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1

Modelling extrasolar planetary atmospheres  

NASA Astrophysics Data System (ADS)

The atmospheres of close-in Extrasolar Giant Planets (EGPs) experience important stellar radiation, raising the question of the heat redistribution around the planetary surface and of the importance of photochemistry effects for their spectral properties. They experience mass loss via quasi-thermal escape of their lightest elements. They rotate and experience tidal effects. Model atmospheres struggle to include even part of this complexity. Some address the dynamics of the atmospheres as a whole (3D) as subjected to rotation, or as patches of the surface (wind studies), compromising on the details of the composition and radiative/convective properties. Others solve the composition and radiative/convective properties, compromising on dynamical effects such as rotation. In this paper, we review existing model atmospheres for EGPs, and present the first high spatial resolution local (as opposed to global) 2/3D radiation hydrodynamic simulations of EGP atmospheres including dust cloud formation.

Allard, France

2010-11-01

2

ATMOSPHERIC LENSING AND OBLATENESS EFFECTS DURING AN EXTRASOLAR PLANETARY TRANSIT  

E-print Network

ATMOSPHERIC LENSING AND OBLATENESS EFFECTS DURING AN EXTRASOLAR PLANETARY TRANSIT Lam Hui1-precision photometric measurements of transiting extrasolar planets promise to tell us much about the characteristics of these systems. We examine how atmospheric lensing and (projected) planet oblateness/ellipticity modify transit

Seager, Sara

3

On the condensating species in terrestrial extrasolar planetary atmospheres  

NASA Astrophysics Data System (ADS)

ABSTRACT The formation of liquid droplets and/or solid particles has a significant impact on the thermal, dynamic, and chemical structure of the planetary environments, in which they are formed. For example, the character and distribution of the atmospheric condensates determine the appearance of such objects. It is therefore important to know, which chemical species might condense under the atmospheric conditions of extrasolar planets and how the condensate, solid or maybe liquid, nucleate in detail to finally form cloudy structures in such planetary atmospheres. In this contribution the presence of particles of likely condensates under atmospheric conditions of extrasolar terrestrial planets is discussed. Consequences regarding the condensation of major gaseous constituents of the planetary atmospheres are considered in particular. Selected applications, especially in view of the recently discovered low mass planets - so called Super-Earths -, are presented and compared. Acknowledgement: This work has been partly supported by the Forschungsallianz Planetary Evolution and Life of the Helmholtz Gemeinschaft (HGF).

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

2008-09-01

4

Mineral clouds and ionisation processes in extrasolar, planetary atmospheres  

NASA Astrophysics Data System (ADS)

The steady increase of the know extrasolar planets broadens our knowledge and at the same time, reveals our lack of understanding. The habitability of a planet depends, amongst other things, on the exposure of the planetary surface to radiation, how clouds form and which effect clouds have on the composition and on the electric state of the gas from which they form. We have studied the formation of mineral clouds (Fig. 1) on planetary atmospheres using a kinetic approach which allows us to predict the size distribution and material composition of the cloud particles. Using theses results we have investigated whether such clouds can be charged and under which conditions an electric field breakdown of the ambient gas, such as lightning or other transient luminous events, may occur. Our results suggest that different intra-cloud discharge processes dominate at different heights inside a cloud. We discuss the efficiency of electric field breakdowns and the electron enrichment (Fig. 2) to be expected in extrasolar atmospheres.

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

2013-09-01

5

Transonic Hydrodynamic Escape of Hydrogen from Extrasolar Planetary Atmospheres  

Microsoft Academic Search

Hydrodynamic escape is an important process in the formation and evolution of planetary atmospheres. Tran- sonic steady state solutions of the time-independent hydrodynamic equations are difficult to find because of the existence of a singularity point. A numerical model is developed to study the hydrodynamic escape of neutral gas from planetary atmospheres by solving the time-dependent hydrodynamic equations. The model

Feng Tian; Owen B. Toon; Alexander A. Pavlov; H. De Sterck

2005-01-01

6

TRANSONIC HYDRODYNAMIC ESCAPE OF HYDROGEN FROM EXTRASOLAR PLANETARY ATMOSPHERES  

E-print Network

point (where the gas flow velocity equals the sound speed) exists in the transonic time the hydrodynamic escape of neutral gas from planetary atmospheres by solving the time-dependent hydrodynamic. The model uses a two-dimensional energy depo- sition calculation instead of the single-layer heating

De Sterck, Hans

7

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

8

Atmospheres of Extrasolar Giant Planets  

E-print Network

The key to understanding an extrasolar giant planet's spectrum--and hence its detectability and evolution--lies with its atmosphere. Now that direct observations of thermal emission from extrasolar giant planets are in hand, atmosphere models can be used to constrain atmospheric composition, thermal structure, and ultimately the formation and evolution of detected planets. We review the important physical processes that influence the atmospheric structure and evolution of extrasolar giant planets and consider what has already been learned from the first generation of observations and modeling. We pay particular attention to the roles of cloud structure, metallicity, and atmospheric chemistry in affecting detectable properties through Spitzer Space Telescope observations of the transiting giant planets. Our review stresses the uncertainties that ultimately limit our ability to interpret EGP observations. Finally we will conclude with a look to the future as characterization of multiple individual planets in a single stellar system leads to the study of comparative planetary architectures.

Mark S. Marley; Jonathan Fortney; Sara Seager; Travis Barman

2006-02-21

9

Atmospheres of Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

The key to understanding an extrasolar giant planet's spectrum - and hence its detectability and evolution - lies with its atmosphere. Now that direct observations of thermal emission from extrasolar giant planets (EGPs) are in hand, atmosphere models can be used to constrain atmospheric composition, thermal structure, and ultimately the formation and evolution of detected planets. We review the important physical processes that influence the atmospheric structure and evolution of EGPs and consider what has already been learned from the first generation of observations and modeling. We pay particular attention to the roles of cloud structure, metallicity, and atmospheric chemistry in affecting detectable properties through Spitzer Space Telescope observations of the transiting giant planets. Our review stresses the uncertainties that ultimately limit our ability to interpret EGP observations. Finally we will conclude with a look to the future as characterization of multiple individual planets in a single stellar system leads to the study of comparative planetary architectures.

Marley, M. S.; Fortney, J.; Seager, S.; Barman, T.

10

Extrasolar Planetary Systems  

Microsoft Academic Search

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

L. V. Ksanfomaliti

2000-01-01

11

Measurements of Extrasolar Planetary Transits  

NASA Astrophysics Data System (ADS)

A campaign to measure properties of extrasolar planets using the transit method was undertaken at the University of Dallas using a C-14 telescope and SBIG 2000XM CCD camera. We successfully recorded transits of TrES-1b, Wasp-3, and HatP1. The C-14 exposure and tracking data (on WASP-3) indicate that we can probably effectively monitor stars to 13.5 or 14 magnitude with the C-14. We present the transit data, modeling, and determined planetary characteristics. The equipment used in this research was comparatively inexpensive and widely available and can be implemented at other small universities.

Meziere, Kyle; Wiseman, Nicolas; Rovny, Jared; Dinehart, Elise; Dufrain, Blaise; Bechter, Andrew; Bechter, Eric; Olenick, Richard; Sweeney, Arthur

2010-03-01

12

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

13

Dynamics of Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

Close to 600 exoplanets have now been detected around nearby, mostly solar-like stars, with many more candidates identified from just the first few months of data obtained with NASA's Kepler satellite. These discoveries have led to a many new questions concerning planet formation, structure and evolution, with many of our existing theoretical models now clearly in need of revision. They have also taken us one step closer to answering deeper questions such as the existence of extraterrestrial life in the Universe. The study of exoplanets has now become a top scientific priority both in the United States and around the world, and there is a sense of excitement in this field which is attracting many of the brightest young researchers in astrophysics. This project will address a number of key theoretical questions concerning the formation and dynamical evolution of planetary systems around other stars, including those in very different environments than our Sun, such as planets in binary stars and in dense stellar clusters. In particular, the dynamical stability and final fate of extrasolar planetary systems will be studied using computer simulations that combine the techniques of orbital dynamics and numerical hydrodynamics. The consequences of dynamical interactions between planets and their central stars (such as tidal interactions with "hot Jupiters") will also be studied using a combination of orbital dynamics, stellar evolution, and hydrodynamics calculations. All these questions are crucial to our theoretical interpretation of the rapidly expanding observational datasets on exoplanets. The main impact of this research will be to provide a new theoretical framework for interpreting data from current and future NASA missions such as Kepler, HST, Spitzer, JWST, and WFIRST.

Rasio, Frederic

14

Atmospheres of Extrasolar Giant Planets  

NASA Technical Reports Server (NTRS)

The next decade will almost certainly see the direct imaging of extrasolar giant planets around nearby stars. Unlike purely radial velocity detections, direct imaging will open the door to characterizing the atmosphere and interiors of extrasola planets and ultimately provide clues on their formation and evolution through time. This process has already begun for the transiting planets, placing new constraints on their atmospheric structure, composition, and evolution. Indeed the key to understanding giant planet detectability, interpreting spectra, and constraining effective temperature and hence evolution-is the atmosphere. I will review the universe of extrasolar giant planet models, focusing on what we have already learned from modeling and what we will likely be able to learn from the first generation of direct detection data. In addition to these theoretical considerations, I will review the observations and interpretation of the - transiting hot Jupiters. These objects provide a test of our ability to model exotic atmospheres and challenge our current understanding of giant planet evolution.

Marley, Mark

2006-01-01

15

Dynamical Habitability of Known Extrasolar Planetary Systems  

Microsoft Academic Search

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

Kristen Menou; Serge Tabachnik

2003-01-01

16

EXTRASOLAR PLANETARY SYSTEMS NEAR A SECULAR SEPARATRIX Rory Barnes1  

E-print Network

by comparing both analytical and numerical results. We find that the apsidal motion from secular theory doesEXTRASOLAR PLANETARY SYSTEMS NEAR A SECULAR SEPARATRIX Rory Barnes1 and Richard Greenberg1 Received 2005 June 19; accepted 2005 October 11 ABSTRACT Extrasolar planetary systems display a range

Barnes, Rory

17

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

18

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

19

The atmospheres and Evolution of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Observations of transiting extrasolar giant planet (EGP), HD 209458b, provided the first tests of atmospheric and evolutionary models for the shortest period EGPs. To date, most models fail to reproduce the observed radius of HD 209458b without including mechanisms, such as tidal heating or strong atmospheric circulations, in addition to irradiation by the parent star. Based solely on the observations of HD 209458b it is difficult to say with certainty how crucial these additional heating sources are to the evolution of close-in EGPs. Fortunately, new transiting EGP candidates are being discovered allowing for more robust tests of the theory over a broader parameter space. In this poster, new atmospheric and evolutionary models are presented for a variety of orbital separations, stellar spectral types, and planetary masses. Comparisons are made to the latest EGP transit observations.

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

2003-12-01

20

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

2011-09-02

21

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

22

Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results  

NASA Technical Reports Server (NTRS)

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

Lyon, Richard G.

2008-01-01

23

Planetary Science (mostly atmospheres)  

E-print Network

-based observing Surface-bounded exospheres like Mercury, Moon, Io and torus Mercury (left and above) Jupiter Mendillo and colleagues #12;Space-based observing Jupiter Saturn UV observations of aurora and coronas A random UV spectrometer Venus atmospheric D/H ratio Nulling interferometer for imaging extrasolar planets

Withers, Paul

24

Uses of Linear Polarization as a Probe of Extrasolar Planet Atmospheres  

E-print Network

We point out some advantages of making observations of extrasolar planets in linearly polarized (LP) light. Older cool stars have quite low levels (~ 10^-4 to 10^-5) of fractional LP, while extrasolar planets can have relatively high fractional LP (~0.1). Observations in LP light can therefore significantly enhance contrast between the planet and its parent star. Data on LP as a function of planetary orbital phase can be used to diagnose the properties (e.g., composition, size, and shape) of the scatterers in the planetary atmosphere. We discuss the feasibility of LP observations of extrasolar planets.

S. Saar; S. Seager

2003-05-22

25

Exploring Extrasolar Planetary Systems: New Observations of Extrasolar Planets Enabled by the James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

The search for extrasolar planets has been increasingly success over the last few years. In excess of 700 systems are now known, and Kepler has approx.2500 additional candidate systems, yet to be confirmed. Recently, progress has also been made in directly imaging extrasolar planets, both from the ground and in space. In this presentation will discuss the techniques employed to discover planetary systems, and highlight the capabilities, enabled by the James Webb Space Telescope (JWST). JWST is a large 6.5 meter aperture infrared telescope that is scheduled for launch in 2018, and will allow us to transition to characterizing the properties of these extrasolar planets and the planetary systems in which they reside.

Clampin, Mark

2012-01-01

26

Extrasolar Planetary Systems Tend to be near a Secular Separatrix  

Microsoft Academic Search

Extra-solar planetary systems display a range of behavior that can be understood in terms of the secular theory of classical celestial mechanics, including cases with libration about alignment of the major axes. Remarkably, >20% of the known systems with multiple planets (upsilon And, 47 Uma, and 55 Cnc) have trajectories in orbital element space that lie close to the separatrix

R. Greenberg; R. Barnes

2005-01-01

27

PREDICTING PLANETS IN KNOWN EXTRASOLAR PLANETARY SYSTEMS. II. TESTING FOR SATURN MASS PLANETS  

E-print Network

PREDICTING PLANETS IN KNOWN EXTRASOLAR PLANETARY SYSTEMS. II. TESTING FOR SATURN MASS PLANETS Sean known extrasolar planets, including 10 systems containing two or more planets. These planets are known we test for the presence of unseen massive planets in four known extrasolar planetary systems: HD

Barnes, Rory

28

Limits of photosynthesis in extrasolar planetary systems for earth-like planets.  

PubMed

We present a general modeling scheme for investigating the possibility of photosynthesis-based life on extrasolar planets. The scheme focuses on the identification of the habitable zone in main-sequence-star planetary systems with planets of Earth mass and size. Our definition of habitability is based on the long-term possibility of photosynthetic biomass production as a function of mean planetary surface temperature and atmospheric CO2-content. All the astrophysical, climatological, biogeochemical, and geodynamic key processes involved in the generation of photosynthesis-driven life conditions are taken into account. Implicitly, a co-genetic origin of the central star and the orbiting planet is assumed. The numerical solution of an advanced geodynamic model yields realistic look-up diagrams for determining the limits of photosynthesis in extrasolar planetary systems, assuming minimum CO2 levels set by the demand of C4 photosynthesis. PMID:11803974

Franck, S; von Bloh, W; Bounama, C; Steffen, M; Schonberner, D; Schellnhuber, H J

2001-01-01

29

Photochemistry in planetary atmospheres  

Microsoft Academic Search

Widely varying paths of evolutionary history, atmospheric processes, solar fluxes, and temperatures have produced vastly different planetary atmospheres. The similarities and differences between the earth atmosphere and those of the terrestrial planets (Venus and Mars) and of the Jovian planets are discussed in detail; consideration is also given to the photochemistry of Saturn, Uranus, Pluto, Neptune, Titan, and Triton. Changes

J. S. Levine; T. E. Graedel

1981-01-01

30

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.

31

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

32

A stability catalogue of the habitable zones in extrasolar planetary systems  

Microsoft Academic Search

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

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

2007-01-01

33

A stability catalogue of the habitable zones in extrasolar planetary systems  

Microsoft Academic Search

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

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

2007-01-01

34

IONIZATION OF EXTRASOLAR GIANT PLANET ATMOSPHERES  

SciTech Connect

Many extrasolar planets orbit close in and are subject to intense ionizing radiation from their host stars. Therefore, we expect them to have strong, and extended, ionospheres. Ionospheres are important because they modulate escape in the upper atmosphere and can modify circulation, as well as leave their signatures, in the lower atmosphere. In this paper, we evaluate the vertical location Z{sub I} and extent D{sub I} of the EUV ionization peak layer. We find that Z{sub I{approx}}1-10 nbar-for a wide range of orbital distances (a = 0.047-1 AU) from the host star-and D{sub I}/H{sub p{approx}}>15, where H{sub p} is the pressure scale height. At Z{sub I}, the plasma frequency is {approx}80-450 MHz, depending on a. We also study global ion transport, and its dependence on a, using a three-dimensional thermosphere-ionosphere model. On tidally synchronized planets with weak intrinsic magnetic fields, our model shows only a small, but discernible, difference in electron density from the dayside to the nightside ({approx}9 x 10{sup 13} m{sup -3} to {approx}2 x 10{sup 12} m{sup -3}, respectively) at Z{sub I}. On asynchronous planets, the distribution is essentially uniform. These results have consequences for hydrodynamic modeling of the atmospheres of close-in extrasolar giant planets.

Koskinen, Tommi T. [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ (United States); Cho, James Y-K. [Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom); Achilleos, Nicholas; Aylward, Alan D., E-mail: tommi@lpl.arizona.ed [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2010-10-10

35

Dynamics of planetary atmospheres  

E-print Network

Dynamics of planetary atmospheres Gas Giant Planets (Jupiter, Saturn, Uranus, Neptune) #12;Gas giant planets Jupiter Uranus Saturn Neptune #12;Giant planets: facts & figures 560 20 500 59? 2.7? 29.6 1660 16.05 3.9 17.2 164.8 30.1 Neptune 560 25 400 59 1.0 97.9 1190 17.24 4.1 14.5 84.0 19.2 Uranus

Read, Peter L.

36

Theoretical Spectra and Atmospheres of Extrasolar Giant Planets  

Microsoft Academic Search

We present a comprehensive theory of the spectra and atmospheres of irradiated extrasolar giant planets. We explore the dependences on stellar type, orbital distance, cloud characteristics, planet mass, and surface gravity. Phase-averaged spectra for specific known extrasolar giant planets that span a wide range of the relevant parameters are calculated, plotted, and discussed. The connection between atmospheric composition and emergent

David Sudarsky; Adam Burrows; Ivan Hubeny

2003-01-01

37

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

38

Extra-solar Oort cloud encounters and planetary impact rates  

SciTech Connect

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

Stern, A.

1987-01-01

39

Remote sensing of planetary properties and biosignatures on extrasolar terrestrial planets.  

PubMed

The major goals of NASA's Terrestrial Planet Finder (TPF) and the European Space Agency's Darwin missions are to detect terrestrial-sized extrasolar planets directly and to seek spectroscopic evidence of habitable conditions and life. Here we recommend wavelength ranges and spectral features for these missions. We assess known spectroscopic molecular band features of Earth, Venus, and Mars in the context of putative extrasolar analogs. The preferred wavelength ranges are 7-25 microns in the mid-IR and 0.5 to approximately 1.1 microns in the visible to near-IR. Detection of O2 or its photolytic product O3 merits highest priority. Liquid H2O is not a bioindicator, but it is considered essential to life. Substantial CO2 indicates an atmosphere and oxidation state typical of a terrestrial planet. Abundant CH4 might require a biological source, yet abundant CH4 also can arise from a crust and upper mantle more reduced than that of Earth. The range of characteristics of extrasolar rocky planets might far exceed that of the Solar System. Planetary size and mass are very important indicators of habitability and can be estimated in the mid-IR and potentially also in the visible to near-IR. Additional spectroscopic features merit study, for example, features created by other biosignature compounds in the atmosphere or on the surface and features due to Rayleigh scattering. In summary, we find that both the mid-IR and the visible to near-IR wavelength ranges offer valuable information regarding biosignatures and planetary properties; therefore both merit serious scientific consideration for TPF and Darwin. PMID:12469366

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

2002-01-01

40

Remote sensing of planetary properties and biosignatures on extrasolar terrestrial planets  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

41

Detectability of planetary rings around an extrasolar planet from reflected-light photometry  

E-print Network

The next generation of high-contrast imaging instruments will provide the first unresolved image of an extrasolar planet. While the emitted infrared light from the planet in thermal equilibrium should show almost no phase effect, the reflected visible light will vary with the orbital phase angle. We study the photometric variation of the reflected light with orbital phase of a ringed extrasolar planet. We show that a ring around an extrasolar planet, both obviously unresolved, can be detected by its specific photometric signature. Keywords: Stars: planetary systems -- Planets: rings -- Extrasolar planet characterization

L. Arnold; J. Schneider

2005-10-19

42

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

E-print Network

on the identification of the "habitable zone" in main-sequence star planetary systems accommodating Earth1 Determination of Habitable Zones in Extrasolar Planetary Systems: Where are Gaia's Sisters-like components. Our definition of habitability is based on the long-term possibility of photosynthetic biomass

43

About putative Neptune-like extrasolar planetary candidates  

E-print Network

We re-analyze the precision radial velocity (RV) data of HD188015, HD114729, HD190360, HD147513 and HD208487. All these stars are supposed to host Jovian companions in long-period orbits. We test a hypothesis that the residuals of the 1-planet model of the RV or an irregular scatter of the measurements about the synthetic RV curve may be explained by the existence of additional planets in short-period orbits. We perform a global search for the best fits in the orbital parameters space with genetic algorithms and simplex method. This makes it possible to verify and extend the results obtained with an application of commonly used FFT-based periodogram analysis for identifying the leading periods. Our analysis confirms the presence of a periodic component in the RV data of HD190360 which may correspond to a hot-Neptune planet. We found four new cases when the 2-planet model yields significantly better fits to the RV data than the best 1-planet solutions. If the periodic variability of the residuals of single-planet fits has indeed a planetary origin then hot-Neptune planets may exist in these extrasolar systems. We estimate their orbital periods in the range of 7-20d and minimal masses about of 20 masses od the Earth.

Krzysztof Gozdziewski; Cezary Migaszewski

2005-11-10

44

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

2009-02-19

45

Terrestrial Planet Formation in Extra-Solar Planetary Systems  

E-print Network

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

Sean N. Raymond

2008-01-16

46

Water vapour in the atmosphere of a transiting extrasolar planet  

Microsoft Academic Search

Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets (`hot Jupiters'). Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution. Here

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

2007-01-01

47

Phase-Dependent Properties of Extrasolar Planet Atmospheres  

Microsoft Academic Search

Recently the Spitzer Space Telescope observed the transiting extrasolar\\u000aplanets, TrES-1 and HD209458b. These observations have provided the first\\u000aestimates of the day side thermal flux from two extrasolar planets orbiting\\u000aSun-like stars. In this paper, synthetic spectra from atmospheric models are\\u000acompared to these observations. The day-night temperature difference is\\u000aexplored and phase-dependent flux densities are predicted for both

Travis S. Barman; Peter H. Hauschildt; France Allard

2005-01-01

48

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

49

Extrasolar Planetary Dynamics with a Generalized Planar Laplace-Lagrange Secular Theory  

Microsoft Academic Search

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

Dimitri Veras; Philip J. Armitage

2007-01-01

50

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

E-print Network

Stability of Earth-Mass Planets in the Habitable Zones of Extrasolar Planetary Systems Dr. Ravi Kumar Kopparapu Dept. of Geosciences, College of Earth and Mineral Science Over 500 planets orbiting and Saturn but in the last couple of years several "super-earths", planets with mass less than 10 times Earth

Bjørnstad, Ottar Nordal

51

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

E-print Network

PREDICTING 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 planets formed and migrated quickly, terrestrial planets may form from a second generation

Barnes, Rory

52

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

Microsoft Academic Search

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

B. W. Jones; P. N. Sleep

2003-01-01

53

Determination of habitable zones in extrasolar planetary systems: Where are Gaia's sisters?  

Microsoft Academic Search

A general modeling scheme for assessing the suitability for life of extrasolar planets is presented. The scheme focuses on the identification of the ``habitable zone'' in main sequence star planetary systems accommodating Earth-like components. Our definition of habitability is based on the long-term possibility of photosynthetic biomass production under geodynamic conditions. Therefore all the pertinent astrophysical, climatological, biogeochemical, and geodynamic

Siegfried Franck; Werner von Bloh; Christine Bounama; Matthias Steffen; Detlef Schönberner; Hans-Joachim Schellnhuber

2000-01-01

54

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

55

Theoretical spectra and atmospheres of extrasolar giant planets  

Microsoft Academic Search

This work is a detailed study of extrasolar giant planet (EGP) atmospheres and spectra. Models representative of the full range of systems known today are included, from the extreme close-in EGPs to Jovian-like planets at large orbital radii. Using a self-consistent planar atmosphere code along with the latest atomic and molecular cross sections, cloud models, Mie theory treatment of grain

David L. Sudarsky

2002-01-01

56

Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres  

Microsoft Academic Search

Atmospheres of transiting extrasolar giant planets (EGPs) such as HD 209458 b\\u000amust impose features on the spectra of their parent stars during transits;\\u000athese features contain information about the physical conditions and chemical\\u000acomposition of the atmospheres. The most convenient observational index showing\\u000athese features is the ``spectrum ratio'', defined as the wavelength-dependent\\u000aratio of spectra taken in and

Timothy M. Brown

2001-01-01

57

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

58

Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres  

NASA Astrophysics Data System (ADS)

Atmospheres of transiting extrasolar giant planets (EGPs) such as HD 209458b must impose features on the spectra of their parent stars during transits; these features contain information about the physical conditions and chemical composition of the atmospheres. The most convenient observational index showing these features is the ``spectrum ratio'' ?(?), defined as the wavelength-dependent ratio of spectra taken in and out of transit. The principal source of structure in ? is the variation with wavelength of the height at which the EGP atmosphere first becomes opaque to tangential rays-one may think of the planet as having different radii, and hence different transit depths, at each wavelength. The characteristic depth of absorption lines in ? scales with the atmospheric scale height and with the logarithm of the opacity ratio between continuum and strong lines. For close-in EGPs, line depths of 10-3 relative to the stellar continuum can occur. The atmospheres of EGPs probably consist mostly of molecular species, including H2, CO, H2O, and CH4, while the illuminating flux is characteristic of a Sun-like star. Thus, the most useful diagnostics are likely to be the near-infrared bands of these molecules, and the visible/near-IR resonance lines of the alkali metals. I describe a model that estimates ?(?) for EGPs with prescribed radius, mass, temperature structure, chemical composition, and cloud properties. This model assumes hydrostatic and chemical equilibrium in an atmosphere with chemistry involving only H, C, N, and O. Other elements (He, Na, K, Si) are included as nonreacting minor constituents. Opacity sources include Rayleigh scattering, the strongest lines of Na and K, collision-induced absorption by H2, scattering by cloud particles, and molecular lines of CO, H2O, and CH4. The model simulates Doppler shifts from height-dependent winds and from planetary rotation, and deals in a schematic way with photoionization of Na and K by the stellar UV flux. Using this model, I investigated the diagnostic potential of various spectral features for planets similar to HD 209458b. Clouds are the most important determinants of the depth of features in ? they decrease the strength of all features as they reach higher in the atmosphere. The relative strengths of molecular lines provide diagnostics for the heavy-element abundance, temperature, and the vertical temperature structure, although diagnostics for different physical properties tend to be somewhat degenerate. Planetary rotation with likely periods leaves a clear signature on the line profiles, as do winds with speeds comparable to that of rotation. Successful use of these diagnostics will require spectral observations with signal-to-noise ratio (S/N) of 103 or better and resolving power R=?/?? ranging from 103 to 106, depending on the application. Because of these stringent demands, it will be important to evolve analysis methods that combine information from many lines into a few definitive diagnostic indices.

Brown, Timothy M.

2001-06-01

59

Theoretical Spectra and Atmospheres of Extrasolar Giant Planets  

E-print Network

We present a comprehensive theory of the spectra and atmospheres of irradiated extrasolar giant planets. We explore the dependences on stellar type, orbital distance, cloud characteristics, planet mass, and surface gravity. Phase-averaged spectra for specific known extrasolar giant planets that span a wide range of the relevant parameters are calculated, plotted, and discussed. The connection between atmospheric composition and emergent spectrum is explored in detail. Furthermore, we calculate the effect of stellar insolation on brown dwarfs. We review a variety of representative observational techniques and programs for their potential for direct detection, in light of our theoretical expectations, and we calculate planet-to-star flux ratios as a function of wavelength. Our results suggest which spectral features are most diagnostic of giant planet atmospheres and reveal the best bands in which to image planets of whatever physical or orbital characteristics.

David Sudarsky; Adam Burrows; Ivan Hubeny

2003-02-19

60

Spectroscopy of planetary atmospheres in our Galaxy  

NASA Astrophysics Data System (ADS)

About 20 years after the discovery of the first extrasolar planet, the number of planets known has grown by three orders of magnitude, and continues to increase at neck breaking pace. For most of these planets we have little information, except for the fact that they exist and possess an address in our Galaxy. For about one third of them, we know how much they weigh, their size and their orbital parameters. For less than 20, we start to have some clues about their atmospheric temperature and composition. How do we make progress from here? We are still far from the completion of a hypothetical Hertzsprung-Russell diagram for planets comparable to what we have for stars, and today we do not even know whether such classification will ever be possible or even meaningful for planetary objects. But one thing is clear: planetary parameters such as mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as happened for the planets in our Solar System. As in situ measurements are and will remain off-limits for exoplanets, to study their chemical composition we will have to rely on remote sensing spectroscopic observations of their gaseous envelopes. In this paper, we critically review the key achievements accomplished in the study of exoplanet atmospheres in the past ten years. We discuss possible hurdles and the way to overcome those. Finally, we review the prospects for the future. The knowledge and the experience gained with the planets in our solar system will guide our journey among those faraway worlds.

Tinetti, Giovanna; Encrenaz, Thérèse; Coustenis, Athena

2013-10-01

61

Retrieval of atmospheric properties of extrasolar planets  

E-print Network

We present a new method to retrieve molecular abundances and temperature profiles from exoplanet atmosphere photometry and spectroscopy. Our method allows us to run millions of 1-D atmosphere models in order to cover the ...

Nikku, Madhusudhan, 1980-

2009-01-01

62

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

63

DETECTION OF AN EXTRASOLAR PLANET ATMOSPHERE1  

Microsoft Academic Search

We report high-precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm. We find that the photometric dimming during transit in a bandpass centered on the sodium feature is deeper by (2.32 ? 0.57) ? 10? 4 relative to simultaneous obser- vations of the transit in adjacent bands. We

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

64

An extrasolar planetary system with three Neptune-mass planets  

Microsoft Academic Search

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 2-15days. Here we report a system of three Neptune-mass planets with periods of 8.67,

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

2006-01-01

65

Radial Velocity Detection of Extra-Solar Planetary Systems  

NASA Technical Reports Server (NTRS)

The McDonald Observatory Planetary Search (MOPS) was designed to search for Jovian-mass planets in orbit around solar-type stars by making high-precision measurements of the Radial Velocity (RV) of a star, to attempt to detect the reflex orbital motion of the star around the star-planet barycenter. In our solar system, the velocity of the Sun around the Sun-Jupiter barycenter averages 12.3 m/ s. The MOPS survey started operation in September 1987, and searches 36 bright, nearby, solar-type dwarfs to 10 m/s precision. The survey was started using telluric O2 absorption lines as the velocity reference metric. Observations use the McDonald Observatory 2.7-m Harlan Smith Telescope coude spectrograph with the six-foot camera. This spectrograph configuration isolates a single order of the echelle grating on a Texas Instruments 800 x 800 CCD. The telluric line method gave us a routine radial velocity precision of about 15 m/s for stars down to about 5-th magnitude. However, the data obtained with this technique suffered from some source of long-term systematic errors, which was probably the intrinsic velocity variability of the terrestrial atmosphere, i.e. winds. In order to eliminate this systematic error and to improve our overall measurement precision, we installed a stabilized I2 gas absorption cell as the velocity metric for the MOPS in October 1990. In use at the telescope, the cell is placed directly in front of the spectrograph entrance slit, with starlight passing through the cell. The use of this sealed stabilized I2 cell removes potential problems with possible long-term drifts in the velocity metric. The survey now includes a sample of 36 nearby F, G, and K type stars of luminosity class V or IV-V.

Cochran, William D.

1998-01-01

66

The Period-Ratio and Mass-Ratio Correlation in Extra-Solar Multiple Planetary Systems  

E-print Network

Employing the data from orbital periods and masses of extra-solar planets in 166 multiple planetary systems, the period-ratio and mass-ratio of adjacent planet pairs are studied. The correlation between the period-ratio and mass-ratio is confirmed and found to have a correlation coefficient of 0.5303 with a 99% confidence interval (0.3807, 0.6528). A comparison with the distribution of synthetic samples from a Monte Carlo simulation reveals the imprint of planet-planet interactions on the formation of adjacent planet pairs in multiple planetary systems.

Jiang, Ing-Guey; Hung, Wen-Liang

2015-01-01

67

The period-ratio and mass-ratio correlation in extra-solar multiple planetary systems  

NASA Astrophysics Data System (ADS)

Employing the data from orbital periods and masses of extra-solar planets in 166 multiple planetary systems, the period ratio and mass ratio of adjacent planet pairs are studied. The correlation between the period ratio and mass ratio is confirmed, with a correlation coefficient of 0.5303 with a 99 per cent confidence interval (0.3807, 0.6528). A comparison with the distribution of synthetic samples from a Monte Carlo simulation reveals the imprint of planet-planet interactions on the formation of adjacent planet pairs in multiple planetary systems.

Jiang, Ing-Guey; Yeh, Li-Chin; Hung, Wen-Liang

2015-04-01

68

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

PubMed

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

Helling, Christiane; Fomins, Aleksejs

2013-07-13

69

The Significance of the Sodium Detection in the Extrasolar Planet HD209458b Atmosphere  

E-print Network

The Hubble Space Telescope (HST) detection of an extrasolar planet atmosphere in 2001 was a landmark step forward for the characterization of extrasolar planets. HST detected the trace element sodium, via the neutral atomic resonance doublet at 593 nm, in the transiting extrasolar giant planet HD209458b. In this paper I discuss the significance of this first ever extrasolar planet atmosphere detection. I explain how the sodium measurement can be used as a constraint on HD209458b atmosphere models and review recent interpretations of the lower-than-expected sodium line strength.

S. Seager

2003-05-19

70

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

71

Extrasolar planets Lecture 2: Planetary formation theory and  

E-print Network

and would be hidden by it. 6 ASTR178 - other worlds: planets and planetary systems #12;Disks around from condensed material in the protoplanetary disc around a star ·In an inner hotter zone only grains of icy snowballs in a cooler zone outside the so-called "ice boundary" ·Planets forming there are likely

Parker, Quentin A.

72

Physics of planetary atmospheres and ionospheres  

NASA Technical Reports Server (NTRS)

The traditional atmospheric regions, the distinction between homosphere and heterosphere, and changing atmospheric composition are discussed. The validity of the barometric law based on a Maxwell-Boltzmann distribution, for the major part of a planetary atmosphere and its breakdown in the exosphere due to escape of atmospheric particles is considered. The formation and maintenance of photochemical and diffusion-controlled ionospheric layers are treated. Their applicability to planetary ionospheres is dealt with. The spatial extent of magnetic and nonmagnetic planet ionospheres is investigated. Thermal and nonthermal processes responsible for the mass loss of planetary atmospheres are surveyed.

Bauer, S. J.

1981-01-01

73

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

74

New Chemical Models for Extrasolar Giant Planet Atmospheres, and Implications for Observations  

NASA Astrophysics Data System (ADS)

We have developed one-dimensional photochemical and thermochemical kinetics and diffusion models to study the effects of disequilibrium processes such as photochemistry and transport-induced quenching in extrasolar giant planet (EGP) atmospheres. These models transition smoothly between each chemical regime (thermochemical, transport-quench, and photochemical) and allow us to explore the effects of photochemistry and/or atmospheric transport on the vertical abundance profiles of individual atmospheric constituents. Here we will present model results for neutral H-C-N-O chemistry in the atmospheres of GJ 436b, HD 189733b, HD 209458b, and WASP-12b. We will examine the sensitivity of the model results to thermal and eddy diffusion profiles, and identify the major chemical processes affecting the abundance of potentially observable carbon, nitrogen, and oxygen species. Particular attention will be given to transport-induced quenching mechanisms, including updates to a timescale approach that can be used to estimate the abundance of quenched species in EGP atmospheres. A comparison of model results with primary transit and secondary eclipse observations will be used to discuss implications for the observational properties of EGPs. In general, our results indicate that disequilibrium processes such as photochemistry and transport-induced quenching play a larger role on cooler exoplanets than on warmer exoplanets. Disequilibrium processes are also likely to enhance the abundances of various atmospheric constituents (e.g., CH4, HCN, NH3, and C2H2) that are expected to affect the spectral and photometric behavior of extrasolar giant planets. This work is supported by the NASA Planetary Atmospheres Program.

Visscher, Channon W.; Moses, J. I.

2011-09-01

75

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

76

Planetary Formation: From The Earth And Moon To Extrasolar Planets  

NASA Technical Reports Server (NTRS)

An overview of current theories of planetary growth, emphasizing the formation of habitable planets, is presented. These models are based upon observations of the Solar System and of young stars and their environments. They predict that rocky planets should form around most single stars, although it is possible that in some cases such planets are lost - to orbital decay within the protoplanetary disk. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth like terrestrial planets, but if they become massive enough before the protoplanetary disk dissipates, then they are able to accumulate substantial amounts of gas. Specific issues to be discussed include: (1) how do giant planets influence the formation and habitability of terrestrial planets? (2) could a giant impact leading to lunar formation have occurred - 100 million years after the condensation of the oldest meteorites?

Lissauer, Jack J.; DeVincenzi, Donald (Technical Monitor)

1999-01-01

77

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

78

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

79

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

80

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

81

Theoretical spectra and atmospheres of extrasolar giant planets  

NASA Astrophysics Data System (ADS)

This work is a detailed study of extrasolar giant planet (EGP) atmospheres and spectra. Models representative of the full range of systems known today are included, from the extreme close-in EGPs to Jovian-like planets at large orbital radii. Using a self-consistent planar atmosphere code along with the latest atomic and molecular cross sections, cloud models, Mie theory treatment of grain scattering and absorption, and incident stellar fluxes, I produce an extensive set of theoretical EGP atmosphere models and emergent spectra. The emergent spectra of EGPs strongly depend upon their outer atmospheric chemical compositions, which in turn depend upon the run of temperature and pressure with atmospheric depth. Because of qualitative similarities in the compositions and spectra of objects within several broad temperature ranges, EGPs fall naturally into five groups, or composition classes. Such a classification scheme, however preliminary, brings a degree of order to the rich variety of EGP systems known to exist today. Generic models that represent the EGP classes, as well as a set of specific models for a number of important systems that have been detected, are provided. Furthermore, the effects on emergent EGP spectra of varying key parameters such as surface gravity, cloud particle sizes, orbital distance, etc. are modeled. A discussion of current and future ground-based and space- based missions to detect and characterize EGPs in light of theoretical spectral models is included to facilitate an understanding of which systems are most likely to be studied successfully.

Sudarsky, David L.

82

Disequilibrium chemistry in the atmospheres of extrasolar giant planets as a function of stellar distance  

Microsoft Academic Search

The atmospheric composition and spectral properties of extrasolar giant planets will depend in large part on disequilibrium processes like photochemistry, chemical kinetics, diffusive transport, and haze formation. We have developed a photochemical kinetics, radiative transfer, and 1-D vertical transport model for extrasolar giant planets (EGPs) and brown dwarfs. The chemical reaction list contains H-, C-, O-, N-, P-, and S-bearing

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

2003-01-01

83

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

84

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets. III. Breakdown Conditions for Mineral Clouds  

NASA Astrophysics Data System (ADS)

Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter, and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn, and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in brown dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from our kinetic dust cloud formation model that is part of the DRIFT-PHOENIX model atmosphere simulations. We present a first investigation of the dependence of the breakdown conditions in brown dwarf and giant gas exoplanets on the local gas-phase chemistry, the effective temperature, and primordial gas-phase metallicity. Our results suggest that different intra-cloud discharge processes dominate at different heights inside mineral clouds: local coronal (point discharges) and small-scale sparks at the bottom region of the cloud where the gas density is high, and flow discharges and large-scale sparks near, and maybe above, the cloud top. The comparison of the thermal degree of ionization and the number density of cloud particles allows us to suggest the efficiency with which discharges will occur in planetary atmospheres.

Helling, Ch.; Jardine, M.; Stark, C.; Diver, D.

2013-04-01

85

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. III. BREAKDOWN CONDITIONS FOR MINERAL CLOUDS  

SciTech Connect

Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter, and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn, and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in brown dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from our kinetic dust cloud formation model that is part of the DRIFT-PHOENIX model atmosphere simulations. We present a first investigation of the dependence of the breakdown conditions in brown dwarf and giant gas exoplanets on the local gas-phase chemistry, the effective temperature, and primordial gas-phase metallicity. Our results suggest that different intra-cloud discharge processes dominate at different heights inside mineral clouds: local coronal (point discharges) and small-scale sparks at the bottom region of the cloud where the gas density is high, and flow discharges and large-scale sparks near, and maybe above, the cloud top. The comparison of the thermal degree of ionization and the number density of cloud particles allows us to suggest the efficiency with which discharges will occur in planetary atmospheres.

Helling, Ch.; Jardine, M.; Stark, C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Diver, D., E-mail: ch@leap2010.eu [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2013-04-20

86

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

87

ROCKY EXTRASOLAR PLANETARY COMPOSITIONS DERIVED FROM EXTERNALLY POLLUTED WHITE DWARFS  

SciTech Connect

We report Keck High Resolution Echelle Spectrometer data and model atmosphere analysis of two helium-dominated white dwarfs, PG1225-079 and HS2253+8023, whose heavy pollutions most likely derive from the accretion of terrestrial-type planet(esimal)s. For each system, the minimum accreted mass is {approx}10{sup 22} g, that of a large asteroid. In PG1225-079, Mg, Cr, Mn, Fe, and Ni have abundance ratios similar to bulk Earth values, while we measure four refractory elements, Ca, Sc, Ti, and V, all at a factor of {approx}2-3 higher abundance than in the bulk Earth. For HS2253+8023 the swallowed material was compositionally similar to bulk Earth in being more than 85% by mass in the major element species, O, Mg, Si, and Fe, and with abundances in the distinctive proportions of mineral oxides-compelling evidence for an origin in a rocky parent body. Including previous studies we now know of four heavily polluted white dwarfs where the measured oxygen and hydrogen are consistent with the view that the parents' bodies formed with little ice, interior to any snow line in their nebular environments. The growing handful of polluted white dwarf systems with comprehensive abundance measurements form a baseline for characterizing rocky exoplanet compositions that can be compared with bulk Earth.

Klein, B.; Jura, M.; Zuckerman, B. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562 (United States); Koester, D., E-mail: kleinb@astro.ucla.edu, E-mail: jura@astro.ucla.edu, E-mail: ben@astro.ucla.edu, E-mail: koester@astrophysik.uni-kiel.de [Institut fuer Theoretische Physik und Astrophysik, University of Kiel, D-24098 Kiel (Germany)

2011-11-01

88

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

89

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

90

Toward a Deterministic Model of Planetary Formation. I. A Desert in the Mass and Semimajor Axis Distributions of Extrasolar Planets  

Microsoft Academic Search

In an attempt to develop a deterministic theory for planet formation, we examine the accretion of cores of giant planets from planetesimals, gas accretion onto the cores, and their orbital migration. We adopt a working model for nascent protostellar disks with a wide variety of surface density distributions in order to explore the range of diversity among extrasolar planetary systems.

S. Ida; D. N. C. Lin

2004-01-01

91

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

92

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

93

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

94

Predicting Planets in Known Extra-Solar Planetary Systems III: Forming Terrestrial Planets  

E-print Network

Recent results have shown that many of the known extrasolar planetary systems contain regions which 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 well-determined. Assuming the giant planets formed and migrated quickly, then terrestrial planets may form from a second generation of planetesimals. In each case, Moon- to Mars-sized planetary embryos are placed in between the giant planets and evolved for 100 Myr. We find that planets form relatively easily in 55 Cnc, with masses up to 0.6 Earth masses and in some cases substantial water contents and orbits in the habitable zone. HD 38529 is likely to support an asteroid belt but no terrestrial planets of significant mass. No terrestrial planets form in HD 37124 and HD 74156, although in some cases 1-2 lone embryos survive for 100 Myr. If migration occurred later, depleting the planetesimal disk, then massive terrestrial planets are unlikely to form in any of these systems.

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

2006-05-15

95

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

96

Studies of planetary upper atmospheres through occultations  

NASA Technical Reports Server (NTRS)

The structure, composition, dynamics and energy balance of planetary upper atmospheres through interpretation of steller occultation data from Uranus is discussed. The wave-optical problem of modelling strong scintillation for arbitrary turbulent atmospheres is studied, as well as influence of turbulence. It was concluded that quasi-global features of atmospheric structure are accurately determined by numerical inversion. Horizontally inhomogeneous structures are filtered out and have little effect on temperature profiles.

Elliot, J. L.

1982-01-01

97

The presence of methane in the atmosphere of an extrasolar planet  

Microsoft Academic Search

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

Mark R. Swain; Gautam Vasisht; Giovanna Tinetti

2008-01-01

98

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

99

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

100

Climatic effects of cloud particles in the atmospheres of Earth-like extrasolar planets  

NASA Astrophysics Data System (ADS)

ABSTRACT Clouds can have an important effect on the climate (and thereby also on the habitability) of terrestrial planets. While clouds in the upper atmosphere increase atmospheric cooling by scattering of the incoming stellar radiation, clouds in the lower atmosphere are leading to an enhanced greenhouse effect, resulting in higher surface temperatures. Due to the shortage of observational detail regarding the atmospheres of terrestrial extrasolar planets, particular studies of clouds are limited to basic questions about the predominant processes at work, which have to be adressed. In this contribution we focus on the climatic effects of water droplet distributions in the lower tropospheres of Earth-like extrasolar planets. As a first approximation, parametrized distribution functions are used in our study for the description of the cloud particles. The distribution function used here is the log-normal distribution, which is known to be a good approximation to observed size spectra of cumulus clouds in the Earths atmosphere (cf. [3]). This size distribution function is given by the expression f(a) = N p 2? a ln ?g exp ? -(ln a - ln an)2 2(ln ?g)2 ? (1) and depends on the three parameters: particle number concentration N, geometric standard deviation ?g and the median radius an. The particle radius is denoted by a, respectively. Our simplified cloud description scheme is coupled with a one-dimensional radiative-convective climate-model (see e.g. [4] and [2] for a general overview of the model) in order to study the basic effects on the climate. Optical properties of the cloud particles are, thereby, calculated by Mie-theory (cf. e.g. [1]), assuming spherical particles composed of pure liquid water and have been included in the models radiative transfer scheme. Results for e.g. different types of central stars are presented and compared with the respective cloud-free situations. References [1] C.F. Bohren and D.R. Huffman, Absorption and scattering of light by small particles, 1983, Wiley [2] Grenfell et al. (2007) Planetary and Space Science, Vol. 55, Issue 5, 661-671 [3] A. A. Kokhanovsky, Cloud Optics, 2006, Springer [4] Segura et al. (2003) Astrobiology, Vol. 3, No. 4, 689- 708

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

2008-09-01

101

Convective storms in planetary atmospheres  

NASA Astrophysics Data System (ADS)

The atmospheres of the planets in the Solar System have different physical properties that in some cases can be considered as extreme when compared with our own planet's more familiar atmosphere. From the tenuous and cold atmosphere of Mars to the dense and warm atmosphere of Venus in the case of the terrestrial planets, to the gigantic atmospheres of the outer planets, or the nitrogen and methane atmosphere of Saturn's moon Titan, we can find a large variety of physical environments. The comparative study of these atmospheres provides a better understanding of the physics of a geophysical fluid. In many of these worlds convective storms of different intensity appear. They are analogous to terrestrial atmospheres fed by the release of latent heat when one of the gases in the atmosphere condenses and they are therefore called moist convective storms. In many of these planets they can produce severe meteorological phenomena and by studying them in a comparative way we can aspire to get a further insight in the dynamics of these atmospheres even beyond the scope of moist convection. A classical example is the structure of the complex systems of winds in the giant planets Jupiter and Saturn. These winds are zonal and alternate in latitude but their deep structure is not accessible to direct observation. However the behaviour of large--scale convective storms vertically extending over the "weather layer" allows to study the buried roots of these winds. Another interesting atmosphere with a rather different structure of convection is Titan, a world where methane is close to its triple point in the atmosphere and can condense in bright clouds with large precipitation fluxes that may model part of the orography of the surface making Titan a world with a methane cycle similar to the hydrological cycle of Earth's atmosphere.

Hueso, R.; Sánchez-Lavega, A.

2013-05-01

102

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

103

Chemical kinetics and modeling of planetary atmospheres  

NASA Technical Reports Server (NTRS)

A unified overview is presented for chemical kinetics and chemical modeling in planetary atmospheres. The recent major advances in the understanding of the chemistry of the terrestrial atmosphere make the study of planets more interesting and relevant. A deeper understanding suggests that the important chemical cycles have a universal character that connects the different planets and ultimately link together the origin and evolution of the solar system. The completeness (or incompleteness) of the data base for chemical kinetics in planetary atmospheres will always be judged by comparison with that for the terrestrial atmosphere. In the latter case, the chemistry of H, O, N, and Cl species is well understood. S chemistry is poorly understood. In the atmospheres of Jovian planets and Titan, the C-H chemistry of simple species (containing 2 or less C atoms) is fairly well understood. The chemistry of higher hydrocarbons and the C-N, P-N chemistry is much less understood. In the atmosphere of Venus, the dominant chemistry is that of chlorine and sulfur, and very little is known about C1-S coupled chemistry. A new frontier for chemical kinetics both in the Earth and planetary atmospheres is the study of heterogeneous reactions. The formation of the ozone hole on Earth, the ubiquitous photochemical haze on Venus and in the Jovian planets and Titan all testify to the importance of heterogeneous reactions. It remains a challenge to connect the gas phase chemistry to the production of aerosols.

Yung, Yuk L.

1990-01-01

104

Submillimeter Planetary Atmospheric Chemistry Exploration Sounder  

NASA Technical Reports Server (NTRS)

Planetary Atmospheric Chemistry Exploration Sounder (SPACES), a high-sensitivity laboratory breadboard for a spectrometer targeted at orbital planetary atmospheric analysis. The frequency range is 520 to 590 GHz, with a target noise temperature sensitivity of 2,500 K for detecting water, sulfur compounds, carbon compounds, and other atmospheric constituents. SPACES is a prototype for a powerful tool for the exploration of the chemistry and dynamics of any planetary atmosphere. It is fundamentally a single-pixel receiver for spectral signals emitted by the relevant constituents, intended to be fed by a fixed or movable telescope/antenna. Its front-end sensor translates the received signal down to the 100-MHz range where it can be digitized and the data transferred to a spectrum analyzer for processing, spectrum generation, and accumulation. The individual microwave and submillimeter wave components (mixers, LO high-powered amplifiers, and multipliers) of SPACES were developed in cooperation with other programs, although with this type of instrument in mind. Compared to previous planetary and Earth science instruments, its broad bandwidth (approx. =.13%) and rapid tunability (approx. =.10 ms) are new developments only made possible recently by the advancement in submillimeter circuit design and processing at JPL.

Schlecht, Erich T.; Allen, Mark A.; Gill, John J.; Choonsup, Lee; Lin, Robert H.; Sin, Seth; Mehdi, Imran; Siegel, Peter H.; Maestrini, Alain

2013-01-01

105

A planetary atmosphere simulator: application to Titan  

Microsoft Academic Search

A planetary environment simulation system developed in the framework of the activities connected with the preparation of the Cassini-Huygens mission is presented. In particular, the simulator was designed to recreate Titan's atmospheric conditions specifically to test the HASI instrument, part of the Huygens probe payload. A review of the actual knowledge on Titan's environment is reported. The experimental apparatus and

F. Ferri; A. Rotundi; F. A. Farrelly; M. Fulchignoni

1997-01-01

106

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

107

Faculty Positions Department of Earth, Atmospheric, and Planetary Sciences  

E-print Network

Faculty Positions Department of Earth, Atmospheric, and Planetary Sciences Purdue University In support of its significant existing strengths in climate and extreme weather, the Department of Earth, Atmospheric and Planetary Sciences (EAPS), within the College of Science, Purdue University, invites

Kihara, Daisuke

108

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

NASA Astrophysics Data System (ADS)

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

Spaulding, Dylan

2011-06-01

109

Atmospheric escape, redox evolution, and planetary habitability  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

110

A second substellar companion in the Gliese 86 system. A brown dwarf in an extrasolar planetary system  

NASA Astrophysics Data System (ADS)

We report observations using the ESO adaptive optics system ADONIS of the known extrasolar planetary system Gliese 86. This star has a known 4 MJup sin i planet in a 15.8 day orbit and exhibits an additional, large, long-period, radial velocity drift (\\cite{queloz00}). The coronographic images reveal a faint (J=14.7, H=14.4, K=13.7) object at a projected distance of r=1{.'' 72 +/- 0.'' 02 and PA=119+/- 1 o. Gliese 86 and the discovered object share the same proper motion, as confirmed by independent measurements at three different epochs indicating that this system is gravitationally bound. From the infrared colors and magnitudes we infer an approximate spectral type for Gliese 86B at the transition from L to T dwarfs, also called ``early T dwarf'' assuming the classification by \\cite{leggett00}. Although present brown dwarf evolutionary models do not cover the mass and age range probed by this objects, an upper limit of the mass of about MGJ86B <= 70 MJup can be inferred from the models by \\cite{baraffe98}. Dusty model atmospheres appear not to be compatible with the IR colors. Based on observations collected with the 3.6~m Telescope of the European Southern Observatory La Silla under proposal Nos. 66.C-0333, 266.C-5621 and 266.C-5634.

Els, S. G.; Sterzik, M. F.; Marchis, F.; Pantin, E.; Endl, M.; Kürster, M.

2001-04-01

111

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

112

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

113

Radiative transfer in realistic planetary atmospheres. [bibliographies  

NASA Technical Reports Server (NTRS)

Some 40 publications that appeared in scientific journals from 1973 to 1981 as well as 45 scientific reports issued during the grant period are listed by title. Topics cover the development of a matrix operator theory of radiative transfer which made possible the exact model calculations of the radiance as a function of height in planetary atmospheres; calculation of the Mie phase matrix for various types of particles as well as for radiance and polarization in planetary atmospheres; analysis of high dispersion spectroscopic observations of Venus; calculation of curves of growth for Venus; the development of a theory for calculating radiative transfer in spherical shell atmospheres; investigations of zonal winds on Venus; and examination of Rayleigh scattering.

Plass, G. N.; Kattawar, G. W.

1982-01-01

114

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

115

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

116

Signatures of hot hydrogen in the atmosphere of the extrasolar planet HD209458b  

Microsoft Academic Search

Of the extrasolar planets detected so far, about 10% consist of giant planets which orbit very close to their parent stars. The atmospheres of these ``hot-Jupiters'' are largely heated by the immense stellar irradiation. In the case of the planet HD209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizable expansion and escape of

David Sing; G. Ballester; Floyd Herbert

2007-01-01

117

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

118

Atmospheric Excitation of Planetary Normal Modes  

NASA Technical Reports Server (NTRS)

The objectives of this study were to: (1) understand the phenomenon of continuous free oscillations of the Earth and (2) examine the idea of using this phenomenon for planetary seismology. We first describe the results on (1) and present our evaluations of the idea (2) in the final section. In 1997, after almost forty years since the initial attempt by Benioff et al, continuous free oscillations of the Earth were discovered. Spheroidal fundamental modes between 2 and 7 millihertz are excited continuously with acceleration amplitudes of about 0.3-0.5 nanogals. The signal is now commonly found in virtually all data recorded by STS-1 type broadband seismometers at quiet sites. Seasonal variation in amplitude and the existence of two coupled modes between the atmosphere and the solid Earth support that these oscillations are excited by the atmosphere. Stochastic excitation due to atmospheric turbulence is a favored mechanism, providing a good match between theory and data. The atmosphere has ample energy to support this theory because excitation of these modes require only 500-10000 W whereas the atmosphere contains about 117 W of kinetic energy. An application of this phenomenon includes planetary seismology, because other planets may be oscillating due to atmospheric excitation. The interior structure of planets could be learned by determining the eigenfrequencies in the continuous free oscillations. It is especially attractive to pursue this idea for tectonically quiet planets, since quakes may be too infrequent to be recorded by seismic instruments.

Tanimoto, Toshiro

2001-01-01

119

A SEARCH FOR WIDE COMPANIONS TO THE EXTRASOLAR PLANETARY SYSTEM HR 8799  

SciTech Connect

The extrasolar planetary system around HR 8799 is the first multiplanet system ever imaged. It is also, by a wide margin, the highest mass system with >27 Jupiters of planetary mass past 25 AU. This is a remarkable system with no analog in any other known planetary system. In the first part of this paper, we investigated the nature of two faint objects imaged near the system. These objects are considerably fainter (H = 20.4 and 21.6 mag) and more distant (projected separations of 612 and 534 AU) than the three known planetary companions b, c, and d (68-24 AU). It is possible that these two objects could be lower mass planets (of mass approx5M{sub Jup} and approx3M{sub Jup}) that have been scattered to wider orbits. We make the first direct comparison of newly reduced archival Gemini adaptive optics images to archival Hubble Space Telescope/NICMOS images. With nearly a decade between these epochs, we can accurately assess the proper motion nature of each candidate companion. We find that both objects are unbound to HR 8799 and are background. We estimate that HR 8799 has no companions of H < 22 from approx5'' to 15''. Any scattered giant planets in the HR 8799 system are >600 AU or less than 3 M{sub Jup} in mass. In the second part of this paper, we search for any sign of a 'reverse parallax signature' in the astrometric residuals of HR 8799b. No such signal was found and we conclude, as expected, that HR 8799b has the same parallax as HR 8799A. In the third part of this paper, we carry out a search for wider common proper motion objects. We found one object within 1 deg{sup 2} in the Palomar Observatory Sky Survey-Digitized Sky Survey images with similar (<2sigma) proper motions to HR 8799 at a separation of 4.'0. We conclude that it is not likely a bound companion to HR 8799 based on available photometry.

Close, Laird M.; Males, Jared R. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2010-01-20

120

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-lik...

McCullough, P R

2006-01-01

121

Relativistic breakdown in planetary atmospheres  

SciTech Connect

In 2003, a new electrical breakdown mechanism involving the production of runaway avalanches by positive feedback from runaway positrons and energetic photons was introduced. This mechanism, which shall be referred to as 'relativistic feedback', allows runaway discharges in gases to become self-sustaining, dramatically increasing the flux of runaway electrons, the accompanying high-energy radiation, and resulting ionization. Using detailed Monte Carlo calculations, properties of relativistic feedback are investigated. It is found that once relativistic feedback fully commences, electrical breakdown will occur and the ambient electric field, extending over cubic kilometers, will be discharged in as little as 2x10{sup -5} s. Furthermore, it is found that the flux of energetic electrons and x rays generated by this mechanism can exceed the flux generated by the standard relativistic runaway electron model by a factor of 10{sup 13}, making relativistic feedback a good candidate for explaining terrestrial gamma-ray flashes and other high-energy phenomena observed in the Earth's atmosphere.

Dwyer, J. R. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida 32901 (United States)

2007-04-15

122

Predicting Planets in Known Extra-Solar Planetary Systems II: Testing for Saturn-mass Planets  

E-print Network

Recent results have shown that many of the known extrasolar planetary systems contain regions which are stable for massless test particles. We examine the possibility that Saturn-mass planets exist in these systems, just below the detection threshold, and attempt to predict likely orbital parameters for such unseen planets. To do this, we insert a Saturn-mass planet into the stable regions of these systems and integrate its orbit for 100 million years. We conduct 200-600 of these experiments to test parameter space in HD37124, HD38529, 55Cnc, and HD74156. In HD37124 the global maximum of the survival rate of Saturns in parameter space is at semimajor axis a = 1.03 AU, eccentricity e=0.1. In HD38529, only 5% of Saturns are unstable, and the region in which a Saturn could survive is very broad, centered on 0.5

Sean N. Raymond; Rory Barnes

2004-04-09

123

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

124

Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres  

Microsoft Academic Search

We explore detailed chemical equilibrium abundance profiles for a variety of brown dwarf and extrasolar giant planet atmosphere models, focusing in particular on Gl 229B, and derive the systematics of the changes in the dominant reservoirs of the major elements with altitude and temperature. We assume an Anders & Grevesse solar composition of 27 chemical elements and track 330 gas-phase

Adam Burrows; C. M. Sharp

1999-01-01

125

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

Microsoft Academic Search

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

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

2008-01-01

126

Search for Double Transit Extrasolar Planetary Systems: Another Transiting Planet Around OGLE-TR-111 or a False Positive Detection?  

E-print Network

The search for double transit planetary systems opens new possibilities for the transit searches and for studies of orbital stability, stellar irradiation, and migration scenarios, among others. We explore the OGLE lightcurves of stars with confirmed planetary companions (OGLE-TR-10, OGLE-TR-56, OGLE-TR-111, OGLE-TR-113, and OGLE-TR-132), searching for additional transits. The most promising candidate is OGLE-TR-111, where the photometric measurements and the radial velocities are consistent with the presence of a second planet. If confirmed, OGLE-TR-111 would be the first extrasolar planetary system detected by transits. The parameters of the possible new planet OGLE-TR-111c would be: period P = 16.0644 d, semimajor axis a = 0.12 AU, orbital inclination i = 88-89 deg, mass M = 0.7 M_J, radius R = 0.85 R_J, density \\rho = 1.4 g/cm^3. If confirmed, OGLE-TR-111c would be the smallest and densest extrasolar planet measured todate, truly a Jovian planet, with properties intermediate between Jupiter and Saturn, albeit with shorter period. Additional photometric and spectroscopic data would allow to discriminate between a second transiting planet around OGLE-TR-111 and a false positive detection.

Dante Minniti

2005-01-20

127

Purdue University Department of Earth, Atmospheric, and Planetary Sciences  

E-print Network

Purdue University Department of Earth, Atmospheric, and Planetary Sciences Visiting Assistant Professor The Department of Earth, Atmospheric, and Planetary Sciences at Purdue University seeks a visiting. Applicants should have a Ph.D. in atmospheric or related sciences. The successful candidate will teach

Kihara, Daisuke

128

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.

129

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

130

Nonlinear symmetric stability of planetary atmospheres  

SciTech Connect

The energy-Casimir method is applied to the problem of symmetric stability in the context of a compressible, hydrostatic planetary atmosphere with a general equation of state. Linear stability criteria for symmetric disturbances to a zonally symmetric baroclinic flow are obtained. In the special case of a perfect gas the results of Stevens (1983) are recovered. Nonlinear stability conditions are also obtained that, in addition to implying linear stability, provide an upper bound on a certain positive-definite measure of disturbance amplitude.

Bowman, J.C. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Shepherd, T.G. [Toronto Univ., ON (Canada). Dept. of Physics

1994-11-01

131

Reflected Spectra and Albedos of Extrasolar Giant Planets. I. Clear and Cloudy Atmospheres  

Microsoft Academic Search

The reflected spectra of extrasolar giant planets are primarily influenced by Rayleigh scattering, molecular absorption, and atmospheric condensates. We present model geometric albedo and phase-integral spectra and Bond albedos for planets and brown dwarfs with masses between 0.8 and 70 Jupiter masses. Rayleigh scattering predominates in the blue while molecular absorption removes most red and infrared photons. Thus cloud-free atmospheres,

Mark S. Marley; Christopher Gelino; Denise Stephens; Jonathan I. Lunine; Richard Freedman

1999-01-01

132

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

133

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

134

HST-COS observations of the transiting extrasolar planetary system HD 209458b  

NASA Astrophysics Data System (ADS)

We summarize results from deep spectroscopic observations of the HD 209458 planetary system, carried out with the Hubble Space Telescope—Cosmic Origins Spectrograph. Orbitally resolved observations are used to show that hot gas emission lines, arising only in the stellar atmosphere, are not variable, while lower ionizations species found in the upper atmosphere of the hot Jupiter HD 209458b absorb stellar photons during transit. For both C II and Si III, we find mean transit attenuation of ˜8%. The firm detection of silicon is in direct conflict with previous low-resolution studies, which we attribute to long-term variability in the system. We also use these observations to search for auroral emission from the planet, detecting a statistically significant emission feature at 1582 Å that is consistent with H2 photoexcited by stellar O I photons.

France, Kevin; Linsky, Jeffrey L.; Yang, Hao; Stocke, John T.; Froning, Cynthia S.

2011-09-01

135

Radio Detection of Extrasolar Planets  

E-print Network

Radio Detection of Extrasolar Planets: Present and Future Prospects T. Joseph W. Lazio1 & W. M.23 (Fisher et al. 2003) In last decade, exciting discovery of extrasolar planets n ~ 100 planetary systems n of extrasolar planets n ~ 100 planetary systems n Indirect detection via optical signature from host star

Ellingson, Steven W.

136

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

137

Hadley cells in planetary atmospheres without a condensible component  

Microsoft Academic Search

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

R. Caballero; J. Mitchell; R. Pierrehumbert

2006-01-01

138

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

139

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

140

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

141

Extrasolar planets  

PubMed Central

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

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

2000-01-01

142

A spectrum of an extrasolar planet  

Microsoft Academic Search

Of the over 200 known extrasolar planets, 14 exhibit transits in front of their parent stars as seen from Earth. Spectroscopic observations of the transiting planets can probe the physical conditions of their atmospheres. One such technique can be used to derive the planetary spectrum by subtracting the stellar spectrum measured during eclipse (planet hidden behind star) from the combined-light

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

2007-01-01

143

Extrasolar Giant Planets under Strong Stellar Irradiation  

Microsoft Academic Search

We investigate irradiation of extrasolar giant planets (EGPs) by treating the radiative transfer in detail, so that the flux from the parent star interacts with all relevant depths of the planetary atmosphere with no need for a preassumed albedo. Rayleigh scattering (in dust-free models) increases the EGP's flux by orders of magnitude shortward of the Ca II H and K

S. Seager; D. D. Sasselov

1998-01-01

144

University of Oxford: Atmospheric, Oceanic, and Planetary Physics  

NSDL National Science Digital Library

The University of Oxford's Atmospheric, Oceanic, and Planetary Physics group "focuses on the study of physical processes in the atmospheres and oceans of the Earth and other planets, using experimental and theoretical techniques." Users can discover the group's innumerable projects and research tools in the areas involving the development of instruments and carrying out experiments mostly on satellites; analyses of data; and modeling and theoretical work related primarily to climate change, the middle atmosphere, planetary atmospheres, and to laboratory experiments on fluids. Individuals can find informational materials about its facilities and capabilities. The website answers a host of questions related to climate change, the ozone, and planetary phenomena.

145

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

2007-10-21

146

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

147

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

148

Application of MODTRAN® to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

At last year's AMOS conference we described modifications made to MODTRAN5® in order to make it more generally applicable to arbitrary planetary atmospheres. It was then used to compare to a wide variety of spectral data for Neptune, spanning the UV through far-IR spectral regime, ~0.4-200 µm. At this year's meeting, we describe our continuing efforts along these lines, and apply an upgraded version to Saturn, providing similar data comparisons over a broad wavelength region. The primary upgrades include an input option to automatically generate the pressure-altitude profile from the hydrostatic equation, development of a molecular band model parameter database based on the isotopic abundances of Saturn, and the addition of continua spectral data, such as H2-CH4 and CH4-CH4 dimer absorption coefficients. Clouds and haze, which are highly variable and play a dominant role in the radiation transfer in Saturn's atmosphere, provide a good test of MODTRAN®'s capability to treat these complications.

Berk, A.; Bernstein, L.; Duff, J.

149

Composition and origin of the atmosphere of Jupiter—an update, and implications for the extrasolar giant planets  

Microsoft Academic Search

New developments have led to this update of the composition and origin of Jupiter's atmosphere that were originally discussed in our Planet. Space Sci. 47 (1999) 1243 paper. Since Jupiter can provide important insight into the atmospheres of extrasolar giant planets (EGP), we also discuss here the possible implications of the first detection of an atmosphere on an EGP. The

S. k. Atreya; P. R Mahaffy; H. b. Niemann; M. h. Wong; T. c. Owen

2003-01-01

150

A similarity approach to the atmospheric dynamics of giant extrasolar planets and brown dwarfs  

NASA Astrophysics Data System (ADS)

We present an assessment of the most plausible dynamical regimes operating in the atmospheres of giant extrasolar planets (EGP) and cold (``methane'') brown dwarfs from the available data on a selected group of objects. The most important parameters controlling the atmospheric circulation are the rotation angular velocity and the energy balance between the internal heat source and the star's insolation. The first parameter can be reasonably constrained for some of these objects by theoretical arguments. The second is constrained by the observations. Assuming a hydrogen composition, we discuss possible scenarios for the first order atmospheric motions in terms of characteristic geophysical fluid dynamic numbers and representative time constants. The analysis is applied to the family of extrasolar giant planets classified recently by Sudarsky et al. (\\cite {sudarsky}) according to their effective temperature and Bond albedo. For completeness we extend this study to cold (``methane'') brown dwarfs. Three main dynamical regimes emerge from this analysis: (A) Close EGP (``hot jupiters'') with spin-orbit locked (slowly rotating) planets, have their atmospheres mainly under the star's radiative control. Super-rotating atmospheric motions between the heated and cooled hemispheres can be expected. (B) Atmospheres with their dynamics controlled by both the internal and external energy sources, with Coriolis forces producing zonal motions (Jupiter like objects). (C) Cold brown dwarfs, with motions controlled by the internal heat source (thermally driven turbulent convection) producing intense vertical velocities that dominate the motion field.

Sanchez-Lavega, A.

2001-10-01

151

Meteoric Material: An Important Component of Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Interplanetary dust particles (IDPs) interact with all planetary atmospheres and leave their imprint as perturbations of the background atmospheric chemistry and structure. They lead to layers of metal ions that can become the dominant positively charged species in lower ionospheric regions. Theoretical models and radio occultation measurements provide compelling evidence that such layers exist in all planetary atmospheres. In addition IDP ablation products can affect neutral atmospheric chemistry, particularly at the outer planets where the IDPs supply oxygen compounds like water and carbon dioxide to the upper atmospheres. Aerosol or smoke particles from incomplete ablation or recondensation of ablated IDP vapors may also have a significant impact on atmospheric properties.

Grebowsky, Joseph M.; Moses, Julianne I.; Pesnell, W. Dean; Vondrak, Richard R. (Technical Monitor)

2001-01-01

152

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

153

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

154

Remote Sensing of Planetary Properties and Biosignatures on Extrasolar Terrestrial Planets  

Microsoft Academic Search

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

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

2002-01-01

155

Planetary Atmosphere Dynamics and Radiative Transfer  

NASA Technical Reports Server (NTRS)

This research program has dealt with two projects in the field of planetary atmosphere dynamics and radiative energy transfer, one theoretical and one experimental. The first project, in radiative energy transfer, incorporated the capability to isolate and quantify the contribution of individual atmospheric components to the Venus radiative balance and thermal structure to greatly improve the current understanding of the radiative processes occurring within the Venus atmosphere. This is possible by varying the mixing ratios of each gas species, and the location, number density and aerosol size distributions of the clouds. This project was a continuation of the work initiated under a 1992 University Consortium Agreement. Under the just completed grant, work has continued on the use of a convolution-based algorithm that provided the capability to calculate the k coefficients of a gas mixture at different temperatures, pressures and spectral intervals from the separate k-distributions of the individual gas species. The second primary goal of this research dealt with the Doppler wind retrieval for the Successful Galileo Jupiter probe mission in December, 1995. In anticipation of the arrival of Galileo at Jupiter, software development continued to read the radioscience and probe/orbiter trajectory data provided by the Galileo project and required for Jupiter zonal wind measurements. Sample experiment radioscience data records and probe/orbiter trajectory data files provided by the Galileo Radioscience and Navigation teams at the Jet Propulsion Laboratory, respectively, were used for the first phase of the software development. The software to read the necessary data records was completed in 1995. The procedure by which the wind retrieval takes place begins with initial consistency checks of the raw data, preliminary data reductions, wind recoveries, iterative reconstruction of the probe descent profile, and refined wind recoveries. At each stage of the wind recovery consistency is checked and maintained between the orbiter navigational data, the radioscience data, and the probe descent profile derived by the Atmospheric Instrument Team. Preliminary results show that the zonal winds at Jupiter increase with depth to approximately 150 m/s.

Atkinson, David H.

1996-01-01

156

The Blue Dot Workshop: Spectroscopic Search for Life on Extrasolar Planets  

NASA Technical Reports Server (NTRS)

This workshop explored the key questions and challenges associated with detecting life on an extrasolar planet. The final product will be a NASA Conference Publication which includes the abstracts from 21 talks, summaries of key findings, and recommendations for future research. The workshop included sessions on three related topics: the biogeochemistry of biogenic gases in the atmosphere, the chemistry and spectroscopy of planetary atmospheres, and the remote sensing of planetary atmospheres and surfaces. With the observation that planetary formation is probably a common phenomenon, together with the advent of the technical capability to locate and describe extrasolar planets, this research area indeed has an exciting future.

Des Marais, David J. (Editor)

1997-01-01

157

Astronomical, physical, and meteorological parameters for planetary atmospheres  

NASA Technical Reports Server (NTRS)

A newly compiled table of astronomical, physical, and meteorological parameters for planetary atmospheres is presented. Formulae and explanatory notes for their application and a complete listing of sources are also given.

Allison, Michael; Travis, Larry D.

1986-01-01

158

Atmospheric planetary-wave response to external forcing  

NASA Technical Reports Server (NTRS)

A summary of the progress report is given, covering the following areas: atmospheric circulation, planetary waves, adaption of the model to the Cyber 205, continental heat flux anomalies, and nonlinear evolution of inertial instabilities in the tropics.

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

1983-01-01

159

Clouds in the atmospheres of extrasolar planets. IV. On the scattering greenhouse effect of CO2 ice particles: Numerical radiative transfer studies  

E-print Network

Owing to their wavelengths dependent absorption and scattering properties, clouds have a strong impact on the climate of planetary atmospheres. Especially, the potential greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars. We study the radiative effects of CO2 ice particles obtained by different numerical treatments to solve the radiative transfer equation. The comparison between the results of a high-order discrete ordinate method and simpler two-stream approaches reveals large deviations in terms of a potential scattering efficiency of the greenhouse effect. The two-stream methods overestimate the transmitted and reflected radiation, thereby yielding a higher scattering greenhouse effect. For the particular case of a cool M-type dwarf the CO2 ice particles show no strong effective scattering greenhouse eff...

Kitzmann, D; Rauer, H

2013-01-01

160

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

161

First International Conference on Laboratory Research for Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Proceedings of the First International Conference on Laboratory Research for Planetary Atmospheres are presented. The covered areas of research include: photon spectroscopy, chemical kinetics, thermodynamics, and charged particle interactions. This report contains the 12 invited papers, 27 contributed poster papers, and 5 plenary review papers presented at the conference. A list of attendees and a reprint of the Report of the Subgroup on Strategies for Planetary Atmospheres Exploration (SPASE) are provided in two appendices.

Fox, Kenneth (editor); Allen, John E., Jr. (editor); Stief, Louis J. (editor); Quillen, Diana T. (editor)

1990-01-01

162

Vibrational-Rotational Spectroscopy For Planetary Atmospheres, volume 1  

NASA Technical Reports Server (NTRS)

Comprehensive information on the composition and dynamics of the varied planetary atmospheres is summarized. New observations resulted in new demands for supporting laboratory studies. Spectra observed from spacecraft used to interpret planetary atmospheric structure measurements, to aid in greenhouse and cloud physics calculations, and to plan future experiments are discussed. Current findings and new ideas of physicists, chemists, and planetry astronomers relating to the knowledge of the structure of things large and small, of planets and of molecules are summarized.

Mumma, M. J. (editor); Fox, K. (editor); Hornstein, J. (editor)

1982-01-01

163

Infrared experiments for spaceborne planetary atmospheres research. Full report  

NASA Technical Reports Server (NTRS)

The role of infrared sensing in atmospheric science is discussed and existing infrared measurement techniques are reviewed. Proposed techniques for measuring planetary atmospheres are criticized and recommended instrument developments for spaceborne investigations are summarized for the following phenomena: global and local radiative budget; radiative flux profiles; winds; temperature; pressure; transient and marginal atmospheres; planetary rotation and global atmospheric activity; abundances of stable constituents; vertical, lateral, and temporal distribution of abundances; composition of clouds and aerosols; radiative properties of clouds and aerosols; cloud microstructure; cloud macrostructure; and non-LTE phenomena.

1981-01-01

164

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

PubMed

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 eta (atmospheric thickness), omega (rotation rate) and xi (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 xi 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 xi is sufficiently large (as for the four examples in the solar system), or if the rotation rate omega is sufficiently small. The model indicates, however, that the dynamical constraint does influence the MEP state when xi 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

2010-05-12

165

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

166

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

167

Time-dependent simulations of disk-embedded planetary atmospheres  

NASA Astrophysics Data System (ADS)

At the early stages of evolution of planetary systems, young Earth-like planets still embedded in the protoplanetary disk accumulate disk gas gravitationally into planetary atmospheres. The established way to study such atmospheres are hydrostatic models, even though in many cases the assumption of stationarity is unlikely to be fulfilled. Furthermore, such models rely on the specification of a planetary luminosity, attributed to a continuous, highly uncertain accretion of planetesimals onto the surface of the solid core. We present for the first time time-dependent, dynamic simulations of the accretion of nebula gas into an atmosphere around a proto-planet and the evolution of such embedded atmospheres while integrating the thermal energy budget of the solid core. The spherical symmetric models computed with the TAPIR-Code (short for The adaptive, implicit RHD-Code) range from the surface of the rocky core up to the Hill radius where the surrounding protoplanetary disk provides the boundary conditions. The TAPIR-Code includes the hydrodynamics equations, gray radiative transport and convective energy transport. The results indicate that diskembedded planetary atmospheres evolve along comparatively simple outlines and in particular settle, dependent on the mass of the solid core, at characteristic surface temperatures and planetary luminosities, quite independent on numerical parameters and initial conditions. For sufficiently massive cores, this evolution ultimately also leads to runaway accretion and the formation of a gas planet.

Stökl, A.; Dorfi, E. A.

2014-03-01

168

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

169

Planetary Atmospheres and the Search for Life.  

ERIC Educational Resources Information Center

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

Owen, Tobias

1982-01-01

170

NASA Planetary Astronomy Lunar Atmospheric Imaging Study  

NASA Technical Reports Server (NTRS)

Authors have conducted a program of research focused on studies of the lunar atmosphere. Also present preliminary results of an ongoing effort to determine the degree that metal abundances in the lunar atmosphere are stoichiometric, that is, reflective of the lunar surface composition. We make the first-ever mid-ultraviolet spectroscopic search for emission from the lunar atmosphere.

Stern, S. Alan

1996-01-01

171

On the stability of extrasolar planetary systems and other closely orbiting pairs  

NASA Astrophysics Data System (ADS)

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 LX) 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 little orbital angular momentum (relative to the total) and are not in an equilibrium configuration. Finally, we consider the time evolution of these planetary systems; the results constrain the tidal quality factor of the stars and suggest that 106 ? Q* ? 107.

Adams, Fred C.; Bloch, Anthony M.

2015-02-01

172

Planetary migration and extrasolar planets in the 2\\/1 mean-motion resonance  

Microsoft Academic Search

In this paper, we present a new set of corotational solutions for the 2\\/1 commensurability, including previously known solutions and new results. Comparisons with observed exoplanets show that current orbital fits of three proposed resonant planetary systems are consistent with apsidal corotations. We also discuss the possible relationship between the current orbital elements fits of known exoplanets in the 2\\/1

C. Beaugé; T. A. Michtchenko; S. Ferraz-Mello

2006-01-01

173

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

174

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

175

High-Contrast Imaging: A Wider View on Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

Although very successful (more than 350 planets discovered up to now) indirect methods for extrasolar planet detection (radial velocity, transits) are sensitive to planets quite close to their hosts. Moreover, accurate studies of planet characteristics are feasible only for a subset of object which are strongly irradiated. Standing at this point, any information about the exoplanets in wide orbits (more than 5-10 AU) is missing. High contrast imaging could be the key to open us a door to an unexplored region of star planet separation and to shed light on these unknown far away worlds. But it's not just a matter of detections. In fact coupling integral field spectrographs to extreme adaptive optic modules at the focus of 8m class telescopes (SPHERE for VLT and GPI for South Gemini), and in the future to ELTs (EPICS), would allow us to perform a first order characterization of the exoplanets themselves. Here we present the potential of the high contrast imaging technique, comparing it's capabilities with the ones of the indirect methods.

Bonavita, M.; Claudi, R. U.; Tinetti, G.; Beuzit, J.; Chauvin, G.; Desidera, S.; Gratton, R.; Kasper, M.

2011-12-01

176

Crossing the Boundaries in Planetary Atmospheres - From Earth to Exoplanets  

NASA Technical Reports Server (NTRS)

The past decade has been an especially exciting time to study atmospheres, with a renaissance in fundamental studies of Earths general circulation and hydrological cycle, stimulated by questions about past climates and the urgency of projecting the future impacts of humankinds activities. Long-term spacecraft and Earth-based observation of solar system planets have now 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, held in Annapolis, MD from June 24-27, 2013 gathered Earth, solar system, and exoplanet scientists to share experiences, insights, and challenges from their individual disciplines, and discuss areas in which thinking broadly might enhance our fundamental understanding of how atmospheres work.

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

2013-01-01

177

Modeling Planetary Waves in the Middle Atmosphere  

NASA Technical Reports Server (NTRS)

In our 3D Numerical Spectral Model (NSM) that incorporates the Doppler Spread Parameterization of Hines, planetary waves are generated with zonal wavenumbers 1-4 that have amplitudes as large as 25 m/s and periods between 50 and 2 days. The waves are generated spontaneously, i.e., without external source, and presumably represent normal modes. Numerical experiments are discussed to shed light on the generation mechanisms. For the wavenumbers 1 and 2 with periods primarily between 4 and 15 days, both eastward and westward propagating waves are generated and their amplitudes are affected significantly by the gravity wave source. For the wavenumbers, 3 and 4 in the upper mesosphere, the waves are virtually monochromatic, with periods around 2.5 days and they propagate westward. These waves behave like Rossby gravity waves; their amplitudes are largest during solstice where the baroclinic instability is playing an important role, but the waves decay when the gravity wave momentum source is turned off. The planetary waves generated in the model produce large amplitude modulations of the diurnal tides at altitudes above 80 km, but contrary to expectations they are not playing an important role for the seasonal variations of the tides. Preliminary results show that such Rossby gravity waves are also generated near the tropopause and are influencing significantly the QBO that is generated in the model.

Mengel, J. G.; Mayr, H. G.; Chan, K. L.; Porter, H. C.; Einaudi, Franco (Technical Monitor)

2000-01-01

178

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

179

Planetary Atmospheres Earth and the Other Terrestrial Worlds  

E-print Network

make planetary surfaces warmer through greenhouse effect #12;3 Greenhouse Effect · Visible light passes without greenhouse effect · Earth would be 31°C colder (below freezing on average) Thought Question What space Where does an atmosphere end? · Small amounts of gas are present even at > 300 km Effects

Crenshaw, Michael

180

The greenhouse effect of planetary atmospheres  

Microsoft Academic Search

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

K. Ya. Kondratyev; N. I. Moskalenko

1980-01-01

181

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

182

Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres  

E-print Network

We calculate detailed chemical abundance profiles for a variety of brown dwarf and extrasolar giant planet atmosphere models, focusing in particular on Gliese 229B, and derive the systematics of the changes in the dominant reservoirs of the major elements with altitude and temperature. We assume an Anders and Grevesse (1989) solar composition of 27 chemical elements and track 330 gas--phase species, including the monatomic forms of the elements, as well as about 120 condensates. We address the issue of the formation and composition of clouds in the cool atmospheres of substellar objects and explore the rain out and depletion of refractories. We conclude that the opacity of clouds of low--temperature ($\\le$900 K), small--radius condensibles (specific chlorides and sulfides), may be responsible for the steep spectrum of Gliese 229B observed in the near infrared below 1 \\mic. Furthermore, we assemble a temperature sequence of chemical transitions in substellar atmospheres that may be used to anchor and define a sequence of spectral types for substellar objects with T$_{eff}$s from $\\sim$2200 K to $\\sim$100 K.

A. Burrows; C. Sharp

1998-07-06

183

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

184

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

185

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

186

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

187

Extra-solar planetary systems. III - Potential sites for the origin and evolution of technical civilisations  

NASA Astrophysics Data System (ADS)

A series of runs of the Silicon Creation' computer model developed by Fogg (1985) has been analyzed in order to evaluate the probable abundance of planets possessing suitable conditions for the evolution of technologically adept forms of life. The evolutionary simulation encompassed 100,000 disk stars of varying mass, metallicity, and age, and focused on civilizations that may have come into existence on planets over the past 10 to the 10th years of planetary disk history. The frequency of such sites is determined to be 0.00292, and the frequency of planets developing a technological civilization is 0.00009; these figures are two orders of magnitude lower than the most optimistic manipulations of the Drake equation, but not low enough to resolve the Fermi paradox, according to which an alien civilization, if existent, should long ago have colonized the entire Galaxy.

Fogg, M. J.

1986-07-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

189

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

NASA Astrophysics Data System (ADS)

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 and Probe, ISO and Voyager, complemented by ground-based observations (Atreya et al., PSS 47, 1243, 1999; Encrenaz et al., PSS, 47, 1223, 1999; Atreya et al., PSS, 2002, in press). Although the atmosphere is made up of mostly H and He, trace amounts of CH4 and its products, H O, NH 3, H2S,22 heavy noble gases (Ne, Ar, Kr, Xe), and disequilibrium species (PH3, CO, CO2, GeH4, AsH3), are also detected. From measurements of the trace constituents in Jupiter's upper and the deep well-mixed troposphere by the Galileo Probe, it has been possible to determine the "bulk" abundance of the heavy elements, which is key to understanding the origin and evolution of the planet's atmosphere. C, N, S, Ar, Kr and Xe are all found to be enriched by a factor of 2-4 relative to their solar ratios to H. This unexpected finding led Owen et al. (Nature, 402, 269, 1999) to suggest that the icy planetesimals that formed Jupiter must have had a low temperature (=30 K) origin in order for them to trap the volatiles containing the heavy elements. An alternate hypothesis - according to which the volatiles were trapped in clathrate hydrates instead (Gautier et al., Ap. J., 550, L227, 2001) - overestimates Jupiter's sulfur abundance, and it too requires a remarkably low temperature of =38 K for argon clathration (Gautier et al., Ap. J., 559, L183, 2001) Could the known composition of Jupiter help in understanding the atmospheres of the EGP's? So far, only sodium has been detected in the atmosphere of an EGP that orbits a sun-like star, HD 209458, at 0.0468 AU (Charbonneau et al., Ap. J., 568, 377, 2002). However, sodium has not been detected in the atmosphere of Jupit er. If the above EGP formed like Jupiter, and so started out its life colder (than its current equilibrium temperature of as much as 1400 K), the observed sodium in its atmosphere may be of an extraplanetary origin, rather being primordial (Atreya et al., PSS, 2002, in press).

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

190

SOIR and NOMAD: Characterization of Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The Belgian Institute for Space Aeronomy is involved in the Venus Express mission (VeX), launched in 2006 and in the ExoMars Trace Gas Orbiter mission (TGO), due for launch in 2016. BISA is responsible for one instrument in each mission, SOIR onboard VeX and NOMAD onboard TGO respectively. The SOIR instrument onboard Venus Express allows observations of trace gases in the Venus atmosphere, at the terminator for both the morning and evening sides of the planet and for almost all latitudes. It has been designed to measure spectra in the IR region (2.2 - 4.3 µm) of the Venus atmosphere using the solar occultation technique1. This method derives unique information on the vertical composition and structure of the mesosphere and lower thermosphere2,3,4,5. It is unique in terms of spectral coverage and spectral resolution (0.15 cm-1), and is ideally designed to probe the Venus atmosphere for CO2 as well as trace gases, such as H2O, CO, HCl and HF. SOIR is capable of (1) providing vertical information on a broad series of species, such as CO2, CO, H2O, HCl, HF, SO26 and aerosols 7, covering the so far sparsely known region located above the clouds, (2) contributing to a better understanding of the dynamics and stability of the atmosphere by delivering total density and kinetic temperature profiles at the terminator, an up-to-now still unchartered region, and (3) detecting weak absorption bands of rare CO2 isotopologues8, due to the sensitivity of SOIR, the high concentration of CO2 on Venus and the long absorption paths sounded during solar occultations.

Robert, S.; Chamberlain, S.; Mahieux, A.; Thomas, I.; Wilquet, V.; Vandaele, A. C.

2014-06-01

191

Planetary Formation: From the Earth and Moon to Extrasolar Giant Planets  

NASA Technical Reports Server (NTRS)

An overview of current theories of star and planet formation is presented. These models are based upon observations of the Solar System and of young stars and their environments. They predict that rocky planets should form around most single stars, although it is possible that in some cases such planets are lost to orbital decay within the protoplanetary disk. The frequency of formation of gas giant planets is more difficult to predict theoretically. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth like terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Specific issues to be discussed include: (1) how large a solid core is needed to initiate rapid accumulation of gas? (2) can giant planets form very close to stars? (3) could a giant impact leading to lunar formation have occurred approximately 100 million years after the condensation of the oldest meteorites?

Lissauer, Jack; DeVincenzi, Donald (Technical Monitor)

1999-01-01

192

Planetary Formation: From the Earth and Moon to Extrasolar Giant Planets  

NASA Technical Reports Server (NTRS)

An overview of current theories of star and planet formation is presented. These models are based upon observations of the Solar System and of young stars and their environments. They predict that rocky planets should form around most single stars, although it is possible that in some cases-such planets are lost to orbital decay within the protoplanetary disk. The frequency of formation of gas giant planets is more difficult to predict theoretically. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth like terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Specific issues to be discussed include: (1) how large a solid core is needed to initiate rapid accumulation of gas? (2) can giant planets form very close to stars? (3) could a giant impact leading to lunar formation have occurred approx. 100 million years after the condensation of the oldest meteorites?

Lissauer, Jack J.; DeVincenzi, Donald (Technical Monitor)

1999-01-01

193

Models for aurora and airglow emissions from other planetary atmospheres  

NASA Technical Reports Server (NTRS)

Models for aurora and airglow emissions from planetary atmospheres other than the earth are surveyed, with emphasis on accomplishments of the last seven years. The goals of modeling the terrestrial planets and modeling the outer planets are very different. Because less is known about the atmospheres of the outer planets, models of their luminosity seek to provide information about the basic structure of the atmospheres and to identify the major production mechanisms. Models of the terrestrial planets have recently begun to address more complex questions about the abundances of trace and minor constituents, about transport phenomena, and about spatial and temporal variations in the atmosphere and in the processes that produce the emissions. In addition, there are a few instances in which models have been used to elucidate atomic and molecular processes that are difficult to study either in the terrestrial atmosphere or in the laboratory.

Fox, J. L.

1986-01-01

194

Solar photo rates for planetary atmospheres and atmospheric pollutants  

Microsoft Academic Search

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

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

1992-01-01

195

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

196

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

197

Formation of spectral lines in planetary atmospheres. I - Theory for cloudy atmospheres: Application to Venus.  

NASA Technical Reports Server (NTRS)

The theory of the formation of spectral lines in a cloudy planetary atmosphere is studied in detail. It is shown that models based upon homogeneous, isotropically scattering atmospheres cannot be used to reproduce observed spectroscopic features of phase effect and the shape of spectral lines for weak and strong bands. The theory must, therefore, be developed using an inhomogeneous (gravitational) model of a planetary atmosphere, accurately incorporating all the physical processes of radiative transfer. Such a model of the lower Venus atmosphere, consistent with our present knowledge, is constructed. The results discussed in this article demonstrate the effects of the parameters that describe the atmospheric model on the spectroscopic features of spectral line profile and phase effect, at visible and near infrared wavelengths. This information enables us to develop a comprehensive theory of line formation in a Venus atmosphere.

Hunt, G. E.

1972-01-01

198

Infrared line parameters at low temperatures relevant to planetary atmospheres  

NASA Technical Reports Server (NTRS)

Employing the techniques that were described in several publications for measuring infrared lineshifts, linewidths and line intensities with a tunable diode laser, these parameters were measures for lines in the important infrared bands of several molecules of interest to the planetary astronomer at low temperatures that are relevant to planetary atmospheres using He, Ne, Ar, H2, N2, O2, and air as the perturbers. In addition to obtaining the many original data on the temperature dependence of the intensities and linewidths, it was also the first measurement of the same for the collision-induced lineshift of an infrared line and it showed that it was markedly different from that of the corresponding collision-broadened linewidth.

Varanasi, Prasad

1990-01-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

200

Studies on possible propagation of microbial contamination in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Maintained aerosols were studied to demonstrate the metabolism and propagation of microbes in clouds which could occur in the course of a probe of a planetary atmosphere. Bacteriophage was used as a tool to test whether the mechanisms for DNA production remain intact and functional within the airborne bacterial cell. In one test method, bacteria were mixed with coliphage in an atomizer to allow attachment before aerosolization; in another, two suspensions were atomized saperately into a common air stream prior to aerosolization. Results show that biochemical and physiological mechanisms to allow aerobic microbes to propagate in the airborne state do exist.

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

1975-01-01

201

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

202

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

203

Extrasolar Planets Lecture 4: Discoveries & Results  

E-print Network

Extrasolar Planets Lecture 4: Discoveries & Results Prof. Quentin A Parker ASTR178 - other worlds; More than 400 extrasolar planets! Over 25 systems with more than one planet Systems similar to our: planets and planetary systems 1 #12;ASTR178 - other worlds: planets and planetary systems 2 #12;ASTR178

Parker, Quentin A.

204

A Spectrum of an Extrasolar Planet  

E-print Network

Of the over 200 known extrasolar planets, 14 exhibit transits in front of their parent stars as seen from Earth. Spectroscopic observations of the transiting planets can probe the physical conditions of their atmospheres. One such technique can be used to derive the planetary spectrum by subtracting the stellar spectrum measured during eclipse (planet hidden behind star) from the combined-light spectrum measured outside eclipse (star + planet). Although several attempts have been made from Earth-based observatories, no spectrum has yet been measured for any of the established extrasolar planets. Here we report a measurement of the infrared spectrum (7.5--13.2 micron) of the transiting extrasolar planet HD209458b. Our observations reveal a hot thermal continuum for the planetary spectrum, with approximately constant ratio to the stellar flux over this wavelength range. Superposed on this continuum is a broad emission peak centered near 9.65 micron that we attribute to emission by silicate clouds. We also find a narrow, unidentified emission feature at 7.78 micron. Models of these ``hot Jupiter'' planets predict a flux peak near 10 micron, where thermal emission from the deep atmosphere emerges relatively unimpeded by water absorption, but models dominated by water fit the observed spectrum poorly.

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

2007-02-20

205

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

E-print Network

Context. Low-mass extrasolar planets are presently being discovered at an increased pace by radial velocity and transit surveys, opening 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 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 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_Earth, 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 perio...

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

2010-01-01

206

Constructing an advanced software tool for planetary atmospheric modeling  

NASA Technical Reports Server (NTRS)

Scientific model building can be an intensive and painstaking process, often involving the development of large and complex computer programs. Despite the effort involved, scientific models cannot be easily 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. In this paper, we describe a prototype for a scientific modeling software tool that serves as an aid to the scientist in developing and using models. This tool includes an interactive intelligent graphical interface, a high level domain specific modeling language, a library of physics equations and experimental datasets, and a suite of data display facilities. Our prototype has been developed in the domain of planetary atmospheric modeling, and is being used to construct models of Titan's atmosphere.

Keller, Richard M.; Sims, Michael; Podolak, Ester; Mckay, Christopher

1990-01-01

207

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

208

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

209

NUMERICAL MODEL OF A NON-STEADY ATMOSPHERIC PLANETARY BOUNDARY LAYER, BASED ON SIMILARITY  

E-print Network

NUMERICAL MODEL OF A NON-STEADY ATMOSPHERIC PLANETARY BOUNDARY LAYER, BASED ON SIMILARITY THEORY S November, 1991) Abstract. A numerical model of a non-stationary atmospheric planetary boundary layer (PBL boundary layer (PBL) subjected to diurnal variations. The typical pattern of diurnal changes

Fedorovich, Evgeni

210

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

Microsoft Academic Search

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

A. Burrows; D. Sudarsky; I. Hubeny

2006-01-01

211

How do Atmospheres Affect Planetary Temperatures: Activity A How do Atmospheres Interact with Solar Energy?  

NSDL National Science Digital Library

In this 2-part inquiry-based lesson, students conduct a literature search to determine the characteristics of the atmospheres of different planets (Venus, Mercury, Mars and Earth). After collecting and analyzing data, student teams design and conduct a controlled physical experiment using a lab apparatus to learn about the interaction of becomes CO², air, and temperature. The resource includes student worksheets, a design proposal, and student questions. Connections to contemporary climate change are addressed. This lesson is the first of four in Topic 4, "How do Atmospheres Affect Planetary Temperatures?" within the resource, Earth Climate Course: What Determines a Planet's Climate?

2012-08-03

212

Extrasolar Giant Planets under Strong Stellar Irradiation  

NASA Astrophysics Data System (ADS)

We investigate irradiation of extrasolar giant planets (EGPs) by treating the radiative transfer in detail, so that the flux from the parent star interacts with all relevant depths of the planetary atmosphere with no need for a preassumed albedo. Rayleigh scattering (in dust-free models) increases the EGP's flux by orders of magnitude shortward of the Ca II H and K doublet (3930 Å), and the spectral features of the parent star are exactly reflected. The inclusion of dust increases the reflected flux in the blue. In the optical and near-IR, the thermal absorption of the planet takes over, but the absorption features are changed by the irradiation.

Seager, S.; Sasselov, D. D.

1998-08-01

213

Searching for extra-solar planets and probing the atmosphere of Bulge giant stars through gravitational microlensing  

NASA Astrophysics Data System (ADS)

A galactic microlensing effect occurs when a luminous object (the source) located in the Bulge of the Milky Way is temporarily magnified by an intervening star (the "microlens'') passing close to its line of sight. This phenomenom is used for searching extra-solar planets and constraining their abundance, as well as probing the atmosphere of Bulge giant stars. The PLANET collaboration (Probing Lensing Anomalies NETwork) monitors carefully chosen ongoing microlensing events on a round-the-clock basis from observatories in the southern hemisphere. Mathematical and numerical methods are developed to deal with both the highly non-linear equations and the wide parameter space plagued with many local minima. Microlensing exoplanet detection is possible because planets can induce perturbations to the standard lensing light curves. Its sensitivity can go down to Earth-mass planets, thanks to gravitational caustics that arise from a binary lens. If crossed by the source, additional secondary magnification peaks in the light curve can occur. OGLE 2005-BLG-390Lb is the third extra-solar planet detected by this method so far, and its discovery is reported here. It is the lightest exoplanet to date - about five Earth masses - located at a rather large distance of its star, that is about three astronomical units. A selection of microlensing events monitored during the 1995-2004 period was used to derive limits on exoplanets abundance around red dwarf stars. The method is described and detection efficiency diagrams are provided as a basis of the statistical analysis. Last, a differential magnification effect over the disk of the source star is used as a tool to probe Bulge giants stellar atmospheres. Limb-darkening parameters of a set of stars have been measured and compared to atmosphere models. Moreover, a high-resolution spectroscopic monitoring of a Bulge G5III giant at 9 kpc made possible both the measurement of the individual lines equivalent width and the direct detection of its chromosphere.

Cassan, Arnaud

2005-12-01

214

Plasma-induced Escape and Alterations of Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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 will review the results of simulations of the plasma bombardment at a number of solar system bodies and use those data to describe the effect on the upper atmosphere and on escape. Of considerable recent interest is the modeling of escape from Titan. Prior to Cassini’s tour of the Saturnian system, plasma-induced escape was suggested to be the dominant loss process, but recent models of enhanced thermal escape, often referred to as ‘slow hydrodynamic’ escape, have been suggested to lead to much larger Titan atmospheric loss rates (Strobel 2008; Cui et al. 2008). Such a process has been suggested to be active at some point in time on a number of solar system bodies. I will present hybrid fluid/ kinetic models of the upper atmosphere of certain bodies in order to test both the plasma-induced and thermal escape processes. Preliminary results suggest that the loss rates estimated using the ‘slow hydrodynamic’ escape process can be orders of magnitude too large. The implications for Mars, Titan and Pluto will be discussed. Background for this talk is contained in the following papers (Johnson 2004; 2009; Chaufray et al. 2007; Johnson et al. 2008; 2009; Tucker and Johnson 2009). References: Chaufray, J.Y., R. Modolo, F. Leblanc, G. Chanteur, R.E. Johnson, and J.G. Luhmann, Mars Solar Wind interaction: formation of the Martian corona and atmosphric loss to space, JGR 112, E09009, doi:10.1029/2007JE002915 (2007) Cui, J., Yelle, R. V., Volk, K. Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere. J. Geophys. Res. 113, doi:10.1029/2007JE003032 (2008) Johnson, R.E. Plasma-induced Sputtering of an Atmosphere. in Space Science Rev. 69, 215-253 (1994). Johnson, R.E., The Magnetospheric Plasma-Driven Evolution of Satellite Atmospheres, Astrophys. J. 609: L99-L102 (2004). Johnson, R.E., M.R. Combi, J.L. Fox, W-H. Ip, F. Leblanc, M.A. McGrath, V.I. Shematovich, D.F. Strobel, J.H. Waite Jr, Exospheres and Atmospheric Escape, Chapter in Comparative Aeronomy, Ed. A. Nagy, Space Sci. Rev. 139: 355-397, DOI 10.1007/s11214-008-9415-3 (2008) Johnson, R.E., Sputtering and heating of Titan's upper atmosphere, Phil. Trans. R. Soc. A 367, 753-771, doi:10.1098/rsta.2008.0244 (2009) Johnson, R.E., O.J. Tucker, M. Michael, E.C. Sittler, H.T. Smith, D.T. Young, and J.H. Waite, Mass Loss Processes in Titan's Upper Atmosphere, Springer-Verlag in press (2009) Strobel, D. F. Titan's hydrodynamically escaping atmosphere. Icarus 193, 588—594 (2008)

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

2009-12-01

215

Frequency Analysis and Extrasolar Planets  

Microsoft Academic Search

\\u000a The discovery [13] (and confirmation [14]) of the first extrasolar planetary system by Wolszczan & Frail (1991) around the pulsar B1257+12 began a new era in this\\u000a exciting field of astronomy. A few years later, in 1995, the first extrasolar planet around a normal star was found by Queloz\\u000a & Mayor [10]. This was followed by other such discoveries [9].

Maciej Konacki; Andrzej J. Maciejewski

1999-01-01

216

Theory of Extrasolar Giant Planet Transits  

NASA Astrophysics Data System (ADS)

We present a synthesis of physical effects influencing the observed light curve of an extrasolar giant planet (EGP) transiting its host star. The synthesis includes a treatment of Rayleigh scattering, cloud scattering, refraction, and molecular absorption of starlight in the EGP atmosphere. Of these effects, molecular absorption dominates in determining the transit-derived radius R for planetary orbital radii less than a few AU. Using a generic model for the atmosphere of EGP HD 209458b, we perform a fit to the best available transit light-curve data and infer that this planet has a radius at a pressure of 1 bar, R1, equal to 94,430 km, with an uncertainty of ~500 km arising from plausible uncertainties in the atmospheric temperature profile. We predict that R will be a function of wavelength of observation, with a robust prediction of at least +/-1% variations at infrared wavelengths where H2O opacity in the high EGP atmosphere dominates.

Hubbard, W. B.; Fortney, J. J.; Lunine, J. I.; Burrows, A.; Sudarsky, D.; Pinto, P.

2001-10-01

217

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

218

Composition and origin of the atmosphere of Jupiter - an update, and implications for the extrasolar giant planets  

NASA Astrophysics Data System (ADS)

New developments have led to this update of the composition and origin of Jupiter's atmosphere that were originally discussed in our Planet. Space Sci. 47 (1999) 1243 paper. Since Jupiter can provide important insight into the atmospheres of extrasolar giant planets (EGP), we also discuss here the possible implications of the first detection of an atmosphere on an EGP. The ammonia mixing ratio on Jupiter has now been determined directly from the Galileo probe mass spectrometer (GPMS) data, and its value relative to H2 (7.1±3.2)×10 -4 in the 9- 12 bar region, is found to be similar to the previously reported result inferred from the radio attenuation technique on Galileo. The Jovian 15N/ 14N ratio is found to be much lower than the terrestrial value at (2.3±0.3)×10 -3. A complete analysis of the various uncertainties in the GPMS data yields an H 2O mixing ratio of 6.0(+3.9,-2.8)×10 -4 at 19 bar in the hotspot, and a trend of increase with depth; all other mixing ratios and error bars remain unchanged. CH 3, previously detected on Saturn and Neptune, has now also been detected in the atmosphere of Jupiter recently by Cassini. Benzene is the heaviest hydrocarbon detected to date in the atmospheres of Jupiter and Saturn. Abundances inferred from Infrared Space Observatory measurements are 9(+4.5,-7.5)×10 14 and 4.7(+2.1,-1.1)×10 13 cm-2 for pressures less than 50 and 10 mbar on Jupiter and Saturn, respectively. Finally, we propose that the recently detected sodium in the atmosphere of the EGP orbiting HD 209458 may have mainly a post-accretionary extraplanetary origin, rather than being primordial.

Atreya, S. K.; Mahaffy, P. R.; Niemann, H. B.; Wong, M. H.; Owen, T. C.

2003-02-01

219

Effects of the Seasonal Cycle on Superrotation in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The dynamics of dry atmospheric general circulation model simulations forced by seasonally varying Newtonian relaxation are explored over a wide range of two control parameters and are compared with the large-scale circulation of Earth, Mars, and Titan in their relevant parameter regimes. Of the parameters that govern the behavior of the system, the thermal Rossby number (Ro) has previously been found to be important in governing the spontaneous transition from an Earth-like climatology of winds to a superrotating one with prograde equatorial winds, in the absence of a seasonal cycle. This case is somewhat unrealistic as it applies only if the planet has zero obliquity or if surface thermal inertia is very large. While Venus has nearly vanishing obliquity, Earth, Mars, and Titan (Saturn) all have obliquities of ~25° and varying degrees of seasonality due to their differing thermal inertias and orbital periods. Motivated by this, we introduce a time-dependent Newtonian cooling to drive a seasonal cycle using idealized model forcing, and we define a second control parameter that mimics non-dimensional thermal inertia of planetary surfaces. We then perform and analyze simulations across the parameter range bracketed by Earth-like and Titan-like regimes, assess the impact on the spontaneous transition to superrotation, and compare Earth, Mars, and Titan to the model simulations in the relevant parameter regime. We find that a large seasonal cycle (small thermal inertia) prevents model atmospheres with large thermal Rossby numbers from developing superrotation by the influences of (1) cross-equatorial momentum advection by the Hadley circulation and (2) hemispherically asymmetric zonal-mean zonal winds that suppress instabilities leading to equatorial momentum convergence. We also demonstrate that baroclinic instabilities must be sufficiently weak to allow superrotation to develop. In the relevant parameter regimes, our seasonal model simulations compare favorably to large-scale, seasonal phenomena observed on Earth and Mars. In the Titan-like regime the seasonal cycle in our model acts to prevent superrotation from developing, and it is necessary to increase the value of a third parameter—the atmospheric Newtonian cooling time—to achieve a superrotating climatology.

Mitchell, Jonathan L.; Vallis, Geoffrey K.; Potter, Samuel F.

2014-05-01

220

Spectral Irradiance Measurements of Simulated Lightning in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Optical emissions from lightning provide information to estimate the altitude, latitude and longitude of lightning storms, the energy of the discharges, and the production of important trace species such as HCN and C2H2. Knowledge of the spectra of planetary lightning is needed to deduce the total energy dissipated by lightning (and thereby, the production of trace gases) and to help design experiments to detect and track lightning storms. Measurements of the spectral irradiance from approximately 380 to 820 nm are reported for laboratory simulations of lightning in the atmospheres of Venus, Jupiter, and Titan. In our laboratory, laser-induced plasmas (LIP) are used to simulate lightning discharges. This technique avoids contamination of the spectra by elect-ode material and maintains a safe environment while allowing the use of flammable gases, such as hydrogen and methane, found in outer planet atmospheres. The observations were made at I and 5 bars pressure for Venus and Jupiter and at 1 bar for the Titan mixture. At a pressure of one bar, our results show prominent lines from H(sub alpha), H(sub beta), H(sub gamma), and H(sub delta) lines of the Balmer Series of atomic hydrogen, a single line from Helium at 588 nm and strong continuum radiation. At pressures of 5 bars, the H(sub alpha) and H(sub beta) lines are wider, the H(sub gamma), and H(sub delta) lines merge into the continuum because of pressure broadening, and the helium line at 588 nm is no longer visible. The observed spectra of simulated lightning in the venusian atmosphere at 1 and 5 bars shows that the OI multiplet at 777.7 nm dominates the spectra, but weak features due to atomic carbon and singly excited and singly ionized oxygen atoms are also visible. Although lightning has not yet been observed on Titan, it conceivable that some form of lightning discharge could be occurring. Therefore experiments on a Titan atmosphere mixture were conducted. The most prominent features seen in the simulated spectra are the H(sub alpha) at 656 nm. from the dissociation of the methane and two strong features at 740 and 820 nm from singly excited nitrogen atoms. Most of the features between 400 and 656 nm are due to ionized nitrogen atoms. A broad, highly structured feature centered near 389 nm is molecular band radiation from CN molecules formed in the cooling plasma of atomic nitrogen, carbon, and hydrogen. It is observed in the lightning simulations of both the venusian and Titan atmospheres, For Venus, Jupiter, and Titan, narrow spectral features that are ideal for detecting lightning in the presence of sunlight are present in the spectra. These features could allow lightning to be detected and tracked by Earth-based instruments.

Borucki, W. J.; McKay, C. P.; Jebbens, D.; Lakkaraju, H. S.; Vanajakshi, C. T.; Cuzzi, Jeffrey (Technical Monitor)

1996-01-01

221

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

222

Nonthermal atoms in planetary, satellite, and cometary atmospheres  

NASA Astrophysics Data System (ADS)

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

Kupperman, David Gerson

1999-08-01

223

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

224

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

225

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

Steffes, Paul G.

1997-01-01

226

Analytic theory of orbit contraction and ballistic entry into planetary atmospheres  

Microsoft Academic Search

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 dissipative force of drag through the dynamic phase of reentry and finally to the point of contact with the planetary surface. A complete uniformly valid theory is developed for orbit contraction due to atmospheric drag

J. M. Longuski

1979-01-01

227

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

NASA Astrophysics Data System (ADS)

Context. Planetary companions of a fixed mass induce reflex motions with a larger amplitude around lower-mass stars, which adds to making M dwarfs excellent targets for extra-solar planet searches. The most recent velocimeters with a stability of ~1 m s-1 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 of the known potentially habitable planets orbit one of these cool stars. Aims: Our M-dwarf radial velocity monitoring with HARPS on the ESO 3.6 m 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 ~five years: GJ 3293 (0.42 M?), GJ 3341 (0.47 M?), and GJ 3543 (0.45 M?). We extracted these RVs through minimum ?2-matching of each spectrum against a stack of all observed spectra for the same star that has a high signal-to-noise ratio. We then compared potential orbital signals against several stellar activity indicators to distinguish the Keplerian variations induced by planets from the spurious signals that result from rotational modulation of stellar surface inhomogeneities and from activity cycles. Results: Two Neptune-mass planets - msin(i) = 1.4 ± 0.1 and 1.3 ± 0.1Mnept - orbit GJ 3293 with periods P = 30.60 ± 0.02 d and P = 123.98 ± 0.38 d, possibly together with a super-Earth - msin(i) ~ 7.9 ± 1.4 M? - with period P = 48.14 ± 0.12d. A super-Earth - msin(i) ~ 6.1 M? - orbits GJ 3341 with P = 14.207 ± 0.007d. The RV variations of GJ 3543, on the other hand, reflect its stellar activity rather than planetary signals. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the program IDs 072.C-0488, 082.C-0718 and 183.C-0437 at Cerro La Silla (Chile).Tables A.1-A.3 (radial velocity data) are available in electronic form at http://www.aanda.org and at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A119

Astudillo-Defru, N.; Bonfils, X.; Delfosse, X.; Ségransan, 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.

2015-03-01

228

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

229

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

230

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

231

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

SciTech Connect

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

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

2011-09-01

232

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

233

Thermal escape from extrasolar giant planets.  

PubMed

The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres. PMID:24664923

Koskinen, Tommi T; Lavvas, Panayotis; Harris, Matthew J; Yelle, Roger V

2014-04-28

234

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

235

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

236

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

NASA Astrophysics Data System (ADS)

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 < 300 K. Modelling of these atmospheres has required the development of new techniques to deal with the molecular chemistry and clouds in these objects. The atmospheres of brown 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 characterisation 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 exoplanets are very dark, indicating a cloud free atmosphere. However, there is also good evidence for clouds and haze in some other planets. It is also well established that some highly irradiated planets have inflated radii, though the mechanism for this inflation is not yet clear. Some other issues in the composition and structure of giant exoplanet atmospheres such as the occurrence of inverted temperature structures, the presence or absence of CO2 and CH4, and the occurrence of high C/O ratios are still the subject of investigation and debate.

Bailey, Jeremy

2014-11-01

237

Laboratory studies of photochemistry and gas phase radical reaction kinetics relevant to planetary atmospheres.  

PubMed

This review seeks to bring together a selection of recent laboratory work on gas phase photochemistry, kinetics and reaction dynamics of radical species relevant to the understanding of planetary atmospheres other than that of Earth. A majority of work focuses on the rich organic chemistry associated with photochemically initiated reactions in the upper atmospheres of the giant planets. Reactions relevant to Titan, the largest moon of Saturn and with a nitrogen/methane dominated atmosphere, have also received much focus due to potential to explain the chemistry of Earth's prebiotic atmosphere. Analogies are drawn between the approaches of terrestrial and non-terrestrial atmospheric chemistry. PMID:22880207

Blitz, M A; Seakins, P W

2012-10-01

238

Microlensing Extrasolar Planets  

E-print Network

Microlensing Searches for Extrasolar Planets Microlensing Searches for Extrasolar Planets Microlensing Searches for Extrasolar Planets, B. Scott Gaudi, IAS Scientific Frontiers in Research on Extrasolar Planets, June 19, 2002 #12;Microlensing and PlanetsMicrolensing and Planets Microlensing Searches

Gaudi, B. Scott

239

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

240

Extrasolar Planet Science with the Antarctic Planet Interferometer  

E-print Network

Extrasolar Planet Science with the Antarctic Planet Interferometer James P. Lloyda, Ben F. Lanea. The unique properties of the polar atmosphere can be exploited for Extrasolar Planet studies on the properties of the atmosphere at the South Pole and other Antarctic plateau sites for Extrasolar Planet

Lloyd, James P.

241

On detecting biospheres from thermodynamic disequilibrium in planetary atmospheres  

E-print Network

Atmospheric chemical disequilibrium has been proposed as a method for detecting extraterrestrial biospheres from exoplanet observations. Chemical disequilibrium is potentially a generalized biosignature since it makes no assumptions about particular biogenic gases or metabolisms. Here, we present the first rigorous calculations of the thermodynamic chemical disequilibrium in the atmospheres of Solar System planets, in which we quantify the difference in Gibbs free energy of an observed atmosphere compared to that of all the atmospheric gases reacted to equilibrium. The purely gas phase disequilibrium in Earth's atmosphere, as measured by this available Gibbs free energy, is not unusual by Solar System standards and smaller than that of Mars. However, Earth's atmosphere is in contact with a surface ocean, which means that gases can react with water, and so a multiphase calculation that includes aqueous species is required. We find that the disequilibrium in Earth's atmosphere-ocean system (in joules per mole o...

Krissansen-Totton, Joshua; Catling, David C

2015-01-01

242

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

243

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. For example, laboratory measurements performed by Fahd and Steffes have shown that the opacity from gaseous SO2 under simulated Venus conditions can be well described by the Van Vleck-Weisskopf lineshape at wavelengths shortward of 2 cm, but that the opacity of wavelengths greater than 2 cm is best described by a different lineshape that was previously used in theoretical predictions. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Steffes, Paul G.

1992-01-01

244

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

245

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

246

Extrasolar Planets and 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

Charbonneau, David (California Institute of Technology) [California Institute of Technology

2002-04-24

247

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

248

Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b  

SciTech Connect

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

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

2011-03-21

249

Diversity of Planetary Atmospheric Circulations and Climates in a Simplified General Circulation Model  

NASA Astrophysics Data System (ADS)

The parametric dependence of terrestrial planetary atmospheric circulations and climates on characteristic parameters is studied. A simplified general circulation model-PUMA is employed to investigate the dynamic effects of planetary rotation rate and equator-to-pole temperature difference on the circulation and climate of terrestrial planetary atmospheres. Five different types of circulation regime are identified by mapping the experimental results in a 2-D parameter space defined by thermal Rossby number and frictional Taylor number. The effect of the transfer and redistribution of radiative energy is studied by building up a new two-band semi-gray radiative-convective scheme, which is capable of modelling greenhouse and anti-greenhouse effects while keeping the tunable parameters as few as possible. The results will provide insights into predicting the habitability of terrestrial exoplanets.

Wang, Yixiong; Read, Peter

2014-04-01

250

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 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

251

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

252

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 radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties taken under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, laboratory measurements completed recently by Kolodner and Steffes (ICARUS 132, pp. 151-169, March 1998, attached as Appendix A) under this grant (NAGS-4190), have shown that the opacity from gaseous H2SO4 under simulated Venus conditions is best described by a different formalism 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 spacecraft entry probe and orbiter radio occultation experiments and by radio astronomical observations, and over a range of frequencies which correspond to those used in such experiments, 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.

1998-01-01

253

Greenhouse effect in semi-transparent planetary atmospheres  

Microsoft Academic Search

In this work the theoretical relationship between the clear-sky outgoing infrared radiation and the surface upward radiative flux is explored by using a realistic finite semi-transparent atmospheric model. We show that the fundamental relationship between the optical depth and source function contains real boundary condition parameters. We also show that the radiative equilibrium is controlled by a special atmospheric transfer

Ferenc M. Miskolczi

2007-01-01

254

VUV photochemistry simulation of planetary upper atmosphere using synchrotron radiation.  

PubMed

The coupling of a gas reactor, named APSIS, with a vacuum-ultraviolet (VUV) beamline at the SOLEIL synchrotron radiation facility, for a photochemistry study of gas mixtures, is reported. The reactor may be irradiated windowless with gas pressures up to hundreds of millibar, and thus allows the effect of energetic photons below 100 nm wavelength to be studied on possibly dense media. This set-up is perfectly suited to atmospheric photochemistry investigations, as illustrated by a preliminary report of a simulation of the upper atmospheric photochemistry of Titan, the largest satellite of Saturn. Titan's atmosphere is mainly composed of molecular nitrogen and methane. Solar VUV irradiation with wavelengths no longer than 100 nm on the top of the atmosphere enables the dissociation and ionization of nitrogen, involving a nitrogen chemistry specific to nitrogen-rich upper atmospheres. PMID:23765300

Carrasco, Nathalie; Giuliani, Alexandre; Correia, Jean Jacques; Cernogora, Guy

2013-07-01

255

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

E-print Network

and ionospheres) are important to understanding planetary and atmospheric evolution Target Learning Objectives: 1. The configuration of the magnetic field helps to determine the structure of the ionosphere How do we communicate. Traveling presentations using the Magic Planet® digital video globe from Global Imagination® all images from

Fillingim, Matthew

256

A collisional kinetic theory of a plane parallel evaporating planetary atmosphere  

Microsoft Academic Search

The departure from equilibrium in the exosphere of a planetary atmosphere owing to the loss of energetic atoms is studied with solutions of the Boltzmann equation. A rigorous collisional solution is obtained for a plane parallel model with a newly developed discrete ordinate method, and the decrease in the excape flux relative to Jeans flux is calculated together with density

B. Shizgal; R. Blackmore

1986-01-01

257

NOTES AND CORRESPONDENCE Zonal Jets as Transport Barriers in Planetary Atmospheres  

E-print Network

section, passive tracer transport in a numerically simulated perturbed PV staircase flow is investigatedNOTES AND CORRESPONDENCE Zonal Jets as Transport Barriers in Planetary Atmospheres F. J. BERON The connection between transport barriers and potential vorticity (PV) barriers in PV-conserving flows

Olascoaga, Maria Josefina

258

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

259

Planetary Atmosphere Stability in the Habitable Zones of M-stars  

Microsoft Academic Search

The traditional habitable zone depends on conditions suitable for long term stability of liquid water on the surface of planets. It is suggested that the frequent intense stellar CME events could have led to so rapid erosion of planetary atmospheres that generally speaking there is essentially no habitable zones around Earth-mass planets around M-stars. However, fast atmosperic mass loss should

Feng Tian

2010-01-01

260

Effective depth of spectral line formation in planetary atmospheres  

NASA Technical Reports Server (NTRS)

The effective level of line formation for spectroscopic absorption lines has long been regarded as a useful parameter for determining average atmospheric values of the quantities involved in line formation. The identity of this parameter was recently disputed. The dependence of this parameter on the average depth where photons are absorbed in a semi-infinite atmosphere is established. It is shown that the mean depths derived by others are similar in nature and behavior.

Lestrade, J. P.; Chamberlain, J. W.

1980-01-01

261

Effective depth of spectral line formation in planetary atmospheres  

NASA Technical Reports Server (NTRS)

The effective level of line formation for spectroscopic absorption lines has long been regarded as a useful parameter for determining average atmospheric values of the quantities involved in line formation. The identity of this parameter has recently been disputed. This paper reestablishes the dependence of this parameter on the average depth at which photons are absorbed in a semi-infinite atmosphere and shows that the mean depths derived by others are similar in nature and behavior.

Lestrade, J. P.; Chamberlain, J. W.

1980-01-01

262

Planetary Atmosphere and Surfaces Chamber (PASC): A Platform to Address Various Challenges in Astrobiology  

NASA Astrophysics Data System (ADS)

The study of planetary environments of astrobiological interest has become a major challenge. Because of the obvious technical and economical limitations on in situ planetary exploration, laboratory simulations are one of the most feasible research options to make advances both in planetary science and in developing a consistent description of the origin of life. With this objective in mind, we applied vacuum technology to the design of versatile vacuum chambers devoted to the simulation of planetary atmospheres' conditions. These vacuum chambers are able to simulate atmospheres and surface temperatures representative of the majority of planetary objects, and they are especially appropriate for studying the physical, chemical and biological changes induced in a particular sample by in situ irradiation or physical parameters in a controlled environment. Vacuum chambers are a promising potential tool in several scientific and technological fields, such as engineering, chemistry, geology and biology. They also offer the possibility of discriminating between the effects of individual physical parameters and selected combinations thereof. The implementation of our vacuum chambers in combination with analytical techniques was specifically developed to make feasible the in situ physico-chemical characterization of samples. Many wide-ranging applications in astrobiology are detailed herein to provide an understanding of the potential and flexibility of these experimental systems. Instruments and engineering technology for space applications could take advantage of our environment-simulation chambers for sensor calibration. Our systems also provide the opportunity to gain a greater understanding of the chemical reactivity of molecules on surfaces under different environments, thereby leading to a greater understanding of interface processes in prebiotic chemical reactions and facilitating studies of UV photostability and photochemistry on surfaces. Furthermore, the stability and presence of certain minerals on planetary surfaces and the potential habitability of microorganisms under various planetary environmental conditions can be studied using our apparatus. Therefore, these simulation chambers can address multiple different challenging and multidisciplinary astrobiological studies.

Mateo-Marti, Eva

2014-08-01

263

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

SciTech Connect

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

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

2012-07-20

264

Wide-Band Heterodyne Submillimetre Wave Spectrometer for Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

We present calculations and measurements on a passive submillimetre wave spectroscopic sounder to gather data on the thermal structure, dynamics and composition of the upper atmosphere of a planet, e.g. the stratosphere of Jupiter, or the entire thickness of the atmosphere of Mars. The instrument will be capable of measuring wind speeds, temperature, pressure, and key constituent concentrations in the stratosphere of the target planet. This instrument consists of a Schottky diode based front end and a digital back-end spectrometer. It differs from previous space-based spectrometers in its combination of wide tunability (520-590 GHz), and rapid frequency switching between widely spaced lines within that range. This will enable near simultaneous observation of multiple lines, which is critical to the reconstruction of atmospheric pressure and density versus altitude profiles. At the same time frequency accuracy must be high to enable wind speeds to be determined directly by measurement of the line's Doppler shift.

Schlecht, Erich

2010-01-01

265

Atmospheric tides on Venus. III - The planetary boundary layer  

NASA Technical Reports Server (NTRS)

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.

1983-01-01

266

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

267

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

268

Planetary, Atmospheric, and Environmental Applications of Physics Frank Mills  

E-print Network

Multispectral and multiangle remote sensing of mineral dust aerosols Current Research Project Grants Analysis: Improvements in understanding Venus'atmospheric evolution Machine-learning-based forecasting of distributed solar energy production Evaluating, forecasting, and managing suburb-scale distributed solar electricity

Chen, Ying

269

Outer satellite atmospheres: Their nature and planetary interactions  

NASA Technical Reports Server (NTRS)

Modeling capabilities and initial model calculations are reported for the peculiar directional features of the Io sodium cloud discovered by Pilcher and the extended atomic oxygen atmosphere of Io discovered by Brown. Model results explaining the directional feature by a localized emission from the satellite are encouraging, but as yet, inconclusive; whereas for the oxygen cloud, an escape rate of 1 to 2 x 10 to the 27th power atoms/sec or higher from Io is suggested. Preliminary modeling efforts were also initiated for the extended hydrogen ring-atmosphere of Saturn detected by the Voyager spacecraft and for possible extended atmospheres of some of the smaller satellites located in the E-ring. Continuing research efforts reported for the Io sodium cloud include further refinement in the modeling of the east-west asymmetry data, the asymmetric line profile shape, and the intersection of the cloud with the Io plasma torus. In addition, the completed pre-Voyager modeling of Titan's hydrogen torus is included and the near completed model development for the extended atmosphere of comets is discussed.

Smyth, W. H.

1981-01-01

270

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

271

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

272

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

2005-06-17

273

Extrasolar Planetary Imaging Coronagraph (EPIC)  

NASA Technical Reports Server (NTRS)

EPIC is a NASA mission being studied to detect and characterize Jovian and superEarth planets, and, the dust/debris disks surrounding the parent star. It will be launched into a heliocentric Earth trailing orbit and operate for 5 years. EPIC would operate over the wavelength range of 480 - 960 nm with spectral resolutions of R < 50 and employs a visible nulling coronagraph (VNC) to suppress the starlight, yielding contrast ratios of greater than 9 orders of magnitude. We will discuss the science mission, and its role in the search for habitable planets.

Clampin, Mark

2009-01-01

274

Constraints on early atmosphere from planetary accretion processes  

NASA Technical Reports Server (NTRS)

Evidence for composition and dynamics of release of the earliest volatiles was in lack of anything better being sought from the most ancient sediments known at the time, although they were recognized to be younger than three billion years. Origin of life on Earth was considered to require a lasting atmosphere with hydrogen and methane as major components. The new observations together with theoretical studies generated by the space program and by systematic exploration of the Earth's oceanic crust changed the climate of opinion in which the questions of the primordial atmosphere are discussed. Even though existing evidence does not permit conclusive choice of any specific scenario, the acceptance of specific model elements now forces the consideration of a series of consequences, some of which may be tested by observation.

Arrhenius, G.

1985-01-01

275

Planetary Aeronomy. 2; NO2 In the Martian Atmosphere  

NASA Technical Reports Server (NTRS)

The transmission curve of the Martian atmosphere derived by Opik is compared with transmission curves of an atmosphere containing various amounts of nitrogen dioxide. It is found that the amount of 6 x l0(exp 18) sq cm column NO2 (or even less) given by Sinton as an upper limit for the Martian NO2 content could adequately explain the phenomenon of the blue haze. This finding made it worthwhile to investigate the effect of the temperature and pressure sensitive equilibrium 2 NO2 reversibly yields N204 upon the total NO2 content and the altitude-number density distributions of NO2 and N204. Computations were carried out for surface temperatures of 273 K, 243 K, 213 K, and 183 K and for three different temperature distributions. The discussion of the results leads to the suggestion of several important new experiments.

Warneck, P.; Marmo, F. F.

1963-01-01

276

Parameterized rotating convection for core and planetary atmosphere dynamics  

NASA Astrophysics Data System (ADS)

New types of convective instability and associated nonlinear phenomena in rapidly rotating spherical systems have been discovered through numerical simulations. The Prandtl number, defined as the ratio of the viscous and thermal diffusivities of a fluid, Pr = nu/kappa, plays a crucial role in determining the fundamental features of both the instabilities and the corresponding nonlinear convection. The results shed new light on regimes of convection in the earth's core and the atmospheres of the major planets.

Zhang, K.

1991-04-01

277

Use of planetary atmosphere for chemical and fusion propulsion flight  

Microsoft Academic Search

Feasibility study of cost-effective interplanetary transportation through reusable heavy-lift launch vehicles and Mars transfer vehicles is presented. Particular attention is given to the earth and Mars atmospheres as a major source of launch and transfer vehicle propellant for interplanetary travel. It is concluded that reusable airbreathing heavy-lift launch vehicles, based on emerging aerospace plane technologies, may eventually be feasible for

H. D. Froning Jr.; J. L. Leingang; F. B. Mead Jr.; S. N. B. Murthy

1992-01-01

278

A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres  

Microsoft Academic Search

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

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

2008-01-01

279

Remote sensing of the turbulence characteristics of a planetary atmosphere by radio occultation of a space probe.  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to analyze the effects of small-scale turbulence on radio waves propagating through a planetary atmosphere. The analysis provides a technique for inferring the turbulence characteristics of a planetary atmosphere from the radio signals received from a spacecraft as it is occulted by the planet. The planetary turbulence is assumed to be localized and smoothly varying, with the structure constant varying exponentially with altitude. Rytov's method is used to derive the variance of log-amplitude and phase fluctuations of a wave propagating through the atmosphere.

Woo, R.; Ishimaru, A.

1973-01-01

280

PHYSICS OF PLANETS: OBSERVING EXTRASOLAR GIANT PLANETS WITH Tristan Guillot  

E-print Network

1 PHYSICS OF PLANETS: OBSERVING EXTRASOLAR GIANT PLANETS WITH DARWIN/TPF Tristan Guillot/TPF. Extrasolar giant planets are milestones on the quest for our origins: they hold crucial information con for those objects with little or no atmosphere). On the other hand, extrasolar giant planets represent a new

Guillot, Tristan

281

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

282

Extrasolar planets  

Microsoft Academic Search

The discovery of the first extra-solar planet surrounding a main-sequence star was announced in 1995, based on very precise radial velocity (Doppler) measurements. A total of 34 such planets were known by the end of March 2000, and their numbers are growing steadily. The newly discovered systems confirm some of the features predicted by standard theories of star and planet

M. A. C. Perryman

2000-01-01

283

Spectrophotometry of planetary atmosphere from the X-15 rocket airplane  

NASA Technical Reports Server (NTRS)

Nike-Apache and Nike-Tomahawk rocket flights using spectrophotometric techniques to investigate auroral activity are reported. The specific objectives were to obtain data relative to typical auroral situations, including quiet pre-breakup auroras, westward traveling surges, breakup auroras, and post-breakup auroras. It was found that excited atoms move considerable distances between excitation and emission owing to the high velocity wind conditions prevailing above 200 km. Based on the results of these observations, recommendations are made for future studies of ionized atmospheric activity at higher altitudes.

Murcray, W. B.

1973-01-01

284

ON THE PERIOD DISTRIBUTION OF CLOSE-IN EXTRASOLAR GIANT PLANETS B. Scott Gaudi,1  

E-print Network

ON THE PERIOD DISTRIBUTION OF CLOSE-IN EXTRASOLAR GIANT PLANETS B. Scott Gaudi,1 S. Seager,2) surveys for extrasolar planets have recently uncovered a population of ``very hot Jupiters,'' planets properties of extrasolar planets. This information, in turn, provides clues to the nature of planetary

Gaudi, B. Scott

285

Grain opacity and the bulk composition of extrasolar planets. II. An analytical model for grain opacity in protoplanetary atmospheres  

NASA Astrophysics Data System (ADS)

Context. We investigate the grain opacity ?gr in the atmosphere (outer radiative zone) of forming planets. This is important for the observed planetary mass-radius relationship since ?gr affects the primordial H/He envelope mass of low-mass planets and the critical core mass of giant planets. Aims: The goal of this study is to derive a simple analytical model for ?gr and to explore its implications for the atmospheric structure and resulting gas accretion rate. Methods: Our model is based on the comparison of the timescales of the most important microphysical processes. We consider grain settling in the Stokes and Epstein drag regime, growth by Brownian motion coagulation and differential settling, grain evaporation in hot layers, and grain advection due to the contraction of the envelope. With these timescales and the assumption of a radially constant grain flux, we derive the typical grain size, abundance, and opacity. Results: We find that the dominating growth process is differential settling. In this regime, ?gr has a simple functional form; it is given as 27Q/ 8H? in the Epstein regime in the outer atmosphere and as 2Q/H? for Stokes drag in the deeper layers. Grain growth leads to a typical radial structure of ?gr with high ISM-like values in the outer layers but a strong decrease towards the deeper parts where ?gr becomes so low that the grain-free molecular opacities take over. Conclusions: In agreement with earlier results, we find that ?gr is typically much lower than in the ISM. In retrospect, this suggests that classical giant planet formation models should have considered the grain-free case to be as equally meaningful as the full ISM opacity case. The equations also show that a higher dust input in the top layers does not strongly increase ?gr. This has two important implications. First, for the formation of giant planet cores via pebbles, there could be the adverse effect that pebbles tend to increase the grain input high in the atmosphere because of ablation. This could in principle increase the opacity, making giant planet formation difficult. Our study indicates that this potentially adverse effect is not important. Second, it means that a higher stellar [Fe/H] which presumably leads to a higher surface density of planetesimals only favors giant planet formation without being detrimental to it because of an increased ?gr. This corroborates the result that core accretion can explain the observed increase of the giant planet frequency with stellar [Fe/H]. Appendices are available in electronic form at http://www.aanda.org

Mordasini, C.

2014-12-01

286

Resolving Sub-Fresnel-Scale Atmospheric Structure and Diffracting Limbs in Planetary Radio Occultation  

NASA Astrophysics Data System (ADS)

indent=0.25in The resolution of atmospheric profiles retrieved from radio occultation is often limited by diffractive blurring. Based on the laws of geometrical optics, the Abel inversion used to generate atmospheric profiles cannot typically resolve sub-Fresnel-scale structure nor compensate for diffraction from planetary limbs. In this research, these diffractive effects have been investigated in forward simulations of radio occultation. To achieve better vertical resolution, a multiple phase screen (MPS) approach has been implemented to manipulate the angular spectrum of forward-simulated data, effectively reducing the Fresnel zone size [Karayel, E. T. and D. P. Hinson, Sub-Fresnel-scale vertical resolution in atmospheric profiles from radio occultation, Radio Sci., 32(2), 411-423, 1997]. Consequently, small atmospheric structure can be more accurately reconstructed than by using Abel inversion alone. In simulation, this technique was able to resolve a smooth, 40 m refractivity perturbation of magnitude 10-7 superposed over the refractivity profile for a Mars-like atmosphere. The simulated atmosphere had a refractivity of ~4\\times 10-6 and a scale height of approximately 9 km. The Fresnel scale in this simulation was approximately 250 m. Using a variation of the same MPS technique, models for diffraction from planetary limbs have been explored in order to better understand the limb diffraction seen in occultation data from satellites (e.g., Mars Global Surveyor) as well as its effect in atmospheric profile retrieval. Such occultation data contain clear indications of diffraction from the planetary limb, having oscillations with spatial frequencies corresponding to the Fresnel scale. Consequently, this investigation attempts to model limb diffraction as the result of single and multiple, non-parallel knife-edges and incorporate it into the method for profile retrieval.

Han, C.; Tyler, G. L.; Hinson, D. P.

2001-12-01

287

Grain opacity and the bulk composition of extrasolar planets. II. An analytical model for the grain opacity in protoplanetary atmospheres  

E-print Network

Context. We investigate the grain opacity k_gr in the atmosphere of protoplanets. This is important for the planetary mass-radius relation since k_gr affects the H/He envelope mass of low-mass planets and the critical core mass of giant planets. Aims. The goal of this study is to derive an analytical model for k_gr. Methods. Our model is based on the comparison of the timescales of microphysical processes like grain settling in the Stokes and Epstein regime, growth by Brownian motion coagulation and differential settling, grain evaporation, and grain advection due to envelope contraction. With these timescales we derive the grain size, abundance, and opacity. Results. We find that the main growth process is differential settling. In this regime, k_gr has a simple functional form and is given as 27 Q/8 H rho in the Epstein regime and as 2 Q/H rho for Stokes drag. Grain dynamics lead to a typical radial structure of k_gr with high ISM-like values in the top layers but a strong decrease in the deeper parts where...

Mordasini, C

2014-01-01

288

Microlensing Search for Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Microlensing has recently proven to be a valuable tool to search for extrasolar planets of Neptune- to super-Earth-mass planets at orbits of few AU. Since planetary signals are of very short duration, an intense and continuous monitoring is required, which is achieved PLANET : ``Probing Lensing Anomalies NETwork''. Up to now the detection number amounts to four, one of them being OGLE~2005-BLG-390Lb, an extrasolar planet of only ˜5.5 M_? orbiting its M-dwarf host star at ˜2.6 AU. For non-planetary microlensing events observed from 1995 to 2006, we compute detection efficiency diagrams which can then be used to derive an estimate of the limit on the Galactic abundance of sub-Jupiter-mass planets, as well as relative abundance of Neptune-like planets.

Cassan, A.; Kubas, D.

2007-07-01

289

Microlensing search for extrasolar planets  

E-print Network

Microlensing has recently proven to be a valuable tool to search for extrasolar planets of Neptune- to super-Earth-mass planets at orbits of few AU. Since planetary signals are of very short duration, an intense and continuous monitoring is required, which is achieved by PLANET : ``Probing Lensing Anomalies NETwork''. Up to now the detection number amounts to four, one of them being OGLE 2005-BLG-390Lb, an extrasolar planet of only ~5.5 M_earth orbiting its M-dwarf host star at ~2.6 AU. For non-planetary microlensing events observed from 1995 to 2006, we compute detection efficiency diagrams which can then be used to derive an estimate of the limit on the Galactic abundance of sub-Jupiter-mass planets, as well as relative abundance of Neptune-like planets.

A. Cassan; D. Kubas

2006-12-01

290

A smoothing technique for improving atmospheric reconstruction for planetary entry probes  

NASA Astrophysics Data System (ADS)

Accelerometer instruments are commonly used on planetary entry probes to determine vertical profiles of atmospheric density, pressure, and temperature. A key consideration for the design and implementation of such investigations is extending the atmospheric results to the highest altitudes possible, which requires minimizing uncertainties in measured accelerations whilst maintaining adequate vertical resolution. Since atmospheric density depends exponentially on altitude, the arithmetic mean of a subset of raw acceleration data points is a biased estimate of the true acceleration at the center of the time interval in question. This diminishes the quality of derived atmospheric properties. Here we show how this problem can be alleviated by using a specialized averaging technique that takes advantage of the inherent exponential variation in acceleration with time at atmospheric entry. This technique is demonstrated successfully on Mars Phoenix data.

Withers, Paul

2013-05-01

291

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

292

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

293

Spectropolarimetric signatures of Earth-like extrasolar planets  

E-print Network

We present results of numerical simulations of the flux (irradiance), F, and the degree of polarization (i.e. the ratio of polarized to total flux), P, of light that is reflected by Earth-like extrasolar planets orbiting solar-type stars, as functions of the wavelength (from 0.3 to 1.0 micron, with 0.001 micron spectral resolution) and as functions of the planetary phase angle. We use different surface coverages for our model planets, including vegetation and a Fresnel reflecting ocean, and clear and cloudy atmospheres. Our adding-doubling radiative transfer algorithm, which fully includes multiple scattering and polarization, handles horizontally homogeneous planets only; we simulate fluxes and polarization of horizontally inhomogeneous planets by weighting results for homogeneous planets. Like the flux, F, the degree of polarization, P, of the reflected starlight is shown to depend strongly on the phase angle, on the composition and structure of the planetary atmosphere, on the reflective properties of the underlying surface, and on the wavelength, in particular in wavelength regions with gaseous absorption bands. The sensitivity of P to a planet's physical properties appears to be different than that of F. Combining flux with polarization observations thus makes for a strong tool for characterizing extrasolar planets. The calculated total and polarized fluxes will be made available through the CDS.

D. M. Stam

2007-07-26

294

Dissociative recombination in reactive flows related to planetary atmospheric entries  

NASA Astrophysics Data System (ADS)

The Dissociative Recombination (DR) processes play a significant role in plasma chemistry. This article illustrates this role from the modeling point of view in the case of reactive flows related to atmospheric entry plasmas. Two situations are investigated, for which the studied plasma is nitrogen. The first configuration corresponds to the relaxation process behind a strong shock wave moving at high Mach number in a shock tube, the second one to the recombination taking place in an expanding plasma flowing in a diverging nozzle. In both cases, the collisional-radiative model CoRaM-N2, involving N2, N, N2+, N+ and electrons, is implemented in an Eulerian 1D code able to compute the aerodynamic fields; calculations are performed in standard conditions. We show that, according to the rate coefficients used for the DR processes, the population density of the charged species especially N2+ is strongly modified only for the post-shock flow.

Bultel, Arnaud; Annaloro, Julien; Druguet, Marie-Claude

2015-01-01

295

Outer satellite atmospheres: Their extended nature and planetary interactions  

NASA Technical Reports Server (NTRS)

Model calculations for the brightness of the sodium cloud in Region A were performed to clarify the role played by the plasma torus sink in producing the east-west intensity asymmetry observed in the sodium D-lines. It was determined that the east-west electric field, proposed by Barbosa and Kievelson (1983) and Ip and Goertz (1983) to explain the dawn-dusk asymmetry in the torus ion emissions measured by the Voyager UVS instrument, could also produce the east-west sodium intensity asymmetry discovered earlier by Bergstralh et al. (1975, 1977). Model results for the directional features of the sodium cloud are also reported. The completion of the development of the Io potassium cloud model, progress in improving the Titan hydrogen torus model, and efforts in developing our model for hydrogen cometary atmospheres are also discussed.

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

1984-01-01

296

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

297

Intensity measurements in the nu4-fundamental of (C-13)H4 at planetary atmospheric temperatures  

NASA Technical Reports Server (NTRS)

Measurements of spectral transmittance have been performed in the nu4-fundamental band of (C-13)H4 at low temperatures of planetary atmospheric interest with spectral resolution of 0.06 per cm. Comparison of observed and computed spectral transmittance on a line-by-line basis has yielded line strengths. Best agreement between measured and computed spectra was obtained when the absolute intensity of the band was taken as 123 per (sq cm atm) at 296 K.

Varanasi, P.; Giver, L. P.; Valero, F. P. J.

1983-01-01

298

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

299

Conjecture on superrotation in planetary atmospheres - A diffusion model with mixing length theory  

NASA Technical Reports Server (NTRS)

The component of rigid shell superrotation on Venus is discussed in the context of comparative planetary atmospheres. A simplified, heuristic analysis, utilizing mixed length theory to describe the small scale nonlinear advections of energy and angular momentum, thereby providing a closure of the dynamic system, is presented, on the basis of which a crude estimate of zonal velocity is made. The rigid shell (global average) component on Venus was calculated to be 105 m/sec.

Mayr, H. G.; Harris, I.; Hartle, R. E.; Schatten, K. H.; Chan, K. L.

1985-01-01

300

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

Microsoft Academic Search

For the purpose of investigating the photon energy dependence of the photoinduced abiotic synthesis of organic molecules, gas mixtures that simulate typical planetary atmospheres, including a carbon source (CO or CH4), a nitrogen source (N2 or NH3), and H2O, were irradiated with synchrotron radiation through a vacuum-ultraviolet transmitting window. Three kinds of window material, fused silica, synthetic quartz, and MgF2,

Jun-Ichi Takahashi; Hitomi Masuda; Takeo Kaneko; Kensei Kobayashi; Takeshi Saito; Teruo Hosokawa

2005-01-01

301

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

PubMed

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

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

2005-10-01

302

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

303

How do Atmospheres Affect Planetary Temperatures? Activity B How do Atmospheres Produce their Effect Upon Surface Temperatures?  

NSDL National Science Digital Library

In this kinesthetic activity, the concept of energy budget is strengthened as students conduct three simulations using play money as units of energy, and students serve as parts of a planetary radiation balance model. Students will determine the energy budget of a planet by manipulating gas concentrations, energy inputs and outputs in the system in this lesson that supports the study of climate on Mars, Mercury, Venus and Earth. The lesson supports understanding of the real-world problem of contemporary climate change. The resource includes a teacher's guide and several student worksheets. This is the second of four activities in the lesson, How do Atmospheres affect planetary temperatures?, within Earth Climate Course: What Determines a Planet's Climate? The resource 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.

304

On the Indirect Detection of Sodium in the Atmosphere of the Planetary Companion to HD 209458  

E-print Network

We construct a new model of the atmosphere of the transiting extrasolar giant planet HD 209458b to investigate the disparity between the observed strength of the sodium absorption feature at 589 nm and the predictions of previous models. Using a sodium ionization model that includes photoionization by stellar UV flux and radiative recombination, we show that the ionization depth in the planet's atmosphere,a function of angle from the planet's substellar point, can reach a pressure greater than 1 mbar at the day/night terminator. Ionization leads to a significant weakening of the sodium feature. Silicate and iron clouds reside at a pressure of several mbar, and their opacity increases absorption in bands directly adjacent to the sodium line core. Including ionization and clouds, we obtain a feature just at the upper limit of the observational error bars. Based on studies of sodium in the Earth's atmosphere, we argue that the amount of ionization could be greater than our model predicts.

Fortney, J J; Hubbard, W B; Burrows, A; Lunine, J I; Cooper, C S

2003-01-01

305

Some peculiarities of the upper atmosphere planetary scale motions in the Caucasus region  

NASA Astrophysics Data System (ADS)

The presence of variations characteristic for planetary scale motion in the Earth's upper atmosphere is shown in the intensities of the nightglow mesopause hydroxyl OH(8-3) band, the lower thermosphere oxygen green OI 557.7nm line and the ionosphere F2 region red OI 630.0 nm line, observed from Abastumani(41.75N, 42.82E). It is demonstrated that the simultaneous observations of the mentioned intensities are characterized by vertical propagation of 4-8 hour tidal motions, which is considered as the manifestation of the lower and upper atmosphere-ionosphere dynamical coupling in the Caucasus region.

Gudadze, Nikoloz; Javakhishvili, Giorgi; Didebulidze, Goderdzi

2014-12-01

306

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

307

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

308

Undergraduate Atmospheric  

E-print Network

-Exploration Planetary Science-Observation Minor Programs Earth, Atmospheric, and Planetary Sciences AstronomyUndergraduate Handbook Earth, Atmospheric and Planetary Sciences #12;EAPS Undergraduate Program, atmospheric science, oceanography, climate, planetary science, and astronomy. The Department's flexible

Rothman, Daniel

309

Analyses of Planetary Atmospheres Across the Spectrum: From Titan to Exoplanets  

NASA Astrophysics Data System (ADS)

Planetary atmospheres exist in a seemingly endless variety of physical and chemical environments. There are an equally diverse number of methods by which we can study and characterize atmospheric composition. In order to better understand the fundamental chemistry and physical processes underlying all planetary atmospheres, my research of the past four years has focused on two distinct topics. First, I focused on the data analysis and spectral retrieval of observations obtained by the Ultraviolet Imaging Spectrograph (UVIS) instrument onboard the Cassini spacecraft while in orbit around Saturn. These observations consisted of stellar occultation measurements of Titan's upper atmosphere, probing the chemical composition in the region 300 to 1500 km above Titan's surface. I examined the relative abundances of Titan's two most prevalent chemical species, nitrogen and methane. I also focused on the aerosols that are formed through chemistry involving these two major species, and determined the vertical profiles of aerosol particles as a function of time and latitude. Moving beyond our own solar system, my second topic of investigation involved analysis of infra-red light curves from the Spitzer space telescope, obtained as it measured the light from stars hosting planets of their own. I focused on both transit and eclipse modeling during Spitzer data reduction and analysis. In my initial work, I utilized the data to search for transits of planets a few Earth masses in size. In more recent research, I analyzed secondary eclipses of three exoplanets and constrained the range of possible temperatures and compositions of their atmospheres.

Kammer, Joshua A.

310

Variability of solar/stellar activity and magnetic field and its influence on planetary atmosphere evolution  

NASA Astrophysics Data System (ADS)

It is shown that the evolution of planetary atmospheres can only be understood if one recognizes the fact that the radiation and particle environment of the Sun or a planet's host star were not always on the same level as at present. New insights and the latest observations and research regarding the evolution of the solar radiation, plasma environment and solar/stellar magnetic field derived from the observations of solar proxies with different ages will be given. We show that the extreme radiation and plasma environments of the young Sun/stars have important implications for the evolution of planetary atmospheres and may be responsible for the fact that planets with low gravity like early Mars most likely never build up a dense atmosphere during the first few 100 Myr after their origin. Finally we present an innovative new idea on how hydrogen clouds and energetic neutral atom (ENA) observations around transiting Earth-like exoplanets by space observatories such as the WSO-UV, can be used for validating the addressed atmospheric evolution studies. Such observations would enhance our understanding on the impact on the activity of the young Sun on the early atmospheres of Venus, Earth, Mars and other Solar System bodies as well as exoplanets.

Lammer, Helmut; Güdel, Manuel; Kulikov, Yuri; Ribas, Ignasi; Zaqarashvili, Teimuraz V.; Khodachenko, Maxim L.; Kislyakova, Kristina G.; Gröller, Hannes; Odert, Petra; Leitzinger, Martin; Fichtinger, Bibiana; Krauss, Sandro; Hausleitner, Walter; Holmström, Mats; Sanz-Forcada, Jorge; Lichtenegger, Herbert I. M.; Hanslmeier, Arnold; Shematovich, Valery I.; Bisikalo, Dmitry; Rauer, Heike; Fridlund, Malcolm

2012-02-01

311

A Decade of Extrasolar Planets around Normal Stars  

NASA Astrophysics Data System (ADS)

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

Livio, Mario; Sahu, Kailash; Valenti, Jeff

2008-06-01

312

A Decade of Extrasolar Planets around Normal Stars  

NASA Astrophysics Data System (ADS)

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

Livio, Mario; Sahu, Kailash; Valenti, Jeff

2011-04-01

313

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

314

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

315

Lunar and Planetary Science XXXV: Origin of Planetary Systems  

NASA Technical Reports Server (NTRS)

The session titled Origin of Planetary Systems" included the following reports:Convective Cooling of Protoplanetary Disks and Rapid Giant Planet Formation; When Push Comes to Shove: Gap-opening, Disk Clearing and the In Situ Formation of Giant Planets; Late Injection of Radionuclides into Solar Nebula Analogs in Orion; Growth of Dust Particles and Accumulation of Centimeter-sized Objects in the Vicinity of a Pressure enhanced Region of a Solar Nebula; Fast, Repeatable Clumping of Solid Particles in Microgravity ; Chondrule Formation by Current Sheets in Protoplanetary Disks; Radial Migration of Phyllosilicates in the Solar Nebula; Accretion of the Outer Planets: Oligarchy or Monarchy?; Resonant Capture of Irregular Satellites by a Protoplanet ; On the Final Mass of Giant Planets ; Predicting the Atmospheric Composition of Extrasolar Giant Planets; Overturn of Unstably Stratified Fluids: Implications for the Early Evolution of Planetary Mantles; and The Evolution of an Impact-generated Partially-vaporized Circumplanetary Disk.

2004-01-01

316

50&100YEARSAGO EXTRASOLAR PLANETS  

E-print Network

the discovery of fluorescent emission from methane in the upper atmosphere of a nearby, Jupiter-mass extrasolar planet6 , HD 189733b (Fig. 1). Fluorescence occurs when an atom or mol- ecule absorbs a photon

Royer, Dana

317

MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions  

NASA Astrophysics Data System (ADS)

The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

2015-04-01

318

Studies of satellite and planetary surfaces and atmospheres. [Jupiter, Saturn, and Mars and their satellites  

NASA Technical Reports Server (NTRS)

Completed or published research supported by NASA is summarized. Topics cover limb darkening and the structure of the Jovian atmosphere; the application of generalized inverse theory to the recovery of temperature profiles; models for the reflection spectrum of Jupiter's North Equatorial Belt; isotropic scattering layer models for the red chromosphore on Titan; radiative-convective equilibrium models of the Titan atmosphere; temperature structure and emergent flux of the Jovian planets; occultation of epsilon Geminorum by Mars and the structure and extinction of the Martian upper atmosphere; lunar occultation of Saturn; astrometric results and the normal reflectances of Rhea, Titan, and Iapetus; near limb darkening of solids of planetary interest; scattering light scattering from particulate surfaces; comparing the surface of 10 to laboratory samples; and matching the spectrum of 10: variations in the photometric properties of sulfur-containing mixtures.

Sagan, C.

1978-01-01

319

The influence of line shape and band structure on temperatures in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Numerical experiments are performed to examine the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres. In order to accurately determine these effects, a method for calculating radiative terms is developed which avoids the usual approximations. It differs from the more commonly used methods in that it allows arbitrary dependence of the absorption coefficient on wave number, without requiring tedious line by line integration and without the constraints of band models. The present formulation is restricted to homogeneous atmospheres but the concept can be extended to the more general case. The numerical experiments reveal that the line shape and band structure of the absorbing gases have a large effect on temperatures in the higher layers of the atmosphere (corresponding to the stratosphere and mesosphere). The more nongrey the spectrum (that is, the higher the peaks and the deeper the troughs in the spectrum), the lower the temperature.

Arking, A.; Grossman, K.

1972-01-01

320

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

321

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

322

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

323

Extrasolar Visions  

NSDL National Science Digital Library

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

324

Planetary atmosphere evolution: do other habitable planets exist and can we detect them?  

NASA Technical Reports Server (NTRS)

The goal of this conference is to consider whether it is possible within the next few decades to detect Earth-like planets around other stars using telescopes or interferometers on the ground or in space. Implicit in the term "Earth-like" is the idea that such planets might be habitable by Earth-like organisms, or that they might actually be inhabited. Here, I shall address two questions from the standpoint of planetary atmosphere evolution. First, what are the chances that habitable planets exist around other stars? And, second, if inhabited planets exist, what would be the best way to detect them?.

Kasting, J. F.

1996-01-01

325

Atmospheric Characterization of Jupiter Using a Planetary Radiation Transport Model On MODTRAN® 5  

NASA Astrophysics Data System (ADS)

At last year's AMOS conference we described the application of a version of MODTRAN® for radiative transfer in planetary atmospheres to Saturn. The initial application was to Neptune. We have demonstrated good agreement with remotely obtained spectral data from the near UV through the far IR for both planets. This year, we describe upgrades to the model and demonstrate its application to Jupiter and Titan. Comparisons will be made to spectra from many different sources, including, for example, the Cassini-Huygens probe that landed on Titan. Some of the model upgrades include extending the spectral data bases to higher temperatures and adding new aerosol and haze models.

Fox, M.; Berk, A.; Bernstein, L.

326

Planetary atmosphere evolution: do other habitable planets exist and can we detect them?  

PubMed

The goal of this conference is to consider whether it is possible within the next few decades to detect Earth-like planets around other stars using telescopes or interferometers on the ground or in space. Implicit in the term "Earth-like" is the idea that such planets might be habitable by Earth-like organisms, or that they might actually be inhabited. Here, I shall address two questions from the standpoint of planetary atmosphere evolution. First, what are the chances that habitable planets exist around other stars? And, second, if inhabited planets exist, what would be the best way to detect them? PMID:11542303

Kasting, J F

1996-01-01

327

GRAVITY WAVES ON HOT EXTRASOLAR PLANETS. I. PROPAGATION AND INTERACTION WITH THE BACKGROUND  

SciTech Connect

We study the effects of gravity waves, or g-modes, on hot extrasolar planets. These planets are expected to possess stably stratified atmospheres, which support gravity waves. In this paper, we review the derivation of the equation that governs the linear dynamics of gravity waves and describe its application to a hot extrasolar planet, using HD 209458 b as a generic example. We find that gravity waves can exhibit a wide range of behaviors, even for a single atmospheric profile. The waves can significantly accelerate or decelerate the background mean flow, depending on the difference between the wave phase and mean flow speeds. In addition, the waves can provide significant heating ({approx}10{sup 2} to {approx}10{sup 3} K per planetary rotation), especially to the region of the atmosphere above about 10 scale heights from the excitation region. Furthermore, by propagating horizontally, gravity waves provide a mechanism for transporting momentum and heat from the dayside of a tidally locked planet to its nightside. We discuss work that needs to be undertaken to incorporate these effects in current atmosphere models of extrasolar planets.

Watkins, Chris [Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom); Cho, J. Y-K., E-mail: c.watkins@qmul.ac.u, E-mail: J.Cho@qmul.ac.u [Visiting Scientist, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States)

2010-05-01

328

Infrared Transmission Spectra for Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

Among the hot Jupiters known to date that transit their parent stars, the two best candidates to be observed with transmission spectroscopy in the mid-infrared (MIR) are HD 189733b and HD 209458b, due to their combined characteristics of planetary density, orbital parameters, and parent star distance and brightness. Here we simulate transmission spectra of these two planets during their primary transit in the MIR, and we present sensitivity studies of the spectra to the changes of atmospheric thermal properties, molecular abundances, and C/O ratios. Our model predicts that the dominant species absorbing in the MIR on hot Jupiters are water vapor and carbon monoxide, and their relative abundances are determined by the C/O ratio. Since the temperature profile plays a secondary role in the transmission spectra of hot Jupiters compared to molecular abundances, future primary transit observations in the MIR of those objects might offer insight on extrasolar giant planet atmospheric chemistry. We find here that the absorption features caused by water vapor and carbon monoxide in a cloud-free atmosphere are deep enough to be observable by the present and future generation of space-based observatories, such as Spitzer Space Telescope and James Webb Space Telescope. We discuss our results in light of the capabilities of these telescopes.

Tinetti, Giovanna; Liang, Mao-Chang; Vidal-Madjar, Alfred; Ehrenreich, David; Lecavelier des Etangs, Alain; Yung, Yuk L.

2007-01-01

329

Laboratory studies at high resolution of the infrared absorption spectra of a number of gases found in planetary atmospheres  

NASA Technical Reports Server (NTRS)

The infrared absorption spectra of a number of gases found in planetary atmospheres were studied at high resolution. Absorption line measurements which can be of value for the interpretation of planetary spectra in terms of molecular abundances and conditions in the planetary atmospheres were provided. The high resolution spectra have yielded measurements of individual vibration rotation line parameters including positions, strengths, pressure broadened widths and, where assignments were unknown, the temperature sensitivity of the strengths. Such information allows the determinations of the absorption of a given molecular gas under planetary conditions of temperature and pressure and at the same time it provides the data necessary if the spectra are to be understood in terms of basic molecular theory. Thus this work has included spectral analysis in the form of line assignments as well as fitting of the data to Hamiltonian models. Such fitting is very useful in that it helps to confirm and extend the assignments.

Hunt, R. H.

1983-01-01

330

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

331

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

332

Atmospheric planetary boundary layers: nature, theory, modelling and role in PEEX  

NASA Astrophysics Data System (ADS)

Atmospheric planetary boundary layers (PBLs) control turbulent exchange processes linking the atmosphere with underlying land, vegetation, urban-canopy or water surfaces. The key PBL parameters are vertical turbulent fluxes of energy, matter (pollutants, greenhouse gases, aerosol particles, etc.) and momentum at the PBL lower and upper boundaries, and the PBL height. This paper presents recent advancements in our understanding the nature of PBL and calculation of the above PBL parameters for the newly discovered PBL types, namely, conventionally-neutral and long-lived stable PBLs, and accounting for large-scale self-organised structures in convective PBLs (cells and rolls in the shear-free and sheared convection, respectively). The emphasis is put on the PBL processes determining local features of weather, climate, and air quality, such as extreme weather events, heavy air-pollution episodes and local consequences of global warming.

Zilitinkevich, Sergej

2014-05-01

333

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

334

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

335

Microlensing Searches for Extrasolar Planets  

E-print Network

Microlensing Searches for Extrasolar Planets Microlensing Searches for Extrasolar Planets I for Extrasolar Planets, B. Scott Gaudi, IAS #12;The Search for Extrasolar PlanetsThe Search for Extrasolar Planets Why Search for Extrasolar Planets ? Frequency of Life Clues to Star Formation Low End

Gaudi, B. Scott

336

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.

337

Interactives: Comets, Orbital Motions, and Virtual Ballooning to Explore Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

We will demonstrate interactives and animations from the Windows to the Universe web site (www.windows.ucar.edu) covering three topics: cometary orbits and tails, orbit shapes and orbital motions, and virtual ballooning to explore planetary atmospheres. The comet interactive illustrates the range of shapes and sizes of cometary orbits, the formation of tails when a comet nears the Sun, and the orientations of the dust and ion tails. Our suite of animations and interactives about orbits and orbital motions help learners understand the shapes (eccentricity) and sizes (semi-major axis) of orbits as well as variations in orbital velocity from perihelion to aphelion. Our Mars orbit interactive illustrates the variations in distance between Earth and Mars as the planets orbit and at successive oppositions (closest approaches), which has influenced the history of both telescopic observations of the Red Planet as well as the timing of space missions to Mars. The virtual ballooning interactive enables students to explore the structures of atmospheres by launching virtual weather balloons that send back data on the variation of pressure and temperature with altitude. Learners set the altitude ranges and sampling frequencies for their balloon-borne virtual instruments and collect data over the course of four flights. Students learn about the pressure variation with altitude, temperature vs. altitude relationships in different atmospheric layers, and how to be thoughtful and selective during experimental data collection. Students can explore the atmospheres of Mars, Venus, and Titan as well as Earth.

Russell, R. M.; Johnson, R. M.; Genyuk, J.

2009-12-01

338

Scintillations during occultations by planets. I - An approximate theory. [for planetary atmosphere structure  

NASA Technical Reports Server (NTRS)

Fluctuations are observed during occultations of both stars and spacecraft by planetary atmospheres. Existing treatments of spacecraft scintillations ignore a major effect unique to occultations: the severe flattening of the Fresnel zone or source image by defocusing. Other large effects, due to 'saturation' of the scintillation, have also been ignored. The deeper portions of atmospheric temperature and density profiles inferred from occultation data are seriously in error if other planets' atmospheres are as turbulent as our own. Thus, profiles obtained from entry probes (e.g., the Soviet Venera series) are probably more accurate than those from radio occultation (Mariner 5 and 10) data. Scintillation greatly reduces the information obtainable from occultation observations; much of the detail attributed to layering in published profiles is probably due to aliasing of turbulence. This paper gives an approximately correct theoretical treatment that is a substantial improvement over published theories, and shows how a more accurate theory could be constructed. Some methods for a more accurate determination of atmospheric structure are proposed.

Young, A. T.

1976-01-01

339

Scientific Value of a Saturn Atmospheric Probe Mission  

NASA Technical Reports Server (NTRS)

Atmospheric entry probe mISSions to the giant planets can uniquely discriminate between competing theories of solar system formation and the origin and evolution of the giant planets and their atmospheres. This provides for important comparative studies of the gas and ice giants, and to provide a laboratory for studying the atmospheric chemistries, dynamics, and interiors of all the planets including Earth. The giant planets also represent a valuable link to extrasolar planetary systems. As outlined in the recent Planetary Decadal Survey, a Saturn Probe mission - with a shallow probe - ranks as a high priority for a New Frontiers class mission [1].

Simon-Miller, A. A.; Lunine, J. I.; Atreya, S. K.; Spilker, T. R.; Coustenis, A.; Atkinson, D. H.

2012-01-01

340

Theortetical Models of Extrasolar Giant Planets  

E-print Network

The recent discoveries of giant planets around nearby stars have galvanized the planetary science community, astronomers, and the public at large. Since {\\it direct} detection is now feasible, and is suggested by the recent acquisition of Gl229 B, it is crucial for the future of extrasolar planet searches that the fluxes, evolution, and physical structure of objects from Saturn's mass to 15 Juipter masses be theoretically investigated. We discuss our first attempts to explore the characteristics of extrasolar giant planets (EGPs), in aid of both NASA's and ESA's recent plans to search for such planets around nearby stars.

A. Burrows; W. B. Hubbard; J. I. Lunine; T. Guillot; D. Saumon; M. Marley; R. S. Freedman

1996-08-28

341

The Search for Extrasolar Earth-like planets  

E-print Network

The search for extrasolar Earth-like planets is underway. Over 100 extrasolar giant planets are known to orbit nearby sun-like stars, including several in multiple-planet systems. These planetary systems are stepping stones for the search for Earth-like planets; the technology development, observational strategies, and science results can all be applied to Earth-like planets. Stars much less massive than the sun the most common stars in our Galaxy are being monitored for the gravitational influence of Earth-like planets. Although Earth-like planets orbiting sun-like stars are much more difficult to detect, space missions are being built to detect them indirectly due to their effects on the parent star and to quantify fundamental factors such as terrestrial planet frequency, size distribution, and mass distribution. Extremely ambitious space programs are being developed to directly detect Earth-like planets orbiting sun-like stars, and must tackle the immense technological challenge of blocking out the light of the parent star, which is brighter than the planet by six to ten orders of magnitude. Direct detection of radiation from the planet is necessary for the definitive goal of the search for Earth-like planets: the study of atmospheric spectral signatures for signs of severe disequilibrium chemistry that could be indicative of biological activity. In addition to technological development, a growing flurry of scientific activity has begun to: understand terrestrial planet formation and terrestrial planet frequency; model terrestrial-like planet atmospheres and evolution; articulate the biological signatures of our own Earth; and even to study Earth as an extrasolar planet by observation and analysis of the spatially unresolved Earth.

S. Seager

2003-05-19

342

Extrasolar Planets: A Galactic Perspective  

E-print Network

The host stars of extrasolar planets tend to be metal-rich. We have examined the data for these stars for evidence of trends in other galactic parameters, without success. However, several ESP hosts are likely to be members of the thick disk population, indicating that planet formation has occurred throughout the full lifetime of the Galactic disk. We briefly consider the radial metallicity gradient and age-metallicity relation of the Galactic disk, and complete a back-of-the envelope estimate of the likely number of solar-type stars with planetary companions with 6 < R < 10 kpc.

I. N. Reid

2006-08-15

343

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

344

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

345

Vapor pressure isotope fractionation effects in planetary atmospheres: application to deuterium  

E-print Network

The impact of the vapor pressure difference between deuterated and nondeuterated condensing molecules in planetary atmospheres is quantitatively assessed. This difference results in a loss of deuterium in the vapor phase above the condensation level. In Titan, Uranus and Neptune, the effect on CH3D is too subtle to alter current D/H ratio determinations. In Mars, the effect can induce a large depletion of HDO, starting about one scale height above the condensation level. Although the current infrared measurements of the D/H ratio appear to be almost unaffected, the intensity of disk-averaged millimetric HDO lines can be modified by about 10%. The effect is much stronger in limb sounding, and can be easily detected from orbiter observations.

Thierry Fouchet; Emmanuel Lellouch

1999-11-15

346

Submillimeter Remote Sensing of Planetary and Cometary Atmospheres and LRO/LCROSS Observations of the Moon  

NASA Technical Reports Server (NTRS)

Submillimeter remote sensing of planetary and cometary atmospheres have been proposed for Venus and Mars while MIRO on Rosetta will observe the coma of Comet 67P/Churyumov - Cierasimenko in December 2015, UARS and AURA MLS have observed millimeter and submillimeter molecule emissions in the Earth's stratosphere for many decades, Observations of submillimeter wave molecular emissions provide a wealth of information not obtainable by alternative techniques. Submillimeter line emissions exhibit linear temperature dependence, insensitivity to aerosol scattering, extinction, and have separated transitions with well determined line-shapes. These observations have high sensitivities to trace chemical species and can; 1) Fully resolve the line profiles of molecules with high resolution, 2) Provide deterministic retrievals of species abundance, temperature, and pressure, and 3) Measure Doppler shifts of detected molecules for wind velocities.

Chin, Gordon

2011-01-01

347

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

NASA Technical Reports Server (NTRS)

We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. Based on a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We then retrieved water and D/H in the atmospheres of Mars, comet C/2007 WI, and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

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

2012-01-01

348

Weak absorptions in high density planetary atmospheres measured by the cavity ring down technique.  

NASA Astrophysics Data System (ADS)

High density planetary atmospheres are characterized by a high opacity due to the strong absorbers. Howevere usually several transparency windows exist which allow to study the lower part of the atmosphere as well as the surface emission. The weak absorptions occurring in these transparency windows are mostly due to trace species and to continuum absorption of the major absorber(s). A good example is the atmosphere of Venus, where carbondioxide causes a high opacity throughout most of the infrared wavelengths, but also has some transparency spectral windows in the near infrared, allowing the study of low lying clouds , trace species such as water vapor and in some cases the surface emission. The cavity ring down (CRD) technique has shown to be a good tool for studying weak absorptions. Here we present a CRD apparatus which can be operated at high pressures (up to 40 bar) with a sensitivity which allows to measure attenuations up to 2x10?8 cm?1. This instrument has been used to measure the carbon dioxide absorption at pressures up to 40 bar and has been also used to measure attenuation due to Rayleigh scattering at 1.18 ?m.

Snels, M.; Stefani, S.; Piccioni, G.

2014-04-01

349

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

Microsoft Academic Search

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

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

2010-01-01

350

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

351

A method for the direct determination of the surface gravities of transiting extrasolar planets  

E-print Network

We show that the surface gravity of a transiting extrasolar planet can be calculated from only the spectroscopic orbit of its parent star and the analysis of its transit light curve. This does not require additional constraints, such as are often inferred from theoretical stellar models or model atmospheres. The planet's surface gravity can therefore be measured precisely and from only directly observable quantities. We outline the method and apply it to the case of the first known transiting extrasolar planet, HD 209458b. We find a surface gravity of g_p = 9.28 +/- 0.15 m/s, which is an order of magnitude more precise than the best available measurements of its mass, radius and density. This confirms that the planet has a much lower surface gravity that that predicted by published theoretical models of gas giant planets. We apply our method to all fourteen known transiting extrasolar planets and find a significant correlation between surface gravity and orbital period, which is related to the known correlation between mass and period. This correlation may be the underlying effect as surface gravity is a fundamental parameter in the evaporation of planetary atmospheres.

John Southworth; Peter J. Wheatley; Giles Sams

2007-04-12

352

ExtraSolar Planets Finding Extrasolar Planets. I  

E-print Network

ExtraSolar Planets #12;Finding Extrasolar Planets. I Direct Searches Direct searches are difficult #12;Finding Extrasolar Planets. II Transits #12;Transits Transits requires an edge-on orbit. ·Jupiter;How Transits Work #12;Finding Extrasolar Planets. III Astrometric Wobble #12;Finding Extrasolar

Walter, Frederick M.

353

Aerial Vehicle Surveys of other Planetary Atmospheres and Surfaces: Imaging, Remote-sensing, and Autonomy Technology Requirements  

NASA Technical Reports Server (NTRS)

The objective of this paper is to review the anticipated imaging and remote-sensing technology requirements for aerial vehicle survey missions to other planetary bodies in our Solar system that can support in-atmosphere flight. In the not too distant future such planetary aerial vehicle (a.k.a. aerial explorers) exploration missions will become feasible. Imaging and remote-sensing observations will be a key objective for these missions. Accordingly, it is imperative that optimal solutions in terms of imaging acquisition and real-time autonomous analysis of image data sets be developed for such vehicles.

Young, Larry A.; Pisanich, Gregory; Ippolito, Corey; Alena, Rick

2005-01-01

354

Evaporation and accretion of extrasolar comets following white dwarf kicks  

NASA Astrophysics Data System (ADS)

Several lines of observational evidence suggest that white dwarfs receive small birth kicks due to anisotropic mass-loss. If other stars possess extrasolar analogues to the Solar Oort cloud, the orbits of comets in such clouds will be scrambled by white dwarf natal kicks. Although most comets will be unbound, some will be placed on low angular momentum orbits vulnerable to sublimation or tidal disruption. The dusty debris from these comets will manifest itself as an IR excess temporarily visible around newborn white dwarfs; examples of such discs may already have been seen in the Helix Nebula, and around several other young white dwarfs. Future observations with the James Webb Space Telescope may distinguish this hypothesis from alternatives such as a dynamically excited Kuiper Belt analogue. Although competing hypotheses exist, the observation that ?15 per cent of young white dwarfs possess such discs, if interpreted as indeed being cometary in origin, provides indirect evidence that low-mass gas giants (thought necessary to produce an Oort cloud) are common in the outer regions of extrasolar planetary systems. Hydrogen abundances in the atmospheres of older white dwarfs can, if sufficiently low, also be used to place constraints on the joint parameter space of natal kicks and exo-Oort cloud models.

Stone, Nicholas; Metzger, Brian D.; Loeb, Abraham

2015-03-01

355

Role of desorption processes in the formation of K in tenuous planetary atmospheres  

NASA Astrophysics Data System (ADS)

We will discuss recent laboratory data indicating that DIET processes (desorption induced by electronic transitions) may affect planetary atmospheres. We focus on the origins of neutral potassium vapor in the atmospheres of the planet Mercury, the Moon, and the icy satellites of Jupiter. We are conducting ultrahigh-vacuum studies of adsorption and desorption of atomic potassium on model mineral systems (SiO2 thin films), as well as on models of icy satellite surfaces (condensed water ice films). We found evidence previously that non-thermal processes - mainly photon-stimulated desorption (PSD) by UV photons - may play a dominant role in desorption of Na atoms from the lunar surface[1], and the present results indicate that K can be desorbed by PSD. The desorption mechanism involves a photon-excited charge-exchange process, in which adsorbed ionic K is converted to neutral K, which desorbs. Recent data on desorption from a lunar sample will be discussed. [1] B. V. Yakshinskiy and T. E. Madey, Nature 400(1999) 642; Surface Science 451 (2000) 160. This work has been supported in part by NASA

Madey, T. E.; Yakshinskiy, B. V.

2001-11-01

356

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.

357

FUV Irradiances, Flares and Winds of the Early Sun: Effects on Early Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

We propose to use the FUSE satellite to determine the flare characteristics, winds, and accurate FUV irradiances for two solar-type stars that serve as proxies for the young Sun covering the first 300 Myr of its history. This program is the remaining part of a comprehensive study of the Sun in Time across the electromagnetic spectrum. We have defined a sample of single G0-5 V stars with well-known rotation periods and ages that are proxies for the Sun at different times. One of the major goals of the program was the determination of the spectral irradiance of the early Sun which is now nearing completion. Our analysis and modeling indicate that the strong XUV emissions of the young Sun could have played a crucial role in the developing planetary system, in particular through the photoionization, photochemical evolution and possible erosion of the planetary atmospheres. An important, yet still missing, ingredient to understand the early Sun is the characterization of the solar wind, flares and coronal mass ejections (CMEs). FUSE is uniquely suited to address these important question, both thanks to its high spectral resolution and wavelength coverage. The FUSE wavelength region contains key spectral features such as the H Lyman series, C III, O VI and an important coronal Fe XVIII line. Thus, FUSE observations permit the simultaneous study of plasmas covering temperatures from ~104 K to ~107 K. Enhancements of the hotter lines, line profile asymmetries or superimposed absorptions are the manifestations of winds, CMEs and flares. This program is also crucial for understanding the operation of the solar dynamo and the transfer of magnetic energy within the chromosphere, the transition region and the corona of the Sun and solar type stars.

Guinan, E.

358

SURVEY FOR TRANSITING EXTRASOLAR PLANETS IN STELLAR SYSTEMS. III. A LIMIT ON THE FRACTION OF STARS WITH PLANETS IN THE OPEN CLUSTER NGC 1245  

E-print Network

SURVEY FOR TRANSITING EXTRASOLAR PLANETS IN STELLAR SYSTEMS. III. A LIMIT ON THE FRACTION OF STARS photometric search for transiting extrasolar planets in the open cluster NGC 1245. An automated transit search: individual (NGC 1245) -- planetary systems 1. INTRODUCTION Extrasolar planet detections and analysis

Gaudi, B. Scott

359

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

360

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

361

Dynamical relaxation and massive extrasolar planets  

Microsoft Academic Search

Following the suggestion of BlackQ1 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 100au. These are assumed to have formed rapidly

John C. B. Papaloizou; Caroline Terquem

2001-01-01

362

An IRAS search for extra-solar Oort clouds  

NASA Technical Reports Server (NTRS)

The presumptively close connection between Oort cloud formation and planetary formation is that the detection of comet clouds around other stars would imply the presence of extrasolar planetary systems. Low-resolution IRAS data and an S/N-enhancement method are presently used to search 17 nearby stars for comet cloud-indicating IR emission. While no such detections were obtained, upper limits have been set for extrasolar Oort clouds (ESOCs) around the candidate stars; the nondetections may be a results either of the absence of the ESOCs around these stars or, with greater probability, of the sensitivity and background confusion limitations of IRAS data.

Stern, S. Alan; Stocke, John; Weissman, Paul R.

1991-01-01

363

3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars  

E-print Network

The potential habitability of a terrestrial planet is usually defined by the possible existence of liquid water on its surface. The potential presence of liquid water depends on many factors such as, most importantly, surface temperatures. The properties of the planetary atmosphere and its interaction with the radiative energy provided by the planet's host star are thereby of decisive importance. In this study we investigate the influence of different main-sequence stars upon the climate of Earth-like extrasolar planets and their potential habitability by applying a 3D Earth climate model accounting for local and dynamical processes. The calculations have been performed for planets with Earth-like atmospheres at orbital distances where the total amount of energy received from the various host stars equals the solar constant. In contrast to previous 3D modeling studies, we include the effect of ozone radiative heating upon the vertical temperature structure of the atmospheres. The global orbital mean results o...

Godolt, M; Hamann-Reinus, A; Kitzmann, D; Kunze, M; Langematz, U; von Paris, P; Patzer, A B C; Rauer, H; Stracke, B

2015-01-01

364

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

365

Elemental Compositions of Extrasolar Planetesimals  

NASA Astrophysics Data System (ADS)

The composition of extrasolar rocky planets is essential for understanding the formation and evolution of these alien worlds. Studying externally-polluted white dwarfs provides the only method to directly measure the elemental compositions of extrasolar planetesimals, the building blocks of planets. The standard model is that some planetesimals can survive to the white dwarf phase, get perturbed, enter into the tidal radius of the white dwarf and get accreted, polluting its pure hydrogen or helium atmosphere. We have been performing high-resolution spectroscopic observations on a number of polluted white dwarfs to measure the bulk compositions of the accreted objects. To have a full picture of the abundance pattern, we gathered data from both Keck/HIRES and HST/COS. I will present the analysis for one of the most interesting objects -- G29-38. It is the first white dwarf identified with an infrared excess from debris of pulverized planetesimals and among the very first identified polluted hydrogen atmosphere white dwarfs. Our analysis indicates that the accreted extrasolar planetesimal is enhanced in refractory elements and depleted in volatile elements. A detailed comparison with solar system objects show that the observed composition can be best interpreted as a blend of chondritic object with some refractory-rich material, a result from post-nebular processing. When all polluted white dwarfs are viewed as an ensemble, we find that the elemental compositions of accreted extrasolar planetesimals resemble to those of solar system objects to zeroth order. (i) The big four elements, O, Fe, Mg and Si are also dominant. Objects with exotic compositions, e.g. diamond planets and refractory-dominated planets, are yet to be found. (ii) Volatiles, such as carbon and water, are only trace constituents. In terms of bulk composition, solar system objects are essentially normal.

Xu, Siyi; Jura, M.

2014-01-01

366

Search for hydrogen peroxide in the Martian atmosphere by the Planetary Fourier Spectrometer onboard Mars Express  

NASA Astrophysics Data System (ADS)

We searched for hydrogen peroxide (H2O2) in the Martian atmosphere using data measured by the Planetary Fourier Spectrometer (PFS) onboard Mars Express during five martian years (MY27-31). It is well known that H2O2 plays a key role in the oxidizing capacity of the Martian atmosphere. However, only a few studies based on ground-based observations can be found in the literature. Here, we performed the first analysis of H2O2 using long-term measurements by a spacecraft-borne instrument. We used the ?4 band of H2O2 in the spectral range between 359 cm-1 and 382 cm-1 where strong features of H2O2 are present around 362 cm-1 and 379 cm-1. Since the features were expected to be very weak even at the strong band, sensitive data calibrations were performed and a large number of spectra were selected and averaged. We made three averaged spectra for different seasons over relatively low latitudes (50°S-50°N). We found features of H2O2 at 379 cm-1, whereas no clear features were detected at 362 cm-1 due to large amounts of uncertainty in the data. The derived mixing ratios of H2O2 were close to the detection limits: 16 ± 19 ppb at Ls = 0-120°, 35 ± 32 ppb at Ls = 120-240°, and 41 ± 28 ppb at Ls = 240-360°. The retrieved value showed the detection of H2O2 only for the third seasonal period, and the values in the other periods provided the upper limits. These long-term averaged abundances derived by the PFS generally agreed with the ones reported by ground-based observations. From our derived mixing ratio of H2O2, the lifetime of CH4 in the Martian atmosphere is estimated to be several decades in the shortest case. Our results and sporadic detections of CH4 suggest the presence of strong CH4 sinks not subject to atmospheric oxidation.

Aoki, Shohei; Giuranna, Marco; Kasaba, Yasumasa; Nakagawa, Hiromu; Sindoni, Giuseppe; Geminale, Anna; Formisano, Vittorio

2015-01-01

367

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

368

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

369

An Investigation of Dynamical Mechanisms Associated with Planetary Wave Disturbances of the Winter Polar Middle Atmosphere  

NASA Astrophysics Data System (ADS)

Throughout the winter season the polar middle atmosphere is intermittently disturbed; the most spectacular type of disturbance is a major Sudden Stratospheric Warming (SSW). However, the region is dynamically active and exhibits other types of disturbances on a more frequent basis. One such disturbance is synoptic-scale "weather events" observed in lidar and rocket soundings, soundings from the TIMED/SABER instrument and UK Meteorological Office (MetO) assimilated data. These disturbances are most easily identified near 42 km where temperatures are elevated over nominal conditions by 50 K and an associated cooling is observed near 75 km. As these disturbances have a vertical structure extending into the lower mesosphere, they will be termed Upper Stratospheric/Lower Mesospheric (USLM) disturbances. We investigate the dynamical mechanisms responsible for USLM disturbances using the above mentioned observations in addition to model outputs from the Whole Atmosphere Community Climate Model (WACCM). Planetary wave amplification appears to be a required but insufficient condition; using the Charney-Stern criteria for instability the role of baroclinic, barotropic and inertial instabilities in the development of USLM disturbances is explored. Employing EP-flux and potential vorticity analysis techniques, the role the instability plays is demonstrated in its interaction with the zonal mean flow and the conversion of potential energy to kinetic energy. In addition, USLM disturbances appear to have front-like behavior analogous to fronts in the troposphere. Broader impacts of these disturbances and the dynamics associated with them are influences on gravity wave generation/propagation, vertical air motion and chemical tracer transport.

Greer, K.; Thayer, J. P.; Liu, H.; Harvey, V.; Peck, E. D.

2011-12-01

370

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

371

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 and Computational Science, National university of Singapore September 30 2000 Abstract A statistical mechanics

Lim, Chjan C.

372

On the use of Very Low Frequency transmitter data for remote sensing of atmospheric gravity and planetary waves  

NASA Astrophysics Data System (ADS)

Continuous ground-based monitoring of Very Low Frequency (VLF) transmitter signals is an efficient remote sensing tool for studying of the lower ionosphere (60-90 km). Here, we present the use of VLF radio data to study short-period (?min-hrs) atmospheric gravity waves and long-period (?days) planetary waves. We analyse VLF data from several receiving stations obtained by ICSP-VLF network during the total solar eclipse of July, 2009 to show the existence of short-period atmospheric gravity waves. We find dominant wave periods range from 10 min to 1 h around the time of maximum eclipse phase which could be associated with atmospheric gravity waves excited due to the eclipse. We also analyse VLF amplitude data of 2007 received at ICSP, Kolkata from VTX (18.2 kHz) transmitter for planetary wave-type oscillations in the mesosphere-lower ionosphere system. Fourier and wavelet analysis show presence of periodic structures with periodicity in the range of 5-27 days. We compare VLF planetary spectrum with spectrum obtained from total column density of Ozone and mesospheric average temperature data which may indicate vertical coupling between the stratosphere and ionosphere in winter to early spring time.

Pal, Sujay; Chakraborty, Suman; Chakrabarti, Sandip K.

2015-02-01

373

Bok Prize Lecture (shared) Towards a Physical Characterization of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We have entered a new era in planetary astrophysics with well over 100 giant planets now known to orbit nearby sun-like stars. Recent theoretical and observational advances have given us new constraints on the physical characteristics of extrasolar planets, while ongoing and proposed observing programs and space missions hold great promise for the future of extrasolar planet science. I will discuss the emerging understanding of the extrasolar transiting planet HD209458b, tying together several recent observational constraints as well as key upcoming measurements.I will also briefly review scientific highlights and prospects for the future detection and study of Earth-like extrasolar planets.

Seager, Sara

2004-03-01

374

Obliquity evolution of extrasolar terrestrial planets  

E-print Network

We have investigated the obliquity evolution of terrestrial planets in habitable zones (at ~ 1AU) in extrasolar planetary systems, due to tidal interactions with their satellite and host star with wide varieties of satellite-to-planet mass ratio and initial obliquity, through numerical calculations and analytical arguments. The obliquity, the angle between planetary spin axis and its orbit normal, of a terrestrial planet is one of the key factors in determining the planetary surface environments. A recent scenario of terrestrial planet accretion implies that giant impacts of Mars-sized bodies determine the planetary spin and form satellites. With isotropic giant impacts, tilted spins are more likely to be produced than straight ones and satellites with various mass are formed. However, most of previous studies have focused on a particular case of the Earth-Moon systems or the two-body planar problem. We numerically integrated the evolution of planetary spin and a satellite orbit with various satellite mass and initial obliquity. We found that in the case of initially tiled spins, the satellite's orbit migrates outward until the orbit reaches the critical radius ~ 10-20 planetary radii, but then the migration is reversed to inward one with large-amplitude oscillation. The satellite eventually falls onto the planetary surface or it is captured at the synchronous state at several planetary radii. With the results of numerical integration and analytical arguments, we identified the parameter regions of qualitatively different evolution.

Keiko Atobe; Shigeru Ida

2006-11-21

375

A Lumped Element Thermal Model of Solar Flare Gradual Phase EUV Emissions for Planetary Atmosphere Studies  

NASA Astrophysics Data System (ADS)

Gradual phase solar flare EUV emissions show a time dependence related to the cooling of the flare plasma where emission lines with higher formation temperatures peak earlier than cooler emission lines. Because photon absorption height in a planetary atmosphere is wavelength dependent, being able to spectrally model this time dependence using available wavelengths is necessary to accurately characterize the temporal response of an atmosphere to a flare when high time cadence measurements of the EUV spectrum are unavailable. Furthermore, both the spectral and wavelength dependent temporal behavior of a flare impact where the total flare energy is absorbed in an atmosphere.To address this challenge, we have developed a Lumped Element Thermal Model (LETM) which can accurately model the flare gradual phase time evolution for emission lines with peak formation temperatures above 106 K based on a cooling rate derived from only two emission lines. We will show that the 13.3 nm Fe XX and 9.4 nm Fe XVIII emission lines can be used to determine a cooling rate. This cooling rate can then be used to calculate a time constant, ?i, associated with a ith EUV emission; and the ith emission’s time-response can then be modeled by passing the measured Fe XX time-series through a digital low pass filter with time constant ?i. An implication of the LETM, is that it constrains the time evolution of the volume integrated flare irradiance which is directly related to the flare emission measure. Detailed analysis suggests that the LETM provides a method to measure the flare thermal conductance and specific heat, and constrains the flare cooling rate and differential emission measure.To broaden the utility of the LETM, correlations between the emission line derived cooling rate and broadband measurements made by MAVEN EUV or other commonly available Earth assets must be found. Therefore, in addition to introducing the LETM, we will review progress towards finding correlations with properties of broadband soft x-ray measurements, as well as relevant multi-channel instruments.

Thiemann, Edward; Eparvier, Francis G.

2015-04-01

376

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

NASA Technical Reports Server (NTRS)

The nature and magnitude of turbulence-induced errors in atmospheric profiles derived from Doppler measurements made during radio occultations are investigated. It is found that turbulence in planetary atmospheres induces both fluctuating and systematic errors in derived profiles, but the errors of both types are very small. Consideration of the occultation of Mariner 10 by Venus and of the Pioneer occultations by Jupiter shows that the rms fractional errors in the atmospheric profiles derived from these observations were less than 0.01 in both temperature and pressure, while the fractional systematic errors were typically of the order of 1 millionth. The extent to which atmospheric profiles derived from radio and optical intensity measurements are affected by turbulence is also examined. The results indicate that turbulence in planetary atmospheres has only a marginal effect on derived profiles in the weak-scattering limit and that the turbulence-induced errors in this case are always much larger than the corresponding errors in profiles derived from radio Doppler measurements.

Haugstad, B. S.

1978-01-01

377

Extrasolar planets detections and statistics through gravitational microlensing  

NASA Astrophysics Data System (ADS)

Gravitational microlensing was proposed thirty years ago as a promising method to probe the existence and properties of compact objects in the Galaxy and its surroundings. The particularity and strength of the technique is based on the fact that the detection does not rely on the detection of the photon emission of the object itself, but on the way its mass affects the path of light of a background, almost aligned source. Detections thus include not only bright, but also dark objects. Today, the many successes of gravitational microlensing have largely exceeded the original promises. Microlensing contributed important results and breakthroughs in several astrophysical fields as it was used as a powerful tool to probe the Galactic structure (proper motions, extinction maps), to search for dark and compact massive objects in the halo and disk of the Milky Way, to probe the atmospheres of bulge red giant stars, to search for low-mass stars and brown dwarfs and to hunt for extrasolar planets. As an extrasolar planet detection method, microlensing nowadays stands in the top five of the successful observational techniques. Compared to other (complementary) detection methods, microlensing provides unique information on the population of exoplanets, because it allows the detection of very low-mass planets (down to the mass of the Earth) at large orbital distances from their star (0.5 to 10 AU). It is also the only technique that allows the discovery of planets at distances from Earth greater than a few kiloparsecs, up to the bulge of the Galaxy. Microlensing discoveries include the first ever detection of a cool super-Earth around an M-dwarf star, the detection of several cool Neptunes, Jupiters and super-Jupiters, as well as multi-planetary systems and brown dwarfs. So far, the least massive planet detected by microlensing has only three times the mass of the Earth and orbits a very low mass star at the edge of the brown dwarf regime. Several free-floating planetary-mass objects, including free-floating planets of about Jupiter's mass, were also detected trough microlensing. Detections and non-detections inform us on the abundance of planets as a function of planetary mass and orbital distance. Recent microlensing studies imply that low-mass planets, in particular super-Earths, are far more abundant than giant planets, and reveal that there are, on average, one or more bound planets per Milky Way star. Future microlensing surveys will dramatically increase the number of microlensing alerts, thus providing unprecedented constraints on the planetary mass function, down to the mass of the Earth.

Cassan, A.

2014-10-01

378

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

379

A Test of Near Infrared Differential Photometry for Study of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We report on test observations, done through the UKIRT Service Observing Program, of the transiting extrasolar system XO-3. While optical monitoring of transiting extrasolar systems is fairly routine, extension to the near infrared (NIR) has only recently been accomplished. Since the emergent flux from close-in planets peaks in the NIR, these bands are sensitive to atmospheric temperature and energy distribution. Furthermore, molecular bands in the planetary atmospheres alter the flux across ground-observable NIR bands; observations then constrain the atmospheric molecular abundances. We used 2MASS K-band images to examine transiting systems for their suitability for differential photometry. We selected XO-3 as one of our top choices and acquired one hour of randomly-timed data in Feb 09. We used a narrowband filter centered at 2.12 microns partly to avoid saturation and also to investigate the suitability of narrowband filters for these types of observations. Using standard aperture photometry techniques and a differential photometry algorithm provided by C. Broeg, we investigated the variability of the stars in the field. We found that XO-3 varied more than stars of comparable magnitude and, after construction of a light curve and comparing it to the XO-3 ephemeris, we discovered our data included roughly the last 25% of a primary transit. We will present analysis of our data. The success of these observations motivated us to propose for multiple narrowband filter observations in 2010A in order to construct a pseudo-spectrum of an extrasolar planet's emission. The routine acquisition of narrowband data such as we seek will significantly advance our understanding of exoplanetary atmospheres.

Prilepina, Valentina; Rodriguez, N.; Kruger, A.; Richter, M.

2010-01-01

380

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

381

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

382

Observed properties of extrasolar planets.  

PubMed

Observational surveys for extrasolar planets probe the diverse outcomes of planet formation and evolution. These surveys measure the frequency of planets with different masses, sizes, orbital characteristics, and host star properties. Small planets between the sizes of Earth and Neptune substantially outnumber Jupiter-sized planets. The survey measurements support the core accretion model, in which planets form by the accumulation of solids and then gas in protoplanetary disks. The diversity of exoplanetary characteristics demonstrates that most of the gross features of the solar system are one outcome in a continuum of possibilities. The most common class of planetary system detectable today consists of one or more planets approximately one to three times Earth's size orbiting within a fraction of the Earth-Sun distance. PMID:23641110

Howard, Andrew W

2013-05-01

383

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

NASA Astrophysics Data System (ADS)

For the purpose of investigating the photon energy dependence of the photoinduced abiotic synthesis of organic molecules, gas mixtures that simulate typical planetary atmospheres, including a carbon source (CO or CH4), a nitrogen source (N2 or NH3), and H2O, were irradiated with synchrotron radiation through a vacuum-ultraviolet transmitting window. Three kinds of window material, fused silica, synthetic quartz, and MgF2, were used as a high-energy-cutting filter, whose absorption-edge energies are 6.4, 8.1, and 10.5 eV, respectively. Three types of gas mixture, Titan-type (CH4-N2-H2O), comet-type (CO-NH3-H2O), and primitive-Earth-type (CO-N2-H2O), were irradiated with vacuum-ultraviolet photons in the three energy ranges. After the irradiation, amino-acid formation yields in the acid-hydrolyzed solution of the product were measured with a high-performance liquid chromatograph method. From the Titan- and comet-type mixtures, amino acids were detected by irradiation with photons lower than 8.1 eV. For both mixtures, the averaged quantum yields of glycine generation in the photon energy region of 7-10.5 eV were of the order of 10-5, which was larger by about one order than that in the region 5-8 eV. On the other hand, from the primitive-Earth-type mixture, amino-acid formation was difficult to detect even with irradiation as high as 10.5 eV, even though amino acids were generated in comparable yields from the Titan- and comet-type mixtures by irradiation with soft x rays or proton beam, whose energies are much higher. These results suggest that the vacuum ultraviolet light is a more effective energy source for the generation of the precursors of bioorganic compounds in extraterrestrial environments than in primitive-Earth atmosphere.

Takahashi, Jun-Ichi; Masuda, Hitomi; Kaneko, Takeo; Kobayashi, Kensei; Saito, Takeshi; Hosokawa, Teruo

2005-07-01

384

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

385

XUV-driven mass loss from extrasolar giant planets orbiting active stars  

NASA Astrophysics Data System (ADS)

Upper atmospheres of Hot Jupiters are subject to extreme radiation conditions that can result in rapid atmospheric escape. The composition and structure of the upper atmospheres of these planets are affected by the high-energy spectrum of the host star. This emission depends on stellar type and age, which are thus important factors in understanding the behaviour of exoplanetary atmospheres. In this study, we focus on Extrasolar Giant Planets (EPGs) orbiting K and M dwarf stars. XUV spectra for three different stars - ? Eridani, AD Leonis and AU Microscopii - are constructed using a coronal model. Neutral density and temperature profiles in the upper atmosphere of hypothetical EGPs orbiting these stars are then obtained from a fluid model, incorporating atmospheric chemistry and taking atmospheric escape into account. We find that a simple scaling based solely on the host star's X-ray emission gives large errors in mass loss rates from planetary atmospheres and so we have derived a new method to scale the EUV regions of the solar spectrum based upon stellar X-ray emission. This new method produces an outcome in terms of the planet's neutral upper atmosphere very similar to that obtained using a detailed coronal model of the host star. Our results indicate that in planets subjected to radiation from active stars, the transition from Jeans escape to a regime of hydrodynamic escape at the top of the atmosphere occurs at larger orbital distances than for planets around low activity stars (such as the Sun).

Chadney, J. M.; Galand, M.; Unruh, Y. C.; Koskinen, T. T.; Sanz-Forcada, J.

2015-04-01

386

Effects of planetary waves on variations in the upper atmsopehre using an atmosphere-ionsophere coupled model  

NASA Astrophysics Data System (ADS)

Recent observational and modeling studies have revealed that the energy input from the lower atmosphere produces significant spatial and temporal variations in the thermosphere/ionosphere. For example, the distributions of the neutral temperature and electron density in the equatorial thermosphere/ionosphere show wave-4 longitudinal structure. This wave-4 pattern is considered to originate from non-migrating diurnal tide (DE3) that is excited in the troposphere. However, the physical mechanism of spatial and temporal variations in the thermosphere/ionosphere caused by upward propagating atmospheric waves is not fully understood. In order to investigate the physical mechanism of these variations, we developed an atmosphere-ionosphere coupled model, in which a whole atmosphere general circulation model, an ionosphere model and an electrodynamics model are integrated. The coupled model, which is called Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA), is useful for investigating efefcts of upward propagating atmospheric waves on the upper atmospheric behaviors. Using the coupled model, we examine effects of planetary waves, such as the 5-day wave and 2-day wave, from the lower atmosphere on longitudinal and temporal variations in the thermosphere/ionosphere. We also discuss further development of the coupled model in the near future.

Miyoshi, Yasunobu; Fujiwara, Hitoshi; Shinagawa, Hiroyuki; Jin, Hidekatsu

2012-07-01

387

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

388

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

SciTech Connect

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

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

2010-06-01

389

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

390

Extrasolar Trojan Planets close to Habitable Zones  

E-print Network

We investigate the stability regions of hypothetical terrestrial planets around the Lagrangian equilibrium points L4 and L5 in some specific extrasolar planetary systems. The problem of their stability can be treated in the framework of the restricted three body problem where the host star and a massive Jupiter-like planet are the primary bodies and the terrestrial planet is regarded as being massless. From these theoretical investigations one cannot determine the extension of the stable zones around the equilibrium points. Using numerical experiments we determined their largeness for three test systems chosen from the table of the know extrasolar planets, where a giant planet is moving close to the so-called habitable zone around the host star in low eccentric orbits. The results show the dependence of the size and structure of this region, which shrinks significantly with the eccentricity of the known gas giant.

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

2004-08-04

391

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

392

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

393

A TEOM (tm) particulate monitor for comet dust, near Earth space, and planetary atmospheres  

NASA Technical Reports Server (NTRS)

Scientific missions to comets, near earth space, and planetary atmospheres require particulate and mass accumulation instrumentation for both scientific and navigation purposes. The Rupprecht & Patashnick tapered element oscillating microbalance can accurately measure both mass flux and mass distribution of particulates over a wide range of particle sizes and loadings. Individual particles of milligram size down to a few picograms can be resolved and counted, and the accumulation of smaller particles or molecular deposition can be accurately measured using the sensors perfected and toughened under this contract. No other sensor has the dynamic range or sensitivity attained by these picogram direct mass measurement sensors. The purpose of this contract was to develop and implement reliable and repeatable manufacturing methods; build and test prototype sensors; and outline a quality control program. A dust 'thrower' was to be designed and built, and used to verify performance. Characterization and improvement of the optical motion detection system and drive feedback circuitry was to be undertaken, with emphasis on reliability, low noise, and low power consumption. All the goals of the contract were met or exceeded. An automated glass puller was built and used to make repeatable tapered elements. Materials and assembly methods were standardized, and controllers and calibrated fixtures were developed and used in all phases of preparing, coating and assembling the sensors. Quality control and reliability resulted from the use of calibrated manufacturing equipment with measurable working parameters. Thermal and vibration testing of completed prototypes showed low temperature sensitivity and high vibration tolerance. An electrostatic dust thrower was used in vacuum to throw particles from 2 x 10(exp 6) g to 7 x 10(exp -12) g in size. Using long averaging times, particles as small as 0.7 to 4 x 10(exp 11) g were weighted to resolutions in the 5 to 9 x 10(exp -13) g range. The drive circuit and optics systems were developed beyond what was anticipated in the contract, and are now virtually flight prototypes. There is already commercial interest in the developed capability of measuring picogram mass losses and gains. One area is contamination and outgassing research, both measuring picogram losses from samples and collecting products of outgassing.

1988-01-01

394

Models of Irradiated Extrasolar Giant Planets  

E-print Network

We review some of the characteristics of irradiated extrasolar giant planets (EGPs), in anticipation of their direct detection from the ground and from space. Spectral measurements are the key to unlocking their structural and atmospheric characteristics and to determining the true differences between giant planets and brown dwarfs. In this spirit, the theoretical spectral and atmospheric calculations we summarize here are in support of the many searches for EGPs to be conducted in the coming decade by astronomers from around the world.

Adam Burrows; David Sudarsky

2002-07-23

395

MASSACHUSETTS INSTITUTE OF TECHNOLOGY | DEpArTMENT OF EArTH, ATMOSpHErIC AND pLANETArY SCIENCES S AN UNDErGrADUATE at Carleton  

E-print Network

MASSACHUSETTS INSTITUTE OF TECHNOLOGY | DEpArTMENT OF EArTH, ATMOSpHErIC AND pLANETArY SCIENCES him to MIT's Department of Earth, Atmospheric and planetary Sciences (EApS) and to the Joint program, including geology, geochemistry, geophysics, geobiol- ogy, atmospheric science, oceanography, astronomy

Rothman, Daniel

396

Working model of the atmosphere and near planetary space of Jupiter  

NASA Technical Reports Server (NTRS)

Basic physical characteristics of Jupiter, its gravitational field, atmosphere, electromagnetic radiation, magnetosphere, meteorite situation and satellites are presented in tables, graphs and figures. Means of observation of the atmosphere and three models of the atmosphere are presented and analyzed.

Moroz, V. I. (editor)

1978-01-01

397

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

398

ATMOSPHERIC CIRCULATION OF ECCENTRIC HOT NEPTUNE GJ436b  

SciTech Connect

GJ436b is a unique member of the transiting extrasolar planet population being one of the smallest and least irradiated and possessing an eccentric orbit. Because of its size, mass, and density, GJ436b could plausibly have an atmospheric metallicity similar to Neptune (20-60 times solar abundances), which makes it an ideal target to study the effects of atmospheric metallicity on dynamics and radiative transfer in an extrasolar planetary atmosphere. We present three-dimensional atmospheric circulation models that include realistic non-gray radiative transfer for 1, 3, 10, 30, and 50 times solar atmospheric metallicity cases of GJ436b. Low metallicity models (1 and 3 times solar) show little day/night temperature variation and strong high-latitude jets. In contrast, higher metallicity models (30 and 50 times solar) exhibit day/night temperature variations and a strong equatorial jet. Spectra and light curves produced from these simulations show strong orbital phase dependencies in the 50 times solar case and negligible variations with orbital phase in the 1 times solar case. Comparisons between the predicted planet/star flux ratio from these models and current secondary eclipse measurements support a high metallicity atmosphere (30-50 times solar abundances) with disequilibrium carbon chemistry at play for GJ436b. Regardless of the actual atmospheric composition of GJ436b, our models serve to illuminate how metallicity influences the atmospheric circulation for a broad range of warm extrasolar planets.

Lewis, Nikole K.; Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Marley, Mark S.; Freedman, Richard S. [NASA Ames Research Center 245-3, Moffett Field, CA 94035 (United States); Lodders, Katharina, E-mail: nlewis@lpl.arizona.ed [Washington University, One Brookings Drive, St. Louis, MO 63130 (United States)

2010-09-01

399

Using N2-N2 Collisionally-Induced Absorption to Detect N2 and Determine Pressure in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Planetary habitability is determined by the stability of liquid water at the surface, which depends on surface temperature and pressure. While molecular nitrogen (N2) constitutes the bulk of Earth’s atmosphere 78% by volume) and is the biggest contributor to surface pressure, it is also extremely hard to remotely detect. In particular, N2 lacks significant absorption features in the visible to near infrared because it is a symmetric homonuclear molecule with no transitional dipole moment. However, nitrogen has a collisionally-induced absorption (CIA) feature near 4.3 ?m, nearly coincident with the 4.3 ?m CO2 band but extending to shorter wavelengths. This feature has been known to spectroscopists for some time, but has never been considered in the context of exoplanet characterization from full-disk observations. We report a direct detection of this N2-N2 CIA feature in disk-integrated spectra of Earth taken by NASA’s EPOXI mission. We use the Virtual Planetary Laboratory’s 3D, line-by-line, multiply scattering Earth Model (Robinson et al., 2011) to match the EPOXI spectrum with a synthetic spectrum that includes N2-N2 CIA (coefficients from Lafferty et al., 1996). Because N2 is stable in the atmosphere for geologically long periods and is present in large quantities in the atmospheres of Earth and Venus, it may be a major component of many terrestrial exoplanet atmospheres. Since the strength of a CIA feature goes as the square of the density of the gas, it is more sensitive to pressure than other forms of absorption. We use a self-consistent 1D climate model and a line-by-line radiative transfer model to explore different pressure scenarios from 0.2 to 10 bars assuming pure N2-CO2-H2O atmospheres. We investigate the detectability of N2 in direct beam and transmission and quantify the signal-to-noise ratio required to distinguish between the different pressure cases. For example, to detect the difference between the 1 and 2 bar models at a 5-sigma level in direct beam observations at 4 ?m (??=0.05 ?m), we find a signal-to noise ratio of 8.1 is required. For planets whose atmospheres contain primarily nitrogen, this is another tool to quantify pressure and, thus, to help constrain planetary habitability.

Schwieterman, Edward; Robinson, T. D.; Meadows, V.; Crisp, D.; Misra, A.

2014-01-01

400

Witnessing Extrasolar Asteroid Destruction?  

NASA Astrophysics Data System (ADS)

40 white dwarfs with excess infrared radiation due to a circumstellar dust disk from tidally disrupted asteroids have been identified. Recently, we identified one dusty white dwarf whose infrared fluxes have been increasing since May 2014. Very likely, it is caused by a recent tidal disruption event of extrasolar asteroid. We propose DDT to follow it up in a timely manner because the flare could dissipate very soon. This proposal provides a unique opportunity to study the destruction of an extrasolar asteroid.

Xu, Siyi; Jura, Michael; Su, Kate; Meng, Huan

2014-11-01

401

XUV-driven mass loss from extrasolar giant planets orbiting active stars  

E-print Network

Upper atmospheres of Hot Jupiters are subject to extreme radiation conditions that can result in rapid atmospheric escape. The composition and structure of the upper atmospheres of these planets are affected by the high-energy spectrum of the host star. This emission depends on stellar type and age, which are thus important factors in understanding the behaviour of exoplanetary atmospheres. In this study, we focus on Extrasolar Giant Planets (EPGs) orbiting K and M dwarf stars. XUV spectra for three different stars - epsilon Eridani, AD Leonis and AU Microscopii - are constructed using a coronal model. Neutral density and temperature profiles in the upper atmosphere of hypothetical EGPs orbiting these stars are then obtained from a fluid model, incorporating atmospheric chemistry and taking atmospheric escape into account. We find that a simple scaling based solely on the host star's X-ray emission gives large errors in mass loss rates from planetary atmospheres and so we have derived a new method to scale th...

Chadney, J M; Unruh, Y C; Koskinen, T T; Sanz-Forcada, J

2014-01-01

402

Impact Events and the Erosion of Planetary Atmospheres: Some Surprising Results from Theory and Simulation  

Microsoft Academic Search

We investigate the evolution of the atmospheric blast waves produced by a K-T sized meteoritic impact on a terrestrial planet. Extending the mathematical analysis due to Kompaneets (1960) for a localized explosion in an isothermal atmosphere, we explore the response of an adiabatic atmosphere as well as model atmospheres for Earth and Venus to a 5 times 10^30 erg event.

W. I. Newman; E. M. D. Symbalisty; E. M. Jones; T. J. Ahrens

1996-01-01

403

On the temperature dependence of possible S8 infrared bands in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Measurements of the temperature dependence between 77 and 333 K of the infrared spectrum of cyclic octatomic sulfur are reported. It is suggested that the 23 micrometer Jovian feature is not due to 3 sub 8 and that the temperature dependence of the frequency of the 835/cm band of S sub 8 may be a useful temperature marker in planetary studies.

Khare, B. N.; Sagan, C.

1976-01-01

404

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

405

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

406

DETECTING OCEANS ON EXTRASOLAR PLANETS USING THE GLINT EFFECT  

SciTech Connect

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

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

2010-09-20

407

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

408

Atmospheric Biomarkers and their Evolution over Geological Timescales  

E-print Network

The search for life on extrasolar planets is based on the assumption that one can screen extrasolar planets for habitability spectroscopically. The first space born instruments able to detect as well as characterize extrasolar planets, Darwin and terrestrial planet finder (TPF-I and TPF-C) are scheduled to launch before the end of the next decade. The composition of the planetary surface, atmosphere, and its temperature-pressure profile influence a detectable spectroscopic signal considerably. For future space-based missions it will be crucial to know this influence to interpret the observed signals and detect signatures of life in remotely observed atmospheres. We give an overview of biomarkers in the visible and IR range, corresponding to the TPF-C and TPF-I/DARWIN concepts, respectively. We also give an overview of the evolution of biomarkers over time and its implication for the search for life on extrasolar Earth-like planets. We show that atmospheric features on Earth can provide clues of biological activities for at least 2 billion years.

L. Kaltenegger; K. Jucks; W. Traub

2005-12-02

409

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

410

Planetary astronomy  

NASA Technical Reports Server (NTRS)

The authors profile the field of astronomy, identify some of the key scientific questions that can be addressed during the decade of the 1990's, and recommend several facilities that are critically important for answering these questions. Scientific opportunities for the 1990' are discussed. Areas discussed include protoplanetary disks, an inventory of the solar system, primitive material in the solar system, the dynamics of planetary atmospheres, planetary rings and ring dynamics, the composition and structure of the atmospheres of giant planets, the volcanoes of IO, and the mineralogy of the Martian surface. Critical technology developments, proposed projects and facilities, and recommendations for research and facilities are discussed.

Morrison, David; Hunten, Donald; Ahearn, Michael F.; Belton, Michael J. S.; Black, David; Brown, Robert A.; Brown, Robert Hamilton; Cochran, Anita L.; Cruikshank, Dale P.; Depater, Imke

1991-01-01

411

Kinetic Energy Release in molecular dications fragmentation after VUV and EUV ionization and escape from planetary atmospheres  

NASA Astrophysics Data System (ADS)

The measurements of the Kinetic Energy Release (KER) for various ionic species originating from two-body dissociations reactions, induced by double photoionization of CO2, C2H2 and N2O neutral molecular precursors of interest in planetary atmospheres, are reported. The KER distributions as a function of the ultraviolet (UV) photon energy in the range of 30-65 eV (Vacuum and Extreme UV photons) are extracted from the electron-ion-ion coincidence spectra obtained by using tunable synchrotron radiation coupled with ion imaging techniques. This experimental method allows assessing the probability of escape for some simple ionic species in the upper atmosphere of Mars and Titan. In fact, the KER measured for H+, C+, CH+, CH2+, N+, O+, CO+, N2+ and NO+ fragment ions are ranging between 1.0 and 5.5 eV (only for H+ the maximum value reaches 6.0 eV), and these translational energies are large enough to allow these ionic species in participating in the atmospheric escape from Mars and Titan into space (for CO+, N2+ and NO+, the measured KER of 0.5-2.5 eV, 0.5-2.8 eV and 1.0-2.5 eV, respectively, allows the possible escape only from the Titan atmosphere).

Falcinelli, Stefano; Rosi, Marzio; Candori, Pietro; Vecchiocattivi, Franco; Farrar, James M.; Pirani, Fernando; Balucani, Nadia; Alagia, Michele; Richter, Robert; Stranges, Stefano

2014-09-01

412

Formation, habitability, and detection of extrasolar moons.  

PubMed

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 circumplanetary debris and gas disk or via capture from a binary, and (iii) are detectable with current technology. PMID:25147963

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

2014-09-01

413

Formation, Habitability, and Detection of Extrasolar Moons  

NASA Astrophysics Data System (ADS)

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 circumplanetary debris and gas disk or via capture from a binary, and (iii) are detectable with current technology.

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

2014-09-01

414

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

415

HAT-P-15b: A 10.9 DAY EXTRASOLAR PLANET TRANSITING A SOLAR-TYPE STAR  

SciTech Connect

We report the discovery of HAT-P-15b, a transiting extrasolar planet in the 'period valley', a relatively sparsely populated period regime of the known extrasolar planets. The host star, GSC 2883-01687, is a G5 dwarf with V= 12.16. It has a mass of 1.01 {+-} 0.04 M{sub sun}, radius of 1.08 {+-} 0.04 R{sub sun}, effective temperature 5568 {+-} 90 K, and metallicity [Fe/H] = +0.22 {+-} 0.08. The planetary companion orbits the star with a period P = 10.863502 {+-} 0.000027 days, transit epoch T{sub c} = 2454638.56019 {+-} 0.00048 (BJD), and transit duration 0.2285 {+-} 0.0015 days. It has a mass of 1.946 {+-} 0.066 M{sub J} and radius of 1.072 {+-} 0.043 R{sub J} yielding a mean density of 1.96 {+-} 0.22 g cm{sup -3}. At an age of 6.8{sup +2.5}{sub -1.6} Gyr, the planet is H/He-dominated and theoretical models require about 2% (10 M{sub +}) worth of heavy elements to reproduce its measured radius. With an estimated equilibrium temperature of {approx}820 K during transit, and {approx}1000 K at occultation, HAT-P-15b is a potential candidate to study moderately cool planetary atmospheres by transmission and occultation spectroscopy.

Kovacs, G. [Konkoly Observatory, Budapest (Hungary); Bakos, G. A.; Hartman, J. D.; Torres, G.; Noyes, R. W.; Latham, D. W.; Sasselov, D. D.; Stefanik, R. P.; Esquerdo, G. A.; Fernandez, J. M. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Howard, A. W.; Marcy, G. W.; Isaacson, H. [Department of Astronomy, University of California, Berkeley, CA (United States); Fischer, D. A. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Johnson, J. A. [California Institute of Technology, Department of Astrophysics, MC 249-17, Pasadena, CA (United States); Lazar, B. Beky J.; Papp, I.; Sari, P., E-mail: gbakos@cfa.harvard.ed [Hungarian Astronomical Association, Budapest (Hungary)

2010-12-01

416

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.

417

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

418

Analytic theory of orbit contraction and ballistic entry into planetary atmospheres  

Microsoft Academic Search

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

J. M. Longuski; N. X. Vinh

1980-01-01

419