonical hot Jupiter HD 189733b obtained in the 3.6 and 4.5 ?m bands using the Spitzer Space Telescope. When combined with previous phase curve observations at 8.0 and 24 ?m, these data allow us to characterize the exoplanet's emission spectrum as a function of planetary longitude and to search for local variations in its vertical thermal profile and atmospheric composition. We utilize an improved method for removing the effects of intrapixel sensitivity variations and robustly extracting phase curve signals from these data, and we calculate our best-fit parameters and uncertainties using a wavelet-based Markov Chain Monte Carlo analysis that accounts for the presence of time-correlated noise in our data. We measure a phase curve amplitude of 0.1242% ± 0.0061% in the 3.6 ?m band and 0.0982% ± 0.0089% in the 4.5 ?m band, corresponding to brightness temperature contrasts of 503 ± 21 K and 264 ± 24 K, respectively. We find that the times of minimum and maximum flux occur several hours earlier than predicted for an atmosphere in radiative equilibrium, consistent with the eastward advection of gas by an equatorial super-rotating jet. The locations of the flux minima in our new data differ from our previous observations at 8 ?m, and we present new evidence indicating that the flux minimum observed in the 8 ?m is likely caused by an overshooting effect in the 8 ?m array. We obtain improved estimates for HD 189733b's dayside planet-star flux ratio of 0.1466% ± 0.0040% in the 3.6 ?m band and 0.1787% ± 0.0038% in the 4.5 ?m band, corresponding to brightness temperatures of 1328 ± 11 K and 1192 ± 9 K, respectively; these are the most accurate secondary eclipse depths obtained to date for an extrasolar planet. We compare our new dayside and nightside spectra for HD 189733b to the predictions of one-dimensional radiative transfer models from Burrows et al. and conclude that fits to this planet's dayside spectrum provide a reasonably accurate estimate of the amount of energy transported to the night side. Our 3.6 and 4.5 ?m phase curves are generally in good agreement with the predictions of general circulation models for this planet from Showman et al., although we require either excess drag or slower rotation rates in order to match the locations of the measured maxima and minima in the 4.5, 8.0, and 24 ?m bands. We find that HD 189733b's 4.5 ?m nightside flux is 3.3? smaller than predicted by these models, which assume that the chemistry is in local thermal equilibrium. We conclude that this discrepancy is best explained by vertical mixing, which should lead to an excess of CO and correspondingly enhanced 4.5 ?m absorption in this region. This result is consistent with our constraints on the planet's transmission spectrum, which also suggest excess absorption in the 4.5 ?m band at the day-night terminator.

Knutson, Heather A.; Lewis, Nikole; Fortney, Jonathan J.; Burrows, Adam; Showman, Adam P.; Cowan, Nicolas B.; Agol, Eric; Aigrain, Suzanne; Charbonneau, David; Deming, Drake; Désert, Jean-Michel; Henry, Gregory W.; Langton, Jonathan; Laughlin, Gregory

2012-07-01

166

3.6 AND 4.5 {mu}m PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b  

SciTech Connect

We present new, full-orbit observations of the infrared phase variations of the canonical hot Jupiter HD 189733b obtained in the 3.6 and 4.5 {mu}m bands using the Spitzer Space Telescope. When combined with previous phase curve observations at 8.0 and 24 {mu}m, these data allow us to characterize the exoplanet's emission spectrum as a function of planetary longitude and to search for local variations in its vertical thermal profile and atmospheric composition. We utilize an improved method for removing the effects of intrapixel sensitivity variations and robustly extracting phase curve signals from these data, and we calculate our best-fit parameters and uncertainties using a wavelet-based Markov Chain Monte Carlo analysis that accounts for the presence of time-correlated noise in our data. We measure a phase curve amplitude of 0.1242% {+-} 0.0061% in the 3.6 {mu}m band and 0.0982% {+-} 0.0089% in the 4.5 {mu}m band, corresponding to brightness temperature contrasts of 503 {+-} 21 K and 264 {+-} 24 K, respectively. We find that the times of minimum and maximum flux occur several hours earlier than predicted for an atmosphere in radiative equilibrium, consistent with the eastward advection of gas by an equatorial super-rotating jet. The locations of the flux minima in our new data differ from our previous observations at 8 {mu}m, and we present new evidence indicating that the flux minimum observed in the 8 {mu}m is likely caused by an overshooting effect in the 8 {mu}m array. We obtain improved estimates for HD 189733b's dayside planet-star flux ratio of 0.1466% {+-} 0.0040% in the 3.6 {mu}m band and 0.1787% {+-} 0.0038% in the 4.5 {mu}m band, corresponding to brightness temperatures of 1328 {+-} 11 K and 1192 {+-} 9 K, respectively; these are the most accurate secondary eclipse depths obtained to date for an extrasolar planet. We compare our new dayside and nightside spectra for HD 189733b to the predictions of one-dimensional radiative transfer models from Burrows et al. and conclude that fits to this planet's dayside spectrum provide a reasonably accurate estimate of the amount of energy transported to the night side. Our 3.6 and 4.5 {mu}m phase curves are generally in good agreement with the predictions of general circulation models for this planet from Showman et al., although we require either excess drag or slower rotation rates in order to match the locations of the measured maxima and minima in the 4.5, 8.0, and 24 {mu}m bands. We find that HD 189733b's 4.5 {mu}m nightside flux is 3.3{sigma} smaller than predicted by these models, which assume that the chemistry is in local thermal equilibrium. We conclude that this discrepancy is best explained by vertical mixing, which should lead to an excess of CO and correspondingly enhanced 4.5 {mu}m absorption in this region. This result is consistent with our constraints on the planet's transmission spectrum, which also suggest excess absorption in the 4.5 {mu}m band at the day-night terminator.

Knutson, Heather A. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Lewis, Nikole; Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Fortney, Jonathan J.; Laughlin, Gregory [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Burrows, Adam [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Cowan, Nicolas B. [CIERA, Northwestern University, Evanston, IL 60208 (United States); Agol, Eric [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Aigrain, Suzanne [Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom); Charbonneau, David; Desert, Jean-Michel [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Deming, Drake [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209 (United States); Langton, Jonathan, E-mail: hknutson@caltech.edu [Department of Physics, Principia College, 1 Maybeck Place, Elsah, IL 62028 (United States)

2012-07-20

167

Detecting tree-like multicellular life on extrasolar planets.  

PubMed

Over the next two decades, NASA and ESA are planning a series of space-based observatories to find Earth-like planets and determine whether life exists on these planets. Previous studies have assessed the likelihood of detecting life through signs of biogenic gases in the atmosphere or a red edge. Biogenic gases and the red edge could be signs of either single-celled or multicellular life. In this study, we propose a technique with which to determine whether tree-like multicellular life exists on extrasolar planets. For multicellular photosynthetic organisms on Earth, competition for light and the need to transport water and nutrients has led to a tree-like body plan characterized by hierarchical branching networks. This design results in a distinct bidirectional reflectance distribution function (BRDF) that causes differing reflectance at different sun/view geometries. BRDF arises from the changing visibility of the shadows cast by objects, and the presence of tree-like structures is clearly distinguishable from flat ground with the same reflectance spectrum. We examined whether the BRDF could detect the existence of tree-like structures on an extrasolar planet by using changes in planetary albedo as a planet orbits its star. We used a semi-empirical BRDF model to simulate vegetation reflectance at different planetary phase angles and both simulated and real cloud cover to calculate disk and rotation-averaged planetary albedo for a vegetated and non-vegetated planet with abundant liquid water. We found that even if the entire planetary albedo were rendered to a single pixel, the rate of increase of albedo as a planet approaches full illumination would be comparatively greater on a vegetated planet than on a non-vegetated planet. Depending on how accurately planetary cloud cover can be resolved and the capabilities of the coronagraph to resolve exoplanets, this technique could theoretically detect tree-like multicellular life on exoplanets in 50 stellar systems. PMID:21118020

Doughty, Christopher E; Wolf, Adam

2010-11-01

168

The Potential Feasibility of Chlorinic Photosynthesis on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

It is highly likely that the first convincing evidence of extrasolar life will arrive in the form of atmospheric absorption spectra. The modern search for life-bearing extrasolar planets emphasizes the potential detection of O2 and O3 absorption spectra in exoplanetary atmospheres as archetypal signatures of biology. However, oxygenic photosynthesis apparently failed to evolve independently more than once on Earth, and is thus unlikely to be reliably ubiquitous throughout the universe. Alternative evolutionary paths may yield planetary atmospheres tinted with the waste products of other dominant metabolisms, including potentially exotic biochemistries. This study examines the potential feasibility of one such exotic metabolism: chlorinic photosynthesis (CPS), defined as biologically-mediated halogenation of aqueous chloride to HClO, Cl2 or partially-oxidized intermediates (e.g. haloalkanes, haloacids, haloaromatics), coupled with photosynthetic CO2 fixation. This metabolic couple is feasible thermodynamically and appears to be geochemically plausible under approximately terrestrial conditions. This study hypothesizes that planetary biospheres dominated by CPS would develop atmospheres enriched with dihalogens and other halogenated compounds, evolve a highly oxidizing surface geochemical environment, and foster biological selection pressures favoring halogen resistance and eventual metazoan heterotrophy based on dihalogen and halocarbon respiration. Planets favoring the evolution of CPS would probably receive equivalent or greater surface UV flux than Earth did in the Paleoarchean (promoting abiotic photo-oxidation of aqueous halides, and establishing a strong biological selective pressure toward their accommodation), and would orbit stars having equivalent or greater bulk metallicities (promoting greater planetary halide abundances) relative to the Sun. Directed searches for such worlds should probably focus on A, F and G0 spectral class stars having bulk metallicities of +0.0 Dex or greater.

Haas, Johnson

2009-09-01

169

THERMO-RESISTIVE INSTABILITY OF HOT PLANETARY ATMOSPHERES  

SciTech Connect

The atmospheres of hot Jupiters and other strongly forced exoplanets are susceptible to a thermal instability in the presence of ohmic dissipation, weak magnetic drag, and strong winds. The instability occurs in radiatively dominated atmospheric regions when the ohmic dissipation rate increases with temperature faster than the radiative (cooling) rate. The instability domain covers a specific range of atmospheric pressures and temperatures, typically P {approx} 3-300 mbar and T {approx} 1500-2500 K for hot Jupiters, which makes it a candidate mechanism to explain the dayside thermal 'inversions' inferred for a number of such exoplanets. The instability is suppressed by high levels of non-thermal photoionization, in possible agreement with a recently established observational trend. We highlight several shortcomings of the instability treatment presented here. Understanding the emergence and outcome of the instability, which should result in locally hotter atmospheres with stronger levels of drag, will require global nonlinear atmospheric models with adequate MHD prescriptions.

Menou, Kristen [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

2012-07-20

170

Thermo-resistive Instability of Hot Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The atmospheres of hot Jupiters and other strongly forced exoplanets are susceptible to a thermal instability in the presence of ohmic dissipation, weak magnetic drag, and strong winds. The instability occurs in radiatively dominated atmospheric regions when the ohmic dissipation rate increases with temperature faster than the radiative (cooling) rate. The instability domain covers a specific range of atmospheric pressures and temperatures, typically P ~ 3-300 mbar and T ~ 1500-2500 K for hot Jupiters, which makes it a candidate mechanism to explain the dayside thermal "inversions" inferred for a number of such exoplanets. The instability is suppressed by high levels of non-thermal photoionization, in possible agreement with a recently established observational trend. We highlight several shortcomings of the instability treatment presented here. Understanding the emergence and outcome of the instability, which should result in locally hotter atmospheres with stronger levels of drag, will require global nonlinear atmospheric models with adequate MHD prescriptions.

Menou, Kristen

2012-07-01

171

Cosmic ray impact on extrasolar earth-like planets in close-in habitable zones.  

PubMed

Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 15% of the Earth's current magnetic moment. Therefore, close-in extrasolar planets seem not to be protected by extended Earth-like magnetospheres, and cosmic rays can reach almost the whole surface area of the upper atmosphere. Primary cosmic ray particles that interact with the atmosphere generate secondary energetic particles, a so-called cosmic ray shower. Some of the secondary particles can reach the surface of terrestrial planets when the surface pressure of the atmosphere is on the order of 1 bar or less. We propose that, depending on atmospheric pressure, biological systems on the surface of Earth-like extrasolar planets at close-in orbital distances can be strongly influenced by secondary cosmic rays. PMID:16225432

Griessmeier, J-M; Stadelmann, A; Motschmann, U; Belisheva, N K; Lammer, H; Biernat, H K

2005-10-01

172

The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems  

Microsoft Academic Search

Context. Low-mass extrasolar planets are presently being discovered at an\\u000aincreased pace by radial velocity and transit surveys, opening a new window on\\u000aplanetary systems. Aims. We are conducting a high-precision radial velocity\\u000asurvey with the HARPS spectrograph which aims at characterizing the population\\u000aof ice giants and super-Earths around nearby solar-type stars. This will lead\\u000ato a better understanding

C. Lovis; D. Ségransan; M. Mayor; S. Udry; W. Benz; J.-L. Bertaux; F. Bouchy; A. C. M. Correia; J. Laskar; G. Lo Curto; C. Mordasini; F. Pepe; D. Queloz; N. C. Santos

2010-01-01

173

The influence of forward-scattered light in transmission measurements of (exo)planetary atmospheres  

NASA Astrophysics Data System (ADS)

The transmission of light through a planetary atmosphere can be studied as a function of altitude and wavelength using stellar or solar occultations, giving often unique constraints on the atmospheric composition. For exoplanets, a transit yields a limb-integrated, wavelength-dependent transmission spectrum of an atmosphere. When scattering haze and/or cloud particles are present in the planetary atmosphere, the amount of transmitted flux not only depends on the total optical thickness of the slant light path that is probed, but also on the amount of forward-scattering by the scattering particles. Here, we present results of calculations with a three-dimensional Monte Carlo code that simulates the transmitted flux during occultations or transits. For isotropically scattering particles, like gas molecules, the transmitted flux appears to be well-described by the total atmospheric optical thickness. Strongly forward-scattering particles, however, such as commonly found in atmospheres of Solar System planets, can increase the transmitted flux significantly. For exoplanets, such added flux can decrease the apparent radius of the planet by several scale heights, which is comparable to predicted and measured features in exoplanet transit spectra. We performed detailed calculations for Titan's atmosphere between 2.0 and 2.8 ?m and show that haze and gas abundances will be underestimated by about 8% if forward-scattering is ignored in the retrievals. At shorter wavelengths, errors in the gas and haze abundances and in the spectral slope of the haze particles can be several tens of percent, also for other Solar System planetary atmospheres. We also find that the contribution of forward-scattering can be fairly well described by modelling the atmosphere as a plane-parallel slab. This potentially reduces the need for a full three-dimensional Monte Carlo code for calculating transmission spectra of atmospheres that contain forward-scattering particles.

de Kok, R. J.; Stam, D. M.

2012-11-01

174

Influence of Clouds on the Emission Spectra of Earth-like Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The climate of Earth-like planets results from the energy balance between absorbed starlight and radiative losses of heat from the surface and atmosphere to space. Clouds reflect sunlight back towards space, reducing the stellar energy available for heating the atmosphere (albedo effect), but also reduce radiative losses to space (greenhouse effect). Clouds also have a large effect on the emission spectra of planetary atmospheres, by either concealing the thermal emission from the surface or dampening the spectral features of molecules, which is, of course, also true for biomarkers (e.g., N2O and O3). We present first results on the impact of multi-layered clouds in the atmospheres of Earth-like extrasolar planets orbiting different types of central stars on the planetary IR emission spectra.

Kitzmann, D.; Patzer, A. B. C.; von Paris, P.; Godolt, M.; Grenfell, J. L.; Rauer, H.

2010-10-01

175

Some remarks on coherent structures out of chaos in planetary atmospheres and oceans.  

PubMed

In the context of planetary atmospheres and oceans, it is natural to define "coherent structures" as "long-lived," or "solitary," Rossby vortices. These can be described by the generalized Charney-Obukhov equation (in fluid dynamics) or the analogous generalized Hasegawa-Mima equation (in plasma physics). These two equations contain KdV-type nonlinearities which (together with the compensating dispersive spreading) determine the formation of the coherent structures and explain the clear-cut cyclonic/anticyclonic asymmetry observed experimentally in long-lived planetary Rossby vortices. Examples are given of natural vortices which are (and which are not) coherent structures. PMID:12780093

Nezlin, Mikhail V.

1994-06-01

176

Terrene Meteorites: Effects of Planetary Atmospheres on Ejecta Launch  

NASA Astrophysics Data System (ADS)

We show that if Earth's atmosphere were not a barrier to escape, Earth should be receiving a current flux of terrene meteorites (ejecta fragments from large recent Earth impacts that reached heliocentric orbit) that rivals the lunar and martian flux.

Gladman, B.; Chan, C.

2012-09-01

177

A Decade of Extrasolar Planets around Normal Stars  

NASA Astrophysics Data System (ADS)

1. Extrasolar planets: past, present, and future A. P. Boss; 2. The quest for very low-mass planets M. Mayor, F. Pepe, C. Lovis, D. Queloz and S. Udry; 3. Extrasolar planets: a galactic perspective I. N. Reid; 4. The Kepler Mission: Design, expected science results, opportunities to participate W. J. Borucki, D. Koch, G. Basri, T. Brown, D. Caldwell, E. Devore, E. Dunham, T. Gautier, J. Geary, R. Gilliland, A. Gould, S. Howell, J. Jenkins and D. Latham; 5. Observations of the atmospheres of extrasolar planets T. M. Brown, R. Alonso, M. Knölker, H. Rauer and W. Schmidt; 6. Planetary migration P. J. Armitage and W. K. M. Rice; 7. Observational constraints on dust disk lifetimes: implications for planet formation L. A. Hillenbrand; 8. The evolution of gas in disks J. Najita; 9. Planet formation J.J. Lissauer; 10. Core accretion-gas capture model for gas giant planet formation O. Hubickyj; 11. Gravitational instabilities in protoplanetary disks R. H. Durisen; 12. Conference summary: the quest for new worlds J. E. Pringle.

Livio, Mario; Sahu, Kailash; Valenti, Jeff

2011-04-01

178

Polarized light in planetary atmospheres for perpendicular directions  

NASA Astrophysics Data System (ADS)

A plane-parallel atmosphere with perpendicularly incident light or scattered light travelling in perpendicular directions is considered. It is shown on the basis of general geometrical arguments that substantial simplifications arise compared with situations in which no perpendicular directions are involved. The azimuth dependence of the radiation field is explicitly derived and shown to require only one or two terms in a Fourier series expansion. When the incident light illuminates the atmosphere perpendicularly, the scattered light travelling in perpendicular directions up and down can be described by matrices which have the same simple form as the scattering matrix of a volume-element has for strictly backward and forward scattering, respectively.

Hovenier, J. W.; de Hann, J. F.

1985-05-01

179

Investigating Earth's Atmospheric Electricity: a Role Model for Planetary Studies  

Microsoft Academic Search

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as ``central tenets'',

K. L. Aplin; R. G. Harrison; M. J. Rycroft

2008-01-01

180

Investigating Earth's Atmospheric Electricity: a Role Model for Planetary Studies  

Microsoft Academic Search

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as \\

K. L. Aplin; R. G. Harrison; M. J. Rycroft

2008-01-01

181

A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The action of an electric discharge on reduced gas mixtures such as H2O, CH4 and NH3 (or N2) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth’s atmosphere was likely not reducing, but was dominated by N2 and CO2. The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought.

Cleaves, H. James; Chalmers, John H.; Lazcano, Antonio; Miller, Stanley L.; Bada, Jeffrey L.

2008-04-01

182

Biological modulation of planetary atmospheres: The early Earth scenario  

NASA Astrophysics Data System (ADS)

The establishment and subsequent evolution of life on Earth had a profound impact on the chemical regime at the planet's surface and its atmosphere. A thermodynamic gradient was imposed on near-surface environments that served as the driving force for a number on important geochemical transformations. An example is the redox imbalance between the modern atmosphere and the material of the Earth's crust. Current photochemical models predict extremely low partial pressures of oxygen in the Earth's prebiological atmosphere. There is widespread consensus that any large-scale oxygenation of the primitive atmosphere was contingent on the advent of biological (autotrophic) carbon fixation. It is suggested that photoautotrophy existed both as a biochemical process and as a geochemical agent since at least 3.8 Ga ago. Combining the stoichiometry of the photosynthesis reaction with a carbon isotope mass balance and current concepts for the evolution of the stationary sedimentary mass as a funion of time, it is possible to quantify, the accumulation of oxygen and its photosynthetic oxidation equivalents through Earth history.

Schidlowski, M.

183

Extrasolar Visions  

NSDL National Science Digital Library

The Extrasolar Visions Web site provides a searchable guide to extra solar planets. These include planets of normal stars, pulsar planets, brown dwarfs, protoplanetary disks and protoplanets, extragalactic worlds, massive compact halo objects, and disproven or doubtful worlds. Visitors can search for these objects or view the week's 20 most popular systems, 20 most interesting systems, or the 20 most recently updated systems. Once chosen, the objects name, mass, average distance, and type is given along with a link for further information. This well designed site does a good job of combining quality information and graphics resulting in a pleasurable surfing experience for anyone exploring it.

1996-01-01

184

A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres  

Microsoft Academic Search

The action of an electric discharge on reduced gas mixtures such as H2O, CH4 and NH3 (or N2) results in the production of several biologically important organic compounds including amino acids. However, it is now\\u000a generally held that the early Earth’s atmosphere was likely not reducing, but was dominated by N2 and CO2. The synthesis of organic compounds by the

H. James Cleaves; John H. Chalmers; Antonio Lazcano; Stanley L. Miller; Jeffrey L. Bada

2008-01-01

185

Probing the extreme planetary atmosphere of WASP-12b  

NASA Astrophysics Data System (ADS)

We report near-infrared measurements of the terminator region transmission spectrum and dayside emission spectrum of the exoplanet WASP-12b obtained using the HST WFC3 instrument. The disk-average dayside brightness temperature averages about 2900 K, peaking to 3200 K around 1.46 ?m. We modeled a range of atmospheric cases for both the emission and transmission spectrum and confirm the recent finding by Crossfield et al. (Crossfield, I., Barman, T., Hansen, B., Tanaka, I., Kodama, T. [2012b]. arXiv: 1210.4836C) that there is no evidence for C/O > 1 in the atmosphere of WASP-12b. Assuming a physically plausible atmosphere, we find evidence that the presence of a number of molecules is consistent with the data, but the justification for inclusion of these opacity sources based on the Bayesian Information Criterion (BIC) is marginal. We also find the near-infrared primary eclipse light curve is consistent with small amounts of prolate distortion. As part of the calibration effort for these data, we conducted a detailed study of instrument systematics using 65 orbits of WFC3-IR grims observations. The instrument systematics are dominated by detector-related affects, which vary significantly depending on the detector readout mode. The 256 × 256 subarray observations of WASP-12 produced spectral measurements within 15% of the photon-noise limit using a simple calibration approach. Residual systematics are estimated to be ?70 ppm.

Swain, Mark; Deroo, Pieter; Tinetti, Giovanna; Hollis, Morgan; Tessenyi, Marcell; Line, Michael; Kawahara, Hajime; Fujii, Yuka; Showman, Adam P.; Yurchenko, Sergey N.

2013-07-01

186

Extrasolar Trojan planets close to habitable zones  

Microsoft Academic Search

We investigate the stability regions of hypothetical terrestrial planets around the Lagrangian equilibrium points L4 and L5 in some specific extrasolar planetary systems. The problem of their stability can be treated in the framework of the restricted three body problem where the host star and a massive Jupiter-like planet are the primary bodies and the terrestrial planet is regarded as

R. Dvorak; E. Pilat-Lohinger; R. Schwarz; F. Freistetter

2004-01-01

187

Stationary Vortical Flows in Two-Dimensional Plasma and in Planetary Atmospheres  

SciTech Connect

We derive the equation governing the asymptotic stationary states generated by decaying turbulence in two-dimensional plasma and planetary atmosphere. These fluids may be described by the Charney-Hasegawa-Mima equation and their relaxation states show a high degree of organization in vortical flows, similar to the Euler fluid. We develop a field-theoretical framework and show that these systems attain at stationarity the extremum of an energy functional corresponding to self-dual fields.

Spineanu, F.; Vlad, M. [Association EURATOM-MEC Romania, NILPRP, MG-36, Magurele, Bucharest (Romania); Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580 (Japan)

2005-06-17

188

Evaporation of extrasolar planets  

NASA Astrophysics Data System (ADS)

This article presents a review on the observations and theoretical modeling of the evaporation of extrasolar planets. The observations and the resulting constraints on the upper atmosphere (thermosphere and exosphere) of the ``hot-Jupiters'' are described. The early observations of the first discovered transiting extrasolar planet, HD209458b, allowed the discovery that this planet has an extended atmosphere of escaping hydrogen. Subsequent observations showed the presence of oxygen and carbon at very high altitude. These observations give unique constraints on the escape rate and mechanism in the atmosphere of hot-Jupiters. The most recent Lyman-alpha HST observations of HD189733b and MgII observations of Wasp-12b allow for the first time a comparison of the evaporation from different planets in different environments. Models to quantify the escape rate from the measured occultation depths, and an energy diagram to describe the evaporation state of hot-Jupiters are presented. Using this diagram, it is shown that few already known planets like GJ876d or CoRot-7b could be remnants of formerly giant planets.

Lecavelier Des Etangs, A.

2010-12-01

189

Exploring extrasolar worlds: from gas giants to terrestrial habitable planets.  

PubMed

Almost 500 extrasolar planets have been found since the discovery of 51 Peg b by Mayor and Queloz in 1995. The traditional field of planetology has thus expanded its frontiers to include planetary environments not represented in our Solar System. We expect that in the next five years space missions (Corot, Kepler and GAIA) or ground-based detection techniques will both increase exponentially the number of new planets discovered and lower the present limit of a approximately 1.9 Earth-mass object [e.g. Mayor et al., Astron. Astrophys., 2009, 507, 487]. While the search for an Earth-twin orbiting a Sun-twin has been one of the major goals pursued by the exoplanet community in the past years, the possibility of sounding the atmospheric composition and structure of an increasing sample of exoplanets with current telescopes has opened new opportunities, unthinkable just a few years ago. As a result, it is possible now not only to determine the orbital characteristics of the new bodies, but moreover to study the exotic environments that lie tens of parsecs away from us. The analysis of the starlight not intercepted by the thin atmospheric limb of its planetary companion (transit spectroscopy), or of the light emitted/reflected by the exoplanet itself, will guide our understanding of the atmospheres and the surfaces of these extrasolar worlds in the next few years. Preliminary results obtained by interpreting current atmospheric observations of transiting gas giants and Neptunes are presented. While the full characterisation of an Earth-twin might requires a technological leap, our understanding of large terrestrial planets (so called super-Earths) orbiting bright, later-type stars is within reach by current space and ground telescopes. PMID:21302557

Tinetti, Giovanna; Griffith, Caitlin A; Swain, Mark R; Deroo, Pieter; Beaulieu, Jean Philippe; Vasisht, Gautam; Kipping, David; Waldmann, Ingo; Tennyson, Jonathan; Barber, Robert J; Bouwman, Jeroen; Allard, Nicole; Brown, Linda R

2010-01-01

190

DETECTING PLANETARY GEOCHEMICAL CYCLES ON EXOPLANETS: ATMOSPHERIC SIGNATURES AND THE CASE OF SO{sub 2}  

SciTech Connect

We study the spectrum of a planetary atmosphere to derive detectable features in low resolution of different global geochemical cycles on exoplanets-using the sulfur cycle as our example. We derive low-resolution detectable features for first generation space- and ground-based telescopes as a first step in comparative planetology. We assume that the surfaces and atmospheres of terrestrial exoplanets (Earth-like and super-Earths) will most often be dominated by a specific geochemical cycle. Here we concentrate on the sulfur cycle driven by outgassing of SO{sub 2} and H{sub 2}S followed by their transformation to other sulfur-bearing species, which is clearly distinguishable from the carbon cycle, which is driven by outgassing of CO{sub 2}. Due to increased volcanism, the sulfur cycle is potentially the dominant global geochemical cycle on dry super-Earths with active tectonics. We calculate planetary emission, reflection, and transmission spectrum from 0.4 mum to 40 mum with high and low resolution to assess detectable features using current and Archean Earth models with varying SO{sub 2} and H{sub 2}S concentrations to explore reducing and oxidizing habitable environments on rocky planets. We find specific spectral signatures that are observable with low resolution in a planetary atmosphere with high SO{sub 2} and H{sub 2}S concentration. Therefore, first generation space- and ground-based telescopes can test our understanding of geochemical cycles on rocky planets and potentially distinguish planetary environments dominated by the carbon and sulfur cycles.

Kaltenegger, L.; Sasselov, D., E-mail: lkaltene@cfa.harvard.ed [Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

2010-01-10

191

A study of nonlinear ionization processes in planetary atmospheres  

SciTech Connect

A model was developed for studying the airglow emission from the resonant transition OI in the Earth's atmosphere. The author used this model to investigate the role of the airglow emission OI {lambda}989 {angstrom} as a secondary source of photoionization of molecular oxygen and nitric oxide, in the ionosphere. The effect of this EUV radiation source on the ion composition at E-region altitudes, during the twilight and at night-time, was studies. He treated the propagation of the OI {lambda}989 {angstrom} resonant photon by using the Monte Carlo simulation technique for the entrapment of resonant radiation in an optically thick thermosphere. Using this simulation model he calculated the enhanced source function due to resonant scattering these photons and the photoionization production rate of O{sub 2}{sup +} and NO{sup +} ions due to this resonance source. A chemistry model for different ionic processes in the ionosphere was developed. Using this chemistry model he calculated the ion distributions in the ionosphere as a function of the solar zenith angle. The results obtained from this investigation show that the secondary photoionization source OI {lambda}989 {angstrom} airglow has a significant effect in the ion density distribution at E-region altitudes and the lower part of the F-region ionosphere. The largest effect of this secondary photoionization source occurs during the sunrise and sunset hours in the absence of direct solar radiation in the lower part of the ionosphere, and in eclipses.

El-Agamaqi, M.M.

1988-01-01

192

Evidence for water in the rocky debris of a disrupted extrasolar minor planet.  

PubMed

The existence of water in extrasolar planetary systems is of great interest because it constrains the potential for habitable planets and life. We have identified a circumstellar disk that resulted from the destruction of a water-rich and rocky extrasolar minor planet. The parent body formed and evolved around a star somewhat more massive than the Sun, and the debris now closely orbits the white dwarf remnant of the star. The stellar atmosphere is polluted with metals accreted from the disk, including oxygen in excess of that expected for oxide minerals, indicating that the parent body was originally composed of 26% water by mass. This finding demonstrates that water-bearing planetesimals exist around A- and F-type stars that end their lives as white dwarfs. PMID:24115434

Farihi, J; Gänsicke, B T; Koester, D

2013-10-11

193

Planetary Ionospheres  

NASA Astrophysics Data System (ADS)

Most planets and many satellites in our solar system are surrounded by envelopes of gravitationally bound gases. The interaction of solar radiation and charged particles of solar wind and planetary magnetospheric origin with these gases produces weak IONIZATION that creates planetary ionospheres embedded within the more dense PLANETARY ATMOSPHERES. Additional sources of ionization which are relat...

Strobel, D.; Murdin, P.

2000-11-01

194

Optical and Hygroscopic Studies of Aerosols In Simulated Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Basic characteristics of the early Earth climate, the only known environment in the Universe in which life has been known to emerge and thrive, remain a mystery. In particular, little is understood about the Earth's atmosphere 2.8 billion years ago. From climate models and laboratory studies, it is postulated that an organic haze, much like that found on Saturn's largest moon Titan, covered the early Earth. This haze, generated from photolysis of carbon dioxide (CO2) and methane (CH4), may have had profound climatic consequences. Climate models of the early Earth that include this haze have had to rely upon optical properties of a Titan laboratory analog. Titan haze, though thought to be similar, is formed from a different combination of precursor gases and by different energy sources than early Earth haze. This thesis examines the direct and indirect radiative effects of aerosol on early Earth climate by studying the optical and hygroscopic properties of a laboratory analog. A Titan analog is studied for comparison and to better understand spacecraft-retrieved haze chemical and optical properties from Titan. The properties of the laboratory analogs, generated in a flowing reactor cell with a continuum ultraviolet (UV) light source, were primarily measured using cavity ringdown aerosol extinction spectroscopy and UV-visible (UV-Vis) transmission spectroscopy. We find that the optical properties of our early Earth analog are significantly different than those of the Titan analog from Khare et al. (1984). In both the UV and visible, when modeled as fractals, particles with the optical properties of the early Earth analog have approximately 30% larger extinction efficiencies than particles with Khare et al. (1984) values. This result implies our early Earth haze analog would provide a more efficient UV shield and have a stronger antigreenhouse effect than the Khare et al. (1984) Titan analog. Our Titan analog has significantly smaller imaginary refractive index values in the UV-Vis than Khare et al. (1984) values. These results may imply that (a) photolysis is not the dominant source of aerosol on Titan, and/or (b) the optical retrievals are dominated by the more absorbing and scattering electric discharge generated aerosol. For the hygroscopicity studies, the optical growth of the early Earth analog at various relative humidities (RH) was measured, as well as a Titan analog for comparison. The retrieved hygroscopic parameter for the early Earth analog indicates that a humidified early Earth aerosol could have contributed to a larger antigreenhouse effect on the early Earth atmosphere than previously modeled with dry aerosol. Such effects would be important in regions where RH is greater than 50% because such high humidities are needed for significant amounts of water to be on the aerosol. The retrieved hygroscopicity parameter also indicates that the particles could activate into cloud droplets at reasonable supersaturations. In regions where the haze was dominant, it is expected that low particle concentrations, once activated into cloud droplets, would create short-lived, optically thin clouds. Such clouds, if predominant on the early Earth, would have a lower albedo than clouds today, thereby warming the planet relative to current day clouds.

Hasenkopf, Christa A.

2011-08-01

195

Predictability of a laboratory analogue for planetary atmospheres  

NASA Astrophysics Data System (ADS)

The first quantitative forecasts of the rotating annulus experiment are presented. Predictability of the second kind (predicting the climatological state of the system, given certain boundary conditions) has been studied in some detail for the rotating annulus, but we believe this is the first study to measure predictability of the first kind (deterministic predictability from initial conditions). The predictability of this experiment is studied by using similar techniques to those used in weather forecasting. A forecasting system has been developed which starts forecasts from analyses of rotating annulus data produced by the Met Office analysis correction method, and uses the breeding method to generate ensembles of initial conditions around these analyses. The results show that flow regimes over a range of complexity can be predicted in this experiment, with varying success. Forecasts in the steady wave flow regime verify well against observations, and are predictable until the end of the available data. Forecasts in the amplitude and structural vacillation flow regimes lose quality and skill by a combination of wave drift and wavenumber transition. Amplitude vacillation is predictable up to several hundred seconds ahead, and structural vacillation is predictable for a few hundred seconds. The annulus is firmly established as an insightful laboratory analogue for certain kinds of atmospheric dynamical behaviour, and is also a useful testbed for the methods used to study them. The laboratory setting allows baroclinic flow to be studied in a reproducible manner in a system where the complexity of the flow can be controlled. Few attempts have taken advantage of these properties of laboratory systems to inform the development of operational forecasting techniques, and this work is also intended to demonstrate a proof-of-concept: that the annulus could be used as a testbed for meteorological techniques under laboratory conditions.

Young, Roland; Read, Peter

2010-05-01

196

Mass spectrometric analysis in planetary science: Investigation of the surface and the atmosphere  

NASA Astrophysics Data System (ADS)

Knowing the chemical, elemental, and isotopic composition of planetary objects allows the study of their origin and evolution within the context of our Solar System. Landed probes are critical to such an investigation. Instruments on a landed platform can answer a different set of scientific questions than can instruments in orbit or on Earth. Composition studies for elemental, isotopic, and chemical analysis are best performed with dedicated mass spectrometer systems. Mass spectrometers have been part of the early lunar missions, and have been successfully employed to investigate the atmospheres of Mars, Venus, Jupiter, Saturn, Titan, and in comet missions. Improved mass spectrometer systems are foreseen for many planetary missions currently in planning or implementation.

Wurz, P.; Abplanalp, D.; Tulej, M.; Iakovleva, M.; Fernandes, V. A.; Chumikov, A.; Managadze, G. G.

2012-11-01

197

On the protection of extrasolar Earth-like planets around K/M stars against galactic cosmic rays  

NASA Astrophysics Data System (ADS)

Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is strongly reduced by tidal locking. Therefore, such a close-in extrasolar planet is not protected by an extended magnetosphere. (b) The small orbital distance of the planet exposes it to a much denser stellar wind than that prevailing at larger orbital distances. This dense stellar wind leads to additional compression of the magnetosphere, which can further reduce the shielding efficiency against GCRs. In this work, we analyse and compare the effect of (a) and (b), showing that the stellar wind variation with orbital distance has little influence on the cosmic ray shielding. Instead, the weak shielding of M star planets can be attributed to their small magnetic moment. We further analyse how the planetary mass and composition influence the planetary magnetic moment, and thus modify the cosmic ray shielding efficiency. We show that more massive planets are not necessarily better protected against galactic cosmic rays, but that the planetary bulk composition can play an important role.

Grießmeier, J.-M.; Stadelmann, A.; Grenfell, J. L.; Lammer, H.; Motschmann, U.

2009-02-01

198

Influx of cometary volatiles to planetary moons: the atmospheres of 1000 possible Titans.  

PubMed

We use a Monte Carlo model to simulate impact histories of possible Titans, Callistos, and Ganymedes. Comets create or erode satellite atmospheres, depending on their mass and velocity distributions: faster and bigger comets remove atmophiles; slower or smaller comets supply them. Mass distributions and the minimum total mass of comets passing through the Saturn system were derived from the crater records of Rhea and Iapetus. These were then scaled to give a minimum impact history for Titan. From this cometary population, of 1000 initially airless Titans, 16% acquired atmospheres larger than Titan's present atmosphere (9 x 10(21) g), and more than half accumulated atmospheres larger than 10(21) g. In contrasts to the work of Zahnle et al. (1992), we find that, in most trials, Callisto acquires comet-based atmospheres. Atmospheres acquired by Callisto and, especially, Ganymede are sensitive to assumptions regarding energy partitioning into the ejecta plume. If we assume that only the normal velocity component heats the plume, the majority of Ganymedes and half of the Callistos accreted atmospheres smaller than 10(20) g. If all the impactor's velocity heats the plume, Callisto's most likely atmosphere is 10(17) g and Ganymede's is negligible. The true cometary flux was most likely larger than that derived from crater records, which raises the probability that Titan, Ganymede, and Callisto acquired substantial atmospheres. However, other loss processes (e.g., sputtering by ions swept up by the planetary magnetic field, solar UV photolysis of hydrocarbons) are potentially capable of eliminating small atmospheres over the age of the solar system. The dark material on Callisto's surface may be a remnant of an earlier, now vanished atmosphere. PMID:11539417

Griffith, C A; Zahnle, K

1995-08-25

199

THE EFFECTS OF SNOWLINES ON C/O IN PLANETARY ATMOSPHERES  

SciTech Connect

The C/O ratio is predicted to regulate the atmospheric chemistry in hot Jupiters. Recent observations suggest that some exoplanets, e.g., Wasp 12-b, have atmospheric C/O ratios substantially different from the solar value of 0.54. In this Letter, we present a mechanism that can produce such atmospheric deviations from the stellar C/O ratio. In protoplanetary disks, different snowlines of oxygen- and carbon-rich ices, especially water and carbon monoxide, will result in systematic variations in the C/O ratio both in the gas and in the condensed phases. In particular, between the H{sub 2}O and CO snowlines most oxygen is present in icy grains-the building blocks of planetary cores in the core accretion model-while most carbon remains in the gas phase. This region is coincidental with the giant-planet-forming zone for a range of observed protoplanetary disks. Based on standard core accretion models of planet formation, gas giants that sweep up most of their atmospheres from disk gas outside of the water snowline will have a C/O {approx} 1, while atmospheres significantly contaminated by evaporating planetesimals will have a stellar or substellar C/O when formed at the same disk radius. The overall metallicity will also depend on the atmosphere formation mechanism, and exoplanetary atmospheric compositions may therefore provide constraints on where and how a specific planet formed.

Oeberg, Karin I.; Murray-Clay, Ruth [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bergin, Edwin A., E-mail: koberg@cfa.harvard.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

2011-12-10

200

Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates. II. Transits of OGLE-TR-113-b in the Optical and Near-IR  

NASA Astrophysics Data System (ADS)

We present precise V- and Ks-band transit photometry for the planetary host star OGLE-TR-113. Using the Ks-band photometry, we confirm the dwarf nature of OGLE-TR-113 and obtain new estimates for its effective temperature, distance, and reddening. We employ the V-band photometry to obtain planetary and orbit parameters from the transit fit, a=0.0232+/-0.0038 AU, orbital period P=1.4324752+/-0.0000015 day, i=86.7-90, and Rp=1.09+/-0.09 RJ. These values are in excellent agreement with previous works. Assuming a mass Mp=1.32+/-0.19 MJ for the planet, we obtain its mean density ?=1.26+/-0.50 g cm-3, also in agreement with previous works. The transit observed in the Ks band has a larger scatter, and we find its amplitude to be consistent with that in the V band. In this way, we find an independent confirmation of the planetary nature of OGLE-TR-113b. Based on observations collected with the Very Large Telescope at Paranal Observatory (J. M. F. and D. M. visiting observers) and at the ESO New Technology Telescope at La Silla Observatory (S. R., F. P., and D. M. visiting observers) for the ESO Programs 075.C-0427, 075.B-0414, and 076.C-0122.

Díaz, Rodrigo F.; Ramírez, Sebastián; Fernández, José Miguel; Gallardo, José; Gieren, Wolfgang; Ivanov, Valentin D.; Mauas, Pablo; Minniti, Dante; Pietrzynski, Grzegorz; Pérez, Felipe; Ruíz, María Teresa; Udalski, Andrzej; Zoccali, Manuela

2007-05-01

201

A numerical radiative transfer model for a spherical planetary atmosphere: combined differential–integral approach involving the Picard iterative approximation  

Microsoft Academic Search

A new radiative transfer model suitable to calculate the radiation field in a spherical planetary atmosphere has been developed. The suggested approach involves the Picard iterative approximation to solve the radiative transfer equation in its integral form. The radiation field calculated by solving the integro-differential radiative transfer equation in a pseudo-spherical atmosphere is used as an initial guess for the

A. Rozanov; V. Rozanov; J. P. Burrows

2001-01-01

202

Kinetics of suprathermal hydrogen atom reactions with saturated hydrides in planetary and satellite atmospheres  

NASA Astrophysics Data System (ADS)

The kinetics of saturated hydrides methane (CH4), silane (SiH4), germane (GeH4), ammonia (NH3), phosphine (PH3), arsane (AsH3), water (H2O), and hydrogen sulfide (H2S) in the low-temperature atmospheres of Jupiter, Saturn, Uranus, Neptune, Pluto, Titan, and Triton reacting with suprathermal hydrogen atoms were investigated computationally to extract suprathermal rate constants /k(E) via an inverse Laplace transformation from experimentally available thermal rate constants /k(T). Our data reveal that all suprathermal rate constants range up to 10-10cm3s-1, whereas the thermal counterparts are as low as 8×10-73cm3s-1. These data demonstrate explicitly a significantly enhanced reactivity of photolytically generated suprathermal hydrogen atoms in the low-temperature planetary and satellite atmospheres and suggest that this hitherto unaccounted reaction class should be included by the planetary modeling community into future photochemical networks of atmospheres of outer solar system planets and their moons.

Morton, Richard J.; Kaiser, Ralf I.

2003-05-01

203

Secondary planetary waves in the middle and upper atmosphere following the stratospheric sudden warming event of January 2012  

NASA Astrophysics Data System (ADS)

The role of planetary waves in causing stratospheric sudden warmings (SSWs) is well understood and quantified. However, recent studies have indicated that secondary planetary waves are excited in the mesosphere and lower thermosphere following SSWs. We use a version of the Whole Atmosphere Community Climate Model constrained by reanalysis data below 50 km to simulate the SSW of January 2012, a minor warming followed by the formation of an elevated stratopause. We document the occurrence of enhanced Eliassen-Palm flux divergence in the mesosphere and lower thermosphere associated with faster, secondary westward-propagating planetary waves of wave number 1 and period <10 days. We confirm the presence of these secondary planetary waves using observations made by the Sounding of the Atmosphere using the Broadband Emission Radiometry instrument onboard NASA's Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite.

Chandran, A.; Garcia, R. R.; Collins, R. L.; Chang, L. C.

2013-05-01

204

Direct Evidence of Multifractal Atmospheric Cascades from Planetary Scales down to 1 km  

NASA Astrophysics Data System (ADS)

We use 909 satellite images spanning the scale range 1-5000 km at both visible and infrared wavelengths to show that the variability at all observed scales and at all levels of intensity is very close to that predicted for a direct multiplicative scale invariant cascade starting at planetary scales. To within 1.6%/octave in scale, the observed type of (multi)scaling is very close to that theoretically predicted for universal multifractals, including multifractal phase transitions. Because of the strong vertical stratification, the scaling cannot be isotropic; these findings thus give strong support to the anisotropic ``unified scaling'' model of atmospheric dynamics.

Lovejoy, S.; Schertzer, D.; Stanway, J. D.

2001-05-01

205

Direct evidence of atmospheric cascades from planetary scales down to 1 km  

NASA Astrophysics Data System (ADS)

We use 909 satellite images spanning the scale range 1-5000km at both visible and infra red wavelengths to show that the variability at all observed scales and at all levels of intensity is very close to that predicted for a direct multiplicative scale invariant cascade starting at planetary scales. To within 1.6%/octave in scale, the observed type of (multi)scaling is very close to that theoretically predicted for universal multifractals, including multifractal phase transitions. Because of the strong vertical stratification, the scaling cannot be isotropic; these findings thus give strong support to the anisotropic "unified scaling" model of atmospheric dynamics.

Lovejoy, S.; Schertzer, D.; Stanway, J.

2001-05-01

206

Turbulence in planetary occultations. II - Effects on atmospheric profiles derived from Doppler measurements. III - Effects on atmospheric profiles derived from intensity measurements  

Microsoft Academic Search

The nature and magnitude of turbulence-induced errors in atmospheric profiles derived from Doppler measurements made during radio occultations are investigated. It is found that turbulence in planetary atmospheres induces both fluctuating and systematic errors in derived profiles, but the errors of both types are very small. Consideration of the occultation of Mariner 10 by Venus and of the Pioneer occultations

B. S. Haugstad

1978-01-01

207

Laboratory studies on N(2D) reactions of relevance to the chemistry of planetary atmospheres  

NASA Astrophysics Data System (ADS)

Molecular nitrogen is a very stable molecule, practically inert from a chemical point of view. For a nitrogen chemistry to occur in the planetary atmospheres which contain N2 , it is necessary to transform it into an active form, such as atoms or ions. As far as the production of atomic nitrogen in the upper atmospheres of planets (like Mars) or moons (like Titan) is concerned, several processes - as N2 dissociation induced by electron impact, EUV photolysis (? <80 nm) and dissociative photoionization, or galactic cosmic ray absorption and N+ dissociative recombination all 2 lead to atomic nitrogen, notably in the ground, 4 S3/2 , and first electronically excited, 2 D3/2,5/2 , states with comparable yields. The radiative lifetimes of the metastable states 2 D3/2 and 2 D5/2 are quite long (12.3 and 48 hours, respectively), because the transition from a doublet to a quartet state is strongly forbidden. In addition, the physical quenching of N(2 D) is often a slow process and in some important cases the main fate of N(2 D) is chemical reaction with other constituents of the planetary atmospheres. The production of N atoms in the 2 D state is an important fact, because N(4 S) atoms exhibit very low reactivity with closed-shell molecules and the probability of collision with an open-shell radical is small. Unfortunately laboratory experiments on the gas-phase reactions of N(2 D) have been lacking until recently, because of serious experimental difficulties in studying these reactive systems. Accurate kinetic data on the reactions of N(2 D) with the some molecules of relevance to the chemistry of planetary atmospheres have finally become available in the late 90's, but a better knowledge of the reactive behavior requires a dynamical investigation of N(2 D) reactions. The capability of generating intense continuous beams of N(2 D) achieved in our laboratory some years ago has opened up the possibility of studying the reactive scattering of this species under single collision conditions by means of the "crossed molecular beam" technique with mass spectrometric detection. Some examples of our experimental results will be illustrated, with particular attention to the reactions of N(2 D) with hydrocarbons (CH4 , C2 H2 and C2 H4 ) of relevance to the atmosphere of Titan, but also with other molecules of relevance to the atmospheres of Mars, Triton and Pluto.

Balucani, N.; Casavecchia, P.

208

Polarimetry of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Polarimetry is a powerful technique for detecting directly the starlight that is scattered in a planetary atmosphere and, thus, possesses information on its geometry, chemistry, and thermodynamics. Recently, we have started a polarimetric survey of nearby planetary systems with hot Jupiters closely orbiting their host stars using the DiPol polarimeter at the KVA telescope and the TurPol polarimeter at the Nordic Optical Telescope, La Palma. Here we present our first results and discuss orbital parameters of the HD 189733 system and scattering properties of its planet.

Berdyugin, A.; Berdyugina, S.; Fluri, D.; Piirola, V.

2011-11-01

209

Photochemistry simulation of planetary atmosphere using synchrotron radiation at soleil. Application to Titan's atmosphere  

NASA Astrophysics Data System (ADS)

We report here on the coupling of a gas reactor with a VUV beamline at the SOLEIL synchrotron radiation facility. The reactor may be irradiated window-less with gas pressure up to the atmosphere. The photochemistry is monitored by a mass spectrometer gas analyzer. This set up, termed APSIS for Atmospheric Photochemistry SImulated by Synchrotron, has been used to simulate the atmosphere of Titan and to study the formation of the photochemical smog and the formation of tholins.

Gautier, T.; Peng, Z.; Giuliani, A.; Carrasco, N.; Cernogora, G.; Mahjoub, A.; Correia, J.-J.; Szopa, C.; Pernot, P.; Buch, A.; Benilan, Y.

2012-02-01

210

Tidal evolution of extra-solar planets  

NASA Astrophysics Data System (ADS)

In both our solar system and extra-solar planetary systems, tides may have a variety of effects, driving complex orbital evolution and geophysical processes. For extra-solar planets with orbits that pass very close to their host stars, tides have reduced orbital eccentricities and semi-major axes, and the rates of tidal evolution may change dramatically as orbits evolve. Understanding how the orbits have evolved and, ultimately, discerning the origins of close-in extra-solar planets require accounting for all the complexity of tidal evolution. The accompanying dissipation of tidal energy within the planets has probably also affected their internal structures. In some cases, tidal dissipation may account the apparent discrepancy between predictions and observations of the radii of extra-solar planets that transit their host stars. Evolutionary models for these planets that allow determinations of their internal structures and composition must include highly variable tidal heating rates. The same tidal evolution and heating probably also affects the orbital and geophysical properties of rocky extra-solar planets and may play a key role in determining whether such a planet can harbor life. As tides reduce a planet's semi-major axis, the planet may eventually pass so close to its host star that the star's gravity completely disrupts the planet, leading to the destruction of many planets. Tidal destruction has left a discernible signature on the distribution of extra-solar planetary orbits, and so interpretations of the distribution in terms of the origins of planets must include consideration of the effects of tidal destruction.

Jackson, Brian Kendall

211

Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates. IV. Solution to the Puzzle of the Extremely Red OGLE-TR-82 Primary  

NASA Astrophysics Data System (ADS)

We present precise new V-, I-, and Ks-band photometry for the planetary-transit candidate star OGLE-TR-82. V-band images acquired in good seeing with the VIMOS instrument at the Very Large Telescope allowed us to measure V=20.61+/-0.03 mag for this star despite the presence of a brighter neighbor about 1" away. This faint magnitude answers the question why it has not been possible to measure radial velocities for this object. One transit of this star has been observed with the GMOS-S instrument on Gemini South in the i and g bands, which allowed us to verify that this is not a false positive, to confirm the transit amplitude measured by OGLE, and to improve the ephemeris. The transit is better defined in the i-band light curve (with a depth of Ai=0.034 mag), than in the g band (Ag=0.1 mag), in which the star is significantly fainter. Near-IR photometry obtained with the SOFI array at the ESO New Technology Telescope yields K=12.20+/-0.10 and V-K=8.40+/-0.10, so red that it is unlike any transit candidate studied before. With the new data, we consider two possible configurations for the system: (1) a nearby M7 V star or (2) a blend with a very reddened, distant red giant. The first hypothesis would give a radius for the companion of Rp=0.3+/-0.1 RJ, i.e., the size of Neptune. Quantitative analysis of near-IR spectroscopy finally shows that OGLE-TR-82 is a distant, reddened, metal-poor early K giant, confirmed by direct comparison with stellar templates, which gives as a best match a K3 III star. Therefore, we rule out a planetary nature for the companion, and conclude that this system is a main-sequence binary blended with a background red giant. As a case study, a system that can so mimic a planetary transit presents a lesson for future transit surveys. Based on observations collected with the Gemini South telescope (queue observing, program GS-2005B-Q-9) and with the Very Large Telescope at Paranal Observatory (J. M. F. and D. M., Visiting Astronomers) and the ESO New Technology Telescope at La Silla Observatory (S. R., F. P., and D. M., Visiting Astronomers) for ESO programs 075.C-0427, 075.B-0414, and 076.C-0122.

Hoyer, Sergio; Ramírez Alegría, Sebastián; Ivanov, Valentin D.; Minniti, Dante; Pietrzy?ski, Grzegorz; Ruíz, María Teresa; Gieren, Wolfgang; Udalski, Andrzej; Zoccali, Manuela; Carrasco, Eleazar Rodrigo; Díaz, Rodrigo F.; Fernández, José Miguel; Gallardo, José; Rejkuba, Marina; Pérez, Felipe

2007-11-01

212

Characterization of potentially habitable planets: Retrieval of atmospheric and planetary properties from emission spectra  

NASA Astrophysics Data System (ADS)

Context. An increasing number of potentially habitable terrestrial planets and planet candidates are found by ongoing planet search programs. The search for atmospheric signatures to establish planetary habitability and the presence of life might be possible in the future. Aims: We want to quantify the accuracy of retrieved atmospheric parameters (composition, temperature, pressure) that might be obtained from infrared emission spectroscopy. Methods: We use synthetic observations of the atmospheres of hypothetical potentially habitable planets. These were constructed with a parametrized atmosphere model, a high-resolution radiative transfer model and a simplified noise model. The simulated observations were used to fit the model parameters. Furthermore, classic statistical tools such as ?2 statistics and least-square fits were used to analyze the simulated observations. Results: When adopting the design of currently planned or proposed exoplanet characterization missions, we find that emission spectroscopy could provide weak limits on the surface conditions of terrestrial planets, hence their potential habitability. However, these mission designs are unlikely to allow the composition of the atmosphere of a habitable planet to be characterized, even though CO2 is detected. Upon increasing the signal-to-noise ratios by about a factor of 2-5 (depending on spectral resolution) compared to current mission designs, the CO2 content could be characterized to within two orders of magnitude. The detection of the O3 biosignature remains marginal. The atmospheric temperature structure could not be constrained. Therefore, a full atmospheric characterization seems to be beyond the capabilities of such missions when using only emission spectroscopy during secondary eclipse or target visits. Other methods such as transmission spectroscopy or orbital photometry are probably needed in order to give additional constraints and break degeneracies.

von Paris, P.; Hedelt, P.; Selsis, F.; Schreier, F.; Trautmann, T.

2013-03-01

213

Spacecraft and Stellar Occultations by Turbulent Planetary Atmospheres. A Theoretical Investigation of Various Wave Propagation Effects and Their Impact on Derived Profiles of Refractivity, Temperature and Pressure.  

National Technical Information Service (NTIS)

The long propagation paths involved in radio and stellar occultations by turbulent planetary atmospheres require that the classical, weak scattering scintillation theory be expanded to account for the inhomogeneous ambient atmosphere upon which the turbul...

B. S. Haugstad

1981-01-01

214

Spacecraft and Stellar Occulations by Turbulent Planetary Atmospheres: A Theoretical Investigation of Various Wave Propagation Effects and Their Impact on Derived Profiles of Refractivity, Temperature, and Pressure.  

National Technical Information Service (NTIS)

The long propagation paths involved in radio and stellar occultations by turbulent planetary atmospheres require that the classical, weak scattering scintillation theory be expanded to account for the inhomogeneous ambient atmosphere upon which the turbul...

B. S. Haugstad

1981-01-01

215

When Extrasolar Planets Transit Their Parent Stars  

Microsoft Academic Search

When extrasolar planets are observed to transit their parent stars, we are\\u000agranted unprecedented access to their physical properties. It is only for\\u000atransiting planets that we are permitted direct estimates of the planetary\\u000amasses and radii, which provide the fundamental constraints on models of their\\u000aphysical structure. In particular, precise determination of the radius may\\u000aindicate the presence (or

David Charbonneau; Timothy M. Brown; Adam Burrows; Greg Laughlin

2006-01-01

216

Extrasolar planets and Their Parent Stars  

NASA Astrophysics Data System (ADS)

Extrasolar planetas (exoplanets), or planets orbiting stars other than our own Sun, are a relatively new field of the astronomical and planetary sciences. After the discovery of Pluto in 1930, planet-finding activities appeared to have reached an end for the foreseeable future. Several brown dwarfs have been discovered between 1930 and 1993 orbiting other solar-type star. Brown dwarfs (or "failed stars") are low-mass celestial objects (M?10MJUP) that formed by stellar processes but did not obtain the critical mass required to sustain hydrogen burning within their core. Other claims for planetary detections were also made during the period 1944 - 1970 but were never verified or were later shown to be false, produced by timing artifacts or instrumentation errors. The first confirmed detection of an extrasolar planet occurred in 1992 when two bodies were found to be orbiting the millisecond pulsar PSR 1257+12 (Wolszczan and Frail, 1992). The first detection of an extrasolar planet orbiting a solar-type star occurred in 1994 with the claim of a Jupiter-type planet orbiting 51 Pegasi (Mayor and Queloz, 1995). As of January 2010, we currently know of 429 planets orbiting solar-type stars The vast majority of these detections have occurred via the radial velocity method (Udry & Santos 2007), although other methods such as that of transiting photometry and microlensing may become increasingly important in future planet searches as we seek to detect terrestrial-sized planetary bodies and utilize space- based observing programs.

Israelian, Garik

2010-11-01

217

Gamma-ray and neutron spectroscopy of planetary surfaces and atmospheres  

SciTech Connect

The neutrons and gamma rays escaping from a planet can be used to map the concentrations of various elements in its surface. In a planet, the high-energy particles in the galactic cosmic rays induce a cascade of particles that includes many neutrons. The ..gamma.. rays are made by the decay of the naturally-occurring radioelements and by nuclear excitations induced by cosmic-ray particles and their secondaries (especially neutron capture or inelastic scattering reactions). After a short history of planetary ..gamma..-ray and neutron spectroscopy, the ..gamma..-ray spectrometer and active neutron detection system planned for the Mars Observer Mission are presented. The results of laboratory experiments that simulate the cosmic-ray bombardments of planetary surfaces and the status of the theoretical calculations for the processes that make and transport neutrons and ..gamma.. rays will be reviewed. Studies of Mars, including its atmosphere, are emphasized, as are new ideas, concepts, and problems that have arisen over the last decade, such as Doppler broadening and peaks from neutron scattering with germanium nuclei in a ..gamma..-ray spectrometer. 23 refs., 1 fig.

Reedy, R.C.

1987-01-01

218

Adaptive Optics Survey for Companions to Stars with Extra-Solar Planets.  

National Technical Information Service (NTIS)

We have undertaken an adaptive optics imaging survey of extrasolar planetary systems and stars showing interesting radial velocity trends from high precision radial velocity searches. Adaptive Optics increases the resolution and dynamic range of an image,...

J. P. Lloyd M. C. Liu J. R. Graham M. Enoch P. Kalas G. W. Marcy D. Fischer

2000-01-01

219

The HARPS search for southern extra-solar planets. XXX. Planetary systems around stars with solar-like magnetic cycles and short-term activity variation  

NASA Astrophysics Data System (ADS)

We present the discovery of four new long-period planets within the HARPS high-precision sample: HD 137388b (Msini = 0.22 MJ), HD 204941b (Msini = 0.27 MJ), HD 7199b (Msini = 0.29 MJ), HD 7449b (Msini = 1.04 MJ). A long-period companion, probably a second planet, is also found orbiting HD 7449. Planets around HD 137388, HD 204941, and HD 7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD 7449b. All these planets were discovered even though their hosting stars have clear signs of activity. Solar-like magnetic cycles, characterized by long-term activity variations, can be seen for HD 137388, HD 204941 and HD 7199, whereas the measurements of HD 7449 reveal a short-term activity variation, most probably induced by magnetic features on the stellar surface. We confirm that magnetic cycles induce a long-term radial velocity variation and propose a method to reduce considerably the associated noise. The procedure consists of fitting the activity index and applying the same solution to the radial velocities because a linear correlation between the activity index and the radial velocity is found. Tested on HD 137388, HD 204941, and HD 7199, this correction reduces considerably the stellar noise induced by magnetic cycles and allows us to derive precisely the orbital parameters of planetary companions. Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at La Silla Observatory (Chile), under programme IDs 072.C-0488 and 183.C-0972.Radial velocities (Tables 4-7) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A55

Dumusque, X.; Lovis, C.; Ségransan, D.; Mayor, M.; Udry, S.; Benz, W.; Bouchy, F.; Lo Curto, G.; Mordasini, C.; Pepe, F.; Queloz, D.; Santos, N. C.; Naef, D.

2011-11-01

220

In-situ exploration of planetary upper atmospheres with balloons ejected from sounding rockets and space probes  

Microsoft Academic Search

Balloon missions have been used extensively on Earth to study a large variety of atmospheric characteristics and phenomena. Of primary interest are in situ temperature, pressure and density profiles and wind velocities. The first planetary balloons were flown in the mid 1980s with the Vega 1 and 2 missions to Venus. Since then, balloons have been further developed and planed

Michael Danielides; Hannes Griebel; Klaus Bayler; J. Herholz

2010-01-01

221

Noble gas isotopic composition as a key reference parameter in a planetary atmospheric evolution model  

NASA Astrophysics Data System (ADS)

The isotopic composition of noble gases is a key reference parameter in discussing the evolution of planetary atmospheres. Currently, two widely occurring noble gas components are identified in the early solar system, one is the Solar Wind noble gas (SW-noble gas, hereafter) and another is the Q-noble gas in unaltered meteorites: both noble gases are characterized by their ubiquitous occurrence and high isotopic homogeneity. Since the SW-noble gas is directly ejected from the Sun, it has been assumed to be a good proxy of the average noble gas isotopic composition in the Sun, namely the solar noble gas. The systematic enrichment of the heavier isotopes in the Q-noble gas relative to the SW-noble gas is then commonly attributed to its isotopic fractionation from the SW-noble gas. However, the isotopic compositions of the SW-noble gas either implanted on lunar soils or trapped by artificial targets show considerable isotopic variation depending on the velocity of the Solar Wind. Therefore, it is important to examine how closely the SW-noble gas represents the indigenous solar noble gas component or the mean isotopic composition of noble gases of the Sun. Here we show that the isotopic composition of the SW-noble gas is substantially fractionated relative to the solar value, and therefore should not be used as a reference parameter. We further suggest that the post D-burning Q-noble gas (see below) is the better proxy of the solar noble gas, and this should be used as a reference of the Solar noble gas isotopic composition in discussing the planetary atmospheric evolution. The most distinct difference between the Q- and the SW-noble gas is apparent in a 3He/4He isotopic ratio: 4.64e-4 in Q-He [1], but 1.23e-4 in SW-He[2]. The difference is attributed to the conversion of deuteron (D) to 3He in the Sun, namely the D-burning [3], due to high temperature during the pre-main sequence stage of the Sun. With the use of recent data on D/H ratios from helio-seismology [4] and spectroscopic observation of the inter-stellar cloud [5], we estimated that the 3He/4He ratio in the post D-burning He in the Sun is 3.98e-4. The latter value is considerably smaller than the recent estimate of the SW-He ratio by the GENESIS mission of 3He/4He = 4.64e-4 [2]. We conclude that this difference is due to isotopic fractionation during the ejection of the Solar Wind from the solar atmosphere. The further interesting implication of this conclusion is that the marked difference in 3He/4He between the SW- and Q-noble gases can be used as an unique chronological marker in the planetary atmospheric evolution. [1] Busemann H. et al., Meteoritics & Planetary Science, 35, 949-973, 2000. [2] Heber V. et al. Geochimica Cosmochimica Acta, 73, 7414-7432, 2009. [3] Geiss J. and Reeve H. Astronomy Astrophysics, 18, 126-132, 1972. [4] Basu S. and Antia H.M. Astrophysical J. , 606:L85-L88, 2004. [5] Linsky J.L. et al. Astrophysical J., 647:1106-1124, 2006.

Ozima, M.

2010-12-01

222

Formation of bioorganic compounds in simulated planetary atmospheres by high energy particles or photons.  

PubMed

Various types of organic compounds have been detected in Jupiter, Titan, and cometary coma. It is probable that organic compounds were formed in primitive Earth and Mars atmospheres. Cosmic rays and solar UV are believed to be two major energy sources for organic formation in space. We examined energetics of organic formation in simulated planetary atmospheres. Gas mixtures including a C-source (carbon monoxide or methane) and a N-source (nitrogen or ammonia) was irradiated with the followings: High energy protons or electrons from accelerators, gamma-rays from 60Co, UV light from a deuterium lamp, and soft X-rays or UV light from an electron synchrotron. Amino acids were detected in the products of particles, gamma-rays and soft X-rays irradiation from each gas mixture examined. UV light gave, however, no amino acid precursors in the gas mixture of carbon monoxide, nitrogen and nitrogen. It gave only a trace of them in the gas mixture of carbon monoxide, ammonia and water or that of methane, nitrogen and water. Yield of amino acid precursors by photons greatly depended on their wavelength. These results suggest that nitrogen-containing organic compounds like amino acid precursors were formed chiefly with high energy particles, not UV photons, in Titan or primitive Earth/Mars atmospheres where ammonia is not available as a predominant N-source. PMID:11605633

Kobayashi, K; Masuda, H; Ushio, K I; Ohashi, A; Yamanashi, H; Kaneko, T; Takahashi, J I; Hosokawa, T; Hashimoto, H; Saito, T

2001-01-01

223

MICROWAVE REMOTE SENSING OF PLANETARY ATMOSPHERES: THE 50 YEARS FROM MARINER 2 TO NASA-JUNO  

NASA Astrophysics Data System (ADS)

In November 2012, the world celebrated the 50th anniversary of spacecraft-based exploration of planets and satellites other our own. The first successful interplanetary mission (Mariner 2) included the first spaceborne microwave radiometer for studying planetary atmospheres which measured the 1.3 and 2.0 cm emission spectrum of Venus (also known as the Cytherean spectrum), These measurements, plus accompanying earth-based observations of the centimeter-wavelength spectrum were used to establish early models of the composition and structure of Venus. Shortly thereafter, measurements of the microwave emission spectrum of Jupiter (also known as the Jovian spectrum) from 1.18 to 1.58 cm were conducted. In both sets of observations, wavelengths near the 1.35 cm water-vapor resonance were selected in hope of detecting the spectral signature of water vapor, but none was found. Thus the question remained, “where’s the water?” The NASA-Juno mission is the first mission since Mariner 2 to carry a microwave radiometer instrument designed specifically for atmospheric sensing. It is expected to finally detect water in the Jovian atmosphere.

Steffes, Paul G.

2013-10-01

224

Estimation of Convective Planetary Boundary Layer Evolution and Land-Atmosphere Interactions from MODIS and AIRS  

NASA Astrophysics Data System (ADS)

Land-atmosphere interaction and coupling remain weak links in current observational and modeling approaches to understanding and predicting the Earth-Atmosphere system. The degree to which the land impacts the atmosphere (and vice-versa) is difficult to quantify given the disparate resolutions and complexity of land surface and atmospheric models. Remote sensing offers the ability to monitor PBL and land surface properties semi-continuously over time and space, and has the potential to provide valuable information on energy and water balances across a range of scales. While well-established satellites such as HIRS and GOES have been providing atmospheric profile data for decades, they are distinctly lacking in temporal and vertical resolution necessary to capture the diurnal evolution of the convective planetary boundary layer. In this study, atmospheric profiles retrieved from high-spectral resolution measurements made by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra and Aqua spacecraft and the Atmospheric Infrared Sounder (AIRS) aboard Aqua. The coverage of these sensors greatly improves upon the coarse network of synoptic radiosonde and intermittent satellite coverage available, and MODIS and AIRS are the first sensors that potentially allow for PBL structure and evolution to be in the context of its relationship and interactions with the land surface. An evaluation of MODIS and AIRS retrievals is performed for 44 days at the ARM-SGP site using radiosonde data, focusing on how well PBL properties can be discerned from each sensor under a range of conditions. PBL structure and evolution from these profiles is assessed at the multiple overpass times of the MODIS and AIRS sensors, and previously developed methods to estimate PBL structure and infer surface conditions are applied using the remote sensing data. To circumvent biases found in the retrieval process, cloud-cleared radiances measured by AIRS in 2085 infrared channels are then examined in the context of PBL and surface property retrievals using statistical techniques. By exploiting strong absorption and window regions of the infrared spectrum, the response of relatively few AIRS channels can be used to describe land surface and PBL conditions on daily to seasonal timescales. Overall, this study highlights the current ability of remote sensing to estimate land-atmosphere interactions, as well as provides guidance for future sensor specification in order to improve our understanding of these processes at a global scale.

Santanello, J. A.; Friedl, M. A.

2006-12-01

225

Reduced asymptotic models for planetary and synoptic motions in the atmosphere  

NASA Astrophysics Data System (ADS)

Reduced model equations valid for two different planetary scale regimes are presented. The models are derived using an unified multiple scales asymptotic approach and account in a systematic way for the planetary-synoptic interactions. The first regime includes the planetary geostrophic equations and a new two scale closure condition in the form of an evolution equation for the vertically averaged pressure. The influence of the synoptic scale on the planetary scale dynamics is represented by the planetary scale divergence of the synoptic momentum fluxes in the closure equation. In the second asymptotic regime only planetary variations in the zonal direction are allowed. This regime describes a coupling between the planetary evolution of the leading order synoptic PV field and the synoptic dynamics of higher order PV corrections. The analysis of experiments with a primitive equations model shows that the asymptotic models capture the leading order balances in the planetary scale vorticity transport.

Dolaptchiev, Stamen; Klein, Rupert

2010-05-01

226

Planetary Waves, Dynamics, and Minor Species Distribution in the Martian Atmosphere observed with PFS/MEX data  

NASA Astrophysics Data System (ADS)

We retrieve atmospheric water vapour and carbon monoxide abundances from nadir data acquired by the Planetary Fourier Spectrometer (PFS) on board of the Mars Express orbiter. The analyzed absorption bands are those centred on 3845 cm-1 (2.6 ?m) and on 4235 cm-1 (2.36 ?m), respectively. The geographical distribution of water vapour and carbon monoxide in the Martian atmosphere highlights longitudinal wave phenomena. These could be related to the existence of atmospheric planetary waves. The longitudinal trends show a sinusoidal behaviour of the gaseous concentration with wave numbers s = 1 for CO and s = 2 for H2O, prevalently. The comparison between these trends and vertical thermal profiles, measured by PFS, suggests a relation between the wave number and the vertical distribution of the examined gasses.

Sindoni, G.; Giuranna, M.; Grassi, D.; Formisano, V.

2011-10-01

227

Secular resonance in extrasolar system  

NASA Astrophysics Data System (ADS)

The two orbits in the HD 160691 planetary system at first appeared highly unstable, but using a new technique called MEGNO (the acronym of Mean Exponential Growth factor of Nearby Orbits), we were able to identify a stability valley in the parameter space. This stability zone is due to the 2:1 mean motion resonance coupled with relative orbital positions of the planets avoiding close approaches in the closeness of their periastron, the two apsidal lines being anti-aligned. The mechanism itself is preserved by librations of the mean motion resonance variables while the longitudes of periapse on average precess at the same rate. The secular resonance variable of the HD 160691 system librates around 180o while it librates around 0o in the Gliese 876 system. We present an extended study of such mechanisms to the Io-Europa pair and the planetary system HD 82943 in order to compare in details these four original cases of secular resonances associated to the 2:1 resonance (Io-Europa, Gliese 876, HD 82943, HD 160691). We concluded that in order to be dynamically stable, the extrasolar planetary systems close to the 2:1 mean motion resonance have to satisfy an apsidal secular resonance and apparently high eccentricities. Because of high eccentricities of the orbits, and despite their relatively small semi-major axes, the relative distances between the two planets may indeed remain sufficiently large over the whole evolutionary time scale of the system.

Rambaux, N.; Bois, E.

2003-04-01

228

Does the HD 209458 planetary system pose a challenge to the stellar atmosphere models?  

NASA Astrophysics Data System (ADS)

Aims: There are very few comparisons between theoretical and empirical limb-darkening coefficients (LDCs). To develop this scenario, we analyse the case of the HD 209458 planetary system for which 10 passband measurements of linear and quadratic LDCs are available. Methods: The empirical data for HD 209458 were derived from the light curves obtained with the Hubble Space Telescope (HST). Since the corresponding effective wavelengths differ from those usually adopted, we computed monochromatic calculations to gain some insight into the problem. The theoretical LDCs were computed by adopting the least-squares method (LSM) but with a larger numerical resolution (100 ? points instead of 11). The flux conservation method (FCM) was also applied. The plane-parallel stellar atmosphere model ATLAS and the spherically symmetrical PHOENIX model were adopted in the calculations. Results: We found systematic disagreement between the theoretical and empirical LDCs for the linear case. Disagreements are also found when we compared the quadratic LDCs with observations. Even taking into account uncertainties in the metallicity, micro-turbulent velocity, and effective temperature in the calculation of the theoretical LDCs, the corresponding shifted curves cannot match the empirical data. It seems that the current atmosphere models are unable to explain the specific intensity distribution of HD 209458.

Claret, A.

2009-11-01

229

In-situ exploration of planetary upper atmospheres with balloons ejected from sounding rockets and space probes  

NASA Astrophysics Data System (ADS)

Balloon missions have been used extensively on Earth to study a large variety of atmospheric characteristics and phenomena. Of primary interest are in situ temperature, pressure and density profiles and wind velocities. The first planetary balloons were flown in the mid 1980s with the Vega 1 and 2 missions to Venus. Since then, balloons have been further developed and planed for, e.g., Mars and Titan. Testing those technologies first on Earth made sense because Earths upper (neutral) atmosphere provides many similarities to Mars atmosphere. The aim of this presentation is to provide a brief overview of the current state in scientific ballooning, and in particular report on the expertise obtained through the MIRIAM (Main Inflated Re-entry Into the Atmosphere Mission Test) Mars balloon near space deployment experiments. The test ballute MIRIAM was flown on board a REXUS 4 sounding rocket from ESRANGE in northern Sweden on October 22nd, 2008. The balloon was deployed at about 140 km altitude. On board were optical instruments, magnetometers, temperature sensors and barometers for atmospheric studies. The data gathered during decent was used to validate inflation, deployment concepts and planetary balloon technologies. Based on those results a new ballute probe MIRIAM-2 is under construction. Its aim is the recording atmospheric parameters which will be then compared to Earth upper atmospheric models. Finally, we address and discuss future prospects for balloon in situ exploration of Mars atmosphere.

Danielides, Michael; Griebel, Hannes; Bayler, Klaus; Herholz, J.

230

Planetary Systems and the Origins of Life  

NASA Astrophysics Data System (ADS)

Preface; Part I. Planetary Systems and the Origins of Life: 1. Observations of extrasolar planetary systems Shay Zucker; 2. The atmospheres of extrasolar planets L. Jeremy Richardson and Sara Seager; 3. Terrestrial planet formation Edward Thommes; 4. Protoplanetary disks, amino acids and the genetic code Paul Higgs and Ralph Pudritz; 5. Emergent phenomena in biology: the origin of cellular life David Deamer; Part II. Life on Earth: 6. Extremophiles: defining the envelope for the search for life in the Universe Lynn Rothschild; 7. Hyperthermophilic life on Earth - and on Mars? Karl Stetter; 8. Phylogenomics: how far back in the past can we go? Henner Brinkmann, Denis Baurain and Hervé Philippe; 9. Horizontal gene transfer, gene histories and the root of the tree of life Olga Zhaxybayeva and J. Peter Gogarten; 10. Evolutionary innovation versus ecological incumbency Adolf Seilacher; 11. Gradual origins for the Metazoans Alexandra Pontefract and Jonathan Stone; Part III. Life in the Solar System?: 12. The search for life on Mars Chris McKay; 13. Life in the dark dune spots of Mars: a testable hypothesis Eörs Szathmary, Tibor Ganti, Tamas Pocs, Andras Horvath, Akos Kereszturi, Szaniszlo Berzci and Andras Sik; 14. Titan: a new astrobiological vision from the Cassini-Huygens data François Raulin; 15. Europa, the Ocean Moon: tides, permeable ice, and life Richard Greenberg; Index.

Pudritz, Ralph; Higgs, Paul; Stone, Jonathon

2013-01-01

231

Exploring Hot Neptune Atmospheres  

NASA Astrophysics Data System (ADS)

The first transiting 'hot Neptune'' GJ 436b inhabits an entirely new region of phase space for extrasolar planetary atmospheres. This relatively cool, low-mass object should be the first transiting extrasolar planet to sport a methane-rich atmosphere. Like Uranus and Neptune it may also have an atmosphere highly enriched in heavy elements. Our experience with the complex atmospheres of the known hot-Jupiters has demonstrated that insights are best gained through the combination of Spitzer observations and atmospheric modeling . However, no models have investigated the atmospheres of Neptune-class exoplanets, which may well be super metal-enriched, and span a wider range in stellar insolation and atmospheric composition than we have previously encountered. GJ 436b the coldest transiting planet, is in entirely new irradiation and mass regimes and is also the target of a barrage of planned Spitzer observations. Here we propose a new generation of atmospheric modeling to understand Spitzer observations of this new planet and others like it.

Fortney, Jonathan; Marley, Mark; Saumon, Didier

2008-03-01

232

Planetary Interior Evolution and Life  

NASA Astrophysics Data System (ADS)

The habitability of planets has received increasing interest in recent years, in particular in view of the increasing number of detected extrasolar planets. Planetary habitability (for life as we know it) is usually thought to require water on (or near) the surface, a magnetic field to protect life against radiation, and transport mechanisms for nutrients. A chemoautotrophic biosphere would also require volcanic activity and the associated large thermal gradients. Volcanic activity is usually thought to have been instrumental for the formation of (initially chemoautotrophic) life on Earth. A magnetic field also serves to protect an existing atmosphere against erosion by the solar wind and thus helps to stabilize the presence of water and habitability. Magnetic fields are generated in the cores of the terrestrial planets and thus habitability is linked to the evolution of the interior through magnetic field generation and volcanic activity. Moreover, the interior is a potential source and sink for water and may interact with the surface and atmosphere reservoirs through volcanic activity and recycling. The most efficient known mechanism for recycling is plate tectonics. Plate tectonics is known to operate, at present, only on the Earth, although Mars may have had a phase of plate tectonics as may have Venus. Plate tectonics also supports the generation of magnetic fields by effectively cooling the deep interior. (In addition, plate tectonics rejuvenates nutrients on the surface and generates granitic cratons.) On the Earth, surface water is stabilized by complex interactions between the atmosphere, the biosphere, the oceans, the crust, and the deep interior in the carbon-silicate cycle. As plate tectonics is widely believed to require water in the mantle to operate, it can be argued that plate tectonics is another element linking the biosphere to the evolution of the planet's interior. Single-plate tectonics associated with stagnant lid convection would also allow for transfer water from the interior through volcanism but a simple recycling mechanism is lacking for this tectonic style. Stagnant lid convection will evolve to thicken the lid and increasingly frustrate volcanic activity and degassing, though. The question of whether or not extrasolar earthlike planets more massive than the Earth are likely to have plate tectonics or rather single-plate tectonics is hotly debated. We would argue that the large interior pressure and its effect on the rheology of the mantle of these planets may frustrate plate tectonics and magnetic field generation altogether. We would even argue that surface volcanic activity may become increasingly difficult with increasing mass of a rocky planet. On Earth, mantle melt is buoyant at depths smaller than 200 - 300km. At larger than this critical depth, the melt will be negatively buoyant because of its greater compressibility in comparison with that of solid rock. The critical depth below which melt ceases to be buoyant will decrease with increasing mass of the planet and may become shallower than the depth to the base of the stagnant lid of mantle convection on massive terrestrial extrasolar planets. We find the ratio between the stagnant lid thickness and the critical depth to increase approximately linearly with the radius of the planet. The great diversity of extrasolar planets may suggest a diversity of life forms and associated habitability parameters, however, and extrapolations from the Earth may be overly naive.The habitability of planets has received increasing interest in recent years, in particular in view of the increasing number of detected extrasolar planets. Planetary habitability (for life as we know it) is usually thought to require water on (or near) the surface, a magnetic field to protect life against radiation, and transport mechanisms for nutrients. A chemoautotrophic biosphere would also require volcanic activity and the associated large thermal gradients. Volcanic activity is usually thought to have been instrumental for the formation of (initially chemoautotrophic) li

Spohn, T.; Noack, L.; Hoening, D.; Breuer, D.

2012-04-01

233

THE COMPOSITIONAL DIVERSITY OF EXTRASOLAR TERRESTRIAL PLANETS. I. IN SITU SIMULATIONS  

SciTech Connect

Extrasolar planet host stars have been found to be enriched in key planet-building elements. These enrichments have the potential to drastically alter the composition of material available for terrestrial planet formation. Here, we report on the combination of dynamical models of late-stage terrestrial planet formation within known extrasolar planetary systems with chemical equilibrium models of the composition of solid material within the disk. This allows us to determine the bulk elemental composition of simulated extrasolar terrestrial planets. A wide variety of resulting planetary compositions are found, ranging from those that are essentially 'Earth like', containing metallic Fe and Mg silicates, to those that are dominated by graphite and SiC. This shows that a diverse range of terrestrial planets may exist within extrasolar planetary systems.

Bond, Jade C.; Lauretta, Dante S. [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); O'Brien, David P., E-mail: jbond@psi.ed [Planetary Science Institute, 1700 E. Fort Lowell, Tucson, AZ 85719 (United States)

2010-06-01

234

Detection of Oxygen and Carbon in the Hydrodynamically Escaping Atmosphere of the Extrasolar Planet HD 209458b  

NASA Astrophysics Data System (ADS)

Four transits of the planet orbiting the star HD 209458 were observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. The wavelength domain (1180-1710 Å) includes H I as well as C I, C II, C IV, N V, O I, S I, Si II, Si III, and Si IV lines. During the transits, absorptions are detected in H I, O I, and C II (5%+/-2%, 13%+/-4.5%, and 7.5%+/-3.5%, respectively). No absorptions are detected for other lines. The 5% mean absorption over the whole H I Ly? line is consistent with the previous detection completed in 2003 at higher resolution (Vidal-Madjar et al.). The absorption depths in O I and C II show that oxygen and carbon are present in the extended upper atmosphere of HD 209458b (nicknamed ``Osiris''). These species must be carried out up to the Roche lobe and beyond, most likely in a state of hydrodynamic escape.

Vidal-Madjar, A.; Désert, J.-M.; Lecavelier des Etangs, A.; Hébrard, G.; Ballester, G. E.; Ehrenreich, D.; Ferlet, R.; McConnell, J. C.; Mayor, M.; Parkinson, C. D.

2004-03-01

235

Solution of the non-LTE problem for molecular gas in planetary atmospheres: superiority of accelerated lambda iteration  

Microsoft Academic Search

A general formulation is given of the multi-level rotation–vibrational non-LTE problem for a mixture of radiating molecular gases in a planetary atmosphere, treating explicitly the coupling of molecular energy levels by collisionally induced energy transfer processes and by band overlap. Various limiting cases of non-LTE effects are discussed. Three techniques—lambda iteration, matrix and accelerated lambda iteration—which are used to solve

A. A. Kutepov; O. A. Gusev; V. P. Ogibalov

1998-01-01

236

Sensitivity of planetary boundary layer atmosphere to historical and future changes of land use\\/land cover, vegetation fraction, and soil moisture in Western Kentucky, USA  

Microsoft Academic Search

Changes in land use land cover (LULCC), vegetation fraction (FV), and soil moisture affects land surface atmosphere interactions, characteristics of planetary boundary layer (PBL), and near surface atmospheric moisture content. Previous studies have investigated impacts of LULC, FV, and soil moisture changes on atmosphere separately. The present study investigates the combined impacts of changes in LULC, FV, and soil moisture,

Rezaul Mahmood; Ronnie Leeper; Arturo I. Quintanar

2011-01-01

237

Detecting Extrasolar Planets With Millimeter-Wave Observatories  

NASA Astrophysics Data System (ADS)

Do nearby stars have planetary systems like our own? How do such systems evolve? How common are such systems? Proposed radio observatories operating at millimeter wavelengths could start answering these questions within the next 6-10 years, according to scientists at the National Radio Astronomy Observatory (NRAO). Bryan Butler, Robert Brown, Richard Simon, Al Wootten and Darrel Emerson, all of NRAO, presented their findings today to the American Astronomical Society meeting in San Antonio, TX. Detecting planets circling other stars is a particularly difficult task, and only a few such planets have been discovered so far. In order to answer fundamental questions about planetary systems and their origin, scientists need to find and study many more extrasolar planets. According to the NRAO scientists, millimeter-wavelength observatories could provide valuable information about extrasolar planetary systems at all stages of their evolution. "With instruments planned by 2005, we could detect planets the size of Jupiter around a solar-type star out to a distance of 100 light-years," said Robert Brown, Associate Director of NRAO. "That means," he added, "that we could survey approximately 2,000 stars of different types to learn if they have planets this size." Millimeter waves occupy the portion of the electromagnetic spectrum between radio microwaves and infrared waves. Telescopes for observing at millimeter wavelengths utilize advanced electronic equipment similar to that used in radio telescopes observing at longer wavelengths. Millimeter-wave observatories offer a number of advantages in the search for extrasolar planets. Planned multi-antenna millimeter-wave telescopes can provide much higher resolving power, or ability to see fine detail, than current optical or infrared telescopes. Millimeter-wave observations would not be degraded by interference from the "zodiacal light" reflected by interplanetary dust, either in the extrasolar system or our own solar system. Another important advantage is that, at millimeter wavelengths, the star's brightness poses less of a problem for observers because, while it is still brighter than a planet, the difference in brightness between the two is far less. Because of the physical nature of the objects themselves, protoplanets in different stages of formation could readily be detected by advanced millimeter-wave observatories. The observatories that could provide these advantages are the Millimeter Array (MMA), a proposed 40-antenna millimeter-wave telescope that could be operational by 2005, and an upgraded version of the existing Very Large Array (VLA), a 27-antenna radio telescope in New Mexico. The MMA is a radio telescope designed to operate at wavelengths from 11.5 millimeters down to 0.5 millimeters, or frequencies from 26 to 650 GHz. It will use 40 precision antennas, each 8 meters in diameter, all operating in concert to produce extremely high- resolution images. As is done with the existing VLA and VLBA radio telescopes, the signals from all the MMA antennas will be processed in a special-purpose computer called a correlator. The processing of the signals corrects for atmospheric propagation effects and for the fact that the "synthesized telescope" is in fact made up of individual antennas. Planning for the MMA began as early as 1983, and a number of scientific workshops have allowed U.S. researchers to make known their needs for a millimeter-wave observatory to serve a wide variety of specialties. The National Science Foundation (NSF) provided initial design funding to NRAO in 1995 for MMA studies. Currently, MMA efforts are centered on selecting an appropriate site, which must be very high, dry and flat. A site at 16,500 feet elevation in northern Chile is now being tested. Hawaii's Mauna Kea is also under consideration. If funding is approved for the MMA, the instrument could be in operation by the year 2005. The MMA is expected to be an international instrument, with funding from both U.S. and foreign sources. The MMA will b

1996-01-01

238

Characterizing Extrasolar Earths  

NASA Astrophysics Data System (ADS)

For thousands of years people have wondered, are we alone? Is there life elsewhere in the Universe? For the first time in human history we are on the way to being able to answer this question by plans to search for Earth-like extrasolar planets. This review summarizes the current state of the scientific motivation for Earth-like planet detection and characterization. The relevance of the June 2004 transit of Venus to the the characterization of extrasolar planets is also discussed.

Seager, Sara

2004-06-01

239

Abundances in stars with planetary systems  

Microsoft Academic Search

Extensive spectroscopic studies of stars with and without planetary systems have concluded that planet host stars are more metal-rich than those without detectable planets. More subtle trends of different chemical elements begin to appear as the number of detected extrasolar planetary systems continues to grow. I review our current knowledge concerning the observed abundance trends of light and heavy elements

Garik Israelian

2008-01-01

240

Seeing the Invisible: Educating the Public on Planetary Magnetic Fields and How they Affect Atmospheres  

Microsoft Academic Search

Magnetic fields and charged particles are difficult for school children, the general public, and scientists alike to visualize. But studies of planetary magnetospheres and ionospheres have broad implications for planetary evolution, from the deep interior to the ancient climate, that are important to communicate to each of these audiences. This presentation will highlight the visualization materials that we are developing

M. O. Fillingim; D. A. Brain; L. M. Peticolas; G. Schultz; D. Yan; S. Guevara; S. Randol

2010-01-01

241

Seeing the Invisible: Educating the Public on Planetary Magnetic Fields and How they Affect Atmospheres  

Microsoft Academic Search

Magnetic fields and charged particles are difficult for school children, the general public, and scientists alike to visualize. But studies of planetary magnetospheres and ionospheres have broad implications for planetary evolution, from the deep interior to the ancient climate, that are important to communicate to each of these audiences. This presentation will highlight the visualization materials that we are developing

M. O. Fillingim; D. A. Brain; L. M. Peticolas; G. Schultz; D. Yan; S. Guevara; S. Randol

2009-01-01

242

Comparative analysis of chemical composition and optical properties of gaseous and disperse phases of the earth-group planetary atmospheres  

NASA Astrophysics Data System (ADS)

The chemical compositions and optical properties of the gaseous and aerosol components of the atmospheres of the earth, Mars and Venus are compared. On the basis of laboratory absorption spectra of the major absorbing species in the planetary atmospheres (CO2, N2, O2, CO and H2O) at temperatures between 200 and 800 K and pressures up to 70 atm, a numerical modelling program is used to determine the radiative transfer within the atmospheres from the fine structure observed in their absorption spectra. For the case of Venus, a multi-component model is proposed of a cloud cover and haze consisting of an H2SO4 solution and sulfur particle fractions. The aerosol component of the Mars atmosphere is represented by a dust aerosol of different size distributions, the optical properties of which change in response to dust storms. The short-wave and long-wave radiative transfer properties of the planetary atmospheres are noted to correspond to the observed climatic conditions, validating the closed parameterization of optical properties and radiative heat transfer used to derive the structural characteristics.

Kondrat'ev, K. Ya.; Moskalenko, N. I.

243

A Balloon-Borne Telescope System for Planetary Atmosphere and Plasma Studies  

NASA Astrophysics Data System (ADS)

A telescope floating in the polar stratosphere can continuously monitor planets for more than 24 hours. Thin, clear and stable air of the stratosphere makes it possible to observe planets in a condition free from cloud with fine seeing and high atmospheric transmittance. Moreover, a balloon-borne telescope system is less expensive compared with a huge terrestrial telescope or a direct planetary probe mission. Targets of a balloon-borne telescope system will extend over various atmospheric and plasma phenomena on almost all the planets, i.e., a sodium tail of Mercury, lightning, airglow and aurora in the atmospheres of Venus, Jupiter and Saturn, escaping atmospheres of the Earth-type planets, satellite-induced luminous events in the Jovian atmosphere, etc. The first target is global dynamics of the Venusian atmosphere by detecting cloud motion in UV and NIR imagery. A decoupling mechanism and a pair of control moment gyros (CMGs) are mounted at the top of the gondola. The decoupling mechanism isolates the gondola from a balloon and also transfers an excess angular momentum of the CMGs to the balloon. The attitude of the gondola is stabilized at a constant sun azimuthal angle so that a solar cell panel faces to the sun. A 300 mm F30 Schmidt-Cassegrain telescope is installed at the bottom of the gondola. DC/DC converters, a PC, a high voltage power supply for a piezo-electrically moving mirror and digital video recorders are contained in a sealed cell. The azimuthal angle is detected by a sun-sensor. A PC processes sensor output to control DC motors used in the decoupling mechanism and CMGs with an accuracy in azimuthal attitude of about 0.5 deg. The two-axis gimbal mount of the telescope is controlled by the same PC, guiding an object within a field-of-view of a guide telescope. Residual tracking error is detected by a position sensitive photomultiplier tube and corrected by the two-axis moving mirror installed in the optical system. The optical path is divided into three paths with different colors: the first one with wavelengths less than 450 nm, the second one with 550-630 nm, and the last one more than 750 nm. The first and last paths are utilized for imagery of UV and NIR with bandpass filters and analog and digital CCD video cameras, respectively. The second path is for tracking error detection. The first experiment was scheduled in June, 2007 at Sanriku Balloon Center (SBC), Japan, but it was postponed until late August because of delay in final testing of the system. As of submission of this abstract the gondola has been ready for launch but has not yet been launched. The result of experiment will be presented.

Taguchi, M.; Yoshida, K.; Sakamoto, Y.; Kanazawa, T.; Shoji, Y.; Sawakami, T.; Takahashi, Y.; Hoshino, N.; Sato, T.; Sakanoi, T.

2007-12-01

244

Reflection and thermal emission spectra of Earth-like extrasolar planets affected by clouds  

NASA Astrophysics Data System (ADS)

Clouds can have an important impact on the radiative transfer in planetary atmospheres by absorption and scattering of the incident stellar radiation and the thermal radiation from the surface. Consequently, the planetary emission and reflection spectra are strongly affected by the presence of clouds, resulting in e.g. the concealing of thermal surface emissions or dampening of molecular absorption bands in the infrared. To study these effects, a parametrised cloud description, accounting for two different types of clouds (low-level water and high-level ice clouds) and their partial overlap has been developed. The multi-layered cloud model is based on observations in the Earth's atmosphere and has been coupled with a one-dimensional radiative-convective steady state climate model to obtain low-resolution spectra of Earth-like extrasolar planets. In this contribution the impact of multi-layered on low-resolution thermal emission and reflec-tion spectra is presented for Earth-like planets orbiting different types of central stars, with special emphasis on so-called biomarker signatures. The influence of clouds on the ability to derive information about the planetary surface temperatures from low-resolution spectra is also discussed.

Kitzmann, Daniel; Patzer, A. B. C.; von Paris, Philip; Rauer, Heike

245

DETECTING OCEANS ON EXTRASOLAR PLANETS USING THE GLINT EFFECT  

SciTech Connect

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

Robinson, Tyler D.; Meadows, Victoria S. [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Crisp, David, E-mail: robinson@astro.washington.ed [Jet Propulsion Laboratory, Pasadena, CA 91109 (United States)

2010-09-20

246

Detecting Oceans on Extrasolar Planets Using the Glint Effect  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

247

The Hunt for Extrasolar Planets at McDonald Observatory  

NASA Astrophysics Data System (ADS)

Currently every major telescope at McDonald Observatory is utilized in the search for extrasolar planets. We review the different planet search efforts and present the results of these programs. In particular we describe in detail the on-going precise Doppler surveys at the Harlan J. Smith 2.7 m telescope and at the Hobby-Eberly Telescope (HET). The highlight of the HET program was last year's discovery of a "Hot Neptune" in the ? planetary system. With a mass of only 17 Earth masses this object demonstrates our ability to detect extrasolar planets with masses below the gas giant range.

Endl, M.; Cochran, W. D.; Hatzes, A. P.; Wittenmyer, R. A.

2005-10-01

248

Photochemical abiotic synthesis of amino-acid precursors from simulated planetary atmospheres by vacuum ultraviolet light  

SciTech Connect

For the purpose of investigating the photon energy dependence of the photoinduced abiotic synthesis of organic molecules, gas mixtures that simulate typical planetary atmospheres, including a carbon source (CO or CH{sub 4}), a nitrogen source (N{sub 2} or NH{sub 3}), and H{sub 2}O, were irradiated with synchrotron radiation through a vacuum-ultraviolet transmitting window. Three kinds of window material, fused silica, synthetic quartz, and MgF{sub 2}, were used as a high-energy-cutting filter, whose absorption-edge energies are 6.4, 8.1, and 10.5 eV, respectively. Three types of gas mixture, Titan-type (CH{sub 4}-N{sub 2}-H{sub 2}O), comet-type (CO-NH{sub 3}-H{sub 2}O), and primitive-Earth-type (CO-N{sub 2}-H{sub 2}O), were irradiated with vacuum-ultraviolet photons in the three energy ranges. After the irradiation, amino-acid formation yields in the acid-hydrolyzed solution of the product were measured with a high-performance liquid chromatograph method. From the Titan- and comet-type mixtures, amino acids were detected by irradiation with photons lower than 8.1 eV. For both mixtures, the averaged quantum yields of glycine generation in the photon energy region of 7-10.5 eV were of the order of 10{sup -5}, which was larger by about one order than that in the region 5-8 eV. On the other hand, from the primitive-Earth-type mixture, amino-acid formation was difficult to detect even with irradiation as high as 10.5 eV, even though amino acids were generated in comparable yields from the Titan- and comet-type mixtures by irradiation with soft x rays or proton beam, whose energies are much higher. These results suggest that the vacuum ultraviolet light is a more effective energy source for the generation of the precursors of bioorganic compounds in extraterrestrial environments than in primitive-Earth atmosphere.

Takahashi, Jun-ichi; Masuda, Hitomi; Kaneko, Takeo; Kobayashi, Kensei; Saito, Takeshi; Hosokawa, Teruo [Nippon Telegraph and Telephone Corporation (NTT) Microsystem Integration Laboratories, 3-I Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan); Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501 (Japan); Institute for Cosmic Ray Research, The University of Tokyo, 3-2-1 Midori-cho, Tanashi, Tokyo 188-8502 (Japan); NTT Electronics, Co. Ltd., 1841-I, Tsuruma, Machida, Tokyo 194-0004 (Japan)

2005-07-15

249

Baroclinic instability on hot extrasolar planets  

NASA Astrophysics Data System (ADS)

We investigate baroclinic instability in flow conditions relevant to hot extrasolar planets. The instability is important for transporting and mixing heat, as well as for influencing large-scale variability on the planets. Both linear normal mode analysis and non-linear initial-value calculations are carried out - focusing on the freely-evolving, adiabatic situation. Using a high-resolution general circulation model (GCM) which solves the traditional primitive equations, we show that large-scale jets similar to those observed in current GCM simulations of hot extrasolar giant planets are likely to be baroclinically unstable, on a timescale of a few to a few tens of planetary rotations, generating cyclones and anticyclones that drive weather systems. The growth rate and scale of the most unstable mode obtained in the linear analysis are in qualitative, good agreement with the full non-linear calculations. In general, unstable jets evolve differently depending on their signs (eastward or westward), due to the change in sign of the jet curvature. For jets located at or near the equator, instability is strong at the flanks - but not at the core. Crucially, the instability is either poorly or not at all captured in simulations with low resolution and/or high artificial viscosity. Hence, the instability has not been observed or emphasized in past circulation studies of hot extrasolar planets.

Polichtchouk, I.; Cho, J. Y.-K.

2012-08-01

250

The Extrasolar Planets Encyclopaedia  

NSDL National Science Digital Library

Jean Schneider, of the Observatoire de Paris, put together this no-nonsense site featuring current information on the "detection and study of extrasolar planets, including exobiology." Schneider's commitment to the subject is clear with the inclusion of detailed scientific and technical articles, a tutorial (by Arizona State University) on the detection of extrasolar planets, and a hyperlinked bibliography of some 200 scientific journal articles, books, and reports. A catalog of extrasolar planets (with links to the scientific articles describing them) features dozens of confirmed planets (or brown dwarfs) around main sequence stars or pulsars, in addition to disks and unconfirmed objects. Whether you are a dedicated amateur or pro (and read English or French), these pages are clearly designed and well worth the orbit.

251

Direct Detection of C4H2 Photochemical Products: Possible Routes to Complex Hydrocarbons in Planetary Atmospheres.  

PubMed

The photochemistry of diacetylene (C4H2), the largest hydrocarbon to be unambiguously identified in planetary atmospheres, is of considerable importance to understanding the mechanisms by which complex molecules are formed in the solar system. In this work, the primary products of C4H2's ultraviolet photochemistry were determined in a two-laser pump-probe scheme in which the products of C4H2 photoexcitation are detected by vacuum ultraviolet photoionization in a time-of-flight mass spectrometer. Three larger hydrocarbon primary products were observed with good yield in the C4H2* + C4H2 reaction: C6H2, C812, and C8H3. Neither C6H2 nor C8H3 is anticipated by current photochemical models of the atmospheres of Titan, Uranus, Neptune, Pluto, and Triton. The free hydrogen atoms that are released during the formation of the C8H3 and C8H2 products also may partially offset the role of C4H2 in catalysing the recombination of free hydrogen atoms in the planetary atmospheres. PMID:17742532

Bandy, R E; Lakshminarayan, C; Frost, R K; Zwier, T S

1992-12-01

252

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

SciTech Connect

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

Carter-Bond, Jade C. [School of Physics, University of New South Wales, Kensington, NSW 2052 (Australia); O'Brien, David P. [Planetary Science Institute, 1700 East Fort Lowell, Tucson, AZ 85719 (United States); Raymond, Sean N., E-mail: j.bond@unsw.edu.au [Observatoire Aquitain des Sciences de l'Univers, Universite de Bordeaux, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France)

2012-11-20

253

Origin of planetary atmospheres and their role in the evolution of life  

Microsoft Academic Search

The successful synthesis of amino acids in a reducing gas mixture presumably resembling the primary Earth atmosphere, by the Miller-Urey experiment, had a long lasting influence on the general perception of such an early atmosphere. Based on atmospheric escape, such a reducing atmosphere, however, has a lifetime of only millions of years. According to present view the early atmosphere of

Siegfried J. Bauer

2002-01-01

254

The Transits of Extrasolar Planets with Moons  

NASA Astrophysics Data System (ADS)

The search for extrasolar planets is strongly motivated by the goal of characterizing how frequent habitable worlds and life may be within the Galaxy. Whilst much effort has been spent on searching for Earth-like planets, large moons may also be common, temperate abodes for life as well. The methods to detect extrasolar moons, or "exomoons" are more subtle than their planetary counterparts and in this thesis I aim to provide a method to find such bodies in transiting systems, which offer the greatest potential for detection. Before one can search for the tiny perturbations to the planetary signal, an understanding of the planetary transit must be established. Therefore, in Chapters 3 to 5 I discuss the transit model and provide several new insights. Chapter 4 presents new analytic expressions for the times of transit minima and the transit duration, which will be critical in the later search for exomoons. Chapter 5 discusses two sources of distortion to the transit signal, namely blending (with a focus on the previously unconsidered self-blending scenario) and light curve smearing due to long integration times. I provide methods to compensate for both of these effects, thus permitting for the accurate modelling of the planetary transit light curve. In Chapter 6, I discuss methods to detect exomoons through their gravitational influence on the host planet, giving rise to transit timing and duration variations (TTV and TDV). The previously known TTV effect is updated with a new model and the associated critical problems are outlined. I then predict a new effect, TDV, which solves these problems, making exomoon detection viable. Chapter 7 presents a feasibility study for detecting habitable-zone exomoons with Kepler, where it is found that moons down to 0.2 Earth masses are detectable. Finally, conclusions and future work are discussed in Chapter 8.

Kipping, David M.

2011-05-01

255

Towards detecting and characterizing Earth-like extrasolar planets  

NASA Astrophysics Data System (ADS)

Extrasolar planet detection methods have recently advanced to the point where planets only slightly larger than the Earth, both in mass and size, are detectable with currently available instruments. The newly discovered class of planets known as "super-Earths" with masses in the range 1-10 M (+) afford scientists the ability to study planets and planet formation scenarios in a mass regime that does not exist in our solar system. This thesis describes work aimed at both detecting and characterizing these low-mass planets. If a transiting planet is found to vary in its measured orbital period over a series of transits, the resulting transit timing variations (TTVs) may be due to the gravitational pull of an additional planet in the system. The first part of this thesis (Chapters 2-4) describes some of the first efforts to use the TTV method to detect low-mass planets in known transiting systems. In Chapters 2 and 3 we present transit timing measurements for both the HD 209458 and HD 189733 systems, using data from the Canadian MOST space telescope. We additionally study the effects of HID 189733's large surface star spots on measuring accurate transit times in Chapter 4. While we find no evidence of low-mass companion planets in either of these transiting hot Jupiter systems, the null results from our TTV analyses serve to provide strong constraints on planet formation theories. Characterization of super-Earth atmospheres will be possible with future instruments, such as those aboard the James Webb Space Telescope. However, the interpretation of any such observations will necessitate direct comparison against theoretical atmosphere models. To this end, we have developed a planetary atmosphere model specifically for the study of super-Earths, and we present this model and some of its applications in Chapters 5-7. In Chapter 5 we determine how to best constrain the atmospheric hydrogen content of a super- Earth atmosphere through observations of the planetary emission and transmission spectrum. In Chapter 6 we turn our attention to the problem of direct detection of low-mass planets with next generation ELTs. We conclude this thesis in Chapter 7, where we describe the recent addition of a self- consistent temperature correction routine to the model atmosphere.

Miller-Ricci, Eliza

256

Possibilities for the Detection of Microbial Life on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

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.

Knacke, Roger F.

2003-11-01

257

Extrasolar Carbon Planets  

Microsoft Academic Search

We suggest that some extrasolar planets <~ 60 Earth masses will form substantially from silicon carbide and other carbon compounds. Pulsar planets and low-mass white dwarf planets are especially good candidate members of this new class of planets, but these objects could also conceivably form around stars like the Sun. This planet-formation pathway requires only a factor of two local

Marc J. Kuchner; S. Seager

2005-01-01

258

The influence of atmospheric tide and planetary wave variability during sudden stratosphere warmings on the low latitude ionosphere  

NASA Astrophysics Data System (ADS)

Numerical simulations are performed for a sudden stratosphere warming (SSW) under different atmospheric tide and planetary wave forcing conditions to investigate the tidal variability in the mesosphere and lower thermosphere (MLT). The influence of variability of different tides in the MLT on generating perturbations to the low latitude ionosphere is also investigated. Significant changes are found to occur in the migrating semidiurnal solar (SW2) and lunar (M2) tides as well as in the westward propagating nonmigrating semidiurnal tide with zonal wave number 1 (SW1). The changes in the zonal mean atmosphere that occur during SSWs lead to an enhancement in the SW2 and M2 tides. The vertical wavelength of the SW2 is also changed, resulting in phase variability in the SW2 at a constant altitude. Significant enhancements in the SW1 are found to occur only in the presence of additional planetary wave forcing, and this demonstrates that nonlinear planetary wave?tide interactions lead to the enhanced SW1 during SSWs. The amplitude and phase variability of the SW2 is found to be capable of producing temporal variability in the vertical plasma drift velocity that is similar to the observed variability. Changes in the M2 during SSWs can contribute up to an additional ˜30% of the total ionosphere variability; however, the overall influence of the lunar tide is found to be dependent upon the phase of the moon relative to the timing of the SSW. Although the influence is relatively minor, the SW1 also contributes to the low latitude ionosphere variability during SSWs. The simulation results for the vertical plasma drift velocity and total electron content (TEC) further illustrate that significant longitude variability occurs in the ionosphere response to SSWs.

Pedatella, N. M.; Liu, H.-L.

2013-08-01

259

Laboratory measurement of charge exchange X-ray emission for diagnosing the Solar wind and planetary and cometary atmospheres  

NASA Astrophysics Data System (ADS)

We have used the EBIT-I electron beam ion trap located at the University of California Lawrence Livermore National Laboratory and a microcalorimeter array to create and measure the X-ray emission from charge exchange recombination reactions. The microcalorimeter array, dubbed the XRS/EBIT, was built by the NASA-Goddard Space Flight Center/University of Wisconsin collaboration and is in operation at the LLNL EBIT-I facility. It consists of 32 independent microcalorimeter elements that work in concert to provide a large collection area, high-resolution, large bandwidth x-ray spectrometer. Our studies have focussed on X-ray emission from charge exchange reactions that occur after Solar wind ions interact with cometary or planetary atmospheres. Here we present an overview of our measurement techniques and capabilities, and the utility of our results. This work is especially timely in light of the upcoming launch of the Astro-E2 X-ray observatory which will provide the first ever high resolution X-ray spectrum emitted from a comet. This work was performed under the auspices of the Department of Energy by UC-LLNL under contract W-7405-ENG-48 and supported by NASA's Planetary Atmospheres Program under Work Order W-19,938.

Brown, G. V.; Beiersdorfer, P.; Boyce, K. R.; Chen, H.; Kelley, R.; Kilbourne, C.; Porter, F. S.; Szymkowiak, A.

2005-05-01

260

Stability of fictitious Trojan planets in extrasolar systems  

Microsoft Academic Search

Our work deals with the dynamical possibility that in extrasolar planetary systems a terrestrial planet may have stable orbits in a 1:1 mean motion resonance with a Jovian like planet. We studied the motion of fictitious Trojans around the Lagrangian points L_4\\/L_5 and checked the stability and\\/or chaoticity of their motion with the aid of the Lyapunov Indicators and the

R. Schwarz; R. Dvorak; Á. Süli; B. Érdi

2007-01-01

261

On the probability density distribution of planetary-scale atmospheric wave amplitude  

NASA Astrophysics Data System (ADS)

The statistical properties of a measure of planetary-scale wave activity are investigated in a 16 winter NMC dataset. The probability density distribution of the wavenumber 2 to 4 amplitude is found to be bimodal, confirming earlier results from a smaller dataset. The statistical significance of this result is established empirically with statistical simulations. It is also shown that the bimodality is not connected with any periodicity in the time series. Partitioning the data based on the density estimation reveals two statistical flow regimes in physical space. One corresponds to an amplified planetary-scale wave pattern and the other to a predominantly zonal flow. Both regimes exhibit a baroclinic vertical structure but the difference between them is equivalent barotropic. These differences extend through the depth of the troposphere and appear to be of hemispheric extent.

Hansen, Anthony R.; Sutera, Alfonso

1986-12-01

262

Status of the Calan-Hertfordshire Extrasolar Planet Search  

NASA Astrophysics Data System (ADS)

In these proceedings we give a status update of the Calan-Hertfordshire Extrasolar Planet Search, an international collaboration led from Chile that aims to discover more planets around super metal-rich and Sun-like stars, and then follow these up with precision photometry to hunt for new bright transit planets. We highlight some results from this program, including exoplanet and brown dwarf discoveries, and a possible correlation between metallicity and planetary minimum mass at the lowest planetary masses detectable. Finally we discuss the short-term and long-term future pathways this program can take.

Jenkins, James S.; Jones, Hugh R. A.; Rojo, Patricio; Tuomi, Mikko; Jones, Matias I.; Murgas, Felipe; Barnes, John R.; Pavlenko, Yakiv; Ivanyuk, Oleksiy; Jordán, Andres; Day-Jones, Avril C.; Ruiz, Maria-Teresa; Pinfield, David J.

2013-04-01

263

PlanetWRF - A Flexible, Multi-scale Model For Planetary Atmospheres  

Microsoft Academic Search

PlanetWRF is a global, planetary version of the mesoscale, Earth-based WRF (Weather Research and Forecasting) model (www.wrf-model.org). With minimal changes, and using the same basic dynamical core and parameterizations of physical processes, it may be run as a global, mesoscale, LES (large eddy simulation), latitude-height or one-dimensional model. This makes it exceptionally flexible and applicable to a range of studies,

Mark I. Richardson; C. E. Newman; A. D. Toigo

2006-01-01

264

Planetary Science  

NSDL National Science Digital Library

Astronomy notes is an educational resource for introductory astronomy classes for undergraduates. This section gives a extensive introduction to planetary science. Topics in this portion of the website include properties of planets, such as distance, mass, volume, density, and composition. There is also explanations on escape velocity, temperature, and gravity and how they affect planetary bodies. Other topics included are: the meanining of atmospheric colors, magnetic fields, the magnetic dynamo theory, seismology, differences between Mars, Earth, and Venus, and the properties of rings and moons in our solar system.

Strobel, Nick

2004-07-16

265

Linear relationships between root-zone soil moisture and atmospheric processes in the planetary boundary layer  

Microsoft Academic Search

Soil moisture modulates the exchange of mass and energy between the atmosphere and the land surface. This study focuses on the relationship between soil moisture and atmospheric processes at and near the Norman Mesonet site using both automated and field samples of hydrologic and atmospheric parameters. During 1999, measurements were made during an intensive observing period (IOP) that spanned the

Jeffrey B. Basara; Kenneth C. Crawford

2002-01-01

266

Progress in planetary exploration  

Microsoft Academic Search

Papers are presented in the areas of planetary structure and composition, comparative planetology, the space investigation of comets, asteroids and cosmic dust, planetary atmospheres, Venus observations, the outer planets, and the formation and evolution of the solar system. Specific topics include the magnetic fields of Mercury, Venus and Mars, the chemical composition and optical properties of terrestrial planet atmospheres, results

R. W. Shorthill; M. Ia. Marov; J. A. M. McDonnell

1981-01-01

267

Commission 53: Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Commission 53 was created at the 2006 Prague General Assembly (GA) of the IAU, in recognition of the outburst of astronomical progress in the field of extrasolar planet discovery, characterization, and theoretical work that has occurred since the discovery of the first planet in orbit around a solar-type star in 1995. Commission 53 is the logical successor to the IAU Working Group on Extrasolar Planets (WGESP), which ended its six years of existence in August 2006. The founding President of Commission 53 was Michael Mayor, in honor of his seminal contributions to this new field of astronomy. The current President is Alan Boss, the former chair of the WGESP. The current members of the Commission 53 (C53) Organizing Committee (OC) began their service in August 2009 at the conclusion of the Rio de Janeiro IAU GA.

Boss, Alan; Lecavelier des Etangs, Alain; Mayor, Michel; Bodenheimer, Peter; Collier-Cameron, Andrew; Kokubo, Eiichiro; Mardling, Rosemary; Minniti, Dante; Queloz, Didier

2012-04-01

268

Aerothermodynamics and ground test facilities simulation of planetary entry flows - application to Earth, Mars and Titan atmospheric entries  

NASA Astrophysics Data System (ADS)

The knowledge of the aerothermodynamic environment of space vehicles crossing the upper layers of planetary atmospheres at hypersonic velocities represents a critical issue for dimensioning purposes. In such high-enthalpy flows, dissociation and ionization effects lead to strong departures from chemical and thermodynamic equilibrium. The formation of a highly emissive plasma also implies taking into account radiation emission and absorption effects in the flow, using quantum mechanics calculations. Different complementary ground test facilities allow the simulation of such entry conditions. At the Laboratoire d'Aérothermique, investigations on Earth, Mars and Titan like plasmas have been conducted over the last years in the SR5 rarefied arc-jet plasma wind-tunnel. Experimental investigations include optical emission spectroscopy (OES) and other measurement techniques. Numerical investigations include the development and validation of the line-by-line radiative code SESAM as well as the modelling of the SR5 plasma flow in a fluid mechanics approach using the Navier-Stokes ARES code and several other internal codes. The complementary numerical and experimental investigations conducted at the Laboratoire d'Aérothermique allow an improved qualitative and quantitative knowledge on planetary entry flows which will lead to improved design properties and performance of future space vehicles.

Lino da Silva, M.; Dudeck, M.; Reis, R.

2004-02-01

269

Simulation of a miniature, low-power time-of-flight mass spectrometer for in situ analysis of planetary atmospheres  

NASA Astrophysics Data System (ADS)

We are implementing nano- and micro-technologies to develop a miniaturized electron impact ionization mass spectrometer for planetary science. Microfabrication technology is used to fabricate the ion and electron optics, and a carbon nanotube (CNT) cathode is used to generate the ionizing electron beam. Future NASA planetary science missions demand miniaturized, low power mass spectrometers that exhibit high resolution and sensitivity to search for evidence of past and present habitability on the surface and in the atmosphere of priority targets such as Mars, Titan, Enceladus, Venus, Europa, and short-period comets. Toward this objective, we are developing a miniature, high resolution reflectron time-of-flight mass spectrometer (Mini TOF-MS) that features a low-power CNT field emission electron impact ionization source and microfabricated ion optics and reflectron mass analyzer in a parallel-plate geometry that is scalable. Charged particle electrodynamic modeling (SIMION 8.0.4) is employed to guide the iterative design of electron and ion optic components and to characterize the overall performance of the Mini TOF-MS device via simulation. Miniature (< 1000 cm3) TOF-MS designs (ion source, mass analyzer, detector only) demonstrate simulated mass resolutions > 600 at sensitivity levels on the order of 10-3 cps/molecule N2/cc while consuming 1.3 W of power and are comparable to current spaceflight mass spectrometers. Higher performance designs have also been simulated and indicate mass resolutions ~1000, though at the expense of sensitivity and instrument volume.

King, Todd T.; Getty, Stephanie A.; Roman, Patrick A.; Herrero, Federico A.; Jones, Hollis H.; Kahle, Duncan M.; Lynch, Bernard; Suárez, George; Brinckerhoff, William B.; Mahaffy, Paul R.

2008-05-01

270

Planetary exploration by robotic aerovehicles  

Microsoft Academic Search

Planetary aerobots are a new type of telerobotic science platform that can fly and navigate in a dynamic 3-dimensional atmospheric environment, thus enabling the global in situ exploration of planetary atmospheres and surfaces. Aerobots are enabled by a new concept in planetary balloon altitude control, developed at JPL, which employs reversible-fluid changes to permit repeated excursions in altitude. The essential

James A. Cutts; Kerry T. Nock; Jack A. Jones; Guillermo Rodriguez; J. Balaram

1995-01-01

271

Planetary exploration by robotic aerovehicles  

Microsoft Academic Search

Planetary aerobots are a new type of telerobotic science platform that can fly and navigate in a dynamic 3D atmospheric environment, enabling the exploration of planetary atmospheres and surfaces. Aerobots use planetary balloon altitude control which employs reversible-fluid changes to permit repeated excursions in altitude. Venus, Mars and Titan will be explored with aerobots using helium or hydrogen as their

J. A. Cutts; K. T. Nock; J. A. Jones; G. Rodriguez; J. Balaram

1995-01-01

272

A new geochemical instrument for the precise measurement of isotopic ratios and trace species in planetary atmospheres  

NASA Astrophysics Data System (ADS)

The technique of GCMS analysis, which has been used with a great success on several past planetary missions, is not adapted for precise measurements of the isotopic composition of planetary atmospheres (noble gases, stable isotopes), and volatile outgassed products from solid sample pyrolysis. Static mass spectrometry, coupled with gas separation by cryo-separation, and chemical trapping, is commonly used in the laboratory to study volatiles extracted from terrestrial and meteoritic samples. This technique allows to reach a precision on isotopic ratios of the order of a few 0.1 ppm for a typical amount of gas of a few micromoles. We are presently studying an instrument based on the same principle for space exploration applications. The PALOMA instrument (PAyload for Local Observation of Mars Atmosphere) will be proposed in response to the AO for the instrumentation of the NASA Mars Smart Lander mission, planned to be launched in 2009. It might be part as well of the EXOMARS mission presently studied at ESA in the frame of the Aurora program. The miniaturization of major key elements, like the cryogenic device, the mass spectrometer, the line and its ensemble of valves, is presently led in our laboratories under CNES funding. The instrument consists of : (i) a gas purification and separation line, using techniques of cryogenic and chemical trapping, and possibly membrane permeation for molecular hydrogen analysis, (ii) a mass spectrometer working in static mode, without carrier gas (both time-of-flight and magnetic solutions are studied), (iii) a turbo-molecular pump that provides the required level of vacuum in the separation line and in the spectrometer. In the specific case of Mars, it is designed to work during typically 2 years (about 1000 measurement cycles), in order to perform accurate measurements of molecular, elemental and isotopic composition and of their diurnal/seasonal variations. The gas is sampled directly from the ambient atmosphere, without need for an external sample distribution system. The general characteristics of the instrument are as following . The mass is 6 kg, for a size of 30 x 30 x 20 cm. The required power, averaged over a complete measurement cycle, is 20 W (peak value : 30 W). The total energy required for one sequence is 100 Wh. This number must be considered as an upper limit, and corresponds to the most complex sequence (noble gas isotope analysis). Sequences used for stable isotopes measurement, and atmospheric molecular composition (trace gases of geological and/or astrobiological interest), are expected to be simpler, and less power-consuming. The anticipated volume of data produced by one observation sequence is estimated to be in the 3-6 kb range. The gas is sampled directly from the ambient atmosphere.

Chassefiere, E.; Jambon, A.; Berthelier, J.-J.; Sarda, Ph.; Agrinier, P.

2003-04-01

273

Origin of planetary atmospheres and their role in the evolution of life  

NASA Astrophysics Data System (ADS)

The successful synthesis of amino acids in a reducing gas mixture presumably resembling the primary Earth atmosphere, by the Miller-Urey experiment, had a long lasting influence on the general perception of such an early atmosphere. Based on atmospheric escape, such a reducing atmosphere, however, has a lifetime of only millions of years. According to present view the early atmosphere of Earth may have resulted from mantle degassing of volatiles (H2O, CO2, N2), followed by later accumulation of O2 as product of life (photosynthesis). For Mars, with similar degassing products, evolution of life could have been possible in its early history. Non-reducing atmospheres (with liquid water) although not conductive for local synthesis of prebiotic molecules, may provide a benign environment for the evolution of life via ubiquitous supply of "building blocks" from external sources.

Bauer, Siegfried J.

2002-11-01

274

Planetary g(t) for which resistive atmospheric falling is rising  

Microsoft Academic Search

A Darboux-transformed surface gravitational acceleration of the constant\\u000agravitational acceleration for a body endowed with an atmospheric layer is\\u000ashown to turn the atmospheric free fall with quadratic resistance in the\\u000aopposite motion, i.e., a free rising. Although the atmosphere of such a body\\u000amay look completely normal, it is the time dependence of its gravitational\\u000afield that produces this

Haret C. Rosu; F. Aceves de la Cruz

2001-01-01

275

Carbon-rich Molecular Chains in Protoplanetary and Planetary Atmospheres: Quantum Mechanisms and Electron Attachment Rates for Anion Formation  

NASA Astrophysics Data System (ADS)

The elementary mechanisms through which molecular polyynes could form stable negative ions after interacting with free electrons in planetary atmospheres (e.g., Titan's) are analyzed using quantum scattering calculations and quantum structure methods. The case of radical species and of nonpolar partners are analyzed via specific examples for both the C n H and HC n H series, with n values from 4 to 12. We show that attachment processes to polar radicals are dominating the anionic production and that the mediating role of dipolar scattering states is crucial to their formation. The corresponding attachment rates are presented as calculated upper limits to their likely values and are obtained down to the low temperatures of interest. The effects of the computed rates, when used in simple evolutionary models, are also investigated and presented in detail.

Carelli, F.; Satta, M.; Grassi, T.; Gianturco, F. A.

2013-09-01

276

Characterization of Complex Organic Compounds Formed in Simulated Planetary Atmospheres by the Action of High Energy Particles  

NASA Astrophysics Data System (ADS)

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase

Kobayashi, Kensei; Kaneko, Takeo; Saito, Takeshi

1999-01-01

277

Characterization of complex organic compounds formed in simulated planetary atmospheres by the action of high energy particles.  

PubMed

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase. PMID:11543332

Kobayashi, K; Kaneko, T; Saito, T

1999-01-01

278

Modeling and process design of III-nitride MOVPE at near-atmospheric pressure in close coupled showerhead and planetary reactors  

Microsoft Academic Search

The metalorganic vapor-phase epitaxy (MOVPE) growth of GaN from TMGa and NH3 at higher process pressures up to near-atmospheric pressure in commercial production scale multi-wafer reactors is investigated. The Planetary Reactor® and close coupled showerhead reactor are compared and their suitability for near-atmospheric pressure growth is demonstrated. Advanced model development and its validation by growth experiments are carried out with

M. Dauelsberg; C. Martin; H. Protzmann; A. R. Boyd; E. J. Thrush; J. Käppeler; M. Heuken; R. A. Talalaev; E. V. Yakovlev; A. V. Kondratyev

2007-01-01

279

Comparative Planetology and the Search for Habitable Extrasolar Planets  

NASA Astrophysics Data System (ADS)

In the last decade, comparative planetology has grown to encompass not just the planets in our own Solar System, but also the more than 300 planets that are now known to orbit other stars in our Galaxy. The vast majority of the planets discovered so far are gas or ice giants, but a growing fraction have masses less than 10 Earth masses, and so may be terrestrial. Over the next two decades, NASA and ESA are planning to build large space-borne telescopes that will enable statistical studies and the first direct detection and characterization of terrestrial planets beyond our Solar System. These missions will allow the study of planets formed under diverse initial conditions, and at stages of evolution that are billions of years younger or older than the Earth. Ultimately though, these missions will finally provide the technical capability to search for habitable environments and life on planets beyond our Solar System. The scientific foundation that will guide this search is built on comparative climate studies of the planets in our own Solar System. From the perspective of extrasolar planet studies, the evolution of the climates of Venus, Earth and Mars inform the definition and characteristics of planetary habitability. Climate and chemistry models, developed initially to be flexible enough for Venus, Earth and Mars studies, and validated against measurements and observations of these planets, are now being modified to model a diversity of plausible extrasolar planetary environments. Specifically, these models have been used to better understand the interaction between the parent star, and the global environment and biosphere of a terrestrial planet for planetary systems unlike our Solar System. Additionally, planetary radiative transfer models developed for Venus, Earth and Mars studies can be used to predict the spectroscopic appearance of distant planetary environments and to simulate a telescopic view of the Earth as an extrasolar planet. This presentation will discuss the relevance of Solar System based comparative climatology to extrasolar planet studies, and show examples of its application to a range of simulated extrasolar terrestrial planet environments.

Meadows, V. S.

2008-12-01

280

Habitable Planets In The Planetary System Of HD 69830  

Microsoft Academic Search

We present the results of a study of the dynamical evolution and habitability of HD 69830 planetary system. Being the first multiplanet extrasolar planetary system with three Neptune-sized objects, HD 69830 provides new grounds for testing the possibility of the existence of smaller objects, such as terrestrial planets, particularly in its habitable zone. We numerically integrated the orbits of the

Sarah Rugheimer; N. Haghighipour

2007-01-01

281

The Bistatic Radar-Occultation Method for the Study of Planetary Atmospheres  

Microsoft Academic Search

Theoretical studies have been made of the characteristics of radio waves dif- fracted at the limb and refracted in the atmosphere of a planet. Sample computations have been made of atmospheric perturbations to the communication links to and from a Mars flyby spacecraft having a trajectory that involves occultation of the spacecraft by the planet as seen from the earth.

G. Fjeldbo; V. R. Eshleman

1965-01-01

282

A three-dimensional simulation of transmitted light through planetary atmospheres using Monte-Carlo methods  

NASA Astrophysics Data System (ADS)

The available light in the atmosphere of Titan has been calculated using a Monte Carlo method. The ``recommended'' temperature profile derived by Lellouch /1/, the aerosol distribution from McKay /2/ and their properties from Khare /3/, and an atmospheric composition from the new photochemical model of Toublanc /4/ are used in the framework of plane parallel geometry to compute all processes that occur in the atmosphere. The solar flux at each level in the atmosphere in the wavelength range 10-1000 nm is estimated. This paper improves 2D models including multiple scattering by molecules and aerosols in a 3D model. Assuming spherical symmetry, the atmosphere is divided into spherical layers of equal optical depth tau = 0.01. The solar flux is represented by 10^5-10^6 photons cm-2. The absorption and diffusion by aerosols and gases is treated exactly.

Brillet, J.; Parisot, J. P.; Dobrijevic, M.; Leflochmoen, E.; Toublanc, D.

283

Extrasolar Planets in the Classroom  

ERIC Educational Resources Information Center

|The field of extrasolar planets is still, in comparison with other astrophysical topics, in its infancy. There have been about 300 or so extrasolar planets detected and their detection has been accomplished by various different techniques. Here we present a simple laboratory experiment to show how planets are detected using the transit technique.…

George, Samuel J.

2011-01-01

284

PHOTOMETRIC ORBITS OF EXTRASOLAR PLANETS  

SciTech Connect

We define and analyze the photometric orbit (PhO) of an extrasolar planet observed in reflected light. In our definition, the PhO is a Keplerian entity with six parameters: semimajor axis, eccentricity, mean anomaly at some particular time, argument of periastron, inclination angle, and effective radius, which is the square root of the geometric albedo times the planetary radius. Preliminarily, we assume a Lambertian phase function. We study in detail the case of short-period giant planets (SPGPs) and observational parameters relevant to the Kepler mission: 20 ppm photometry with normal errors, 6.5 hr cadence, and three-year duration. We define a relevant 'planetary population of interest' in terms of probability distributions of the PhO parameters. We perform Monte Carlo experiments to estimate the ability to detect planets and to recover PhO parameters from light curves. We calibrate the completeness of a periodogram search technique, and find structure caused by degeneracy. We recover full orbital solutions from synthetic Kepler data sets and estimate the median errors in recovered PhO parameters. We treat in depth a case of a Jupiter body-double. For the stated assumptions, we find that Kepler should obtain orbital solutions for many of the 100-760 SPGP that Jenkins and Doyle estimate Kepler will discover. Because most or all of these discoveries will be followed up by ground-based radial velocity observations, the estimates of inclination angle from the PhO may enable the calculation of true companion masses: Kepler photometry may break the 'msin i' degeneracy. PhO observations may be difficult. There is uncertainty about how low the albedos of SPGPs actually are, about their phase functions, and about a possible noise floor due to systematic errors from instrumental and stellar sources. Nevertheless, simple detection of SPGPs in reflected light should be robust in the regime of Kepler photometry, and estimates of all six orbital parameters may be feasible in at least a subset of cases.

Brown, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)], E-mail: rbrown@stsci.edu

2009-09-10

285

Modelling the impact of the solar UV flux on Ganymede's atmosphere for constraining planetary missions: application to aeronomic emissions  

NASA Astrophysics Data System (ADS)

In the framework of future space missions to Ganymede, a pre-study of this satellite is a necessary step to constrain instrument performances according to the mission objectives. This work aims at characterizing the impact of the solar UV flux on Ganymede's atmosphere and especially at deriving some key physical parameters that are measurable by an orbiter. Another objective is to test several models for reconstructing the solar flux in the Extreme-UV (EUV) in order to give recommendations for future space missions. We first compute the primary production of excited and ionized states due to photoabsorption, neglecting the secondary production that is due to photoelectron impacts as well as to precipitated suprathermal electrons. Computations are performed at the equator and close to the pole, in the same conditions as during the Galileo flyby. From the excitations, we then compute the radiative relaxation leading to the atmospheric emissions. We also propose a simple chemical model to retrieve the stationary electron density. There are two main results: (i) the modelled electron density and the one measured by Galileo are in good agreement. The main atmospheric visible emission is the atomic oxygen red line at 630 nm, both in equatorial and in polar conditions. This emission is measurable from space, especially for limb viewing conditions. (ii) The input EUV solar flux may be directly measured or reconstructed from only two passbands solar observing diodes with no degradation of the modelled response of the Ganymede's atmosphere. This result strongly supports the idea that future planetary mission should include a radiometer to measure the local solar EUV flux.

Cessateur, G.; Lilensten, J.; Barthelemy, M.; Dudok de Wit, T.; Wedlund, C. Simon; Gronoff, G.; Kretzschmar, M.

2012-04-01

286

A hybrid method for modeling polarized radiative transfer in a spherical-shell planetary atmosphere  

NASA Astrophysics Data System (ADS)

The Markov chain method is developed for polarized radiative transfer in a pseudo-spherical atmosphere with solar illumination. This solution is then used as an initial guess of the radiation field for a spherical atmosphere. By use of the short characteristic method, a convergent radiation field throughout the atmosphere is achieved after a few Picard iterations. We verified this hybrid method by comparing numerical results to those obtained by a backward Monte Carlo calculation. We carried out a demonstration calculation by simulating the Titan haze reflected intensity I and Stokes parameter Q, and degree of linear polarization at 934.8 nm wavelength. Comparison of the I and Q images to those measured by the Imaging Science Subsystem instrument on the Cassini spacecraft shows the hybrid method to be useful for radiative transfer analyses for (both optically and physically) thick spherical atmospheres.

Xu, Feng; West, Robert A.; Davis, Anthony B.

2013-03-01

287

Laboratory evaluation of microwave absorption properties under simulated conditions for planetary atmospheres  

Microsoft Academic Search

The microwave absorbing properties of gaseous sulfuric acid (H2SO4) under Venus atmospheric conditions are investigated. The results are applied to measurements from Mariner 5, Mariner 10, and Pioneer\\/Venus Radio Occultation experiments, to determine abundancies of gaseous sulfuric acid in the Venus atmosphere. The microwave properties of the vapors accompanying liquid H2SO4 are studied to estimate the vapor pressure in an

P. G. Steffes

1984-01-01

288

Theoretical investigation of the possibility of the radio spectroscopy of planetary atmospheres using interplanetary probes  

Microsoft Academic Search

Consideration is given to the possibility of using interplanetary platforms for the remote sensing of trace components (N2O, CO and NH3) in the upper atmosphere of Venus and NH3 and H2O vapor in the atmospheres of Jupiter and Saturn. The limits of determining the relative concentrations of these gases using microwave resonance absorption spectroscopy are examined. The effective conditions under

A. P. Naumov

1977-01-01

289

STEM Colorado: Simplified Planetary Transits  

NSDL National Science Digital Library

This applet demonstrates how astronomers measure the properties of extra-solar planets by detecting planetary transits and eclipses. The applet shows a planet in orbit around a star. A graph plots the total brightness of the star as the planet orbits around it. The user can control the star's radius, the star's temperature, the planet's radius, the orbital radius and the albedo. This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Mccray, Richard; Koelemay, Andrew

2008-10-22

290

Mission Requirements: How to Search for Extrasolar Planets  

Microsoft Academic Search

In this chapter we will discuss the motivation, scientific requirements and technical implementation of space-based search for extrasolar planets. We discuss current and planned future missions, with a focus on designs that will be able to collect photons and therefore spectral information of the atmospheres of planets. The interferometric nulling technique as well as simulations of the observations is discussed

Malcolm Fridlund; Lisa Kaltenegger

2007-01-01

291

Possibilities for the Detection of Microbial Life on Extrasolar Planets  

Microsoft Academic Search

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

Roger F. Knacke

2003-01-01

292

The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 super-Earths (4.2, 6.9, and 9.2 M?)  

Microsoft Academic Search

We report the detection of a planetary system with three Super-Earths orbiting HD 40307. HD 40307 is a K2 V metal-deficient star at a distance of only 13 parsec, which is part of the HARPS GTO high-precision planet-search programme. The three planets on circular orbits have very low minimum masses of 4.2, 6.9, and 9.2 Earth masses and periods of

M. Mayor; S. Udry; C. Lovis; F. Pepe; D. Queloz; W. Benz; J.-L. Bertaux; F. Bouchy; C. Mordasini; D. Segransan

2009-01-01

293

Photometric Light Curves and Polarization of Close-in Extrasolar Giant Planets  

Microsoft Academic Search

The close-in extrasolar giant planets (CEGPs), <~0.05 AU from their parent stars, may have a large component of optically reflected light. We present theoretical optical photometric light curves and polarization curves for the CEGP systems from reflected planetary light. Different particle sizes of three condensates are considered. In the most reflective case, the variability is ~100 mumag, which will be

S. Seager; B. A. Whitney; D. D. Sasselov

2000-01-01

294

Survey for Transiting Extrasolar Planets in Stellar Systems. IV. Variables in the Field of NGC 1245  

Microsoft Academic Search

The Survey for Transiting Extrasolar Planets in Stellar Systems (STEPSS) project is a search for planetary transits in open clusters. In this paper we analyze the STEPSS observations of the open cluster NGC 1245 to determine the variable-star content of the cluster. Out of 6787 stars observed with V<22, of which ~870 are cluster members, we find 14 stars with

Joshua Pepper; Christopher J. Burke

2006-01-01

295

Direct imaging of extra-solar planets  

SciTech Connect

Direct imaging of extra-solar planets may be possible with the new generation of large ground-based telescopes equipped with state- of- the-art adaptive optics (AO) systems to compensate for the blurring effect of the Earth`s atmosphere. The first of these systems is scheduled to begin operation in 1998 on the 10 in Keck II telescope. In this paper, general formulas for high-contrast imaging with AO systems are presented and used to calculate the sensitivity of the Keck AO system. The results of these calculations show that the Keck AO system should achieve the sensitivity necessary to detect giant planets around several nearby bright stars.

Olivier, S.S.; Max, V.E.; Brase, J.M.; Caffano, C.J.; Gavel, D.T.; Macintosh, B.A.

1997-03-01

296

Orbit design for future SpaceChip swarm missions in a planetary atmosphere  

NASA Astrophysics Data System (ADS)

The effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag.

Colombo, Camilla; McInnes, Colin

2012-06-01

297

THIS -- next-generation mid-infrared remote sensing of planetary atmospheres using a tuneable heterodyne infrared spectrometer  

NASA Astrophysics Data System (ADS)

The Cologne spectrometer THIS (Tuneable Heterodyne Infrared Spectrometer) opens the mid-infrared wavelength region from 8 to 17 microns to ultra-high-resolution spectroscopy. The main scientific goal of THIS is to analyze highly resolved lineshape data of molecules (e.g. O3, NH3, CH4, N2O, HxCy etc.) to deduce physical parameters like wind velocities or height profiles of gases in either the Earth's or other planetary atmospheres. Also astronomical observations of non-solar-system IR-sources like IRC+10216 as well as the measurement of pure rotational transitions of H2 in the interstellar-medium from ground based telescopes are planned in the near future. THIS is a proposed second-generation instrument for the stratospheric observatory SOFIA. With a system noise temperature of less than three times the quantum limit THIS is the first widely tuneable and transportable infrared heterodyne receiver having a sensitivity equivalent to CO2-laser based heterodyne systems. A quantum-cascade-laser is used as local oscillator. Its radiation is superimposed to that from the signal by use of a Fabry-Perot ring-resonator to provide optimum efficiency. The frequency mixing is done by a Mercury-Cadmium-Telluride photomixer and spectral analysis with a resolution of up to 3x107 is performed by means of an Acousto-Optical spectrometer. We report on THIS' successful first observing run performed at the west auxiliary telescope at McMath-Pierce solar observatory on Kitt Peak/Arizona in 11/2002. Very weak non-LTE CO2 emission from the atmosphere of Venus have been observed as well as trace gases in Earth's atmosphere and molecular features in sunspots.

Sonnabend, G.; Wirtz, D.; Vetterle, V.; Schieder, R.

2003-12-01

298

Evaporation of ice in planetary atmospheres - Ice-covered rivers on Mars  

Microsoft Academic Search

The existence of ice covered rivers on Mars is considered. It is noted that the evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. It is determined that even with a mean Martian insolation rate above the ice of approximately

D. Wallace; C. Sagan

1979-01-01

299

Low-temperature Kinetic Studies of OH Radical Reactions Relevant to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

In the solar system, the temperature (T) of the atmosphere of giant planets or their satellites is only several tens of Kelvin (K). The temperature of the tropopause of Titan (satellite of Saturn) and the surface of Mars is 70 K and 210 K, respectively. In the Earth's atmosphere, T decreases from 298 K (surface) to 210 K close to the T-inversion region (tropopause). The principal oxidants in the Earth's lower atmosphere are ozone, the hydroxyl (OH) radical and hydrogen peroxide. A number of critical atmospheric chemical problems depend on the Earth's oxidising capacity, which is essentially the global burden of these oxidants. In the interstellar clouds and circumstellar envelopes, OH radicals have also been detected. As the chemistry of atmospheres is highly influenced by temperature, the knowledge of the T-dependence of the rate coefficients for OH-reactions (k) is the key to understanding the underlying molecular mechanisms. In general, these reactions take place on a short temporal scale. Therefore, a detection technique with high temporal resolution is required. Measurements of k at low temperatures can be achieved by maintaining a thermalised environment using either cryogenic cooling (T>200 K) or supersonic gas expansion with a Laval nozzle (several tens of K). The pulsed laser photolysis technique coupled with laser induced fluorescence detection has been widely used in our laboratory to determine the rate coefficients of OH-reactions with different volatile organic compounds, such as alcohols (1), saturated and unsaturated aliphatic aldehydes (2), linear ketones (3), as a function of temperature (260 350 K). An experimental system based on the CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique is currently under construction. This technique will allow the performance of kinetic studies of OH-reactions of astrophysical interest at temperatures lower than 200 K.

Townsend, T. M.; Antiñolo, M.; Ballesteros, B.; Jimenez, E.; Canosa, A.

2011-05-01

300

STEM Colorado: Planetary Transits  

NSDL National Science Digital Library

This applet demonstrates how astronomers measure the properties of extra-solar planets by detecting planetary transits and eclipses. The applet shows a planet in orbit around a star. A graph plots the total brightness of the star as the planet orbits around it. The user can control the star's radius, the star's temperature, the planet's radius, the orbital radius and the albedo. The user can also see how the spectrum of the illuminated side of the planet, due to both the reflected starlight and the emitted planetary radiation, dependes on wavelength, albedo, and the parameters of the system. This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Mccray, Richard; Koelemay, Andrew

2008-08-30

301

The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 Super-Earths (4.2, 6.9, & 9.2 Earth masses)  

Microsoft Academic Search

This paper reports on the detection of a planetary system with three\\u000aSuper-Earths orbiting HD40307. HD40307 is a K2V metal-deficient star at a\\u000adistance of only 13 parsec, part of the HARPS GTO high-precision planet-search\\u000aprogramme. The three planets on circular orbits have very low minimum masses of\\u000arespectively 4.2, 6.9 and 9.2 Earth masses and periods of 4.3, 9.6

M. Mayor; S. Udry; C. Lovis; F. Pepe; D. Queloz; W. Benz; J.-L. Bertaux; F. Bouchy; C. Mordasini; D. Segransan

2008-01-01

302

Planetary Radiation Balance as a Function of Atmospheric Dust: Climatological Consequences  

Microsoft Academic Search

An analysis of several atmospheric dust-loading events at Phoenix, Arizona, under background cloudless sky conditions, allowed determination of dust-induced changes in both the net solar and net thermal radiation received at the earth's surface. The resultant climatological forcing function for surface temperature change was plotted against the ratio of diffuse to normal-incidence solar radiation. It was found that initial increases

Sherwood B. Idso; Anthony J. Brazel

1977-01-01

303

Electronic excitation and isentropic coefficients of high temperature planetary atmosphere plasmas  

SciTech Connect

In this paper, we have discussed the effects of electronically excited states of atomic species in affecting the isentropic coefficients of plasmas, focusing on mixtures representing the atmospheres of Jupiter, Mars, and Earth. General behaviors have been rationalized on the basis of simplified approaches. The contribution of the electronically excited states has been evidenced by comparing results obtained considering only the ground state and those obtained using either Fermi or Griem cutoff criteria.

Colonna, Gianpiero [CNR IMIP Bari Via Amendola 122/d, 70126 Bari (Italy); D'Angola, Antonio [Dipartimento di Ingegneria e Fisica dell'Ambiente, Universita della Basilicata, via dell'Ateneo Lucano, 10-85100 Potenza (Italy); Capitelli, Mario [CNR IMIP Bari Via Amendola 122/d, 70126 Bari (Italy); Department of Chemistry, University of Bari, via Orabona, 4, 70126, Bari (Italy)

2012-07-15

304

New Experimental Data and Analysis of the Ammonia-Water System for Studies of Planetary Atmospheres  

Microsoft Academic Search

Studies of the atmospheres of the giant planets require an accurate understanding of the vapor-liquid equilibrium for the ammonia-water system. New vapor-liquid equilibrium data for this system have been taken in the Laboratory for Chemical Thermodynamics at Cornell University using a custom-built apparatus. An extensive evaluation of the available literature data has been conducted to assess their quality and thermodynamic

N. C. Parikh; J. A. Zollweg

1996-01-01

305

Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations  

PubMed Central

Abstract The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ?100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ?10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ?7% and brightness temperature errors of less than 1?K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology—Extrasolar terrestrial planets—Habitability—Planetary science—Radiative transfer. Astrobiology 11, 393–408.

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

2011-01-01

306

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

PubMed

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ?100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ?10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ?7% and brightness temperature errors of less than 1?K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology-Extrasolar terrestrial planets-Habitability-Planetary science-Radiative transfer. Astrobiology 11, 393-408. PMID:21631250

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

2011-06-01

307

Planetary Interior Evolution and Life  

NASA Astrophysics Data System (ADS)

The habitability of planets has received increasing interest, in particular in view of the increasing number of detected extrasolar planets. Planetary habitability (for life as we know it) is thought to require water on (or near) the surface, a magnetic field to protect life against radiation, and transport mechanisms for nutrients. A chemoautotrophic biosphere would require volcanic activity and associated large thermal gradients. Volcanic activity is thought to have been instrumental for the formation of (initially chemoautotrophic) life on Earth. A magnetic field also protects an existing atmosphere against erosion by the solar wind and thus helps to stabilize the presence of surface water. Magnetic fields are generated in the cores of the terrestrial planets and thus habitability is linked to the evolution of the interior through magnetic field generation and volcanic activity. Moreover, the interior is a source and sink for water and may interact with the surface and atmosphere reservoirs through volcanism and recycling. The most efficient known mechanism for recycling is plate tectonics. Plate tectonics is known to operate only on the Earth, although Mars and Venus may have had phases of plate tectonics. Plate tectonics supports the generation of magnetic fields by effectively cooling the deep interior and rejuvenates near-surface nutrients. On the Earth, surface water is stabilized by complex interactions between the atmosphere, the biosphere, the oceans, the crust, and the deep interior in the carbon-silicate cycle. As plate tectonics is believed to require water in the mantle to operate, plate tectonics is another element linking the biosphere to the evolution of the planet's interior. Single-plate tectonics associated with stagnant lid convection would allow for transfer of water from the interior by volcanism but lacks a simple recycling mechanism. The question of whether or not extrasolar earthlike planets more massive than the Earth are likely to have plate tectonics or single-plate tectonics is hotly debated. We argue that the large interior pressure and its effect on the rheology of their mantles may frustrate plate tectonics and magnetic field generation altogether. We even argue that surface volcanic activity may become difficult with increasing mass of a rocky planet. On Earth, mantle melt is buoyant at depths smaller than a few 100km. Below this critical depth melt will be negatively buoyant because of its compressibility. The critical depth will decrease with increasing mass of the planet and may become shallower than the depth to the base of the stagnant lid on massive planets. We find the ratio between the stagnant lid thickness and the critical depth to increase approximately linearly with the planet radius. The great diversity of extrasolar planets may suggest a diversity of life forms and associated habitability parameters, however, and extrapolations from the Earth may be overly naive.

Spohn, T.; Breuer, D.; Noack, L.; Höning, D.

2011-12-01

308

Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres.  

PubMed

Gas chromatography (GC) is a powerful technique for analyzing gaseous mixtures. Applied to the earth's atmosphere, GC can be used to determine the permanent gases--such as carbon dioxide, nitrogen, and oxygen--and to analyze organic pollutants in air. The U.S. National Aeronautics and Space Administration (NASA) has used GC in spacecraft missions to Mars (the Viking Biology Gas Exchange Experiment [GEX] and the Viking Gas Chromatograph-Mass Spectrometer [GC-MS]) and to Venus (the Pioneer Venus Gas Chromatograph [PVGC] on board the Pioneer Venus sounder probe) for determining the atmospheric constituents of these two planets. Even though conventional GC was very useful in the Viking and Pioneer missions, spacecraft constraints and limitations intrinsic to the technique prevented the collection of more samples. With the Venus probe, for instance, each measurement took a relatively long time to complete (10 min), and successive samples could not be introduced until the previous samples had left the column. Therefore, while the probe descended through the Venusian atmosphere, only three samples were acquired at widely separated altitudes. With the Viking mission, the sampling rate was not a serious problem because samples were acquired over a period of one year. However, the detection limit was a major disadvantage. The GC-MS could not detect simple hydrocarbons and simple alcohols below 0.1 ppm, and the GEX could not detect them below 1 ppm. For more complex molecules, the detection limits were at the parts-per-billion level for both instruments. Finally, in both the Viking and Pioneer missions, the relatively slow rate of data acquisition limited the number of analyses, and consequently, the amount of information returned. Similar constraints are expected in future NASA missions. For instance, gas chromatographic instrumentation is being developed to collect and analyze organic gases and aerosols in the atmosphere of Titan (one of Saturn's satellites). The Titan-Cassini entry probe, which is being jointly planned by NASA and the European Space Agency (ESA), might be launched as early as 1994. As in the Pioneer mission, limited time--perhaps only 3-4 h--will be available for the completion of all analyses while the probe descends through the atmosphere. A conventional GC or GC-MS system would be able to analyze no more than two aerosol and two gas samples during the probe's descent. Conventional GC also is limited by the sensitivity of the detector and by the sample volume. For the Titan mission, the sensitivity problems will be worse because the atmospheric pressure at the time of instrument deployment is expected to be < 3 torr. Consequently, the sample volume might not be large enough to satisfy the detector sensitivity requirements. Because of such limitations, alternative GC analysis techniques have been investigated for future NASA missions. Multiplex gas chromatography has been investigated as a possible candidate for chemical analysis within a spacecraft or other restricted environment, and chemical modulators have been developed and used when needed with this technique to reduce the size and weight of the instrumentation. Also, several new multiplex techniques have been developed for use in specific applications. PMID:11539794

Valentin, J R

1989-03-01

309

Sensitivity of MM5-simulated planetary boundary layer height to soil dataset: comparison of soil and atmospheric effects  

NASA Astrophysics Data System (ADS)

The effects of two soil datasets on planetary boundary layer (PBL) height are analyzed, using model simulations. Simulations are performed with the MM5 weather prediction system over the Carpathian Basin, with 6 km horizontal resolution, investigating three summer days, two autumn, and one winter day of similar synoptic conditions. Two soil datasets include that of the United States Department of Agriculture, which is globally used, and a regional Hungarian called Hungarian unsaturated soil database. It is shown that some hydraulic parameter values between the two datasets can differ up to 5-50%. These differences resulted in 10% deviations in the space-time-averaged PBL height (averaged over Hungary and over 12 h in the daytime period). Over smaller areas, these relative deviations could reach 25%. Daytime course changes in the PBL height for reference run conditions were significant ( p < 0.01) in ?70% of the grid points covering Hungary. Ensemble runs using different atmospheric parameterizations and soil moisture initialization setups are also performed to analyze the sensitivity under changed conditions. In these cases, the sensitivity test showed that irrespective of the radiation and PBL scheme, the effect of different soil datasets on PBL height is roughly the same. PBL height is also sensitive to field capacity (?f) and wilting point (?w) changes. ?f changes seem to be more important for loamy sand, while ?w changes for the clay soil textural class.

Breuer, Hajnalka; Ács, Ferenc; Laza, Borbála; Horváth, Ákos; Matyasovszky, István; Rajkai, Kálmán

2012-08-01

310

Planetary wave coupling processes in the middle atmosphere (30 90 km): A study involving MetO and MFR data  

NASA Astrophysics Data System (ADS)

The MetO assimilated data and mesospheric winds provided by five medium frequency radars (MFR) from the Canada US Japan Opportunity (CUJO) network have been used to study coupling processes due to planetary waves (PWs) in the middle atmosphere. It is shown that there is strong vertical coupling between the stratosphere and mesosphere especially during winter months. However, not all observed disturbances in mesospheric winds can be explained by the simple propagation of PWs from below. In addition to the vertical coupling there is also weaker horizontal “inter-hemispheric” coupling during equinoxes. The data used are from December 2000 to December 2002. The time interval was chosen to include austral winters and springs of 2 years: the dynamically unusual year 2002, during which a major stratospheric warming involving a split vortex and wind reversals occurred in the Southern Hemisphere, and a more typical year 2001. The character of PW activity during these 2 years is compared. In contrast to the usually weak PW activity dominated by eastward motions, both strong eastward and westward propagating waves existed during austral winter of 2002. Wavelet spectra of MetO winds show strong peaks near 14 days that match similar signals observed in mesospheric winds at Antarctic stations [Dowdy et al., 2004. The large-scale dynamics of the mesosphere lower thermosphere during the SH stratospheric warming of 2002. Geophysical Research Letters 31, L14102. doi:10.1029/2004GL020282] during the stratospheric warming. It is suggested that this oscillation was generated at low atmospheric heights and propagated upward. The longer duration of the stratospheric mesospheric winter vortex (7 months) compared to that of the summer jet in the Northern Hemisphere provide equinoctial months when eastward winds dominate globally. Results suggest that during equinoxes, with favourable conditions, the PWs with ˜10-, 16- and 25-day periods can penetrate to the opposite hemisphere.

Chshyolkova, T.; Manson, A. H.; Meek, C. E.; Avery, S. K.; Thorsen, D.; MacDougall, J. W.; Hocking, W.; Murayama, Y.; Igarashi, K.

2006-02-01

311

Planetcam: A Visible And Near Infrared Lucky-imaging Camera To Study Planetary Atmospheres And Solar System Objects  

NASA Astrophysics Data System (ADS)

PlanetCam is a two-channel fast-acquisition and low-noise camera designed for a multispectral study of the atmospheres of the planets (Venus, Mars, Jupiter, Saturn, Uranus and Neptune) and the satellite Titan at high temporal and spatial resolutions simultaneously invisible (0.4-1 ?m) and NIR (1-2.5 ?m) channels. This is accomplished by means of a dichroic beam splitter that separates both beams directing them into two different detectors. Each detector has filter wheels corresponding to the characteristic absorption bands of each planetary atmosphere. Images are acquired and processed using the “lucky imaging” technique in which several thousand images of the same object are obtained in a short time interval, coregistered and ordered in terms of image quality to reconstruct a high-resolution ideally diffraction limited image of the object. Those images will be also calibrated in terms of intensity and absolute reflectivity. The camera will be tested at the 50.2 cm telescope of the Aula EspaZio Gela (Bilbao) and then commissioned at the 1.05 m at Pic-duMidi Observatory (Franca) and at the 1.23 m telescope at Calar Alto Observatory in Spain. Among the initially planned research targets are: (1) The vertical structure of the clouds and hazes in the planets and their scales of variability; (2) The meteorology, dynamics and global winds and their scales of variability in the planets. PlanetCam is also expected to perform studies of other Solar System and astrophysical objects. Acknowledgments: This work was supported by the Spanish MICIIN project AYA2009-10701 with FEDER funds, by Grupos Gobierno Vasco IT-464-07 and by Universidad País Vasco UPV/EHU through program UFI11/55.

Sanchez-Lavega, Agustin; Rojas, J.; Hueso, R.; Perez-Hoyos, S.; de Bilbao, L.; Murga, G.; Ariño, J.; Mendikoa, I.

2012-10-01

312

Airships for Planetary Exploration.  

National Technical Information Service (NTIS)

The feasibility of utilizing an airship for planetary atmospheric exploration was assessed. The environmental conditions of the planets and moons within our solar system were evaluated to determine their applicability for airship flight. A station-keeping...

A. Colozza

2004-01-01

313

C/O Ratios in Exoplanetary Atmospheres  

NASA Astrophysics Data System (ADS)

Recent observations are allowing unprecedented constraints on the carbon-to-oxygen (C/O) ratios of giant exoplanetary atmospheres. Elemental abundance ratios, such as the C/O ratio, of planetary atmospheres provide important constraints on planetary interior compositions and formation conditions, and on the chemical and dynamical processes in the atmospheres. In addition, for super-Earths, the potential availability of water and oxygen, and hence the notion of `habitability', is contingent on the C/O ratio. Typically, an oxygen-rich composition, motivated by the solar nebula C/O of 0.5, is assumed in models of exoplanetary formation, interiors, and atmospheres. However, recent observations of exoplanetary atmospheres are suggesting the possibility of C/O ratios of 1.0 or higher, motivating the new class of Carbon-rich Planets (CRPs). In this talk, we will present observational constraints on atmospheric C/O ratios for an ensemble of transiting exoplanets and discuss their implications on the various aspects of exoplanetary characterization described above. Motivated by these results, we propose a two-dimensional classification scheme for irradiated giant exoplanets in which the incident irradiation and the atmospheric C/O ratio are the two dimensions. We demonstrate that some of the extreme anomalies reported in the literature for hot Jupiter atmospheres can be explained based on this 2-D scheme. An overview of new theoretical avenues and observational efforts underway for chemical characterization of extrasolar planets, from hot Jupiters to super-Earths, will be presented.

Madhusudhan, N.

2012-04-01

314

The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 super-Earths (4.2, 6.9, and 9.2 M?)  

NASA Astrophysics Data System (ADS)

We report the detection of a planetary system with three Super-Earths orbiting HD 40307. HD 40307 is a K2 V metal-deficient star at a distance of only 13 parsec, which is part of the HARPS GTO high-precision planet-search programme. The three planets on circular orbits have very low minimum masses of 4.2, 6.9, and 9.2 Earth masses and periods of 4.3, 9.6, and 20.5 days, respectively. The planet with the shortest period is the lowest mass planet detected to-date orbiting a main sequence star. The detection of the correspondingly low amplitudes of the induced radial-velocity variations is secured completely by the 135 high-quality HARPS observations illustrated by the radial-velocity residuals around the 3-Keplerian solution of only 0.85 ms-1. Activity and bisector indicators exclude any significant perturbations of stellar intrinsic origin, which supports a planetary interpretation. In contrast to most planet-host stars, HD 40307 has a significantly sub-solar metallicity ([Fe/H] = -0.31), which suggests that very light planets might have a different dependence on host star metallicity than gas giant planets. In addition to the 3 planets close to the central star, a small drift in the radial-velocity residuals implies the presence of another companion in the system, the nature of which is still unknown. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory under the GTO programme ID 072.C-0488. The table with the individual radial velocities is available in electronic form at the CDS anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/639

Mayor, M.; Udry, S.; Lovis, C.; Pepe, F.; Queloz, D.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Mordasini, C.; Segransan, D.

2009-01-01

315

Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data  

NASA Astrophysics Data System (ADS)

The activities of mid-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W) and one Chinese station (Wuhan, 30.5° N, 114.4° E). Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same quasi 16-day wave at the three American stations (Miramar Nas, Santa Teresa and Fort Worth), which propagates steadily along the latitude. The quasi 16-day wave in the stratosphere is also a standing wave with vertical wavelength larger than 10 km in the zonal wind component, and it is westward with the zonal number 1-2. However, the quasi 16-day wave in the stratosphere may not come from the troposphere because of the different concurrent times, propagation directions and velocities. By using the global dataset of NCEP/NCAR reanalysis data, the zonal propagation parameters of 16-day waves in the troposphere and stratosphere are calculated. It is found that the tropospheric 16-day wave propagates eastward with the zonal number 6, while the stratospheric 16-day wave propagates westward with the zonal number 2, which matches well with the results of radiosonde data.

Wang, R.; Zhang, S. D.; Yang, H. G.; Huang, K. M.

2012-10-01

316

Simulation of a miniature, low-power time-of-flight mass spectrometer for in situ analysis of planetary atmospheres  

Microsoft Academic Search

We are implementing nano- and micro-technologies to develop a miniaturized electron impact ionization mass spectrometer for planetary science. Microfabrication technology is used to fabricate the ion and electron optics, and a carbon nanotube (CNT) cathode is used to generate the ionizing electron beam. Future NASA planetary science missions demand miniaturized, low power mass spectrometers that exhibit high resolution and sensitivity

Todd T. King; Patrick A. Roman; Federico A. Herrero; Hollis H. Jones; Duncan M. Kahle; Bernard Lynch; George Suárez; William B. Brinckerhoff; Paul R. Mahaffy

2008-01-01

317

Once in a Pale Blue Dot: Simulated Observations of an Extrasolar Earth-Moon System  

NASA Astrophysics Data System (ADS)

The inability of the Moon to efficiently circulate energy from its day side to its night side leads to large surface temperatures on its illuminated hemisphere. As a result, the Moon can contribute a significant amount of flux to spatially unresolved thermal infrared (IR) observations of the Earth-Moon system, especially at wavelengths where Earth's atmosphere is absorbing. We have paired the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model with a model of the phase dependent IR spectrum of the Moon to investigate the effects of an unresolved companion on observations of Earthlike extrasolar planets. For an extrasolar Earth-Moon system observed at full phase at IR wavelengths, the Moon consistently comprises about 20% of the total signal, approaches 30% of the signal in the 9.6 ?m ozone band and the 15 ?m carbon dioxide band, makes up as much as 80% of the total signal in the 6.3 ?m water band, and more than 90% of the signal in the 4.3 ?m carbon dioxide band. These excesses translate to inferred brightness temperatures for Earth that are too large by about 20-40 K, and demonstrate that the presence of an undetected satellite can have a significant impact on the spectroscopic characterization of terrestrial exoplanets. The thermal flux contribution from an airless companion depends strongly on the star-planet-observer angle (i.e., the phase angle), allowing moons to mimic or mask seasonal variations in the host planet's IR spectrum. We show that, by differencing IR observations of an Earth with a companion taken at both gibbous phase and at crescent phase, Moon-sized satellites may be detectable by future exoplanet characterization missions for a wide range of system inclinations.

Robinson, T. D.; Meadows, V. S.

2011-12-01

318

A map of the day-night contrast of the extrasolar planet HD 189733b.  

PubMed

'Hot Jupiter' extrasolar planets are expected to be tidally locked because they are close (<0.05 astronomical units, where 1 au is the average Sun-Earth distance) to their parent stars, resulting in permanent daysides and nightsides. By observing systems where the planet and star periodically eclipse each other, several groups have been able to estimate the temperatures of the daysides of these planets. A key question is whether the atmosphere is able to transport the energy incident upon the dayside to the nightside, which will determine the temperature at different points on the planet's surface. Here we report observations of HD 189733, the closest of these eclipsing planetary systems, over half an orbital period, from which we can construct a 'map' of the distribution of temperatures. We detected the increase in brightness as the dayside of the planet rotated into view. We estimate a minimum brightness temperature of 973 +/- 33 K and a maximum brightness temperature of 1,212 +/- 11 K at a wavelength of 8 mum, indicating that energy from the irradiated dayside is efficiently redistributed throughout the atmosphere, in contrast to a recent claim for another hot Jupiter. Our data indicate that the peak hemisphere-integrated brightness occurs 16 +/- 6 degrees before opposition, corresponding to a hotspot shifted east of the substellar point. The secondary eclipse (when the planet moves behind the star) occurs 120 +/- 24 s later than predicted, which may indicate a slightly eccentric orbit. PMID:17495920

Knutson, Heather A; Charbonneau, David; Allen, Lori E; Fortney, Jonathan J; Agol, Eric; Cowan, Nicolas B; Showman, Adam P; Cooper, Curtis S; Megeath, S Thomas

2007-05-10

319

Extrasolar planet detection at infrared wavelengths from the Earth  

NASA Astrophysics Data System (ADS)

We show that extrasolar planets in orbit around nearby stars can be detected from the ground or from a stratospheric telescope in the infrared region of the spectrum. We present calculations on the detectability of extrasolar planets, using Erich Grossman's Atmospheric Transmission (AT) code to compute atmospheric transmission at bands centered at 11 ?m, 20 ?m, 27 ?m, 200 ?m, 225 ?m, 350 ?m, 450 ?m, 640 ?m, 750 ?m, and 870 ?m. Detection limits for terrestrial and Jovian planets orbiting Sun-like stars are presented by assuming Planck emission. We consider several potential sites including the south pole, a 5000-m elevation site in the Atacama Desert in Chile, Mauna Kea in Hawaii, and an aerostat-borne telescope flown near the poles. We consider extrasolar planet detection with a 10-m class mid-IR telescope and a dilute aperture stratospheric telescope consisting of 4-m mirrors optimized for this task. Detection in the submillimeter, even with a 104 m2 collecting area array is extremely difficult because of low atmospheric transparency, and the decrease (~?-2) in planet emission with increasing wavelength in the Rayleigh-Jeans limit. We discuss critical technologies needed for this undertaking, including tethered aerostats and balloon-borne telescopes, the development of mid-IR nulling interferometry, actively cooled optics operating in the atmosphere, and optimized filters that are matched to the atmospheric transmission windows.

Yu, Ka Chun; Bally, John

320

Negative Ions Induced Processes in Proto-Planetary Atmospheres and ISM  

NASA Astrophysics Data System (ADS)

In a carbon-rich red giant or in a carbon-rich protoplanetary nebula (PPN) atmosphere, like CRL 618, the major carbon-bearing chemical species that is initially formed is acetylene.Specific chemical reactions, depending on both density and temperature conditions, could then lead to the formation of polycyclic aromatic hydrocarbons (PAHs), large aromatic planar molecules.Some of the chemical networks assume PAHs synthesis in the molecular envelops of C-rich stars, with acetylene being the major carbon source and requiring at the same time particularly dense and slow stellar winds.More in detail, the ionic chemical model involves hydrocarbon ion-neutral acetylene reactions and both hydrogenation and/or electron recombination processes, thereby implicitly accounting for the presence of low-energy electrons that we argue here to play an important role.Having found that one of the suggested intermediate species, the neutral ortho-benzyne molecule, is indeed capable of forming by electron attachment at low energy (1 eV) at least one metastable anionic state, we have consequently analysed the possibility that condensation reactions, leading to PAHs formation in PPN atmospheres, could occur with negative aromatic species such as stabilized anionic ortho-benzyne (o-C6H4-).To account for this task, through accurate quantum dynamical modelling of the initial steps, we find that, once the primary electron attachment on the neutral ortho-benzyne has taken place producing the corresponding metastable negative ion, the evolution of this resonant anionic intermediate in terms of its energy locations and lifetimes suggests the possibility of a radiationless stabilization by a very rapid intramolecular vibrational redistribution (IVR) of the excess energy carried by the attached electron.Currently,always in the low-energy range (0-5 eV), we are studying the formation mechanisms and evolution of metastable anions of both coronene, given its role in the UV extinction processes due to its charge state, and linear polyynes having permanent dipole.

Carelli, F.; Sebastianelli, F.; Gianturco, F. A.

2011-05-01

321

Transit spectroscopy of the extrasolar planet HD 209458B: The search for water  

NASA Astrophysics Data System (ADS)

This dissertation describes an attempt to detect water in the atmosphere of the extrasolar planet HD 209458b using transit spectroscopy. It first discusses the importance of water detection and reviews the state of knowledge about extrasolar planets. This review discusses the main statistical trends and describes the detection methods employed to this date. The importance of the transiting planets and the many measurements of the known ones are also discussed. A radiative transfer model designed and built specifically for this project predicts, given a planetary temperature/pressure/composition profile, the dependence in wavelength of the stellar spectrum modulation due to a transiting planet. A total of 352 spectra around 1.8 [mu]m were obtained on four nights (three in transit) of observations on August 3--4, September 26, and October 3 of 2002 using ISAAC at the Very Large Telescope. Correlating the modeled modulation with the infrared spectra yields a nondetection of water in the atmosphere of HD 209458b. It is found that the nondetection is due to an unfortunate choice of observing parameters and conditions that made it impossible to reach the required sensitivity. Nonetheless, the results are scaled with synthetic spectra to place strong limits on the planetary system configurations for which the observing parameters and telluric conditions would have yielded a successful detection. None of the 10 other known transiting planets would be detectable with the choice of parameters and conditions for this observation. A quantitative model of an improved observing strategy for future observations of this kind is developed. The improvements include: airmass and timing constraints, the simultaneous observation of a calibrator star, and a new method to find the optimal wavelength range. The data-reduction process includes several original techniques that were developed during this work, such as a method to remove fringes from flat fields and several methods to correct for telluric absorption, among others. Some of the code developed for this project is available under the GNU General Public License at the DSpace Internet archive from Cornell University.

Rojo, Patricio Michel

322

Planet Finder: Discovering Extra-solar Planets Exercise  

NSDL National Science Digital Library

This applet demonstrates the technique for detecting extrasolar planets through measurements of the Doppler shift of spectral lines of the star due to the star's reflex motion. The applet generates randomized data of the Doppler velocity representing observations of a planetary system. The object of the game is to adjust the parameters of the orbit so that the Doppler curve will fit the specified data. The user can control the semi-major axis, eccentricity, inclination, node angle, planet mass and the phase. This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Mccray, Richard; Koelemay, Andrew

2008-11-04

323

New laboratory measurements on ammonia's inversion spectrum, with implications for planetary atmospheres  

NASA Astrophysics Data System (ADS)

Microwave spectral measurements have been performed on pure room-temperature gaseous ammonia at frequencies from 1.75 to 18 GHz (1.7-17 cm), at 50-, 100-, and 300-torr pressures. These measurements are part of a laboratory program to measure the microwave absorption spectrum of ammonia, under conditions applicable to giant planet atmospheres, now in progress at the Jet Propulsion Laboratory. The pure ammonia data reported here agree well with previous data by Bleaney and Loubser (1950) at 100 and 300 torrs, and with predictions of the absorptivity formalism published by Berge and Gulkis. Success with pure ammonia but failure with mixtures of ammonia in hydrogen and helium (Spilker, 1990) indicates that the Berge and Gulkis formalism does not correctly handle foreign-gas effects on ammonia inversion lines. This may require modifying conclusions of radio astronomical and radio occultation studies that used this formalism. Notably, a suggested depletion of ammonia and superabundance of hydrogen sulfide may have been exaggerated as a result of inaccuracies in the Berge and Gulkis formalism.

Spilker, T. R.

1993-03-01

324

Microfabricated silicon leak for sampling planetary atmospheres with a mass spectrometer.  

PubMed

A microfabricated silicon mass spectrometer inlet leak has been designed, fabricated, and tested. This leak achieves a much lower conductance in a smaller volume than is possible with commonly available metal or glass capillary tubing. It will also be shown that it is possible to integrate significant additional functionality, such as inlet heaters and valves, into a silicon microleak with very little additional mass. The fabricated leak is compatible with high temperature (up to 500 degrees C) and high pressure (up to 100 bars) conditions, as would be encountered on a Venus atmospheric probe. These leaks behave in reasonable agreement with their theoretically calculated conductance, although this differs between devices and from the predicted value by as much as a factor of 2. This variation is believed to be the result of nonuniformity in the silicon etching process which is characterized in this work. Future versions of this device can compensate for characterized process variations in order to produce devices in closer agreement with designed conductance values. The integration of an inlet heater into the leak device has also been demonstrated in this work. PMID:17614640

Jamieson, B G; Lynch, B A; Harpold, D N; Niemann, H B; Shappirio, M D; Mahaffy, P R

2007-06-01

325

Dynamical Evolution of Planetary Systems  

NASA Astrophysics Data System (ADS)

The apparent regularity of the motion of the giant planets of our solar system suggested for decades that said planets formed onto orbits similar to the current onesand that nothing dramatic ever happened during their lifetime. The discovery of extrasolar planets showed astonishingly that the orbital structure of our planetary system is not typical. Many giant extrasolar planets have orbits with semimajor axes of ˜ 1 AU,and some have even smaller orbital radii, sometimes with orbital periods of just a few days. Moreover, most extrasolar planets have large eccentricities, up to values that only comets have in our solar system. Why is there such a great diversitybetween our solar system and the extrasolar systems, as well as among the extrasolar systems themselves? This chapter aims to give a partial answer to this fundamental question. Its guideline is a discussion of the evolution of our solarsystem, certainly biased by a view that emerges, in part, from a series of works comprising the "Nice model." According to this view, the giant planets of the solar system migrated radially while they were still embedded in a protoplanetary disk of gas and presumably achieved a multi-resonant orbital configuration, characterized by smaller interorbital spacings and smaller eccentricities and inclinations with respect to the current configuration.The current orbits of the giant planets may have been achieved during a phase of orbital instability, during which the planets acquired temporarily large-eccentricity orbits and all experienced close encounters with at least oneother planet. This instability phase occurred presumably during the putative "Late Heavy Bombardment" of the terrestrial planets, approximately ˜ 3.9 Gy ago (Tera et al. 1974). The interaction with a massive, distant planetesimal disk (the ancestor of the current Kuiper belt) eventually damped the eccentricities of the planets, ending the phase of mutual planetary encounters and parking the planets onto their current, stable orbits. This new view of the evolution of the solar system makes our system not very different from the extrasolar ones. In fact, the best explanation for the large orbital eccentricities of extrasolar planets is that the planets that are observed are the survivors of strong instability phases of original multi-planet systems on quasi-circular orbits. The main difference between the solar system and the extrasolar systems is in the magnitude of such an instability. In the extrasolar systems, encounters among giant planets had to be the norm. In our case, the two major planets (Jupiter and Saturn) never had close encounters with each other: They only encountered "minor" planets like Uranus and/or Neptune. This was probably just mere luck, as simulations show that Jupiter-Saturn encounters in principle could have occurred. Another relevant difference with the extrasolar planets is that, during the gas-disk phase, our giant planets avoided migrating permanently into the inner solar system, thanks to the specific mass ratio of the Jupiter/Saturn pair and the rapid disappearance of the disk soon after the formation of the giant planets. This chapter ends on a note on terrestrial planets. The structure of a terrestrial-planet system depends sensitively on the dynamical evolution of the giant planets and on their final orbits. It appears clear that habitable terrestrial planets, with moderate eccentricity orbits, cannot exist in systems where the giant planets became violently unstable and developed very elliptic orbits. Thus, our very existence is possible only because the instability phase experienced by the giant planets of our solar system was of "moderate" strength.

Morbidelli, Alessandro

326

Schumann Resonance: A Tool for Investigating Planetary Atmospheric Electricity and the Origin and Evolution of the Solar System  

NASA Astrophysics Data System (ADS)

In this work we discuss a new technique and associated instrumentation to detect Schumann resonance signatures of planetary environments and subsequently to infer the fraction of volatiles in the gaseous envelopes of the giant planets.

Simoes, F.; Pfaff, R. F.; Hamelin, M.; Beghin, C.; Berthelier, J.-J.; Chamberlin, P.; Farrell, W.; Freudenreich, H.; Grard, R.; Klenzing, J.; Lebreton, J.-P.; Martin, S.; Rowland, D.; Yair, Y.

2012-10-01

327

Earthshine and Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The search for life on extrasolar planets requires first that we find terrestrial-mass planets around nearby stars, and second that we determine habitability and search for signs of life. The Terrestrial Planet Finder missions, a Coronagraph (TPF-C) and an Interferometer (TPF-I in the US, also Darwin in Europe) are designed to carry out these tasks. This talk will focus on how we could determine habitability and search for signs of life with these missions. In the visible and near-infrared, TPF-C could measure O2, H2O, O3, Rayleigh scattering, and the red-edge reflection of land planet leaves; on an early-Earth twin it also could measure CO2 and CH4. In the mid-infrared, TPF-I/Darwin could measure CO2, O3, H2O, and temperature. To validate some of these expectations, we observed Earthshine spectra in the visible and near-infrared, and modeled these spectra with our line-by-line radiative transfer code. We find that the major gas and reflection components are present in the data, and that a simple model of the Earth is adequate to represent the data, within the observational uncertainties. We determined that the Earth appears to be habitable, and also shows signs of life. However to validate the time variable features, including the continent-ocean differences, the presence of weather patterns, the large-scale variability of cloud types and altitude, and the rotation period of the planet, we need to obtain a continuous time-series of observations covering multiple rotations; these observations could be carried out in the coming years, using, for example, a site at the South Pole.

Traub, W. A.; Kaltenegger, L.; Turnbull, M. C.; Jucks, K. W.

2006-05-01

328

Extrasolar planet population synthesis. II. Statistical comparison with observations  

NASA Astrophysics Data System (ADS)

Context: This is the second paper in a series of papers showing the results of extrasolar planet population synthesis calculations using our extended core accretion model. In the companion paper (Paper I), we presented in detail the methods we use. In subsequent papers, we shall discuss the effect of the host star's mass on the planetary population and the influence of various properties of protoplanetary disks. Aims: In this second paper, we focus on planets orbiting solar-like stars. The goal is to use the main characteristics of the actually observed extrasolar planet population to derive in a statistical manner constraints on the planet formation models. Methods: Drawing initial conditions for our models at random from probability distributions derived as closely as possible from observations, we synthesize a number of planetary populations. By applying an observational detection bias appropriate for radial velocity surveys, we identify the potentially detectable synthetic planets. The properties of these planets are compared in quantitative statistical tests with the properties of a carefully selected sub-population of actually observed extrasolar planets. Results: We use a two dimensional Kolmogorov-Smirnov test to compare the mass-distance distributions of synthetic and observed planets, as well as the one dimensional version of the test to compare the M sin i, the semimajor axis and the [Fe/H] distribution. We find that while many combinations of parameters lead to unacceptable distributions, a number of models can account to a reasonable degree of statistical significance for most of the properties of the observed sample. We concurrently account for many other observed features, e.g. the “metallicity effect”. This gives us confidence that our model captures several essential features of giant planet formation. In addition, the fact that many parameter combinations could be rejected indicates that planet population synthesis is indeed a promising approach to constrain formation models. Our simulations allow us also to extract a number of properties of the underlying exoplanet population that are not yet directly detectable. For example, we have derived the planetary initial mass function (PIMF) and have been led to conclude that the planets detected so far represent only the tip of the iceberg (9%) of all the existing planets. The PIMF can also be used to predict how the detectable extrasolar planet population will change as the instrumental precision of radial velocity surveys improves from ~10 m/s to ~1 m/s, or even to an extreme precision of 0.1 m/s.

Mordasini, C.; Alibert, Y.; Benz, W.; Naef, D.

2009-07-01

329

Detecting extrasolar planets from stellar radial velocities using Bayesian evidence  

NASA Astrophysics Data System (ADS)

Stellar radial velocity (RV) measurements have proven to be a very successful method for detecting extrasolar planets. Analysing RV data to determine the parameters of the extrasolar planets is a significant statistical challenge owing to the presence of multiple planets and various degeneracies between orbital parameters. Determining the number of planets favoured by the observed data is an even more difficult task. Bayesian model selection provides a mathematically rigorous solution to this problem by calculating marginal posterior probabilities of models with different number of planets, but the use of this method in extrasolar planetary searches has been hampered by the computational cost of the evaluating Bayesian evidence. None the less, Bayesian model selection has the potential to improve the interpretation of existing observational data and possibly detect yet undiscovered planets. We present a new and efficient Bayesian method for determining the number of extrasolar planets, as well as for inferring their orbital parameters, without having to calculate directly the Bayesian evidence for models containing a large number of planets. Instead, we work iteratively and at each iteration obtain a conservative lower limit on the odds ratio for the inclusion of an additional planet into the model. We apply this method to simulated data sets containing one and two planets and successfully recover the correct number of planets and reliable constraints on the orbital parameters. We also apply our method to RV measurements of HD 37124, 47 Ursae Majoris and HD 10180. For HD 37124, we confirm that the current data strongly favour a three-planet system. We find strong evidence for the presence of a fourth planet in 47 Ursae Majoris, but its orbital period is suspiciously close to 1 yr, casting doubt on its validity. For HD 10180 we find strong evidence for a six-planet system.

Feroz, F.; Balan, S. T.; Hobson, M. P.

2011-08-01

330

PLANETARY CONSTRUCTION ZONES IN OCCULTATION: DISCOVERY OF AN EXTRASOLAR RING SYSTEM TRANSITING A YOUNG SUN-LIKE STAR AND FUTURE PROSPECTS FOR DETECTING ECLIPSES BY CIRCUMSECONDARY AND CIRCUMPLANETARY DISKS  

SciTech Connect

The large relative sizes of circumstellar and circumplanetary disks imply that they might be seen in eclipse in stellar light curves. We estimate that a survey of {approx}10{sup 4} young ({approx}10 million year old) post-accretion pre-main-sequence stars monitored for {approx}10 years should yield at least a few deep eclipses from circumplanetary disks and disks surrounding low-mass companion stars. We present photometric and spectroscopic data for a pre-main-sequence K5 star (1SWASP J140747.93-394542.6 = ASAS J140748-3945.7), a newly discovered {approx}0.9 M{sub Sun} member of the {approx}16 Myr old Upper Centaurus-Lupus subgroup of Sco-Cen at a kinematic distance of 128 {+-} 13 pc. This star exhibited a remarkably long, deep, and complex eclipse event centered on 2007 April 29 (as discovered in Super Wide Angle Search for Planets (SuperWASP) photometry, and with portions of the dimming confirmed by All Sky Automated Survey (ASAS) data). At least five multi-day dimming events of >0.5 mag are identified, with a >3.3 mag deep eclipse bracketed by two pairs of {approx}1 mag eclipses symmetrically occurring {+-}12 days and {+-}26 days before and after. Hence, significant dimming of the star was taking place on and off over at least a {approx}54 day period in 2007, and a strong >1 mag dimming event occurring over a {approx}12 day span. We place a firm lower limit on the period of 850 days (i.e., the orbital radius of the eclipser must be >1.7 AU and orbital velocity must be <22 km s{sup -1}). The shape of the light curve is similar to the lopsided eclipses of the Be star EE Cep. We suspect that this new star is being eclipsed by a low-mass object orbited by a dense inner disk, further girded by at least three dusty rings of optical depths near unity. Between these rings are at least two annuli of near-zero optical depth (i.e., gaps), possibly cleared out by planets or moons, depending on the nature of the secondary. For possible periods in the range 2.33-200 yr, the estimated total ring mass is {approx}8-0.4 M{sub Moon} (if the rings have optical opacity similar to Saturn's rings), and the edge of the outermost detected ring has orbital radius {approx}0.4-0.09 AU. In the new era of time-domain astronomy opened by surveys like SuperWASP, ASAS, etc., and soon to be revolutionized by Large Synoptic Survey Telescope, discovering and characterizing eclipses by circumplanetary and circumsecondary disks will provide us with observational constraints on the conditions that spawn satellite systems around gas giant planets and planetary systems around stars.

Mamajek, Eric E.; Quillen, Alice C.; Pecaut, Mark J.; Moolekamp, Fred; Scott, Erin L. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States); Kenworthy, Matthew A. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Cameron, Andrew Collier; Parley, Neil R. [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom)

2012-03-15

331

Planetary Ionospheres, Summary of the Panel Discussion.  

National Technical Information Service (NTIS)

This paper is intended to provide a very brief introduction to some current concepts of planetary atmospheres for the purpose of considering planetary ion molecule reactions. Model calculations of neutral and ionic species concentrations for the upper atm...

R. S. Narcisi

1975-01-01

332

Five New Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We report multiple Doppler measurements of five nearby FGK main-sequence stars and subgiants obtained during the past 4-6 yr at the Keck Observatory. These stars, namely, HD 183263, HD 117207, HD 188015, HD 45350, and HD 99492, all exhibit coherent variations in their Doppler shifts consistent with a planet in Keplerian motion. The five new planets occupy known realms of planetary parameter space, including a wide range of orbital eccentricities, e=0-0.78, and semimajor axes, 0.1-3.8 AU, that provide further statistical information about the true distributions of various properties of planetary systems. One of the planets, HD 99492b, has a low minimum mass of 0.112MJup=36MEarth. Four of the five planets orbit beyond 1 AU. We describe two quantitative tests of the false alarm probability for Keplerian interpretations of measured velocities. The more robust of these involves Monte Carlo realizations of scrambled velocities as a proxy for noise. Keplerian orbital fits to that ``noise'' yield the distribution of ?2? to compare with ?2? from the original (unscrambled) velocities. We establish a 1% false alarm probability as the criterion for candidate planets. All five of these planet-bearing stars are metal-rich, with [Fe/H]>+0.27, reinforcing the strong correlation between planet occurrence and metallicity. From the full sample of 1330 stars monitored at Keck, Lick, and the Anglo-Australian Telescope, the shortest orbital period for any planet is 2.64 days, showing that shorter periods occur less frequently than 0.1% in the solar neighborhood. Photometric observations were acquired for four of the five host stars with an automatic telescope at Fairborn Observatory. The lack of brightness variations in phase with the radial velocities supports planetary-reflex motion as the cause of the velocity variations. No transits were observed, but their occurrence is not ruled out by our observations. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by both NASA and the University of California.

Marcy, Geoffrey W.; Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A.; Henry, Gregory W.; Laughlin, Greg; Wright, Jason T.; Johnson, John A.

2005-01-01

333

Planetary wave coupling in the middle atmosphere (20-90km): A CUJO study involving TOMS, MetO and MF radar data  

NASA Astrophysics Data System (ADS)

The atmospheric coupling due to Planetary Waves (PW) in the middle atmosphere (20-90km) has been studied using TOMS, MetO and MFR data. The wavelet and wave number analyses have been applied to all parameters at five CUJO (Canada US Japan Opportunity) locations. The CUJO network covers latitudes of 31-52° N and longitudes from 81° W to 142° E, and allows for the assessment of longitudinal variability. The results of temporal and spectral comparisons show that the total ozone (TOMS) and MetO temperatures at low stratospheric heights (typically 100mbar) have high values of correlation as well as similar spectral content. The eastward motions dominate at low stratospheric heights (100mbar), while westward motions became comparable or even stronger in the upper stratosphere (0.46mbar). During the summer months a reduction of PW activity has been observed in the stratosphere, especially at its upper heights, and in the upper middle atmosphere. The MetO (0.32mbar, 55km) and MFR winds (circa 60km) are in good general agreement, especially for the zonal component. Several examples of planetary wave activity at different atmospheric levels throughout the middle atmosphere have been presented. These examples include an eastward propagating 15-day disturbance with wave number 6, that has been observed only at low stratospheric heights; long-period (20-30 days) oscillations with wave number ~1 that have been detected in a wide height range (20-90km); and an oscillation with period near 16 days that was found only at mesospheric heights.

Chshyolkova, T.; Manson, A. H.; Meek, C. E.; Avery, S. K.; Thorsen, D.; MacDougall, J. W.; Hocking, W.; Murayama, Y.; Igarashi, K.

2005-06-01

334

Adaptive Optics for Direct Detection of Extrasolar Planets: The Gemini Planet Imager  

SciTech Connect

The direct detection of photons emitted or reflected by extrasolar planets, spatially resolved from their parent star, is a major frontier in the study of other solar systems. Direct detection will provide statistical information on planets in 5-50 AU orbits, inaccessible to current Doppler searches, and allow spectral characterization of radius, temperature, surface gravity, and perhaps composition. Achieving this will require new dedicated high-contrast instruments. One such system under construction is the Gemini Planet Imager (GPI.) This combines a high-order/high-speed adaptive optics system to control wavefront errors from the Earth's atmosphere, an advanced coronagraph to block diffraction, ultrasmooth optics, a precision infrared interferometer to measure and correct systematic errors, and a integral field spectrograph/polarimeter to image and characterize target planetary systems. We predict that GPI will be able to detect planets with brightness less than 10{sup -7} of their parent star, sufficient to observe warm self-luminous planets around a large population of targets.

Macintosh, B; Graham, J; Palmer, D; Doyon, R; Gavel, D; Larkin, J; Oppenheimer, B; Saddlemyer, L; Wallace, J K; Bauman, B; Erikson, D; Poyneer, L; Sivaramakrishnan, A; Soummer, R; Veran, J

2007-04-24

335

Phase Functions and Light Curves of Wide-Separation Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

We calculate self-consistent extrasolar giant planet (EGP) phase functions and light curves for orbital distances ranging from 0.2 to 15 AU. We explore the dependence on wavelength, cloud condensation, and Keplerian orbital elements. We find that the light curves of EGPs depend strongly on wavelength, the presence of clouds, and cloud particle sizes. Furthermore, the optical and infrared colors of most EGPs are phase-dependent, tending to be reddest at crescent phases in V-R and R-I. Assuming circular orbits, we find that at optical wavelengths most EGPs are 3-4 times brighter near full phase than near greatest elongation for highly inclined (i.e., close to edge-on) orbits. Furthermore, we show that the planet/star flux ratios depend strongly on the Keplerian elements of the orbit, particularly inclination and eccentricity. Given a sufficiently eccentric orbit, an EGP's atmosphere may make periodic transitions from cloudy to cloud-free, an effect that may be reflected in the shape and magnitude of the planet's light curve. Such elliptical orbits also introduce an offset between the time of the planet's light-curve maximum and the time of full planetary phase, and for some sets of orbital parameters, this light-curve maximum can be a steeply increasing function of eccentricity. We investigate the detectability of EGPs by proposed space-based direct-imaging instruments.

Sudarsky, David; Burrows, Adam; Hubeny, Ivan; Li, Aigen

2005-07-01

336

On the Secular Resonances Occured in Planetary Systems  

Microsoft Academic Search

We present different orbital topologies for extrasolar planetary systems including a 2:1 mean motion resonance namely the Gliese 876 HD 82943 and HD 160691 planetary systems as well as the pair Io-Europa in our solar system. Using a new technique called MEGNO we show that the orbital parameters may allow the existence of a stability zone in the semi-major axes

Eric Bois; Nicolas Rambaux; Ludmila Kiseleva-Eggleton; Elke Pilat-Lohinger

2003-01-01

337

Secular Evolution of Hierarchical Planetary Systems  

Microsoft Academic Search

We investigate the dynamical evolution of coplanar, hierarchical, two-planet systems where the ratio of the orbital semimajor axes alpha=a1\\/a2 is small. Hierarchical two-planet systems are likely to be ubiquitous among extrasolar planetary systems. We show that the orbital parameters obtained from a multiple-Kepler fit to the radial velocity variations of a host star are best interpreted as Jacobi coordinates and

Man Hoi Lee; S. J. Peale

2003-01-01

338

A Search for Extrasolar Giant Planets in the Nearby TW Hya Association  

NASA Astrophysics Data System (ADS)

One of the primary goals of NASA's mission is the identification of formed and nascent planetary systems. As the nature of giant planets is to cool off quickly as they age, the best stars around which to search for extrasolar giant planets {EGPs} are nearby pre-main sequence {PMS} stars. In this proposal, we identify a unique opportunity for pursuing these goals: we have identified a cluster of five T Tauri stars {TTS} only 39-60 pc from Earth. These stars are at least three times closer than any previously identified TTS. We request time to carry out a three-filter {F164N, F190N, F215N} observing program designed to detect EGPs and brown dwarfs {BDs} around four of these stars by comparison of the observations with model predictions of H_2 absorption in the atmospheres of cool, gaseous objects. Because these stars are only 20 MY old, any associated EGPs and BDs intrinsically will be 3^m-6^m brighter than similar objects of ages 0.1-1.0 Gyr {e.g., those in the Pleiades or Hyades clusters}; and by virtue of the proximity of these stars, such objects will be brighter by 3^m in comparision to young EGPs and BDs in the next closest clusters of PMS stars. In addition, by virtue of their proximity, we have the unprecedented opportunity to image substellar objects within 20 AU of these TTS. This is the region of space not accessible to the GTO programs of coronagraphic imaging of three of these stars yet it is an accessible region for these stars and is a region of fundamental importance for planetary formation.

Weintraub, David

1997-12-01

339

A TIME-DEPENDENT RADIATIVE MODEL FOR THE ATMOSPHERE OF THE ECCENTRIC EXOPLANETS  

SciTech Connect

We present a time-dependent radiative model for the atmosphere of extrasolar planets that takes into account the eccentricity of their orbit. In addition to the modulation of stellar irradiation by the varying planet-star distance, the pseudo-synchronous rotation of the planets may play a significant role. We include both of these time-dependent effects when modeling the planetary thermal structure. We investigate the thermal structure and spectral characteristics for time-dependent stellar heating for two highly eccentric planets. Finally, we discuss observational aspects for those planets suitable for Spitzer measurements and investigate the role of the rotation rate.

Iro, N. [LESIA, Observatoire de Paris-Meudon, place Jules Janssen, 92395 Meudon Cedex (France); Deming, L. D., E-mail: nicolas.iro@nasa.go, E-mail: leo.d.deming@nasa.go [NASA/Goddard Space Flight Center, Planetary Systems Laboratory, Code 693, Greenbelt, MD 20771 (United States)

2010-03-20

340

Wave activity (planetary, tidal) throughout the middle atmosphere (20-100km) over the CUJO network: Satellite (TOMS) and Medium Frequency (MF) radar observations  

NASA Astrophysics Data System (ADS)

Planetary and tidal wave activity in the tropopause-lower stratosphere and mesosphere-lower thermosphere (MLT) is studied using combinations of ground-based (GB) and satellite instruments (2000-2002). The relatively new MFR (medium frequency radar) at Platteville (40° N, 105° W) has provided the opportunity to create an operational network of middle-latitude MFRs, stretching from 81° W-142° E, which provides winds and tides 70-100km. CUJO (Canada U.S. Japan Opportunity) comprises systems at London (43° N, 81° W), Platteville (40° N, 105° W), Saskatoon (52° N, 107° W), Wakkanai (45° N, 142° E) and Yamagawa (31° N, 131° E). It offers a significant 7000-km longitudinal sector in the North American-Pacific region, and a useful range of latitudes (12-14°) at two longitudes. Satellite data mainly involve the daily values of the total ozone column measured by the Earth Probe (EP) TOMS (Total Ozone Mapping Spectrometer) and provide a measure of tropopause-lower stratospheric planetary wave activity, as well as ozone variability. Climatologies of ozone and winds/tides involving frequency versus time (wavelet) contour plots for periods from 2-d to 30-d and the interval from mid 2000 to 2002, show that the changes with altitude, longitude and latitude are very significant and distinctive. Geometric-mean wavelets for the region of the 40° N MFRs demonstrate occasions during the autumn, winter and spring months when there are similarities in the spectral features of the lower atmosphere and at mesopause (85km) heights. Both direct planetary wave (PW) propagation into the MLT, nonlinear PW-tide interactions, and disturbances in MLT tides associated with fluctuations in the ozone forcing are considered to be possible coupling processes. The complex horizontal wave numbers of the longer period oscillations are provided in frequency contour plots for the TOMS satellite data to demonstrate the differences between lower atmospheric and MLT wave motions and their directions of propagation.

Manson, A. H.; Meek, C. E.; Chshyolkova, T.; Avery, S. K.; Thorsen, D.; MacDougall, J. W.; Hocking, W.; Murayama, Y.; Igarashi, K.

2005-02-01

341

The Transport of Nitric Oxide in the Upper Atmosphere by Planetary Waves and the Zonal Mean Circulation.  

National Technical Information Service (NTIS)

A time-dependent numerical model was developed and used to study the interaction between planetary waves, the zonal mean circulation, and the trace constituent nitric oxide in the region between 55 km and 120 km. The factors which contribute to the struct...

G. A. Jones S. K. Avery

1982-01-01

342

Progress in planetary exploration  

NASA Astrophysics Data System (ADS)

Papers are presented in the areas of planetary structure and composition, comparative planetology, the space investigation of comets, asteroids and cosmic dust, planetary atmospheres, Venus observations, the outer planets, and the formation and evolution of the solar system. Specific topics include the magnetic fields of Mercury, Venus and Mars, the chemical composition and optical properties of terrestrial planet atmospheres, results of the Pioneer fly-by of Saturn and its rings, the flux of earth-crossing and moon-cratering interplanetary objects, and the orbital dynamics of magnetospherically trapped lunar ejecta. Attention is also given to space-borne zodiacal light photometry, Pioneer Orbiter observations of equatorial clouds on Venus, the photoelectron spectrum in the Mars atmosphere, the magnetic fields of Jupiter and Saturn, the shape of rapidly rotating asteroids, and dynamical planetary systems accounting for the structures and evolution of terrestrial-type planets.

Shorthill, R. W.; Marov, M. Ia.; McDonnell, J. A. M.

343

Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

344

Maintenance of Equatorial Superrotation of a Planetary Atmosphere: Analytic Evaluations of the Zonal Momentum Budget for the Stratospheres of Venus, Titan and Earth  

NASA Astrophysics Data System (ADS)

The long-standing problem of the existence of equatorial superrotation in a slowly rotating planetary atmosphere has been solved analytically. Each of ten terms in the averaged zonal momentum equation is analyzed systematically, first by scale analysis, then through analytic formulations and numerical evaluations, and finally by comparison with well-known planetary atmospheres. Key parameters of the analytic formulations are found to agree with observational constraints, resulting in a formulation consistent with fundamental physical concepts. The analytic forms of the approach explicitly show how an equatorial superrotation is dependent on various external and internal parameters. The main results are: (i) Venus equatorial superrotation of 118 m/s results primarily from a balance between the momentum source of the pumping by thermal tides and the momentum sink of the meridional advection of wind shear by horizontal branches of the Hadley circulation; (ii) no solution is found for Titan's stratospheric equatorial superrotation at 1-mb level; (iii) however, if the main absorption layer of the solar radiation in Titan's stratosphere is lifted from 1 mb ( ˜ 185 km) to 0.1 mb ( ˜ 288 km), an equatorial superrotation of ˜ 110 m/s can be maintained at the 0.1-mb level; (iv) a dust cloud in the Earth's lower stratosphere at the 100-mb level, such as one produced by an asteroid impact, can also produce an equatorial superrotation of ˜ 120 m/s; (v) the postulated superrotation in the atmosphere of either Titan or Earth results mainly from a balance between the momentum source of the tidal pumping and the momentum sink of the frictional drag force; (vi) superrotation in Earth's lower stratosphere can enhance the meridional transport of dust clouds. This increased meridional transport can, for example, accelerate the globalization of unfavorable environments for the survival of the dinosaurs, following an asteroid impact. Detailed analyses also lead to the following more general results on the equatorial superrotation: (i) planetary rotation rate is not crucial for the existence of an equatorial superrotation; (ii) it is unlikely that the eddy horizontal momentum transfer in a slowly rotating atmosphere such as Venus' is against its gradient, though this remains an open question; and (iii) upward momentum flux by Hadley circulation below the jet center of an equatorial superrotation is a momentum sink, which will impede rather than assist the formation of the equatorial superrotation. This work was supported by NASA Grant NAG5-11962.

Zhu, X.

2004-11-01

345

On Planetary Evolution and the Evolution of Planetary Science During the Career of Don Anderson  

NASA Astrophysics Data System (ADS)

The planets of our solar system have long been viewed by Don Anderson as laboratories for testing general aspects of planetary evolution and as points of comparison to the Earth. I was fortunate to have been a student 39 years ago in a course at Caltech that Don taught with Bob Kovach on the interiors of the Earth and the planets. At that time, Mariner 4 had not yet flown by Mars, the lunar Ranger program was still in progress, and it was permissible to entertain the hypothesis that all of the terrestrial planets were identical in bulk composition. In the last four decades spacecraft have visited every planet from Mercury to Neptune; samples from the Moon, Mars, asteroids, and comets reside in our laboratories; and more than 100 planets have been discovered orbiting other stars. More importantly, traditionally distinct fields have merged to the point where planetary scientists must be conversant with the findings and modes of thinking from astronomy and biology as well as the geosciences. A few examples illustrate this confluence. Theoretical models for the structure of the atmospheres of gas-giant planets led to the first astronomical detection of an extrasolar planetary atmosphere for the transiting planet HD209458b. Although the atmospheric models were based on those for solar-system gas giants, the 3.5-day orbital period means that this planet is 100 times closer to its star than Jupiter is to the Sun, its effective temperature is 1100 K, and the detected signature of the planetary atmosphere was absorption by neutral sodium. Sodium in Mercury's exosphere, detected astronomically from Earth, figures into the question of how the terrestrial planets came to have distinct bulk compositions. Hypotheses to account for Mercury's high uncompressed density, and by inference its high ratio of metal to silicate, range from chemical gradients in the early solar nebula to preferential removal of silicates from a differentiated protoplanet by nebular heating or giant impact disruption, processes that would have affected the final composition of the other inner planets to lesser degrees. These hypotheses will be distinguishable by future remote sensing measurements from a spacecraft in Mercury orbit, but all lead to the prediction that volatile species such as sodium should be deficient in Mercury's silicate fraction. The most recent models for Mercury's exosphere are consistent with the idea that the required fresh supply of sodium from Mercury's surface is no greater than that predicted for meteorite infall. One of the leading questions driving the current exploration of Mars is whether the surface or subsurface was ever conducive to the origin and evolution of life. Sites of hydrothermal circulation within the crust may have provided the necessary energy and chemical building blocks. Remote sensing of candidate hydrothermal minerals at the Martian surface is the leading technique being used to seek such sites, but paleomagnetism may offer another route. Several hypotheses link hydrothermal activity to either the formation of magnetic carriers during the lifetime of the Martian dynamo or the alteration of such carriers after the dynamo ceased, leading to the possibility that high-resolution mapping of crustal magnetism may provide a prospecting tool for promising Martian biological habitats. As Don Anderson showed us by example throughout his career, students of the Earth need not confine their attention to a single planet or even a single planetary system. The lessons from diverse fields that planetary scientists must master to stay current will keep all of us --- like Don --- young and curious.

Solomon, S. C.

2003-12-01

346

Planetary Science Advances with the International X-ray Observatory  

NASA Astrophysics Data System (ADS)

X-ray studies of planetary systems are beginning to provide important insights inaccessible at other wavelengths. In our Solar System, charge exchange emission from solar particles is faint and variable with complex spectra, a situation well-matched to the planned International X-ray Observatory's high-throughput and high spectral resolution. Solar-type stars universally exhibit enhanced magnetic activity during their youth so that X-ray studies reveal the high-energy inputs to protoplanetary disks and planetary atmospheres. It is possible that X-ray illumination is a critical regulator to the formation of planets. This paper is based on the report of the Con-X ``Solar System, Planet Formation and Evolution'' Science Panel. (1) X-ray irradiation of protoplanetary disks can be probed with the 6.4 keV iron fluorescent line. Seen in a handful of protostars with Chandra and XMM, IXO will survey the line in hundreds of young stellar systems and will quantify the 10-30 keV emission stellar emission that can penetrate deep into the disk. In a few cases, X-ray `superflares' will permit disk reverberation mapping. Combined with infrared and submillimeter studies, IXO will establish the importance of X-ray illumination on protoplanetary disk physics and chemistry. (2) Planetary atmospheres show rapidly varying X-ray components from charge exchange of heavy solar wind ions, electron bremsstrahlung continuum from ion-neutral interactions, and scattering and fluorescence of solar X-ray emission. IXO will produce a movie of these effects in Jupiter as the planet rotates and responds to solar flare/CME events. IXO study of the remarkable Martian X-ray exosphere will constrain the evaporation of planetary atmospheres. Three additional science programs are outlined: study of charge exchange processes in cometary comae; spectroscopy of diffuse heliospheric charge exchange X-rays previously attributed to the hot local interstellar medium; and measurements of flaring in stars hosting extrasolar planets in the Habitable Zone to evaluate atmospheric evaporation.

Feigelson, Eric; Elsner, R.; Glassgold, A.; Guedel, M.; Montmerle, T.; Wargelin, B.; Wolk, S.

2009-01-01

347

Planetary rings  

SciTech Connect

Among the topics discussed are the development history of planetary ring research, the view of planetary rings in astronomy and cosmology over the period 1600-1900, the characteristics of the ring systems of Saturn and Uranus, the ethereal rings of Jupiter and Saturn, dust-magnetosphere interactions, the effects of radiation forces on dust particles, the collisional interactions and physical nature of ring particles, transport effects due to particle erosion mechanisms, and collision-induced transport processes in planetary rings. Also discussed are planetary ring waves, ring particle dynamics in resonances, the dynamics of narrow rings, the origin and evolution of planetary rings, the solar nebula and planetary disk, future studies of the planetary rings by space probes, ground-based observatories and earth-orbiting satellites, and unsolved problems in planetary ring dynamics.

Greenberg, R.; Brahic, A.

1984-01-01

348

Climate and Atmospheric Modeling Studies. Climate Applications of Earth and Planetary Observations. Chemistry of Earth and Environment.  

National Technical Information Service (NTIS)

The research conducted during the past year in the climate and atmospheric modeling programs concentrated on the development of appropriate atmospheric and upper ocean models, and preliminary applications of these models. Principal models are a one-dimens...

1990-01-01

349

EVOLUTION OF THE SOLAR ACTIVITY OVER TIME AND EFFECTS ON PLANETARY ATMOSPHERES. II. {kappa}{sup 1} Ceti, AN ANALOG OF THE SUN WHEN LIFE AROSE ON EARTH  

SciTech Connect

The early evolution of Earth's atmosphere and the origin of life took place at a time when physical conditions at the Earth were radically different from its present state. The radiative input from the Sun was much enhanced in the high-energy spectral domain, and in order to model early planetary atmospheres in detail, a knowledge of the solar radiative input is needed. We present an investigation of the atmospheric parameters, state of evolution, and high-energy fluxes of the nearby star {kappa}{sup 1} Cet, previously thought to have properties resembling those of the early Sun. Atmospheric parameters were derived from the excitation/ionization equilibrium of Fe I and Fe II, profile fitting of H{alpha}, and the spectral energy distribution. The UV irradiance was derived from Far-Ultraviolet Spectroscopic Explorer and Hubble Space Telescope data, and the absolute chromospheric flux from the H{alpha} line core. From careful spectral analysis and the comparison of different methods, we propose for {kappa}{sup 1} Cet the following atmospheric parameters: T{sub eff} = 5665 {+-} 30 K (H{alpha} profile and energy distribution), log g = 4.49 {+-} 0.05 dex (evolutionary and spectroscopic), and [Fe/H] = +0.10 {+-} 0.05 (Fe II lines). The UV radiative properties of {kappa}{sup 1} Cet indicate that its flux is some 35% lower than the current Sun's between 210 and 300 nm, it matches the Sun's at 170 nm, and increases to at least 2-7 times higher than the Sun's between 110 and 140 nm. The use of several indicators ascribes an age to {kappa}{sup 1} Cet in the interval {approx}0.4-0.8 Gyr and the analysis of the theoretical Hertzsprung-Russell diagram (H-R) suggests a mass {approx}1.04 M{sub sun}. This star is thus a very close analog of the Sun when life arose on Earth and Mars is thought to have lost its surface bodies of liquid water. Photochemical models indicate that the enhanced UV emission leads to a significant increase in photodissociation rates compared with those commonly assumed of the early Earth. Our results show that reliable calculations of the chemical composition of early planetary atmospheres need to account for the stronger solar photodissociating UV irradiation.

Ribas, I.; Garces, A. [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5, parell, 2a pl., E-08193 Bellaterra (Spain); Porto de Mello, G. F.; Ferreira, L. D. [Universidade Federal do Rio de Janeiro, Observatorio do Valongo, Ladeira do Pedro Antonio 43, CEP: 20080-090, Rio de Janeiro, RJ (Brazil); Hebrard, E.; Selsis, F. [Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France); Catalan, S. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Do Nascimento, J. D.; De Medeiros, J. R., E-mail: iribas@ice.csic.e, E-mail: garces@ice.csic.e, E-mail: gustavo@astro.ufrj.b, E-mail: leticia@astro.ufrj.b, E-mail: franck.selsis@obs.u-bordeaux1.f, E-mail: eric.hebrard@obs.u-bordeaux1.f, E-mail: s.catalan@herts.ac.u, E-mail: dias@dfte.ufrn.b, E-mail: renan@dfte.ufrn.b [Departamento de Fisica, Universidade Federal do Rio Grande do Norte, CEP: 59072-970, Natal, RN (Brazil)

2010-05-01

350

Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z  

SciTech Connect

Papers from the conference are presented, and the topics covered include the following: planetary geology, meteorites, planetary composition, meteoritic composition, planetary craters, lunar craters, meteorite craters, petrology, petrography, volcanology, planetary crusts, geochronology, geomorphism, mineralogy, lithology, planetary atmospheres, impact melts, K-T Boundary Layer, volcanoes, planetary evolution, tectonics, planetary mapping, asteroids, comets, lunar soil, lunar rocks, lunar geology, metamorphism, chemical composition, meteorite craters, planetary mantles, and space exploration. Separate abstracts have been prepared for articles from this report.

Not Available

1993-01-01

351

An Investigation on the role of Planetary Boundary Layer Parameterization scheme on the performance of a hydrostatic atmospheric model over a Coastal Region  

NASA Astrophysics Data System (ADS)

As part of the ocean/land-atmosphere interaction, more than half of the total kinetic energy is lost within the lowest part of atmosphere, often referred to as the planetary boundary layer (PBL). A comprehensive understanding of the energetics of this layer and turbulent processes responsible for dissipation of kinetic energy within the PBL require accurate estimation of sensible and latent heat flux and momentum flux. In numerical weather prediction (NWP) models, these quantities are estimated through different surface-layer and PBL parameterization schemes. This research article investigates different factors influencing the accuracy of a surface-layer parameterization scheme used in a hydrostatic high-resolution regional model (HRM) in the estimation of surface-layer turbulent fluxes of heat, moisture and momentum over the coastal regions of the Indian sub-continent. Results obtained from this sensitivity study of a parameterization scheme in HRM revealed the role of surface roughness length (z_{0}) in conjunction with the temperature difference between the underlying ground surface and atmosphere above (?T = T_{G} - T_{A}) in the estimated values of fluxes. For grid points over the land surface where z_{0} is treated as a constant throughout the model integration time, ?T showed relative dominance in the estimation of sensible heat flux. In contrast to this, estimation of sensible and latent heat flux over ocean were found to be equally sensitive on the method adopted for assigning the values of z_{0} and also on the magnitudes of ?T.

Anurose, J. T.; Subrahamanyam, Bala D.

2012-07-01

352

Search for Radio Emissions from Extrasolar Planets: The Observation Campaign  

NASA Astrophysics Data System (ADS)

Non-thermal, low-frequency radio emissions have been observed for decades from planets in our solar system, and they are also expected from the magnetospheres of extrasolar planets. Particularly from "Hot Jupiters", extrasolar planets of Jupiter size that orbit their primary at very close range (<0.1 AU in some cases), we expect the radiated power to be strong enough to allow detection from Earth. This is because the energy input into a magnetosphere so close to a star is orders of magnitude larger than that experienced by our own Jupiter. Using the new 150 MHz receivers of the Giant Metrewave Radiotelescope (GMRT) in India, we have searched for radio emissions from a sub-set of known "hot Jupiters". We have selected three primary and two backup targets, based on the expected flux density and the level of background noise. No observation of these targets has been attempted previously at these frequencies with the sensitivity and aperture offered by GMRT. Calibrations with GMRT at 150 MHz have confirmed the noise floor to be 2 mJy over a 5 MHz bandwidth. The noise floor is well below the expected flux levels from the targets. Our search strategy included a focus on those planetary emissions that may be caused by impulsive events on the primary star. For this reason, the target primaries where monitored for impulsive events with near-simulatenous optical observations. This paper will describe the campaign, and present the preliminary results.

Winterhalter, D.; Bryden, G.; Chandra, I. C.; Gonzalez, W.; Kuiper, T. B.; Lazio, J.; Majid, W. A.; Treumann, R.; Zarka, P.

2005-05-01

353

Planetas extrasolares con pequeño semieje orbital  

NASA Astrophysics Data System (ADS)

The discovery of extra-solar planets, first surrounding a pulsar (PSR1257+12, Malhotra et al 1992) and then main-sequence stars similar to our sun, (http://exoplanets.org) has opened a new field of study inside the dynamic of planetary systems. Although the information we have of these objects is determined by the own limitations of the detection methods that are used, important differences between these systems and the Solar System were observed. The mass of these planets are, in general, bigger than Jupiter, the measured semimayor axes have a low limit of 0.04 AU, the ten part of Mercury semimayor axe. Further, the excentricities take different values from almost 0 to 0.93, in contrast to our system where the planetary orbits are approximately circular. Among the extra solar planets detected until August 2002, it is possible to observe a deficiency of massive planets (Mp sin I < 3.5 Mj) near the primary star, i.e. semimayor axe below 0.1 AU, with excentricity below 0.2. The goal of this work is to attempt an explanation of these cases by an eliptic planar model in which two point planets interac gravitationaly. The motion equations are analized for different initial conditions by using numerical methods. The motion equations were stated and several pairs of particles were generated by varying the relative masses and the orbital elements. To integrate the equations the Bulirsh - Stoer code was used, with a 10-12 accuracy. As a control variable of the results the calculus of energy was used. The total span of integrations was 106 years. The outputs of the numerical simulations show several dynamic behaviors for the particles: - Lower mass escapes to the outside of the system - Stability in both bodies - Less massive planet fall to the primary star Moreover, by comparing the results obtained for objets with identical initial conditions in their orbital parameters, but with different relations of mass, it is possible to distinguish two types of behaviours: - during the integration time there is dynamical estability if both masses are below 3.5Mj. - the less massive planet fall to the star if the other mass is about 10Mj. in this case the major body increase his semimajor axe in order to preserve the constancy of the angular moment of the total system. The simulations performed have shown results with a high dependence of the values of the initial conditions and the masses of the planets considered.

Giuliodori, D.; Fernández, S.

354

The University of New South Wales Extrasolar Planet Search  

NASA Astrophysics Data System (ADS)

Our team at the University of New South Wales (UNSW) is searching for transiting extrasolar planets using the 0.5~m Automated Patrol Telescope (APT) at Siding Spring Observatory, Australia. We monitor field stars in pairs of fields (2 × 3 degrees each) at intermediate galactic latitudes (15° ? |b| ? 45°), over runs of approximately two months. To date we have identified 62 planet candidates, though follow-up studies have shown most of these to be eclipsing binary stars. For three remaining candidates a planetary origin of the transit signal has not been ruled out. We are currently analysing follow-up data on two of these. A new CCD camera for the APT --- currently under construction --- will provide higher sensitivity, better image sampling, and up to an 8-fold increase in field of view, increasing our search efficiency accordingly.

Hidas, M. G.; Webb, J. K.; Ashley, M. C. B.; Phillips, M. A.; Christiansen, J. L.; Hamacher, D. W.; Curran, S. J.; Irwin, M.; Aigrain, S.; Irwin, J.

2007-07-01

355

Spectropolarimetric signatures of Earth--like extrasolar planets.  

NASA Astrophysics Data System (ADS)

Numerically calculated scattering matrix elements a1 and b1 of 11 different types of Earth-like extrasolar planets are presented. Matrix element a1 is proportional to the total flux that is reflected by the exoplanet, matrix element b1 is proportional to the linearly polarized flux. Also given is the ratio -b1/a1, which is the degree of linear polarization of the light that is reflected by the exoplanet. Each directory contains 91 ASCII files: one file for each planetary phase angle. The phase angles range from 0 degrees ("a full planet") to 180 degrees ("a new planet"), in steps of 2 degrees. Files are labelled DDDAAN.txt, where DDD is the phase angle and AAN the model code (000fo0.txt for 0 degrees in forest0 model, 000oc0.txt for 0 degrees in ocean_0 model, 000000.txt for 0 degrees in lambert000 model). (11 data files).

Stam, D. M.

356

The extrasolar planet GL 581 d: A potentially habitable planet?  

Microsoft Academic Search

Aims: The planetary system around the M star Gliese 581 contains at least three close-in potentially low-mass planets, Gl 581c, d, and e. In order to address the question of the habitability of Gl 581d, we performed detailed atmospheric modeling studies for several planetary scenarios. Methods: A 1D radiative-convective model was used to calculate temperature and pressure profiles of model

P. von Paris; A. B. C. Patzer; M. Godolt; J. L. Grenfell; P. Hedelt; D. Kitzmann; B. Stracke

2010-01-01

357

Practicality of Using Oxygen Atom Emissions to Evaluate the Habitability of ExtraSolar Planets  

Microsoft Academic Search

It has previously been proposed [Akasofu, 1999] that observation of the O(1S - 1D) green line from the atmospheres of extra-solar planets might be a marker for habitability. Guidance on this question is available within our own solar system. The green line is a dominant feature in the visible terrestrial nightglow, and the ultimate origin of its mesospheric emission is

T. G. Slanger

2005-01-01

358

TIDAL EVOLUTION OF CLOSE-IN EXTRASOLAR PLANETS: HIGH STELLAR Q FROM NEW THEORETICAL MODELS  

SciTech Connect

In recent years it has been shown that the tidal coupling between extrasolar planets and their stars could be an important mechanism leading to orbital evolution. Both the tides the planet raises on the star and vice versa are important and dissipation efficiencies ranging over four orders of magnitude are being used. In addition, the discovery of extrasolar planets extremely close to their stars has made it clear that the estimates of the tidal quality factor, Q, of the stars based on Jupiter and its satellite system and on main-sequence binary star observations are too low, resulting in lifetimes for the closest planets orders of magnitude smaller than their age. We argue that those estimates of the tidal dissipation efficiency are not applicable for stars with spin periods much longer than the extrasolar planets' orbital period. We address the problem by applying our own values for the dissipation efficiency of tides, based on our numerical simulations of externally perturbed volumes of stellar-like convection. The range of dissipation we find for main-sequence stars corresponds to stellar Q{sub *} of 10{sup 8} to 3 x 10{sup 9}. The derived orbit lifetimes are comparable to or much longer than the ages of the observed extrasolar planetary systems. The predicted orbital decay transit timing variations due to the tidal coupling are below the rate of ms yr{sup -1} for currently known systems, but within reach of an extended Kepler mission provided such objects are found in its field.

Penev, Kaloyan; Sasselov, Dimitar [Astronomy Department, Harvard University, 60 Garden St., M.S. 16, Cambridge, MA 02138 (United States)

2011-04-10

359

Microlensing detection of extrasolar planets  

NASA Astrophysics Data System (ADS)

We review the method of exoplanetary microlensing with a focus on two-body planetary lensing systems. The physical properties of planetary systems can be successfully measured by means of a deep analysis of lightcurves and high-resolution imaging of planetary systems, countering the concern that microlensing cannot determine planetary masses and orbital radii. Ground-based observers have had success in diagnosing properties of multi-planet systems from a few events, but space-based observations will be much more powerful and statistically more complete. Since microlensing is most sensitive to exoplanets beyond the snow line, whose statistics, in turn, allow for testing current planetary formation and evolution theories, we investigate the retrieval of semi-major axis density by a microlensing space-based survey with realistic parameters. Making use of a published statistical method for projected exoplanets quantities (Brown 2011), we find that one year of such a survey might distinguish between simple power-law semi-major axis densities. We conclude by briefly reviewing ground-based results hinting at a high abundance of free-floating planets and describing the potential contribution of space-based missions to understanding the frequency and mass distribution of these intriguing objects, which could help unveil the formation processes of planetary systems.

Giannini, Emanuela; Lunine, Jonathan I.

2013-05-01

360

Microlensing detection of extrasolar planets.  

PubMed

We review the method of exoplanetary microlensing with a focus on two-body planetary lensing systems. The physical properties of planetary systems can be successfully measured by means of a deep analysis of lightcurves and high-resolution imaging of planetary systems, countering the concern that microlensing cannot determine planetary masses and orbital radii. Ground-based observers have had success in diagnosing properties of multi-planet systems from a few events, but space-based observations will be much more powerful and statistically more complete. Since microlensing is most sensitive to exoplanets beyond the snow line, whose statistics, in turn, allow for testing current planetary formation and evolution theories, we investigate the retrieval of semi-major axis density by a microlensing space-based survey with realistic parameters. Making use of a published statistical method for projected exoplanets quantities (Brown 2011), we find that one year of such a survey might distinguish between simple power-law semi-major axis densities. We conclude by briefly reviewing ground-based results hinting at a high abundance of free-floating planets and describing the potential contribution of space-based missions to understanding the frequency and mass distribution of these intriguing objects, which could help unveil the formation processes of planetary systems. PMID:23604071

Giannini, Emanuela; Lunine, Jonathan I

2013-04-19

361

Simultaneous observations of the Martian atmosphere by Planetary Fourier Spectrometer on Mars Express and Miniature Thermal Emission Spectrometer on Mars Exploration Rover  

NASA Astrophysics Data System (ADS)

In this study we present temperature profiles in the lower atmosphere of Mars from simultaneous observations performed by the Planetary Fourier Spectrometer (PFS) aboard the Mars Express spacecraft and the Miniature Thermal Emission Spectrometer (Mini-TES) aboard the Mars Exploration Rovers. Thermal infrared spectra were collected in both the upward and downward looking geometries from the surface and from orbit, respectively. We used two sets of criteria to select PFS observations. These criteria took into account the location around the landing sites of the rovers, the local time (LT), and the solar longitude (Ls) corresponding to the Martian solar day (sol). The first set of criteria included PFS measurements carried out within ±1° in latitude and longitude, within 1 h in local time, and on the same sol. From the restricted set of measurements we conclude that the PFS data are consistent with the Mini-TES data. The next set of criteria covered the area 5° × 5° around the landing sites, within 1 h in local time and within 9 sols. The latter criteria allow us to study the variation of parameters LT, distance, and Ls and their influence on changes of temperature profiles. This comparison for the group with relaxed criteria showed also that local time has strongest effect on temperature differences. The main purpose of this study is to confirm the validity of PFS temperature profiles close to the surface. Atmospheric temperatures below 5 km are retrieved from satellite measurements with a large uncertainty because of poor pieces of information in the wings of the CO2 absorption band at 667 cm-1. The Mini-TES temperature profiles span atmospheric layers below 2 km. The good correspondence observed in a number of cases confirms the possibility of using PFS measurements to investigate the lower atmosphere.

Wolkenberg, P.; Grassi, D.; Formisano, V.; Rinaldi, G.; D'Amore, M.; Smith, M.

2009-04-01

362

THERMOCHEMICAL AND PHOTOCHEMICAL KINETICS IN COOLER HYDROGEN-DOMINATED EXTRASOLAR PLANETS: A METHANE-POOR GJ436b?  

SciTech Connect

We introduce a thermochemical kinetics and photochemical model. We use high-temperature bidirectional reaction rates for important H, C, O, and N reactions (most importantly for CH{sub 4} to CO interconversion), allowing us to attain thermochemical equilibrium, deep in an atmosphere, purely kinetically. This allows the chemical modeling of an entire atmosphere, from deep-atmosphere thermochemical equilibrium to the photochemically dominated regime. We use our model to explore the atmospheric chemistry of cooler (T{sub eff} < 10{sup 3} K) extrasolar giant planets. In particular, we choose to model the nearby hot-Neptune GJ436b, the only planet in this temperature regime for which spectroscopic measurements and estimates of chemical abundances now exist. Recent Spitzer measurements with retrieval have shown that methane is driven strongly out of equilibrium and is deeply depleted on the day side of GJ436b, whereas quenched carbon monoxide is abundant. This is surprising because GJ436b is cooler than many of the heavily irradiated hot Jovians and thermally favorable for CH{sub 4}, and thus requires an efficient mechanism for destroying it. We include realistic estimates of ultraviolet flux from the parent dM star GJ436, to bound the direct photolysis and photosensitized depletion of CH{sub 4}. While our models indicate fairly rich disequilibrium conditions are likely in cooler exoplanets over a range of planetary metallicities, we are unable to generate the conditions for substantial CH{sub 4} destruction. One possibility is an anomalous source of abundant H atoms between 0.01 and 1 bars (which attack CH{sub 4}), but we cannot as yet identify an efficient means to produce these hot atoms.

Line, Michael R.; Yung, Yuk L. [California Institute of Technology, Pasadena, CA 91106 (United States); Vasisht, Gautam; Chen, Pin [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Angerhausen, D., E-mail: mrl@gps.caltech.edu, E-mail: gv@s383.jpl.nasa.gov [Hamburger Sternwarte, Universitaet Hamburg, 21029 Hamburg (Germany)

2011-09-01

363

WATER FRACTIONS IN EXTRASOLAR PLANETESIMALS  

SciTech Connect

With the goal of using externally polluted white dwarfs to investigate the water fractions of extrasolar planetesimals, we assemble from the literature a sample that we estimate to be more than 60% complete of DB white dwarfs warmer than 13,000 K, more luminous than 3 Multiplication-Sign 10{sup -3} L{sub Sun }, and within 80 pc of the Sun. When considering all the stars together, we find that the summed mass accretion rate of heavy atoms exceeds that of hydrogen by over a factor of 1000. If so, this sub-population of extrasolar asteroids treated as an ensemble has little water and is at least a factor of 20 drier than CI chondrites, the most primitive meteorites. Furthermore, while an apparent 'excess' of oxygen in a single DB can be interpreted as evidence that the accreted material originated in a water-rich parent body, we show that at least in some cases, there can be sufficient uncertainties in the time history of the accretion rate that such an argument may be ambiguous. Regardless of the difficulty associated with interpreting the results from an individual object, our analysis of the population of polluted DBs provides indirect observational support for the theoretical view that a snow line is important in disks where rocky planetesimals form.

Jura, M.; Xu, S., E-mail: jura@astro.ucla.edu, E-mail: sxu@astro.ucla.edu [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095-1562 (United States)

2012-01-15

364

The Role of Planetary Data System Archive Standards in International Planetary Data Archives  

Microsoft Academic Search

A major objective of NASA's Planetary Data System (PDS) is to efficiently archive and make accessible digital data produced by NASA's planetary missions, research programs, and data analysis programs. The PDS is comprised of a federation of groups known as nodes, with each node focused on archiving and managing planetary data from a given science discipline. PDS nodes include Atmospheres,

Edward Guinness; Susan Slavney; Reta Beebe; Daniel Crichton

2008-01-01

365

Astronomers Report Discovery of New Extra-solar Planets: Four Reports  

NSDL National Science Digital Library

If you are feeling alone in the universe, this news from 2000 of the search for new planets might inspire you. This account is from the popular space science Website, Space.com. It chronicles the latest detection of at least nine possible planetary bodies orbiting stars outside of our solar system. The text includes a discussion of how detection of wobble behavior is used in the search for extra-solar planets and plans for future planet hunts. This site also features links to Websites of the observatories involved in extra-solar planet detection, related Space.com stories, a diagram of Doppler shift due to stellar wobble and a table of the nine planet candidates's size and distance from Earth.

Weinstock, Maia.

2000-01-01

366

Intensity and polarization line profiles in a semi-infinite Rayleigh-scattering planetary atmosphere. I - Integrated flux  

NASA Astrophysics Data System (ADS)

Absorption and polarization line profiles as well as the curves of growth in the integrated light of a planet over the whole range of phase angles have been computed assuming a semi-infinite atmosphere scattering according to Rayleigh's phase-matrix which takes polarization into account. The relative change in line depth and equivalent widths qualitatively agree with the observations of the CO2 bands in Venus reported by Young, Schorn and Young (1980). It is pointed out that the bands might be formed in a part of the atmosphere which is different from that where continuum polarization originates.

Bhatia, R. K.; Abhyankar, K. D.

1982-09-01

367

Spectroscopy and planetary atmospheres\\/Spectroscopie et atmosphères planétaires History and future of the molecular spectroscopic databases  

Microsoft Academic Search

A brief history and review of the development of some molecular spectroscopic databases is presented. Such databases are compilations of spectroscopic parameters whose principal purpose is to provide the necessary molecular absorption input for transmission and radiance codes. Remote sensing of the terrestrial atmosphere has advanced significantly in recent years, and this has placed greater demands on the compilations in

Laurence S. Rothman; Nicole Jacquinet-Husson; Christian Boulet; Agnès M. Perrin

368

Observed generation of an atmospheric gravity wave by shear instability in the mean flow of the planetary boundary layer  

Microsoft Academic Search

Observations of a single boundary-layer event — the generation of an atmospheric gravity wave by an unstable shear flow at Haswell, Colorado on November 12, 1971 — are briefly described and discussed. The observations were made using: (a) an acoustic echo sounder, (b) anemometers mounted at two fixed levels on a 150-m tower, (c) an anemometer and a thermometer mounted

W. H. Hooke; F. F. Hall; E. E. Gossard

1973-01-01

369

Dinámica de planetas extrasolares resonantes  

NASA Astrophysics Data System (ADS)

Actualmente se han detectado 117 planetas alrededor de estrellas de Secuencia Principal, incluyendo 12 sistemas planetarios, cada uno con dos o tres miembros. De estos últimos, ocho poseen planetas en órbitas próximas y sus perturbaciones gravitacionales se convierten en un factor fundamental para la estabilidad orbital del sistema. Todos se encuentran en configuraciones resonantes, desde la conmensurabilidad de movimientos 2/1 de Gliese 876, hasta la resonancia secular de Ups And. En esta presentación analizamos varios aspectos de la dinámica resonante de los planetas extrasolares, incluyendo la existencia de soluciones de equilibrio, construcción de modelos analógicos y métodos para la determinación de masas individuales. También discutimos por qué las resonancias son tan frecuentes en estos sistemas, comparado con nuestro propio Sistema Solar. Por último, intentamos relacionar estos modelos con la hipótesis de migración planetaria, buscando límites en su extensión y en los posibles mecanismos que le dieron origen.

Beauge, C.

370

Minimum planetary size for forming outer Jovian-type planets - Stability of an isothermal atmosphere surrounding a protoplanet  

NASA Astrophysics Data System (ADS)

An initial phase in the formation of Jovian planets is a bound hydrostatic atmosphere. When the core mass reaches a critical value, this atmosphere collapses on to the core, and subsequent rapid gas accumulation should form the present massive gas envelope. In the present study, the critical core mass for gas capture is obtained for an isothermal gas. The critical value is proportional to T exp 1.5 whereas its dependence on ambient gas density is very small. The minimum core mass of Jovian planets is reduced to less than 0.2 times the present mass of the earth. The results suggest that Uranus and Neptune might form initially from small gaseous protoplanets.

Sasaki, S.

1989-05-01

371

THE SURVIVAL OF WATER WITHIN EXTRASOLAR MINOR PLANETS  

SciTech Connect

We compute that extrasolar minor planets can retain much of their internal H{sub 2}O during their host star's red giant evolution. The eventual accretion of a water-rich body or bodies onto a helium white dwarf might supply an observable amount of atmospheric hydrogen, as seems likely for GD 362. More generally, if hydrogen pollution in helium white dwarfs typically results from accretion of large parent bodies rather than interstellar gas as previously supposed, then H{sub 2}O probably constitutes at least 10% of the aggregate mass of extrasolar minor planets. One observational test of this possibility is to examine the atmospheres of externally polluted white dwarfs for oxygen in excess of that likely contributed by oxides such as SiO{sub 2}. The relatively high oxygen abundance previously reported in GD 378 can be explained plausibly but not uniquely by accretion of an H{sub 2}O-rich parent body or bodies. Future ultraviolet observations of white dwarf pollutions can serve to investigate the hypothesis that environments with liquid water that are suitable habitats for extremophiles are widespread in the Milky Way.

Jura, M.; Xu, S., E-mail: jura@astro.ucla.ed, E-mail: xsynju@gmail.co [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 (United States)

2010-11-15

372

A Investigation of Low-Frequency Planetary Wave Forcing and Predictability in a Simple Global Atmospheric Circulation Model  

Microsoft Academic Search

Dynamically consistent data generated by a simple 2-level global spectral model are used in conjunction with a diagnostic method to study the forcing of large-scale low-frequency (LF) atmospheric fluctuations. Run in perpetual January mode at moderate spatial resolution (i.e., R15 truncation), the model realistically simulates pertinent features of the observed time-mean climate and variability. The diagnostic method consists of calculating,

Douglas A. Stewart

1992-01-01

373

An investigation of low-frequency planetary wave forcing and predictability in a simple global atmospheric circulation model  

Microsoft Academic Search

Dynamically consistent data generated by a simple 2-level global spectral model are used in conjunction with a diagnostic method to study the forcing of large-scale low-frequency (LF) atmospheric fluctuations. Run in perpetual January mode at moderate spatial resolution (i.e., R15 truncation), the model realistically simulates pertinent features of the observed time-mean climate and variability. The diagnostic method consists of calculating,

Douglas A. Stewart

1992-01-01

374

Thermodynamics and Planetary Habitability  

NASA Astrophysics Data System (ADS)

The relevance of thermodynamics as the driving force for life has long been recognized, for instance by Boltzmann (1886), Lotka (1922) and Schrödinger (1944). Thermodynamics has also been used to characterize planetary habitability. The Earth's atmosphere in a state far from thermodynamic equilibrium, as reflected by its high oxygen content, has been used as an indication for a habitable planet as this state is maintained by the biosphere (Lovelock, 1965). Yet the question remains regarding the fundamental causes that make planet Earth so habitable, or, in other words, what the driving principles are that make the emergence of life an inevitable feature of Earth system functioning. As an extension to these thermodynamic views, I argue here that the myriad of different biogeochemical processes that we call life act to maximize the planetary rate of entropy production. The possibility to do so exists on Earth because its planetary albedo, and therefore the amount of absorbed sunlight and planetary entropy production, is not a fixed planetary property, but emerges from the dynamics of the climate system and the global biogeochemical cycles that shape the composition of the atmosphere. A dominant effect on the planetary albedo is surface temperature: low temperatures result in more highly reflective snow and sea-ice cover, while high temperatures result in an atmosphere with high moisture contents, low temperature gradients, and likely higher reflective cloud cover. Hence, a minimum planetary albedo should exist for a certain, optimum surface temperature at which the absorption of sunlight and the associated rate of entropy production is maximized. Surface temperature, in turn, can be regulated towards the optimum through the intensity of carbon cycling as it directly impacts the strength of the atmospheric greenhouse effect. Hence, a carbon-cycling biosphere can be seen as the biogeochemical implementation to maximize planetary entropy production. This thermodynamic perspective views life as an intrinsic planetary property that is the inevitable consequence of non-equilibrium thermodynamic systems to maximize their rates of entropy production to the extent possible (Kleidon 2004). Planetary habitability can then be related to the flexibility of the planetary boundary conditions, that is, the extent to which these can be altered by internal dynamics. In this presentation, I describe this view in more detail and will outline methods by which this view can be tested quantitatively with numerical simulation models of the Earth system. References Boltzmann, L.: Der zweite Hauptsatz der mechanischen Wärmetheorie. Almanach der kaiserlichen Akademie der Wissenschaften, 36:225-259, 1886. Kleidon, A.: Beyond Gaia: Thermodynamics of life and Earth system functioning. Clim. Ch., 66:271-319, 2004. Lotka, A. J.: Natural Selection as a Physical Principle. Proc. Natl. Acad. Sci. U.S.A., 8:151-154, 1922. Lovelock, J.?aE.: A Physical Basis for Life Detection Experiments. Nature, 207:568- 570, 1965. Schrödinger, E.: What is Life? The physical aspect of the living cell. Cambridge University Press, Cambridge, UK, 1944.

Kleidon, A.

2007-08-01

375

Secular resonance in extrasolar system  

Microsoft Academic Search

The two orbits in the HD 160691 planetary system at first appeared highly unstable, but using a new technique called MEGNO (the acronym of Mean Exponential Growth factor of Nearby Orbits), we were able to identify a stability valley in the parameter space. This stability zone is due to the 2:1 mean motion resonance coupled with relative orbital positions of

N. Rambaux; E. Bois

2003-01-01

376

The Realm of Extrasolar Planets  

Microsoft Academic Search

In November 1995, an article published in Nature [1] put planetary sciences not only as a new hot field in both observational and theoretical astrophysics but also as a topic with a large impact toward the layman. This article was reporting the first discovery of a planet orbiting a star beyond our Sun, namely the solar-type star 51 Pegasi. Nearly

Roger Ferlet

2010-01-01

377

The evolution of comets and the detectability of Extra-Solar Oort Clouds  

SciTech Connect

According the standard theory, comets are natural products of solar system formation, ejected to the Oort Cloud by gravitational scattering events during the epoch of giant planet formation. Stored far from the Sun for billions of years, comets almost certainly contain a record of the events which occurred during (and perhaps even before) the epoch of planetary formation. Two themes are examined of the evolutionary processes that affect comets in the Oort Cloud, and a search for evidence of Extra-Solar Oort Clouds (ESOCs). With regard to cometary evolution in the Oort Cloud, it was found that luminous O stars and supernovae have heated the surface layers of all comets on numerous occasions to 20 to 30 K and perhaps once to 50 K. Interstellar medium (ISM) interactions blow small grains out of the Oort Clouds, and erode the upper few hundred g/cu cm of material from cometary surfaces. The findings presented contradict the standard view that comets do not undergo physical change in the Oort Cloud. A logical consequence of the intimate connection between the Oort Cloud and our planetary system is that the detection of comet clouds around other stars would strongly indicate the sites of extant extra-solar planetary systems. A search was conducted for infrared IR emission from debris in ESOCs. After examining 17 stars using the Infrared Astronomical Satellite data base, only upper limits on ESOC emission could be set.

Stern, S.A.

1989-01-01

378

Planetary geodesy  

Microsoft Academic Search

Research in planetary geodesy in the United States during the period 1975–1978 has benefitted from data obtained by a number of U.S. planetary spacecraft and from some exciting ground-based and aircraft-based observations. Continuing analyses of data from the Mariner 9 orbiter of Mars obtained in 1971 and 1972, the Pioneer 10 and 11 fly-bys of Jupiter in 1973 and 1974,

William H. Michael

1979-01-01

379

Combining Linear and Circular Polarization in Remote Sensing of Cosmic Dust and Planetary Aerosols  

NASA Astrophysics Data System (ADS)

Scattering of light by any type of cosmic dust and planetary aerosols always produces some linear polarization. Its degree and polarization plane are sensitive to the characteristics of the scattering particles, specifically their size, shape and composition. Circular polarization arises from more special conditions, namely, when the scatterers or the scattering medium are characterized by a lack of mirror symmetry. Most common sources of circular polarization are multiple scattering in asymmetric media (e.g. nonspherical nebulae), alignment of elongated dust particles, or their optical activity (circular birefringence and dichroism). The last case is of special interest as optical activity is typical for life-related molecules due to their homochirality, and, thus, circular polarization can indicate presence of biological or pre-biological organics. There are numerous observations of circular polarization, e.g. in molecular clouds and comets, and in the future we may expect to see it when studying the atmospheres of extrasolar planets. In all cases it is important to determine the cause of the circular polarization, specifically to prove or disprove its biological origin. We explore how this can be done by combining linear and circular polarization. Correlations between linear and circular polarization are discussed for cosmic dust and planetary aerosols. The discussion is based on spectral and angular dependence of linear and circular polarizations obtained using computer modeling of light scattering by complex, including optically active, particles and with laboratory measurements of light scattering by biological objects.

Kolokolova, L.; Nagdimunov, L.; Sparks, W.

2012-04-01

380

Adaptive Optics Survey for Companions to stars with Extra-Solar Planets  

SciTech Connect

We have undertaken an adaptive optics imaging survey of extrasolar planetary systems and stars showing interesting radial velocity trends from high precision radial velocity searches. Adaptive Optics increases the resolution and dynamic range of an image, substantially improving the detectability of faint close companions. This survey is sensitive to objects less luminous than the bottom of the main sequence at separations as close as 1 inch. We have detected stellar companions to the planet bearing stars HD 114762 and Tau Boo. We have also detected a companion to the non-planet bearing star 16 Cyg A.

Lloyd, J P; Liu, M C; Graham, J R; Enoch, M; Kalas, P; Marcy, G W; Fischer, D; Patience, J; Macintosh, B; Gavel, D T; Olivier, S S; Max, C E; White, R; Ghez, A M; McLean, I S

2000-11-27

381

An Adaptive Optics Survey for Companions to Stars with Extra-Solar Planets  

SciTech Connect

We have undertaken an adaptive optics imaging survey of extrasolar planetary systems and stars showing interesting radial velocity trends from high precision radial velocity searches. Adaptive Optics increases the resolution and dynamic range of an image, substantially improving the detectability of faint close companions. This survey is sensitive to objects less luminous than the bottom of the main sequence at separations as close as 1 inch. We have detected stellar companions to the planet bearing stars HD 114762 and Tau Boo. We have also detected a companion to the non-planet bearing star 16 Cyg A.

Lloyd, J.P.; Liu, M.C.; Graham, J.R.; Enoch, M.; Kalas, P.; Marcy, G.W.; Fischer, D.; Patience, J.; Macintosh, B.; Gavel, D.T.; Olivier, S.S.; Max, C.E.; White, R.; Ghez, A.M.; McLean, I.S.

2000-11-27

382

Formation of amino acids and nucleic acid constituents from simulated primitive planetary atmospheres by irradiation with high-energy protons  

NASA Astrophysics Data System (ADS)

It is suggested that primitive Earth atmosphere was only slightly reduced, which w as composed of carbon dioxide, carbon monoxide, nitrogen and water. It has been shown that bioorganic compounds can be hardly formed by energies as UV light, heat and spark discharges. We therefore examined possible formation pat hways of bioorganic compounds in the primitive E arth. A mixt ure of carbon monoxide, nitrogen and water was irradiated with high-energy prot ons generated by a van de Graaff accelerator, whi c h simulated an action of cosm ic rays. Aqueous solution of the product was hydr olyzed, and then analyzed by chromatography and mass spectrometry. A wide variety of amino acids and uracil, one of the nucle ic acid bases, wer e identified. Ribose, the RNA sugar, has not been identified, but formation of reducing polyols was suggested. A mino acids and uracil were also formed from a mixture of carbo n dioxide, carbon monoxide, nitrogen and water, and their yields correlated to the ratio of carbon monoxide and nitrogen in the mixture. Since a certain percentage of carbon monoxide could be expected to be in it [1], cosmic radiation can be regarded as an effective energ so urce for prebiotic formation of life's building blocks in they primitive Earth [2]. In the conventional scenario of chemical evolution, amino acids were formed in t he primitive ocean from such intermediates as HCN an d HCHO formed in t he atmosphere. T his scenario seem s not to be possible due to the following reasons: (1) The irradiation products were quit e complex organic com pound s whose molecular weights were ca. 1000, and they gave amino acids after hydrolysis. (2) Energy yields of amino ac ids in the hydrolysates were comparable to those of HCN and HCHO in the irradiation pro duct s. (3) Irradiation products from a mixture of carbon monoxide and nitrogen without water als o gave amino acids aft er hydrolysis. T hes e observations strongly sugge s t e d that complex precursors of bioor ganic com poun ds could be formed directly in the atmosphere. A new scenario of chemical evolution via complex organics toward the origin of life will be prop o s e d. [1] J. Kasting, Origins Life Evol. Biosph ere, 20, 199 (1990). [2] K. Kobay ashi , et al., Origins Life Evol. Biosphere, 28, 155 (1998). * Present address: Rensselaer Polytechnic Ins titut e.

Kobayashi, K.; Yamanashi, H.; Ohashi, A.; Kaneko, T.; Miyakawa, S.; Saito, T.

383

Habitable planet formation in extreme planetary systems: systems with multiple stars and\\/or multiple planets  

Microsoft Academic Search

Understanding the formation and dynamical evolution of habitable planets in extrasolar planetary systems is a challenging task. In this respect, systems with multiple giant planets and\\/or multiple stars present special complications. The formation of habitable planets in these environments is strongly affected by the dynamics of their giant planets and\\/or their stellar companions. These objects have profound effects on the

Nader Haghighipour

2008-01-01

384

Modeling of collision induced absorption spectra of CO2-CO2 pairs for planetary atmosphere of Venus  

NASA Astrophysics Data System (ADS)

The objective of the proposal was to model the rototranslational and rotovibrational collision induced absorption spectral bands of importance for the radiative transfer analysis of the atmosphere of Venus. Our main task has involved CO2 pairs. The approach is not straightforward: whereas computational techniques to compute CIA spectra of small linear molecules exist, and were successfully applied to molecules like H2 or N2, they fail when applied to large molecules like CO2. For small molecules one can safely assume that the interaction potential is isotropic. The same approximation does not work for CO2, and when employed, it gives an incorrect band shape and only 50 percent of the CIA intensity.

Borysow, Aleksandra

1995-03-01

385

Ethane in planetary and cometary atmospheres: Transmittance and fluorescence models of the ?7 band at 3.3 ?m  

NASA Astrophysics Data System (ADS)

Ethane and other hydrocarbon gases have strong rovibrational transitions in the 3.3 ?m spectral region owing to C-H, CH2, and CH3 vibrational modes, making this spectral region prime for searching possible biomarker gases in extraterrestrial atmospheres (e.g., Mars, exoplanets) and organic molecules in comets. However, removing ethane spectral signatures from high-resolution terrestrial transmittance spectra has been imperfect because existing quantum mechanical models have been unable to reproduce the observed spectra with sufficient accuracy. To redress this problem, we constructed a line-by-line model for the ?7 band of ethane (C2H6) and applied it to compute telluric transmittances and cometary fluorescence efficiencies. Our model considers accurate spectral parameters, vibration-rotation interactions, and a functional characterization of the torsional hot band. We integrated the new band model into an advanced radiative transfer code for synthesizing the terrestrial atmosphere (LBLRTM), achieving excellent agreement with transmittance data recorded against Mars using three different instruments located in the Northern and Southern hemispheres. The retrieved ethane abundances demonstrate the strong hemispheric asymmetry noted in prior surveys of volatile hydrocarbons. We also retrieved sensitive limits for the abundance of ethane on Mars. The most critical validation of the model was obtained by comparing simulations of C2H6 fluorescent emission with spectra of three hydrocarbon-rich comets: C/2004 Q2 (Machholz), 8P/Tuttle, and C/2007 W1 (Boattini). The new model accurately describes the complex emission morphology of the ?7 band at low rotational temperatures and greatly increases the confidence of the retrieved production rates (and rotational temperatures) with respect to previously available fluorescence models.

Villanueva, G. L.; Mumma, M. J.; Magee-Sauer, K.

2011-08-01

386

Modelling the high-eccentricity planetary three-body problem. Application to the GJ876 planetary system  

Microsoft Academic Search

The discovery of extrasolar planets located in the vicinity of mean-motion commensurabilities has opened a new arena for the study of resonance capture and its possible role in the dynamical evolution and long-term stability of planetary systems. Contrary to our own Solar System, many of these planets have highly eccentric orbits (~0.1-0.6), making the use of usual analytical perturbative models

C. Beaugé; T. A. Michtchenko

2003-01-01

387

Methane Imaging Search for Planetary Mass Objects in Rho Ophiuchi  

NASA Astrophysics Data System (ADS)

Outside our solar system, T dwarfs have the coldest photospheres that are currently accessible to direct observation. With masses inferred to lie between 10 and 60 times that of Jupiter, these objects represent a class of object linking the properties of observable low mass stars and brown dwarfs with those of unobservable extrasolar planets. Because of their low photospheric temperatures, an understanding of the atmospheres of T dwarfs is likely to yield important clues about the nature of giant planetary atmospheres. The cool atmospheres of T dwarfs are rich in molecular gases, especially methane (CH4). In fact, strong, broad CH4 absorption lines at near-infrared wavelengths represent the distinguishing feature of T dwarfs from hotter objects. Most T dwarfs have been d