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1

The Atmospheres of Extrasolar Planets  

NASA Technical Reports Server (NTRS)

In this chapter we examine what can be learned about extrasolar planet atmospheres by concentrating on a class of planets that transit their parent stars. As discussed in the previous chapter, one way of detecting an extrasolar planet is by observing the drop in stellar intensity as the planet passes in front of the star. A transit represents a special case in which the geometry of the planetary system is such that the planet s orbit is nearly edge-on as seen from Earth. As we will explore, the transiting planets provide opportunities for detailed follow-up observations that allow physical characterization of extrasolar planets, probing their bulk compositions and atmospheres.

Richardson, L. J.; Seager, S.

2007-01-01

2

The Atmospheres of Extrasolar Planets  

E-print Network

The characteristics of irradiated solar system planetary atmospheres have been studied for decades, consequently modern planetary science benefits from an exhaustive body of ground- and space-based data. The study of extrasolar planetary atmospheres, by contrast, is still in its infancy and currently rests on a few score of datapoints, mostly of the transiting planets. This short survey aims not to review this dynamic field but rather stresses the importance of a few theoretical concepts and processes for our understanding of exoplanet atmospheres. Topics covered include atmospheric structure and dynamics, cloud processes and photochemistry of planetary atmospheres. Influences on the albedos, spectra, and colors of extrasolar planets are reviewed and caution is urged in the interpretation of exoplanet colors.

Mark S. Marley

2008-09-26

3

Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Observation, characterization, and understanding the atmospheres of our neighboring planets and moons in the solar system provide essential inputs for addressing broad science goals. These goals include identifying the conditions that are favorable for producing and supporting biological activity, managing the effects of human activity on the Earth's atmosphere, and planning and evaluating observations of extra-solar planets. Here we review the current state of knowledge, pose key science questions, recommend enhancements in the research infrastructure for investigation of planetary atmospheres, and propose new space missions with specific science objectives.

Huestis, D. L.; Adams, N. G.; Atreya, S. K.; Baines, K. H.; Beebe, R. F.; Bolton, S. J.; Bougher, S. W.; Coustenis, A.; Edgington, S. G.; Friedson, A. J.; Galand, M.; Griffith, C. A.; Guberman, S. L.; Hammel, H. B.; Hofstadter, M. D.; Ingersoll, A. P.; Lunine, J. I.; Mendillo, M.; Moses, J.; Mueller-Wodarg, I.; Orton, G. S.; Rages, K. A.; Slanger, T. G.; Titov, D. V.; Vasavada, A. R.; Wong, A.-S.; Yelle, R.

2002-08-01

4

Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

The discovery of planetary systems around alien stars is an outstanding achievement of recent years. The idea that the Solar System may be representative of planetary systems in the Galaxy in general develops upon the knowledge, current until the last decade of the 20th century, that it is the only object of its kind. Studies of the known planets gave rise to a certain stereotype in theoretical research. Therefore, the discovery of exoplanets, which are so different from objects of the Solar System, alters our basic notions concerning the physics and very criteria of normal planets. A substantial factor in the history of the Solar System was the formation of Jupiter. Two waves of meteorite bombardment played an important role in that history. Ultimately there arose a stable low-entropy state of the Solar System, in which Jupiter and the other giants in stable orbits protect the inner planets from impacts by dangerous celestial objects, reducing this danger by many orders of magnitude. There are even variants of the anthropic principle maintaining that life on Earth owes its genesis and development to Jupiter. Some 20 companions more or less similar to Jupiter in mass and a few ``infrared dwarfs,'' have been found among the 500 solar-type stars belonging to the main sequence. Approximately half of the exoplanets discovered are of the ``hot-Jupiter'' type. These are giants, sometimes of a mass several times that of Jupiter, in very low orbits and with periods of 3-14 days. All of their parent stars are enriched with heavy elements, [Fe/H] = 0.1-0.2. This may indicate that the process of exoplanet formation depends on the chemical composition of the protoplanetary disk. The very existence of exoplanets of the hot-Jupiter type considered in the context of new theoretical work comes up against the problem of the formation of Jupiter in its real orbit. All the exoplanets in orbits with a semimajor axis of more than 0.15-0.20 astronomical units (AU) have orbital eccentricities of more than 0.1, in most cases of 0.2-0.5. In conjunction with their possible migration into the inner reaches of the Solar System, this poses a threat to the very existence of the inner planets. Recent observations of gas-dust clouds in very young stars show that hydrogen dissipates rapidly, in several million years, and dissipation is completed earlier than, according to the accretion theory, the gas component of such a planet as Jupiter forms. The mass of the remaining hydrogen is usually small, much smaller than Jupiter's mass. However, the giant planets of the Solar System retain a few percent of the amount of hydrogen that should be contained in the early protoplanetary disk, creating difficulties in understanding their formation. A plausible explanation is that gravitational instabilities in the protoplanetary disk could be the mechanism of their rapid formation.

Ksanfomaliti, L. V.

2000-11-01

5

Stability of motion in extrasolar planetary systems  

Microsoft Academic Search

The discovery of extrasolar planets was and is a big challenge for astronomers because of the very different structure of these systems compared to our Solar System. In some of the extrasolar planetary systems (EPS) we can observe Jupiter-like planets very close to the central star -- even inside Mercury's orbit around the Sun. Many of them -- up to

R. Dvorak

2006-01-01

6

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

7

Dynamical Instabilities in Extrasolar Planetary Systems  

E-print Network

Instabilities and strong dynamical interactions between multiple giant planets have been proposed as a possible explanation for the surprising orbital properties of extrasolar planetary systems. In particular, dynamical instabilities seem to provide a natural mechanism for producing the highly eccentric orbits seen in many systems. Previously, we performed numerical integrations for the dynamical evolution of planetary systems containing two giant planets of equal masses initially in nearly circular orbits very close to the dynamical stability limit. We found the ratio of collisions to ejections in these simulations was greater than the ratio of circular orbits to eccentric orbits among the known extrasolar planets. Further, the mean eccentricity of the planets remaining after an ejection was larger than the mean eccentricity of the known extrasolar planets. Recently, we have performed additional integrations, generalizing to consider two planets of unequal masses. Our new simulations reveal that the two-planet scattering model can produce a distribution of eccentricities consistent with the observed eccentricity distribution for plausible mass distributions. Additionally, this model predicts a maximum eccentricity of about 0.8, in agreement with observations. Early results from simulations of three equal-mass planets also reveal a reduced frequency of collisions and a broad range of final eccentricities for the retained inner planet.

Eric B. Ford; Frederic A. Rasio; Kenneth Yu

2002-10-12

8

Detectability of extrasolar planetary transits  

NASA Technical Reports Server (NTRS)

Precise stellar photometry can be used to detect other planetary systems. However, the intrinsic variability of stellar luminosity imposes a fundamental limit on the sensitivity of this method. Based on recent precise solar observations made from the Solar Maximum Mission satellite, it appears that the detection of earth-sized planets will be marginal during periods of high stellar activity. However, with a suitable photometer larger planets should be readily detectable even in the presence of stellar activity equal to that of the sun at the peak of its sunspot cycle. The high precision, multiple-star photometric system required to detect planets in other stellar systems could be used to monitor flares, starspots, and global oscillations.

Borucki, W. J.; Scargle, J. D.; Hudson, H. S.

1985-01-01

9

Specific Angular Momentum of Extrasolar Planetary Systems  

E-print Network

As the number of known planetary systems increases, the ability to follow-up and characterize the extent of any system becomes limited. This paper considers the use of specific angular momentum as a metric to prioritize future observations. We analyze 431 planets in 367 known extrasolar planetary systems from Butler et al. (2006) (including updates to their online catalog, current to April, 2011) and estimate each system's orbital angular momentum. The range of partition- ing of specific angular momentum in these systems is found to be large, spanning several orders of magnitude. The analysis shows that multi-planet systems tend to have the highest values of specific angular momentum normalized against the planetary masses. This suggests that in high angular momentum systems, the dominant contributors have already been discovered, and that single-planet sys- tems with low observed angular momentum may be the most likely candidates for additional undiscovered companions compared to their high angular momentum, single-planet counterparts. The multi-planet system, GJ 581, is considered as a historical case study to demonstrate the concept, examining how the specific angular momentum of the know planetary system evolved with each discovery.

John C. Armstrong; Shane L. Larson; Rhett R. Zollinger

2007-08-13

10

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

11

Exploring the Diversity of Extrasolar Planet Atmospheres  

NASA Astrophysics Data System (ADS)

The detection and characterization of the atmosphere of a habitable, Earthlike planet is a primary goal in the study of extrasolar planets. Until candidates suitable for such characterization are discovered, observations of larger, hotter, and more massive planets must be used to refine observational techniques and inform exoplanetary atmosphere models, while producing new discoveries exciting in their own right. I will present three new results which challenge our current understanding of more massive extrasolar planets, and represent steps toward characterizing future exo-earths. First, I will present new spectrally resolved observations of the extremely hot Jupiter WASP-12b, which has been claimed to be unusually carbon-rich. Our results, which are also the first to correct WASP-12b's emission for the photometric dilution of a nearby M dwarf, strongly disagree with current carbon-rich models and suggests a nearly isothermal planetary photosphere. Thus detailed compositional analysis will rely on transmission spectroscopy rather than emission measurements. Next, our recent survey of 24 micron thermal phase curves of several other nearby hot Jupiters shows that these planets exhibit strikingly dissimilar recirculation of the incident stellar flux. These different heat redistribution patterns (in spite of the planets' similar equilibrium temperatures) demonstrate the continuing challenge of a robust classification scheme for hot Jupiters. Finally, I will also present first results from our observations of the recently discovered warm Uranus GJ 3470b. This planet's bright host star and deep transit make it the best cool, low-mass planet for detailed atmospheric characterization, and it will quickly become a touchstone object in the study of successively smaller, cooler, and more Earthlike planets.

Crossfield, Ian J.; Hansen, B. M.; Barman, T. S.; Harrington, J.; Knutson, H.; Vican, L.

2013-01-01

12

Detection of planetary spectral features of extrasolar planets through their circumstellar dust - a Monte Carlo simulation  

Microsoft Academic Search

One of the methods envisaged to detect planets outside of our solar system assumes that certain spectral features at 10 and below 20mum wavelength are typical of planetary atmospheres. Their detection would then be an unambiguous sign of the presence of extrasolar planets. In these spectral regions, there might be interference with the silicate and ice features of circumstellar material

O. Fischer; W. Pfau

1997-01-01

13

Dead Zones and Extrasolar Planetary Properties  

E-print Network

Most low-mass protostellar disks evolve in clustered environments where they are affected by external radiation fields, while others evolve in more isolated star-forming regions. Assuming that the magneto-rotational instability (MRI) is the main source of viscosity, we calculate the size of a poorly ionized, MRI inactive, and hence low viscosity region - the "dead zone" - in these protostellar disks. We include disk ionization by X-rays, cosmic rays, radioactive elements and thermal collisions, recombination by molecules, metals, and grains, as well as the effect of turbulence stimulation in the dead zone by the active layers lying above it. We also calculate the gap-opening masses of planets, which are determined by a disk's viscosity and a disk aspect ratio, for disks in these environments and compare them with each other. We find that the dead zone is a robust feature of the protostellar disks that is largely independent of their environment, typically stretching out to ~ 15 AU. We analyze the possible effects of dead zones on planet formation, migration, and eccentricity evolution. We show that the gap-opening mass inside the dead zone is expected to be of the order of terrestrial and ice giant mass planets while that outside the dead zone is Jovian or super-Jovian mass planets, largely independent of the star-forming environment. We show that dead zones can significantly slow down both type I and type II planetary migration due to their lower viscosity. We also find that the growth of eccentricity of massive extrasolar planets is particularly favorable through the planet-disk interaction inside the dead zones due to the large gaps expected to be opened by planets.

Soko Matsumura; Ralph E. Pudritz

2005-09-16

14

Stellar Ablation of Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

We review observations and theories of the solar ablation of planetary atmospheres, focusing on the terrestrial case where a large magnetosphere holds off the solar wind, so that there is little direct atmospheric impact, but also couples the solar wind electromagnetically to the auroral zones. We consider the photothermal escape flows known as the polar wind or refilling flows, the enhanced mass flux escape flows that result from localized solar wind energy dissipation in the auroral zones, and the resultant enhanced neutral atom escape flows. We term these latter two escape flows the "auroral wind." We review observations and theories of the heating and acceleration of auroral winds, including energy inputs from precipitating particles, electromagnetic energy flux at magnetohydrodynamic and plasma wave frequencies, and acceleration by parallel electric fields and by convection pickup processes also known as "centrifugal acceleration." We consider also the global circulation of ionospheric plasmas within the magnetosphere, their participation in magnetospheric disturbances as absorbers of momentum and energy, and their ultimate loss from the magnetosphere into the downstream solar wind, loading reconnection processes that occur at high altitudes near the magnetospheric boundaries. We consider the role of planetary magnetization and the accumulating evidence of stellar ablation of extrasolar planetary atmospheres. Finally, we suggest and discuss future needs for both the theory and observation of the planetary ionospheres and their role in solar wind interactions, to achieve the generality required for a predictive science of the coupling of stellar and planetary atmospheres over the full range of possible conditions.

Moore, Thomas E.; Horwitz, J. L.

2007-01-01

15

Dynamical Instabilities in Extrasolar Planetary Systems Containing Two Giant Planets  

Microsoft Academic Search

Instabilities and strong dynamical interactions between several giant planets have been proposed as a possible explanation for the surprising orbital properties of extrasolar planetary systems. In particular, dynamical instabilities seem to provide a natural mechanism for producing the highly eccentric orbits seen in many systems. Here we present results from a new set of numerical integrations for the dynamical evolution

Eric B. Ford; Marketa Havlickova; Frederic A. Rasio

2001-01-01

16

Planetary Science (mostly atmospheres)  

E-print Network

Planetary Science (mostly atmospheres) at Boston University Paul Withers withers@bu.edu Planetary Science Decadal Survey Town Hall Meeting Boston University 2011.03.26 #12;Selected people Supriya John

Withers, Paul

17

On the dynamics of Trojan planets in extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

In this article we examine the motion of fictitious Trojan planets close to the equilateral Lagrangean equilibrium points in extrasolar planetary systems. Whether there exist stable motion in this area or not depends on the massratio of the primariy bodies in the restricted three body problem, namely the host star and the gasgiant. Taking into account also the eccentricity of the primaries we show via results of extensive numerical integrations that Trojan planets may survive only for e < 0.25. We also show first results of a mapping in the 1:1 resonance with a gas giant on an eccentric orbit which is applied to the extrasolar planetary systems HD 17051. We furthermore study the influence of an additional outer planet which perturbs the motion of the gasgiant as well as the Trojan cloud around its L4 Lagrangean point.

Dvorak, R.; Schwarz, R.; Lhotka, Ch.

2008-05-01

18

Stability Limits in Extrasolar Planetary Systems  

Microsoft Academic Search

Two types of stability boundaries exist for any planetary system consisting of one star and two planets. Lagrange stability requires that the planets remain bound to the star, conserves the ordering of the distance from the star, and limits the variations of orbital elements like semimajor axis and eccentricity. Hill stability only requires that the ordering of the planets remain

Rory Barnes; Richard Greenberg

2006-01-01

19

Stability Limits in Extrasolar Planetary Systems  

Microsoft Academic Search

Two types of stability boundaries exist for any planetary system consisting\\u000aof one star and two planets. Lagrange stability requires that the planets\\u000aremain bound to the star, conserves the ordering of the distance from the star,\\u000aand limits the variations of orbital elements like semi-major axis and\\u000aeccentricity. Hill stability only requires that the ordering of the planets\\u000aremain

Rory Barnes; Richard Greenberg

2006-01-01

20

GMRT Low Frequency Observations of Extrasolar Planetary Systems  

E-print Network

Extrasolar planets are expected to emit detectable low frequency radio emission. In this paper we present results from new low frequency observations of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at 150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have been chosen because the stars are young (with ages < 1 Gyr) and are likely to have strong stellar winds, which will increase the expected radio flux. The planets are massive (presumably) gas giant planets in longer period orbits, and hence will not be tidally locked to their host star (as is likely to be the case for short period planets) and we would expect them to have a strong planetary dynamo and magnetic field. We do not detect either system, but are able to place tight upper limits on their low frequency radio emission, at levels comparable to the theoretical predictions for these systems. From these observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy for HD 128311. In addition, these upper limits also provide limits on the low frequency radio emission from the stars themselves. These results are discussed and also the prospects for the future detection of radio emission from extrasolar planets.

Samuel George; Ian Stevens

2007-08-30

21

Effects of Secular Interactions in Extrasolar Planetary Systems  

E-print Network

This paper studies the effects of dynamical interactions among the planets in observed extrasolar planetary systems, including hypothetical additional bodies, with a focus on secular perturbations. These interactions cause the eccentricities of the planets to explore a distribution of values over time scales that are long compared to observational time baselines, but short compared to the age of the systems. The same formalism determines the eccentricity forcing of hypothetical test bodies (terrestrial planets) in these systems and we find which systems allow for potentially habitable planets. Such planets would be driven to nonzero orbital eccentricity and we derive the distribution of stellar flux experienced by the planets over the course of their orbits. The general relativistic corrections to secular interaction theory are included in the analysis and such effects are important in systems with close planets ($\\sim$4 day orbits). Some extrasolar planetary systems (e.g., Upsilon Andromedae) can be used as a test of general relativity, whereas in other systems, general relativity can be used to constrain the system parameters (e.g., $\\sin i \\gta 0.93$ for HD160691). For the case of hot Jupiters, we discuss how the absence of observed eccentricity implies the absence of companion planets.

Fred C. Adams; Gregory Laughlin

2006-06-14

22

Comparative Planetary Atmospheres  

E-print Network

. All of the planets orbit the Sun in the same sense 4. Planets spin in the same sense as their orbits Ã? solar for Jupiter to ~40 Ã? solar for Neptune 8. Separation between planet orbits increases with distanceComparative Planetary Atmospheres 1. Formation and evolution of planets and atmospheres Prof FW

Read, Peter L.

23

Space Science I: Planetary Atmospheres  

E-print Network

Space Science I: Planetary Atmospheres Atmospheric Structure and Transport Origins and Evolution of Planetary Atmospheres Books The New Solar System Chapters 8,9,11,13,15,17,18,20 #12;Space Science I, is crucial and is one goal of this course. #12;Space Science I: Planetary Atmospheres Goals To understand- 1

Johnson, Robert E.

24

Predicting the Atmospheric Composition of Extrasolar Giant Planets  

NASA Technical Reports Server (NTRS)

To date, approximately 120 planet-sized objects have been discovered around other stars, mostly through the radial-velocity technique. This technique can provide information about a planet s minimum mass and its orbital period and distance; however, few other planetary data can be obtained at this point in time unless we are fortunate enough to find an extrasolar giant planet that transits its parent star (i.e., the orbit is edge-on as seen from Earth). In that situation, many physical properties of the planet and its parent star can be determined, including some compositional information. Our prospects of directly obtaining spectra from extrasolar planets may improve in the near future, through missions like NASA's Terrestrial Planet Finder. Most of the extrasolar giant planets (EGPs) discovered so far have masses equal to or greater than Jupiter's mass, and roughly 16% have orbital radii less than 0.1 AU - extremely close to the parent star by our own Solar-System standards (note that Mercury is located at a mean distance of 0.39 AU and Jupiter at 5.2 AU from the Sun). Although all EGPs are expected to have hydrogen-dominated atmospheres similar to Jupiter, the orbital distance can strongly affect the planet's temperature, physical, chemical, and spectral properties, and the abundance of minor, detectable atmospheric constituents. Thermochemical equilibrium models can provide good zero-order predictions for the atmospheric composition of EGPs. However, both the composition and spectral properties will depend in large part on disequilibrium processes like photochemistry, chemical kinetics, atmospheric transport, and haze formation. We have developed a photochemical kinetics, radiative transfer, and 1-D vertical transport model to study the atmospheric composition of EGPs. The chemical reaction list contains H-, C-, O-, and N-bearing species and is designed to be valid for atmospheric temperatures ranging from 100-3000 K and pressures up to 50 bar. Here we examine the effect of stellar distance (e.g., incident ultraviolet flux, atmospheric temperature) on the chemical properties of EGPs. The model is applied to two generic Class II and III intermediate temperature EGPs located at 3.3 and 0.27 AU from a solar-like parent star, and the results are compared with a model for Jupiter at 5.2 AU.

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

2004-01-01

25

Exploring Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The past decade has been an exciting time to study atmospheres. Fundamental studies of Earth's general circulation and hydrological cycle have been stimulated by questions about past climates and the future impacts of humankind's activities. Long-term spacecraft and Earth-based observations of solar system planets have reinvigorated the study of comparative planetary climatology. The explosion in discoveries of planets outside our solar system has made atmospheric science integral to understanding the diversity of our solar system and the potential habitability of planets outside it. Thus, the AGU Chapman Conference: Crossing the Boundaries in Planetary Atmospheres—From Earth to Exoplanets, gathered Earth, solar system, and exoplanet scientists to share experiences, insights, and challenges from their individual disciplines and to discuss areas in which thinking broadly might enhance scientists' fundamental understanding of how atmospheres work.

Simon-Miller, Amy A.; Del Genio, Anthony D.

2013-11-01

26

Dynamics of planetary atmospheres  

E-print Network

Dynamics of planetary atmospheres Gas Giant Planets (Jupiter, Saturn, Uranus, Neptune) #12;Gas (Earth yrs) 9.55.2Mean distance to Sun (AU) SaturnJupiter #12;Interiors of Gas Giants From Guillot (1999 h Adz zB zT " #12;Vorticity equation ! "# "t + u "# "x + v "# "y $ (2%+ #) "w "z = 0 " ( # "t + ( u

Read, Peter L.

27

A grid of polarization models for Rayleigh scattering planetary atmospheres  

E-print Network

We investigate the intensity and polarization of reflected light from planetary atmospheres. We present a large grid of Monte Carlo simulations for planets with Rayleigh scattering atmospheres. We discuss the disk-integrated polarization for phase angles typical of extrasolar planet observations and for the limb polarization effect observable for solar system objects near opposition. The main parameters investigated are single scattering albedo, optical depth of the scattering layer, and albedo of an underlying Lambert surface for a homogeneous Rayleigh scattering atmosphere. We also investigate atmospheres with isotropic scattering and forward scattering aerosol particles, as well as models with two scattering layers. The model grid provides a tool for extracting quantitative results from polarimetric measurements of planetary atmospheres from solar system planets and extrasolar planets, in particular on the scattering properties and stratification of particles in the highest atmosphere layers. Spectropolari...

Buenzli, Esther

2009-01-01

28

Predicting Planets in Known Extrasolar Planetary Systems. III. Forming Terrestrial Planets  

Microsoft Academic Search

Recent results have shown that many of the known extrasolar planetary systems contain regions that are stable for both Earth-mass and Saturn-mass planets. Here we simulate the formation of terrestrial planets in four planetary systems, 55 Cancri, HD 38529, HD 37124, and HD 74156, under the assumption that these systems of giant planets are complete and that their orbits are

Sean N. Raymond; Rory Barnes; Nathan A. Kaib

2006-01-01

29

PICTURE: a sounding rocket experiment for direct imaging of an extrasolar planetary environment  

E-print Network

PICTURE: a sounding rocket experiment for direct imaging of an extrasolar planetary environment 90278, USA ABSTRACT The Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE 36.225 UG.5 AU. PICTURE carried four key enabling technologies on board a NASA sounding rocket at 4:25 MDT

30

Cryptic photosynthesis, Extrasolar planetary oxygen without a surface biological signature  

E-print Network

On the Earth, photosynthetic organisms are responsible for the production of virtually all of the oxygen in the atmosphere. On the land, vegetation reflects in the visible, leading to a red edge that developed about 450 Myr ago and has been proposed as a biosignature for life on extrasolar planets. However, in many regions of the Earth, and particularly where surface conditions are extreme, for example in hot and cold deserts, 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 metres depth in water bodies. These communities are widespread and dominate local photosynthetic productivity. We review known cryptic photosynthetic communities and their productivity. We link 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-analogs that show detectable atmospheric biomarkers like our own planet, but do not exhibit a discernable biological surface feature in the disc-averaged spectrum.

C. S. Cockell; L. Kaltenegger; J. A. Raven

2008-09-23

31

IUE observations of planetary atmospheres  

Microsoft Academic Search

The UV observations of planetary atmospheres were used to study the upper parts of the atmospheres, below and above the homopause. The IUE observations significantly contribute to knowledge of the aeronomy and photochemistry of planetary atmospheres. On Venus, SO2 is detected; ozone is observed on Mars; C2H2 and NH3 are detected in the Jovian upper atmosphere; acetylene is detected also

Therese Encrenaz

1988-01-01

32

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

33

Predicting Planets in Known ExtraSolar Planetary Systems III: Forming Terrestrial Planets  

Microsoft Academic Search

Recent results have shown that many of the known extrasolar planetary systems\\u000acontain regions which are stable for both Earth-mass and Saturn-mass planets.\\u000aHere we simulate the formation of terrestrial planets in four planetary systems\\u000a-- 55 Cancri, HD 38529, HD 37124, and HD 74156 -- under the assumption that\\u000athese systems of giant planets are complete and that their

Sean N. Raymond; Rory Barnes; Nathan A. Kaib

2004-01-01

34

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

35

Stability of Earth-Mass Planets in the Habitable Zones of Extrasolar Planetary Systems  

E-print Network

Kumar Kopparapu Dept. of Geosciences, College of Earth and Mineral Science Over 500 planets orbiting be influenced by the remaining companions in the system. Just like Jupiter affects the orbits of planets in our solar system, giant planets in extrasolar planetary systems also influence the orbits of Earth

Bjørnstad, Ottar Nordal

36

PREDICTING PLANETS IN KNOWN EXTRASOLAR PLANETARY SYSTEMS. III. FORMING TERRESTRIAL PLANETS  

E-print Network

that these systems of giant planets are complete and that their orbits are well determined. Assuming that the giantPREDICTING PLANETS IN KNOWN EXTRASOLAR PLANETARY SYSTEMS. III. FORMING TERRESTRIAL PLANETS Sean N that are stable for both Earth-mass and Saturn-mass planets. Here we simulate the formation of terrestrial planets

Barnes, Rory

37

Characterization of Extrasolar Planets: Lessons From Atmospheres Modeling  

NASA Astrophysics Data System (ADS)

When the landmark of the first direct detection of an extrasolar planet is achieved, the next task will be to characterize the object. The goals of characterization will include determination of the mass, radius, composition, and atmospheric structure of the planet. Evolution and atmospheric models will be required to guide the observations and interpret the data. Given this situation, one might reasonably inquire about the veracity of the models and how well they can be applied in practice to cool atmospheres. In my review I will explore the history of atmospheric modeling and discuss the track record of models in the solar system. Some brown dwarfs are already known to be cooler than hot, young Jupiters and provide further testing grounds for the models. I'll consider the remaining uncertainties, especially regarding cloud modeling, and will focus the key issues expected to be faced in the early characterization of extrasolar planets.

Marley, M.

2007-06-01

38

Energetics of planetary upper atmospheres  

Microsoft Academic Search

One of the fundamental questions in aeronomy is that of energy balance. What are the sources of energy incident upon an atmosphere, how is this energy redistributed internally and how much of it is lost into space? These questions are key to understanding planetary atmospheres, and we address them by comparing different planets and moons with atmospheres, as opposed to

I. C. Mueller-Wodarg; R. V. Yelle; M. Mendillo; M. Galand

2006-01-01

39

Dynamics of Extrasolar Planetary Systems: 2\\/1 Resonant Motion  

Microsoft Academic Search

A systematic study of the dynamics of resonant planetary systems is made, based on the existence and stability character of families of periodic orbits of the planetary type. In the present study we consider planetary systems with two planets, moving in the same plane. We explore the whole phase space close to the 2\\/1 resonance, for the masses of the

John D. Hadjidemetriou; Dionyssia Psychoyos

2003-01-01

40

Is the HR8799 extrasolar system destined for planetary scattering?  

Microsoft Academic Search

The recent discovery of a three-planet extrasolar system of HR8799 by Marois et al. is a breakthrough in the field of the direct imaging. This great achievement raises questions on the formation and dynamical stability of the system, because Keplerian fits to astrometric data disrupt during ~0.2Myr. We search for stable, self-consistent N-body orbits with the so-called GAMP (genetic algorithm

Krzysztof Gozdziewski; Cezary Migaszewski

2009-01-01

41

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

42

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

43

A New Hypothesis On The Origin and Formation of The Solar And Extrasolar Planetary Systems  

E-print Network

A new theoretical hypothesis on the origin and formation of the solar and extrasolar planetary systems is summarized and briefly discussed in the light of recent detections of extrasolar planets, and studies of shock wave interaction with molecular clouds, as well as H. Alfven's work on Sun's magnetic field and its effect on the formation of the solar system (1962). We propose that all objects in a planetary system originate from a small group of dense fragments in a giant molecular cloud (GMC). The mechanism of one or more shock waves, which propagate through the protoplanetary disk during the star formation is necessary to trigger rapid cascade fragmentation of dense clumps which in turn collapse quickly, simultaneously, and individually to form multi-planet and multi-satellite systems. Magnetic spin resonance may be the cause of the rotational directions of newly formed planets to couple and align in the strong magnetic field of a younger star.

Yao, Lihong

2014-01-01

44

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

Microsoft Academic Search

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

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

2011-01-01

45

Clouds in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

In the terrestrial atmosphere clouds are familiar as vast collections of small water drops or ice cyrstals suspended in the air. The study of clouds touches on many facets of armospheric science. The chemistry of clouds is tied to the chemistry of the surrounding atmosphere.

West, R.

1999-01-01

46

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

47

Can The Periods of Some Extra-Solar Planetary Systems be Quantized?  

NASA Astrophysics Data System (ADS)

A simple formula was derived before by Morcos (2013 ), to relate the quantum numbers of planetary systems and their periods. This formula is applicable perfectly for the solar system planets, and some extra-solar planets , of stars of approximately the same masses like the Sun. This formula has been used to estimate the periods of some extra-solar planet of known quantum numbers. The used quantum numbers were calculated previously by other authors. A comparison between the observed and estimated periods, from the given formula has been done. The differences between the observed and calculated periods for the extra-solar systems have been calculated and tabulated. It is found that there is an error of the range of 10% The same formula has been also used to find the quantum numbers, of some known periods, exo-planet. Keywords: Quantization; Periods; Extra-Planetary; Extra-Solar Planet REFERENCES [1] Agnese, A. G. and Festa, R. “Discretization on the Cosmic Scale Inspirred from the Old Quantum Mechanics,” 1998. http://arxiv.org/abs/astro-ph/9807186 [2] Agnese, A. G. and Festa, R. “Discretizing ups-Andro- medae Planetary System,” 1999. http://arxiv.org/abs/astro-ph/9910534. [3] Barnothy, J. M. “The Stability of the Solar Systemand of Small Stellar Systems,” Proceedings of the IAU Sympo-sium 62, Warsaw, 5-8 September 1973, pp. 23-31. [4] Morcos, A.B. , “Confrontation between Quantized Periods of Some Extra-Solar Planetary Systems and Observations”, International Journal of Astronomy and Astrophysics, 2013, 3, 28-32. [5] Nottale, L. “Fractal Space-Time and Microphysics, To-wards a Theory of Scale Relativity,” World Scientific, London, 1994. [6] Nottale , L., “Scale-Relativity and Quantization of Extra- Solar Planetary Systems,” Astronomy & Astrophysics, Vol. 315, 1996, pp. L9-L12 [7] Nottale, L., Schumacher, G. and Gay, J. “Scale-Relativity and Quantization of the Solar Systems,” Astronomy & Astrophysics letters, Vol. 322, 1997, pp. 1018-10 [8]Nottale, L. “Scale-Relativity and Quantization of Exo- planet Orbital Semi-Major Axes,” Astronomy & Astro- physics, Vol. 361, 2000, pp. 379-387.

El Fady Morcos, Abd

48

PASCAL - Planetary Atmospheres Spectral Catalog  

NASA Astrophysics Data System (ADS)

Spectroscopic observation of planetary atmospheres, stellar atmospheres, comets, and the interstellar medium is the most powerful tool for extracting detailed information concerning the properties of these objects. The HITRAN molecular spectroscopic database1 has traditionally served researchers involved with terrestrial atmospheric problems, such as remote-sensing of constituents in the atmosphere, pollution monitoring at the surface, identification of sources seen through the atmosphere, and numerous environmental issues. A new thrust of the HITRAN program is to extend this longstanding database to have capabilities for studying the above-mentioned planetary and astronomical systems. The new extension is called PASCAL (Planetary Atmospheres Spectral Catalog). The methodology and structure are basically identical to the construction of the HITRAN and HITEMP databases. We will acquire and assemble spectroscopic parameters for gases and spectral bands of molecules that are germane to the studies of planetary atmospheres. These parameters include the types of data that have already been considered for transmission and radiance algorithms, such as line position, intensity, broadening coefficients, lower-state energies, and temperature dependence values. Additional parameters beyond what is currently considered for the terrestrial atmosphere will be archived. Examples are collision-broadened halfwidths due to various foreign partners, collision-induced absorption, and temperature dependence factors. New molecules (and their isotopic variants), not currently included in the HITRAN database, will be incorporated. That includes hydrocarbons found on Titan but not archived in HITRAN (such as C3H4, C4H2, C3H8). Other examples include sulfur-bearing molecules such as SO and CS. A further consideration will be spectral bands that arise as opportunities to study exosolar planets. The task involves acquiring the best high-resolution data, both experimental and theoretical, covering a wide spectral range from the microwave through ultraviolet. The data are frequently from multiple sources and must be merged, with special attention to the unique quantum identification of each transition. The resultant line lists are then validated and incorporated into a structured database that is easily employed by modelers. Partition sums that are necessary for applications at a wide range of temperature will also be generated. For molecules with dense spectra, especially molecules with many low-lying fundamental vibrations, the approach is to cast them into sets of pressure-temperature absorption cross-section files. In this case, we will acquire the best laboratory measurements of these gases and transform them into the standard reference files for use in the radiative-transfer codes. This effort is supported by the NASA Planetary Atmospheres program, under the grant NNX10AB94G.

Rothman, Laurence; Gordon, Iouli

2010-05-01

49

An extrasolar planetary system with three Neptune-mass planets  

E-print Network

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.

C. Lovis; M. Mayor; F. Pepe; Y. Alibert; W. Benz; F. Bouchy; A. C. M. Correia; J. Laskar; C. Mordasini; D. Queloz; N. C. Santos; S. Udry; J. -L. Bertaux; J. -P. Sivan

2007-03-01

50

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

51

Radial Velocity Detection of Extra-Solar Planetary Systems  

NASA Technical Reports Server (NTRS)

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 2dcoude spectrometer, 2) A high-precision radial-velocity survey of Hyades dwarfs, using the Keck telescope and its HIRES spectrograph, 3) A program at McDonald Observatory to obtain spectra of the parent stars of planetary systems at R = 210,000, and 4) the start of high precision radial velocity surveys using the Hobby-Eberly Telescope. The most important results from NASA support of these research programs are described. A list of all papers published under support of this grant is included at the end.

Cochran, William D.

2004-01-01

52

Radial Velocity Detection of Extra-Solar Planetary Systems  

NASA Technical Reports Server (NTRS)

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 spectrometer, 2) A high-precision radial-velocity survey of Hyades dwarfs, using the Keck telescope and its HIRES spectrograph, 3) A program at McDonald Observatory to obtain spectra of the parent stars of planetary systems at R = 210,000, and 4) the start of high precision radial velocity surveys using the Hobby-Eberly Telescope. The most important results from NASA support of these research programs are described below. A list of all papers published under support of this grant is included at the end.

Cochran, William D.

2004-01-01

53

The Rossiter-McLaughlin effect and analytic radial velocity curves for transiting extrasolar planetary systems  

E-print Network

A transiting extrasolar planet sequentially blocks off the light coming from the different parts of the disk of the host star in a time dependent manner. Due to the spin of the star, this produces an asymmetric distortion in the line profiles of the stellar spectrum, leading to an apparent anomaly of the radial velocity curves, known as the Rossiter - McLaughlin effect. Here, we derive approximate but accurate analytic formulae for the anomaly of radial velocity curves taking account of the stellar limb darkening. The formulae are particularly useful in extracting information of the projected angle between the planetary orbit axis and the stellar spin axis, \\lambda, and the projected stellar spin velocity, V sin I_s. We create mock samples for the radial curves for the transiting extrasolar system HD209458, and demonstrate that constraints on the spin parameters (V sin I_s, \\lambda) may be significantly improved by combining our analytic template formulae and the precision velocity curves from high-resolution spectroscopic observations with 8-10 m class telescopes. Thus future observational exploration of transiting systems using the Rossiter - McLaughlin effect is one of the most important probes to better understanding of the origin of extrasolar planetary systems, especially the origin of their angular momentum.

Yasuhiro Ohta; Atsushi Taruya; Yasushi Suto

2004-10-21

54

PLANETARY MIGRATION AND ECCENTRICITY AND INCLINATION RESONANCES IN EXTRASOLAR PLANETARY SYSTEMS  

SciTech Connect

The differential migration of two planets due to planet-disk interaction can result in capture into the 2:1 eccentricity-type mean-motion resonances. Both the sequence of 2:1 eccentricity resonances that the system is driven through by continued migration and the possibility of a subsequent capture into the 4:2 inclination resonances are sensitive to the migration rate within the range expected for type II migration due to planet-disk interaction. If the migration rate is fast, the resonant pair can evolve into a family of 2:1 eccentricity resonances different from those found by Lee. This new family has outer orbital eccentricity e {sub 2} {approx}> 0.4-0.5, asymmetric librations of both eccentricity resonance variables, and orbits that intersect if they are exactly coplanar. Although this family exists for an inner-to-outer planet mass ratio m {sub 1}/m {sub 2} {approx}> 0.2, it is possible to evolve into this family by fast migration only for m {sub 1}/m {sub 2} {approx}> 2. Thommes and Lissauer have found that a capture into the 4:2 inclination resonances is possible only for m {sub 1}/m {sub 2} {approx}< 2. We show that this capture is also possible for m {sub 1}/m {sub 2} {approx}> 2 if the migration rate is slightly slower than that adopted by Thommes and Lissauer. There is significant theoretical uncertainty in both the sign and the magnitude of the net effect of planet-disk interaction on the orbital eccentricity of a planet. If the eccentricity is damped on a timescale comparable to or shorter than the migration timescale, e {sub 2} may not be able to reach the values needed to enter either the new 2:1 eccentricity resonances or the 4:2 inclination resonances. Thus, if future observations of extrasolar planetary systems were to reveal certain combinations of mass ratio and resonant configuration, they would place a constraint on the strength of eccentricity damping during migration, as well as on the rate of the migration itself.

Lee, Man Hoi [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Thommes, Edward W. [Department of Physics, University of Guelph, Guelph, ON N1G 2W1 (Canada)], E-mail: mhlee@hku.hk, E-mail: ethommes@physics.uoguelph.ca

2009-09-10

55

The chemical diversity of extra-solar planetary systems  

NASA Astrophysics Data System (ADS)

Over the past few years, it has become increasingly clear that the most plausible scenario to explain the infrared excess observed at 30 white dwarfs is accretion from rocky planetary material - suggesting that these white dwarfs may have had, or may still have terrestial planets as well. This hypothesis is corroborated through the detection of volatile-depleted abundance patterns in the photospheres of these white dwarfs. We are carrying out a large COS snapshot survey of 150 white dwarfs, with the aim to determine the fraction of remnants of planetary systems around young {20-200Myr} white dwarfs. At the time of writing, we have observed 94 white dwarfs, and find pollution by Si, one of the major constituents of the Earth, in 25% of them. In about a dozen stars, we detect multiple {up to nine} different elements, and show that their abundance pattern is broadly consistent with that of bulk-Earth: extremely volatile depleted, in particular in C/Si. However, there are two exceptions: WD1013+256 and WD1647+375 show strong lines of both Si and C. We have ruled out accretion from the wind of a nearby low-mass companion, and the only explanation is accretion of planetary debris that is significantly richer in C than the bulk Earth. This discovery is of substantial significance within the current discussion on variations in the exo-planet chemistry. We propose to re-observe these two white dwarfs, doubling the signal-to-noise ratio with respect to our very short Snapshot spectra, to and to determine the abundances of additional elements, including Fe, O, and possibly Ni and N.

Gaensicke, Boris

2012-10-01

56

Water vapour in the atmosphere of a transiting extrasolar planet  

E-print Network

Water is predicted to be among, 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 an exoplanet, but have 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 HD189733b taken during the transit, where 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, 5.8 and 8 microns. The larger effective radius observed at visible wavelengths may be due to either star variability or the presence of clouds/hazes. We explain the most recent thermal infrared observations of the planet during secondary transit behind the star, reporting a non-detection of water on HD189733b, as being a consequence of the nearly isothermal vertical profile of the planet.s atmosphere. Our results show that water is detectable on extrasolar planets using the primary transit technique and that the infrared should be a better wavelength region than the visible, for such searches.

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

2007-07-20

57

Extrasolar planetary dynamics with a generalized planar Laplace-Lagrange secular theory  

E-print Network

The dynamical evolution of nearly half of the known extrasolar planets in multiple-planet systems may be dominated by secular perturbations. The commonly high eccentricities of the planetary orbits calls into question the utility of the traditional Laplace-Lagrange (LL) secular theory in analyses of the motion. We analytically generalize this theory to fourth-order in the eccentricities, compare the result with the second-order theory and octupole-level theory, and apply these theories to the likely secularly-dominated HD 12661, HD 168443, HD 38529 and Ups And multi-planet systems. The fourth-order scheme yields a multiply-branched criterion for maintaining apsidal libration, and implies that the apsidal rate of a small body is a function of its initial eccentricity, dependencies which are absent from the traditional theory. Numerical results indicate that the primary difference the second and fourth-order theories reveal is an alteration in secular periodicities, and to a smaller extent amplitudes of the planetary eccentricity variation. Comparison with numerical integrations indicates that the improvement afforded by the fourth-order theory over the second-order theory sometimes dwarfs the improvement needed to reproduce the actual dynamical evolution. We conclude that LL secular theory, to any order, generally represents a poor barometer for predicting secular dynamics in extrasolar planetary systems, but does embody a useful tool for extracting an accurate long-term dynamical description of systems with small bodies and/or near-circular orbits.

Dimitri Veras; Philip J. Armitage

2007-03-05

58

Planetary targets in the search for extrasolar oxygenic photosynthesis  

Microsoft Academic Search

Background: In the coming decades space telescopes will be constructed that will attempt to find the gaseous products of oxygenic photosynthesis, the most promising biosignatures of life, in the atmospheres of temperate Earth-like planets orbiting distant stars.Aims: This paper aims to provide a synthesis of the range of feasible targets – either planets or their satellites – that could harbour

Charles S. Cockell; John A. Raven; Lisa Kaltenegger; Roberta C. Logan

2009-01-01

59

The HARPS search for southern extra-solar planets: XXVI: Seven new planetary systems  

Microsoft Academic Search

We are conducting a planet search survey with HARPS since seven years. The\\u000avolume-limited stellar sample includes all F2 to M0 main-sequence stars within\\u000a57.5 pc, where extrasolar planetary signatures are systematically searched for\\u000awith the radial-velocity technics. In this paper, we report the discovery of\\u000anew substellar companions of seven main-sequence stars and one giant star,\\u000adetected through multiple

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

2010-01-01

60

The Role of Carbon in Extrasolar Planetary Geodynamics and Habitability  

NASA Astrophysics Data System (ADS)

The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ~3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

Unterborn, Cayman T.; Kabbes, Jason E.; Pigott, Jeffrey S.; Reaman, Daniel M.; Panero, Wendy R.

2014-10-01

61

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets. I. The Role of Electron Avalanche  

Microsoft Academic Search

Brown dwarf and extrasolar planet atmospheres form clouds which strongly influence the local chemistry and physics. These clouds are globally neutral obeying dust-gas charge equilibrium which is, on short timescales, inconsistent with the observation of stochastic ionization events of the solar system planets. We argue that a significant volume of the clouds in brown dwarfs and extrasolar planets is susceptible

Ch. Helling; M. Jardine; S. Witte; D. A. Diver

2011-01-01

62

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

63

NASA's Planetary Astronomy and Planetary Atmospheres Programs - A Snapshot  

Microsoft Academic Search

I am considering establishing two standing Review Committees with staggered two-year appointments for the Planetary Astronomy (PAST) and Planetary Atmospheres (PATM) Programs. These committees are being formed to solicit membership and Chair the annual review processes in these two program areas. Initially the PAST Review Committee will consist of 4 to 5 members, an overall chairperson and 3 to 4

J. J. Hillman

2001-01-01

64

Rapid heating of the atmosphere of an extrasolar planet.  

PubMed

Near-infrared observations of more than a dozen 'hot-Jupiter' extrasolar planets have now been reported. These planets display a wide diversity of properties, yet all are believed to have had their spin periods tidally spin-synchronized with their orbital periods, resulting in permanent star-facing hemispheres and surface flow patterns that are most likely in equilibrium. Planets in significantly eccentric orbits can enable direct measurements of global heating that are largely independent of the details of the hydrodynamic flow. Here we report 8-microm photometric observations of the planet HD 80606b during a 30-hour interval bracketing the periastron passage of its extremely eccentric 111.4-day orbit. As the planet received its strongest irradiation (828 times larger than the flux received at apastron) its maximum 8-microm brightness temperature increased from approximately 800 K to approximately 1,500 K over a six-hour period. We also detected a secondary eclipse for the planet, which implies an orbital inclination of i approximately 90 degrees , fixes the planetary mass at four times the mass of Jupiter, and constrains the planet's tidal luminosity. Our measurement of the global heating rate indicates that the radiative time constant at the planet's 8-microm photosphere is approximately 4.5 h, in comparison with 3-5 days in Earth's stratosphere. PMID:19177124

Laughlin, Gregory; Deming, Drake; Langton, Jonathan; Kasen, Daniel; Vogt, Steve; Butler, Paul; Rivera, Eugenio; Meschiari, Stefano

2009-01-29

65

The role of planetary formation and evolution in shaping the composition of exoplanetary atmospheres  

NASA Astrophysics Data System (ADS)

Over the last twenty years, the search for extrasolar planets has revealed the rich diversity of outcomes from the formation and evolution of planetary systems. In order to fully understand how these extrasolar planets came to be, however, the orbital and physical data we possess are not enough, and they need to be complemented with information about the composition of the exoplanets. Ground-based and space-based observations provided the first data on the atmospheric composition of a few extrasolar planets, but a larger and more detailed sample is required before we can fully take advantage of it. The primary goal of a dedicated space mission like the Exoplanet Characterization Observatory (EChO) proposal is to fill this gap and to expand the limited data we possess by performing a systematic survey of extrasolar planets. The full exploitation of the data that space-based and ground-based facilities will provide in the near future, however, requires knowledge about the sources and sinks of the chemical species and molecules that will be observed. Luckily, the study of the past history of the Solar System provides several indications about the effects of processes like migration, late accretion and secular impacts, and on the time they occur in the life of planetary systems. In this work we will review what is already known about the factors influencing the composition of planetary atmospheres, focusing on the case of gaseous giant planets, and what instead still need to be investigated.

Turrini, D.; Nelson, R. P.; Barbieri, M.

2014-07-01

66

Review of methodology and technology available for the detection of extrasolar planetary systems.  

PubMed

Anyone undertaking an interstellar voyage might wish to be assured of the existence of a safe planetary harbor at the other end! Aside from the obvious interest of the participants in this Symposium, astronomers and astrophysicists are also eager to detect and study other planetary systems in order to better understand the formation of our own Solar System. Scientists involved in the search for extraterrestrial intelligence argue that planets suitable for the evolution of life may abound elsewhere within our own Milky Way Galaxy. On theoretical grounds, they are probably correct, but they lack any observational support. For in spite of decades of claimed astrometric detections of planetary companions and the recent exciting and tantalizing observations from the IRAS satellite and the IR speckle observations of Van Biesbroeck 8 and other cool stars, there is no unambiguous proof for the existence of another planetary system beyond our own. In this paper we review the various methods for detecting extrasolar planets and briefly describe the Earth and space based technology currently available and discuss the near-term plans to implement these different search techniques. In each case an attempt is made to identify the limiting source of systematic error inherent to the methodology and to assess the potential for technological improvements. PMID:11539063

Tarter, J C; Black, D C; Billingham, J

1986-01-01

67

Review of methodology and technology available for the detection of extrasolar planetary systems  

NASA Technical Reports Server (NTRS)

Anyone undertaking an interstellar voyage might wish to be assured of the existence of a safe planetary harbor at the other end! Aside from the obvious interest of the participants in this Symposium, astronomers and astrophysicists are also eager to detect and study other planetary systems in order to better understand the formation of our own Solar System. Scientists involved in the search for extraterrestrial intelligence argue that planets suitable for the evolution of life may abound elsewhere within our own Milky Way Galaxy. On theoretical grounds, they are probably correct, but they lack any observational support. For in spite of decades of claimed astrometric detections of planetary companions and the recent exciting and tantalizing observations from the IRAS satellite and the IR speckle observations of Van Biesbroeck 8 and other cool stars, there is no unambiguous proof for the existence of another planetary system beyond our own. In this paper we review the various methods for detecting extrasolar planets and briefly describe the Earth and space based technology currently available and discuss the near-term plans to implement these different search techniques. In each case an attempt is made to identify the limiting source of systematic error inherent to the methodology and to assess the potential for technological improvements.

Tarter, J. C.; Black, D. C.; Billingham, J.

1986-01-01

68

Chemical kinetics on extrasolar planets.  

PubMed

Chemical kinetics plays an important role in controlling the atmospheric composition of all planetary atmospheres, including those of extrasolar planets. For the hottest exoplanets, the composition can closely follow thermochemical-equilibrium predictions, at least in the visible and infrared photosphere at dayside (eclipse) conditions. However, for atmospheric temperatures approximately <2000K, and in the uppermost atmosphere at any temperature, chemical kinetics matters. The two key mechanisms by which kinetic processes drive an exoplanet atmosphere out of equilibrium are photochemistry and transport-induced quenching. I review these disequilibrium processes in detail, discuss observational consequences and examine some of the current evidence for kinetic processes on extrasolar planets. PMID:24664912

Moses, Julianne I

2014-04-28

69

Impact erosion of terrestrial planetary atmospheres  

NASA Technical Reports Server (NTRS)

I review current ideas about the nature of the planetesimals - composition, size distribution, and the planetary encounter velocity. Previous papers on accretion and erosion of planetary atmospheres as a result of multiple impacts are reviewed. Finally, the effects of blowing off a substantial fraction of the atmosphere from a terrestrial planet due to a single giant body impact are discussed.

Ahrens, Thomas J.

1992-01-01

70

Remote Detection of Biosignatures of Primitive and Evolved Life on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Extrasolar planetary detection is at an exciting stage, one in which we are detecting and imaging extrasolar planets as well as measuring their atmospheric constituents. New World Observer (NOW) is a new idea in imaging extrasolar planets currently being proposed to NASA's decadal review.

Demarines, J.; Cash, W.; Domagal-Goldman, S.; Meadows, V.

2010-04-01

71

Planet-Planet Scattering in Planetesimal Disks. II. Predictions for Outer Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

We develop an idealized dynamical model to predict the typical properties of outer extrasolar planetary systems, at radii comparable to the Jupiter-to-Neptune region of the solar system. The model is based upon the hypothesis that dynamical evolution in outer planetary systems is controlled by a combination of planet-planet scattering and planetary interactions with an exterior disk of small bodies ("planetesimals"). Our results are based on 5000 long duration N-body simulations that follow the evolution of three planets from a few to 10 AU, together with a planetesimal disk containing 50 M ? from 10 to 20 AU. For large planet masses (M >~ M Sat), the model recovers the observed eccentricity distribution of extrasolar planets. For lower-mass planets, the range of outcomes in models with disks is far greater than that which is seen in isolated planet-planet scattering. Common outcomes include strong scattering among massive planets, sudden jumps in eccentricity due to resonance crossings driven by divergent migration, and re-circularization of scattered low-mass planets in the outer disk. We present the distributions of the eccentricity and inclination that result, and discuss how they vary with planet mass and initial system architecture. In agreement with other studies, we find that the currently observed eccentricity distribution (derived primarily from planets at a <~ 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 ? 5 m s-1 and periods in excess of 10 years will provide constraints on this regime. Finally, we present an analysis of the predicted separation of planets in two-planet systems, and of the population of planets in mean-motion resonances (MMRs). We show that, if there are systems with ~ Jupiter-mass planets that avoid close encounters, the planetesimal disk acts as a damping mechanism and populates MMRs at a very high rate (50%-80%). In many cases, resonant chains (in particular the 4:2:1 Laplace resonance) are set up among all three planets. We expect such resonant chains to be common among massive planets in outer planetary systems.

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

2010-03-01

72

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

73

Ultraviolet emissions in the planetary atmospheres  

Microsoft Academic Search

Actual state and perspectives of the observations of the planetary atmospheres in the ultraviolet range of wavelengths are\\u000a discussed. The main features of the planetary aeronomy for terrestrial planets, giant planets and exoplanets-transits are\\u000a given. The following hot problems of the planetary astronomy in the UV wavelength range are discussed: (i) UV observations\\u000a of hot coronas of the terrestrial planets;

V. I. Shematovich

2011-01-01

74

Jupiter and the Extrasolar Giant Planets: Composition and origin of atmospheres  

Microsoft Academic Search

In this paper, we will discuss the related issues of the composition and origin of Jupiter's atmosphere, and how this can help in understanding the atmospheres of the extrasolar giant planets (EGP). In the case of Jupiter, a wealth of data on the planet's atmosphere is available, largely as a result of the successful spacecraft observations by the Galileo Orbiter

S. Atreya; A. Wong; P. Mahaffy; H. Niemann; M. Wong; T. Owen

2002-01-01

75

Extrasolar low-orbit planets: Dissipation of their atmospheres and probable magnetic field  

Microsoft Academic Search

Analysis of the data obtained during transits of low-orbit extrasolar planets across the stellar disk yields different estimates\\u000a of their atmospheric loss rates. Experimental data point to the probable existence of several distinct subtypes of extrasolar\\u000a giant planets, including “hot Jupiters” of low density (HD 209458b), with massive cores composed of heavy elements (HD 149026b),\\u000a and others. We show that

L. V. Ksanfomality

2007-01-01

76

The Role of Clouds in Brown Dwarf and Extrasolar Giant Planet Atmospheres  

E-print Network

Clouds and hazes are important throughout our solar system and in the atmospheres of brown dwarfs and extrasolar giant planets. Among the brown dwarfs, clouds control the colors and spectra of the L-dwarfs; the disappearance of clouds helps herald the arrival of the T-dwarfs. The structure and composition of clouds will be among the first remote-sensing results from the direct detection of extrasolar giant planets.

M. S. Marley; A. S. Ackerman

2001-03-16

77

Spectral signatures of photosynthesis II: coevolution with other stars and the atmosphere on extrasolar worlds  

E-print Network

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 planetary atmospheric compositions simulated by Segura, et al. (2003, 2005) for Earth-like planets around observed F2V and K2V stars, 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. 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 NIR, in bands at 0.93-1.1 microns, 1.1-1.4 microns, 1.5-1.8 microns, and 1.8-2.5 microns. In addition, we calculate wavelength restrictions for underwater organisms and depths of water at which they would be protected from UV flares in the early life of M stars. We estimate the potential productivity for both surface and underwater photosynthesis, for both oxygenic and anoxygenic photosynthesis, and for hypothetical photosynthesis in which longer wavelength, multi-photosystem series are used.

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

2007-01-12

78

A Comparative Study of Photochemistry in the Atmospheres of an Extrasolar  

NASA Astrophysics Data System (ADS)

Since the discovery of the first extrasolar planet 51 Peg b (Mayor & Queloz 1995), the formation and evolution of planetary systems have been intensively studied. Most of the known planets have masses similar to the Jupiter and some of them are orbiting close to the central stars at < 0.05 AU. These "hot jupiters" reside in an irradiated environment much more intense than that for our solar system's giant planets. Using the one-dimensional Caltech/JPL KINETICS model, we have simulated the atmospheric photochemical processes of a "hot jupiter". Unlike solar jovian planets, OH and O radicals are more prevalent, driving the chemical reactions in this "hot jupiter". The main results are (a) the atomic hydrogen abundance is 1000 times greater than that of Jupiter and is primarily formed by OH radicals produced in the photolysis of H2O and subsequent reaction of OH + H2, and (b) hydrocarbon formation is initiated by the downward flux of C atoms produced by the photolysis of CO in the upper atmosphere, unlike the colder jovian planets which derive their hydrocarbons from photodissociation of CH4 and subsequent reactions of the products. Hydrocarbon abundances are many orders of magnitude less than those of Jupiter, implying the haze formation is probably insignificant in affecting the optical spectrum/albedo.

Yung, Y. L.; Jiang, X.; Shia, R.; Dowling, T. E.; Liang, M.; Parkinson, C. D.; Lee, A. Y.; Yung, Y.; Seager, S.

2003-12-01

79

Balloon Measurements of Winds in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Atmospheric dynamics can be better measured if data is recorded from many spatially separated capsules. One method under study is to use a planetary lander that releases multiple balloon-bourne transceivers that can be Doppler tracked by the lander.

Wayne, S.; Kitchen, A.; Perry, R.; Petersen, P.; Slater, J.; Oudrhiri, K.; Asmar, S.; Atkinson, D.

2014-06-01

80

Lithium in cool stellar atmospheres: Big bang nucleosynthesis and extrasolar planets  

E-print Network

Lithium in cool stellar atmospheres: Big bang nucleosynthesis and extrasolar planets Matthias Steffen and Elisabetta Caffau Sternphysik In metal-poor stellar atmospheres, the Lithium line at 6707 Ã?-NLTE, respectively. The accurate spectroscopic determination of the Lithium abundance and in particular the 6Li/7Li

81

PLANETARY ATMOSPHERES Jupiter and the Outer Planets  

E-print Network

PLANETARY ATMOSPHERES Contents Jupiter and the Outer Planets Mars Venus Jupiter and the Outer range of atmospheres. The giant planets F Jupiter, Saturn, Uranus, and Neptune F are fluid objects whose equilibrium with solid nitrogen ice on their surfaces. And the Galilean satellites of Jupiter F Io, Europa

82

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

83

Theory of planetary atmospheres. An introduction to their physics andchemistry  

Microsoft Academic Search

Contents: 1. Vertical structure of an atmosphere. 2. Hydrodynamics of atmospheres. 3. Chemistry and dynamics of Earth's stratosphere. 4. Planetary astronomy. 5. Ionospheres. 6. Airglows, auroras, and aeronomy. 7. Stability of planetary atmospheres.

J. W. Chamberlain; D. M. Hunten

1987-01-01

84

Eccentricity Evolution of Extrasolar Multiple Planetary Systems Due to the Depletion of Nascent Protostellar Disks  

NASA Astrophysics Data System (ADS)

Most extrasolar planets are observed to have eccentricities much larger than those in the solar system. Some of these planets have sibling planets, with comparable masses, orbiting around the same host stars. In these multiple planetary systems, eccentricity is modulated by the planets' mutual secular interaction as a consequence of angular momentum exchange between them. For mature planets, the eigenfrequencies of this modulation are determined by their mass and semimajor axis ratios. However, prior to the disk depletion, self-gravity of the planets' nascent disks dominates the precession eigenfrequencies. We examine here the initial evolution of young planets' eccentricity due to the apsidal libration or circulation induced by both the secular interaction between them and the self-gravity of their nascent disks. We show that as the latter effect declines adiabatically with disk depletion, the modulation amplitude of the planets' relative phase of periapsis is approximately invariant despite the time-asymmetrical exchange of angular momentum between planets. However, as the young planets' orbits pass through a state of secular resonance, their mean eccentricities undergo systematic quantitative changes. For applications, we analyze the eccentricity evolution of planets around ? Andromedae and HD 168443 during the epoch of protostellar disk depletion. We find that the disk depletion can change the planets' eccentricity ratio. However, the relatively large amplitude of the planets' eccentricity cannot be excited if all the planets had small initial eccentricities.

Nagasawa, M.; Lin, D. N. C.; Ida, S.

2003-04-01

85

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

Electrostatic charging of dust and its effect on planetary atmospheres is discussed, along with its applications to Martian atmosphere. Laboratory and field experiments in dust storms indicate that the major atmospheric parameters on Mars include: (1) pressure, temperature, and relative humidity; (2) wind velocity and direction; (3) particulate size and composition; and (4) electrostatic charge and field gradient. Various instrumentation techniques adapted for a Mars Lander are briefly reviewed. The effect of exoelectron emission on surface catalysis is studied.

Hoenig, S. A. (principal investigator)

1975-01-01

86

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets VI: Properties of Large-scale Discharge Events  

NASA Astrophysics Data System (ADS)

Mineral clouds in substellar atmospheres play a special role as a catalyst for a variety of charge processes. If clouds are charged, the surrounding environment becomes electrically activated, and ensembles of charged grains are electrically discharging (e.g., by lightning), which significantly influences the local chemistry creating conditions similar to those thought responsible for life in early planetary atmospheres. We note that such lightning discharges contribute also to the ionization state of the atmosphere. We apply scaling laws for electrical discharge processes from laboratory measurements and numerical experiments to DRIFT-PHOENIX model atmosphere results to model the discharge's propagation downward (as lightning) and upward (as sprites) through the atmospheric clouds. We evaluate the spatial extent and energetics of lightning discharges. The atmospheric volume affected (e.g., by increase of temperature or electron number) is larger in a brown dwarf atmosphere (108-1010 m3) than in a giant gas planet (104-106 m3). Our results suggest that the total dissipated energy in one event is <1012 J for all models of initial solar metallicity. First attempts to show the influence of lightning on the local gas phase indicate an increase of small carbohydrate molecules like CH and CH2 at the expense of CO and CH4. Dust-forming molecules are destroyed and the cloud particle properties are frozen in unless enough time is available for complete evaporation. We summarize instruments potentially suitable to observe lightning on extrasolar objects.

Bailey, R. L.; Helling, Ch.; Hodosán, G.; Bilger, C.; Stark, C. R.

2014-03-01

87

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

Microsoft Academic Search

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 \\

Ruth Ann Murray-Clay

2008-01-01

88

Work on Planetary Atmospheres and Planetary Atmosphere Probes  

NASA Technical Reports Server (NTRS)

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

89

ATMOSPHERIC LENSING AND OBLATENESS EFFECTS DURING AN EXTRASOLAR PLANETARY TRANSIT  

E-print Network

at ingress (vice versa for egress). A search over several parameters, such as the limb-darkening profile are strong. Planet oblateness induces an asymmetry to the transit light curve about the point of minimum flux asymmetry is at the level of 0.5% for a projected oblateness of 10%, independent of whether or not lensing

Seager, Sara

90

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

The research for the development of new types of detectors for analysis of planetary atmospheres is summarized. Topics discussed include: corona discharge humidity detector, surface catalysis and exo-electron emission, and analysis of soil samples by means of exo-electron emission. A report on the exo-electron emission during heterogeneous catalysis is included.

Hoenig, S. A.

1972-01-01

91

Space Science I: Planetary Atmospheres  

E-print Network

and evolution of atmospheres #12;Outline Overview of Solar System* Basic Properties of Atmospheres Composition Uranus* 14.5 2.3 56 Neptune* 17.0 2.8 57 Terrestrial-like Venus 0.81 0.56 90 750 Earth 1 0.65 1 280 Mars.0002 N 0.0004 Giant Planets (because of size U,N differ from J,S) Jupiter Saturn Uranus Neptune H2 0

Johnson, Robert E.

92

Work on Planetary Atmospheres and Planetary Atmosphere Probes  

NASA Technical Reports Server (NTRS)

A major objective of the grant 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 grantee was competitively selected to be Principal Investigator of Jupiter's atmosphere structure on the Galileo Probe. His primary motivation was to learn as much as possible about Jupiter's atmosphere by means of a successful atmosphere structure experiment, and to support the needs and schedule of the Galileo Project. After a number of launch delays, the Flight instrument was shipped to Kennedy Space Center 2 years after the start of this collaboration, on April 14, 1989, at which time it was determined from System level tests of the ASI on the Probe that the instrument was in good working order and ready for flight. The spacecraft was launched on October 18, 1989. Data analysis of test and calibration data taken over a period of years of instrument testing was continued in preparation for the encounter. The initial instrument checkout in space was performed on October 26, 1989. The data set received by telemetry was thoroughly analyzed, and a report of the findings was transmitted to the Probe Operations Office on Feb. 28, 1990. Key findings reported were that the accelerometer biases had shifted by less than 1 mg through launch and since calibration at Bell Aerospace in 1983; accelerometer scale factors, evaluated by means of calibration currents, fell on lines of variation with temperature established in laboratory calibrations; pressure sensor offsets, correlated as a function of temperature, fell generally within the limits of several years of ground test data; atmospheric and engineering temperature sensor data were internally consistent within a few tenths of a degree; and the instrument electronics performed all expected functions without any observable fault. Altogether, this checkout was highly encouraging of the prospects of instrument performance, although performed greater than 5 years prior to Jupiter encounter. Capability of decoding the science data from the Experiment Data Record to be provided at encounter was developed and exercised using the tape recording of the first Cruise Checkout data. A team effort was organized to program the selection and combination of data words defining pressure, temperature, acceleration, turbulence, and engineering quantities; to apply decalibration algorithms to convert readings from digital numbers to physical quantities; and to organize the data into a suitable printout. A paper on the Galileo Atmosphere Structure Instrument was written and submitted for publication in a special issue of Space Science Reviews. At the Journal editor's request, the grantee reviewed other Probe instrument papers submitted for this special issue. Calibration data were carefully taken for all experiment sensors and accumulated over a period of 10 years. 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. This report was distributed to experiment coinvestigators and the Probe Project Office.

Seiff, Alvin; Lester, Peter

1999-01-01

93

PLANETARY ATMOSPHERES Winter 2003 (ATMS 555/ASTR 555, ESS 581)  

E-print Network

PLANETARY ATMOSPHERES Winter 2003 (ATMS 555/ASTR 555, ESS 581) Instructor: David Catling Office in planetary atmospheres (Earth, Venus; Mars as a case study). Methane on Titan. 1.2 Energy Sources on Planets. 2. Atmospheric Evolution (Wks 4-8) 2.1 The solar nebula. Planetary formation processes and chemical

Catling, David C.

94

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

The application of detectors developed for analysis of planetary atmospheres under partial vacuum conditions, and data obtained during dust charging studies to various industrial problems is summarized. A specialized apparatus for dust measurements on a planetary lander was designed with the capability of measuring ambient dust density as a function of particle size, as well as for observing the charge of the collected dust. the optical system operates on an intermittent basis and requires only low power. No radioactive source or delicate detection equipment is required. Advances in monitoring catalyst operation by means of exoelection emission are also reported.

Hoenig, S. A.

1978-01-01

95

Atmospheric planetary wave response to external forcing  

NASA Technical Reports Server (NTRS)

The tools of observational analysis, complex general circulation modeling, and simpler modeling approaches were combined in order to attack problems on the largest spatial scales of the earth's atmosphere. Two different models were developed and applied. The first is a two level, global spectral model which was designed primarily to test the effects of north-south sea surface temperature anomaly (SSTA) gradients between the equatorial and midlatitude north Pacific. The model is nonlinear, contains both radiation and a moisture budget with associated precipitation and surface evaporation, and utilizes a linear balance dynamical framework. Supporting observational analysis of atmospheric planetary waves is briefly summarized. More extensive general circulation models have also been used to consider the problem of the atmosphere's response, especially in the horizontal propagation of planetary scale waves, to SSTA.

Stevens, D. E.; Reiter, E. R.

1985-01-01

96

Studies of Tenuous Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

The final report includes an overall project overview as well as scientific background summaries of dust and sodium in comets, and tenuous atmospheres of Jupiter's natural satellites. Progress and continuing work related to dust coma and tenuous atmospheric studies are presented. Also included are published articles written during the course of the report period. These are entitled: (1) On Europa's Magnetospheric Interaction: An MHD Simulation; (2) Dust-Gas Interrelations in Comets: Observations and Theory; and (3) Io's Plasma Environment During the Galileo Flyby: Global Three Dimensional MHD Modeling with Adaptive Mesh Refinement.

Combi, Michael R.

1998-01-01

97

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

E-print Network

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 of the extrasolar planet. We modify analytic expressions for the bi-directional reflectances previously validated by satellite imagery of the Earth to account for the fractional linear polarization of sea-surface reflections and of Rayleigh scattering in the atmosphere. We compare our models with Earth's total visual light and degree of linear polarization as observed in the ashen light of the Moon, or Earthshine. We predict the spatially-integrated reflected light and its degree of polarization as functions of the diurnal cycle and orbital phase of Earth and Earth-like planets of various imagined types. The difference in polarized reflectances of Earth-like planets may increase greatly the detectability of such planets in the glare of their host star. Finally, sea-surface glints potentially may provide a practical means to map the boundaries between oceans and continents on extrasolar planets.

P. R. McCullough

2006-10-17

98

A grid of polarization models for Rayleigh scattering planetary atmospheres  

Microsoft Academic Search

Context: Reflected light from giant planets is polarized by scattering, offering the possibility of investigating atmospheric properties with polarimetry. Polarimetric measurements are available for the atmospheres of solar system planets, and instruments are being developed to detect and study the polarimetric properties of extrasolar planets. Aims: We investigate the intensity and polarization of reflected light from planets in a systematic

Esther Buenzli; H. M. Schmid

2009-01-01

99

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

100

Planetary atmospheric physics and solar physics research  

NASA Technical Reports Server (NTRS)

An overview is presented on current and planned research activities in the major areas of solar physics, planetary atmospheres, and space astronomy. The approach to these unsolved problems involves experimental techniques, theoretical analysis, and the use of computers to analyze the data from space experiments. The point is made that the research program is characterized by each activity interacting with the other activities in the laboratory.

1973-01-01

101

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. I. THE ROLE OF ELECTRON AVALANCHE  

SciTech Connect

Brown dwarf and extrasolar planet atmospheres form clouds which strongly influence the local chemistry and physics. These clouds are globally neutral obeying dust-gas charge equilibrium which is, on short timescales, inconsistent with the observation of stochastic ionization events of the solar system planets. We argue that a significant volume of the clouds in brown dwarfs and extrasolar planets is susceptible to local discharge events. These are electron avalanches triggered by charged dust grains. Such intra-cloud discharges occur on timescales shorter than the time needed to neutralize the dust grains by collisional processes. An ensemble of discharges is likely to produce enough free charges to suggest a partial and stochastic coupling of the atmosphere to a large-scale magnetic field.

Helling, Ch.; Jardine, M. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Witte, S. [Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg (Germany); Diver, D. A., E-mail: ch80@st-andrews.ac.uk [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2011-01-20

102

Spectroscopic Characterisation of Close Orbiting Extrasolar Giant Planets  

Microsoft Academic Search

A number of successful mid-infrared detections and studies of close orbiting extrasolar giant planetary atmospheres have been responsible for both driving and informing modelling efforts. Recent models have indicated that these planets may be subdivided into two groups, one with cooler atmospheres exhibiting solely absorption features, and a second comprising the most highly irradiated atmospheres which possess a temperature inversion

J. R. Barnes; Travis S. Barman; H. R. A. Jones; C. J. Leigh; A. Collier Cameron; Lisa Prato; R. Barber

2009-01-01

103

Dynamics and Origin of Extra-solar Planetary Systems and Microlensing Detection of Extra-solar Planets  

NASA Technical Reports Server (NTRS)

We compare a space-based microlensing search for planets, with a ground based microlensing search originally proposed by D. Tytler (Beichman, et al. 1996). Perturbations of microlensing light curves when the lens star has a planetary companion are sought by one wide angle survey telescope and an array of three or four followup narrow angle telescopes distributed in longitude that follow events with high precision, high time resolution photometry. Alternative ground based programs are considered briefly. With the four 2 meter telescopes distributed in longitude in the southern hemisphere in the Tytler proposal, observational constraints on a ground-based search for planets during microlensing events toward the center of the galaxy are severe. Probably less than 100 events could be monitored per year with high precision, high time resolution photometry with only about 42% coverage on the average regardless of how many events were discovered by the survey telescope. Statistics for the occurrence and properties for Jupiter-mass planets would be meaningful but relatively meager four years after the program was started, and meaningful statistics for Earth-mass planets would be non existent. In contrast, the 14,500 events in a proposed 4 year space based program (GEST = Galactic Exoplanet Survey Telescope) would yield very sound statistics on the occurrence, masses and separations of Jupiter-mass planets, and significant constraints on similar properties for Earth-mass planets. The significance of the Jupiter statistics would be to establish the frequency of planetary systems like our own, where terrestrial planets could exist inside the orbits of the giants.

Peale, S. J.

2003-01-01

104

Diurnal Forcing of Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Much progress has been made on calculations of the Martian seasonal water cycle using the Mars Climate Model developed for this purpose. Two papers, documenting the model and the water transport results obtained with it have been published in the Journal of Geophysical Research - Planets. An additional paper describing results related to the evolution of the seasonal water cycle as a result of orbital changes was published in Advances in Space Research. Since that time, further studies have concentrated on the consequences of the soil adsorption required to match the observed water cycle and its relation to the stability of ground ice and other potential water reservoirs. Earth-related studies have concentrated on incorporating an efficient and realistic microphysical model into the Ames Stratospheric General Circulation Model used to simulate the spread of the ML Pinatubo and other volcanic clouds in the stratosphere. In addition, visualizations of the simulations are being incorporated into a video describing the UARS mission. A paper describing the new stratospheric aerosol microphysics package (and its consequences for volcanic cloud evolution) will be submitted in the near future. The paper will discuss the relative importance of condensation and coagulation to early particle growth and the separation of the cloud by sedimentation of the larger particles. A more general paper which highlights the observation that particle number densities did not increase dramatically after the ML Pinatubo eruption is planned. Simulations of atmospheric transport will be extended to include studies of terrestrial tropospheric tracers using the Fifth-Generation Penn State/NCAR Mesoscale Model.

Houben, Howard C.

1997-01-01

105

Origin and evolution of planetary atmospheres  

NASA Technical Reports Server (NTRS)

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 response to publish interpretations of the Soviet Venera probe XRF experiment data, to investigate the chemistry of volcanic gases, injection of volatiles by cometary and asteroidal impactors, and reactions in the troposphere; (2) we have completed and are now writing up our research on condensation-accretion modeling of the terrestrial planets; (3) we have laid the groundwork for a detailed study of the effects of water transport in the solar nebula on the bulk composition, oxidation state, and volatile content of preplanetary solids; (4) we have completed an extensive laboratory study of cryovolcanic materials in the outer solar system; (5) we have begun to study the impact erosion and shock alteration of the atmosphere of Mars resulting from cometary and asteroidal bombardment; and (6) we have developed a new Monte Carlo model of the cometary and asteroidal bombardment flux on the terrestrial planets, including all relevant chemical and physical processes associated with atmospheric entry and impact, to assess both the hazards posed by this bombardment to life on Earth and the degree of cross-correlation between the various phenomena (NO(x) production, explosive yield, crater production, iridium signature, etc.) that characterize this bombardment. The purpose of these investigations has been to contribute to the developing understanding of both the dynamics of long-term planetary atmosphere evolution and the short-term stability of planetary surface environments.

Lewis, John S.

1992-01-01

106

Atmospheric Circulation of Close-In Extrasolar Giant Planets: I. Global, Barotropic, Adiabatic Simulations  

E-print Network

We present results from a set of over 300 pseudospectral simulations of atmospheric circulation on extrasolar giant planets with circular orbits. The simulations are of high enough resolution (up to 341 total and sectoral modes) to resolve small-scale eddies and waves, required for reasonable physical accuracy. In this work, we focus on the global circulation pattern that emerges in a shallow, ``equivalent-barotropic'', turbulent atmosphere on both tidally synchronized and unsynchronized planets. A full exploration of the large physical and numerical parameter-space is performed to identify robust features of the circulation. For some validation, the model is first applied to Solar System giant planets. For extrasolar giant planets with physical parameters similar to HD209458b--a presumably synchronized extrasolar giant planet, representative in many dynamical respects--the circulation is characterized by the following features: 1) a coherent polar vortex that revolves around the pole in each hemisphere; 2) a low number--typically two or three--of slowly-varying, broad zonal (east-west) jets that form when the maximum jet speed is comparable to, or somewhat stronger than, those observed on the planets in the Solar System; and, 3) motion-associated temperature field, whose detectability and variability depend on the strength of the net heating rate and the global root mean square wind speed in the atmosphere. In many ways, the global circulation is Earth-like, rather than Jupiter-like. However, if extrasolar giant planets rotate faster and are not close-in (therefore not synchronized), their circulations become more Jupiter-like, for Jupiter-like rotation rates.

James Y-K. Cho; Kristen Menou; Brad Hansen; Sara Seager

2006-07-14

107

Determination of Habitable Zones in Extrasolar Planetary Systems: Where are Gaia's Sisters?  

E-print Network

).In other words, the search might have tracked down a sister of "Gaia", i.e., a planet which sup- ports life scheme for assessing the suitability for life of extrasolar planets is pre- sented. The scheme focuses, biogeochemical, and geodynamic processes involved in the generation of photosynthesis-driven life conditions

108

Understanding other worlds: NASA's missions to find and characterize extrasolar planetary systems  

NASA Technical Reports Server (NTRS)

About 150 extrasolar planets, mostly much more massive the Earth, are now known from ground-based observations. Earth-mass planets are very hard, if not impossible, to detect from the ground. The study of planets like our own Earth, orbiting in a 'habitable zone' around their parent stars, will require a new generation of space-based instruments.

Unwin, Stephen C.

2005-01-01

109

Measuring Wind Speeds in the Atmospheres of Extrasolar Hot Jupiters  

NASA Astrophysics Data System (ADS)

3-D dynamical models of hot Jupiter atmospheres predict strong winds in the atmospheres of these planets. For tidally locked hot Jupiters, winds at high altitude in the planet's atmosphere advect heat from the day side to the cooler night side of the planet. Net wind speeds on the order of 1-10 km/s directed towards the night side of the planet are predicted at mbar pressures, which is the approximate pressure level probed by transmission spectroscopy. These winds should result in an observed blue shift of spectral lines in transmission on the order of the wind speed. Indeed, Snellen et al. (2010) recently observed a 2 (+/-) 1 km/s blue shift of CO transmission features for HD 209458b, which has been interpreted as a detection of the day-to-night winds that have been predicted by 3-D atmospheric dynamics modeling. In this talk, I present the results of a coupled 3-D atmospheric dynamics and transmission spectrum model, which predicts the Doppler-shifted spectrum of a hot Jupiter during transit resulting from winds in the planet's atmosphere. We show how Doppler shifted transmission spectra can be used to diagnose wind speeds in the planet's atmosphere, and in certain cases can be used to map wind speeds across the planet's terminator and as a function of altitude.

Kempton, Eliza; Rauscher, E.

2011-09-01

110

Undergraduate Astronomy Laboratory Software: Planetary Atmosphere Evolution  

NASA Astrophysics Data System (ADS)

A computer simulation software package has been developed to evolve planetary atmospheres from their formation through whatever time period the user inputs. Required initial inputs are the spectral class of the star (main sequence stars are assumed) and its chemical abundance, the distance that the planet is from the star, along with the radius, mass, and albedo of the planet. Characteristics of the Earth and Sun are loaded as defaults upon start-up. Once the input is complete, the user clicks on the ``EVOLVE'' button to start the calculations. As the calculations progress, a bar chart shows the relative abundance of important molecules (eg., H2, CO2, etc.) and the thickness of the atmosphere is continually updated. Should conditions warrant, a box will indicate if lifeforms have come into existence. The user can ``PAUSE'' the evolution at any time through the maximum inputed time. The goal of this program is to teach students that the structure of planetary atmospheres result from their initial conditions, change over time, and that the formation of life is a natural occurrence without need for magic. Two versions of this software exist, one written in Visual Basic and the other in IDL. Both will be freely available off of the Web at http://www.etsu.edu/physics/.

Luttermoser, D. G.

1999-12-01

111

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

112

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.

113

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

The development of new types of detectors for analysis of planetary atmospheres is discussed. Initially, the interest was in detectors for use under partial vacuum conditions; recently, the program has been extended to include detectors for use at one atmosphere and adsorption systems for control and separation of gases. Results to date have included detector for O2 and H2 under partial vacuum conditions. Experiments on detectors for use at high pressures began in 1966; and systems for CO, H2, and O2 were reported in 1967 and 1968. In 1968 studies began on an electrically controlled adsorbent. It was demonstrated that under proper conditions a thin film of semiconductor material could be electrically cycled to absorb and desorb a specific gas. This work was extended to obtain quantitative data on the use of semiconductors as controllable adsorbents.

Hoenig, S. A.; Summerton, J. E.; Kirchner, J. D.; Allred, J. B.

1974-01-01

114

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

The development of new types of detectors for analysis of planetary atmospheres is discussed. Initially, the interest was in detectors for use under partial vacuum conditions. The program has been extended to include detectors for use at one atmosphere and adsorption system for control and separation of gases. Results to date have included detectors for O2 and H2 under partial vacuum conditions. Experiments on detectors for use at high pressures began in 1966, and systems for CO, H2, and O2, were reported. Electrically controlled adsorbent was developed. It was demonstrated that under proper conditions a thin film of semiconductor material could be electrically cycled to adsorb and desorb a specific gas. This work was extended to obtain quantitative data on the use of semiconductors as controllable adsorbents.

Hoenig, S. A.

1971-01-01

115

Constraints on planetary formation from the discovery & study of transiting Extrasolar Planets  

NASA Astrophysics Data System (ADS)

After centuries of wondering about the presence of other worlds outside our Solar System, the first extrasolar planets were discovered about fifteen years ago. Since the quest continued. The greatest discovery of our new line of research, exoplanetology, has probably been the large diversity that those new worlds have brought forward; a diversity in mass, in size, in orbital periods, as well as in the architecture of the systems we discover. Planets very different from those composing our system have been detected. As such, we found hot Jupiters, gas giants which orbital period is only of a few days, mini-Neptunes, bodies five to ten time the mass of the Earth but covered by a thick gas layer, super-Earths of similar masses but rocky, lava worlds, and more recently, maybe the first ocean planet. Many more surprises probably await us. This thesis has for subject this very particular planet class: the hot Jupiters. Those astonishing worlds are still badly understood. Yet, thanks to the evolution of observational techniques and of the treatment of their signals, we probably have gathered as much knowledge from these worlds, than what was known of our own gas giants prior to their visit by probes. They are laboratories for a series of intense physical phenomena caused by their proximity to their star. Notably, these planets are found in average much larger than expected. In addition to these curiosities, their presence so close to their star is abnormal, the necessary conditions for the formation of such massive bodies, this close, not being plausible. Thus it is more reasonable to explain their current orbits by a formation far from their star, followed by an orbital migration. It is on this last subject that this thesis is on: the origin of hot Jupiters. The laws of physics are universal. Therefore, using the same physical phenomena, we need to explain the existence of hot Jupiters, while explaining why the Jupiter within our Solar System is found five times the Earth-Sun distance. In Astronomy, we cannot do experiments; we are a part of it. Instead, we search and characterise several similar objects in order to extract information out of them statistically. To answer our question, we needed to find several objects and detect the clues from their past history bringing us back to the processes that led to their formation. There are several manners with which one can find planets. For this thesis, the so-called transit method was used. It consists in detecting a periodic loss of light from a star in front of which a planet passes: a transit. This method is particularly sensitive to the presence of hot Jupiters. During this thesis, about fifty planets of such type have been discovered, about a third of the known hot Jupiters. Those planets are confirmed thanks to radial velocity measurements, the same technique that led to the discovery of the first extrasolar planet, around the star 51 Pegasi. The analysis of the stellar light affected by the presence of a planet around it, notably the light received during transit, allows us to know about the mass, the size of the planet, its orbital period, the shape of its orbit, its temperature, even the chemical composition of its atmosphere. Furthermore, these observations give us the occasion to study the star around which is found the planet, such as its mass, its size, its rotation speed, as well as give estimates on its age. One type of observations was employed in particular: the Rossiter-McLaughlin effect. During transit, this effect creates an anomaly compared to the expected radial velocities. Through a modelisation of this anomaly, it is possible to measure the projection of the angle between the orbital plane of the planet and the equatorial plane of the star, on the sky. In our System, all planets are located more or less in a same plane : the ecliptic. The equatorial plane of the Sun is also almost aligned with the ecliptic. This observation led Kant and Laplace to postulate on the formation of planets from matter spread in the form of a primordial disc around the Sun; such

Triaud, A. H. M. J.

2011-08-01

116

Atmosphere Models for the Brown Dwarf Gliese 229 B and the Extrasolar Giant Planets  

NASA Technical Reports Server (NTRS)

Brown dwarfs inhabit a realm intermediate between the more massive stars and the less massive planets. Their thermal infrared emission is powered by the release of gravitational potential energy as regulated by their atmospheres. Long known only as theoretical constructs. the discovery of the first unimpeachable brown dwarf. Gliese 229 has opened up a new field: the study of brown dwarf atmospheres. The subsequent discoverv of numerous extrasolar giant planets circling nearby stars, further demonstrated the need for a comprehensive modeling effort to understand this new class of jovian atmospheres. Although no spectra are yet available of the new planets, the next generation of groundbased and spacebased telescopes will return such data. Here author report on the effort with Ames collaborator Dr. Christopher McKay to better understand these new atmospheres.

Marley, Mark S.

1996-01-01

117

Planetary Atmospheres Earth and the Other Terrestrial Worlds  

E-print Network

per sq. inch ­ 1 bar Where does an atmosphere end? · There is no clear upper boundary · Most of Earth1 Chapter 10 Planetary Atmospheres Earth and the Other Terrestrial Worlds What is an atmosphere? An atmosphere is a layer of gas that surrounds a world Earth s Atmosphere · About 10 km thick · Consists mostly

Crenshaw, Michael

118

Constraining Oxygen False Positives in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Oxygen (O2) and ozone (O3) in the present Earth's atmosphere are byproducts of oxygenic photosynthesis coupled with organic carbon burial. On Earth, no known abiotic surface process would be able to generate such an atmosphere, and by extension, lifeless exoplanets are expected to be devoid of O2. As a result, molecular oxygen and ozone are often seen as convincing signposts for life. Recently, however, a number of authors have demonstrated the abiotic generation of molecular oxygen in a planetary atmosphere, either under oxidizing conditions (Hu et al., 2013) or around an M star (Tian et al., 2013). This èfalse positive', if verified, would remove oxygen and ozone from an already short list of easily detectable biosignatures. We explore oxygen false positives with our 1-D photochemical model, updated from Segura et al. (2007). Preliminary results show that if water vapor photolysis longward of ~200 nm is neglected, substantial amounts of CO and O2 can build up in the lower part of the atmosphere. Additionally, the ultimate fate of CO and O2 produced in such atmospheres is strongly dependent on the imposed lower boundary condition, with low depositional velocities corresponding to higher mixing ratios in the lower atmosphere. The deposition velocity of a gas depends on it dissolved concentration, however, and so one needs to consider the chemistry of these gases in solution. Ongoing work seeks to test the conclusions of Tian et al., (2013) by exploring this dependence on ocean chemistry and by including spectra from AD Leo (an active M-dwarf, used by Domagal-Goldman et al., (2011)) to compare with the M-dwarf spectra used by Tian et al.

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

2014-03-01

119

Arctic Climate and Atmospheric Planetary Waves  

NASA Technical Reports Server (NTRS)

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave I pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach to determine significant forcing patterns of sea ice and high-latitude variability.

Cavalieri, D. J.; Haekkinen, S.

2000-01-01

120

Arctic Climate and Atmospheric Planetary Waves  

NASA Technical Reports Server (NTRS)

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave 1 pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach for determining significant forcing patterns of sea ice and high-latitude variability.

Cavalieri, D. J.; Haekkinen, S.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

121

A theoretical framework for volcanic degassing chemistry in a comparative planetology perspective and implications for planetary atmospheres  

NASA Astrophysics Data System (ADS)

Magmatic degassing is ubiquitous and enduring, yet its impact on both planetary surficial chemistry and how it may have varied among planetary systems remains imprecise. A large number of factors are likely to be involved in the control of magmatic gas compositions, leading roles being given to the redox state and volatile abundances in planetary interiors, and the fate of the latter during mantle melting. We however show that the pressure at which degassing occurs, that is the atmospheric pressure in most sensible cases, has a prime influence on the composition of subaerial volcanic gases on planets: high surface pressure produces N2- and CO2-rich and dry volcanic gases, while low pressure promotes sulfur-rich gases. In-between, atmospheric pressures close to 1 bar trigger volcanic gases dominated by H2O. This simple pattern broadly mirrors the atmospheres of Venus-Earth-Mars-Io planetary suite and constitutes benchmarks for the prediction and interpretation of atmospheric features of extra-solar planets. Volatile abundances within the planetary body interiors also matter but they play a secondary role. Furthermore, our analysis shows that any difference in redox conditions prevailing during partial melting tends to disappear with the degassing process itself, converging toward a unique - planetary oxygen fugacity - at the venting pressure. A feedback relationship between volcanic gas compositions and atmospheric pressure implies a runaway drying during atmospheric growth; that is volcanic gases must become CO2 richer as the atmospheric mass increases. This may explain some features of the Venusian atmosphere. On Earth, impact ejection of the atmosphere and CO2-sink mechanisms, such as carbonate precipitation and plate tectonics, must have decreased atmospheric pressure allowing the reestablishment of water-rich volcanic gases.

Gaillard, Fabrice; Scaillet, Bruno

2014-10-01

122

Dust in the solar system and in extra-solar planetary systems  

Microsoft Academic Search

Among the observed circumstellar dust envelopes a certain population, planetary debris disks, is ascribed to systems with\\u000a optically thin dust disks and low gas content. These systems contain planetesimals and possibly planets and are believed to\\u000a be systems that are most similar to our solar system in an early evolutionary stage. Planetary debris disks have been identified\\u000a in large numbers

Ingrid Mann; Melanie Köhler; Hiroshi Kimura; Andrzej Cechowski; Tetsunori Minato

2006-01-01

123

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

124

Hydrodynamics of Highly Irradiated Planetary Atmospheres  

Microsoft Academic Search

Among the discovered extrasolar planets, a large fraction are close-in giant planets orbiting with periods of only a few days. Unlike Jupiter, intense stellar irradiation and slow rotation due to tidal locking drive unique flow dynamics across the surfaces of these planets. Current and ongoing transit and photometric monitoring campaigns have allowed us an unprecedented look the energy distribution resulting

Ian Dobbs-Dixon

2008-01-01

125

Aerodynamic Heating and Deceleration During Entry into Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Aerodynamic Heating and Deceleration During Entry into Planetary Atmospheres. Dr. Chapman's lecture examines the physics behind spacecraft entry into planetary atmospheres. He explains how scientists determine if a planet has an atmosphere and how scientists can compute deceleration when the atmospheric conditions are unknown. Symbols and equations used for calculations for aerodynamic heating and deceleration are provided. He also explains heat transfer in bodies approaching an atmosphere, deceleration, and the use of ablation in protecting spacecraft from high temperatures during atmospheric entry. [Entire movie available on DVD from CASI as Doc ID 20070030962. Contact help@sti.nasa.gov

1962-01-01

126

Dynamical Simulations of Extrasolar Planetary Systems with Debris Disks Using a GPU Accelerated N-Body Code  

NASA Astrophysics Data System (ADS)

This thesis begins with a description of a hybrid symplectic integrator named QYMSYM which is capable of planetary system simulations. This integrator has been programmed with the Compute Unified Device Architecture (CUDA) language which allows for implementation on Graphics Processing Units (GPUs). With the enhanced compute performance made available by this choice, QYMSYM was used to study the effects debris disks have on the dynamics of the extrasolar planetary systems HR 8799 and KOI-730. The four planet system HR 8799 was chosen because it was known to have relatively small regions of stability in orbital phase space. Using this fact, it can be shown that a simulated debris disk of moderate mass around HR 8799 can easily pull this system out of these regions of stability. In other cases it is possible to migrate the system to a region of stability - although this requires significantly more mass and a degree of fine tuning. These findings suggest that previous studies on the stability of HR 8799 which do not include a debris disk may not accurately report on the size and location of the stable orbital phase space available for the planets. This insight also calls into question the practice of using dynamical simulations to help constrain observed planetary orbital data. Next, by studying the stability of another four planet system, KOI-730, whose planets are in an 8:6:4:3 mean motion resonance, we were additionally able to determine mass constraints on debris disks for KOI-730 like Kepler objects. Noting that planet inclinations increase by a couple of degrees when migrating through a Neptune mass debris disk, and that planet candidates discovered by the Kepler Space Telescope are along the line of site, it is concluded that significant planetary migration did not occur among the Kepler objects. This result indicates that Kepler objects like KOI-730 have relatively small or stable debris disks which did not cause migration of their planets - ruling out late-heavy bombardment style events. In both cases, the inclusion of debris disks in our simulations provided new results or useful constraints.

Moore, Alexander

127

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

128

An aluminum/calcium-rich, iron-poor, white dwarf star: evidence for an extrasolar planetary lithosphere?  

E-print Network

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. 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 Eart...

Zuckerman, B; Dufour, P; Melis, Carl; Klein, B; Jura, M

2011-01-01

129

On the Stability of Extrasolar Planetary Systems and other Closely Orbiting Pairs  

E-print Network

This paper considers the stability of tidal equilibria for planetary systems in which stellar rotation provides a significant contribution to the angular momentum budget. We begin by applying classic stability considerations for two bodies to planetary systems --- where one mass is much smaller than the other. The application of these stability criteria to a subset of the Kepler sample indicates that the majority of the systems are not in a stable equilibrium state. Motivated by this finding, we generalize the stability calculation to include the quadrupole moment for the host star. In general, a stable equilibrium requires that the total system angular momentum exceeds a minimum value (denoted here as $L_X$) and that the orbital angular momentum of the planet exceeds a minimum fraction of the total. Most, but not all, of the observed planetary systems in the sample have enough total angular momentum to allow an equilibrium state. Even with the generalizations of this paper, however, most systems have too lit...

Adams, Fred C

2014-01-01

130

Evaporation of extrasolar planets  

E-print Network

Atomic hydrogen escaping from the extrasolar giant planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. In fact, the upper atmosphere of this planet is evaporating. Observational evidences and interpretations coming from various models are reviewed. Implications for exoplanetology are discussed.

David Ehrenreich

2008-07-11

131

The Presence of Methane in the Atmosphere of an Extrasolar Planet  

NASA Technical Reports Server (NTRS)

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 (micro)m confirms the recent claim4 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.

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

2008-01-01

132

Franklin Lecture: Lightning in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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 flashes produced by lightning; (2) high-frequency radio measurements to detect the impulsive broadband radio bursts, called spherics, produced by lightning discharges; and (3) low-frequency plasma wave measurements to detect the whistling tones, called whistlers, produced by lightning. Using these techniques, lightning has been reported at five planets other than Earth. These are: Venus, Jupiter, Saturn, Uranus, and Neptune. Of these, the existence of lightning at Venus is doubtful, and the evidence of lightning at Neptune is at best marginal. Jupiter and Saturn have by far the most intense and well documented lightning activity. During the Voyager 1 flyby of Jupiter, whistlers and intense optical flashes, comparable to those from terrestrial superbolts, were observed by the plasma wave and optical imaging instruments. However, no impulsive high-frequency radio bursts were observed. Two factors may be responsible for the absence of high-frequency radio signals: (1) the very strong magnetic field of Jupiter, which blocks the escape of the extra-ordinary mode; and (2) the relatively high electron collision frequency in the ionosphere, which increases the absorption of radio waves. During the Voyager 1 and 2 flybys of Saturn many very strong high-frequency radio bursts, called Saturn Electrostatic Discharges (SEDs), were detected. Although the origin of these impulsive radio bursts was initially uncertain, strong evidence now exists that SEDs are produced by lightning. Recent optical imaging and radio measurements from the Cassini spacecraft clearly show that SEDs originate from reappearing convective storms that are carried around by Saturn's rotation. One whistler has been observed at Saturn, but no optical flashes have been observed, possibly due to the enhanced background caused by ring shine, or due to extinction caused by clouds or haze in the atmosphere. During the Voyager 2 flyby of Uranus, numerous high- frequency radio bursts, called Uranian Electrostatic Discharges (UEDs), were observed that are comparable to those at Saturn, although at a much lower rate. No optical flashes or whistlers were observed at Uranus. The available data shows that the lightning discharges at Jupiter, Saturn, Uranus, and maybe Neptune, are much more intense than terrestrial lightning, by factors of 10{^1} to 10{4}, depending on the method of comparison. Since the electrical breakdown field increases with pressure, the high intensities suggest that lightning at the giant planets, and the convective storms that cause the discharges, occur deep in the atmosphere, at pressures considerably greater than for terrestrial lightning.

Gurnett, D. A.

2006-12-01

133

A Systematic Retrieval Analysis of Secondary Eclipse Spectra. III. Diagnosing Chemical Disequilibrium in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Chemical disequilibrium has recently become a relevant topic in the study of the atmospheres of transiting extrasolar planets, brown dwarfs, and directly imaged exoplanets. We present a new way of assessing whether or not a Jovian-like atmosphere is in chemical disequilibrium from observations of detectable or inferred gases such as H2O, CH4, CO, and H2. Our hypothesis, based on previous kinetic modeling studies, is that cooler atmospheres will show stronger signs of disequilibrium than hotter atmospheres. We verify this with chemistry-transport models and show that planets with temperatures less than ~1200 K are likely to show the strongest signs of disequilibrium due to the vertical quenching of CO, and that our new approach is able to capture this process. We also find that in certain instances a planetary composition may appear in equilibrium when it actually is not due to the degeneracy in the shape of the vertical mixing ratio profiles. We determine the state of disequilibrium in eight exoplanets using the results from secondary eclipse temperature and abundance retrievals. We find that all of the planets in our sample are consistent with thermochemical equilibrium to within 3?. Future observations are needed to further constrain the abundances in order to definitively identify disequilibrium in exoplanet atmospheres.

Line, Michael R.; Yung, Yuk L.

2013-12-01

134

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. PMID:20368254

Jupp, Tim E.; Cox, Peter M.

2010-01-01

135

Plasma-induced Escape and Alterations of Planetary Atmospheres  

Microsoft Academic Search

The atmospheres of planets and planetary satellites are typically imbedded in space plasmas. Depending on the interaction with the induced or intrinsic fields energetic ions can have access to the thermosphere and the corona affecting their composition and thermal structure and causing loss to space. These processes are often lumped together as `atmospheric sputtering' (Johnson 1994). In this talk I

R. E. Johnson; O. J. Tucker; J. Ewrin; T. A. Cassidy; F. Leblanc

2009-01-01

136

Planetary Research Center. [astronomical photography of planetary surfaces and atmospheres  

NASA Technical Reports Server (NTRS)

Extensive Earth-based photography of Mars, Jupiter, and Venus is presented which monitors the atmospheric and/or surface changes that take place day to day. Color pictures are included of the 1973 dust storm on Mars, showing the daily cycle of the storm's regeneration. Martian topography, and the progress of the storm is examined. Areas most affected by the storm are summarized.

Baum, W. A.; Millis, R. L.; Bowell, E. L. G.

1974-01-01

137

Hadley cells in planetary atmospheres without a condensible component  

NASA Astrophysics Data System (ADS)

A key goal for theories of planetary atmospheres is to predict features of the circulation purely on the basis of planetary parameters observable from Earth. Tropical overturning circulations or Hadley cells play an important role in the general circulation of any atmosphere. Here, we extend and generalise previous work to provide a complete theory for the axially-symmetric Hadley cell in compressible, radiative-convective atmospheres under the simplifying assumptions that radiation is semi-gray and that the atmosphere contains no condensible component. The theory is analytically tractable and provides both tropopause height and Hadley cell width as a function of planetary parameters. The relevant parameters turn out to be radius, rotation rate, insolation, infrared optical depth and spectral bandwidth, and the ratio of gas constant to heat capacity. The theory converges to the classic result of Held and Hou in the Boussinesq limit, when tropopause height ? scale height.

Caballero, R.; Mitchell, J.; Pierrehumbert, R.

2006-12-01

138

Symposium on Planetary Atmospheres, 19th, Ottawa, Canada, August 16-19, 1977, Proceedings  

Microsoft Academic Search

Atmospheres of the planets are discussed with particular emphasis on planetary spectroscopy, the aeronomy of planetary atmospheres, and the new Viking results for Mars. Spectroscopic techniques for determining abundances as well as hypotheses concerning planetary atmospheres are considered. Investigations of Venus, Jupiter, and the outer planets are reported in addition to studies of the upper atmosphere and the lower atmosphere

A. Vallance Jones

1977-01-01

139

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

140

A New Perspective on Trapped Radiation Belts in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

The charged particle fluxes trapped in the magnetic dipole fields of certain planets in our Solar System are interesting signatures of planetary properties in space physics. They also represent a source of potentially hazardous radiation to spacecraft during planetary and interplanetary exploration. The Earth s trapped radiation belts have been studied for years and the physical mechanisms by which primary radiation from the Sun and Galaxy is captured is well understood. The higher-energy particles collide with molecules in the planetary atmosphere and initiate large cascades of secondary radiation which itself becomes trapped by the magnetic dipole field of the planet. Some of it is even backscattered as albedo neutrons.

Diaz, A.; Lodhi, M. A. K.; Wilson, T. L.

2005-01-01

141

Electrodynamics on Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

Strong ionization on close-in extrasolar giant planets (EGPs) suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive magnetohydrodynamics that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an upper ionosphere dominated by ionization of H and He and a lower ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter the energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments. We find that the atmospheric conductivity decreases by several orders of magnitude in the night side of tidally locked planets, leading to a potentially interesting large-scale dichotomy in electrodynamics between the day and night sides. A combined approach that relies on UV observations of the upper atmosphere, phase curve and Doppler measurements of global dynamics, and visual transit observations to probe the alkali metals can potentially be used to constrain electrodynamics in the future.

Koskinen, T. T.; Yelle, R. V.; Lavvas, P.; Y-K. Cho, J.

2014-11-01

142

Understanding the Outer Planets and Planetary Atmospheres  

E-print Network

: · Geological processes on Mars · Evolution of Saturn's ring system · Interaction of magnetospheric plasma that planetary rings, once thought unique to the planet Saturn, exist around all the giant planets. These rings to determine the structure, composition, and history of Saturn's rings. #12;201:20130919.1248 The Laboratory

Mojzsis, Stephen J.

143

Planetary waves in Jupiter's equatorial atmosphere  

NASA Astrophysics Data System (ADS)

Planetary-scale waves which have been latitudinally trapped within the equatorial jet of Jupiter are attested to by Voyager IR, radio occultation, and imaging data. An effort is presently made to identify a distinguishing class of planetary wave modes in the course of interpreting these data, with special attention being given to the equatorial plume features observed. A comparative evaluation of horizontal dispersion properties for linear wave modes on an equatorial beta plane suggests that the Rossby modes with a meridional structure index of 1 and an equivalent depth of 2-4 km are the interpretation most nearly consistent with all of the observational data for an equatorially trapped, wavenumber 12 pattern.

Allison, M.

1990-02-01

144

Scientific program in planetary atmospheric studies  

NASA Technical Reports Server (NTRS)

The Voyager encounters with Jupiter led to two main areas of investigation: (1) the definition of the structure and composition of the upper atmosphere and the interaction of the magnetosphere and atmosphere, and (2) the study of the plasma torus using the EUV (Extreme Ultraviolet) data in conjunction with ground-based and in-situ measurements. In the course of these investigations, the atmosphere studies were extended to a comparative study with the bound atmospheres of Saturn and Titan; and the torus study expanded to include the extended atmospheres of Titan (the H torus) and the rings of Saturn.

Broadfoot, A. L.

1983-01-01

145

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

146

An application of gas chromatography to planetary atmospheres  

NASA Technical Reports Server (NTRS)

A gas chromatography developed for the Viking experiment is described. The instrument is designed to measure gases in planetary atmospheres and head space in a chamber. It is hoped that the chromatograph will also measure any biological activity present in these environments.

Oyama, V.

1974-01-01

147

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

148

Meteoroids in solar corona and planetary atmospheres  

Microsoft Academic Search

We simulate the meteoroid entry into the solar corona with a model similar to the one-dimensional ablation model developed by Campbell-Brown and Koschny (2004) for the Earth's atmosphere and by McAuliffe and Christou (2005) for the case of the atmosphere of Venus. We present the results of mass deposition profiles for a wide range of masses for objects falling into

Herve Lamy; Ingrid Mann; Emeritus Joseph Lemaire

2010-01-01

149

Electrodynamics on extrasolar giant planets  

E-print Network

Strong ionization on close-in extrasolar giant planets suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive MHD that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an upper ionosphere dominated by ionization of H and He and a lower ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conduc...

Koskinen, T T; Lavvas, P; Cho, J Y-K

2014-01-01

150

Asteroid observations and planetary atmospheres analysis  

NASA Technical Reports Server (NTRS)

Photoelectric observations of Eros and 30 other asteroids providing information on their surface characteristics, shape, and rotation axes are reported. Photographs of 18 asteroids and 4 comets yielding accurate position information on various dates were obtained. Photometric observations were made of the Saturn satellite lapetus, and electronographic images of the Uranus and Neptune satellites were obtained experimentally with a Spectracon tube to assess photometry by that method. Planetary patrol photographs of Venus and deconvolved area scans of Uranus were taken. UBV photometry of the Galilean satellites for the period 1973-1974 was completely analyzed and accepted for publication. An improved magnitude and color index for Minas were derived from 1974 area scans. A special photomultiplier tube with a suppressor grid was incorporated into a pulse-counting photometer with special added circuitry for carrying out the observations concerning the constancy of solar system dimensions over cosmic time.

Baum, W. A.; Millis, R. L.; Bowell, E. L. G.

1975-01-01

151

Fourier transform spectroscopy to study planetary atmospheres.  

NASA Astrophysics Data System (ADS)

Motivated by the selection of MATMOS for the ExoMars Trace Gas Orbiter (withdrawn), we have been working on algorithms for retrieving information about the Martian atmosphere using infrared spectroscopy.The Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS) was a joint Canadian Space Agency (CSA) and Jet Propulsion Laboratory (JPL) mission to send a high-resolution Fourier transform spectrometer to Mars, similar to the CSA's Atmospheric Chemistry Experiment (ACE) FTS. The ACE-FTS, currently in Earth orbit, is a solar-occultation instrument measuring the solar spectrum between 750-4400 cm (-1) at a spectral resolution of 0.02 cm (-1) . We present an algorithm to retrieve temperatures and pressures from measured spectra, accurate knowledge of which is vital for inferring volume mixing ratios of trace gases. The effects of high dust quantities on spectra have been simulated using synthetic spectra of the Martian atmosphere and a method for mitigating these effects has been tested and will be presented. Work has been done to characterize the interferometer performance of the Engineering Demonstration Unit, constructed by ABB, with a focus on gaining a better understanding of the modulation efficiency of the interferometer.

Olsen, Kevin; Walker, Kaley; Strong, Kimberly; Hipkin, Victoria; Toon, Geoff; Conway, Stephanie; Berube, Philippe; Veilleux, James

152

Extrasolar planets and brown dwarfs around A-F type stars V. A planetary system found with HARPS around the F6IV-V star HD 60532  

E-print Network

Aims: In the frame of the search for extrasolar planets and brown dwarfs around early-type stars, we present the results obtained for the F-type main-sequence star HD 60532 (F6V) with HARPS. Methods: Using 147 spectra obtained with HARPS at La Silla on a time baseline of two years, we study the radial velocities of this star. Results: HD 60532 radial velocities are periodically variable, and the variations have a Keplerian origin. This star is surrounded by a planetary system of two planets with minimum masses of 1 and 2.5 Mjup and orbital separations of 0.76 and 1.58 AU respectively. We also detect high-frequency, low-amplitude (10 m/s peak-to-peak) pulsations. Dynamical studies of the system point toward a possible 3:1 mean-motion resonance which should be confirmed within the next decade.

M. Desort; A. -M. Lagrange; F. Galland; H. Beust; S. Udry; M. Mayor; G. Lo Curto

2008-09-23

153

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

154

Formulation of molecular diffusion in planetary atmospheres  

NASA Astrophysics Data System (ADS)

We report on a formulation of molecular diffusion for ionized multi-component atmospheres that is valid in the diffusion and small electron mass limits. The formulation is based on the construction of successive approximations of the diffusion matrix by means of the projective iterative algorithm of Ern and Giovangigli [Projected iterative algorithms with application to multicomponent transport. Lin. Alg. and its Appl. 250, 289-315], and allows naturally for different temperatures for the neutral, ion and electron constituents of the gas. The reported expressions incorporate the effect of electric forces preventing charge separation, are explicit in the driving forces and mass conservative. Yet approximate, their accuracy can be easily tested and improved upon by going to a higher approximation of the diffusion matrix. We have illustrated the formulation with a model that solves the composition of Mars' atmosphere. The continuity equations of the model are linearized and marched in time with an implicit numerical scheme, allowing thus for large time steps. It is found that the first and second approximations of the diffusion matrix are probably optimal trade-offs between computational cost and accuracy. Finally, the formulation is tested against more conventional approximations of the molecular diffusion velocities of neutral and ion species, showing the importance of the various assumptions that may restrict their applicability.

García Muñoz, A.

2007-07-01

155

Upper atmospheric planetary-wave and gravity-wave observations  

NASA Technical Reports Server (NTRS)

Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily-difference method, and results on the magnitude of atmospheric perturbations interpreted as gravity waves and planetary waves are presented. Traveling planetary-wave contributions in the 25-85 km range were found to have significant height and latitudinal variation. It was found that observed gravity-wave density perturbations and wind are related to one another in the manner predicted by gravity-wave theory. It was determined that, on the average, gravity-wave energy deposition or reflection occurs at all altitudes except the 55-75 km region of the mesosphere.

Justus, C. G.; Woodrum, A.

1973-01-01

156

50&100YEARSAGO EXTRASOLAR PLANETS  

E-print Network

be harmful to the bulk of complex life forms on Earth. Jupiter's methane, meanwhile, isphotochemicalinorigin emission from methane in the upper atmosphere of a Jupiter-like extrasolar planet. The first extrasolar the discovery of fluorescent emission from methane in the upper atmosphere of a nearby, Jupiter-mass extrasolar

Royer, Dana

157

Atmospheric circulation modeling of super Earths and terrestrial extrasolar planets using the SPARC/MITgcm  

NASA Astrophysics Data System (ADS)

The field of exoplanets continues to be a booming field of research in astronomy and planetary science, with numerous ground-based (e.g., SuperWASP, HARPS-N and S) and space-based surveys (e.g., Kepler) that detect and characterize planets ranging from hot Jupiters, Jovian-sized planets orbiting less than 0.1 AU from their star, to super Earths and terrestrial exoplanets, planets that have masses equal to or less than 10 times that of Earth with a range of orbital distances. Atmospheric circulation modeling plays an important role in the characterization of these planets, helping to constrain observations that probe their atmospheres. These models have proven successful in understanding observations of transiting exoplanets (when the planet passes in front of the star along our line of sight) particularly when the planet is passing through secondary eclipse (when the planet's dayside is visible). In modeling super Earths and terrestrial exoplanets, we must consider not only planets with thick fluid envelopes, but also traditional terrestrial planets with solid surfaces and thinner atmospheres. To that end, we present results from studies investigating the atmospheric circulation of these classes of planets using the SPARC/MITgcm, a state-of-the-art model which couples the MIT General Circulation Model with a plane-parallel, two-stream, non-gray radiative transfer model. We will present results from two studies, the first focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth ground-based survey, and a second study which explores the circulation of terrestrial exoplanets orbiting M-dwarfs.

Kataria, T.; Showman, A. P.; Haberle, R. M.; Marley, M. S.; Fortney, J. J.; Freedman, R. S.

2013-12-01

158

An Analytic Radiative-Convective Model for Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

A fundamental aspect of planetary atmospheres is the vertical thermal structure. Simple one-dimensional (vertical) models can provide reasonable estimates of a planet's global-mean temperature profile while providing insights into the physics behind the thermal profile of an atmosphere. The best basic models are those that incorporate the minimum amount of complexity while still remaining general enough to provide intuitive understanding. Here, we present an analytic 1-D radiative-convective model of the thermal structure of planetary atmospheres [1]. We assume that thermal radiative transfer is gray, and we include two shortwave channels for absorbed solar (or stellar) light so that the model can compute realistic stratospheric temperature inversions. A convective profile is placed at the base of the portion of the atmosphere that is in radiative equilibrium, and the model ensures that both the temperature profile and the upwelling flux profile are continuous across the radiation-convection boundary. The convective portions of our models are taken to follow adiabats that account for condensation of volatiles through a scaling parameter to the dry adiabat. By combining these assumptions, we produce analytic expressions that allow calculations of the atmospheric pressure-temperature profile, as well as expressions for the profiles of thermal radiative flux and convective flux. The utility, validity, and generality of our model are demonstrated by applying it to a disparate range of worlds, including Jupiter, Venus, and Titan. Our model can be used to explain general observed phenomena in the Solar System [2], and we explore the behaviors of variants of our model, showing its ability to provide clear insights. Given the wealth of new problems posed by exoplanets, development of an analytic model with few parameters is likely to be useful for future application to such worlds, for which only limited data will be known. Our model can be used to help interpret observations of, and make predictions for, these worlds. For example, our model could be used in retrieval schemes that are currently being developed for exoplanets. As our model incorporates the essential physics of a 1-D planetary atmosphere with only a small number of free parameters, it is well suited to extracting information from sparse exoplanet observations. [1] T. D. Robinson, and D. C. Catling. An analytic radiative-convective model for planetary atmospheres, ApJ, in press. [2] T. D. Robinson, and D. C. Catling. A "0.1 bar Tropopause Law" in thick atmospheres of planets and large moons, submitted.

Robinson, T. D.; Catling, D. C.

2012-12-01

159

Ultraviolet imaging and spectroscopy of planetary atmospheres  

NASA Technical Reports Server (NTRS)

The main scientific results of the participation of the Institute of Astrophysics (Belgium) in the NASA's Pioneer Venus mission are reported on. The data were obtained with the Pioneer Orbiter's Ultraviolet Spectrometer (POUVS). The instrument provided a morphological study of the nitric oxide ultraviolet night glow. Information concerning the altitude of the airglow emitting layer was also collected and used to constrain models of turbulent transport on the night side of the planet. Models of the odd nitrogen thermospheric chemistry and transport were developed to analyze the observations and derive the properties of the global circulation of Venus' upper atmosphere. Images of the Jovian ultraviolet aurora were obtained. The morphology and the time variations of the HI Ly-alpha and H2 Lyman and Werner bands were acquired at different longitudes. The observed distribution was compared with the results of the spectrometric observations made with the Voyager and the International Ultraviolet Explorer missions. Images concerning the Io surface albedo and Saturn's disk and ring's reflectivity were also obtained.

Gerard, Jean-Claude

1994-01-01

160

Theory of Planetary Atmospheres: An Introduction to Their Physics and Chemistry  

Microsoft Academic Search

This textbook describes the entire field of atmospheric physics for Earth and the planets, from surface levels to just below the magnetospheres. The protean talents of the authors have led to seven chapters: vertical structure of an atmosphere; hydrodynamics of atmospheres; chemistry and dynamics of Earth's stratosphere; planetary astronomy; ionospheres; airglows, auroras, and aeronomy; and finally, stability of planetary atmospheres.

C. Muller

1987-01-01

161

Gas chromatographic concepts for the analysis of planetary atmospheres  

NASA Technical Reports Server (NTRS)

Over the last few years, new gas chromatographic (GC) concepts were developed for use on board spacecraft or any other restricted environments for determining the chemical composition of the atmosphere and surface material of various planetary bodies. Future NASA Missions include an entry probe that will be sent to Titan and various spacecraft that will land on Mars. In order to be able to properly respond to the mission science requirements and physical restrictions imposed on the instruments by these missions, GC analytical techniques are being developed. Some of these techniques include hardware and mathematical techniques that will improve GC sensitivity and increase the sampling rate of a GC descending through a planetary atmosphere. The technique of Multiplex Gas Chromatography (MGC) is an example of a technique that was studied in a simulated Titan atmosphere. In such an environment, the atmospheric pressure at instrument deployment is estimated to be a few torr. Thus, at such pressures, the small amount of sample that is acquired might not be enough to satisfy the detection requirements of the gas chromatograph. In MGC, many samples are pseudo-randomly introduced to the chromatograph without regard to elution of preceding components. The resulting data is then reduced using mathematical techniques such as cross-correlation of Fourier Transforms. Advantages realized from this technique include: improvement in detection limits of several orders of magnitude and increase in the number of analyses that can be conducted in a given period of time. Results proving the application of MGC at very low pressures emulating the same atmospheric pressures that a Titan Probe will encounter when the instruments are deployed are presented. The sample used contained hydrocarbons that are expected to be found in Titan's atmosphere. In addition, a new selective modulator was developed to monitor water under Martian atmospheric conditions. Since this modulator is selective only to water, the need for a GC column is eliminated. This results in further simplification of the instrument.

Valentin, J. R.; Cullers, D. K.; Hall, K. W.; Krekorian, R. L.; Phillips, J. B.

1991-01-01

162

AN ANALYTIC RADIATIVE-CONVECTIVE MODEL FOR PLANETARY ATMOSPHERES  

SciTech Connect

We present an analytic one-dimensional radiative-convective model of the thermal structure of planetary atmospheres. Our model assumes that thermal radiative transfer is gray and can be represented by the two-stream approximation. Model atmospheres are assumed to be in hydrostatic equilibrium, with a power-law scaling between the atmospheric pressure and the gray thermal optical depth. The convective portions of our models are taken to follow adiabats that account for condensation of volatiles through a scaling parameter to the dry adiabat. By combining these assumptions, we produce simple, analytic expressions that allow calculations of the atmospheric-pressure-temperature profile, as well as expressions for the profiles of thermal radiative flux and convective flux. We explore the general behaviors of our model. These investigations encompass (1) worlds where atmospheric attenuation of sunlight is weak, which we show tend to have relatively high radiative-convective boundaries; (2) worlds with some attenuation of sunlight throughout the atmosphere, which we show can produce either shallow or deep radiative-convective boundaries, depending on the strength of sunlight attenuation; and (3) strongly irradiated giant planets (including hot Jupiters), where we explore the conditions under which these worlds acquire detached convective regions in their mid-tropospheres. Finally, we validate our model and demonstrate its utility through comparisons to the average observed thermal structure of Venus, Jupiter, and Titan, and by comparing computed flux profiles to more complex models.

Robinson, Tyler D. [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Catling, David C., E-mail: robinson@astro.washington.edu [Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195-1310 (United States)

2012-09-20

163

Extrasolar Planet Orbits and Eccentricities  

E-print Network

The known extrasolar planets exhibit many interesting and surprising features--extremely short-period orbits, high-eccentricity orbits, mean-motion and secular resonances, etc.--and have dramatically expanded our appreciation of the diversity of possible planetary systems. In this review we summarize the orbital properties of extrasolar planets. One of the most remarkable features of extrasolar planets is their high eccentricities, far larger than seen in the solar system. We review theoretical explanations for large eccentricities and point out the successes and shortcomings of existing theories.

Scott Tremaine; Nadia L. Zakamska

2003-12-01

164

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

165

Experimental Measurement of Dissociative Recombination Relevant to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Dissociative recombination (DR) is the primary mechanism for electron loss in ionized, low-pressure molecular gases and plasmas, such as planetary ionospheres. Through the use of heavy ion storage rings, there has been considerable progress in recent years in characterizing both the cross sections and the products produced by DR reactions. DR can in principle be strongly dependent on specific rotational, vibrational, and electronic states of the ion, but current work has allowed only investigating ground state species or uncharacterized internal state distributions. Above 150 km in the CO2 atmosphere of Venus, the oxygen molecular ion is formed by the reactions: h? + CO2 -> O+ + O2 and O+ + CO2 -> O2+(v) + CO, where >60% of the O2+(v) is produced in vibrationally excited levels. We report here the first experimental determination of cross sections and products produced in the DR of O2+(v) in its ground state vibrational levels v = 0, 1, 2, 3, and 4. In particular, our measurements show substantial variations (factors of 5) in the DR cross sections among these low levels. Our measurements were made at CRYRING using a variable pressure electron-impact ion source with the ion populations characterized by dissociative charge transfer in cesium vapor. This work is partially supported by the NASA Planetary Atmospheres Program under grant NAG5-11173.

Cosby, P. C.; Peterson, J. R.; Huestis, D. L.; Petrignani, A.; van der Zande, W.; Larsson, M.; Thomas, R.; Hellberg, F.

2003-05-01

166

Magnetic Field Influence on Atmospheric Escape and Planetary Evolution  

NASA Astrophysics Data System (ADS)

Planetary magnetic fields are maintained by a convective dynamo within the deep interior but their influence extends all the way up to the magnetopause, where the solar wind is deflect around the planet. The presence of a magnetic field is thought to influence the atmosphere-solar wind interaction in a variety of ways, but there is no clear consensus as to whether it impedes or facilitates volatile loss to space. Escape of planetary atmospheres to space is of central importance to studying the evolution of planetary climates, volatile exchange with the interior, and interaction with the space environment. Out of the terrestrial planets Earth has by far the largest surface hydrogen inventory (mainly in the form of liquid water) and furthest magnetopause at ~10 Earth radii. Evidence from volatile concentrations and isotopic ratios imply that Mars and Venus have both lost a significant amount of H over their history, and have maintained little to no magnetic barrier, respectively, to hold off the erosive solar wind. Venus is a particularly interesting case because it is most similar to Earth in mass and density, yet has no detectable magnetic field and an isotopic D/H ratio that implies the loss of a significant amount of water in the past. Is the decline of Venus' dynamo related to the loss of hydrogen from its atmosphere? Is the stability of Earth's unusually large volatile reservoir over billions of years related to the presence of a strong magnetic field over that period of time? We explore conditions under which the presence of a magnetic barrier at the top of the atmosphere may operate as an additional limit to escape. We derive a model for magnetic field limited escape that depends on the terrestrial number density, area, scale height, and loss time scale at the magnetopause. This model predicts rapid escape when magnetic field is weak and magnetopause altitude is low, and a decrease in escape as magnetic field strength increases. This coupling between field strength and escape may be part of a larger negative feedback mechanism that stabilizes climate, tectonic regime, and dynamo action. Such a feedback is possible by a coupling between surface temperature and tectonic regime. Numerical simulations of mantle convection with damage demonstrate that low surface temperature stagnates grain growth and promotes surface convection, which increases the core cooling rate and magnetic field intensity. Therefore, magnetic limited escape may be part of a whole planet coupling that has stabilized Earth's volatile reservoir, surface tectonics, and magnetic field.

Driscoll, P. E.; Bercovici, D.

2012-12-01

167

The HARPS search for southern extra-solar planets XXXV. Planetary systems and stellar activity of the M dwarfs GJ 3293, GJ 3341, and GJ 3543  

E-print Network

Context. Planetary companions of a fixed mass induce larger amplitude reflex motions around lower-mass stars, which helps make M dwarfs excellent targets for extra-solar planet searches. State of the art velocimeters with $\\sim$1m/s stability can detect very low-mass planets out to the habitable zone of these stars. Low-mass, small, planets are abundant around M dwarfs, and most known potentially habitable planets orbit one of these cool stars. Aims. Our M-dwarf radial velocity monitoring with HARPS on the ESO 3.6m telescope at La Silla observatory makes a major contribution to this sample. Methods. We present here dense radial velocity (RV) time series for three M dwarfs observed over $\\sim5$ years: GJ 3293 (0.42M$_\\odot$), GJ 3341 (0.47M$_\\odot$), and GJ 3543 (0.45M$_\\odot$). We extract those RVs through minimum $\\chi^2$ matching of each spectrum against a high S/N ratio stack of all observed spectra for the same star. We then vet potential orbital signals against several stellar activity indicators, to dis...

Astudillo-Defru, N; Delfosse, X; Segransan, D; Forveille, T; Bouchy, F; Gillon, M; Lovis, C; Mayor, M; Neves, V; Pepe, F; Perrier, C; Queloz, D; Rojo, P; Santos, N C; Udry, S

2014-01-01

168

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

169

Building a "big picture" of planetary atmospheres dynamics  

NASA Astrophysics Data System (ADS)

Together with Saturn's large satellite, Titan, Earth, Mars and Venus provide four clear and increasingly well-studied examples of terrestrial-style planetary circulation systems under quite different parametric conditions. Clear trends in behaviour can be seen between these planets, especially contrasting the slowly and rapidly rotating bodies, suggesting some analogies with the studies of flow transitions and bifurcations in laboratory flow systems such as the rotating, baroclinic annulus experiment[1,2], and other simple models. This approach to comparative studies comes especially naturally to dynamicists, to whom the ability of even relatively simple, nonlinear, dynamical systems to exhibit radically different behaviours, punctuated by well characterized bifurcations as control parameters are varied, is familiar and commonplace. But is this analogy more than superficial? Does it suggest the possibility of an overarching the-oretical framework or even prototype model that could offer useful quantitative predictions of atmospheric structure, circulation and transport across a wide range of planetary parameters? If so, what are the critical parameters upon which key dynamical properties of the circulation depend? Can comparisons between the Earth and other planetary bodies provide useful insights into the Earth's circulation and climate? These questions come into even sharper focus in the light of the recent discoveries of terrestrial-style planets around other stars, about which obser-vational measurements can provide only very basic, globally integrated parameters. It is vital, therefore, to exploit and understand as fully as possible the available models of atmospheric circulation systems amenable to detailed study within our Solar System, their common aspects and key differences, and to confront them with detailed observations and measurements. In this contribution we examine ways in which numerical models of atmospheric circulation can be used to construct and explore relatively simple parameter spaces for atmospheric circulation systems, along similar lines to what is commonly done in the laboratory, without the need to compute many of the details specific to individual planetary composition, topography etc. Trends observed in such studies indicate that a common theoretical framework can account for many of the basic differences and similarities between the terrestrial planets in the Solar System, although this approach is still in its infancy. Such an approach can even enable simple predictions to be made of the style and intensity of circulation for planets (e.g. around other stars) yet to be discovered. Future work along similar lines, however, will need to take into account a wider range of possibilities than has been studied systematically hitherto, including the full range of planetary obliquity and seasonal variations, ratios of dynamical and radiative timescales, diurnal cycles and tidally-locked states. [1] R. Hide and P. J. Mason. Adv. in Phys., 24:47-99, 1975 [2] Wordsworth, R. D., Read, P. L. Yamazaki, H. Y. (2008) Phys. Fluids, 20, 126602

Read, Peter; Wang, Yixiong

170

Theory of planetary atmospheres: an introduction to their physics and chemistry /2nd revised and enlarged edition/  

SciTech Connect

Theoretical models of planetary atmospheres are characterized in an introductory text intended for graduate physics students and practicing scientists. Chapters are devoted to the vertical structure of an atmosphere; atmospheric hydrodynamics; the chemistry and dynamics of the earth stratosphere; planetary astronomy; ionospheres; airglows, auroras, and aeronomy; and the stability of planetary atmospheres. Extensive graphs, diagrams, and tables of numerical data are provided.

Chamberlain, J.W.; Hunten, D.M.

1987-01-01

171

Theory of planetary atmospheres: an introduction to their physics and chemistry \\/2nd revised and enlarged edition  

Microsoft Academic Search

Theoretical models of planetary atmospheres are characterized in an introductory text intended for graduate physics students and practicing scientists. Chapters are devoted to the vertical structure of an atmosphere; atmospheric hydrodynamics; the chemistry and dynamics of the earth stratosphere; planetary astronomy; ionospheres; airglows, auroras, and aeronomy; and the stability of planetary atmospheres. Extensive graphs, diagrams, and tables of numerical data

Joseph W. Chamberlain; Donald M. Hunten

1987-01-01

172

Data Assimilation and Data Fusion for Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

The overarching goal of this Cooperative Agreement was to develop a model and procedures for the data assimilation of planetary spacecraft atmospheric observations. Data assimilation - in its application to weather analysis and prediction - is the process of finding an initial state of the meteorological variables (winds, temperatures, pressures, etc.) of an atmosphere, which, when propagated forward in time using a deterministic general circulation model, reproduces all of the available observations over that time to within the measurement and computational errors. With this definition, data assimilation is seen to be a natural extension of well-known least-squares minimization techniques. The primary complication arises from the scale of the problem: For the Martian atmosphere with the available nadir-viewing Thermal Emission Spectrometer data from Mars Global Surveyor, approximately 1,000,000 individual measurements of channel radiances (in the 15-micrometer region, where these radiances relate directly to the surface and atmospheric temperature) were made per day. A suitable general circulation model for dealing with this data set has on the order of 20,000 independent variables. After some spatial and temporal averaging of the data - which provides a necessary statistical estimate of the representativeness of the measurements, a crucial issue in data assimilation - the problem reduces in scale to the solution of approximately 50,000 equations for the 20,000 variables.

Houben, Howard

2005-01-01

173

Survey for transiting extrasolar planets in stellar systems: Stellar and planetary content of the open cluster NGC 1245  

Microsoft Academic Search

An investigation into the stellar and planetary content of the open cluster NGC 1245 using BVI photometry from the MDM 1.3m and 2.4m telescopes. Color magnitude diagram observations provide the basis for the exploration of the cluster stellar content. Based on detailed isochrone fitting, I find NGC 1245 has a slightly sub-solar metallicity, [Fe\\/H] = -0.05 +\\/- 0.03 (statistical) +\\/-

Christopher J. Burke

2005-01-01

174

Meteoric Ablation in Planetary Atmospheres and the Laboratory  

NASA Astrophysics Data System (ADS)

The chemistry and energetics of all planetary atmospheres are influenced by the influx of interplanetary dust particles and the layers of material deposited through ablation. Even for the well-monitored terrestrial atmosphere, the amount of the incoming cosmic material remains uncertain. Radar and lidar systems make valuable measurements of the incoming particles and the atomic and ion layers, as well as the particulate remnants. However, the measurement methods are biased due to the wide ranges of mass, velocity and composition of the incoming material. Further ambiguity is introduced through the uncertainty of some of the ablation parameters, e.g., the ionization probability. Laboratory measurements can be used to benchmark the ablation of different materials over a wide range of speeds. In this talk, we give and overview of the state of the art ablation models and the applicability of laboratory measurements to verify these models and how fundamental quantities can be measured, including ionization and luminous efficiencies. There are upcoming mission to Mars (MAVEN) and Pluto (New Horizons) that are expected to return data on the distribution of the ablated material and the effect on their atmospheres. These data could potentially be used to further constrain the ablation processes and the parameters used.

Sternovsky, Z.; Robertson, S. H.; Horanyi, M.; Szalay, J.

2013-12-01

175

Construction of an advanced software tool for planetary atmospheric modeling  

NASA Technical Reports Server (NTRS)

Scientific model-building can be a time intensive and painstaking process, often involving the development of large complex computer programs. Despite the effort involved, scientific models cannot be distributed easily and shared with other scientists. In general, implemented scientific models are complicated, idiosyncratic, and difficult for anyone but the original scientist/programmer to understand. We propose to construct a scientific modeling software tool that serves as an aid to the scientist in developing, using and sharing models. The proposed tool will include an interactive intelligent graphical interface and a high-level domain-specific modeling language. As a testbed for this research, we propose to develop a software prototype in the domain of planetary atmospheric modeling.

Friedland, Peter; Keller, Richard M.; Mckay, Christopher P.; Sims, Michael H.; Thompson, David E.

1993-01-01

176

Construction of an advanced software tool for planetary atmospheric modeling  

NASA Technical Reports Server (NTRS)

Scientific model-building can be a time intensive and painstaking process, often involving the development of large complex computer programs. Despite the effort involved, scientific models cannot be distributed easily and shared with other scientists. In general, implemented scientific models are complicated, idiosyncratic, and difficult for anyone but the original scientist/programmer to understand. We propose to construct a scientific modeling software tool that serves as an aid to the scientist in developing, using and sharing models. The proposed tool will include an interactive intelligent graphical interface and a high-level domain-specific modeling language. As a test bed for this research, we propose to develop a software prototype in the domain of planetary atmospheric modeling.

Friedland, Peter; Keller, Richard M.; Mckay, Christopher P.; Sims, Michael H.; Thompson, David E.

1992-01-01

177

Hydrogen atom initiated chemistry. [chemical evolution in planetary atmospheres  

NASA Technical Reports Server (NTRS)

H Atoms have been created by the photolysis of H2S. These then initiated reactions in mixtures involving acetylene-ammonia-water and ethylene-ammonia-water. In the case of the acetylene system, the products consisted of two amino acids, ethylene and a group of primarily cyclic thio-compounds, but no free sulfur. In the case of the ethylene systems, seven amino acids, including an aromatic one, ethane, free sulfur, and a group of solely linear thio-compounds were produced. Total quantum yields for the production of amino acids were about 3 x 10 to the -5th and about 2 x 10 to the -4th with ethylene and acetylene respectively as carbon substrates. Consideration is given of the mechanism for the formation of some of the products and implications regarding planetary atmosphere chemistry, particularly that of Jupiter, are explored.

Hong, J. H.; Becker, R. S.

1979-01-01

178

Abundances of refractory elements in the atmospheres of stars with extrasolar planets  

Microsoft Academic Search

Aims.This work presents a uniform and homogeneous study of chemical abundances of refractory elements in 101 stars with and 93 without known planetary companions. We carry out an in-depth investigation of the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al. The new comparison sample, spanning the metallicity range -0.70< [Fe\\/H]< 0.50, fills the

G. Gilli; G. Israelian; A. Ecuvillon; N. C. Santos; M. Mayor

2006-01-01

179

The HARPS search for southern extrasolar planets. XXIII. 8 planetary companions to low-activity solar-type stars  

E-print Network

In this paper, we present our HARPS radial-velocity data for eight low-activity solar-type stars belonging to the HARPS volume-limited sample: HD6718, HD8535, HD28254, HD290327, HD43197, HD44219, HD148156, and HD156411. Keplerian fits to these data reveal the presence of low-mass companions around these targets. With minimum masses ranging from 0.58 to 2.54 MJup, these companions are in the planetary mass domain. The orbital periods of these planets range from slightly less than one to almost seven years. The eight orbits presented in this paper exhibit a wide variety of eccentricities: from 0.08 to above 0.8.

Naef, Dominique; Curto, Gaspare Lo; Bouchy, Francois; Lovis, Christophe; Moutou, Claire; Benz, Willy; Pepe, Francesco; Queloz, Didier; Santos, Nuno C; Segransan, Damien; Udry, Stephane; Bonfils, Xavier; Delfosse, Xavier; Forveille, Thierry; Hebrard, Guillaume; Mordasini, Christoph; Perrier, Christian; Boisse, Isabelle; Sosnowska, Danuta

2010-01-01

180

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

181

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

182

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets. II. Dust-induced Collisional Ionization  

Microsoft Academic Search

Observations have shown that continuous radio emission and also sporadic Halpha 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

Ch. Helling; M. Jardine; F. Mokler

2011-01-01

183

Photometric Techniques Using Small College Research Instruments for Study of the Extrasolar Planetary Transits of HD 209458  

NASA Astrophysics Data System (ADS)

We present the results of a program to develop techniques that enable high-resolution photometric measurements using modest research instruments available to small colleges, and then demonstrate those techniques in a pilot photometric project. Using a 25cm Schmidt-Cassegrain telescope and SBIG ST7E CCD camera, we develop techniques that enabled milli-magnitude photometric resolution. The pilot project studied five transits of the recently discovered gas giant planet orbiting HD 209458. We measured a flux drop of 1.46+/-0.17% during the transit which corresponds to a planetary diameter of 1.39+/-0.14 RJup, a transit period of 2h 48min+/-21min, and planet orbital inclination of 87.6+/-1.3°. We determined the orbital period as 3.5234+/-0.0026 days. These results agree well with other studies which used professional grade research instruments. We suggest a number of other challenging photometric research areas suitable for graduate and undergraduate investigation using equipment common to many small colleges.

Hudgins, David W.; Filipovi?, Miroslav D.

184

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. IV. THE EFFECT OF COSMIC RAYS  

SciTech Connect

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 10{sup 6} 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{sub eff} = 1500 K, and two example giant gas planets (T{sub eff} = 1000 K, 1500 K). For the model brown dwarf atmosphere, the electron fraction is enhanced significantly by cosmic rays when the pressure p{sub gas} < 10{sup -2} bar. Our example giant gas planet atmosphere suggests that the cosmic ray enhancement extends to 10{sup -4}-10{sup -2} bar, depending on the effective temperature. For the model atmosphere of the example giant gas planet considered here (T{sub eff} = 1000 K), cosmic rays bring the degree of ionization to f{sub e} {approx}> 10{sup -8} when p{sub gas} < 10{sup -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., E-mail: pr33@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom)

2013-09-10

185

Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown Dwarfs  

NASA Technical Reports Server (NTRS)

In L-dwarfs and T-dwarfs the resonance lines of sodium and potassium are so profoundly pressure-broadened that their wings extend several hundred nanometers from line center. With accurate knowledge of the line profiles as a function of temperature and pressure: such lines can prove to be valuable diagnostics of the atmospheres of such objects. We have initiated a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Although potassium and sodium are the alkali species of most interest in the atmospheres of cool brown dwarfs and extrasolar giant planets, some of our theoretical focus this year has involved the calculation of pressure-broadening of lithium resonance lines by He, as a test of a newly developed suite of computer codes. In addition, theoretical calculations have been carried out to determine the leading long range van der Waals coefficients for the interactions of ground and excited alkali metal atoms with helium atoms, to within a probable error of 2%. Such data is important in determining the behavior of the resonance line profiles in the far wings. Important progress has been made on the experimental aspects of the program since the arrival of a postdoctoral fellow in September. A new absorption cell has been designed, which incorporates a number of technical improvements over the previous cell, including a larger cell diameter to enhance the signal, and fittings which allow for easier cleaning, thereby significantly reducing the instrument down-time.

Kirby, Kate; Babb, J.; Yoshino, K.

2004-01-01

186

An automated method for tracking clouds in planetary atmospheres  

NASA Astrophysics Data System (ADS)

We present an automated method for cloud tracking which can be applied to planetary images. The method is based on a digital correlator which compares two or more consecutive images and identifies patterns by maximizing correlations between image blocks. This approach bypasses the problem of feature detection. Four variations of the algorithm are tested on real cloud images of Jupiter's white ovals from the Galileo mission, previously analyzed in Vasavada et al. [Vasavada, A.R., Ingersoll, A.P., Banfield, D., Bell, M., Gierasch, P.J., Belton, M.J.S., Orton, G.S., Klaasen, K.P., Dejong, E., Breneman, H.H., Jones, T.J., Kaufman, J.M., Magee, K.P., Senske, D.A. 1998. Galileo imaging of Jupiter's atmosphere: the great red spot, equatorial region, and white ovals. Icarus, 135, 265, doi:10.1006/icar.1998.5984]. Direct correlation, using the sum of squared differences between image radiances as a distance estimator (baseline case), yields displacement vectors very similar to this previous analysis. Combining this distance estimator with the method of order ranks results in a technique which is more robust in the presence of outliers and noise and of better quality. Finally, we introduce a distance metric which, combined with order ranks, provides results of similar quality to the baseline case and is faster. The new approach can be applied to data from a number of space-based imaging instruments with a non-negligible gain in computing time.

Luz, D.; Berry, D. L.; Roos-Serote, M.

2008-05-01

187

Incorporation of the planetary boundary layer in atmospheric models  

NASA Technical Reports Server (NTRS)

The topics discussed include the following: perspectives on planetary boundary layer (PBL) measurements; current problems of PBL parameterization in mesoscale models; and convective cloud-PBL interactions.

Moeng, Chin-Hoh; Wyngaard, John; Pielke, Roger; Krueger, Steve

1993-01-01

188

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION  

SciTech Connect

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{sup –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{sup –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, H{sub 2}, 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.; Rimmer, P. B. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Diver, D. A., E-mail: craig.stark@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

2013-10-10

189

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

190

Simulated planetary wave-tide interactions in the atmosphere of Mars  

NASA Astrophysics Data System (ADS)

This study is a first attempt to simulate the nonlinear interactions between planetary waves and tides in the atmosphere of Mars and to examine the consequences of the secondary waves that result from these interactions. Recent analysis of aerobraking densities show clear signatures of secondary waves produced by the modulation of tides by planetary waves. The vertically propagating secondary waves serve to modulate longitudinal density structures (due to nonmigrating tides) at planetary wave periods, even in the local absence of planetary waves. In this parametric study, using a general circulation model of Mars, we determine the most important waves produced by these interactions and quantify their induced variability at aerobraking altitudes.

Moudden, Y.; Forbes, J. M.

2011-01-01

191

Problem of photochemical equilibrium of ozone in planetary atmospheres: Ozone distribution in the lower atmosphere of Mars  

NASA Technical Reports Server (NTRS)

The inherent errors of applying terrestrial atmospheric ozone distribution studies to the atmosphere of other planets are discussed. Limitations associated with some of the earlier treatments of photochemical equilibrium distributions of ozone in planetary atmospheres are described. A technique having more universal application is presented. Ozone concentration profiles for the Martian atmosphere based on the results of the Mariner 4 radio occultation experiment and the more recent results with Mariner 6 and Mariner 7 have been calculated using this approach.

Grams, G. W.; SHARDANAND

1972-01-01

192

REVIEWS OF TOPICAL PROBLEMS: Generation of large-scale eddies and zonal winds in planetary atmospheres  

NASA Astrophysics Data System (ADS)

The review deals with a theoretical description of the generation of zonal winds and vortices in a turbulent barotropic atmosphere. These large-scale structures largely determine the dynamics and transport processes in planetary atmospheres. The role of nonlinear effects on the formation of mesoscale vortical structures (cyclones and anticyclones) is examined. A new mechanism for zonal wind generation in planetary atmospheres is discussed. It is based on the parametric generation of convective cells by finite-amplitude Rossby waves. Weakly turbulent spectra of Rossby waves are considered. The theoretical results are compared to the results of satellite microwave monitoring of the Earth's atmosphere.

Onishchenko, O. G.; Pokhotelov, O. A.; Astafieva, N. M.

2008-06-01

193

The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs  

E-print Network

The last few years has seen a dramatic increase in the number of exoplanets known and in the range of methods for characterising their atmospheric properties. At the same time, new discoveries of increasingly cooler brown dwarfs have pushed down their temperature range which now extends down to Y-dwarfs of dwarfs are relatively well understood, but some problems remain, in particular the behavior of clouds at the L/T transition. Observational data for exoplanet atmosphere characterization is largely limited to giant exoplanets that are hot because they are near to their star (hot Jupiters) or because they are young and still cooling. For these planets there is good evidence for the presence of CO and H2O absorptions in the IR. Sodium absorption is observed in a number of objects. Reflected light measurements show that some giant exo...

Bailey, Jeremy

2014-01-01

194

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

195

Extrasolar Planets & The Power of the Dark Side  

SciTech Connect

It is only in the last decade that we have direct evidence for planets orbiting nearby Sun-like stars. If such planets happen to pass in front of their stars, we are presented with a golden opportunity to learn about the nature of these objects. Measurements of the dimming of starlight and gravitational wobble allow us to derive the planetary radius and mass, and, by inference, its composition. Recently, we used the Hubble Telescope to detect and study the atmosphere of an extrasolar planet for the first time. I will describe what we have learned about these planets 

Dr. David Charbonneau

2009-04-24

196

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

197

Influence of atmospheric turbulence on planetary transceiver laser ranging  

NASA Astrophysics Data System (ADS)

In this paper we investigate the influence of atmospheric turbulence on the performance of the uplink of a planetary transceiver laser ranging system using a single photon detector. We numerically combine the influence of turbulence in the mean intensity profile variations, scintillation, beam-wander induced pointing errors and stochastic time-of-flight variations, using the Hufnagel-Valley turbulence profile to model the ground turbulence behavior. We map the intensity variations due to turbulence to variations in the probability distribution of the arrival time of the 1st photon in a laser pulse, which influences the range measurement error probability distribution. The turbulence models are applied to assess the influence on single-pass range accuracy and precision statistics, as well as the parameter estimation quality of a Phobos Laser Ranging (PLR) mission. The difference in range measurement error between weak and strong turbulence is 3-4 mm in a PLR concept. This indicates that turbulence is a potentially important contributor to the error budget of interplanetary laser ranging missions, which aim at mm-level accuracy and precision. The single-shot precision is weakly influenced by turbulence, but strong turbulence is found to cause a strong decrease in detected pulse fraction, reducing normal point precision. We show that a trade-off between range accuracy and precision must be made when selecting laser system parameters, considerations for which are influenced by atmospheric turbulence effects. By consistently operating at the single-photon signal strength level, accuracy variations can be largely removed, at the expense of normal point precision, due to the reduced detection probability. We perform parameter estimation of Phobos initial state and observation biases using simulated measurements with and without turbulence, using a daily periodic turbulence strength model. We show that the parameter estimation quality is degraded significantly below that of the turbulence-free case only in the presence of strong turbulence. This shows the existence of a limit of ground turbulence strength below which its influence on parameter estimation becomes negligible.

Dirkx, D.; Noomen, R.; Prochazka, I.; Bauer, S.; Vermeersen, L. L. A.

2014-12-01

198

Analytic theory of orbit contraction and ballistic entry into planetary atmospheres  

NASA Technical Reports Server (NTRS)

A space object traveling through an atmosphere is governed by two forces: aerodynamic and gravitational. On this premise, equations of motion are derived to provide a set of universal entry equations applicable to all regimes of atmospheric flight from orbital motion under the dissipate force of drag through the dynamic phase of reentry, and finally to the point of contact with the planetary surface. Rigorous mathematical techniques such as averaging, Poincare's method of small parameters, and Lagrange's expansion, applied to obtain a highly accurate, purely analytic theory for orbit contraction and ballistic entry into planetary atmospheres. The theory has a wide range of applications to modern problems including orbit decay of artificial satellites, atmospheric capture of planetary probes, atmospheric grazing, and ballistic reentry of manned and unmanned space vehicles.

Longuski, J. M.; Vinh, N. X.

1980-01-01

199

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

NASA Technical Reports Server (NTRS)

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 atmospheric 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. 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. The goal of this investigation was 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.

1992-01-01

200

Atom Resonance Lines for Modeling Atmosphere: Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown Dwarfs  

NASA Technical Reports Server (NTRS)

We report on progress made in a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Accurate knowledge of the line profiles of Na and K as a function of temperature and pressure will allow such lines to serve as valuable diagnostics of the atmospheres of brown dwarfs and extra-solar giant planets. A new experimental apparatus has been designed, built and tested over the past year, and we are poised to begin collecting data on the first system of interest, the potassium resonance lines perturbed by collisions with helium. On the theoretical front, calculations of line-broadening due to sodium collisions with helium are nearly complete, using accurate molecular potential energy curves and transition moments just recently computed for this system. In addition we have completed calculations of the three relevant potential energy curves and associated transition moments for K - He, using the MOLPRO quantum chemistry codes. Currently, calculations of the potential surfaces describing K-H2 are in progress.

Hasan, Hashima (Technical Monitor); Kirby, K.; Babb, J.; Yoshino, K.

2005-01-01

201

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

202

Meteoric Material - One of the Least Explored Components of Planetary Atmospheres  

Microsoft Academic Search

Interplanetary dust particles (IDPs) continuously impact all the planets and their satellites in the solar system. In all planetary atmospheres IDPs leave their imprint as aerosols or smoke particles that are left behind when the IDPs do not ablate completely or when the ablated vapors recondense. In addition, in all atmospheres they produce ionization layers comprised of metallic ions, predominantly

J. I. Moses; J. M. Grebowsky; W. D. Pesnell; A. L. Weisman

2001-01-01

203

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

204

Transmission of planetary wave effects to the upper atmosphere through eddy diffusion modulation  

NASA Astrophysics Data System (ADS)

Past observations have shown that the effects of planetary waves can travel beyond their dissipation region and into the thermosphere and ionosphere. One possible mechanism through which this event can occur is the modulation of turbulent mixing near the turbopause. Because turbulent mixing in the mesosphere-lower thermosphere is strongly dependent on the amount of wave dissipation, planetary wave filtering of gravity waves from below can indirectly modulate the amount of turbulent mixing. This study uses the NCAR TIE-GCM to investigate how this mechanism induces variability in upper atmospheric composition and density. It is shown that varying the amount of turbulent mixing at discrete planetary wave periods induces similar periodicities in neutral and electron density. This process is driven by species diffusive flux through isobaric (constant pressure) levels, resulting in atmospheric contraction or expansion. Results also indicate that the mechanism studied has a wave frequency dependence and is most effective for long period planetary waves.

Nguyen, Vu; Palo, S. E.

2014-09-01

205

When Extrasolar Planets Transit Their Parent Stars  

E-print Network

When extrasolar planets are observed to transit their parent stars, we are granted unprecedented access to their physical properties. It is only for transiting planets that we are permitted direct estimates of the planetary masses and radii, which provide the fundamental constraints on models of their physical structure. In particular, precise determination of the radius may indicate the presence (or absence) of a core of solid material, which in turn would speak to the canonical formation model of gas accretion onto a core of ice and rock embedded in a protoplanetary disk. Furthermore, the radii of planets in close proximity to their stars are affected by tidal effects and the intense stellar radiation. As a result, some of these "hot Jupiters" are significantly larger than Jupiter in radius. Precision follow-up studies of such objects (notably with the space-based platforms of the Hubble and Spitzer Space Telescopes) have enabled direct observation of their transmission spectra and emitted radiation. These data provide the first observational constraints on atmospheric models of these extrasolar gas giants, and permit a direct comparison with the gas giants of the Solar system. Despite significant observational challenges, numerous transit surveys and quick-look radial velocity surveys are active, and promise to deliver an ever-increasing number of these precious objects. The detection of transits of short-period Neptune-sized objects, whose existence was recently uncovered by the radial-velocity surveys, is eagerly anticipated. Ultra-precise photometry enabled by upcoming space missions offers the prospect of the first detection of an extrasolar Earth-like planet in the habitable zone of its parent star, just in time for Protostars and Planets VI.

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

2006-03-14

206

Observations of Extrasolar Planet Transits: What's next?  

NASA Astrophysics Data System (ADS)

Transits of extrasolar planets are a goldmine for our understanding of the physical nature of planets beyond the Solar System. Measurements of radii from transit observations combined with mass determinations from radial velocity spectroscopy, or transit timing variations, have provided the first indications to the planetary composition and interior structure. It turns out that planets show a much richer diversity than found in our own planetary system, considering e.g. the so-called 'super-Earths', 'mini-Neptunes', and inflated giant planets. Transiting exoplanets also allow for spectroscopic observations of their atmospheres, either during transit or near secondary eclipse. Exoplanets showing transits have therefore been identified as key observables, not only for planet detection, but in particular for investigating further planetary nature. As a result, a new generation of instruments (space- and groundbased) for exoplanet transit observations is already in the construction phase and is planned for the near future. Most of these target specifically stars bright enough for spectroscopic follow-up observations, a èlesson learned' from past transit surveys. A clear goal for future investigations of habitable planets is the detection and characterization of terrestrial planets which potentially could harbor life. This talk will review the status and in particular the future of transit observations, with a focus on rocky planets in the habitable zone of their host stars.

Rauer, H.

2014-03-01

207

Adapting the GISS Climate GCM to Model Extra-Solar Climate Regimes  

NASA Astrophysics Data System (ADS)

Hundreds of extra-solar planets have been discovered by NASA's Kepler mission, some potentially habitable, most exhibiting extremes in climate beyond current modeling experience. Zero-order assessment of the stellar type and the planet's distance from the star serves to identify the ballpark of whether silicon dioxide is likely to be in gaseous or liquid phase in the planet's atmosphere, or a part of the solid planetary ground surface. A lot of first-order modeling would involve assessing the chemical limitations to establish the likely chemical composition of the planetary atmosphere. For a more detailed analysis of the prevailing climate on an extra-solar planet a 3-D global climate model would be required. We begin the Extra-Solar Climate Model development by starting the with GISS Climate GCM by having key model parameters be expressed in physics based terms rather than Earth specific parameters. Examples of such key parameters are: the Planet's mass and radius, mass and composition of the atmosphere, Star-Planet distance, rotation rate and orbital parameters, stellar spectral distribution, land topography, and land-ocean distribution. These are parameters that are more or less straight forward to redefine for extra-solar conditions that are not greatly different for what may be considered as the ';habitable' zone. We present extreme climate simulations ranging from snowball Earth conditions to near-runaway greenhouse conditions. The objective of this modeling study is the development of a more physically based climate model that will be adaptable for assessing habitable climate regimes on newly discovered extra-solar planets, and will also facilitate the study terrestrial climate system analysis in paleoclimate applications.

Lacis, A. A.

2013-12-01

208

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

NASA Technical Reports Server (NTRS)

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 atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorping properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or 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 measurement of the microwave properties of atmospheric gases under simulated conditions for the outer planets were conducted. Results of these measurements are discussed.

Steffes, Paul G.

1987-01-01

209

Can We Probe the Atmospheric Composition of an Extrasolar Planet from its Reflection Spectrum in a High-Magnification Microlensing Event?  

E-print Network

We revisit the possibility of detecting an extrasolar planet around a background star as it crosses the fold caustic of a foreground binary lens. During such an event, the planet's flux can be magnified by a factor of ~100 or more. The detectability of the planet depends strongly on the orientation of its orbit relative to the caustic. If the source star is inside the inter-caustic region, detecting the caustic-crossing planet is difficult against the magnified flux of its parent star. In the more favorable configuration, when the star is outside the inter-caustic region when the planet crosses the caustic, a close-in Jupiter-like planet around a Sun-like star at a distance of 8 kpc is detectable in 8-minute integrations with a 10m telescope at maximal S/N~15 for phase angle ~10 degrees. In this example, we find further that the presence of methane, at its measured abundance in Jupiter, and/or water, sodium and potassium, at the abundances expected in theoretical atmosphere models of close-in Jupiters, could be inferred from a non-detection of the planet in strong broad absorption bands at 0.6-1.4 microns caused by these compounds, accompanied by a S/N~10 detection in adjacent bands. We conclude that future generations of large telescopes might be able to probe the composition of the atmospheres of distant extrasolar planets.

David S. Spiegel; Michel Zamojski; Alan Gersch; Jennifer Donovan; Zoltan Haiman

2005-01-07

210

Simulated planetary wavetide interactions in the atmosphere of Mars  

E-print Network

. Recent analysis of aerobraking densities show clear signatures of secondary waves produced at aerobraking altitudes. Citation: Moudden, Y., and J. M. Forbes (2011), Simulated planetary wavetide of longitude structures in Mars aerobraking region density measurements may be attributed, at least in part

Forbes, Jeffrey

211

On the averaging of ratios of specific heats in a multicomponent planetary atmosphere  

NASA Technical Reports Server (NTRS)

The use of adiabatic relations in the calculation of planetary atmospheres requires knowledge of the ratio of specific heats of a mixture of gases under various pressure and temperature conditions. It is shown that errors introduced by simple averaging of the ratio of specific heats in a multicomponent atmosphere can be roughly 0.4%. Therefore, the gamma-averaging error can become important when integrating through the atmosphere to a large depth.

Dubisch, R.

1974-01-01

212

Stability of Satellites around Close-in Extrasolar Giant Planets  

Microsoft Academic Search

We investigate the long-term dynamical stability of hypothetical moons orbiting extrasolar giant planets. Stellar tides brake a planet's rotation and, together with tidal migration, act to remove satellites; this process limits the lifetimes of larger moons in extrasolar planetary systems. Because more massive satellites are removed more quickly than less massive ones, we are able to derive an upper mass

Jason W. Barnes; D. P. O'Brien

2002-01-01

213

The Effect of CO on Planetary Haze Formation  

E-print Network

Organic haze plays a key role in many planetary processes ranging from influencing the radiation budget of an atmosphere to serving as a source of prebiotic molecules on the surface. Numerous experiments have investigated the aerosols produced by exposing mixtures of N$_{2}$/CH$_{4}$ to a variety of energy sources. However, many N$_{2}$/CH$_{4}$ atmospheres in both our solar system and extrasolar planetary systems also contain CO. We have conducted a series of atmosphere simulation experiments to investigate the effect of CO on formation and particle size of planetary haze analogues for a range of CO mixing ratios using two different energy sources, spark discharge and UV. We find that CO strongly affects both number density and particle size of the aerosols produced in our experiments and indicates that CO may play an important, previously unexplored, role in aerosol chemistry in planetary atmospheres.

Hörst, Sarah M

2014-01-01

214

The origins and early histories of planetary atmospheres  

Microsoft Academic Search

Ancient dry river beds detected on Mars by the Viking spacecraft suggest that the early Martian atmosphere may have been much more massive than at present. Degassing of a late-accreting, volatile-rich veneer may account for the primitive atmosphere of both Mars and earth. The primitive earth atmosphere could have produced a greenhouse effect sufficient to maintain temperatures above 273 K

T. Owen

1979-01-01

215

Is Hydrodynamic Escape from Small Orbit Extrasolar Planets Fast or Slow? New Solution of Hydrodynamic Equations and Its Applications  

Microsoft Academic Search

Hydrodynamic escape has important applications in the formation and evolution of planetary atmospheres. Solutions to the time-independent hydrodynamic equations are difficult to find due to the existence of a singularity point. New method to solve time-dependent hydrodynamic equations is developed and validated. When applied to extrasolar planets under intense radiation from parent stars (HD209458b), we tried to answer the following

O. B. Toon; H. de Sterck; F. Tian; A. A. Pavlov

2003-01-01

216

Theory of Tumbling Bodies Entering Planetary Atmospheres with Application to Probe Vehicles and the Australian Tektites  

NASA Technical Reports Server (NTRS)

The tumbling motion of aerodynamically stable bodies entering planetary atmospheres is analyzed considering that the tumbling, its arrest, and the subsequent oscillatory motion are governed by the equation for the fifth Painleve' transcendent. Results based on the asymptotic behavior of the transcendent are applied to study (1) the oscillatory behavior of planetary probe vehicles in relation to aerodynamic heating and loads and (2) the dynamic behavior of the Australian tektites on entering the Earth's atmosphere, under the hypothesis that their origin was the Moon.

Tobak, Murray; Peterson, Victor L.

1964-01-01

217

Multiple scattering polarization – Application of Chandrasekhar’s formalisms to the atmosphere of brown dwarfs and extrasolar planets  

Microsoft Academic Search

Chandrasekhar’s formalisms for the transfer of polarized radiation are used to explain the observed dust scattering polarization\\u000a of brown dwarfs in the optical band. Model polarization profiles for hot and young directly imaged extrasolar planets are\\u000a presented with specific prediction of the degree of polarization in the infrared. The model invokes Chandrasekhar’s formalism\\u000a for the rotation-induced oblateness of the objects

Sujan Sengupta; MARK S MARLEY

2011-01-01

218

Outer satellite atmospheres: Their nature and planetary interactions  

NASA Technical Reports Server (NTRS)

Significant insights regarding the nature and interactions of Io and the planetary magnetosphere were gained through modeling studies of the spatial morphology and brightness of the Io sodium cloud. East-west intensity asymmetries in Region A are consistent with an east-west electric field and the offset of the magnetic and planetary-spin axes. East-west orbital asymmetries and the absolute brightness of Region B suggest a low-velocity (3 km/sec) satellite source of 1 to 2 x 10(26) sodium atoms/sec. The time-varying spatial structure of the sodium directional features in near Region C provides direct evidence for a magnetospheric-wind-driven escape mechanism with a high-velocity (20 km/sec) source of 1 x 10(26) atoms/sec and a flux distribution enhanced at the equator relative to the poles. A model for the Io potassium cloud is presented and analysis of data suggests a low velocity source rate of 5 x 10(24) atoms/sec. To understand the role of Titan and non-Titan sources for H atoms in the Saturn system, the lifetime of hydrogen in the planetary magnetosphere was incorporated into the earlier Titan torus model of Smyth (1981) and its expected impact discussed. A particle trajectory model for cometary hydrogen is presented and applied to the Lyman-alpha distribution of Comet Kohoutek (1973XII).

Smyth, W. H.; Combi, M. R.

1984-01-01

219

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

220

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

221

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

NASA Technical Reports Server (NTRS)

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 atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. Work performed has shown that laboratory measurements of the millimeter-wave opacity of ammonia between 7.5 mm and 9.3 mm and also at the 3.2 mm wavelength require a different lineshape to be used in the theoretical prediction for millimeter-wave ammonia opacity than was previously used. 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.

1989-01-01

222

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

NASA Technical Reports Server (NTRS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth- based or spacecraft-based radio astronomical (emission) 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 the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, new laboratory measurements completed recently by Mohammed and Steffes (2003 and 2004) under this grant (NAG5-12122,5/1/02-4/30/05), have shown that the millimeter-wavelength opacities from both gaseous phosphine (PH3) and gaseous ammonia ("3) under simulated conditions for the outer planets vary significantly from that predicted by theory over a wide range of temperatures and pressures. These results have directly impacted planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment, as discussed below. 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 spacecraft entry probe and orbiter (or flyby) 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.

2005-01-01

223

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

NASA Technical Reports Server (NTRS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based or spacecraft-based radio astronomical (emission) 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 the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements have shown that the centimeter-wavelength opacity from gaseous phosphine (PH3) under simulated conditions for the outer planets far exceeds that predicted from theory over a wide range of temperatures and pressures. This fundamentally changed the resulting interpretation of Voyager radio occultation data at Saturn and Neptune. It also directly impacts planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment and the Rossini RADAR instrument. 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 spacecraft entry probe and orbiter (or flyby) 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.

2002-01-01

224

Detecting Tree-like Multicellular Life on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

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.

Doughty, Christopher E.; Wolf, Adam

2010-11-01

225

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

226

Research in planetary studies and operation of the Mauna Kea Observatory  

NASA Technical Reports Server (NTRS)

The research programs are highlighted in the following areas: major planets; planetary satellites and rings; asteroids; comets; dark organic matter; theoretical and analytical structures; extrasolar planetary; and telescopes.

Cruikshank, Dale P.

1986-01-01

227

Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets  

E-print Network

Opacities and chemical abundance data are crucial ingredients of ultracool dwarf and extrasolar giant planet atmosphere models. We report here on the detailed sources of molecular opacity data employed by our group for this application. We also present tables of Rosseland and Planck mean opacities which are of use in some studies of the atmospheres, interiors, and evolution of planets and brown dwarfs. For the tables presented here we have included the opacities of important atomic and molecular species, including the alkali elements, pressure induced absorption by hydrogen, and other significant opacity sources but neglect opacity from condensates. We report for each species how we have assembled molecular line data from a combination of public databases, laboratory data that is not yet in the public databases, and our own numerical calculations. We combine these opacities with abundances computed from a chemical equilibrium model using recently revised solar abundances to compute mean opacities. The chemical equilibrium calculation accounts for the settling of condensates in a gravitational field, and is applicable to ultracool dwarf and extrasolar planetary atmospheres, but not circumstellar disks. We find that the inclusion of alkali atomic opacity substantially increases the mean opacities over those currently in the literature at densities relevant to the atmospheres and interiors of giant planets and brown dwarfs. We provide our opacity tables for public use and discuss their limitations.

Richard S. Freedman; Mark S. Marley; Katharina Lodders

2007-06-15

228

The ultraviolet absorption spectrum of CO - Applications to planetary atmospheres  

NASA Technical Reports Server (NTRS)

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, Xin-Min; Caldwell, J.; Chen, F. Z.; Judge, D. L.; Wu, C. Y. R.

1993-01-01

229

Possibility of growth of airborne microbes in outer planetary atmospheres  

NASA Technical Reports Server (NTRS)

It is shown that airborne bacteria can maintain metabolic functions in a suitable atmosphere. It is theorized that particles in the Jovian atmosphere would have physical half-lives of 10 to 1500 years, depending upon which of two turbulent models is chosen.

Dimmick, R. L.; Chatigny, M. A.

1975-01-01

230

AIAA JOURNAL VOL. 1, NO. 1 Structure of Planetary Atmospheres  

E-print Network

adiabatic temperature gradient mass absorption coefficient, cm2 /g density of the atmosphere at any given square velocityof escaping particles specific heat of a gas at constantpressure universal would exist at the surface if the atmosphere at all heights were iso- thermal at the temperature ofthe

231

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

232

The Young Sun and Its Influence on Planetary Atmospheres M. Gdel1,2  

E-print Network

-studied "Sun in Time" sample covering ages of 100-7000 Myr in the optical, ultraviolet (UV), far Stellar evolution calculations indicate that the young, zero-age main sequence Sun was bolometricallyThe Young Sun and Its Influence on Planetary Atmospheres M. Güdel1,2 , J.F. Kasting3 1 ETH Zurich

Guedel, Manuel

233

Planetary and Space Science 54 (2006) 11151116 Surfaces and atmospheres of the outer planets,  

E-print Network

with the focus on ground-based and space- craft observations as well as modeling studies related to the neutralPlanetary and Space Science 54 (2006) 1115­1116 Preface Surfaces and atmospheres of the outer returned a wealth of new data revealing a more complex and dynamic system than that revealed by the Voyager

Atreya, Sushil

234

The Boltzmann Equation to Study the Escape of Light Atoms from Planetary Atmospheres  

Microsoft Academic Search

The atmosphere is bound to a planet by the planetary gravitational field. At high altitudes, light atoms such as hydrogen and helium can attain speeds in excess of the escape speed of the planet. These particles escape provided they suffer no further collision. In exospheric models, it is assumed that the escape flux is contributed only by particles moving outwards

Viviane Pierrard

2003-01-01

235

Possibility of growth of airborne microbes in outer planetary atmospheres  

NASA Technical Reports Server (NTRS)

The state of the art of laboratory aerobiological research is briefly reviewed. Experiments are described in which the biological behavior of microbes in or on aerosol particles is investigated in a stirred settling chamber and a rotating drum. Experimental findings are summarized which indicate that airborne bacteria can maintain metabolic functions in a suitable atmosphere. These studies have been undertaken in consideration of the possibility that Jupiter's atmosphere might be contaminated if a space probe enters a biological stratum.

Dimmick, R. L.; Chatigny, M. A.

1976-01-01

236

Extrasolar Planets Lecture 4: Discoveries & Results  

E-print Network

14 Most planets have eccentric orbits rather than circular like our Solar System #12;ASTR178 - other worlds: planets and planetary systems 15 Most planets have eccentric orbits rather than circular like ourExtrasolar Planets Lecture 4: Discoveries & Results Prof. Quentin A Parker ASTR178 - other worlds

Parker, Quentin A.

237

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

NASA Technical Reports Server (NTRS)

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 atmospheric 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 laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often lead to significant misinterpretation of available opacity data. Steffes and Eshleman showed that under environmental conditions corresponding to the middle atmosphere of Venus, the microwave absorption due to atmospheric SO2 was 50 percent greater than that calculated from Van Vleck-Weiskopff theory. Similarly, the opacity from gaseous H2SO4 was found to be a factor of 7 greater than theoretically predicted for conditions of the Venus middle atmosphere. The recognition of the need to make such measurements over a range of temperatures and pressures which correspond to the periapsis altitudes of radio occultation experiments, and over a range of frequencies which correspond to 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.

Steffes, P. G.

1985-01-01

238

Preparing EChO space mission: laboratory simulation of planetary atmospheres  

NASA Astrophysics Data System (ADS)

Space missions, as EChO, or ground based experiments, as SPHERE, have been proposed to measure the atmospheric transmission, reflection and emission spectra. In particular, EChO is foreseen to probe exoplanetary atmospheres over a wavelength range from 0.4 to 16 micron by measuring the combined spectra of the star, its transmission through the planet atmosphere and the emission of the planet. The planet atmosphere characteristics and possible biosignatures will be inferred by studying such composite spectrum in order to identify the emission/absorption lines/bands from atmospheric molecules such as water (H2O), carbon monoxide (CO), methane (CH4), ammonia (NH3) etc. The interpretation of the future EChO observations depends upon the understanding of how the planet atmosphere affects the stellar spectrum and how this last affects the planet emission/absorption. In particular, it is important to know in detail the optical characteristics of gases in the typical physical conditions of the planetary atmospheres and how those characteristics could be affected by radiation induced phenomena such as photochemical and biological one. Insights in this direction can be achieved from laboratory studies of simulated planetary atmosphere of different pressure and temperature conditions under the effects of radiation sources, used as proxies of different bands of the stellar emission.

Claudi, Riccardo U.; Erculiani, Marco S.; Micela, Giuseppina; D'Alessandro, Maurizio; Galletta, Giuseppe; Giro, Enrico; Adriani, Alberto; Altieri, Francesca; Bellucci, Giancarlo; Billi, Daniela; Cecchi-Pestellini, Cesare; Ciaravella, Angela; Filacchione, Gianrico; Gilli, Gabriella; Giuranna, Marco; Grassi, Davide; Leto, Giuseppe; Pace, Emanuele; Palumbo, Maria E.; Piccioni, Giuseppe; Scuderi, Salvatore; Strazzulla, Giovanni; Turrini, Diego

2014-08-01

239

Atmospheric tides on Venus. III - The planetary boundary layer  

NASA Astrophysics Data System (ADS)

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Dobrovolskis, A. R.

1983-10-01

240

Conditions for Organic Haze Formation in Planetary Atmospheres - A Case Study in Archean Earth  

NASA Astrophysics Data System (ADS)

Atmospheric haze can serve as a vital component in the prebiotic synthesis of organic compounds. In many planetary atmospheres, haze is a product of complex organic chemistry, initiated by the deposition of ultraviolet photons, forming compounds that can serve as key components in the propagation of prebiotic chemistry. Saturn’s moon, Titan, provides the prime example of the significance of haze in a planetary atmosphere in our present-day Solar System due to its intricate chemical interaction between aromatic hydrocarbons, nitrogen-bearing species, and complex ions. Titan has long been considered as an analogue for the environment possibly experienced by Archean Earth, and recent studies demonstrate that, like Titan, early Earth may have had an organically-furnished haze layer, facilitated by an enhanced ultraviolet solar flux during this period, protecting greenhouse gases and biota early in their development from harmful ultraviolet radiationi1 and allowing the Earth to maintain temperatures necessary for their development during the faint young Sun period. This primordial haze may have had a different composition than present-day Titan due to the CO2 content and possibly large amounts of H2 in prebiotic Earthi2. Furthermore, the amount of CO2 and H2 in the early terrestrial atmosphere would have had large implications in the efficiency of organic haze formation. A photochemical model employing complex neutral and ion chemistry is used to examine the mechanisms and efficiency of haze formation in a variety of conditions, focusing on sensitivity to factors such as atmospheric composition, and atmospheric temperature profile, and vertical mixing. These results can be used to assess the impact of atmospheric haze on the evolution of planetary atmospheres in our Solar System as well as viability of organic haze formation in the atmospheres of exoplanets. 1 Trainer et al., GRL, 31, L17S08, 2004. 2 Tian et al., Science 308, 1014-1017, 2005.

Wilson, Eric; Atreya, S.

2012-10-01

241

The Role of Remote Sensing Displays in Earth Climate and Planetary Atmospheric Research  

NASA Technical Reports Server (NTRS)

The communities of scientists who study the Earth's climate and the atmospheres of the other planets barely overlap, but the types of questions they pose and the resulting implications for the use and interpretation of remote sensing data sets have much in common. Both seek to determine the characteristic behavior of three-dimensional fluids that also evolve in time. Climate researchers want to know how and why the general patterns that define our climate today might be different in the next century. Planetary scientists try to understand why circulation patterns and clouds on Mars, Venus, or Jupiter are different from those on Earth. Both disciplines must aggregate large amounts of data covering long time periods and several altitudes to have a representative picture of the rapidly changing atmosphere they are studying. This emphasis separates climate scientists from weather forecasters, who focus at any one time on a limited number of images. Likewise, it separates planetary atmosphere researchers from planetary geologists, who rely primarily on single images (or mosaics of images covering the globe) to study two-dimensional planetary surfaces that are mostly static over the duration of a spacecraft mission yet reveal dynamic processes acting over thousands to millions of years. Remote sensing displays are usually two-dimensional projections that capture an atmosphere at an instant in time. How scientists manipulate and display such data, how they interpret what they see, and how they thereby understand the physical processes that cause what they see, are the challenges I discuss in this chapter. I begin by discussing differences in how novices and experts in the field relate displays of data to the real world. This leads to a discussion of the use and abuse of image enhancement and color in remote sensing displays. I then show some examples of techniques used by scientists in climate and planetary research to both convey information and design research strategies using remote sensing displays.

DelGenio, Anthony D.; Hansen, James E. (Technical Monitor)

2001-01-01

242

Scattering and Absorption by Nonspherical Particles in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

The atmospheres of Mars, the giant planets, and Titan all support populations of nonspherical particles. Analyses of observations of these atmospheres therefore rely on an understanding of the optical properties of nonspherical particles. We can glean information on particle size and composition from the wavelength dependence of the optical depth and from the shape of the forward peak of the scattering phase function. Additional information comes from polarization measurements which have been especially fruitful for Titan's haze. The Mars atmosphere contains mineral dust particles with effective radii near 1.6 micro meters, and water ice particles with radii between about 1 and 4 micro meters. The uppermost tropospheric hazes in Jupiter and Saturn are composed of ice crystals of ammonia, water and possibly traces of ammonium hydrosulfide, Methane ice and hydrogen sulfide ice are present in the atmospheres of Uranus and Neptune. Size estimation for these hazes in the giant planets is difficult, and even the expected spectral signatures are elusive, Titan's haze is both forward scattering and strongly polarized - a combination which points toward a fractal aggregate struc1.ure of 10 - 100 or more organic monomers whose radius is about 0.06 micro meters. Polar stratospheric hazes on Jupiter and Saturn also display this characteristic.

West, Robert A.

2005-01-01

243

Stellar-Planetary Relations: Atmospheric Stability as a Prerequisite for Planetary Habitability  

Microsoft Academic Search

The region around a star where a life-supporting biosphere can evolve is the so-called Habitable Zone (HZ). The current definition\\u000a of the HZ is based only on the mass-luminosity relation of the star and climatological and meteorological considerations of\\u000a Earth-like planets, but neglects atmospheric loss processes due to the interaction with the stellar radiation and particle\\u000a environment. From the knowledge

H. Lammer; Yu. N. Kulikov; T. Penz; M. Leitner; H. K. Biernat; N. V. Erkaev

244

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

245

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

246

High sensitivity trace gas sensor for planetary atmospheres: miniaturized Mars methane monitor  

NASA Astrophysics Data System (ADS)

Highly sensitive trace gas measurements in planetary atmospheres can yield information about a planet's atmosphere and surface. One prominent example is methane in the Martian atmosphere, which could originate biogenically and provides answers to one of the most intriguing questions in planetary science: "Does life currently exist on Mars?" Recently, in situ measurements by the Mars Science Laboratory (MSL) have resulted in an upper limit of 1300 parts per trillion by volume (pptv), whereas previous measurements using terrestrial telescopes and an instrument orbiting Mars reported significantly higher values of 10,000 pptv or more. These results are not necessarily contradictory, due to the possibility of spatial and temporal variability of the trace gas concentration. Thus, more measurements will be required to gain clarity. The concept of a miniaturized Mars methane monitor, a high spectral resolution, midinfrared spectrometer observing the sun through the Mars atmosphere from either the Mars surface, a Mars balloon or plane, or a Mars orbiting satellite is presented. The instrument would measure atmospheric methane and water vapor volume mixing ratios with equal or higher precision than the tunable laser spectrometer on MSL. The spectrometer concept uses the spatial heterodyne spectroscopy technique, which has previously been used for ground- and space-based observations of the Earth's atmosphere.

Englert, Christoph R.; Stevens, Michael H.; Brown, Charles M.; Harlander, John M.; DeMajistre, Robert; Marr, Kenneth D.

2014-01-01

247

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

NASA Technical Reports Server (NTRS)

The recognition of the need to make laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressure which correspond to the altitudes probed by radio occultation experiments, and over a range of frequencies which correspond to 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. Construction was completed of the outer planets simulator and measurements were conducted of the microwave absorption and refraction from nitrogen under simulated Titan conditions. The results of these and previous laboratory measurements were applied to a wide range of microwave opacity measurements, in order to derive constituent densities and distributions in planetary atmospheres such as Venus.

Steffes, P. G.

1986-01-01

248

Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves  

NASA Technical Reports Server (NTRS)

As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

2010-01-01

249

Other satellite atmospheres: Their nature and planetary interactions  

NASA Technical Reports Server (NTRS)

The Io sodium cloud model was successfully generated to include the time and spatial dependent lifetime sink produced by electron impact ionization as the plasma torus oscillates about the satellite plane, while simultaneously including the additional time dependence introduced by the action of solar radiation pressure on the cloud. Very preliminary model results are discussed and continuing progress in analysis of the peculiar directional features of the sodium cloud is also reported. Significant progress was made in developing a model for the Io potassium cloud and differences anticipated between the potassium and sodium cloud are described. An effort to understand the hydrogen atmosphere associated with Saturn's rings was initiated and preliminary results of a very and study are summarized.

Smyth, W. H.

1982-01-01

250

Non-LTE model atmospheres for central stars of planetary nebulae  

Microsoft Academic Search

A grid of hot non-LTE model atmospheres with H and He opacity sources has been calculated. The emergent fluxes, together with integrals required for Zanstra and Energy-Balance methods, are presented. These are needed for the analyses and modelling of planetary nebulae. The grid spans the following ranges: Teff: 40 - 180×103K, log g: 4.0 - 8.0, He\\/H: 10 and 1

R. E. S. Clegg; D. Middlemass

1987-01-01

251

Decadal regime shift linkage between global marine fish landings and atmospheric planetary wave forcing  

NASA Astrophysics Data System (ADS)

This investigation focuses on a global forcing mechanism for decadal regime shifts and their subsequent impacts. The proposed global forcing mechanism is the global atmospheric planetary waves that can lead to changes in the global surface air-sea conditions and subsequently fishery changes. In this study, the five decadal regime shifts (1956-1957, 1964-1965, 1977-1978, 1988-1989, and 1998-1999) in the recent 59 years (1950-2008) have been identified based on student t tests and their association with global marine ecosystem change has been discussed. Changes in the three major oceanic (Pacific, Atlantic and Indian) ecosystems will be explored with the goal of demonstrating the linkage between stratospheric planetary waves and the ocean surface forcing that leads to fisheries impacts. Due to the multidisciplinary audience, the global forcing mechanism is described from a top-down approach to help the multidisciplinary audience follow the analysis. Following previous work, this analysis addresses how changes in the atmospheric planetary waves may influence the vertical wind structure, surface wind stress, and their connection with the global ocean ecosystems based on a coupling of the atmospheric regime shifts with the decadal regime shifts determined from marine life changes. The multiple decadal regime shifts related to changes in marine life are discussed using the United Nations Food and Agriculture Organization's (FAO) global fish capture data (catch/stock). Analyses are performed to demonstrate the interactions between the atmosphere, ocean, and fisheries are a plausible approach to explaining decadal climate change in the global marine ecosystems and its impacts. The results show a consistent mechanism, ocean wind stress, responsible for marine shifts in the three major ocean basins. Changes in the planetary wave pattern affect the ocean wind stress patterns. A change in the ocean surface wind pattern from long wave (relatively smooth and less complex) to shorter wave (more convoluted and more complex) ocean surface wind stress creates changes in the ocean marine fisheries.

Powell, A. M., Jr.; Xu, J.

2014-08-01

252

Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope  

E-print Network

The nearby transiting planet HD 189733b was observed during three transits with the ACS camera of the Hubble Space Telescope in spectroscopic mode. The resulting time series of 675 spectra covers the 550-1050 nm range, with a resolution element of ~8 nm, at extremely high accuracy (signal-to-noise ratio up to 10,000 in 50 nm intervals in each individual spectrum). Using these data, we disentangle the effects of limb darkening, measurement systematics, and spots on the surface of the host star, to calculate the wavelength dependence of the effective transit radius to an accuracy of ~50 km. This constitutes the ``transmission spectrum'' of the planetary atmosphere. It indicates at each wavelength at what height the planetary atmosphere becomes opaque to the grazing stellar light during the transit. In this wavelength range, strong features due to sodium, potassium and water are predicted by atmosphere models for a planet like HD 189733b, but they can be hidden by broad absorption from clouds or hazes higher up in the atmosphere. We observed an almost featureless transmission spectrum between 550 and 1050 nm, with no indication of the expected sodium or potassium atomic absorption features. Comparison of our results with the transit radius observed in the near and mid-infrared (2-8 microns), and the slope of the spectrum, suggest the presence of a haze of sub-micron particles in the upper atmosphere of the planet.

F. Pont; H. Knutson; R. L. Gilliland; C. Moutou; D. Charbonneau

2007-12-09

253

Flight with lift modulation inside a planetary atmosphere. [spacecraft trajectory analysis  

NASA Technical Reports Server (NTRS)

A set of dimensionless variables (modified Chapman's variables) is introduced in a derivation of general equations for lifting flight and bank modulation within a planetary atmosphere. The atmosphere is assumed spherical and at rest, and a generalized lift-drag polar is also introduced. Corresponding equations for flight over a flat planet model are attained via a straightforward transformation. Two planar flight cases: flight at constant absolute speed over a spherical planet, and flight at constant descent rate over a flat planet, are analyzed, and the required lift control law (with negative or positive lift) is exhibited in each case. Glide at very high descent rate and plane flows of trajectories are analyzed.

Vinh, N. X.; Bletsos, N. A.; Busemann, A.; Culp, R. D.

1976-01-01

254

Spectra of van der Waals complexes (dimers) with applications to planetary atmospheres  

NASA Technical Reports Server (NTRS)

Spectral features observed in the atmosphere of Titan by the Voyager IR experiment have been attributed to weakly bound complexes of N2 and H2, dominant and minor constituents, respectively. The abundance of H2-N2 dimers there was computed. Current calculations include quantitative spectral line positions and intensities for N2-Ar and CO2-CO2 relating to Titan and Earth, and to Mars and Venus, respectively. This work suggests applications to spectra of planetary atmospheres obtained in spacecraft missions.

Fox, Kenneth; Kim, Sang J.

1988-01-01

255

Implications of the gas compositional measurements of pioneer venus for the origin of planetary atmospheres.  

PubMed

Comparisons are made between the volatile inventories of the terrestrial planets, including Pioneer Venus data, and the predictions of three classes of theories for the origin of planetary atmospheres. Serious difficulties arise for the primary atmosphere and external source hypotheses. The grain accretion hypothesis can account for the trends in the volatile inventory from Venus to Earth to Mars, if volatiles were incorporated into planet-forming grains at nearly the same temperature for all of these planets, but at systematically lower pressures in the regions of planet formation farther from the center of the solar nebula. PMID:17778901

Pollack, J B; Black, D C

1979-07-01

256

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

257

Electron-Nitrogen Collision Processes Relevant to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Electron-N2 collisions play an important role in the nitrogen-rich upper atmospheres of Titan, Triton, and Earth. Modeling these processes requires accurate laboratory data. Despite the recognized importance of such data, there remained an unsatisfactory degree of consensus among much of the available laboratory collision cross section data. To address this situation, our group has devoted considerable effort over the past decade to improve the status of low energy electron collision data. In doing so, we have measured direct excitation cross sections for at least 17 electronic states of neutral N2 and a variety of key UV emission cross sections. Here we review the result of this effort, highlighting how the picture of electron collision processes has evolved, where consensus has been reached and where discrepancies still exist. New electron energy-loss measurements will be presented for excitation of the valence states, with finely spaced (<1eV) impact energy increments in the threshold-to-peak region where excitation is not in proportion to the Franck-Condon factors. These data are novel in that they include measurements at fixed electron scattering angles, differential in impact energy over a range of scattering angle. Also, new near-threshold integral cross sections are provided and compared to existing data.

Johnson, Paul

2011-06-01

258

Superrotation planetary atmospheres: Mechanical analogy, angular momentum budget and simulation of the spin up process  

NASA Technical Reports Server (NTRS)

Superrotation rates observed in planetary atmospheres are analyzed based on the concept of a thermally driven zonally symmetric circulation. Specifically, how this superrotation is produced and maintained against the tendency for friction to oppose differential motions between the atmosphere and the underlying planet is addressed. The time evolution of a fluid leading from corotation under uniform heating to superrotation under globally nonuniform heating is simulated using a three dimensional zonally symmetric spectral model and Laplace transformation. The increased tendency toward geostrophy combined with the increase of surface pressure toward the poles (due to meridional mass transport), induces the atmosphere to subrotate temporarily at lower altitudes. The resulting viscous shear near the surface thus permits angular momentum to flow from the planet into the atmosphere where it propagates upwards and, combined with the change in moment of inertia, produces large superrotation rates at higher viscosities.

Mayr, H. G.; Harris, I.; Conrath, B. J.

1981-01-01

259

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

260

How do Atmospheres Affect Planetary Temperatures? Activity C Can we Model an Atmosphere's Effect Upon a Planet's Surface Temperature?  

NSDL National Science Digital Library

In this activity, students simulate the interaction of variables, including carbon dioxide, in a radiation balance exercise using a spreadsheet-based radiation balance model. Through a series of experiments, students attempt to mimic the surface temperatures of Earth, Mercury, Venus and Mars, and account for the influence of greenhouse gases in atmospheric temperatures. The activity supports inquiry into the real-world problem of contemporary climate change. Student-collected data is needed from activity A in the same module, "How do atmospheres interact with solar energy?" to complete this activity. Included in the resource are several student data sheets and a teacher's guide. This activity is part of module 4, "How do Atmospheres Affect Planetary Temperatures?" in Earth Climate Course: What Determines a Planet's Climate? The course aims to help students to develop an understanding of our environment as a system of human and natural processes that result in changes that occur over various space and time scales.

261

Kinetics of Suprathermal Atoms and Molecules in the Rarefied Planetary Atmospheres  

SciTech Connect

Ground-based and space observations have revealed that the upper layers of planetary atmospheres contain both a thermal fraction of neutral atoms and molecules with the mean particle kinetic energy corresponding to the local gas temperature and a suprathermal (hot) fraction of neutral particles with the mean kinetic energy much higher than the local atmospheric temperature. Atmospheric photochemistry and solar wind/magnetospheric plasma inflow play an important role in the formation of suprathermal atoms and molecules in the rarefied atmospheric gas. The current physical and mathematical models of suprathermal atom formation are presented. These models are used to investigate the formation and kinetics of suprathermal carbon, nitrogen, and oxygen atoms in the upper atmospheres of Venus, Earth, and Mars where they are formed in significant amounts due to the atmospheric photochemistry. The role and input of such photochemical reactions as photo- and electron impact dissociation of the main atmospheric constituents as well as in the exothermic ion-molecular reactions including the dissociative recombination of the ionospheric ions into the formation of hot O populations in the upper atmospheres of the terrestrial planets are estimated.

Shematovich, Valery I. [Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya str., Moscow 119017 (Russian Federation)

2008-12-31

262

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

263

Modeling XUV/EUV/FUV solar spectral irradiance at very high resolution and the upper atmosphere with applications to extrasolar-planets  

NASA Astrophysics Data System (ADS)

This talk will present the latest news on the modeling of the UV solar spectral irradiance (SSI) at very high resolution and will show how this modeling compares and complements observations that are now being carried at moderate spectral resolution and over more limited spectral ranges. Also, the talk will show how the new knowledge makes possible to advance the modeling of the Earth's upper atmosphere including the ionosphere and thermosphere with a much more realistic solar input than it has been done in the past. The new improved input prompts for improving the modeling of planetary atmospheres solar/stellar radiation driven processes in a way that is both realistic and practical for GCM models that can take advantage of the new high-resolution spectral irradiance input. Finally, will briefly mention the exploratory calculations we are now carrying out on other stars to assess their planets (or exoplanets) atmospheres.

Fontenla, J. M.

2013-12-01

264

Formation, Habitability, and Detection of Extrasolar Moons  

E-print Network

The diversity and quantity of moons in the Solar System suggest a manifold population of natural satellites exist around extrasolar planets. Of peculiar interest from an astrobiological perspective, the number of sizable moons in the stellar habitable zones may outnumber planets in these circumstellar regions. With technological and theoretical methods now allowing for the detection of sub-Earth-sized extrasolar planets, the first detection of an extrasolar moon appears feasible. In this review, we summarize formation channels of massive exomoons that are potentially detectable with current or near-future instruments. We discuss the orbital effects that govern exomoon evolution, we present a framework to characterize an exomoon's stellar plus planetary illumination as well as its tidal heating, and we address the techniques that have been proposed to search for exomoons. Most notably, we show that natural satellites in the range of 0.1 - 0.5 Earth mass (i) are potentially habitable, (ii) can form within the c...

Heller, René; Kipping, David; Limbach, Mary Anne; Turner, Edwin; Greenberg, Richard; Sasaki, Takanori; Bolmont, Émeline; Grasset, Olivier; Lewis, Karen; Barnes, Rory; Zuluaga, Jorge I

2014-01-01

265

Atmospheric modelling for the removal of telluric features from infrared planetary spectra  

NASA Astrophysics Data System (ADS)

The effects of telluric absorption on infrared spectra present a problem for the observer. Strong molecular absorptions from species whose concentrations vary with time can be particularly challenging to remove precisely. Yet removing these effects is key to accurately determining the composition of many astronomical objects - planetary atmospheres in particular. Here, we present a method for removing telluric effects based on a modelling approach. The method relies only on observations usually made by the planetary astronomer, and so is directly comparable with current techniques. We use the modelling approach to process observations made of Jupiter, and Saturn's moon Titan and compare the results with those of the standard telluric division technique, finding the modelling approach to have distinct advantages even in conditions regarded as ideal for telluric division.

Cotton, Daniel V.; Bailey, Jeremy; Kedziora-Chudczer, Lucyna

2014-03-01

266

Stability of Satellites Around Close-in Extrasolar Giant Planets  

Microsoft Academic Search

We investigate the long-term dynamical stability of hypothetical moons\\u000aorbiting extrasolar giant planets. Stellar tides brake a planet's rotation and,\\u000atogether with tidal migration, act to remove satellites; this process limits\\u000athe lifetimes of larger moons in extrasolar planetary systems. Because more\\u000amassive satellites are removed more quickly than less massive ones, we are able\\u000ato derive an upper mass

Jason W. Barnes; D. P. O’Brien

2002-01-01

267

The Effects of Snowlines on C/O in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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 H2O 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 ~ 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.

Öberg, Karin I.; Murray-Clay, Ruth; Bergin, Edwin A.

2011-12-01

268

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

269

A theoretical study of polarization in scattered light from planetary and exoplanetary atmospheres  

NASA Astrophysics Data System (ADS)

Scattering of mostly unpolarized (linearly polarized fraction of orde 10-5) starlight by planetary atmospheres partially polarizes the scattered light (order ~0.1). The degree of polarization in scattered light is extremely sensitive to the geometry of the system, which is usually known and the nature of scattering particles, which is often unknown. There has been growing interest in observing polarized light scattered from exoplanetary atmospheres, particularly due to the recent detections of clouds and hazes on a number of exoplanets. The primary motivation of such observations has been the enhanced contrast between the planet and its star when observed in polarized light. There is also a possibility of constraining the geometry of the system, thus providing information about the inclination of the orbit, when it is uncertain from photometry alone. There have been reports of observing polarized light scattered from an exoplanet, though they are disputed.Several groups have numerically modeled the polarized light from exoplanetary atmospheres, but the model atmospheres are close analogues of either Earth or Jupiter with clouds of water or ammonia. While useful for initial investigations, such atmospheres are unrealistic for many close in exoplanets whose atmospheres are thought to contain hazes and clouds of silicates and metals. We will undertake a modeling study, using the vector radiative transfer model VLIDORT to study the phase space of expected atmospheric composition and the observable polarization signal.

Kopparla, Pushkar; Natraj, Vijay; Yung, Yuk L.

2014-11-01

270

Planetary atmosphere models: A research and instructional web-based resource  

NASA Astrophysics Data System (ADS)

The effects of altitude change on the temperature, pressure, density, and speed of sound were investigated. These effects have been documented in Global Reference Atmospheric Models (GRAMs) to be used in calculating the conditions in various parts of the atmosphere for several planets. Besides GRAMs, there are several websites that provide online calculators for the 1976 US Standard Atmosphere. This thesis presents the creation of an online calculator of the atmospheres of Earth, Mars, Venus, Titan, and Neptune. The websites consist of input forms for altitude and temperature adjustment followed by a results table for the calculated data. The first phase involved creating a spreadsheet reference based on the 1976 US Standard Atmosphere and other planetary GRAMs available. Microsoft Excel was used to input the equations and make a graphical representation of the temperature, pressure, density, and speed of sound change as altitude changed using equations obtained from the GRAMs. These spreadsheets were used later as a reference for the JavaScript code in both the design and comparison of the data output of the calculators. The websites were created using HTML, CSS, and JavaScript coding languages. The calculators could accurately display the temperature, pressure, density, and speed of sound of these planets from surface values to various stages within the atmosphere. These websites provide a resource for students involved in projects and classes that require knowledge of these changes in these atmospheres. This project also created a chance for new project topics to arise for future students involved in aeronautics and astronautics.

Gray, Samuel Augustine

271

Geochemical and planetary dynamical views on the origin of Earth's atmosphere and oceans  

E-print Network

Earth's volatile elements (H, C, and N) are essential to maintaining habitable conditions for metazoans and simpler life forms. However, identifying the sources (comets, meteorites, and trapped nebular gas) that supplied volatiles to Earth is not straightforward because secondary processes like mantle degassing, crustal recycling, and escape to space modified the composition of the atmosphere. Here, we review two complementary approaches to investigate the origin of Earth's atmosphere and oceans. The geochemical approach uses volatile element abundances and isotopic compositions to identify the possible contributors to the atmosphere and to disentangle the processes that shaped it. In that respect, noble gases (He, Ne, Ar, Kr, and Xe), elements that are chemically inert and possess several isotopes produced by radioactivity, play a critical role. The dynamical approach uses our knowledge of planetary dynamics to track volatile delivery to the Earth, starting with dust transport in the disk to planet-building ...

Dauphas, Nicolas

2013-01-01

272

Microlensing for extrasolar planets : improving the photometry  

NASA Astrophysics Data System (ADS)

Gravitational Microlensing, as a technique for detecting Extrasolar Planets, is recognised for its potential in discovering small-mass planets similar to Earth, at a distance of a few Astronomical Units from their host stars. However, analysing the data from microlensing events (which statistically rarely reveal planets) is complex and requires continued and intensive use of various networks of telescopes working together in order to observe the phenomenon. As such the techniques are constantly being developed and refined; this project outlines some steps of the careful analysis required to model an event and ensure the best quality data is used in the fitting. A quantitative investigation into increasing the quality of the original photometric data available from any microlensing event demonstrates that 'lucky imaging' can lead to a marked improvement in the signal to noise ratio of images over standard imaging techniques, which could result in more accurate models and thus the calculation of more accurate planetary parameters. In addition, a simulation illustrating the effects of atmospheric turbulence on exposures was created, and expanded upon to give an approximation of the lucky imaging technique. This further demonstrated the advantages of lucky images which are shown to potentially approach the quality of those expected from diffraction limited photometry. The simulation may be further developed for potential future use as a 'theoretical lucky imager' in our research group, capable of producing and analysing synthetic exposures through customisable conditions.

Bajek, David J.

273

Infrared spectroscopy of homogeneously nucleated hydrazine aerosols - Disordered and crystalline phases. [in planetary atmospheres  

NASA Technical Reports Server (NTRS)

It is shown that aerosols generated at low temperatures and high condensation rate spontaneously form in a highly crystalline state. The resonant absorption bands in the IR spectra of these highly crystalline particles are much sharper than any reported previously in the bulk, and reveal details in the N-H vibrational bands that have not been previously observed. A disordered phase is also observed at somewhat higher temperatures. These results are consistent with this being a supercooled liquid. The fact that the spectra associated with these two aerosol phases are quite different is important to any future attempts at detecting hydrazine aerosols in planetary atmospheres by remote sensing techniques.

Dunder, T.; Clapp, M. L.; Miller, R. E.

1993-01-01

274

Extrasolar planet taxonomy: a new statistical approach  

E-print Network

In this paper we present the guidelines for an extrasolar planet taxonomy. The discovery of an increasing number of extrasolar planets showing a vast variety of planetary parameters, like Keplerian orbital elements and environmental parameters, like stellar masses, spectral types, metallicity etc., prompts the development of a planetary taxonomy. In this work via principal component analysis followed by hierarchical clustering analysis, we report the definition of five robust groups of planets. We also discuss the physical relevance of such analysis, which may provide a valid basis for disentangling the role of the several physical parameters involved in the processes of planet formation and subsequent evolution. For instance, we were able to divide the hot Jupiters into two main groups on the basis of their stellar masses and metallicities. Moreover, for some groups, we find strong correlations between metallicity, semi-major axis and eccentricity. The implications of these findings are discussed.

Simone Marchi

2007-05-07

275

Detection of Extrasolar Planets by Transit Photometry  

NASA Technical Reports Server (NTRS)

A knowledge of other planetary systems that includes information on the number, size, mass, and spacing of the planets around a variety of star types is needed to deepen our understanding of planetary system formation and processes that give rise to their final configurations. Recent discoveries show that many planetary systems are quite different from the solar system in that they often possess giant planets in short period orbits. The inferred evolution of these planets and their orbital characteristics imply the absence of Earth-like planets near the habitable zone. Information on the properties of the giant-inner planets is now being obtained by both the Doppler velocity and the transit photometry techniques. The combination of the two techniques provides the mass, size, and density of the planets. For the planet orbiting star HD209458, transit photometry provided the first independent confirmation and measurement of the diameter of an extrasolar planet. The observations indicate a planet 1.27 the diameter of Jupiter with 0.63 of its mass (Charbonneau et al. 1999). The results are in excellent agreement with the theory of planetary atmospheres for a planet of the indicated mass and distance from a solar-like star. The observation of the November 23, 1999 transit of that planet made by the Ames Vulcan photometer at Lick Observatory is presented. In the future, the combination of the two techniques will greatly increase the number of discoveries and the richness of the science yield. Small rocky planets at orbital distances from 0.9 to 1.2 AU are more likely to harbor life than the gas giant planets that are now being discovered. However, new technology is needed to find smaller, Earth-like planets, which are about three hundred times less massive than Jupiter-like planets. The Kepler project is a space craft mission designed to discover hundreds of Earth-size planets in and near the habitable zone around a wide variety of stars. To demonstrate that the technology exists to find such small planets, our group has conducted an end-to-end system test. The results of the laboratory tests are presented and show that we are ready to start the search for Earth-size planets.

Borucki, William; Koch, David; Webster, Larry; Dunham, Edward; Witteborn, Fred; Jenkins, Jon; Caldwell, Douglas; Showen, Robert; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

276

Polarization radiation in the planetary atmosphere delimited by a heterogeneous diffusely reflecting surface  

NASA Technical Reports Server (NTRS)

Spatial frequency characteristics (SFC) and the scattering functions were studied in the two cases of a uniform horizontal layer with absolutely black bottom, and an isolated layer. The mathematical model for these examples describes the horizontal heterogeneities in a light field with regard to radiation polarization in a three dimensional planar atmosphere, delimited by a heterogeneous surface with diffuse reflection. The perturbation method was used to obtain vector transfer equations which correspond to the linear and nonlinear systems of polarization radiation transfer. The boundary value tasks for the vector transfer equation that is a parametric set and one dimensional are satisfied by the SFC of the nonlinear system, and are expressed through the SFC of linear approximation. As a consequence of the developed theory, formulas were obtained for analytical calculation of albedo in solving the task of dissemination of polarization radiation in the planetary atmosphere with uniform Lambert bottom.

Strelkov, S. A.; Sushkevich, T. A.

1983-01-01

277

Light scattering by randomly oriented cubes and parallelepipeds. [for interpretation of observed data from planetary atmospheres  

NASA Technical Reports Server (NTRS)

In this paper, the geometric ray tracing theory for the scattering of light by hexagonal cylinders to cubes and parallelepipeds has been modified. Effects of the real and imaginary parts of the refractive index and aspect ratio of the particle on the scattering phase function and the degree of linear polarization are investigated. Causes of the physical features in the scattering polarization patterns are identified in terms of the scattering contribution due to geometric reflections and refractions. The single-scattering phase function and polarization data presented in this paper should be of some use for the interpretation of observed scattering and polarization data from planetary atmospheres and for the physical understanding of the transfer of radiation in an atmosphere containing nonspherical particles.

Liou, K. N.; Cai, Q.; Pollack, J. B.; Cuzzi, J. N.

1983-01-01

278

Structure of the atmosphere in an urban planetary boundary layer from lidar and radiosonde observations  

SciTech Connect

The planetary boundary layer (PBL) over Mexico City was probed with a scanning backscatter lidar to characterize and evaluate the multidimensional structure of the atmosphere. Comparisons were made between radiosonde and lidar-derived PBL heights which showed the two techniques to be in close agreement. The spatial properties of the free atmosphere-PBL interface were found to be approximately the same size as the entrainment zone thickness. Below the interface the lidar observed spatially resolved structures, such as thermal plumes, convective eddies low-level jets, and entrainment into the PBL. These structures were spatially correlated with the local diabatic condition and wind stress. One highly unstable atmosphere contains a lidar-visualized convective structure rising to a height of 0.45 the inversion base, which was predicted from earlier turbulence models. Other features, such as low-level jets, were found to be associated with neutral atmospheres in the mixing layer. The analysis indicates that the transport of pollutants is not a continuous and gradient-driven process, but low frequency and spatially discontinuous. The high spatial and temporal resolution afforded by the scanning lidar depicts surface-atmosphere interactions which are neither spatially homogeneous nor horizontally uniform. 20 refs., 12 figs., 1 tab.

Cooper, D.I.; Eichinger, W.E. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1994-11-20

279

Large scale modulations of spectral aerosol optical depths by atmospheric planetary waves  

NASA Astrophysics Data System (ADS)

Analysis of 6 years of spectral aerosol optical depths (AOD), obtained during boreal winter at the tropical semi-arid location Anantapur, India, revealed significant modulations (to the seasonal mean AOD) by planetary scale atmospheric waves. Most significant contributions came from 30 to 50 day, and quasi-16 day periodicities; each contributing ~10% to 24%, and jointly up to 45% to the seasonal mean AOD; the contribution varying linearly with zonal wind speed. Analysis of the upper air wind fields revealed these to be associated with Madden Julian Oscillations and quasi -16 day planetary waves. The spectral dependence of AOD also responded to these waves, becoming flatter with the strengthening of the MJO and steeper with the quasi-16 oscillations. The possible implications of these to the long-range transport of different aerosol types to the measurement region are discussed. The findings signify the role of natural atmospheric motions in producing significant changes in spectral AOD, which will have strong implications to regional climate.

Beegum, S. Naseema; Krishna Moorthy, K.; Babu, S. Suresh; Reddy, R. Ramakrishna; Gopal, K. Rama

2009-02-01

280

Infrared spectra of van de Waals complexes of importance in planetary atmospheres  

NASA Technical Reports Server (NTRS)

It has been suggested that (CO2)2 and Ar-CO2 are important constituents of the planetary atmospheres of Venus and Mars. Recent results on the laboratory spectroscopy of CO2 containing van der Waals complexes which may be of use in the modeling of the spectra of planetary atmospheres are presented. Sub-Doppler infrared spectra were obtained for (CO2)2, (CO2)3, and rare-gas-CO2 complexes in the vicinity of the CO2 Fermi diad at 2.7 micrometers using a color-center-laser optothermal spectrometer. From the spectroscopic constants the geometries of the complexes have been determined and van der Waals vibrational frequencies have been estimated. The equilibrium configurations are C2h, C3h, and C2v, for (CO2)2, (CO2)3, and the rare-gas-CO2 complexes, respectively. Most of the homogeneous linewidths for the revibrational transitions range from 0.5 to 22 MHz, indicating that predissociation is as much as four orders of magnitude faster than radiative processes for vibrational relaxation in these complexes.

Fraser, G. T.; Pine, A. S.; Lafferty, W. J.

1990-01-01

281

The CORALIE survey for southern extrasolar planets XIV. HD 142022 b: a long-period planetary companion in a wide binary  

E-print Network

We report precise Doppler measurements of HD 142022 obtained during the past six years with the CORALIE echelle spectrograph at La Silla Observatory together with a few additional observations made recently with the HARPS echelle spectrograph. Our radial velocities reveal evidence of a planetary companion with an orbital period P = 1928 +53-39 days, an eccentricity e = 0.53 +0.23-0.18, and a velocity semiamplitude K = 92 +102-29 m/s. The inferred companion minimum mass is M2sini = 5.1 +2.6-1.5 MJup and the semimajor axis a = 3.03+/-0.05 AU. Only one full orbital revolution has been monitored yet, and the periastron passage could not be observed since the star was too low on the horizon. The eccentricity and velocity semiamplitude remain therefore quite uncertain and the orbital solution is preliminary. HD 142022 is a chromospherically inactive K0 dwarf, metal rich relative to the Sun, and is the primary component of a wide binary. HD 142022 b is thus a new "planet in binary" candidate, and its high eccentricity might be due to secular interactions with the distant stellar companion.

A. Eggenberger; M. Mayor; D. Naef; F. Pepe; D. Queloz; N. C. Santos; S. Udry; C. Lovis

2005-10-19

282

Direct modeling of transiting planet light curves from model stellar atmospheres  

NASA Astrophysics Data System (ADS)

Recent and new observations of extrasolar planets via the transit method are provided unparalleled measurements that enhance our understanding of both the planets and their host stars. However, analysis techniques assume simple parameters to describe the stellar intensity profile. In this work, we compare new planetary transit light curves computed directly from model stellar atmosphere intensity profiles with light curves computed using limb-darkening coefficients. This comparison highlights the need for better models of stellar intensities and atmospheres to better understand the extrasolar planets themselves, especially in the upcoming eras of TESS and PLATO.

Mcneil, Joseph; Neilson, H.; Ignace, R.

2014-01-01

283

Strong scintillations during atmospheric occultations Theoretical intensity spectra. [radio scattering during spacecraft occultations by planetary atmospheres  

NASA Technical Reports Server (NTRS)

Each of the two Voyager spacecraft launched in 1977 has completed a reconnaissance of the Jovian and Saturnian systems. In connection with occultation experiments, strong scintillations were observed. Further theoretical work is required before these scintillations can be interpreted. The present study is, therefore, concerned with the derivation of a theory for strong scattering during atmospheric occultation experiments, taking into account as fundamental quantity of interest the spatial spectrum (or spectral density) of intensity fluctuations. Attention is given to a theory for intensity spectra, and numerical calculations. The new formula derived for Phi-i accounts for strong scattering of electromagnetic waves during atmospheric occultations.

Hinson, D. P.

1986-01-01

284

Planetary host stars: Evaluating uncertainties in ultra-cool model atmospheres  

E-print Network

M-dwarfs are discussed as promising targets for detecting planet at the lower mass end of the planetary mass distribution. An important step in this process is to accurately estimate the stellar parameters of the M-dwarf host star for which the results of stellar model atmosphere simulations are used. We present a comparison of the ATLAS9, MARCS, PHOENIX and Drift-PHOENIX model atmosphere families in the M-dwarf parameter space. We examine the differences in the (T$_{\\rm gas}$, p$_{\\rm gas}$)-structures, in synthetic photometric fluxes and in colour indices. We compiled the broad-band synthetic photometric fluxes for all available M-dwarf model atmospheres for the UKIRT WFCAM ZYJHK, 2MASS JHKs and Johnson UBVRI filters, and calculated related colour indices. We find that the synthetic colours in the IR wavelengths diverge by no more than 0.15 dex amongst all model families. For all bands considered, discrepancies in colour diminish for the higher T$_{\\rm eff}$-end of model atmosphere grids. We notice signific...

Bozhinova, I; Scholz, A

2014-01-01

285

Transit of Extrasolar Planets  

NASA Technical Reports Server (NTRS)

During the past five years we have pursued the detection of extrasolar planets by the photometric transit method, i.e. the detection of a planet by watching for a drop in the brightness of the light as it crosses in front of a star. The planetary orbit must cross the line-of-sight and so most systems will not be lined up for such a transit to ever occur. However, we have looked at eclipsing binary systems which are already edge-on. Such systems must be very small in size as this makes the differential light change due to a transit much greater for a given planet size (the brightness difference will be proportional to the area of the transiting planet to the disc area of the star). Also, the planet forming region should be closer to the star as small stars are generally less luminous (that is, if the same thermal regime for planet formation applies as in the solar system). This led to studies of the habitable zone around other stars, as well. Finally, we discovered that our data could be used to detect giant planets without transits as we had been carefully timing the eclipses of the stars (using a GPS antenna for time) and this will drift by being offset by any giant planets orbiting around the system, as well. The best summary of our work may be to just summarize the 21 refereed papers produced during the time of this grant. This will be done is chronological order and in each section separately.

Doyle, Laurance R.

1998-01-01

286

Dynamical evolution of planetary systems Alessandro Morbidelli  

E-print Network

. The discovery of extra-solar planets showed astonishingly that the orbital structure of our planetary system is not typical. Many giant extra-solar planets have orbits with semi major axes of 1 AU, and some have even of the giant planets have been achieved during a phase of orbital instability, during which the planets

Paris-Sud XI, Université de

287

Imaging Extrasolar Planets from the Ground  

Microsoft Academic Search

An approach to direct imaging of extrasolar planets is described, in which adaptive optics to correct atmospheric aberration are based on interferometric measurements made in the focal plane. In order to minimize the weak, residual speckles of the stellar halo, their complex amplitudes are first determined using photon-counting, spectrally-resolved imaging sensors. Corrections to both the corrugation and intensity of the

R. Angel

2003-01-01

288

Characterization of Extrasolar Planets Using SOFIA  

NASA Technical Reports Server (NTRS)

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

Deming, Drake

2010-01-01

289

Confirming the most water-rich extrasolar rocky body  

NASA Astrophysics Data System (ADS)

Most theories of exobiology require liquid water for a planet to be considered as habitable. Yet, very little is known about the prevalence of water for mature rocky objects in extrasolar planetary systems. A unique method of probing the existence, characteristics, and frequency of extrasolar water-bearing rocky bodies is through examining their bulk composition after they have been accreted by their host white dwarf star. Results to date show that water-rich extrasolar rocky bodies are rare. Evidence for oxygen in ground-based spectroscopy of SDSSJ104341.53+085558.2 suggests that it could be accreting the most water-rich extrasolar rocky object currently known. We propose COS ultraviolet spectroscopy to confirm the water-rich nature and characterize the mineralogy of the rocky body being accreted by this white dwarf star.

Melis, Carl

2014-10-01

290

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

291

Interstellar planetary protection  

Microsoft Academic Search

In the coming decades the detection of Earth-like extrasolar planets, either apparently lifeless or exhibiting spectral signatures of life, will encourage design studies for craft to visit them. These missions will require the elaboration of an interstellar planetary protection protocol. Given a specific dose required to sterilize microorganisms on a spacecraft, a critical mean velocity can be determined below which

Charles S. Cockell

2008-01-01

292

Middle atmosphere dynamics with gravity wave interactions in the numerical spectral model: Tides and planetary waves  

NASA Astrophysics Data System (ADS)

As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) 10-h global-scale inertio gravity waves. Numerical experiments are discussed, which illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations.

Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

2011-05-01

293

Microwave spectra of van der Waals complexes of importance in planetary atmospheres  

NASA Technical Reports Server (NTRS)

The Fourier-transform Fabry-Perot pulsed-molecular-beam microwave spectrometer at NIST was used to study the microwave spectra of a number of molecular dimers and trimers that may be present in planetary atmospheres. The weak van der Waals bonds associated with these species usually give rise to rotational-tunneling splittings in the microwave spectra. The microwave spectrum of the water dimer species was used to illustrate the complications that can arise in the study of the rotational spectra of these loosely bound species. In addition to the water dimer species, the microwave spectra of the following hydrogen-bonded and van der Waals complexes were studied: (CO2)2-H2O, CO2-(H2O)2, CO2-H2S, N2-H2O, CO-H2O, SO2-H2O, and O3-H2O.

Suenram, R. D.; Lovas, F. J.

1990-01-01

294

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

295

Proposal for constructing an advanced software tool for planetary atmospheric modeling  

NASA Technical Reports Server (NTRS)

Scientific model building can be a time intensive and painstaking process, often involving the development of large and complex computer programs. Despite the effort involved, scientific models cannot easily be distributed and shared with other scientists. In general, implemented scientific models are complex, idiosyncratic, and difficult for anyone but the original scientist/programmer to understand. We believe that advanced software techniques can facilitate both the model building and model sharing process. We propose to construct a scientific modeling software tool that serves as an aid to the scientist in developing and using models. The proposed tool will include an interactive intelligent graphical interface and a high level, domain specific, modeling language. As a testbed for this research, we propose development of a software prototype in the domain of planetary atmospheric modeling.

Keller, Richard M.; Sims, Michael H.; Podolak, Esther; Mckay, Christopher P.; Thompson, David E.

1990-01-01

296

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

NASA Technical Reports Server (NTRS)

After long arduous work with the simulator, measurements of the refractivity and absorptivity of nitrogen under conditions similar to those for Titan were completed. The most significant measurements, however, were those of the microwave absorption from gaseous ammonia under simulated conditions for the Jovian atmospheres over wavelengths from 1.3 to 22 cm. The results of these measurements are critical in that they confirm the theoretical calculation of the ammonia opacity using the Ben-Reuven lineshape. The application of both these results, and results obtained previously, to planetary observations at microwave frequencies were especially rewarding. Applications of the results for ammonia to radio astronomical observations of Jupiter in the 1.3 to 20 cm wavelength range and the application of results for gaseous H2SO4 under simulated Venus conditions are discussed.

Steffes, P. G.

1986-01-01

297

The solar wind interaction with Mars: Recent progress and future directions The Sun has a powerful influence on planetary atmospheres.  

E-print Network

Editorial The solar wind interaction with Mars: Recent progress and future directions The Sun has a powerful influence on planetary atmospheres. This is especially true for planets lacking a global magnetic field, because the solar wind can interact directly with the upper atmo- sphere. Neutral particles

California at Berkeley, University of

298

Theory of extended stellar atmospheres. II - A grid of static spherical models for O stars and planetary nebula nuclei  

Microsoft Academic Search

Spherical static non-LTE model atmospheres are presented for stars from 30 to 60 solar masses at various points on their evolutionary tracks, and for some nuclei of planetary nebulae at two points of a modified Harman-Seaton sequence. The method of Mihalas and Hummer was employed, which uses a parametrized radiation force multiplier to simulate the force of radiation arising from

P. B. Kunasz; D. G. Hummer; D. Mihalas

1975-01-01

299

Comparative Study on Hot Atom Coronae of Solar and Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Solar/stellar forcing on the upper atmospheres of the solar and extrasolar planets via both absorption of the XUV (soft X-rays and extreme ultraviolet) radiation and atmospheric sputtering results in the formation of an extended neutral corona populated by the suprathermal (hot) H, C, N, and O atoms (see, e.g., Johnson et al., 2008). The hot corona, in turn, is altered by an inflow of the solar wind/magnetospheric plasma and local pick-up ions onto the planetary exosphere. Such inflow results in the formation of the superthermal atoms (energetic neutral atoms - ENAs) due to the charge exchange with the high-energy precipitating ions and can affect the long-term evolution of the atmosphere due to the atmospheric escape. The origin, kinetics and transport of the suprathermal H, C, N, and O atoms in the transition regions (from thermosphere to exosphere) of the planetary atmospheres are discussed. Reactions of dissociative recombination of the ionospheric ions CO _{2} (+) , CO (+) , O _{2} (+) , and N _{2} (+) with thermal electrons are the main photochemical sources of hot atoms. The dissociation of atmospheric molecules by the solar/stellar XUV radiation and accompanying photoelectron fluxes and the induced exothermic photochemistry are also the important sources of the suprathermal atoms. Such kinetic systems with the non-thermal processes are usually investigated with the different (test particles, DSMC, and hybrid) versions of the kinetic Monte Carlo method. In our studies the kinetic energy distribution functions of suprathermal and superthermal atoms were calculated using the stochastic model of the hot planetary corona (Shematovich, 2004, 2010; Groeller et al., 2014), and the Monte Carlo model (Shematovich et al., 2011, 2013) of the high-energy proton and hydrogen atom precipitation into the atmosphere respectively. These functions allowed us to estimate the space distribution of suprathermals in the planetary transition regions. An application of these numerical models to study the atmospheric gas flow in the transition region from the collision-dominated thermosphere to collisionless exosphere, and the non-thermal escape will be discussed and illustrated with the simple 1D-models of the hot coronae of the solar and extrasolar planets. This work is supported by the RFBR project No. 14-02-00838a and by the Basic Research Program of the Presidium of the Russian Academy of Sciences (Program 22). begin{itemize} Johnson et al., Sp. Sci.Rev., 2008, v. 139, 355. Shematovich, Solar System Res., 2004, v.38, 28. Shematovich, Solar System Res., 2010, v.44, 96. Shematovich et al., J. Geophys. Res., 2011, v.116, A11320; 2013, v. 118, 1231. Groeller et al., Planet. Space Sci., 2014.

Shematovich, Valery

300

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

301

A Possible Aeronomy of Extrasolar Terrestrial Planets  

E-print Network

Terrestrial planetary systems may exist around nearby stars as the Earth-sized counterparts to the many giant planets already discovered within the solar neighborhood. In this chapter we first discuss the numerous techniques which have been suggested to search for extrasolar terrestrial planets. We then focus on the expected results from that technique in which an orbiting telescope or interferometer is used to obtain a visible or infrared spectrum of a planet, without contamination from the parent star. We show examples of such spectra for selected cases: the present Earth, the Neoproterozoic (snowball) Earth, a methane-rich Earth, and the present Mars and Venus. We conclude by discussing the implications of such spectra for the detection of life on an extrasolar terrestrial planet.

W. A. Traub; K. W. Jucks

2002-05-22

302

A Possible Aeronomy of Extrasolar Terrestrial Planets  

E-print Network

Terrestrial planetary systems may exist around nearby stars as the Earth-sized counterparts to the many giant planets already discovered within the solar neighborhood. In this chapter we first discuss the numerous techniques which have been suggested to search for extrasolar terrestrial planets. We then focus on the expected results from that technique in which an orbiting telescope or interferometer is used to obtain a visible or infrared spectrum of a planet, without contamination from the parent star. We show examples of such spectra for selected cases: the present Earth, the Neoproterozoic (snowball) Earth, a methane-rich Earth, and the present Mars and Venus. We conclude by discussing the implications of such spectra for the detection of life on an extrasolar terrestrial planet.

Traub, W A

2002-01-01

303

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

304

Modeling and Observing Extrasolar Planetary Transits  

Microsoft Academic Search

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

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

2010-01-01

305

VISTA: a micro-thermogravimeter to analyze condensable species in planetary atmospheres  

NASA Astrophysics Data System (ADS)

Thermogravimetry is a technique largely used in order to study absorption/desorption and sublimation/evaporation processes in several environments. Micro-thermogravimetry (mu-TGA) is particularly suitable for space applications, due to the very small mass, volume and power required by mu-TGA sensors. VISTA (Volatile In Situ Thermogravimetry Analyser) is a micro-thermogravimeter developed at IAPS-INAF (Rome) which aims to measure the amount of volatiles of scientific interest (e.g. water, organics) in planetary environments. It is based on Piezoelectric Crystal Microbalances (PCM), whose resonant frequency is linearly related to the deposited mass. The PCM heating/cooling allows the release/deposition of volatile materials, allowing to measure their abundance and to infer their composition. The instrument has been selected in the payload of the ESA MarcoPolo-R proposed mission, aiming to analyze in situ and bring to Earth samples of asteroidal regolith. In this framework, VISTA would measure the water and organic content in the asteroid regolith, detect the possible cometary-like activity of the asteroid and assess the contamination issue. VISTA could be used also to assess relevant scientific issue concerning planetary atmospheres. It has been studied for the ESA Cosmic Vision proposed missions EVE (European Venus Explorer) and TAE (Titan Aerial Explorer), which planned an in-situ analysis of the Venus and Titan atmosphere, respectively. In the framework of a Venus in-situ mission, VISTA would have the following goals: - Measurement of dew points of condensable species, and hence of humidity (by cooling the PCM down to condensation temperatures) - Measurement of amount of refractory species in the Venus cloud aerosols (by heating the PCM) - Measurement of electric charge of cloud particles (by coupling the thermogravimeter and an electric field generator) In the framework of a Titan in-situ mission, the heating of the VISTA PCM would: - determine the presence of nucleating aerosols in cloud droplets, hence whether methane cloud droplets homogeneously or heterogeneously nucleate - measure the abundance of organic compounds of particular scientific interest present as nucleating seeds within cloud particles (acetylene, benzene, HCN)

Palomba, Ernesto; Zampetti, Emiliano; Longobardo, Andrea; Biondi, David; Saggin, Bortolino; Boccaccini, Angelo; Dirri, Fabrizio

306

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

307

Satellite radio occultation investigations of internal gravity waves in the planetary atmospheres  

NASA Astrophysics Data System (ADS)

Internal gravity waves (IGWs) modulate the structure and circulation of the Earth’s atmosphere, producing quasi-periodic variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. In this context, an original method for the determination of IGW parameters from a vertical temperature profile measurement in a planetary atmosphere has been developed [Gubenko et al., 2008, 2011, 2012]. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, the analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitudes of the wave field and on the linear IGW saturation theory in which these amplitudes are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability threshold, energy is assumed to be dissipated in such a way that the IGW amplitude is maintained at the instability threshold level as the wave propagates upwards. We have extended the developed technique [Gubenko et al., 2008] in order to reconstruct the complete set of wave characteristics including such important parameters as the wave kinetic and potential energy per unit mass and IGW fluxes of the energy and horizontal momentum [Gubenko et al., 2011]. We propose also an alternative method to estimate the relative amplitudes and to extract IGW parameters from an analysis of perturbations of the Brunt-Vaislala frequency squared [Gubenko et al., 2011]. An application of the developed method to the radio occultation (RO) temperature data has given the possibility to identify the IGWs in the Earth's, Martian and Venusian atmospheres and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal wind velocity perturbations, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy per unit mass, vertical fluxes of the wave energy and horizontal momentum. Vertical profiles of temperature retrieved from RO measurements of the CHAMP (Earth), Mars Global Surveyor (Mars), Magellan and Venus Express (Venus) missions are used and analyzed to identify discrete or “narrow spectral” wave events and to determine IGW characteristics in the Earth’s, Martian and Venusian atmospheres. This work was partially supported by the RFBR grant 13-02-00526-? and Program 22 of the RAS Presidium. References. Gubenko V.N., Pavelyev A.G., Andreev V.E. Determination of the intrinsic frequency and other wave parameters from a single vertical temperature or density profile measurement // J. Geophys. Res. 2008. V. 113. No.D08109, doi:10.1029/2007JD008920. Gubenko V.N., Pavelyev A.G., Salimzyanov R.R., Pavelyev A.A. Reconstruction of internal gravity wave parameters from radio occultation retrievals of vertical temperature profiles in the Earth’s atmosphere // Atmos. Meas. Tech. 2011. V. 4. No.10. P. 2153-2162, doi:10.5194/amt-4-2153-2011. Gubenko V.N., Pavelyev A.G., Salimzyanov R.R., Andreev V.E. A method for determination of internal gravity wave parameters from a vertical temperature or density profile measurement in the Earth’s atmosphere // Cosmic Res. 2012. V. 50. No.1. P. 21-31, doi: 10.1134/S0010952512010029.

Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander

308

Direct Imaging of Warm Extrasolar Planets  

SciTech Connect

One of the most exciting scientific discoveries in the last decade of the twentieth century was the first detection of planets orbiting a star other than our own. By now more than 130 extrasolar planets have been discovered indirectly, by observing the gravitational effects of the planet on the radial velocity of its parent star. This technique has fundamental limitations: it is most sensitive to planets close to their star, and it determines only a planet's orbital period and a lower limit on the planet's mass. As a result, all the planetary systems found so far are very different from our own--they have giant Jupiter-sized planets orbiting close to their star, where the terrestrial planets are found in our solar system. Such systems have overturned the conventional paradigm of planet formation, but have no room in them for habitable Earth-like planets. A powerful complement to radial velocity detections of extrasolar planets will be direct imaging--seeing photons from the planet itself. Such a detection would allow photometric measurements to determine the temperature and radius of a planet. Also, direct detection is most sensitive to planets in wide orbits, and hence more capable of seeing solar systems resembling our own, since a giant planet in a wide orbit does not preclude the presence of an Earth-like planet closer to the star. Direct detection, however, is extremely challenging. Jupiter is roughly a billion times fainter than our sun. Two techniques allowed us to overcome this formidable contrast and attempt to see giant planets directly. The first is adaptive optics (AO) which allows giant earth-based telescopes, such as the 10 meter W.M. Keck telescope, to partially overcome the blurring effects of atmospheric turbulence. The second is looking for young planets: by searching in the infrared for companions to young stars, we can see thermal emission from planets that are still warm with the heat of their formation. Together with a UCLA team that leads the field of young-star identification, we carried out a systematic near-infrared search for young planetary companions to {approx}200 young stars. We also carried out targeted high-sensitivity observations of selected stars surrounded by circumstellar dust rings. We developed advanced image processing techniques to allow detection of even fainter sources buried in the noisy halo of scattered starlight. Even with these techniques, around most of our targets our search was only sensitive to planets in orbits significantly wider than our solar system. With some carefully selected targets--very young dusty stars in the solar neighborhood--we reach sensitivities sufficient to see solar systems like our own. Although we discovered no unambiguous planets, we can significantly constrain the frequency of such planets in wide (>50 AU) orbits, which helps determine which models of planet formation remain plausible. Successful modeling of our observations has led us to the design of a next-generation AO system that will truly be capable of exploring solar systems resembling our own.

Macintosh, B

2005-04-11

309

Arctic Sea Ice Export Through Fram Strait and Atmospheric Planetary Waves  

NASA Technical Reports Server (NTRS)

A link is found between the variability of Arctic sea ice export through Ram Strait and the phase of the longest atmospheric planetary wave (zonal wave 1) in SLP for the period 1958-1997. Previous studies have identified a link between From Strait ice export and the North Atlantic Oscillation (NAO), but this link has been described as unstable because of a lack of consistency over time scales longer than the last two decades. Inconsistent and low correlations are also found between From Strait ice export and the Arctic Oscillation (AD) index. This paper shows that the phase of zonal wave 1 explains 60% - 70% of the simulated From Strait ice export variance over the Goodyear period 1958 - 1997. Unlike the NAB and AD links, these high variances are consistent for both the first and second halves of the Goodyear period. This consistency is attributed to the sensitivity of the wave I phase at high latitudes to the presence of secondary low pressure systems in the Barents Sea that serve to drive sea ice southward through From Strait. These results provide further evidence that the phase of zonal wave 1 in SLP at high latitudes drives regional as well as hemispheric low frequency Arctic Ocean and sea ice variability.

Cavalieri, Donald J.; Koblinsky, Chester (Technical Monitor)

2001-01-01

310

The Runaway Greenhouse: implications for future climate change, geoengineering and planetary atmospheres  

E-print Network

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 once the surface reaches ~1400K 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 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 diox...

Goldblatt, Colin

2012-01-01

311

Cross Sections for Electron Impact Excitation of Ions Relevant to Planetary Atmospheres Observation  

NASA Technical Reports Server (NTRS)

The goal of this research grant was to calculate accurate oscillator strengths and electron collisional excitation strengths for inelastic transitions in atomic species of relevance to Planetary Atmospheres. Large scale configuration-interaction atomic structure calculations have been performed to obtain oscillator strengths and transition probabilities for transitions among the fine-structure levels and R-matrix method has been used in the calculations of electron-ion collision cross sections of C II, S I, S II, S III, and Ar II. A number of strong features due to ions of sulfur have been detected in the spectra of Jupiter satellite Io. The electron excitation cross sections for the C II and S II transitions are studied in collaboration with the experimental atomic physics group at the Jet Propulsion Laboratory. There is excellent agreement between experiment and theory which provide an accurate and broad-base test of the ability of theoretical methods used in the calculation of atomic processes. Specifically, research problems have been investigated for: electron impact excitation cross sections of C II: electron impact excitation cross sections of S III; energy levels and oscillator strengths for transitions in S III; collision strengths for electron collisional excitation of S II; electron impact excitation of inelastic transitions in Ar II; oscillator strengths of fine-structure transitions in neutral sulfur; cross sections for inelastic scattering of electrons from atomic nitrogen; and excitation of atomic ions by electron impact.

Tayal, Swaraj S.

1998-01-01

312

Synergistic Study of Hydrocarbon Photochemistry in the Laboratory and Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

A synergistic study of hydrocarbon photochemistry in the laboratory and planetary atmospheres has been carried out using the Caltech/JPL KINETICS photochemical model and laboratory measurements from Adamkovics and Boering (2003). The laboratory simulations provide the data for the time-evolution of gaseous species such as H2, C2H2, C2H4, C2H6, C3H4, C4H2 and C4H10 during UV irradiation of CH4. We apply forward and adjoint models to analyze the experiments. Different photochemical schemes (e.g., Moses et al. 2000, 2005) are compared and modified to reproduce the laboratory results. We first test the full sensitivity of the model results to all chemical kinetics using the adjoint model and show that the abundances of C2H2, C2H4, C2H6, and C4H10 can be well reproduced while that of C4H2 is underestimated by 1-2 orders of magnitude. The abundance of C3H4 is underestimated with Moses et al. (2000) kinetics but overestimated with Moses et al. (2005) kinetics. This suggests a major gap in our understanding of chemical pathways to higher hydrocarbons. We next examine higher order hydrocarbon chemistry (>C2). In this case, we assume that all rate coefficients for the chemistry of C1 and C2 hydrocarbons remain invariant in the adjoint optimization. Better agreement is achieved, but complete agreement remains elusive. Further laboratory measurements are urgently needed to constrain the pathways. The implications for modeling the atmospheres of Titan and the giant planets (e.g., Jupiter) are discussed.

Liang, M. C.; Henze, D.; Adamkovics, M.; Chu, E. F.; Boering, K.; Yung, Y. L.

2009-04-01

313

Condensates from stellar protoplanetary nebulae: Implications for heavy element and volatile enrichment in extrasolar planets  

Microsoft Academic Search

The study of planetary systems around other stars is rapidly expanding to include spectral data on the composition of extrasolar planets. These can be interpreted in the context of what we know about the origin and evolution of our own solar system. Planetary characteristics are strongly affected by the composition of the solid material condensed from the protoplanetary stellar nebula

T. V. Johnson; J. I. Lunine; O. Mousis

2010-01-01

314

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.

315

Brown Dwarfs and Extrasolar Planets  

Microsoft Academic Search

Brown dwarfs bridge the gap between the stellar and planetary mass regimes and, as they cool, their atmospheres evolve towards conditions most commonly associated with planets. Despite differences (e.g., formation and proximity to a stellar companion), it is interesting to know just how much of the knowledge gained by studying brown dwarfs can be directly applied when predicting the thermal

F. Allard; I. Baraffe; G. Chabrier; T. S. Barman; P. H. Hauschildt

2003-01-01

316

Venus observed as an extrasolar planet  

NASA Astrophysics Data System (ADS)

In a relatively near future, numerous transiting extrasolar planets will be discovered {gaseous giant planets, Earth-size planets and temperate Uranus in the form of "Ocean-planets"}. Space telescopes operating in the UV-optical-IR will allow the study of their atmospheres. We have to show if and how these observations will give access to the detection of atmospheric species, particularly when telluric planets will be observed, to demonstrate that life may be possible on one of them. For that purpose, we propose to use the unique event of the century, the Venus transit in 2012 {next Venus transits are in 2117 and 2125!}, to demonstrate the feasibility of these observations and show precisely what a Venus-like planet will look-like. To observe the Venus transit with similar conditions as extrasolar planets {no spatial resolution}, we propose to observe the solar light reflected on the Moon during the Venus transit on June 5-6 2012, lasting about 7h 40mn, i.e. about 4 HST orbits. A total of 5 HST orbits will allow us to obtain high S/N transit spectra and reference spectra to reveal the detectable atmospheric species with current space instrumentations. Similarly, in a companion proposal, we propose to observe the Earth transit on the Moon through the reflected light during a total Moon eclipse to directly compare the observed atmospheric signatures of Earth-like and Venus-like extrasolar planets.

Ehrenreich, David

2011-10-01

317

Planetary Surface Instruments Workshop  

NASA Technical Reports Server (NTRS)

This report on planetary surface investigations and planetary landers covers: (1) the precise chemical analysis of solids; (2) isotopes and evolved gas analyses; (3) planetary interiors; planetary atmospheres from within as measured by landers; (4) mineralogical examination of extraterrestrial bodies; (5) regoliths; and (6) field geology/processes.

Meyer, Charles (Editor); Treiman, Allan H. (Editor); Kostiuk, Theodor (Editor)

1996-01-01

318

The D to H ratio on Titan and the planets: Implications for origin and evolution of planetary atmospheres  

NASA Technical Reports Server (NTRS)

Measurements of deuterated methane show that Titan's atmosphere is enriched by at least several times in deuterium compared to the major planets. Potential causative factors for this enrichment are condensation to form tropospheric methane clouds, fractionation occuring over a hypothetical CH4-C2H2 ocean and between the ocean and the clathrate crust beneath, fractionation which occurred during the formation of Titan and fractionation occuring as a result of the evolution of Titan's atmosphere. The greater part of the observed fractionation is probably derived from the formation of Titan and the subsequent evolution of Titan atmosphere driven by photochemistry. The latter process is developed here for the first time. The D/H ratio in a planetary atmosphere is one readily available measure of the origin and evolution of the hydrogen bearing volatiles on the planet. Comparison between D/H ratio in the inner solar system and the outer solar system may pose important constraints on current theories.

Pinto, J. P.; Lunine, J. I.; Kim, S. J.; Yung, Y. L.

1986-01-01

319

Modelling of N2 Vegard-Kaplan and LBH emissions in the planetary atmospheres  

NASA Astrophysics Data System (ADS)

The N_{2} triplet band emissions are common features in the dayglow of Earth. Recent discoveries of N _{2} Vegard-Kaplan (VK) band emissions on Mars by SPICAM/Mars-Express and N _{2} VK and LBH band emissions on Titan by Cassini's UVIS have led planetary scientists to look for the processes governing the N _{2} triplet and singlet band emissions in different planetary atmospheres. We have developed a model to calculate N _{2} triplet and Lyman-Birge-Hopefield (LBH) band emissions in the dayglow of Venus, Mars, Titan, and Pluto. The Steady state photoelectron fluxes and volume excitation rates have been calculated using the Analytical Yield Spectra (AYS) technique. Since interstate cascading is important for triplet and singlet states of N _{2}, the population of any given level of N _{2} triplet and singlet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet and singlet states is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK ( A(3Sigma_u^+) - X(1Sigma^+_g) ), first positive ( B(3Pi_g) - A(3Sigma^+_u) ), second positive ( C(3Pi_u) - B(3Pi_g) ), Wu-Benesch (W(3Delta_u) - B(3Pi_g) ), B '-> B, E -> B, E-> C, E-> A, and LBH (a(1Pi_g) - X(1Sigma^+_g) ) bands of N _{2}. The N _{2} VK band span wavelength range from far ultraviolet to visible, and some transitions even originate at wavelength more than 1000 nm. Our calculations show that the overhead intensity of VK bands in the wavelength range 400-800, 300-190, 200-300, and 150-200 nm are 22%, 39%, 35%, and 4% of the total VK band emission. On Titan, the calculated intensities of N _{2} VK and LBH bands in 150-190 and 120-190 nm wavelength range, respectively, are in good agreement with the Cassini-UVIS observation. On Mars, calculated intensities of N _{2} VK bands are in agreement with the SPICAM observed limb profile of N _{2} VK (0-6) when the N _{2} density in Martian upper atmosphere is reduced by a factor of 3. Calculations are also carried out on Venus using this model. Calculated intensities on Venus are about factor of 10 higher than that on Mars. On Pluto, the predicted limb intensities of N _{2} VK and LBH bands for New Horizons flyby condition peak at radial distance of 2000 km with a value of about 5 and 9.5 R, respectively for solar zenith angle 60(°) . The results will presented and discussed.

Jain, Sonal Kumar; Bhardwaj, Anil

320

The Compositional Diversity of Extrasolar Terrestrial Planets. II. Migration Simulations  

NASA Astrophysics Data System (ADS)

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.; O'Brien, David P.; Raymond, Sean N.

2012-11-01

321

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

322

The Martian atmosphere above great volcanoes: Early planetary Fourier spectrometer observations  

NASA Astrophysics Data System (ADS)

This work reports the first observations of the Martian atmosphere returned by the planetary Fourier spectrometer (PFS) on board of Mars express (MEX) satellite in the vicinity of the greatest volcanic domes of the planet. Two of the early MEX orbits have already covered the region of Olympus Mons and Ascraeus Mons. These measurements are very similar in terms of local time (14LT) and season ( L=337 and 342, respectively). The long wavelength channel (LWC) of the instrument works in the thermal IR (300-1500 cm -1); its data allow the simultaneous retrieval of surface temperature, integrated content of water ice and dust suspended in the atmosphere and air thermal field up to an altitude of about 50 km. Results of the code described in the companion paper by Grassi et al. for the two orbits are presented and compared with the state expected by the European Martian climate dataset v3.1. The parent global circulation model LMD-Oxford-AAS is able to take into account a wide number of physical phenomena, but the results included in EMCD are affected by a relatively coarse spatial resolution, that does not properly describe the great volcanic domes. The comparison demonstrated that observed data follow quite strictly the trends foreseen by the model in low altitude regions, while the behavior shows remarkable differences above the relief, where orography likely plays an important role. Namely, extended mid-altitude minima in air temperature fields above the summit of volcanic domes are observed. The integrated content of dust shows a minima above Olympus, as expected for a dust particle concentration that decays with height. Measurements are consistent with an exponential decay characterized by a scale height of ˜10 km. Consistently, the surface temperature presents a maxima over the dome, as expected for conditions of clearer sky. Water ice clouds are clearly detected around Ascreus Mons, with a strong asymmetry in latitude. Further comparison with the results of the thermal emission spectrometer (TES) on board of Mars global surveyor (MGS) is also provided, partially supporting our observations of air temperature fields. Possible explanation of these trends is represented by thermal circulation, driven by air heating close to the surface. If confirmed by future observations, these data can represent important constraint by PFS data to mesospheric simulation, with possible implications on the Global Circulation Models.

Grassi, D.; Fiorenza, C.; Zasova, L. V.; Ignatiev, N. I.; Maturilli, A.; Formisano, V.; Giuranna, M.

2005-08-01

323

Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane  

NASA Technical Reports Server (NTRS)

Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

Blass, William E.; Daunt, Stephen J.; Peters, Antoni V.; Weber, Mark C.

1990-01-01

324

Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets  

Microsoft Academic Search

Opacities and chemical abundance data are crucial ingredients of ultracool dwarf and extrasolar giant planet atmosphere models. We report here on the detailed sources of molecular opacity data employed by our group for this application. We also present tables of Rosseland and Planck mean opacities, which are of use in some studies of the atmospheres, interiors, and evolution of planets

Richard S. Freedman; Mark S. Marley; Katharina Lodders

2008-01-01

325

Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation  

E-print Network

We apply hydrodynamic evaporation models to different synthetic planet populations that were obtained from a planet formation code based on a core-accretion paradigm. We investigated the evolution of the planet populations using several evaporation models, which are distinguished by the driving force of the escape flow (X-ray or EUV), the heating efficiency in energy-limited evaporation regimes, or both. Although the mass distribution of the planet populations is barely affected by evaporation, the radius distribution clearly shows a break at approximately 2 $R_{\\oplus}$. We find that evaporation can lead to a bimodal distribution of planetary sizes (Owen & Wu 2013) and to an "evaporation valley" running diagonally downwards in the orbital distance - planetary radius plane, separating bare cores from low-mass planet that have kept some primordial H/He. Furthermore, this bimodal distribution is related to the initial characteristics of the planetary populations because low-mass planetary cores can only acc...

Jin, Sheng; Parmentier, Vivien; van Boekel, Roy; Henning, Thomas; Ji, Jianghui

2014-01-01

326

Analytic evaluation of the weighting functions for remote sensing of blackbody planetary atmospheres : the case of limb viewing geometry  

NASA Technical Reports Server (NTRS)

In a recent publication (Ustinov, 2002), we proposed an analytic approach to evaluation of radiative and geophysical weighting functions for remote sensing of a blackbody planetary atmosphere, based on general linearization approach applied to the case of nadir viewing geometry. In this presentation, the general linearization approach is applied to the limb viewing geometry. The expressions, similar to those obtained in (Ustinov, 2002), are obtained for weighting functions with respect to the distance along the line of sight. Further on, these expressions are converted to the expressions for weighting functions with respect to the vertical coordinate in the atmosphere. Finally, the numerical representation of weighting functions in the form of matrices of partial derivatives of grid limb radiances with respect to the grid values of atmospheric parameters is used for a convolution with the finite field of view of the instrument.

Ustinov, Eugene A.

2006-01-01

327

LINE AND MEAN OPACITIES FOR ULTRACOOL DWARFS AND EXTRASOLAR PLANETS Richard S. Freedman1  

E-print Network

LINE AND MEAN OPACITIES FOR ULTRACOOL DWARFS AND EXTRASOLAR PLANETS Richard S. Freedman1 and Mark S in the literature at densities relevant to the atmospheres and interiors of giant planets and brown dwarfs. We dwarfs and extrasolar planets ultimately de- pends on an entire suite of molecular and atomic opacities

Fegley Jr., Bruce

328

Characterization of extrasolar terrestrial planets from diurnal photometric variability  

NASA Astrophysics Data System (ADS)

The detection of massive planets orbiting nearby stars has become almost routine, but current techniques are as yet unable to detect terrestrial planets with masses comparable to the Earth's. Future space-based observatories to detect Earth-like planets are being planned. Terrestrial planets orbiting in the habitable zones of stars-where planetary surface conditions are compatible with the presence of liquid water-are of enormous interest because they might have global environments similar to Earth's and even harbour life. The light scattered by such a planet will vary in intensity and colour as the planet rotates; the resulting light curve will contain information about the planet's surface and atmospheric properties. Here we report a model that predicts features that should be discernible in the light curve obtained by low-precision photometry. For extrasolar planets similar to Earth, we expect daily flux variations of up to hundreds of per cent, depending sensitively on ice and cloud cover as well as seasonal variations. This suggests that the meteorological variability, composition of the surface (for example, ocean versus land fraction) and rotation period of an Earth-like planet could be derived from photometric observations. Even signatures of Earth-like plant life could be constrained or possibly, with further study, even uniquely determined.

Ford, E. B.; Seager, S.; Turner, E. L.

2001-08-01

329

Imaging Extrasolar Planets from the Ground  

NASA Astrophysics Data System (ADS)

An approach to direct imaging of extrasolar planets is described, in which adaptive optics to correct atmospheric aberration are based on interferometric measurements made in the focal plane. In order to minimize the weak, residual speckles of the stellar halo, their complex amplitudes are first determined using photon-counting, spectrally-resolved imaging sensors. Corrections to both the corrugation and intensity of the wavefront are then derived by Fourier transform and applied using a pair of deformable mirrors. In this way the systematic and non-common path errors of pupil wavefront sensing methods are avoided, and the resulting high accuracy correction should allow detection of giant extrasolar planets with existing large telescopes. With new ground-based telescopes of approximately 20 meter or larger aperture, detection and even spectroscopy of nearby earth-like planets should be possible.

Angel, R.

330

The Young and Restless Sun: Effects of the Young Sun's Strong Magnetic Activity on Paleo-Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Studies of young solar proxies (G0-G5 V stars), as part of the ``Sun in Time'' program, show that the young Sun was rotating over 10× faster than today. As a consequence, these young solar type stars (including the young Sun) had vigorous magnetic dynamos and correspondingly strong coronal X-ray and EUV emissions and chromospheric FUV and UV emissions - up to several hundred times stronger than that observed for the present Sun. Also, observations of the youngest solar proxies indicate that the young Sun had frequent and powerful flares and most likely significant winds. The results of the ``Sun in Time'' program will be discussed that show the decline of solar coronal and chromospheric activity with slower rotation and increasing age. Also discussed are some of the major effects that the young Sun's strong magnetic activity may have had on the photoionization, photochemistry, and erosion of paleo-planetary atmospheres. Some examples that will be briefly discussed include: the possible erosion of Mercury's mantle, loss of water on Mars and the oxidation of its surface, hydrodynamic mass loss from paleo planetary atmospheres, and the evolution of the Earth's atmosphere and the origin and evolution of life on Earth (and maybe on Mars). This work was supported by NASA/FUSE grants NAG 5-12125, NAG 5-10387 and NNG04GC76G.

Guinan, E. F.; DeWarf, L. E.; Ribas, I.; Lammer, H.

2004-05-01

331

Direct detection of C4H2 photochemical products - Possible routes to complex hydrocarbons in planetary atmospheres  

NASA Technical Reports Server (NTRS)

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, C8H2, and C8H3. Neither C6H2 or 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 catalyzing the recombination of free hydrogen atoms in the planetary atmospheres.

Bandy, Ralph E.; Lakshminarayan, Chitra; Frost, Rex K.; Zwier, Timothy S.

1992-01-01

332

Pervasive orbital eccentricities dictate the habitability of extrasolar earths.  

PubMed

The long-term habitability of Earth-like planets requires low orbital eccentricities. A secular perturbation from a distant stellar companion is a very important mechanism in exciting planetary eccentricities, as many of the extrasolar planetary systems are associated with stellar companions. Although the orbital evolution of an Earth-like planet in a stellar binary system is well understood, the effect of a binary perturbation on a more realistic system containing additional gas-giant planets has been very little studied. Here, we provide analytic criteria confirmed by a large ensemble of numerical integrations that identify the initial orbital parameters leading to eccentric orbits. We show that an extrasolar earth is likely to experience a broad range of orbital evolution dictated by the location of a gas-giant planet, which necessitates more focused studies on the effect of eccentricity on the potential for life. PMID:20879864

Kita, Ryosuke; Rasio, Frederic; Takeda, Genya

2010-09-01

333

Extrasolar Planet Inferometric Survey (EPIcS)  

NASA Technical Reports Server (NTRS)

The discovery of the nature of the solar system was a crowning achievement of Renaissance science. The quest to evaluate the properties of extrasolar planetary systems is central to both the intellectual understanding of our origins and the cultural understanding of humanity's place in the Universe; thus it is appropriate that the goals and objectives of NASA's breakthrough Origins program emphasize the study of planetary systems, with a focus on the search for habitable planets. We propose an ambitious research program that will use SIM - the first major mission of the Origins program - to explore planetary systems in our Galactic neighborhood. Our program is a novel two-tiered SIM survey of nearby stars that exploits the capabilities of SIM to achieve two scientific objectives: (i) to identify Earth-like planets in habitable regions around nearby Sunlike stars: and (ii) to explore the nature and evolution of planetary systems in their full variety. The first of these objectives was recently recommended by the Astronomy and Astrophysics Survey Committee (the McKee-Taylor Committee) as a prerequisite for the development of the Terrestrial Planet Finder mission later in the decade. Our program combines this two-part survey with preparatory and contemporaneous research designed to maximize the scientific return from the limited and thus precious observing resources of SIM.

Shao, Michael; Baliunas, Sallie; Boden, Andrew; Kulkarni, Shrinivas; Lin, Douglas N. C.; Loredo, Tom; Queloz, Didier; Shaklan, Stuart; Tremaine, Scott; Wolszczan, Alexander

2004-01-01

334

Infrared extinction spectra of aerosols with relevance to planetary and lunar atmospheres. I: Single-component aerosols  

NASA Astrophysics Data System (ADS)

Mid-infrared extinction spectra (500-6000 cm-1) of a series of single-component aerosol particle ensembles representative of those found in a range of planetary and lunar atmospheres are presented. The aerosols were generated in the laboratory via condensation from the gas phase in a bath gas cooling cell, and the spectra recorded using a Fourier transform infrared spectrometer. This paper is the first in a series aimed towards building a spectral database for use in remote sensing of aerosols. The aerosol substances included here are methane, ethane, propane, butane, pentane, ethylene, acetylene, carbon dioxide, ammonia and sulfur dioxide.

Knox, Kerry J.; Lang, E. Kathrin; Signorell, Ruth

2012-02-01

335

Schumann resonance: a tool to study planetary atmospheric electricity and the origin and evolution of the solar system  

NASA Astrophysics Data System (ADS)

Investigation of extremely low frequency electromagnetic waves produced by lightning activity has been used to assist the characterization of a variety of phenomena related to atmospheric electricity in the Earth environment. Detection of Schumann Resonance spectral features of the earth-ionosphere cavity from outside the cavity offers new remote sensing capabilities to assess tropospheric-space weather connections, namely periodic patterns observed in a variety of tropospheric, ionospheric, and magnetospheric processes. A link between the water mixing ratio and atmospheric electrical conductivity makes Schumann resonance a suitable tool to assess volatile abundance of the outer planets, offering new capabilities to constrain thermodynamic parameters of the protosolar nebula from which the solar system evolved. In this work we discuss a technique and associated instrumentation to detect Schumann resonance signatures of planetary environments and subsequently to infer the fraction of volatiles and to investigate weather patterns in the gaseous envelopes of the giant planets.

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

2012-12-01

336

A Massively Parallel Particle Code for Rarefied Ionized and Neutral Gas Flows in Earth and Planetary Atmospheres, Ionospheres and Magnetospheres  

NASA Technical Reports Server (NTRS)

In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important.

Combi, Michael R.

2004-01-01

337

Planetary Population Synthesis Coupled with Atmospheric Escape: A Statistical View of Evaporation  

NASA Astrophysics Data System (ADS)

We apply hydrodynamic evaporation models to different synthetic planet populations that were obtained from a planet formation code based on the core-accretion paradigm. We investigated the evolution of the planet populations using several evaporation models, which are distinguished by the driving force of the escape flow (X-ray or EUV), the heating efficiency in energy-limited evaporation regimes, or both. Although the mass distribution of the planet populations is barely affected by evaporation, the radius distribution clearly shows a break at approximately 2 R ?. We find that evaporation can lead to a bimodal distribution of planetary sizes and to an "evaporation valley" running diagonally downward in the orbital distance—planetary radius plane, separating bare cores from low-mass planets that have kept some primordial H/He. Furthermore, this bimodal distribution is related to the initial characteristics of the planetary populations because low-mass planetary cores can only accrete small primordial H/He envelopes and their envelope masses are proportional to their core masses. We also find that the population-wide effect of evaporation is not sensitive to the heating efficiency of energy-limited description. However, in two extreme cases, namely without evaporation or with a 100% heating efficiency in an evaporation model, the final size distributions show significant differences; these two scenarios can be ruled out from the size distribution of Kepler candidates.

Jin, Sheng; Mordasini, Christoph; Parmentier, Vivien; van Boekel, Roy; Henning, Thomas; Ji, Jianghui

2014-11-01

338

A statistical mechanics barotropic energy-enstrophy theory for super-rotation in planetary atmospheres  

E-print Network

A statistical mechanics barotropic energy-enstrophy theory for super-rotation in planetary possibilities for the energy sources, amongst which are baroclinic instability driven by solar radiation and Computational Science, National university of Singapore September 30 2000 Abstract A statistical mechanics

Lim, Chjan C.

339

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

340

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

341

Pressure Effects on Product Channels of Hydrocarbon Radical-Radical Reactions; Implications for Modelling of Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Previously we had studied the kinetics and product channels of small unsaturated hydrocarbon radical (C2 and C3s) reactions relevant to planetary atmospheric modelling. Reactions of C2 radicals (such as vinyl, H2CCH and ethynyl C2H) and C3 radicals (such as propargyl, HCCCH2 and allyl, H2CCCH3) can affect the abundances of a large number of stable observable C3, C4, C5, C6 and larger molecules, including linear, aromatic and even poly aromatic molecules. We have experimentally determined pressuredependent product yields for self- and cross-radical reactions performed at 298 K and at selected pressures between ~4 Torr (0.5 kPa) and 760 Torr (101 kPa). Final products were determined by gas chromatograph with mass spectrometry/flame ionization detection (GC/MS/FID). In some cases complementary computational studies extended the pressure and temperature range of the observations and provided valuable information on complex reaction mechanisms. These studies provide a systematic framework so that important energetic and structural parameters for radical-radical reactions can be assessed. Here we report a compilation of our earlier results relevant to planetary atmospheres in addition to recent ones for allyl radical (H2CCCH3) reactions.

Fahr, A.; Halpern, J.; N'doumi, M.

2011-10-01

342

Elemental Compositions of Two Extrasolar Rocky Planetesimals  

NASA Astrophysics Data System (ADS)

We report Keck/HIRES and Hubble Space Telescope/COS spectroscopic studies of extrasolar rocky planetesimals accreted onto two hydrogen atmosphere white dwarfs, G29-38 and GD 133. In G29-38, eight elements are detected, including C, O, Mg, Si, Ca, Ti, Cr, and Fe while in GD 133, O, Si, Ca, and marginally Mg are seen. These two extrasolar planetesimals show a pattern of refractory enhancement and volatile depletion. For G29-38, the observed composition can be best interpreted as a blend of a chondritic object with some refractory-rich material, a result from post-nebular processing. Water is very depleted in the parent body accreted onto G29-38, based on the derived oxygen abundance. The inferred total mass accretion rate in GD 133 is the lowest of all known dusty white dwarfs, possibly due to non-steady state accretion. We continue to find that a variety of extrasolar planetesimals all resemble to zeroth order the elemental composition of bulk Earth. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Xu, S.; Jura, M.; Koester, D.; Klein, B.; Zuckerman, B.

2014-03-01

343

The Search for the Extrasolar Planets: A Brief History of the Search, the Findings and the Future Implications  

NSDL National Science Digital Library

This website gives an extensive outline of the history and results of the discovery of extrasolar planets. Topics inlcude planetary like objects orbiting pulsars and recent work being done by scientists detecting extra solar planetary systems and objects. References are included.

Bell, George

2004-07-16

344

Microfabricated Two-plate Ion Traps: A New Tool for Planetary Atmosphere Analysis  

NASA Astrophysics Data System (ADS)

Mass spectrometers are an important analytical tool in planetary exploration because of their high chemical specificity, high sensitivity, and the application to a wide variety of sample and analyte types. We have developed a novel miniature ion trap mass spectrometer using microfabrication techniques. The mass analyzer is made using two ceramic plates, the facing surfaces of which are patterned with electrodes using microlithography. Appropriate electrical potentials applied to the patterns yield quadrupole trapping fields. High mass resolution, in excess of 1000, has been demonstrated in the lab. This device combines small size, low mass, excellent mechanical ruggedness, and low-power operation. Tandem mass analysis has been demonstrated, and would be particularly useful in identification of unknown compounds. Funding on this development has been from the NASA Planetary Instrument Definition and Development Program.

Austin, Daniel

2009-09-01

345

Reflected light from 3D exoplanetary atmospheres and simulation of HD 209458b  

E-print Network

We present radiation transfer models that demonstrate that reflected light levels from three dimensional (3D) exoplanetary atmospheres can be more than 50% lower than those predicted by models of homogeneous or smooth atmospheres. Compared to smooth models, 3D atmospheres enable starlight to penetrate to larger depths resulting in a decreased probability for the photons to scatter back out of the atmosphere before being absorbed. The increased depth of penetration of starlight in a 3D medium is a well known result from theoretical studies of molecular clouds and planetary atmospheres. For the first time we study the reflectivity of 3D atmospheres as a possible explanation for the apparent low geometric albedos inferred for extrasolar planetary atmospheres. Our models indicate that 3D atmospheric structure may be an important contributing factor to the non-detections of scattered light from exoplanetary atmospheres. We investigate the self-shadowing radiation transfer effects of patchy cloud cover in 3D scattered light simulations of the atmosphere of HD209458b. We find that, for a generic planet, geometric albedos can be as high as 0.45 in some limited situations, but that in general the geometric albedo is much lower. We conclude with some explanations on why extrasolar planets are likely dark at optical wavelengths.

Ben Hood; Kenneth Wood; Sara Seager; Andrew Collier Cameron

2008-07-10

346

Photometric Orbits of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

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 & 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.

2009-09-01

347

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

348

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

NASA Technical Reports Server (NTRS)

Radio absorptivity data for the Venus middle atmosphere (1 to 6 atm, temperatures from 500 to 575K) obtained from spacecraft radio occultation experiments (at 3.6 to 13.4 cm wavelengths) and earth-based radio astronomical observations (1 to 3 cm wavelength range) are compared to laboratory observations at the latter wavelength range under simulated Venus conditions to infer abundances of microwave-absorbing atmospheric constituents, i.e. H2SO4 in a CO2 atmosphere.

Steffes, P. G.

1985-01-01

349

Work output of planetary atmospheric engines: dissipation in clouds and rain  

E-print Network

not provide enough work to lift the condensate against gravity. INDEX TERMS: 0343 Atmospheric Composition as the original function of steam engines was to lift water, a principal output of the atmospheric heat engine (the average surface temperature of 288K) and ÁT $38K, the difference between T and the effective

Lorenz, Ralph D.

350

CARBON-RICH MOLECULAR CHAINS IN PROTOPLANETARY AND PLANETARY ATMOSPHERES: QUANTUM MECHANISMS AND ELECTRON ATTACHMENT RATES FOR ANION FORMATION  

SciTech Connect

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{sub n}H and HC{sub 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.; Grassi, T.; Gianturco, F. A. [Department of Chemistry and CNISM, University of Rome ''Sapienza'', Piazzale Aldo Moro 5, 00185 Rome (Italy); Satta, M., E-mail: francesco.gianturco@uniroma1.it [CNR-ISMN and University of Rome ''Sapienza'', Piazzale Aldo Moro 5, 00185 Rome (Italy)

2013-09-10

351

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

352

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

353

* Corresponding author. Present address: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Fax: #617-253-4464.  

E-print Network

* Corresponding author. Present address: Department of Earth, Atmospheric and Planetary Sciences@ocean.mit.edu (S. Khatiwala). Deep-Sea Research I 48 (2001) 1423}1441 Age tracers in an ocean GCM S. Khatiwala*, M. Visbeck, P. Schlosser Lamont}Doherty Earth Observatory and Department of Earth and Environmental Sciences

Khatiwala, Samar

354

Analysis of stellar occultation data - Effects of photon noise and initial conditions. [planetary atmosphere temperature, pressure and density profiles from occultation light curve  

NASA Technical Reports Server (NTRS)

An occultation light curve can be analyzed to provide information about a planetary atmosphere. Temperature, pressure, and number density profiles for the atmosphere of Mars are derived from a series of boundary layer equations, which invert equal increments of altitude (as opposed to time) in order to predict the noise quality of the occultation. Numerical results are given for a noisy isothermal light curve, with special attention to error analysis.

French, R. G.; Elliot, J. L.; Gierasch, P. J.

1978-01-01

355

Extrasolar Carbon Planets  

E-print Network

We suggest that some extrasolar planets 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 enhancement of the protoplanetary disk's C/O ratio above solar, a condition that pileups of carbonaceous grains may create in ordinary protoplanetary disks. Hot, Neptune-mass carbon planets should show a significant paucity of water vapor in their spectra compared to hot planets with solar abundances. Cooler, less massive carbon planets may show hydrocarbon-rich spectra and tar-covered surfaces. The high sublimation temperatures of diamond, SiC, and other carbon compounds could protect these planets from carbon depletion at high temperatures.

Kuchner, M J; Kuchner, Marc J.

2005-01-01

356

Extrasolar Carbon Planets  

E-print Network

We suggest that some extrasolar planets 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 enhancement of the protoplanetary disk's C/O ratio above solar, a condition that pileups of carbonaceous grains may create in ordinary protoplanetary disks. Hot, Neptune-mass carbon planets should show a significant paucity of water vapor in their spectra compared to hot planets with solar abundances. Cooler, less massive carbon planets may show hydrocarbon-rich spectra and tar-covered surfaces. The high sublimation temperatures of diamond, SiC, and other carbon compounds could protect these planets from carbon depletion at high temperatures.

Marc J. Kuchner; S. Seager

2005-04-08

357

The long-term stability of extrasolar system HD37124. Numerical study of resonance effects  

Microsoft Academic Search

We describe numerical tools for the stability analysis of extrasolar planetary systems. In particular, we consider the relative Poincaré variables and symplectic integration of the equations of motion. We apply the tangent map to derive a numerically efficient algorithm of the fast indicator Mean Exponential Growth factor of Nearby Orbits (MEGNO), a measure of the maximal Lyapunov exponent, that helps

Krzysztof Gozdziewski; Slawomir Breiter; Wojciech Borczyk

2008-01-01

358

Extrasolar planet population synthesis. I. Method, formation tracks, and mass-distance distribution  

Microsoft Academic Search

Context: With the high number of extrasolar planets discovered by now, it has become possible to use the properties of this planetary population to constrain theoretical formation models in a statistical sense. This paper is the first in a series in which we carry out a large number of planet population synthesis calculations within the framework of the core accretion

C. Mordasini; Y. Alibert; W. Benz

2009-01-01

359

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

360

Introduction to planetary aeronomy  

Microsoft Academic Search

This work examines problems in theoretical planetary aeronomy, involving the study of the structure, dynamics, energetics, and radiation state of planetary upper atmospheres (comprising neutral atmosphere, ionosphere, and plasmasphere). The proposed mathematical approach includes elements of the kinetic theory of gases and approximations of multicomponent radiative gasdynamics; heat and mass transfer processes are also considered. The properties of the upper

Mikhail Iakovlevich Marov; Aleksandr Vladimirovich Kolesnichenko

1987-01-01

361

Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets  

Microsoft Academic Search

Opacities and chemical abundance data are crucial ingredients of ultracool\\u000adwarf and extrasolar giant planet atmosphere models. We report here on the\\u000adetailed sources of molecular opacity data employed by our group for this\\u000aapplication. We also present tables of Rosseland and Planck mean opacities\\u000awhich are of use in some studies of the atmospheres, interiors, and evolution\\u000aof planets

Richard S. Freedman; Mark S. Marley; Katharina Lodders

2007-01-01

362

Magnetic communication scenarii for close-in extrasolar planets  

NASA Astrophysics Data System (ADS)

Close-in extrasolar planetary systems are often considered to be scaled up versions of Jupiter and its satellite, Io, which exhibit a strong electromagnetic interaction. Still, this scenario lacks detailed modeling to show its feasibility. We try to fill this gap by studying the magnetic interaction of close-in extrasolar planes and their stars on the basis of realistic stellar wind models and numerical simulations in the frame of resistive magneto-hydrodynamics. We find that a current system between the planet and its star may be established. Contrary to Io and Jupiter it seems to be unlikely that the flux tubes connecting the planet and the star are the source region for radio emissions due to a cyclotron maser instability. Therefore, we suggest that the energy contained in the current system may be dissipated in the chromosphere of the star. This is indicated by observations of an enhanced chromospheric activity on HD 179949.

Preusse, S.; Kopp, A.; Büchner, J.; Motschmann, U.

2006-02-01

363

Outer satellite atmospheres: Their extended nature and planetary interactions. [sodium cloud of Io, hydrogen torus of Titan, and comet atmospheres  

NASA Technical Reports Server (NTRS)

Highly developed numerical models are applied to interpret extended-atmosphere data for the sodium cloud of Io and the hydrogen torus of Titan. Solar radiation pressure was identified and verified by model calculations as the mechanism to explain two different east-west asymmetries observed in the sodium cloud. Analysis of sodium line profile data, suggesting that a Jupiter magnetospheric wind may be responsible for high speed sodium atoms emitted from Io, and preliminary modeling of the interaction of the Io plasma torus and Io's sodium cloud are also reported. Models presented for Titan's hydrogen torus are consistent both with the recent Pioneer 11 measurements and earlier Earth-orbiting observations by the Copernicus satellite. Progress is reported on developing models for extended gas and dust atmospheres of comets.

Smyth, W. H.

1980-01-01

364

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

Microsoft Academic Search

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

Mao-Chang Liang

2006-01-01

365

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

366

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

367

EXTRASOLAR PLANETS Awhiffofmethane  

E-print Network

- pheres in our Solar System: those of Earth, Mars, Titan and the gas giants, Jupiter, Saturn, Uranus planetary formation, evolution, weather, photochemistry and -- in the case of Earth -- life. We have amorerobust estimateof itsabun- dance. The planet is a `hot Jupiter' that orbits only 0.03 Earth­Sun distances

368

Simulating Super Earth Atmospheres in the Laboratory  

NASA Astrophysics Data System (ADS)

The "Atmosphere in a Test Tube" project is a laboratory experiment that will be able to reproduce condition of extreme environments by means of a simulator. These conditions span from those existing inside some parts of the human body to combinations of temperatures, pressures, irradiation and atmospheric gases present on other planets. In this latter case the experiments to be performed will be useful as preliminary tests for both simulation of atmosphere of exoplanets and Solar System planets and Astrobiology experiments that should be performed by planetary landers or by instruments to be launched in the next years. In particular at INAF Astronomical Observatory of Padova Laboratory we are approaching the characterization of extrasolar planet atmospheres taking advantage by innovative laboratory experiments with a particular focus on low mass Neptunes and Super earths and low mass M dwarfs primaries.

Claudi, R.; Erculiani, S. M.

2014-03-01

369

Estimating the height of the planetary boundary layer for transport and diffusion atmospheric models: A four algorithm comparison  

SciTech Connect

The authors present the results of a performance evaluation of four algorithms that determine the height of the Planetary Boundary Layer (PBL) against both forecasted and observed PBL heights derived by human analysis (taken to be the forecasted and observed truth). The PBL height determines the direction and speed of pollution movement, as well as the vertical depth over which the effluent will be mixed, and therefore is important for accurate transport and diffusion modeling. Three of these algorithms are methods used by the Short-range Layered Atmospheric Model (SLAM). Although designed to be used with observed upper-air data, these three methods have been adapted to utilize forecast soundings from the Regional Atmospheric Modeling System (RAMS) forecast model. The fourth method relies on the properties of turbulent kinetic energy (TKE) predicted by the RAMS forecast model to determine PBL heights. The results of the study indicate that two of the three SLAM model algorithms, and the RAMS TKE derived PBL heights all produce reasonable results compared to those derived by human analysis. The results suggest an ensemble approach in which the transport and diffusion calculations are performed using each of the three algorithms may produce the best results.

Russ, R.L.; Dean, D.; Walters, M.K.

1999-07-01

370

Stabilizing planetary evolution through the coupling of magnetic field, surface tectonics, and atmosphere  

NASA Astrophysics Data System (ADS)

We present a method for coupling the evolution of Earth's surface (atmosphere, tectonics) to the interior (mantle convection, core dynamo) by treating the layers as boundary-coupled one dimensional boxes. Initially atmospheric volatiles (H2O and CO2) are degassed from the mantle and remain in the atmosphere until the H2O liquid-vapor (T-P) saturation curve is intersected by the greenhouse surface temperature, at which point precipitation and weathering begins, accumulating a water ocean and buffering atmospheric CO2. Surface plate motion, a critical component of the carbon buffering cycle, is driven by mantle convection as long as the surface temperature remains below a critical value as predicted by numerical experiments using damage rheology. Active surface tectonics also allows for efficient cooling of the mantle and core, driving the core dynamo and maintaining a strong surface magnetic field. We demonstrate that this coupled model self-stabilizes as a strong magnetic field provides shielding against atmospheric erosion by the solar wind, allowing for the retention of a large water-rich atmosphere that is critical to stabilizing a temperate surface environment, surface tectonics, and whole planet cooling. Such a stabilizing feedback is consistent with observations of Earth's roughly constant surface temperature, plate speeds, and magnetic field intensity going back ~3.5 Ga. The model produces a history of Venus with initially active surface tectonics and strong magnetic field before a runaway greenhouse prevents lithospheric damage and subduction, limiting interior cooling and ultimately leading to a decay of the dynamo magnetic field.

Driscoll, P.; Bercovici, D.

2012-04-01

371

Pre-conditioned Backward Monte Carlo solutions to radiative transport in planetary atmospheres. Fundamentals: Sampling of propagation directions in polarising media  

E-print Network

Context. The interpretation of polarised radiation emerging from a planetary atmosphere must rely on solutions to the vector Radiative Transport Equation (vRTE). Monte Carlo integration of the vRTE is a valuable approach for its flexible treatment of complex viewing and/or illumination geometries and because it can intuitively incorporate elaborate physics. Aims. We present a novel Pre-Conditioned Backward Monte Carlo (PBMC) algorithm for solving the vRTE and apply it to planetary atmospheres irradiated from above. As classical BMC methods, our PBMC algorithm builds the solution by simulating the photon trajectories from the detector towards the radiation source, i.e. in the reverse order of the actual photon displacements. Methods. We show that the neglect of polarisation in the sampling of photon propagation directions in classical BMC algorithms leads to unstable and biased solutions for conservative, optically-thick, strongly-polarising media such as Rayleigh atmospheres. The numerical difficulty is avoid...

Muñoz, García; Mills,; P, F

2014-01-01

372

Equilibrium and disequilibrium chemistry of adiabatic, solar-composition planetary atmospheres  

NASA Technical Reports Server (NTRS)

The impact of atmospheric and cloud-structure models on the nonequilibrium chemical behavior of the atmospheres of the Jovian planets is discussed. Quantitative constraints on photochemical, lightning, and charged-particle production of organic matter and chromophores are emphasized whenever available. These considerations imply that inorganic chromophore production is far more important than that of organic chromophores, and that lightning is probably a negligibly significant process relative to photochemistry on Jupiter. Production of complex molecules by gas-phase disequilibrium processes on Saturn, Uranus, and Neptune is severely limited by condensation of even simple intermediates.

Lewis, J. S.

1976-01-01

373

A new inversion method for remote sounding of planetary atmospheres. [spectral lines  

NASA Technical Reports Server (NTRS)

An inversion method which is applicable to high resolution observations where the spectral lines are fully resolved is described. The technique is based on matching calculated slopes of the spectral line profiles with slopes of the observed lineshapes, and involves finding an inverse solution to the derivative of the radiative transfer equation with respect to frequency. The method is applied to inversion of ozone absorption lines in the earth's atmosphere and the results are compared with those obtained by a conventional method. Advantages include narrower weighting functions providing a higher vertical resolution; higher atmospheric level which may be probed, more faster and more stable convergence, and more accurate retrieved profiles.

Abbas, M. M.

1978-01-01

374

Studies of the chemistry of vibrationally and electronically excited species in planetary upper atmospheres  

NASA Technical Reports Server (NTRS)

The vibrational distribution of O2(+) in the atmospheres of Venus and Mars was investigated to compare with analogous values in the Earth's atmosphere. The dipole moment of the Z(2) Pi sub u - X(2) Pi sub g transition of O2(+) is calculated as a function of internuclear distance. The band absorption oscillator strengths and band transition probabilities of the second negative system are derived. The vibrational distribution of O2(+) in the ionosphere of Venus is calculated for a model based on data from the Pioneer Venus neutral mass spectrometer.

Fox, J. L.

1984-01-01

375

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

376

Impact Erosion of Planetary Atmospheres: Some Surprising Results William I. Newman  

E-print Network

able to obtain analytically the particle trajectories in an isothermal atmosphere. The outcome and used a state-of-the-art code (CAVEAT), a hybrid Los Alamos-Sandia Lagrangian-Eulerian finite difference any previous use of such codes. We developed new methods to test the accuracy and convergence

Stewart, Sarah T.

377

Planetary and Space Science 56 (2008) 12 Surfaces and atmospheres of the outer planets,  

E-print Network

during the PS3.02 and PS3.03 sessions of the European Geosciences Union (EGU) meeting in Vienna, Austria and the rings. In particular, there are several studies reported here from session PS3.02 on the Kronian icy PS3.03 included presentations on the neutral atmospheres of the outer planets and Titan--the largest

Atreya, Sushil

378

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

379

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

380

Jupiter-like planets as dynamical barriers to inward-migrating super-Earths: a new understanding of the origin of Uranus and Neptune and predictions for extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

Planets of 1-4 times Earth's size on orbits shorter than 100 days exist around 30-50% of all Sun-like stars. These ``hot super-Earths'' (or ``mini-Neptunes''), or their building blocks, might have formed on wider orbits and migrated inward due to interactions with the gaseous protoplanetary disk. The Solar System is statistically unusual in its lack of hot super-Earths. Here, we use a suite of dynamical simulations to show that gas-giant planets act as barriers to the inward migration of super-Earths initially placed on more distant orbits. Jupiter's early formation may have prevented Uranus and Neptune (and perhaps Saturn's core) from becoming hot super-Earths. It may actually have been crucial to the very formation of Uranus and Neptune. In fact, the large spin obliquities of these two planets argue that they experienced a stage of giant impacts from multi-Earth mass planetary embryos. We show that the dynamical barrier offered by Jupiter favors the mutual accretion of multiple migrating planetary embryos, favoring the formation of a few massive objects like Uranus and Neptune. Our model predicts that the populations of hot super-Earth systems and Jupiter-like planets should be anti-correlated: gas giants (especially if they form early) should be rare in systems with many hot super-Earths. Testing this prediction will constitute a crucial assessment of the validity of the migration hypothesis for the origin of close-in super-Earths.

Morbidelli, Alessandro; Izidoro Da Costa, Andre'; Raymond, Sean

2014-11-01

381

Taxonomy of the extrasolar planet  

E-print Network

When a star is described as a spectral class G2V, we know that the star is similar to our Sun.We know its approximate mass, temperature, age and size. In our work with extrasolar planets database, it is very useful to have a taxonomy scale (classification), for example, like the Harvard classification for stars. This new taxonomy has to be comprehensible and present the important information about extrasolar planets. The important information of extrasolar planets are their mass, radius, period, density, eccentricity, temperature, and their distance from the parent star. There are too many parameters, that is, taxonomy with six parameters would be complicated and difficult to apply. We propose following the extrasolar planet taxonomy scale with only four parameters. The first parameter is the information about the mass of an extrasolar planet in the form of the units of the mass of other known planets, where M - Mercury, E - Earth, N - Neptune, and J - Jupiter. The second parameter is the distance from its pa...

Plávalová, E

2011-01-01

382

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

NASA Technical Reports Server (NTRS)

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. The thickness of the ice is governed principally by the solar flux which penetrates the ice layer and then is conducted back to the surface. Evaporation from the surface is governed by wind and free convection. In the absence of wind, eddy diffusion is caused by the lower density of water vapor in comparison to the density of the Martian atmosphere. For mean martian insolations, the evaporation rate above the ice is approximately 10 to the minus 8th power gm/sq cm/s. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as ice-chocked rivers. Typical equilibrium thicknesses of such ice covers are approximately 10m to 30 m; typical surface temperatures are 210 to 235 K.

Wallace, D.; Sagan, C.

1978-01-01

383

Dynamical Relaxation and Massive Extrasolar Planets  

E-print Network

Following the suggestion of Black (1997) that some massive extrasolar planets may be associated with the tail of the distribution of stellar companions, we investigate a scenario in which 5 < N < 100 planetary mass objects are assumed to form rapidly through a fragmentation process occuring in a disc or protostellar envelope on a scale of 100 au. These are assumed to have formed rapidly enough through gravitational instability or fragmentation that their orbits can undergo dynamical relaxation on a timescale of about 100 orbits. Under a wide range of initial conditions and assumptions the relaxation process ends with either (i) one potential 'hot Jupiter' plus up to two 'external' companions, i.e. planets orbiting near the outer edge of the initial distribution; (ii) one or two 'external' planets or even none at all; (iii) one planet on an orbit with a semi--major axis 10 to a 100 times smaller than the outer boundary radius of the inital distribution together with an 'external' companion. Most of the other objects are ejected and could contribute to a population of free floating planets. Apart from the potential 'hot Jupiters', all the bound objects are on highly eccentric orbits. We found that, apart from the close orbiters, the probability of ending up with a planet orbiting at a given distance from the central star increases with the distance. This is because of the tendency of the relaxation process to lead to collisions with the central star. We discuss the application of these results to some of the more massive extrasolar planets.

J. C. B. Papaloizou; Caroline Terquem

2000-12-18

384

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

385

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

E-print Network

This paper reports on the detection of a planetary system with three Super-Earths orbiting HD40307. HD40307 is a K2V metal-deficient star at a distance of only 13 parsec, part of the HARPS GTO high-precision planet-search programme. The three planets on circular orbits have very low minimum masses of respectively 4.2, 6.9 and 9.2 Earth masses and periods of 4.3, 9.6 and 20.5 days. The planet with the shortest period is the lightest planet detected to-date orbiting a main sequence star. The detection of the correspondingly low amplitudes of the induced radial-velocity variations is completely secured by the 135 very high-quality HARPS observations illustrated by the radial-velocity residuals around the 3-Keplerian solution of only 0.85 m/s. Activity and bisector indicators exclude any significant perturbations of stellar intrinsic origin, which supports the planetary interpretation. Contrary to most planet-host stars, HD40307 has a marked sub-solar metallicity ([Fe/H]=-0.31), further supporting the already raised possibility that the occurrence of very light planets might show a different dependence on host star's metallicity compared to the population of gas giant planets. In addition to the 3 planets close to the central star, a small drift of the radial-velocity residuals reveals the presence of another companion in the system the nature of which is still unknown.

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

2008-06-27

386

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

NASA Technical Reports Server (NTRS)

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.

Valentin, J. R.

1989-01-01

387

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

388

Laboratory studies of atomic collision processes of importance in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Progress in the following research supported under NSG 7386 is reported: (1) measurement of differential cross sections for atomic and molecular collisions relevant to analysis and modeling of data from Pioneer 11, Pioneer 12, Voyager 1, and Voyager 2; (2) analysis of measured differential cross section results to provide scattering data in forms that are easy to apply to atmospheric modeling work; (3) analysis of the data to give basic information on the molecular potentials involved in the scattering process; and (4) development and initial use of apparatus to study dissociative processes in neutral molecules.

Stebbings, R. F.; Smith, K.

1984-01-01

389

An assessment of thermal, wind, and planetary wave changes in the middle and lower atmosphere due to 11-year UV flux variations  

NASA Technical Reports Server (NTRS)

Hines (1974) speculated that solar-induced modifications of the middle and upper atmosphere may alter the transmissivity of the stratosphere to upwardly propagating atmospheric waves. It was suggested that subsequent constructive or destructive interference may result in a change of phase or amplitude of these waves in the troposphere leading to weather or climate changes. The present investigation has the objective to bring together both radiative transfer and planetary wave studies in an effort to assess specifically whether Hines mechanism can be initiated by the solar ultraviolet flux variability assumed to be associated with the 11-year solar cycle. The obtained results suggest that the presently studied mechanism, which links solar-induced zonal wind changes in the stratosphere and mesosphere to planetary wave changes in the troposphere, is not strong enough to cause substantive changes in the troposphere.

Callis, L. B.; Alpert, J. C.; Geller, M. A.

1985-01-01

390

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

391

Atmospheric,OceanicandSpaceSciences Atmospheric, Oceanic & Space Sciences  

E-print Network

/Thermosphere Physics Planetary Magnetospheres Solar & Heliospheric Physics Space Weather Aeronomy For Faculty involved Atmospheric & Space Science Research Areas Numerical Methods & Scientific Computing Planetary Atmospheres

Eustice, Ryan

392

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

393

Water vapor from a lunar breccia - Implications for evolving planetary atmospheres.  

NASA Technical Reports Server (NTRS)

The exposure of a typical complex lunar breccia to hydrogen after a through outgassing produces a fully reduced surface state. Subsequent outgassing over a wide temperature range results in the production of water vapor formed from the chemisorbed hydrogen and oxygen from the lunar sample; the proposed mechanism has been confirmed in terms of the chemisorption of deuterium and the release of heavy water. Since the conditions of the experiments are consistent with those on the lunar surface, it is postulated that water vapor will be produced on the moon through the interaction of the solar wind with lunar soil. It is also proposed that such a process could play an important role in the early history of many planets where an oxygen-rich soil is exposed to a reducing atmosphere.

Cadenhead, D. A.; Buergel, W. G.

1973-01-01

394

Shock-induced CO2 loss from CaCO3: Implications for early planetary atmospheres  

NASA Technical Reports Server (NTRS)

Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines shock-induced CO2 loss as a function of shock pressure. Incipient to complete CO2 loss occurs over a pressure range of approximately 10 to approximately 70 GPa. Optical and scanning electron microscopy reveal structural changes, which are related to the shock-loading. The occurrence of dark, diffuse areas, which can be resolved as highly vesicular areas as observed with a scanning electron microscope are interpreted as representing quenched partial melts, into which shock-released CO2 was injected. The experimental results are used to constrain models of shock-produced, primary CO2 atmospheres on the accreting terrestrial planets.

Lange, M. A.; Ahrens, T. J.

1984-01-01

395

Impact induced dehydration of serpentine and the evolution of planetary atmospheres  

NASA Technical Reports Server (NTRS)

Results of shock recovery experiments carried out on antigorite serpentine Mg3Si2O5(OH)4 are reported. The main objective of the present study is the determination of critical shock pressures for partial and complete dehydration of serpentine under shock loading. It is pointed out that serpentine and serpentine-like layer silicates are the major water-bearing phases in carbonaceous chondrites. It appears that these minerals, and a poorly defined cometary contribution, were the most likely water-bearing phases in accreting planetesimals which led to the formation of the terrestrial planets. The obtained results imply that the process of impact induced devolatilization of volatile bearing minerals during accretion is likely to have occurred on earth. The findings lend support to the model of a terrestrial atmosphere/hydrosphere forming during the later stages of accretion of the earth.

Lange, M. A.; Ahrens, T. J.

1982-01-01

396

Effective optical thickness of the layer in a planetary atmosphere where the observed spectrum of the planet is formed. Concept and simplest estimation  

Microsoft Academic Search

The author proposes an equation to determine the effective optical thickness tau0e of the layer in a semi-infinite planetary atmosphere where the observed spectrum of the planet is formed. The left side of this equation is the ratio between the number of photons that have stayed for a time below the tau0e level and the total number of photons reflected

Eh. G. Yanovitskij

1997-01-01

397

ExtraSolar Planets Finding Extrasolar Planets. I  

E-print Network

close to the star. #12;Orbits Planets do not orbit the Sun - they both orbit the center of mass Planets. III Transits Six planets have been found by transits. This requires an edge-on orbit. JupiterExtraSolar Planets #12;Finding Extrasolar Planets. I Direct Searches Direct searches are difficult

Walter, Frederick M.

398

The HARPS search for southern extra-solar planets. XXXIV. A planetary system around the nearby M dwarf GJ163, with a super-Earth possibly in the habitable zone  

E-print Network

The meter-per-second precision achieved by today velocimeters enables the search for 1-10 M_Earth planets in the habitable zone of cool stars. This paper reports on the detection of 3 planets orbiting GJ163 (HIP19394), a M3 dwarf monitored by our ESO/HARPS search for planets. We made use of the HARPS spectrograph to collect 150 radial velocities of GJ163 over a period of 8 years. We searched the RV time series for coherent signals and found 5 distinct periodic variabilities. We investigated the stellar activity and casted doubts on the planetary interpretation for 2 signals. Before more data can be acquired we concluded that at least 3 planets are orbiting GJ163. They have orbital periods of P_b=8.632+-0.002, P_c=25.63+-0.03 and P_d=604+-8 days and minimum masses msini = 10.6+-0.6, 6.8+-0.9, and 29+-3 M_Earth, respectively. We hold our interpretations for the 2 additional signals with periods P_(e)=19.4 and P_(f)=108 days. The inner pair presents an orbital period ratio of 2.97, but a dynamical analysis of th...

Bonfils, X; Correia, A C M; Laskar, J; Udry, S; Delfosse, X; Forveille, T; Astudillo-Defru, N; Benz, W; Bouchy, F; Gillon, M; Hébrard, G; Lovis, C; Mayor, M; Moutou, C; Naef, D; Neves, V; Pepe, F; Perrier, C; Queloz, D; Santos, N C; Ségransan, D

2013-01-01

399

Venus as a laboratory for studying planetary surface, interior, and atmospheric evolution  

NASA Astrophysics Data System (ADS)

As Earth's twin, Venus offers a laboratory for understanding what makes our home planet unique in our solar system. The Decadal Survey points to the role of Venus in answering questions such as the supply of water and its role in atmospheric evolution, its availability to support life, and the role of geology and dynamics in controlling volatiles and climate. On Earth, the mechanism of plate tectonics drives the deformation and volcanism that allows volatiles to escape from the interior to the atmosphere and be recycled into the interior. Magellan revealed that Venus lacks plate tectonics. The number and distribution of impact craters lead to the idea Venus resurfaced very rapidly, and inspired numerous models of lithospheric foundering and episodic plate tectonics. However we have no evidence that Venus ever experienced a plate tectonic regime. How is surface deformation affected if no volatiles are recycled into the interior? Although Venus is considered a ';stagnant' lid planet (lacking plate motion) today, we have evidence for recent volcanism. The VIRTIS instrument on Venus Express mapped the southern hemisphere at 1.02 microns, revealing areas likely to be unweathered, recent volcanic flows. Additionally, numerous studies have shown that the crater population is consistent with ongoing, regional resurfacing. How does deformation and volcanism occur in the absence of plates? At what rate is the planet resurfacing and thus outgassing? Does lithospheric recycling occur with plate tectonics? In the 25 years since Magellan, the design of Synthetic Aperture Radar has advanced tremendously, allowing order of magnitude improvements in altimetry and imaging. With these advanced tools, we can explore Venus' past and current tectonic states. Tesserae are highly deformed plateaus, thought to be possible remnants of Venus' earlier tectonic state. How did they form? Are they low in silica, like Earth's continents, indicating the presence of abundant water? Does the plains volcanism cover an earlier tectonic surface, or perhaps cover ancient impact basins? Was there an abrupt transition in tectonic style, perhaps due to degassing of the crust or a more gradual shift? What is the nature of Venus' modern tectonics? Is the lithosphere still deforming? Is there recent or active volcanism? Is volcanism confined to hotspots, areas above mantle plumes? Has plains volcanism ceased? What are the implications for volatile history? These questions can be addressed via a combination of high resolution altimetry, imaging, and surface emissivity mapping.

Smrekar, S. E.; Hensley, S.; Helbert, J.

2013-12-01

400

Impact induced dehydration of serpentine and the evolution of planetary atmospheres  

SciTech Connect

Shock recovery experiments in the 25 to 45 GPa range on antigorite serpentine determine the amount of shock-induced loss of structural water as a function of shock pressure. Infrared absorption spectra of shock recovered samples demonstrate systematic changes in the amount of structural water and molecular, surface adsorbed water. These yield qualitative estimates of shock-induced water loss and demonstrate that a portion of the shock release structural water is readsorbed on interfacial grain surfaces. Determination of the post-shock water content of the shocked samples relates shock-induced water loss and shock pressure. Based on the present results and theoretical predictions, we conclude that shock pressures of from 20 to approx.60 GPa induce incipient to complete water loss, respectively. This result agrees closely with theoretical estimates for total dehydration. The dehydration interval and the activation energies for dehydration in shocked samples decrease systematically with increasing shock pressure as experienced by the sample. We believe the present experiments are applicable to describing dehydration processes of serpentine-like minerals in the accretional environment of the terrestrial planets. We conclude that complete loss of structural water in serpentine could have occurred from accretional impacts of approx.3 km/sec when earth and Venus have grown to about 50% of their final size. Accreting planetesimals, impacting Mars, never reached velocities sufficient for complete dehydration of serpentine. Our results support a model in which an impact generated atmosphere/hydrosphere forms while the earth is accreting.

Lange, M.A.; Ahrens, T.J.

1982-11-15

401

A miniature sensor for electrical field measurements in dusty planetary atmospheres  

NASA Astrophysics Data System (ADS)

Dusty phenomena such as regular wind-blown dust, dust storms, and dust devils are the most important, currently active, geological processes on Mars. Electric fields larger than 100 kV/m have been measured in terrestrial dusty phenomena. Theoretical calculations predict that, close to the surface, the bulk electric fields in martian dusty phenomena reach the breakdown value of the isolating properties of thin martian air of about a few 10 kV/m. The fact that martian dusty phenomena are electrically active has important implications for dust lifting and atmospheric chemistry. Electric field sensors are usually grounded and distort the electric fields in their vicinity. Grounded sensors also produce large errors when subject to ion currents or impacts from clouds of charged particles. Moreover, they are incapable of providing information about the direction of the electric field, an important quantity. Finally, typical sensors with more than 10 cm of diameter are not capable of measuring electric fields at distances as small as a few cm from the surface. Measurements this close to the surface are necessary for studies of the effects of electric fields on dust lifting. To overcome these shortcomings, we developed the miniature electric-field sensor described in this article.

Renno, N. O.; Kok, J. F.; Kirkham, H.; Rogacki, S.

2008-12-01

402

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

403

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

NASA Technical Reports Server (NTRS)

In the first half of this grant year, laboratory measurements were conducted on the millimeter-wave properties of atmospheric gases under simulated conditions for the outer planet. Significant improvements in the current system have made it possible to accurately characterize the opacity from gaseous NH3 at longer millimeter wavelengths (7 to 10 mm) under simulated Jovian conditions. In the second half of the grant year, it is hoped to extend such measurements to even shorter millimeter-wavelengths. Further analysis and application of the laboratory results to microwave and millimeter-wave absorption data for the outer planets, such as results from Voyager Radio Occultation experiments and earth-based radio astronomical observations will be continued. The analysis of available multispectral microwave opacity data from Venus, including data from the most recent radio astronomical ovservations in the 1.3 to 3.6 cm wavelength range and newly obtained Pioneer-Venus Radio Occulatation measurements at 13 cm, using the laboratory measurements as an interpretative tool will be pursued.

Steffes, Paul G.

1988-01-01

404

Microfabricated silicon leak for sampling planetary atmospheres with a mass spectrometer  

SciTech Connect

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 deg. 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 cal