Note: This page contains sample records for the topic extrasolar planetary atmospheres from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Extrasolar Planetary Systems  

Microsoft Academic Search

This paper is an updated version of lectures given at the Helmholtz Summer School on Extrasolar Planetary Systems (Potsdam,\\u000a 2003). It includes five sections: Orbit determination, the known planetary systems, chaos, transition from secular to resonant\\u000a dynamics and planetary migration. The first section is mainly devoted to problems arising in the orbit determination of systems\\u000a with 2 or more planets

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

2005-01-01

2

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

3

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

4

The Virtual Planetary Laboratory: Towards Characterizing Extrasolar Terrestrial Planets  

NASA Astrophysics Data System (ADS)

The Virtual Plantary Laboratory (VPL) is a recently funded 5-yr project which seeks to improve our understanding of the range of plausible environments and the likely signatures for life on extrasolar terrestrial planets. To achieve these goals we are developing a suite of innovative modeling tools to simulate the environments and spectra of extrasolar planets. The core of the VPL is a coupled radiative transfer/climate/chemistry model, which is augmented by interchangeable modules which characterize geological, exogenic, atmospheric escape, and life processes. The VPL is validated using data derived from terrestrial planets within our own solar system. The VPL will be used to explore the plausible range of atmospheric compositions and globally-averaged spectra for extrasolar planets and for early Earth, and will improve our understanding of the effect of life on a planet's atmospheric spectrum and composition. The models will also be used to create a comprehensive spectral catalog to provide recommendations on the optimum wavelength range, spectral resolution, and instrument sensitivity required to characterize extrasolar terrestrial planets. Although developed by our team, the VPL is envisioned to be a comprehensive and flexible tool, which can be collaboratively used by the broader planetary science and astrobiology communities. This presentation will describe the project concept, the tasks involved, and will outline current progress to date. This work is funded by the NASA Astrobiology Institute.

Meadows, V. S.; Allen, M.; Brown, L.; Crisp, D.; Fijany, A.; Storrie-Lombardi, M.; Ustinov, E.; Velusamy, T.; Richardson, M.; Yung, Y.; Huntress, W.; DesMarais, D.; Zahnle, K.; Kasting, J.; Morrow, C.; Sleep, N.; Cohen, M.; Nealson, K.; Rye, R.; Coleman, M.

2001-11-01

5

The chemistry of extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

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

Bond, Jade Chantelle

2008-06-01

6

Stability of motion in extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

The discovery of extrasolar planets was and is a big challenge for astronomers because of the very different structure of these systems compared to our Solar System. In some of the extrasolar planetary systems (EPS) we can observe Jupiter-like planets very close to the central star -- even inside Mercury's orbit around the Sun. Many of them -- up to now 147 -- host planets on high eccentric orbits and have masses up to several masses of Jupiter. In this lecture we concentrate on the dynamical state of extrasolar planetary systems and report how planets in multiplanetary systems may stay on stable orbits although their orbits cross. The major part of this review is devoted to the results of investigations with regard to the possibility of EPSs to host terrestrial like planets (TP) in the habitable zone (HZ) around a star. For these -- still fictitious -- planets one can distinguish three principal types: 1st when the giant planet (GP) moves close to the star -- then a TP may move on stable orbits inside the HZ; 2nd when the GP moves far from the star, then we have the same situation like in our Solar System; 3rd when the GP itself moves inside the HZ, then a terrestrial satellite or a trojan planet may exist. Future space missions will show whether we may observe such interesting systems with terrestrial planets.

Dvorak, R.

2006-05-01

7

Understanding the Atmospheres of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

With the direct measurement of thermal emission (and perhaps soon reflected light) from the 'hot Jupiters', extrasolar planetary science is transitioning from discovery to characterization. Familiar attributes of solar system giant planet atmospheres, including hot stratospheres, clouds, redistribution of heat by winds, and perhaps even non-equilibrium molecular abundances and photochemical products have been recognized and modeled in some of these exotic atmospheres. Despite the fact that atmospheric dynamics undoubtedly plays a major role in controlling the thermal structures of these planets, one-dimensional radiative-convective equilibrium models are still exceptionally useful for understanding the baseline atmospheric physics and resultant thermal structure. Our group's apparently successful prediction of a hot stratosphere on planet HD 149026b is emblematic of the utility of 1D models. In the talk we will review our efforts to model the vertical structure of several of the hot Jupiters, focusing on the processes that play major roles in influencing the atmospheric chemical and temperature profiles. We will highlight processes (e.g., photochemistry acting on S-, P-, N-, and O- as well as C-bearing molecules) that are ripe for further modeling. Given that measurements of thermal emission in various Spitzer mid-infrared bands will soon be published for 10 planets, unprecedented opportunities for comparative exoplanetary science are now at hand.

Marley, Mark S.; Fortney, J.

2007-10-01

8

Multi-Aperture Imaging of Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

In this paper, we review the various ways in which an infrared stellar interferometer can be used to perform direct detection of extrasolar planetary systems. We first review the techniques based on classical stellar interferometry, where (complex) visibilities are measured, and then describe how higher dynamic ranges can be achieved with nulling interferometry. The application of nulling interferometry to the study of exozodiacal discs and extrasolar planets is then discussed and illustrated with a few examples.

Absil, O.

2010-10-01

9

Terrestrial Planet Formation in Extrasolar Planetary Systems  

NASA Astrophysics Data System (ADS)

The 47 UMa and Epsilon Eridani extrasolar planetary systems are among those that resemble the most our own solar system, with moderately massive planets (2.4 Mjup and 0.86 minimum mass) on relatively distant orbits (at 2.09 and 3.3 A.U.). It is thus natural to ask whether these systems can harbour terrestrial planets in their inner regions. We numerically investigate how the accretion process of such inner planets might have been affected by the presence of the detected massive external bodies. The crucial point is the timing of the giant planets's formation. We have investigated 2 different scenarios: 1) the perturbing planet was fully formed in the early phases of planetesimal accretion in the inner disk and 2) the giant planet reaches its final mass only later on when lunar-sized embryos already formed in the inner disk. For case 1) we focus on one crucial parameter driving the accretion process: the distribution of encounter velocities in the early inner disk, which is estimated using a deterministic code that takes into account the gravitational pull of external perturbers and the possible effect of gas drag. For case 2) a classical symplectic algorithm is used taking into account the mutual pull of protoplanetary embryos. The Epsilon Eridani system turns out to be very hostile to planetary accretion in the inner disk in the scenario 1) where the planet affects the initial phases of planetesimal accretion. The planet's high eccentricity (0.608) induces too large encounter velocities everywhere in the disk. Accretion of already formed large embryos is nevertheless possible in the a<0.8AU region. Planetesimal accretion is also strongly affected by an early formed giant planet in the 47 UMa system, with only a small inner region (a<0.3AU) being protected from too high impact velocities. The presence of gas drag could open a small chance for accretion, in particular for relatively large initial planetesimals. Nevertheless, as for Eps. Eridani, a later growth of the giant planet cannot prevent the accretion of lunar-sized embryos in the a<0.8AU area. Additional simulations are also in progress in order to investigate the perturbing effect of the second planet that has been recently discovered around 47 UMa orbiting at 3.73 AU from the central star. References: Thebault, P., Marzari, F., Scholl, H., ``Terrestrial planet formation in exoplanetary systems with a giant planet on an external orbit", submitted to A&A.

Thebault, P.; Marzari, F.; Scholl, H.

2001-11-01

10

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

11

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

12

The atmospheres of extrasolar planets  

NASA Astrophysics Data System (ADS)

The discovery of extrasolar planets, or "exoplanets" - i.e., planets orbiting around other stars - may be seen as the major discovery of astronomy over the past two decades. About twenty years ago, in 1992, the first discovery of a couple of planets around a pulsar was announced by A. Wolszczan and D. Frail.

Encrenaz, Thérèse

2014-01-01

13

Model Atmospheres and Spectra of Extrasolar Giant Planets  

NASA Astrophysics Data System (ADS)

Of the known extrasolar giant planets, five have estimated effective temperatures below ~ 800K. We report on the application of a radiative-convective equilibrium model, originally developed to study the atmospheres of the solar jovian planets, to these objects (70 Vir b, 47 UMa b, Gl 411 b, 55 Cnc c, and HD 114762 b). The deposition of incident radiation from the various primaries and the estimated internal heat fluxes are included in the models. Condensible species are removed and clouds inserted where appropriate. To span the likely range of planet masses, a variety of surface gravities are considered for each object. Preliminary results suggest that water clouds are present in all these atmospheres except for 70 Vir b and HD 114762 b. Water marginally condenses in the atmosphere of the former while that of the latter should be essentially cloud free. Condensation of trace species (e.g. NH_4Cl and NH_4H_2PO_4) may produce thin hazes in these two cases. Thermochemical equilibrium favors NH_3 and CH_4 in all these atmospheres while N_2 and CO are favored in the atmospheres of the close-orbit, hot companions like 51 Peg b and upsilon And b. The reflected visible and thermal infrared spectra of these objects are dominated by water, methane, and ammonia absorption. We find that the 4 to 5 microns window in CH_4 and H_2O opacity is open for all of these objects. Consequently, as in the case of Jupiter and the brown dwarf Gliese 229 B, the emitted flux in this region is significantly greater than the blackbody flux for the planetary effective temperature. Thus this spectral region is favorable for the detection of extrasolar giant planets and brown dwarfs. Comparison of model spectra with observations would constrain the vertical temperature and cloud structure of these new atmospheres. Burrows et al. (this meeting) use these and other models to examine the evolution of extrasolar giant planets.

Marley, M. S.; Guillot, T.; Saumon, D.; Freedman, R. S.

1996-09-01

14

Extrasolar Planetary Complex Biosphere Organization as Exemplified  

NASA Astrophysics Data System (ADS)

Planetary habitability has usually been defined with reference to the physiological tolerances of human beings, or, in a more general sense, in terms of a modelled planet's ability to retain liquid water (essential for life as we know it) on its surface for a few Gyr. Another way of investigating habitability is with regard to the global mode of biosphere organization. Every combination of stellar composition and main sequence luminosity evolution, planetary characteristics and history, and biosphere organisation is unique, and will have its own specific inner and outer Habitable Zone radii. We illustrate this with modelled equilibrium partial pressures of CO_2. Although, as pointed out by previous workers, plants' CO_2 compensation points (where respiration exactly balances photosynthetic production) are just a few p.p.m. for some species, plants in the real world need to grow, repair tissue loss, reproduce and colonise new areas as they become available. This means that Earth-type forest ecosystems will require CO_2 levels comparable to those of the present day Earth. Reductions in equilibrium CO_2 with progressievely higher insolation, will define different inner margins for the Forest H.Z. with different axial obliquities and continential configurations.

Heath, Martin; Williams, Darren; Doyle, Laurence

15

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

16

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

17

Portraits of distant worlds: Characterizing the atmospheres of extrasolar planets  

NASA Astrophysics Data System (ADS)

This thesis presents observational studies of the atmospheres of extrasolar planets, including the first longitudinal temperature profile of an extrasolar planet and the first detection of a temperature inversion in the atmosphere of an extrasolar planet. Our observations target four eclipsing gas-giant planets known as "hot Jupiters"; as a result of their short orbital periods we expect these planets to be tidally locked, with day-night circulation patterns and atmospheric chemistries that differ significantly from those of Jupiter. The first two chapters of this thesis describe infrared observations of the secondary eclipses of HD 209458b and TrES-4 with the Spitzer Space Telescope . By measuring the decrease in flux as the planet passes behind its parent star, we can characterize the infrared emission spectra of these planets and from that learn something about their dayside pressure-temperature profiles. Our observations reveal that these two planets have spectra with water bands in emission, requiring the presence of an atmospheric temperature inversion between 0.1 - 0.01 bars. The third chapter describes a ground-based search for thermal emission from TrES-1 using L -band grism spectroscopy with the NIRI instrument on Gemini North. Unlike Spitzer photometry, which is limited to broad bandpasses at these wavelengths, grism spectroscopy offers the opportunity to resolve specific features in the planetary emission spectrum. We find that our precision is limited by our ability to correct for time-varying slit losses from pointing drift and seeing changes, and place an upper limit on the depth of the planet's secondary eclipse in this band. The fourth and fifth chapters describe observations of the infrared phase variations of the hot Jupiter HD 189733b in the 8 and 24 mm Spitzer bands. By monitoring the changes in the brightness of this planet as it rotates around its parent star we can determine how much energy is circulated from the perpetually-illuminated day side around to the night side. We then invert these data to produce a longitudinal temperature profile for the planet, allowing us to resolve the locations of prominent hot and cold regions in the planet's atmosphere.

Knutson, Heather Ann

2009-06-01

18

Photochemistry in planetary atmospheres  

NASA Technical Reports Server (NTRS)

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 in the earth's ancient atmosphere are described, and problems of interest in the earth's present troposphere are discussed, including the down wind effect, plume interactions, aerosol nucleation and growth, acid rain, and the fate of terpenes. Temperature fluctuations in the four principal layers of the earth's atmosphere, predicted decreases in the ozone concentration as a function of time, and spectra of particles in the earth's upper atmosphere are also presented. Finally, the vertical structure of the Venus cloud system and the thermal structure of the Jovian planets are shown graphically.

Levine, J. S.; Graedel, T. E.

1981-01-01

19

Transiting extrasolar planetary candidates in the Galactic bulge.  

PubMed

More than 200 extrasolar planets have been discovered around relatively nearby stars, primarily through the Doppler line shifts owing to reflex motions of their host stars, and more recently through transits of some planets across the faces of the host stars. The detection of planets with the shortest known periods, 1.2-2.5 days, has mainly resulted from transit surveys which have generally targeted stars more massive than 0.75 M(o), where M(o) is the mass of the Sun. Here we report the results from a planetary transit search performed in a rich stellar field towards the Galactic bulge. We discovered 16 candidates with orbital periods between 0.4 and 4.2 days, five of which orbit stars of masses in the range 0.44-0.75 M(o). In two cases, radial-velocity measurements support the planetary nature of the companions. Five candidates have orbital periods below 1.0 day, constituting a new class of ultra-short-period planets, which occur only around stars of less than 0.88 M(o). This indicates that those orbiting very close to more-luminous stars might be evaporatively destroyed or that jovian planets around stars of lower mass might migrate to smaller radii. PMID:17024085

Sahu, Kailash C; Casertano, Stefano; Bond, Howard E; Valenti, Jeff; Smith, T Ed; Minniti, Dante; Zoccali, Manuela; Livio, Mario; Panagia, Nino; Piskunov, Nikolai; Brown, Thomas M; Brown, Timothy; Renzini, Alvio; Rich, R Michael; Clarkson, Will; Lubow, Stephen

2006-10-01

20

Habitable Extrasolar Planetary Systems; The Case of ? Cancri  

NASA Astrophysics Data System (ADS)

Having the largest number of extrasolar planets, a Neptune-mass object on a 2.8 days orbit, and an outer planet that orbits at 5.3 AU which is comparable to Jupiter's distance from the Sun, ? Cancri has become an interesting system for study of habitability. In this paper, we present the results of a study of the orbital evolution and dynamical stability of Earth-like planets in this system. Numerical integrations of the system, using the orbital parameters reported by McArthur et al. (2004), indicate that the system may not be stable. In search of stable planetary orbits, an extensive search of the parameter-space of the system was carried out, and a stable region was identified. Within this region, dynamical stability of an Earth-like planet in the habitable zone of the system was studied and two regions of stability were recognized. This research took place at the University of Hawaii's Institute for Astronomy during a Research Experience for Undergraduates (REU) internship funded by the National Science Foundation (NSF).

Cotto-Figueroa, D.; Haghighipour, N.

2005-12-01

21

Infrared spectra of planetary atmospheres  

NASA Technical Reports Server (NTRS)

The development of high spectral resolution and highly sensitive long infrared wavelength instruments is reported. This instrumentation is used to examine molecular lines in planetary atmospheres in enough detail to obtain new information about these atmospheres. Such information includes (1) pressure and temperature relations in planetary atmospheres, and (2) molecular and isotopic composition.

Townes, C. H.

1975-01-01

22

Radiative transfer in planetary atmospheres  

NASA Technical Reports Server (NTRS)

A wide range of topics are covered including the following: (1) the observational study of cometary comae via millimeter and radio spectroscopy; (2) observational and theoretical studies of planetary atmospheres at millimeter wavelengths; and (3) application of theoretical models of the reflection of light from solid surfaces to the study of planetary regoliths and planetary rings.

Schloerb, F. Peter

1991-01-01

23

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

NASA Astrophysics Data System (ADS)

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

Tajika, E.

2008-12-01

24

Impact erosion of planetary atmospheres  

Microsoft Academic Search

The problem of planetary atmospheres evolution due to impacts of large cosmic bodies was investigated by Ahrens, O'Keefe, Cameron, Hunten and others. These studies were focused mainly on the atmosphere growth under impact devolatilization and atmosphere losses due to escape of high velocity ejecta. Most of the results concerning atmosphere erosion were based on assumption that atmosphere itself does not

Valery Shuvalov

1999-01-01

25

Dissipation in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The net radiative entropy flux of a planet is negative because atmospheres absorb solar radiation at a higher temperature than the temperature at which they re-emit an equal amount of longwave radiation to space. If in the long term the entropy of an atmosphere is constant, the radiative entropy loss must be balanced by the entropy production associated with thermally direct heat transports and dissipation. Given estimates of the thermally direct sources of entropy production and the temperature at which dissipation occurs, this determines the rate of dissipation in an atmosphere. It is estimated that the entropy production due to dissipation in the atmospheres of Venus, Earth, Mars and Titan occurs at the rate, respectively, of about ?23, 29, 2, and ?4 mW m-2 K-1. If the dissipation in Earth’s atmosphere occurs between temperatures of 250 K and 288 K the dissipation rate must lie between 7.3 and 8.4 W m- 2, consistent with other recent estimates. The terrestrial heat engine operates with an efficiency of about 60% of the Carnot efficiency. Sources of dissipation in planetary atmospheres are highly uncertain, even for Earth. For Earth, frictional dissipation in rainfall is comparable to the turbulent dissipation of kinetic energy. Rainfall might also be a significant source of dissipation on Titan but it is not likely to be important for Mars or Venus. The breaking of upward propagating internal gravity waves generated by convection and flow over the surface topography is another source of dissipation and is possibly dominant on Venus.

Schubert, Gerald; Mitchell, J.

2012-10-01

26

Studies of Tenuous Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

In order to understand the physical and chemical processes which produce the tenuous planetary and planetary satellite (upper) atmospheres through interactions with their particle, field, and radiation environs, it is necessary to analyze remotely observed and spacecraft data with physically meaningful models. With this in mind, we have undertaken a coupled program of theoretical modeling and complementary data analysis regarding the global distributions of neutral and ionized gases in, and escape from, tenuous planetary atmospheres of Io and Europa. The theoretical models developed will have further applications to other tenuous atmospheres such as that of Pluto and Titan or the upper atmospheres of the terrestrial planets.

Combi, Michael R.; Beebe, Reta (Technical Monitor)

2001-01-01

27

The Astronomical Detection of Biosignatures on Extrasolar Terrestrial Planets: The Virtual Planetary Laboratory  

Microsoft Academic Search

NASA and ESA are designing space-based observatories to detect and characterize extrasolar terrestrial planets. Because these systems will initially resolve planets only as point sources, we must learn to distinguish habitable worlds and to discriminate between planets with and without life based entirely on the interpretation of remote sensing observations of disk-averaged spectra. The Virtual Planetary Laboratory (VPL) is being

D. Crisp; V. S. Meadows; C. D. Parkinson; M. A. Allen; T. Velusami; G. Tinetti; R. Rye; K. Krelove

2003-01-01

28

Extrasolar planets and false atmospheric biosignatures: The role of micrometeoroids  

NASA Astrophysics Data System (ADS)

The coexistence of oxygen and a reduced gas such as methane in the atmosphere of an extrasolar planet is considered to be strong evidence for the presence of a biosphere. Proposed spacecraft such as Darwin or Terrestrial Planet Finder are designed to be capable of spectroscopically characterising the atmospheres of exoplanets, detecting chemical disequilibrium indicative of life. However, methane can be produced by various abiological mechanisms, including the ablation of carbonaceous micrometeoroids upon atmospheric entry, and it is possible that extrasolar planets in dust-rich systems might receive enough micrometeoroidal infall to produce a false atmospheric biosignature. Here, we review the production of methane from carbonaceous meteoroids upon atmospheric ablation in our solar system and discuss its application to extrasolar planets. The current paucity of data regarding dust densities in systems possessing terrestrial planets in the habitable zones of their stars makes firm conclusions difficult. However, the data suggest that only very young systems possessing very dense debris disks, or systems undergoing reorganisation similar to the Late Heavy Bombardment in our early solar system, would be capable of producing sufficient methane to be mistaken for an atmospheric biosignature.

Court, Richard W.; Sephton, Mark A.

2012-12-01

29

The chemistry of planetary atmospheres  

NASA Technical Reports Server (NTRS)

Present knowledge concerning the chemistry of planetary atmospheres is reviewed along with the theories which attempt to explain observational data. The known gross atmospheric compositions of the terrestrial and giant planets are listed, differences between the atmospheres of earth and Venus are discussed, and the atmospheres of the giant planets are described. The origin and evolution of the atmospheres of earth, Venus, Mars, Jupiter, Saturn, and Uranus are outlined, and chemical processes in the atmospheres are examined, particularly cloud formation. The question of organic synthesis and evolution in the reducing atmospheres of the giant planets is considered. It is noted that laboratory work on the individual chemical processes and reactions involved in the evolution of organic compounds in planetary atmospheres, comets, and interstellar space points to the inevitability of organic-compound synthesis in all these situations and to the pervasiveness of organic chemistry throughout the universe.

Huntress, W. T., Jr.

1976-01-01

30

Extra-Solar Planetary Imager (ESPI) for Space Based Jovian Planetary Detection  

NASA Technical Reports Server (NTRS)

We report on out Extra-Solar Planetary Imager (ESPI) study for a recent Midex (NASA Medium Class Explorer Mission) proposal. Proposed for ESPI was a 1.5 x 1.5 square meter Jacquinot apodized square aperture telescope. The combination of apodization and a square aperture telescope significantly reduces the diffracted light from a bright central source over much of the telescope focal plane. As a result, observations of very faint astronomical objects next to bright sources with angular separations as small as 0.32 arcseconds become possible. This permits a sensitive search for exo-planets in reflected light. The system is capable of detecting a Jupiter-like planet in a relatively long-period orbit around as many as 160 to 175 stars with a signal-to-noise ratio greater than 5 in observations lasting maximally 100 hours per star. We discuss the effects of wavefront error, mirror speckle, pointing error and signal-to-noise issues, as well as the scalability of our ESPI study with respect to NASA's Terrestrial Planet Finder mission.

Lyon, Rick G.; Melnick, Gary J.; Nisenson, Peter; Papaliolios, Costa; Ridgeway, Steve; Friedman, Edward; Gezari, Dan Y.; Harwit, Martin; Graf, Paul

2002-01-01

31

Planetary Surface-Atmosphere Interactions  

NASA Astrophysics Data System (ADS)

Planetary bodies having an accessible solid surface and significant atmosphere, such as Earth, Mars, Venus, Titan, share common phenomenology. Specifically wind induced transport of surface materials, subsequent erosion, the generation and transport of solid aerosols which leads both to chemical and electrostatic interaction with the atmosphere. How these processes affect the evolution of the atmosphere and surface will be discussed in the context of general planetology and the latest laboratory studies will be presented.

Merrison, J. P.; Bak, E.; Finster, K.; Gunnlaugsson, H. P.; Holstein-Rathlou, C.; Knak Jensen, S.; Nørnberg, P.

2013-09-01

32

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

Microsoft Academic Search

We are conducting a planet search survey with HARPS since seven years. The volume-limited stellar sample includes all F2 to M0 main-sequence stars within 57.5 pc, where extrasolar planetary signatures are systematically searched for with the radial-velocity technics. In this paper, we report the discovery of new substellar companions of seven main-sequence stars and one giant star, detected through multiple

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

2011-01-01

33

Clouds in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

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

West, R.

1999-01-01

34

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

35

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

36

Radial Velocity Detection of Extra-Solar Planetary Systems  

NASA Technical Reports Server (NTRS)

This NASA Origins Program grant supported four closely related research programs at The University of Texas at Austin: 1) The McDonald Observatory Planetary Search (MOPS) Program, using the McDonald Observatory 2.7m Harlan Smith telescope and its 2dcoude spectrometer, 2) A high-precision radial-velocity survey of Hyades dwarfs, using the Keck telescope and its HIRES spectrograph, 3) A program at McDonald Observatory to obtain spectra of the parent stars of planetary systems at R = 210,000, and 4) the start of high precision radial velocity surveys using the Hobby-Eberly Telescope. The most important results from NASA support of these research programs are described. A list of all papers published under support of this grant is included at the end.

Cochran, William D.

2004-01-01

37

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

38

Planetary Atmospheric Flow  

NASA Technical Reports Server (NTRS)

This drawing depicts one set of flow patterns simulated in the Geophysical Fluid Flow Cell (GFFC) that flew on two Spacelab missions. Silicone oil served as the atmosphere around a rotating steel hemisphere (dotted circle) and an electrostatic field pulled the oil inward to mimic gravity's effects during the experiments. The GFFC thus produced flow patterns that simulated conditions inside the atmospheres of Jupiter and the Sun and other stars. The principal investigator was John Hart of the University of Colorado at Boulder. It was managed by NASA's Marshall Space Flight Center (MSFC). An Acrobat PDF copy of this drawing is available at http://microgravity.nasa.gov/gallery. (Credit: NASA/Marshall Space Flight Center)

1995-01-01

39

The search for extra-solar planetary systems.  

PubMed

I review the observational evidence for planetary systems around nearby stars and, using our own solar system as a guide, assess the stringent requirements that new searches need to meet in order to unambiguously establish the presence of another planetary system. Basically, these requirements are: 1 milliarcsecond or better positional accuracy for astrometric techniques, 9 orders of magnitude or better star to planet luminosity ratio discrimination at 0.5 to 1" separation in the optical for direct imaging techniques, 10 meters sec-1 or better radial velocity accuracy for reflex motion techniques and +/-1% or better brightness fluctuation accuracy for planet/star occultation measurements. The astrometric accuracy is in reach of HST, direct imaging will require much larger telescopes and/or a 50 times smoother mirror than HST while the reflex motion and occultation techniques best performed on the ground are just becoming viable and promise exciting new discoveries. On the other band, new indirect evidence on the existence of other planetary systems also comes from the observation of large dusty disks around nearby main sequence stars not too dissimilar from our sun. In one particular case, that of Beta Pictoris, a flattened disk seen nearly edge-on has been imaged in the optical and near IR down to almost 70 AU of the star. It probably represents a young planetary system in its clearing out phase as planetesimals collide, erode and are swept out of the inner system by radiation pressure. The hypothesized Kuiper belt around our solar system may be the analogous structure in a later evolutionary stage. Features of this type have been detected in the far IR and sub-millimeter wavelength regions around 50-100 nearby main sequence and pre-main sequence stars. I discuss a battery of new accurate observations planned in the near future of these objects some of which may actually harbour planets or planetesimals that will certainly dramatically improve our knowledge of planetary system formation processes and our peculiar position in this scheme. PMID:11538135

Paresce, F

1992-01-01

40

Impact erosion of planetary atmospheres  

NASA Astrophysics Data System (ADS)

The problem of planetary atmospheres evolution due to impacts of large cosmic bodies was investigated by Ahrens, O'Keefe, Cameron, Hunten and others. These studies were focused mainly on the atmosphere growth under impact devolatilization and atmosphere losses due to escape of high velocity ejecta. Most of the results concerning atmosphere erosion were based on assumption that atmosphere itself does not influence significantly on the ejecta evolution. However more detailed investigations show that atmospheric drag is important at least for 1-10km impactors. From the other hand the theory of large explosions in an exponential atmosphere is not applicable in the case under consideration because of the influence of a trail created during the body flight through the atmosphere. In the present study the problem of 1-10km asteroid impacts against the Earth is investigated with the use of multi-material hydrocode SOVA. This code is similar to the widely used CTH system and allows to model all stages of the impact (penetration into the atmosphere, collision with the ground surface covered by water basin, ejecta evolution). The air mass ejected from each altitude depending on impactor size and velocity is determined. Apart from the impacts into the present-day atmosphere, the erosion of the dense Proto-Atmosphere is also considered.

Shuvalov, Valery

1999-06-01

41

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

Microsoft Academic Search

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

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

2010-01-01

42

Prospecting transit duration variations in extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

Context. Transiting planetary systems allow us to extract geometrical information, e.g., the angle ? between the orbital angular momentum and the stellar spin, that can be used to discriminate among different formation and evolutionary scenarios. This angle is constrained by means of the Rossiter-McLaughlin effect observed on radial velocity and can be subject to large uncertainties, especially for hot stars (Teff > 6250 K). It is thus interesting to have an alternative method to constrain the value of the obliquity ? and to detect companions that might have disturbed the orbit of the planet. Aims: We show how the long-term variations in the transit duration (TDV) can be used to constrain the obliquity of the stellar rotation axis. Our calculations may also be used to put an upper limit on the contribution of geometrical effects to the TDVs, thus allowing us to indirectly infer the presence of additional companions. Methods: We introduce a simple theory to describe the secular variations in the orbital elements and their effects on the TDVs with a general formulation valid for both oblique and eccentric systems. Parameters or orbital elements that cannot be directly measured, such as the longitude of the ascending node of the orbit, are avoided thus allowing us to perform a straightforward application. Results: We compute the expected TDVs for the presently known transiting systems, adopting their parameters found in the literature. Considering the capabilities of the present or next generation space-borne telescopes, we point out the systems that could be readily observed and discuss the constraints derivable on their fundamental parameters. Conclusions: Measured TDVs can be used to constrain the obliquity of the stars (and possibly of the planets in systems younger than 10-100 Myr), giving information about the formation scenarios, the strength of the tidal coupling, and the internal structure of both the stars and the planets. Moreover, they can provide an indirect indication of other bodies, even with a mass comparable with that of the Earth, because they give rise to additional contributions to the nodal precession.

Damiani, C.; Lanza, A. F.

2011-11-01

43

Planetary Atmospheres at High Resolution  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

44

Rocky Extrasolar Planetary Compositions Derived from Externally Polluted White Dwarfs  

NASA Astrophysics Data System (ADS)

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 ~1022 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 ~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.; Koester, D.; Zuckerman, B.

2011-11-01

45

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

46

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

47

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

NASA Astrophysics Data System (ADS)

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 inspite 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 nounambiguousproof 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.

48

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

49

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

50

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

51

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

52

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

53

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

NASA Astrophysics Data System (ADS)

Recent results have shown that many of the known extrasolar planetary systems contain regions that are stable for both Earth-mass and Saturn-mass planets. Here we simulate the formation of terrestrial planets in four planetary systems, 55 Cancri, HD 38529, HD 37124, and HD 74156, under the assumption that these systems of giant planets are complete and that their orbits are well determined. Assuming that the giant planets formed and migrated quickly, 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 M? and, in some cases, substantial water content 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.

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

2006-06-01

54

Extra-solar Planetary Systems Tend to be near a Secular Separatrix  

NASA Astrophysics Data System (ADS)

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 between libration and circulation. (55 Cnc is complicated by a 3:1 mean-motion commensurability.) A review of the basics of secular theory provides insight into this behavior, correcting misconceptions about the definition of secular resonance that have propagated in the literature of extra-solar planetary systems: Resonance is not synonymous with libration, and is not a commensurability of eigenfrequencies. Contrary to earlier reports, what makes these systems special is not that they are librating (they may not be) or that they are in resonance (they are not), but that each is so close to its separatrix. We have evaluated the behavior of the near-separatrix systems with updated orbital elements and compared both analytical and numerical results. The systems are so close to the separatrix that first-order theory analytic secular theory cannot reliably distinguish between circulation and libration. Similarly, uncertainty in observational orbit determination is great enough that, even with numerical integration, the libration state is uncertain. These near-separatrix systems are so common that they suggest that some physical process of planet formation or dynamical evolution may tend to set up systems near the separatrix. Explanations based on an impulsive increase in the eccentricity of one planet from near zero are promising, but some issues are unresolved. A successful explanation must explain why this remarkable dynamical condition is so common.

Greenberg, R.; Barnes, R.

2005-08-01

55

Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Participants; Preface; Acknowledgements; 1. Extrasolar planet detection methods Laurance R. Doyle; 2. Statistical properties of exoplanets Stéphane Udry; 3. Characterizing extrasolar planets Timothy M. Brown; 4. From clouds to planet systems: formation and evolution of stars and planets Günther Wuchterl; 5. Abundances in stars with extrasolar planetary systems Garik Israelian; 6. Brown dwarfs: the bridge between stars and planets Rafael Rebolo; 7. The perspective: a panorama of the Solar System Agustín Sánchez-Lavega; 8. Habitable planets around the Sun and other stars James F. Kasting; 9. Biomarkers of extrasolar planets and their observability Franck Selsis, Jimmy Paillet and France Allard; Index.

Deeg, Hans; Belmonte, Juan Antonio; Aparicio, Antonio

2012-03-01

56

Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Participants; Preface; Acknowledgements; 1. Extrasolar planet detection methods Laurance R. Doyle; 2. Statistical properties of exoplanets Stéphane Udry; 3. Characterizing extrasolar planets Timothy M. Brown; 4. From clouds to planet systems: formation and evolution of stars and planets Günther Wuchterl; 5. Abundances in stars with extrasolar planetary systems Garik Israelian; 6. Brown dwarfs: the bridge between stars and planets Rafael Rebolo; 7. The perspective: a panorama of the Solar System Agustín Sánchez-Lavega; 8. Habitable planets around the Sun and other stars James F. Kasting; 9. Biomarkers of extrasolar planets and their observability Franck Selsis, Jimmy Paillet and France Allard; Index.

Deeg, Hans; Belmonte, Juan Antonio; Aparicio, Antonio

2007-10-01

57

Balloon Measurements of Winds in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

58

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

59

Target of Opportunity: New Observable Transiting Extrasolar Planets  

Microsoft Academic Search

We propose a Legacy Target of Opportunity (TOO) program to observe transits and eclipses of new extrasolar planets. These measurements provide the most accurate planetary radii and the only emission fluxes possible with current telescopes for extrasolar planets; the next opportunity for the latter is with JWST. Radii and band fluxes constrain models of composition, chemistry, and atmospheric dynamics. They

Joseph Harrington; Drake Deming; Debra Fischer; L. Jeremy Richardson; Sara Seager

2006-01-01

60

The Earth as an extrasolar transiting planet. Earth's atmospheric composition and thickness revealed by Lunar eclipse observations  

Microsoft Academic Search

Context. An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Aims: Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first important step for future comparisons. We have completed observations of the Earth during a lunar eclipse, a unique situation similar to

Alfred Vidal-Madjar; Luc Arnold; David Ehrenreich; Roger Ferlet; A. Lecavelier Des Etangs; François Bouchy; Damien Segransan; Isabelle Boisse; Guillaume Hébrard; Claire Moutou; J.-M. Désert; D. K. Sing; Rémy Cabanac; Christian Nitschelm; Xavier Bonfils; Xavier Delfosse; Morgan Desort; R. F. Diaz; Anne Eggenberger; Thierry Forveille; A.-M. Lagrange; Christophe Lovis; Francesco Pepe; Christian Perrier; Frédéric Pont; N. C. Santos; Stéphane Udry

2010-01-01

61

Planetary atmospheres: Microwave spectroscopic and space physics  

NASA Technical Reports Server (NTRS)

Ground-based spectroscopic observations of isotopes of CO in the atmosphere of Mars, Venus, and Titan were collected over the 1982-1990 period. These observations were analyzed to obtain information on the photochemistry, dynamics, and thermal profiles of these planetary atmospheres. In the cases of the mesosphere (80-100 km altitude) of Venus and the lower atmosphere (0-70 km altitude) of Mars, the primary conclusion of this research is that significant interannual variation in the global, thermal, and compositional structures of these atmospheres occur over 10 year periods. The Titan studies have focussed on pinning down the true atmosphere CO abundance. A more detailed summary of the results for each of these planetary atmospheres is provided.

Clancy, R. Todd

1990-01-01

62

Work on Planetary Atmospheres and Planetary Atmosphere Probes  

Microsoft Academic Search

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

Alvin Seiff; Peter Lester

1999-01-01

63

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

64

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 ESA'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.

David J. Des Marais; Martin Harwit; Kenneth Jucks; James Kasting; Douglas Lin; Jonathan Lunine; Jean Schneider; Sara Seager; Wesley Traubc; Neville Woolf

2002-01-01

65

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

66

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

PubMed

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

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

2009-09-01

67

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

68

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

69

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

70

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

71

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

72

Atmospheres From Very Low-Mass Stars to Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Within the next few years, several instruments aiming at imaging extrasolar planets will see first light. In parallel, low mass planets are being searched around red dwarfs which offer more favorable conditions - both for radial velocity detection and transit studies - than solar-type stars. We review recent advancements in modeling the stellar to substellar transition. The revised solar oxygen abundances and cloud models allow to reproduce the photometric and spectroscopic properties of this transition to a degree never achieved before, but problems remain at the stellar-brown dwarf transition typical of the Teff range of characterizable exoplanets.

Allard, F.; Homeier, D.; Freytag, B.; Sharp, C. M.

2012-11-01

73

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

74

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

75

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

76

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

77

Extrasolar planets  

PubMed Central

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

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

2000-01-01

78

Sputtering Contribution to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

We have measured the sputtering of specific species during ion irradiation of water ice, labradorite, albite, anorthoclase, and olivine targets, to understand the importance of sputtering in the generation of atmospheres around icy satellites of the outer solar system by magnetospheric ions, and around the Moon and Mercury by the Solar wind. We use mass spectrometry in ultrahigh vacuum to measure sputtered species and gas evolved during post-irradiation heating to identify chemical species formed by ion implantation. We will discuss the formation of NO and other molecules in the Saturnian system that may be detectable by Cassini, and the relative importance of different mechanism that lead to the formation of Na atmospheres around the Moon and Mercury.

Baragiola, R. A.; Dukes, C. A.; Chang, W.; Teolis, B. D.; Raut, U.; Vidal, R. A.

2004-05-01

79

Space Weather and Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Space weather is the rubric applied to phenomena that effect the near-Earth space environment and, more importantly, to the response of that environment to external inputs. Space weather at Earth is important in terms of the root cause of some satellite anomalies, effects on radio communications, and changes in atmospheric drag experienced by satellites. Many of these effects are observed at other planets and can rightly be included in any discusion of space weather. As we consider the next steps in the exploration of other planets we need to be aware that space weather will shape how and when we can safely go to other planets and determine to some degree the scope and implementation of the design of missions to these planets. Mars is, after the Moon, the next target for human exploration. The atmosphere of Mars and its interaction with the changing solar system environment is the main subject of this oveview paper. The Mars atmosphere and ionosphere are fascinating - and they represent a true test of the predictive capabilities of our first principles models. There will be brief excursions into the the issues that need to addressed for a Venus mission as well as some consideration of the open questions at Europa and Titan - possible longer-term targets for robotic exploration.

Paxton, L. J.

2006-05-01

80

Photochemistry of planetary atmospheres. [Mars atmospheric composition  

NASA Technical Reports Server (NTRS)

The atmospheric composition of Mars is presented, and the applicability of laboratory data on CO2 absorption cross sections and quantum yields of dissociation is discussed. A summary and critical evaluation are presented on the various mechanisms proposed for converting the photodissociation products CO and O2 back to CO2.

Stief, L. J.

1973-01-01

81

Application of MODTRAN to Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

MODTRAN(TM) is a widely used radiative-transfer (RT) code for computing the transmission, emission and scattering in the Earth's atmosphere. However, the RT algorithms used in MODTRAN(TM) are generally applicable to any layered atmosphere, and, in principle, can be applied to any planetary atmosphere. The primary required modification required for this application is the development of the appropriate spectral properties data bases for the particular species associated with a given planetary atmosphere. We will show the application of MODTRAN(TM) to Neptune for which the primary atmospheric species are H2, CH4, C2H6, and C2H2. For the carbon-containing species, we have developed molecular band model parameters, and for H2 we have utilized continuum parameters computed by others. Additionally, we have developed a new cloud model to account for the CH4 clouds which form in the extremely cold upper atmosphere of Neptune. We will show calculations both for the solar reflective spectral region and the thermal IR emission region, ~0.4-20 microns. Comparisons will be made with archival data.

Bernstein, L.; Sundberg, R.; Singer-Berk, A.

82

The greenhouse effect of planetary atmospheres  

NASA Astrophysics Data System (ADS)

Consideration is given to the components of the greenhouse effect in planetary atmospheres. A means for calculating the atmospheric greenhouse effect, defined as the difference between planetary surface temperature and brightness temperature, is presented which is based on a one-dimensional model of radiative convective equilibrium. The contributions of water vapor, CO2 and ozone to the greenhouse effect of the earth are pointed out, and the evolution of the earth greenhouse effect is traced in relation to the evolution of the atmosphere. Calculations are then presented of the potential impacts on the atmosphere of anthropogenic gaseous and aerosol components, and it is pointed out that the cloud-generated effect may prevail over the effect of CO2 warming in the near future. Consideration is then given to the greenhouse effects in the atmospheres of Venus, Mars and Jupiter as calculated on the basis of atmospheric structural and radiative models, with particular emphasis on the contributions of Venus clouds and Martian dust, and the conditions favoring an antigreenhouse effect.

Kondratev, K. Ia.; Moskalenko, N. I.

1980-08-01

83

Planetary atmospheric physics and solar physics research  

NASA Technical Reports Server (NTRS)

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

1973-01-01

84

Tools for discovering and characterizing extrasolar planets  

Microsoft Academic Search

Among the group of extrasolar planets, transiting planets provide a great opportunity to obtain direct measurements for the basic physical properties, such as mass and radius of these objects. These planets are therefore highly important in the understanding of the evolution and formation of planetary systems: from the observations of photometric transits, the interior structure of the planet and atmospheric

András Pál

2009-01-01

85

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

86

Origin and evolution of planetary atmospheres  

NASA Technical Reports Server (NTRS)

This report concerns several research tasks related to the origin and evolution of planetary atmospheres and the large-scale distribution of volatile elements in the Solar System. These tasks and their present status are as follows: (1) we have conducted an analysis of the volatility and condensation behavior of compounds of iron, aluminum, and phosphorus in the atmosphere of Venus in response to publish interpretations of the Soviet Venera probe XRF experiment data, to investigate the chemistry of volcanic gases, injection of volatiles by cometary and asteroidal impactors, and reactions in the troposphere; (2) we have completed and are now writing up our research on condensation-accretion modeling of the terrestrial planets; (3) we have laid the groundwork for a detailed study of the effects of water transport in the solar nebula on the bulk composition, oxidation state, and volatile content of preplanetary solids; (4) we have completed an extensive laboratory study of cryovolcanic materials in the outer solar system; (5) we have begun to study the impact erosion and shock alteration of the atmosphere of Mars resulting from cometary and asteroidal bombardment; and (6) we have developed a new Monte Carlo model of the cometary and asteroidal bombardment flux on the terrestrial planets, including all relevant chemical and physical processes associated with atmospheric entry and impact, to assess both the hazards posed by this bombardment to life on Earth and the degree of cross-correlation between the various phenomena (NO(x) production, explosive yield, crater production, iridium signature, etc.) that characterize this bombardment. The purpose of these investigations has been to contribute to the developing understanding of both the dynamics of long-term planetary atmosphere evolution and the short-term stability of planetary surface environments.

Lewis, John S.

1992-01-01

87

Origin and evolution of planetary and satellite atmospheres  

SciTech Connect

The present volume on the origin and evolution of planet and satellite atmospheres discusses the chemistry of interstellar gas and grains, planetary accretion, cometary composition, the inventories of asteroid volatiles, key similarities and differences among the terrestrial planets' atmospheric compositions, and planets' atmospheric escape and water loss. Also discussed are planetary atmosphere-planetary interior evolutionary coupling, the atmospheric composition of the outer planets, the structure and composition of giant planet interiors, the tenuous atmosphere of Io, the sources of the atmospheres of the outer solar system's satellites, the present state and chemical evolution of the Titan, Triton, and Pluto atmospheres, and the thermal structure and heat balance of the outer planets.

Atreya, S.K.; Pollack, J.B.; Matthews, M.S.

1989-01-01

88

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

PubMed

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

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

2007-02-01

89

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

90

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

Microsoft Academic Search

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

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

91

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

NASA Astrophysics Data System (ADS)

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 HD 209458b-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) a motion-associated temperature field, whose detectability and variability depend on the strength of the net heating rate and the global rms 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.

Cho, James Y.-K.; Menou, Kristen; Hansen, Bradley M. S.; Seager, Sara

2008-03-01

92

Optical efficiencies of lightning in planetary atmospheres.  

PubMed

Spacecraft observations show that the presence of lightning activity is not confined to the terrestrial atmosphere, but is also found in the atmospheres of Venus, Jupiter and Saturn. Lightning activity may also occur in Titan's thick atmosphere. Calculations show that lightning produces a significant fraction of the nitric oxide that reacts with the ozone and chlorine compounds in the terrestrial stratosphere. In the atmosphere of the primordial Earth, lightning could have been the major source of many of the molecules required for the formation of life. To determine the effects of lightning activity in the atmospheres of other planets from spacecraft images requires a knowledge of the optical properties of the lightning discharge. Here we report the first simulations of lightning in planetary atmospheres by laser-induced plasmas. These simulations show that the fraction of the energy in lightning discharge channels that is radiated in the visible spectrum is similar for Earth, Venus and Titan, but quite different for Jupiter. One implication of our results is that the amount of trace gases produced by lightning in the jovian atmosphere must be larger than previously estimated. PMID:11540880

Borucki, W J; McKay, C P

1987-08-01

93

Undergraduate Astronomy Laboratory Software: Planetary Atmosphere Evolution  

NASA Astrophysics Data System (ADS)

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

Luttermoser, D. G.

1999-12-01

94

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.

95

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

96

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

97

Detection techniques for tenuous planetary atmospheres  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

98

Aerosols in Planetary Atmospheres: Cycle 1 Observations  

NASA Astrophysics Data System (ADS)

Our goal is to determine the vertical and horizontal distribution and optical properties of stratospheric aerosols in the atmospheres of the outer planets Jupiter and Saturn to constrain models of their photochemical production, vertical and horizontal transport, absorption of solar and thermal radiation, and role in forcing atmospheric dynamics. Observations needed for this purpose include photometry which 1) spans a wide range of wavelengths to permit discrimination in particle size; 2) refers to limited pressure ranges; 3) tracks specific planetary features. Carefully timed HST WFPC successive telescope orbits permit a wide spread in airmass factors at many planetary longitudes for good vertical discrimination both by the 8888A methane band at long wavelengths and by Rayleigh scattering at short wavelengths. These images at wavelengths separated by a factor >3 also provides good discrimination in the size of small stratospheric aerosols. No other technique is available which can provide either the simultaneous wide wavelength coverage or the spatial resolution to use center-to-limb variations to limit the vertical region probed on the outer planets. In addition, repeating such observations yearly permits temporal changes to be monitored for a new understanding of seasonal variations and the role of the solar cycle in these stratospheres.

Tomasko, Martin

1991-07-01

99

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

NASA Astrophysics Data System (ADS)

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

Triaud, A. H. M. J.

2011-08-01

100

A stability limit for the atmospheres of giant extrasolar planets.  

PubMed

Recent observations of the planet HD209458b indicate that it is surrounded by an expanded atmosphere of atomic hydrogen that is escaping hydrodynamically. Theoretically, it has been shown that such escape is possible at least inside an orbit of 0.1 au (refs 4 and 5), and also that H3+ ions play a crucial role in cooling the upper atmosphere. Jupiter's atmosphere is stable, so somewhere between 5 and 0.1 au there must be a crossover between stability and instability. Here we show that there is a sharp breakdown in atmospheric stability between 0.14 and 0.16 au for a Jupiter-like planet orbiting a solar-type star. These results are in contrast to earlier modelling that implied much higher thermospheric temperatures and more significant evaporation farther from the star. (We use a three-dimensional, time-dependent coupled thermosphere-ionosphere model and properly include cooling by H3+ ions, allowing us to model globally the redistribution of heat and changes in molecular composition.) Between 0.2 and 0.16 au cooling by H3+ ions balances heating by the star, but inside 0.16 au molecular hydrogen dissociates thermally, suppressing the formation of H3+ and effectively shutting down that mode of cooling. PMID:18064005

Koskinen, Tommi T; Aylward, Alan D; Miller, Steve

2007-12-01

101

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

102

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

Microsoft Academic Search

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

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

1996-01-01

103

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

104

Planetary Mass Spectrometry: From Atmospheres to the Solar Wind  

Microsoft Academic Search

Measurement of the bulk composition and isotopic fractionation of planetary atmospheres yields essential information about their origin, evolution and eventual loss. In particular, measurements from below the homopause out through the exosphere to the solar wind (e.g., at Mars and Venus) or to a planetary magnetosphere (e.g., at Titan) are essential to understanding processes driving atmospheric evolution and loss. Over

D. T. Young; J. H. Waite; A. de Los Santos; G. P. Miller; J. L. Burch; P. Wilson; K. S. Pickens; T. G. Brockwell; R. Gomez; J. Grimes; E. L. Patrick; A. Richter; J. M. Roberts; B. D. Teolis; J. H. Westlake

2008-01-01

105

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

106

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

107

Exploring Hot Neptune Atmospheres  

Microsoft Academic Search

The first transiting 'hot Neptune'' GJ 436b inhabits an entirely new region of phase space for extrasolar planetary atmospheres. This relatively cool, low-mass object should be the first transiting extrasolar planet to sport a methane-rich atmosphere. Like Uranus and Neptune it may also have an atmosphere highly enriched in heavy elements. Our experience with the complex atmospheres of the known

Jonathan Fortney; Mark Marley; Didier Saumon

2008-01-01

108

Evaporation of extrasolar planets  

Microsoft Academic Search

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

A. Lecavelier Des Etangs

2010-01-01

109

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

110

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

111

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

NASA Astrophysics Data System (ADS)

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

Line, Michael R.; Yung, Yuk L.

2013-12-01

112

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

Microsoft Academic Search

The Radio Science Atmospheric Occultation (RSAO) technique has a history of producing excellent science results for a wide range of denser planetary atmospheres. Overwhelmingly, the specific technique used so far has been the ``downlink\\

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

2003-01-01

113

Quasi-stationary planetary waves and temperature reference atmosphere  

Microsoft Academic Search

Summary A middle atmosphere temperature reference model from satellite measurements has recently been proposed. Comparisons are made with the Air Force Reference Atmosphere and the Reference model from satellite data. Large temperature deviations between two models at 60 N, 90 W in winter are found and the role of quasi-stationary planetary waves for these deviations is dicussed.

C. Varotsos

1987-01-01

114

Hadley cells in planetary atmospheres without a condensible component  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

115

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

NASA Astrophysics Data System (ADS)

The Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE 36.225 UG) was designed to directly image the exozodiacal dust disk of ? Eridani (K2V, 3.22 pc) down to an inner radius of 1.5 AU. PICTURE carried four key enabling technologies on board a NASA sounding rocket at 4:25 MDT on October 8th, 2011: a 0.5 m light-weight primary mirror (4.5 kg), a visible nulling coronagraph (VNC) (600-750 nm), a 32x32 element MEMS deformable mirror and a milliarcsecond-class fine pointing system. Unfortunately, due to a telemetry failure, the PICTURE mission did not achieve scientific success. Nonetheless, this flight validated the flight-worthiness of the lightweight primary and the VNC. The fine pointing system, a key requirement for future planet-imaging missions, demonstrated 5.1 mas RMS in-flight pointing stability. We describe the experiment, its subsystems and flight results. We outline the challenges we faced in developing this complex payload and our technical approaches.

Mendillo, Christopher B.; Hicks, Brian A.; Cook, Timothy A.; Bifano, Thomas G.; Content, David A.; Lane, Benjamin F.; Levine, B. Martin; Rabin, Douglas; Rao, Shanti R.; Samuele, Rocco; Schmidtlin, Edouard; Shao, Michael; Wallace, J. Kent; Chakrabarti, Supriya

2012-09-01

116

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

117

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

118

Formation of Charge Layers in the Planetary Atmospheres  

Microsoft Academic Search

This section focuses on the physical phenomena, leading to large-scale space-charge and electric field generation (electric dynamo) in the planetary atmospheres, and ways of their theoretical description. The main attention is paid to charge-layer formation in atmospheres. Under terrestrial conditions, a problem of charge-layer formation in the atmosphere is important from the viewpoint of both thunderstorm and fair weather electricity.

Evgeny A. Mareev

2008-01-01

119

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

120

Studying Extrasolar Planets with WFIRST  

NASA Astrophysics Data System (ADS)

The WFIRST mission will be a powerful tool for studying extrasolar planets. Through observations of gravitational microlensing, the mission will probe the demographics of extrasolar planetary systems. Its coronagraph will enable imaging and spectroscopic study of nearby planets. It will also be able to complement GAIA's astrometric measurements of masses and orbits of nearby planets.

Spergel, David N.

2014-06-01

121

Scientific program in planetary atmospheric studies  

NASA Technical Reports Server (NTRS)

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

Broadfoot, A. L.

1983-01-01

122

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

NASA Astrophysics Data System (ADS)

Recent astronomical observations are allowing unprecedented measurements of masses and radii of low-mass transiting extrasolar planets, particularly super-Earths. Defined as planets with masses less than 10 Earth masses, super-Earths are expected to be the closest analogues to terrestrial planets in the solar system that are currently detectable around other stars. The observed masses, radii, and temperatures of super-Earths provide constraints on their interior structures, geophysical conditions, as well as their atmospheric compositions. Some of the most recently detected super-Earths span a wide gamut of possible compositions, from super-Mercuries and lava planets to water worlds with thick gaseous envelopes. In this work, we report joint constraints on the interior and atmospheric compositions of several super-Earths and discuss their possible formation scenarios using comprehensive models of their interiors, non-gray atmospheres, and formation conditions. Our model constraints are based on the sum-total of latest multi-wavelength measurements of transmission spectro-photometry, as well as observations of thermal emission where available. We will present a comparative analysis of all the transiting super-Earths currently known, including the Kepler planets, CoRoT-7b, and the two super-Earths with the most data, GJ 1214b and 55 Cancri e. We will discuss new observations on the horizon, and new theoretical and experimental work that will be critical to the characterization of super-Earths in the coming years. We will conclude with the geophysical implications of our results for different planets.

Madhusudhan, N.; Lee, K. K.; Mousis, O.

2012-12-01

123

Atmospheric Visibility Monitoring for planetary optical communications  

NASA Technical Reports Server (NTRS)

The Atmospheric Visibility Monitoring project endeavors to improve current atmospheric models and generate visibility statistics relevant to prospective earth-satellite optical communications systems. Three autonomous observatories are being used to measure atmospheric conditions on the basis of observed starlight; these data will yield clear-sky and transmission statistics for three sites with high clear-sky probabilities. Ground-based data will be compared with satellite imagery to determine the correlation between satellite data and ground-based observations.

Cowles, Kelly

1991-01-01

124

Scientific Program in Planetary Atmospheric Studies.  

National Technical Information Service (NTIS)

The Voyager encounters with Jupiter led to two main areas of investigation: (1) the definition of the structure and composition of the upper atmosphere and the interaction of the magnetosphere and atmosphere, and (2) the study of the plasma torus using th...

A. L. Broadfoot

1983-01-01

125

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

126

HITRAN2012 and Remote Sensing of Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

For the recently-released HITRAN2012 edition of the database, a substantial effort was taken to extend the HITRAN database to have capabilities for studying a variety of planetary atmospheres. Spectroscopic parameters for gases and spectral bands of molecules that are germane to the studies of planetary atmospheres have been assembled. These parameters include the types of data that have already been considered for transmission and radiance algorithms, such as line position, intensity, broadening coefficients, lower-state energies, and temperature dependence values. Besides adding new bands and isotopologues to the relevant molecules that already exist in HITRAN (methane, hydrogen halides, hydrogen disulfide, etc.), a number of new molecules, namely H_2, CS, C_4H_2, HC_3N and SO_3 have been incorporated into the HITRAN2012 database. For some of the molecules, additional parameters, beyond what is currently considered for the terrestrial atmosphere, have been archived. Examples are pressure-broadened half widths due to various foreign partners. Collision-induced absorption data for a large variety of the collision partners are provided in HITRAN for the first time. Future efforts, including preparation of a new edition of the HITEMP database, will be discussed. Note that another talk is given in the "Atmospheric Species" session, describing HITRAN improvements towards remote sensing of terrestrial atmosphere. This effort is supported by the NASA Planetary Atmospheres program, under the grant NNX10AB94G. L. S. Rothman, I. E. Gordon, et al. "The HITRAN 2012 molecular spectroscopic database," JQSRT, submitted 2013.

Gordon, I. E.; Rothman, L. S.; Li, G.

2013-06-01

127

16 and 24-Micron Photometry of Transiting Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We have recently used Spitzer MIPS-24 to detect light from the transiting extrasolar planet HD 209458b during its secondary eclipse. Previously, there had been no direct detection of light from an extrasolar planet. Our calculated brightness temperature constrains models of this planet's thermal emission. We now propose additional eclipse photometry of HD 209458b using the IRS blue peak-up array and MIPS-24 to provide a brightness temperature at 16 microns, reduce the errors on our 24-micron measurement, search for variability due to atmospheric dynamics, investigate the puzzlingly large radius of this planet, and possibly derive the day/night temperature contrast. We also propose eclipse photometry of the second-brightest transiting planet, TrES-1b, in the IRS blue peak-up array, with similar goals. These pioneering measurements of extrasolar planetary fluxes will constrain the many competing radiative, chemical, and dynamical models of these planets' atmospheres.

Harrington, Joseph; Cho, James; Deming, Drake; Hansen, Brad; Menou, Kristen; Richardson, Jeremy; Seager, Sara

2005-06-01

128

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

129

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

130

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

131

A spectrum of an extrasolar planet  

NASA Astrophysics Data System (ADS)

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 (7.5-13.2µm) of the transiting extrasolar planet HD 209458b. Our observations reveal a hot thermal continuum for the planetary spectrum, with an approximately constant ratio to the stellar flux over this wavelength range. Superposed on this continuum is a broad emission peak centred near 9.65µm that we attribute to emission by silicate clouds. We also find a narrow, unidentified emission feature at 7.78µm. Models of these `hot Jupiter' planets predict a flux peak near 10µm, where thermal emission from the deep atmosphere emerges relatively unimpeded by water absorption, but models dominated by water fit the observed spectrum poorly.

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

2007-02-01

132

Main Group Metal Ion Chemistry In Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Metal ions are a significant product of meteoric ablation within planetary atmospheres. The lifetimes and ultimate chemical processing of these metal ions depend crucially on their association chemistry with the dominant atmospheric constituents (variously N2, CO2, and H2 among the Solar System's representative planetary atmospheres), yet this association chemistry has received very little previous study. In this work we present, for the first time, calculated temperature-dependent termolecular association rate coefficients for the reactions of the dominant main-group metal ions Na+, Mg+, Al+, K+, and Ca+ with N2, CO2, and H2. These rate coefficients have been determined through the use of variational transition state theory, employing structural and thermochemical data obtained via ab initio quantum chemical calculations. Implications of the calculated kinetic data, for a few specific instances of meteoric metal-ion chemistry, are sketched out, and directions for future study are also outlined.

Petrie, Simon; Dunbar, Robert C.

2006-09-01

133

Tectonic implications of radiogenic noble gases in planetary atmospheres  

SciTech Connect

An account is given of the ways in which the He-4 and Ar-40 radiogenic isotopes furnish important constraints on planetary interior tectonics. In the case of the earth, where there are such independent constraints on radiogenic isotope concentrations as observed surface heat flow, the specification of radiogenic isotope concentration allows the interpretation of data on the Ar-40 atmospheric mass and mantle He-4 in terms of models for the entire mantle and of layered mantle convection. He loss rate estimates through the Venus atmosphere indicate a flux that is nearly equal to that through the earth atmosphere. 34 references.

Turcotte, D.L.; Schubert, G.

1988-04-01

134

Volcanic Degassing and the Atmosphere of Planetary Suites  

NASA Astrophysics Data System (ADS)

How unique the Earth is requires an urgent definition in front of the myriad of spatial observations revealing extra solar planets with variable spectral signatures. In the close solar system, high water abundance, atmospheric pressure at 1 bar and an O2-rich atmosphere constitute the main features of the Earth surface. This contrasts with dry Venus and its nearly 100 bar of reduced atmosphere dominated by CO2. This also contrasts with Mars, once flowed by water, today dominated by sulphate deposits, with 0.01 bar of atmospheric pressure and its oxidized surface. Such diversity in the physic and chemistry of planetary surfaces constitutes our most robust observation and benchmark for deciphering the remote exoplanets and defining the possible development of clement conditions for extra-terrestrial life. Volcanic degassing is a fundamental planetary process that conveys igneous volatiles species regulating important physical and chemical features of the exosphere. Understanding the planetary chemical fix supplied by volcanoes and how it can vary is therefore critical for a better definition of systems favorable to life emergence. We show that the atmospheric pressure, defining the minimum pressure of volcanic degassing, is the chief parameter controlling the composition of volcanic gases. On Venus, volcanic degassing occurring at minimum pressure of 100 bar can only be composed of CO2, whereas water and sulfur remain dissolved in the lavas. This explains the dry Venusian atmosphere. Degassing at 1 bar (minimum) on Earth produces mixtures dominated by water, explaining the Earth's wet surface. On Mars, gases produced at less than 0.05 bar contain more sulfur than water and Jupiter moon, Io, emits, in vacuum, gases that are dominated by sulfite. The composition of volcanic gases is therefore merely regulated by the atmospheric pressure. The latter is, in turn, mainly controlled by the size of the planet, even if little certitude exists about the most influential parameter governing atmospheric pressure. Such a behavior is dictated by volatile solubility laws in basalts, which filter the release of gaseous volcanic species independently from the volatile's abundances in the planetary interior. This behavior constitutes a simple but robust indicator for planetary exploration.

Gaillard, F.; Scaillet, B.

2012-12-01

135

Planetary Mass Spectrometry: From Atmospheres to the Solar Wind  

NASA Astrophysics Data System (ADS)

Measurement of the bulk composition and isotopic fractionation of planetary atmospheres yields essential information about their origin, evolution and eventual loss. In particular, measurements from below the homopause out through the exosphere to the solar wind (e.g., at Mars and Venus) or to a planetary magnetosphere (e.g., at Titan) are essential to understanding processes driving atmospheric evolution and loss. Over the past three years we have developed and tested prototypes of two types of time-of-flight (TOF) mass spectrometers capable of the comprehensive measurements needed to settle questions of atmospheric evolution and loss. The first is the Ion Neutral Mass Spectrometer (INMS) which uses electrostatic mirrors to artificially lengthen and focus ion flight times, allowing the spectrometer to reach mass resolution needed to separate key compounds such as N2 and CO or isotopologues such as 13C17O16O vs. 12C18O16O (dM = 0.0033 amu). In order to boost sensitivity and signal to noise the INMS is also capable of storing and concentrating gases for prolonged analysis. The INMS prototype has demonstrated mass resolution > 15,000 M/dM and sensitivity for noble gas isotopes at 1 part per billion. The second spectrometer is the hot plasma composition analyzer (HPCA), a carbon-foil based instrument with heritage from the CAPS Cassini Ion Mass Spectrometer but with significantly improved mass resolution and sensitivity. The HPCA is designed to measure ion fluxes impinging on and escaping from planetary atmospheres. Together the INMS and HPCA cover the broad range of ion species and velocity space needed for investigation of planetary atmospheres and ionospheres and their interactions with the space environment.

Young, D. T.; Waite, J. H.; de Los Santos, A.; Miller, G. P.; Burch, J. L.; Wilson, P.; Pickens, K. S.; Brockwell, T. G.; Gomez, R.; Grimes, J.; Patrick, E. L.; Richter, A.; Roberts, J. M.; Teolis, B. D.; Westlake, J. H.

2008-12-01

136

Infrared quantitative spectroscopy and planetary atmospheres  

NASA Astrophysics Data System (ADS)

Optical measurements of atmospheric minor constituents are carried out using spectrometers working in the UV-visible, infrared and microwave spectral ranges. In all cases the quality of the analysis and of the interpretation of the atmospheric spectra requires the best possible knowledge of the molecular parameters of the species of interest. To illustrate this point we will concentrate on recent laboratory studies of nitric acid, chlorine nitrate and formaldehyde. Nitric acid is one of the important minor constituent of the terrestrial atmosphere. Using new and accurate experimental results concerning the spectroscopic properties of the H14NO3 and H15NO3 molecules, as well as improved theoretical methods (Perrin et al., 2004), it has been possible to generate an improved set of line parameters for these molecules in the 11.2 ?m spectral region. These line parameters were used to detect for the first time the H15NO3 molecule in the atmosphere analyzing atmospheric spectra recorded by the MIPAS experiment. The retrievals of chlorine nitrate profiles are usually performed using absorption cross sections (Birk and Wagner, 2003). Following a high resolution analysis of the ?3 and ?4bands of this species in the 12.8 ?m region wepropose, as a possibility, to use line by line calculation simulating its ?4Q-branch for the atmospheric temperature and pressure ranges. For the measurement of atmospheric formaldehyde concentrations, mid-infrared and ultraviolet absorptions are both used by ground, air or satellite instruments. It is then of the utmost importance to have consistent spectral parameters in these various spectral domains. Consequently the aim of the study performed at LISA (Gratien et al., 2007) was to intercalibrate formaldehyde spectra in the infrared and ultraviolet regions acquiring simultaneously UV and IR spectra using a common optical cell. The results of the work will be presented. Also high resolution infrared data derived from Perrin et al., 2003 have been used to determine vertical distributions from the upper troposphere to the stratopause using the high spectral resolution measurements of MIPAS (Steck et al., 2008). References: M. Birk, G. Wagner, J. Quant. Spectros. Radiat.Transfer, 82, 443, 2003. G. Brizzi, M. Carlotti, J.-M. Flaud, A. Perrin and M. Ridolfi, Geophys. Res. Lett., 34, L03802, 2006. A. Gratien, B. Picquet-Varrault, J. Orphal, E. Perraudin, J.-F. Doussin and J.-M. Flaud, J. Geophys. Res., 112, D05305, 2007. A. Perrin, F. Keller and J.-M. Flaud, J. Mol. Spectrosc., 221, 192, 2003. A. Perrin, J. Orphal, J.-M. Flaud, S. Klee, G. Mellau, H. Mader, D. Walbrodt and M. Winnewisser, J. Mol. Spectrosc, 228, 375, 2004. T. Steck, N. Glatthor, T. von Clarmann, H. Fischer, J. M. Flaud, B. Funke, U. Grabowski, M. Hopfner, S. Kellmann, A. Linden, A. Perrin, and G. P. Stiller, Atm. Chem. Phys., 8, 463, 2008.

Flaud, J.-M.

2009-04-01

137

Infrared laboratory studies of synthetic planetary atmospheres  

NASA Technical Reports Server (NTRS)

The initial stages of the research were involved with a test of Burch's law of multiplicative transmittance for mixed absorbing gases when their lines are broadened by H2 and He, which are constituents of the atmospheres of the major planets. The broadening of individual lines in the CO fundamental by various gases was investigated. Line strength and half-width for individual CO lines were studied as a function of temperature. Measurements of total band absorptance as a function of absorber thickness and total effective pressure were made at various temperatures for bands of CO and N2O. Attempts were made to develop a phenomenological theory of line broadening that would account for the phenomena observed for the CO fundamental and those reported for more highly polar gases. Laboratory measurements of nitric acid vapor absorptance were compared with balloon measurements in arriving at an estimate of the quantity of nitric acid vapor present in the earth's atmosphere in the region of the ozone layer.

Williams, D.

1972-01-01

138

On the mutually inclined orbits of planets in the CoRoT-7 extrasolar planetary system  

Microsoft Academic Search

We propose a method to be able to decide whether the planets of CoRoT-7 are moving on mutually inclined orbits in the order of i > 10 degrees. The extrasolar system CoRoT-7 is very special with respect to the closeness of the planets to the host star, which results in a fast dynamical development. It would therefore be possible to

R. Dvorak; J. Schneider; V. Eybl

2010-01-01

139

Atmospheric planetary waves induced by solar rotation  

NASA Technical Reports Server (NTRS)

It is known that there are variations in the atmospheric processes with a period close to that of the rotation of the Sun (27 days). The variations are discovered in tropospheric processes, rainfalls, geopotential and in stratosphere. The main theoretical problem is the identification of the physical process by which these heterogeneous solar and meteorological phenomena are connected. Ivanovsky and Krivolutsky proposed that the periodic heating of the ozone layer by the short wave radiation would be the reason of excitation the 27-day oscillations. It was also assumed that excitement takes place in condition of resonance with an excited mode corresponding to the conditions present in the stratospheric circulations. The possibility is discussed of the resonant excitation and presentation is made of the data analysis results which support this idea.

Krivolutsky, A. A.

1989-01-01

140

An Analytic Radiative-Convective Model for Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

141

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

142

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

143

Haze Formation in Planetary Atmospheres: Lessons from the Lab  

NASA Astrophysics Data System (ADS)

For more than 50 years, haze formation in planetary atmospheres has been simulated in the laboratory. Of particular interest are simulations of haze formation in the atmosphere of Titan, the largest moon of Saturn. These simulation experiments have provided a wealth of knowledge about the possible composition and optical properties of haze particles, informed efforts to understand the transition between gas phase and particle chemistry, and provide “analogue” materials to aid in the selection and testing of the next generation of spacecraft based analytical techniques. In this talk I will review the current state of knowledge from Titan atmosphere simulation experiments, discuss difficulties that have arisen from knowledge gained from the Cassini-Huygens mission to the Saturn system, and present particular areas where laboratory studies could provide much needed guidance for the observation and modeling communities studying atmospheres in our solar system and beyond.

Horst, Sarah

2014-06-01

144

Models of Planetary-Scale Waves in the Venus Atmosphere.  

NASA Astrophysics Data System (ADS)

Planetary-scale ultraviolet albedo contrasts in the clouds of Venus are atmospheric waves which travel slowly with respect to the "4-day rotation" of the cloud -top atmosphere. These waves cannot be directly forced by topography or by the diurnal variation of solar heating, since they are not fixed with respect to the solid planet (243 day rotation period) or to the overhead motion of the Sun (117 day period). Possible forcing mechanisms for these waves include hydrodynamic instabilities and organized patterns of convection and turbulence. The forcing probably takes place over a range of frequencies, with the atmosphere exhibiting a preferred response at 4 - 6 day periods. In this thesis we develop two models of wave propagation which predict oscillations with the observed properties. The models incorporate the monotonic variation of atmospheric rotation from nearly zero at the planetary surface to the "4-day rotation" at the cloud tops. Wind shear precludes separability of the wave propagation equation, in contrast to the simpler terrestrial problem. We solve the problem by expanding in spherical harmonics (the spherical model) or by simplifying the latitude dependence (the "beta-plane" model). Preferred modes of oscillation are found by imposing forcing over a wide range of frequencies and looking for those frequencies at which the atmospheric response is greatly enhanced. Our results reveal two types of planetary-scale waves which can explain the observations: upward-propagating gravity waves, which travel slightly faster than the "4 -day rotation," and upward-propagating Rossby waves, which travel slightly slower. The two types of waves combine together with varying phase differences to give a variety of shapes, including the "horizontal Y" and related features seen in ultraviolet images of Venus.

Covey, Curtis Charles

1982-03-01

145

Planetary Atmospheres: Decadal Survey of Priorities for 2003-2013  

NASA Astrophysics Data System (ADS)

At the request of NASA, the NAS/NRC Space Science Board and its Committee on Planetary and Lunar Exploration have organized a community assessment of the scientific priorities of the U.S. planetary science research programs. Community response to this initiative is being coordinated by the Division for Planetary Science of the American Astronomical Society. We will present a description of the progress made by the Planetary Atmospheres Community Panel, which has the difficult mission of summarizing current knowledge, identifying key science questions, and recommending research priorities and actions needed to create and maintain future capabilities. A comparative approach is clearly valuable in identifying the issues of greatest importance and in making recommendations that are likely to be implemented. We wish to attract broad participation in the survey process and to solicit input about key research needs. The needs are divided into the broad categories of (1) Comparative Understanding, (2) Observations, (3) Modeling, (4) Laboratory and Theory, and (5) Future Capabilities. Let us know about your opinions, interests, and recommendations by electronic mail, by posting at the AAS Web site, or at the AGU Meeting. http://www.nationalacademies.org/ssb/ssefrontpage.html http://www.aas.org/ ~dps/decadal/

Huestis, D. L.; Bougher, S. W.

2001-12-01

146

Biomarkers of extrasolar planets and their observability  

NASA Astrophysics Data System (ADS)

The first space-borne instruments able to detect and characterize extrasolar terrestrial planets, Darwin (ESA) and TPF-C (Terrestrial Planet Finder-Coronograph, NASA), should be launched at the end of the next decade. Beyond the challenge of planet detection itself, the ability to measure mid-infrared (Darwin) and visible (TPF-C) spectra at low resolution will allow us to characterize the exoplanets discovered. The spectral analysis of these planets will extend the field of planetary science beyond the Solar System to the nearby Universe: It will give access to certain planetary properties (albedo, brightness temperature, radius) and reveal the presence of atmospheric compounds, which, together with the radiative budget of the planet, will provide the keys to understanding how the climate system works on these worlds. If terrestrial planets are sufficiently abundant, these missions will collect data for numerous planetary systems of different ages and orbiting different types of stars. Theories for the formation, evolution and habitability of the terrestrial planets will at last face the test observation. The most fascinating perspective offered by these space observatories is the ability to detect spectral signatures indicating biological activity. In this chapter, we review and discuss the concept of extrasolar biosignatures or biomarkers. We focus mainly on the identification of oxygen-rich atmospheres through the detection of O2 and O3 features, addressing also the case of other possible biomarkers and indicators of habitability.

Selsis, Franck; Paillet, Jimmy; Allard, France

147

A model-independent test of the spatial variations of the Newtonian gravitational constant in some extrasolar planetary systems  

NASA Astrophysics Data System (ADS)

In this paper, we directly constrain possible spatial variations of the Newtonian gravitational constant G over the range ~0.01-5 au in various extrasolar multiplanet systems. Using the third Kepler law, we determine the quantity ?XY = GX/GY for each couple of planets X and Y located at different distances from their parent star; deviations of the measured values of ? from unity would signal variations of G. The obtained results for ? = 1 - ? are found to be very compatible with zero within the experimental errors (?/?? ~ 0.2-0.3). We make a comparison with an analogous test previously performed in our Solar system.

Iorio, Lorenzo

2007-04-01

148

Planetary Atmospheres: Data Archiving, tools and services developments in France  

NASA Astrophysics Data System (ADS)

Involvements in France in recent space experiments (Mars-Express, Venus-express, Cassini- Huygens, Rosetta, etc...), in related laboratory activities (Pampre, Progra2, etc...) and in related numerical modelling (Planetary GCM and Exosphere) have promoted developments of archiving centres, tools and web based services in the planetary atmosphere scientific community. Theses activities have been developed in frames of many space agencies (CNES, ESA, NASA, etc...), following (or not following), when possible, recommendations of international alliances of data providers (IPDA, IVOA, etc..) and supported by international projects (Europlanet, Euro-VO, etc...). The diversity of standards used by the whole community is a problem to develop interoperable tools. An overview of these activities in France is necessary for future selection of interoperability standards to be used by our international community in the frame of IPDA.

Sarkissian, Alain

149

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

NASA Astrophysics Data System (ADS)

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as "central tenets", for example, the importance of radio science in establishing the conducting upper layer. The central tenets are distinguished from additional findings that merely corroborate, or are explained by, the global circuit model. Using this analysis it is possible to specify which observations are preferable for detecting global circuits in extraterrestrial atmospheres. Schumann resonances, the extremely low frequency signals generated by excitation of the surface-ionosphere cavity by electrical discharges, are identified as the most useful single measurement of electrical activity in a planetary atmosphere.

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

150

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

NASA Astrophysics Data System (ADS)

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as “central tenets”, for example, the importance of radio science in establishing the conducting upper layer. The central tenets are distinguished from additional findings that merely corroborate, or are explained by, the global circuit model. Using this analysis it is possible to specify which observations are preferable for detecting global circuits in extraterrestrial atmospheres. Schumann resonances, the extremely low frequency signals generated by excitation of the surface-ionosphere cavity by electrical discharges, are identified as the most useful single measurement of electrical activity in a planetary atmosphere.

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

2008-06-01

151

Theoretical studies of important processes in planetary and comet atmospheres  

NASA Technical Reports Server (NTRS)

This is the fifth semi-annual progress report describing research on dissociative recombination reactions in planetary and comet atmospheres. The Appendix has two papers that describe NASA supported research. Both papers have been recently accepted for publication. The first paper, 'The Generation of O(S-1) from the Dissociative Recombination of O2(+)', describes in detail the Multichannel Quantum Defect (MQDT) theory used for the calculation of dissociative recombination (DR) cross sections and rates. The application to the generation of the upper state of the atomic oxygen green line emission is of great importance to the modelling of planetary atmospheres. The second paper in the Appendix, 'Dissociative Recombination of the Ground State of N2(+)', applies the methods described in the first paper to N2(+). We find remarkable agreement with the prior microwave afterglow experiments for both the total recombination rate and for its electron temperature dependence. However, the results disagree with recent merged beams results which gave cross sections that are a factor of five below the microwave afterglow experiments and the current results. DR of N2(+) is an important mechanism for generating energetic N atoms which can escape the atmosphere of Mars. Currently we are also continuing additional work on the DR of O2(+) which is aimed at calculating both the total DR rate as a function of ion vibrational level and the rate for production of O(D-1).

Guberman, Steven L.

1991-01-01

152

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

153

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

154

A new inversion method of remote sounding of planetary atmospheres  

NASA Technical Reports Server (NTRS)

A new inversion method for remote sounding of planetary atmospheres is presented which appears to have several significant advantages over the conventional methods. This method is applicable to high-resolution observations where the spectral lines are fully resolved and is based on matching the calculated slopes of the spectral line profiles with slopes of the observed line shapes. The method is applied to inversion of ozone absorption lines in the earth's atmosphere, and the results are compared with those obtained by a conventional method. The proposed method is seen to provide a significant improvement in the overall accuracy of the retrieved profiles, with higher vertical resolution and higher levels which may be probed.

Abbas, M. M.

1979-01-01

155

Composition/Structure/Dynamics of comet and planetary satellite atmospheres  

NASA Technical Reports Server (NTRS)

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

Combi, Michael R. (Principal Investigator)

1995-01-01

156

Theoretical studies of important processes in planetary and comet atmospheres  

NASA Technical Reports Server (NTRS)

Dissociative recombination (DR) reactions in planetary and comet atmospheres are discussed. A computer program was developed which determines DR cross sections and rates using potential curves and electronic capture widths. It uses Multi-Channel Quantum Defect Theory (MQDT) to include excited Rydberg resonance levels in the DR cross section and rate calculations. Each vibrational level of a molecular ion is the limit for an infinite series of Rydberg states. Above each ion vibrational level are Rydberg vibrational levels having higher ion levels as their series limit. These Rydberg vibrational levels are resonances, i.e., neutral states which are imbedded in the electron-molecular ion continuum. The process in which the Rydberg level causes an abrupt perturbation in the cross section for DR (because of interference between capture into the Rydberg level and capture into the repulsive dissociative state) is referred to as indirect recombination. The process in which the Rydberg levels are excluded and recombination goes from the entrance channel to the repulsive state is called direct recombination. The full DR process, i.e., both direct and indirect recombination, is the process of importance for planetary atmospheres. These ideas are illustrated with the new results for DR from excited ion vibrational levels of O2(+) into the dissociative state which leads to O(1S) + O(1D).

Guberman, Steven L.

1990-01-01

157

Building a "big picture" of planetary atmospheres dynamics  

NASA Astrophysics Data System (ADS)

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

Read, Peter; Wang, Yixiong

158

Data Assimilation and Data Fusion for Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

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

Houben, Howard

2005-01-01

159

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

Microsoft Academic Search

Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is

J.-M. Grießmeier; A. Stadelmannc; J. L. Grenfell; H. Lammerf

160

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

Microsoft Academic Search

Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is

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

2009-01-01

161

Continuing Studies in Support of Ultraviolet Observations of Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

This program was a one-year extension of an earlier Planetary Atmospheres program grant, covering the period 1 August 1996 through 30 September 1997. The grant was for supporting work to complement an active program observing planetary atmospheres with Earth-orbital telescopes, principally the Hubble Space Telescope (HST). The recent concentration of this work has been on HST observations of Jupiter's upper atmosphere and aurora, but it has also included observations of Io, serendipitous observations of asteroids, and observations of the velocity structure in the interplanetary medium. The observations of Jupiter have been at vacuum ultraviolet wavelengths, including imaging and spectroscopy of the auroral and airglow emissions. The most recent HST observations have been at the same time as in situ measurements made by the Galileo orbiter instruments, as reflected in the meeting presentations listed below. Concentrated efforts have been applied in this year to the following projects: The analysis of HST WFPC 2 images of Jupiter's aurora, including the Io footprint emissions. We have performed a comparative analysis of the lo footprint locations with two magnetic field models, studied the statistical properties of the apparent dawn auroral storms on Jupiter, and found various other repeated patterns in Jupiter's aurora. Analysis and modeling of airglow and auroral Ly alpha emission line profiles from Jupiter. This has included modeling the aurora] line profiles, including the energy degradation of precipitating charged particles and radiative transfer of the emerging emissions. Jupiter's auroral emission line profile is self-absorbed, since it is produced by an internal source, and the resulting emission with a deep central absorption from the overlying atmosphere permits modeling of the depth of the emissions, plus the motion of the emitting layer with respect to the overlying atmospheric column from the observed Doppler shift of the central absorption. By contrast the airglow emission line, which is dominated by resonant scattering of solar emission, has no central absorption, but displays rapid time variations and broad wings, indicative of a superthermal component (or corona) in Jupiter's upper atmosphere. Modeling of the observed motions of the plumes produced after the impacts of the fragments of Comet S/L-9 with Jupiter in July 1994, from the HST WFPC 2 imaging series.

Clark, John

1997-01-01

162

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

Microsoft Academic Search

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

Christopher J. Burke

2005-01-01

163

Plasma Flow Past Cometary and Planetary Satellite Atmospheres  

NASA Technical Reports Server (NTRS)

The tenuous atmospheres and ionospheres of comets and outer planet satellites share many common properties and features. Such similarities include a strong interaction with their outer radiation, fields and particles environs. For comets the interaction is with the magnetized solar wind plasma, whereas for satellites the interaction is with the strongly magnetized and corotating planetary magnetospheric plasma. For this reason there are many common or analogous physical regimes, and many of the same modeling techniques are used to interpret remote sensing and in situ measurements in order to study the important underlying physical phenomena responsible for their appearances. We present here a review of various modeling approaches which are used to elucidate the basic properties and processes shaping the energetics and dynamics of these systems which are similar in many respects.

Combi, Michael R.; Gombosi, Tamas I.; Kabin, Konstantin

2000-01-01

164

Theoretical studies of important processes in planetary and comet atmospheres  

NASA Technical Reports Server (NTRS)

The dissociative recombination (DR) of the AB(+) molecular ion with an electron has been shown to be an important component in the detailed interpretation of planetary ionosphere data. A first principles theoretical approach is developed for calculating the DR cross sections and rates for AB(+) molecular ions. The calculations focus on O2(+) and N2(+) DR, and are the first to include the indirect DR mechanism (Ryberg vibrational levels below v = 0 level of ion) for a molecule larger than H2(+). The importance of electron capture width in calculating the cross sections and rates is also examined. Electron capture widths are given for all states of O2 that are of importance to DR (lowest 10 vibrational levels of ion). Knowledge of the details of dissociative recombination will be needed for interpretation of data from future interplanetary and comet atmospheric studies.

Guberman, Steven L.

1991-01-01

165

Hydrogen atom initiated chemistry. [chemical evolution in planetary atmospheres  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

166

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?

167

The Colors of Extrasolar Planets  

Microsoft Academic Search

The color of an extrasolar planet is an important property because, for the case of direct detection, color is likely to be the first post-detection quantity to be measured. We show here that color carries considerable information on planetary properties. The next most likely measurable quantity is a low resolution spectrum, and we show what additional information this carries. Several

W. A. Traub

2003-01-01

168

The applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research  

NASA Technical Reports Server (NTRS)

A review of the applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research during the past four decades is presented with an emphasis on chemical equilibrium models and thermochemical kinetics. Several current problems in planetary atmospheres research such as the origin of the atmospheres of the terrestrial planets, atmosphere-surface interactions on Venus and Mars, deep mixing in the atmospheres of the gas giant planets, and the origin of the atmospheres of outer planet satellites all require laboratory data on the kinetics of thermochemical reactions for their solution.

Fegley, Bruce, Jr.

1990-01-01

169

Measuring the Infrared Spectrum of the Transiting Extrasolar Planet HD 209458b  

NASA Astrophysics Data System (ADS)

Researchers from two independent groups recently detected the first infrared signal from an extrasolar planet. Deming et. al. (2005a) detected the 24-micron flux density of HD 209458b using MIPS at secondary eclipse, and Charbonneau et. al. (2005) detected the infrared signal of TrES-1 using IRAC at 4.5 and 8 microns. These results have dramatically demonstrated the ability of Spitzer to characterize extrasolar planets. We propose to build on these observations with IRS spectroscopy of HD 209458b from 7.4 to 14.5 microns. By observing the system both during and outside of secondary eclipse, we will derive the planetary spectrum from the change in the shape of the continuum spectrum in combined light. These observations will lead directly to a measurement of the temperature gradient in the planetary atmosphere and the column density of water above the clouds, and we will search for variability due to atmospheric dynamics.

Richardson, L. Jeremy; Cho, James; Deming, Drake; Hansen, Brad; Harrington, Joseph; Menou, Kristen; Seager, Sara

2005-06-01

170

Discovery of Planetary Systems With SIM.  

National Technical Information Service (NTIS)

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

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

2004-01-01

171

Discovery of Planetary Systems With SIM.  

National Technical Information Service (NTIS)

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

B. Oppenheimer D. Fischer G. W. Marcy P. R. Butler S. Frink

2008-01-01

172

Extrasolar Planets in the Gliese 581 System - Model Atmospheres and Implications for Habitability  

NASA Astrophysics Data System (ADS)

The planets Gliese (GL) 581 c and d were the first objects which merited a detailed study of their potential habitability. The orbital distances of the two planets have recently been revised. We investigated the habitability of GL 581 c and d under these new conditions with a 1-D radiative-convective atmospheric model, varying the surface pressure and atmospheric composition. GL 581 c was found to be uninhabitable for all scenarios considered. GL 581 d was also found to be uninhabitable for low and medium CO2 atmospheres (3.55×10-4 and 5% CO2 vmr, 1 ? psurf ? 20 bar).

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

2010-10-01

173

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

National Technical Information Service (NTIS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based or spacecraft-based radio astronomical (emission) observations can be used to infer...

P. G. Steffes

2002-01-01

174

Upper thermal boundary layer of planetary atmosphere: an experience of developing a general theory  

Microsoft Academic Search

Any planetary atmosphere has an upper layer where molecular heat conduction contributes significantly to the energy balance. In that layer the heat from absorbed solar radiation is transferred down to the lower atmosphere where it is removed away by the longwave radiation of atmosphere. We call that layer an upper thermal boundary layer and propose a general model for it

A. Semenov; G. Shved

2005-01-01

175

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

176

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

177

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

NASA Technical Reports Server (NTRS)

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

Grams, G. W.; SHARDANAND

1972-01-01

178

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

179

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

180

Red clouds in reducing atmospheres. [polymer production by UV irradiation in planetary atmospheres  

NASA Technical Reports Server (NTRS)

A dark reddish-brown high-molecular weight polymer is produced by long wavelength ultraviolet irradiation of abundant gases in reducing planetary atmospheres. The polymer is examined by paper chromatography, mass spectrometry, and infrared, visible, and ultraviolet spectroscopy. High carbon-number straight-chain alkanes with NH2 and, probably, OH and C = O groups are identified, along with amino acids. There are chemical similarities between this polymer and organic compounds recovered from carbonaceous chondrites and precambrian sediments. The visible and near-ultraviolet transmission spectrum of the polymer shows its absorption optical depth to be redder than lambda(-2) and perhaps similar in coloration to the clouds of Jupiter, Saturn, and Titan. The nitrile content is small, and the polymer should be semitransparent in the 5 micrometer atmospheric window. Such polymers may be a common constituent of clouds in the outer solar system and on the early earth.

Khare, B. N.; Sagan, C.

1973-01-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

182

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

183

Extrasolar Storms: The Physics and Chemistry of Evolving Cloud Structures in Brown Dwarf Atmospheres  

NASA Astrophysics Data System (ADS)

Condensate clouds pose the most significant challenge to the understanding of ultracool atmospheres of brown dwarfs and giant?exoplanets. In three ongoing Spitzer programs we have?taken advantage of Spitzer's ability to obtain high-cadence uninterrupted observations to pioneer a new technique, rotational phase mapping, and successfully explored the properties of cloud covers in ~50 brown?dwarfs. Among other exciting results we found that most brown dwarfs possess heterogeneous cloud cover, often with complex surface structures. Perhaps the most perplexing behavior seen in our surveys is light curve evolution on timescales as short as 5 hours and as long as a year. This unexpected behavior offers a unique opportunity to explore the dynamics of cloud layers, but requires multi-epoch data sets. We propose here to follow up a representative set of varying brown dwarfs via multi-epoch Spitzer and HST phase mapping to carry out the first quantitative exploration of cloud cover evolution. The proposed study will establish the first time-resolved multi-wavelength light curve library for brown dwarfs. Spitzer uniquely offers precise 3-5 micron photometry and continuous coverage that allow us to detect cloud structures a fraction of the size of the Great Red Spot on Jupiter in our targets. Combined with HST grism spectroscopy during a subset of the Spitzer observations, the Spitzer phase maps will allow us to disentangle the effects of cloud formation, differential rotation, large-scale rainout and dispersal of clouds. As different wavelengths probe different pressures and different rotational phases probe different latitudes we will be able to explore the two or even three-dimensional structure of the atmospheres. We will also constrain the dynamical and radiative timescales for brown dwarfs and compare these to theoretical predictions to identify the underlying atmospheric dynamics. This program will leave a unique legacy that will propel studies of ultracool atmosphere studies into a new era.

Apai, Daniel; Buenzli, Esther; Flateau, Davin; Metchev, Stanimir; Marley, Mark; Radigan, Jacqueline; Lowrance, Patrick; Showman, Adam; Artigau, Etienne; Heinze, Aren; Burgasser, Adam; Mohanty, Subhanjoy

2012-09-01

184

Negative ions in the ionospheres of planetary bodies without atmospheres  

NASA Technical Reports Server (NTRS)

It is noted that negative ions may be formed in the ionospheres of Mercury, the moon, and Jupiter's satellites with densities of a few percent of the ionospheric electron density. Negative ions result from three mechanisms at the planetary surface: charge inversion during energetic proton scattering, with simultaneous secondary negative ion emission, and micrometeorite impacts. The density and distribution of negative ions around planetary bodies depends primarily on the negative ion lifetimes determined through photodetachment by solar radiation.

Wekhof, A.

1981-01-01

185

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

186

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

187

Upper thermal boundary layer of planetary atmosphere: An attempt of developing a general model  

Microsoft Academic Search

In any planetary atmosphere there is an uppermost layer in which the molecular thermal conduction is a significant mechanism of forming the thermal structure of the atmosphere. In this paper, the similarity approach is first used to develop the 1-D general model of aforementioned layer. The main concepts of the model are (i) the radiative equilibrium condition at the lower

A. O. Semenov; G. M. Shved

2008-01-01

188

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

189

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

Microsoft Academic Search

The planetary boundary layer (PBL) over Mexico City was probed with a scanning backscatter lidar to characterize and evaluate the multidimensional structure of the atmosphere. Comparisons were made between radiosonde and lidar-derived PBL heights which showed the two techniques to be in close agreement. The spatial properties of the free atmosphere-PBL interface were found to be approximately the same size

D. I. Cooper; W. E. Eichinger

1994-01-01

190

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

Microsoft Academic Search

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

Paul G. Steffes; Bryan M. Karpowicz

2008-01-01

191

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

192

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

NASA Technical Reports Server (NTRS)

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and Earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorping properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurement of the microwave properties of atmospheric gases under simulated conditions for the outer planets were conducted. Results of these measurements are discussed.

Steffes, Paul G.

1987-01-01

193

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

194

Ion precipitation in planetary upper atmospheres: test particle simulations and implications for escape  

NASA Astrophysics Data System (ADS)

A 3-D Monte Carlo energetic particle transport model has been developed and successfully applied to ion precipitation into planetary upper atmospheres in our solar system (viz., Earth, Mars, Jupiter, and Saturn), and can be readily be extended using a full Lorentz motion formu-lation in the absence of strong dipole planetary magnetic fields. This model can be used with a variety of other models to assess the influence of hot ion precipitation on the thermosphere and exosphere of planetary atmospheres and the subsequent sputtering and escape. For instance in the case of Mars, a pick-up ion transport model already exists to allow for particle acceleration exerted by the convection electric field used in conjunction with existing model results from the Mars Thermosphere General Circulation Model (MTGCM) and the BATS-R-US global MHD model. The loss of exospheric neutrals through ionization, in which they become pick-up ions in the solar wind, can be calculated to examine the relative contribution of the various ionization processes. Solar wind protons as well as pick-up ions from a planetary exosphere routinely enter and alter their upper atmosphere. A study of the pick-up ion escape, sputtering, ion-ization, excitation, and energy deposition will be reviewed and discussed, resulting in a robust examination of the influence of energetic ion transport on planetary upper atmospheres.

Parkinson, Christopher; Liemohn; Fang, Xiaohua

195

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

196

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

NASA Technical Reports Server (NTRS)

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

Tobak, Murray; Peterson, Victor L.

1964-01-01

197

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

198

Models of planetary wave propagation in the middle atmosphere  

Microsoft Academic Search

Linear steady-state models were used to study the propagation of quasi-stationary planetary waves through zonally symmetric basic states with both meridional and vertical wind shears. Simulations from a comprehensive general circulation model were analyzed to provide realistic basic state and forcing. A quasi-geostrophic and a primitive-equation model were constructed. The models were found to give very different results when the

Chung-Chun Ma

1990-01-01

199

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

200

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

201

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

202

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

203

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

204

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

205

Laboratory measurements of microwave and millimeter-wave properties of planetary atmospheric constituents  

NASA Technical Reports Server (NTRS)

Accurate data on microwave and millimeter-wave properties of potential planetary atmospheric constituents is critical for the proper interpretation of radio occultation measurements, and of radio astronomical observations of both continuum and spectral line emissions. Such data is also needed to correct for atmospheric effects on radar studies of surface reflectivity. Since the refractive and absorptive properties of atmospheric constituents often vary drastically from theoretically-predicted profiles, especially under the extreme conditions characteristic of the planetary atmosphere, laboratory measurements under simulated planetary conditions are required. This paper reviews the instrumentation and techniques used for laboratory measurement of the refractivity and absorptivity of atmospheric constituents at wavelengths longward of 1 mm, under simulated planetary conditions (temperature, pressure, and broadening gases). Techniques for measuring both gases and condensates are considered. Also reviewed are the relative accuracies of the various techniques. Laboratory measurements are reviewed which have already been made, and additional measurements which are needed for interpretation of data from Venus and the outer planets, are highlighted.

Steffes, Paul G.

1989-01-01

206

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

207

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

208

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

209

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

210

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

211

Possibility of growth of airborne microbes in outer planetary atmospheres  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

212

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

213

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

214

Thermo-resistive Instability of Hot Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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

Menou, Kristen

2012-07-01

215

THERMO-RESISTIVE INSTABILITY OF HOT PLANETARY ATMOSPHERES  

SciTech Connect

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

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

2012-07-20

216

Solid State Photon Counting for Planetary Altimetry, Atmospheric Lidar and Deep Space Navigation  

Microsoft Academic Search

We are describing the solid state photon counting technique, its performance, capability and possible applications in space research and planetary exploration in particular. The solid state photon counting concept has been tested in the previous Mars missions the laser altimeter and atmospheric Lidar have been constructed for the Mars `92 and Mars Polar Lander '98.

I. Prochazka; K. Hamal

2004-01-01

217

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

Microsoft Academic Search

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

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

2008-01-01

218

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

Microsoft Academic Search

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

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

2009-01-01

219

Evaporation of extrasolar planets  

NASA Astrophysics Data System (ADS)

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

Lecavelier Des Etangs, A.

2010-12-01

220

Extrasolar planets and Their Parent Stars  

Microsoft Academic Search

Extrasolar planetas (exoplanets), or planets orbiting stars other than our own Sun, are a relatively new field of the astronomical and planetary sciences. After the discovery of Pluto in 1930, planet-finding activities appeared to have reached an end for the foreseeable future. Several brown dwarfs have been discovered between 1930 and 1993 orbiting other solar-type star. Brown dwarfs (or \\

Garik Israelian

2010-01-01

221

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

PubMed

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

Nezlin, Mikhail V.

1994-06-01

222

Analysis of stellar occultation data for planetary atmospheres. I - Model fitting, with application to Pluto  

NASA Technical Reports Server (NTRS)

Consideration is given to an analytic model for a stellar-occultation light curve developed for a small, spherically symmetric planetary atmosphere that includes thermal and molecular weight gradients in a region that overlies an extinction layer. The model incorporates two equivalent sets of parameters. One set specifies the occultation light curve in terms of signal levels, times, and time intervals. The other set specifies physical parameters of the planetary atmosphere. Equations are given for the transforming between the sets of parameters, including their errors and correlation coefficients. Detailed numerical calculations are presented for a benchmark case. The results obtained are consistent with the isothermal prediction of the 'methane-thermostat' model of Pluto's atmosphere.

Elliot, J. L.; Young, L. A.

1992-01-01

223

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

224

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

225

Scattering and Absorption by Nonspherical Particles in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

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

West, Robert A.

2005-01-01

226

A reassessment of prebiotic organic synthesis in neutral planetary atmospheres.  

PubMed

The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought. PMID:18204914

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

2008-04-01

227

A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

228

Biological modulation of planetary atmospheres: The early Earth scenario  

NASA Technical Reports Server (NTRS)

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

Schidlowski, M.

1985-01-01

229

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

230

Experimental characterisation of new design thermometers for planetary atmospheric measurements  

NASA Astrophysics Data System (ADS)

A new design of a platinum resistance sensor has been studied for atmospheric experiments onboard a lander mission in order to measure the vertical temperature profile of the Martian atmosphere. Laboratory tests of different prototypes of platinum resistance thermometers (PRT) have been performed and the results are presented. The prototypes are derived from the HASI TEM, the temperature sensors of the Huygens probe of the Cassini/Huygens mission. To obtain an accurate estimation of the atmospheric temperature gradient, very high spatial resolution measurements are required. This means that, for a given descent profile, a high sampling frequency is needed. Studies have been carried out to improve the sensor performance; they result in new possible structural solutions. In the new design, the sensing element (Pt wire) is suspended on very thin non-metallic fibres truss, in order to thermally decouple it from the supporting structure. Several sensors have been designed and built; laboratory tests have been conducted in a wind tunnel in order to dynamically characterise the sensors. The time response has been investigated and the time constant calculated from the asymptotic trend of the sensor response to a step-wise electric power, simulating a steep temperature gradient. The measurements of the PRT have been compared to those of numerical simulations. A prototype has also flown in a balloon flight test in order to verify its performance in Earth's atmosphere. Results from post flight analysis data of the balloon flight experiment are presented; spectral analysis of the data has evidenced the larger bandwidth of the new sensor and a higher signal to noise ratio. Improvements of HASI TEM performance are shown in terms of a shorter time constant; this allows the new sensor to be able to resolve smaller temperature variations during the descent in Mars' atmosphere.

Colombatti, G.; Francesconi, A.; Lion Stoppato, P. F.; De Cecco, M.; Ferri, F.; Fulchignoni, M.; Angrilli, F.

2000-10-01

231

Planetary Entry Probes and Mass Spectroscopy: Tools and Science Results from In Situ Studies of Planetary Atmospheres and Surfaces  

NASA Technical Reports Server (NTRS)

Probing the atmospheres and surfaces of the planets and their moons with fast moving entry probes has been a very useful and essential technique to obtain in situ or quasi in situ scientific data (ground truth) which could not otherwise be obtained from fly by or orbiter only missions and where balloon, aircraft or lander missions are too complex and costly. Planetary entry probe missions have been conducted successfully on Venus, Mars, Jupiter and Titan after having been first demonstrated in the Earth's atmosphere. Future missions will hopefully also include more entry probe missions back to Venus and to the outer planets. 1 he success of and science returns from past missions, the need for more and better data, and a continuously advancing technology generate confidence that future missions will be even more successful with respect to science return and technical performance. I'he pioneering and tireless work of Al Seiff and his collaborators at the NASA Ames Research Center had provided convincing evidence of the value of entry probe science and how to practically implement flight missions. Even in the most recent missions involving entry probes i.e. Galileo and Cassini/Huygens A1 contributed uniquely to the science results on atmospheric structure, turbulence and temperature on Jupiter and Titan.

Niemann, Hasso B.

2007-01-01

232

Mechanisms and observations for isotope fractionation of molecular species in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Chemcial and physical processes which may give rise to isotope fractionation of molecular species in the atmospheres of both earth and other planets are reviewed, along with observations of isotopically substituted molecules in planetary atmospheres. Mechanisms for production of isotope fractionation considered include atmospheric escape and the effect of isotope substitution on equilibrium constants (including those of phase changes), photolysis rates, and chemical reaction rates. The isotopes considered for compounds in the terrestrial atmosphere include D, T, C-13, C-14, N-15, O-18, and S-34. Compounds for which data about isotopic composition in the terrestrial atmosphere are summarized include CO, CO2, O3, N2O, NH3, SO2, H2S, H2O, H, H2, and CH4. Planetary atmospheres discussed include those of Venus, Mars, Jupiter, Saturn, Uranus, and Titan; isotopes reviewed are D, C-13, N-15, and O-18. Suggestions for additional research in the area of isotopically substituted molecules in atmospheres are offered.

Kaye, Jack A.

1987-01-01

233

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

234

Some issues related to evolution of planetary atmospheres  

SciTech Connect

This work considers several issues related to atmospheric evolution on Venus and Earth. Chapter 1 introduces 5 topics related to atmospheric evolution on Venus which will be specifically addressed in remaining chapters: 1) photochemical stability of CO/sub 2/, 2) abundance and distribution of water, 3) abundance of CO and oxidation state of the atmosphere, 4) hydrogen escape and its effect on composition, and 5) deuterium enrichment. Chapter 2 considers the response of the hydrogen escape flux on Venus to changes in composition, effusion velocity, and temperature. Chapter 3 establishes the observational, thermodynamic, and photochemical constraints on the abundance of molecular hydrogen above the clouds of Venus. Chapter 4 extends the work of Yung and DeMore (1982) on the photochemical stability of CO/sub 2/, employing more realistic models for sulphur and water supply to the stratophere. Chapter 5 considers the evolutionary implications of recent work on specific nonthermal escape mechanisms using results from earlier chapters to constrain evolutionary models. Chapter 6 is a separate investigation of the evolution of noble gasses on Earth, based on reported measurements of noble gas abundances in the glassy margins of mid-ocean-ridge basalts. Appendices A and B provide details of the photochemical model used to investigate Venus and the degassing model used to investigate Earth. Results include a simple functional form for escape flux as a function of effusion velocity and the minimum exobase temperature resulting in significant thermal escape (475K).

Yatteau, J.H.

1983-01-01

235

Acoustic measurements of atmospheric electrical discharges for planetary probes  

NASA Astrophysics Data System (ADS)

We present acoustic measurements carried out in a high voltage laboratory in order to characterise signals from various discharge processes, e.g. lightning or corona discharge. The investigations are in the frame of the Acoustic Sensor Package (ACU) for Titan Saturn System Mission (TSSM), a proposed post Cassini-Huygens mission. The multi-microphone system ACU has the scientific objective to characterise acoustical phenomena in Titan's atmosphere with heritage from Huygens Atmospheric Structure Instrument (HASI/PWA) on Huygens probe. We investigate the possibility to use acoustic measurements for the study of atmospheric electrical discharges. The experiments in the high voltage lab used a generator with voltages up to 1.9 million volts with different polarities. Various discharges have been generated and acoustical signals detected. From the sound signature we derive parameters which influence the technical design of ACU, e.g. filter coefficients for capturing fast transient acoustic phenomena and intermittent signals. In addition multi-microphone sound systems can be used to estimate the location of discharges.

Eichelberger, H.; Prattes, G.; Schwingenschuh, K.; Jaffer, G.; Aydogar, Ö.; Jernej, I.; Besser, B.; Stachel, M.; Tokano, T.; Falkner, P.

2010-05-01

236

Probing the extreme planetary atmosphere of WASP-12b  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

237

Planetary optical and infrared imaging  

NASA Technical Reports Server (NTRS)

The purpose is to obtain and analyze high spatial resolution CCD coronagraphic images of extra-solar planetary material and solar system objects. These data will provide information on the distribution of planetary and proto-planetary material around nearby stars leading to a better understanding of the origin and evolution of the solar system.

Terrile, Richard J.

1991-01-01

238

Extension Of The Hitran Database To Aid Remote Sensing Of Diverse Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Studies of the spectroscopic signatures of planetary atmospheres are a powerful tool for extracting detailed information concerning their constituents and thermodynamic properties. The HITRAN molecular spectroscopic database has traditionally served researchers involved with terrestrial atmospheric problems, including remote-sensing of constituents in the atmosphere. In collaboration with laboratories across the globe, an extensive effort is currently underway to extend HITRAN database to have capabilities for studying a variety of planetary atmospheres. Spectroscopic parameters for gases and spectral bands of molecules that are germane to the studies of planetary atmospheres are being assembled. A major accomplishment of the effort is the assembly and recent release of the HITEMP database, which included spectral parameters suitable for simulating high-temperature and NLTE spectra for H2O, CO2, CO, NO and OH gases. A number of new molecules, such as H2, CS, C4H2, HC3N and C2N2 are being incorporated for the HITRAN2012 release of the database, while several other molecules are pending. For some of the molecules, additional parameters, beyond what is currently considered for the terrestrial atmosphere will be archived. In particular, collision-broadened halfwidths due to various foreign partners will now be provided. In that regard not only do we collect, evaluate and extrapolate available experimental and theoretical data, but also create a new structure to the database for user convenience. Collision-induced absorption data for H2-H2, H2-N2, H2-He, H2-CH4, CH4-CH4, N2-N2, N2-O2, O2-O2, O2-CO2 and N2-CH4 were also recently released. Partition sums that are necessary for applications at a wide range of temperature have recently been calculated for a wide variety of molecules of planetary interest. Current accomplishments and future efforts will be reviewed at the meeting. This effort is supported by the NASA Planetary Atmospheres program, under the grant NNX10AB94G.

Gordon, Iouli; Li, G.; Rothman, L. S.

2012-10-01

239

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

Microsoft Academic Search

The technique of GCMS analysis, which has been used with a great success on several past planetary missions, is not adapted for precise measurements of the isotopic composition of planetary atmospheres (noble gases, stable isotopes), and volatile outgassed products from solid sample pyrolysis. Static mass spectrometry, coupled with gas separation by cryo-separation, and chemical trapping, is commonly used in the

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

2003-01-01

240

Analytical design of sensors for measuring during terminal phase of atmospheric temperature planetary entry  

NASA Technical Reports Server (NTRS)

An analytical study was conducted to develop a sensor for measuring the temperature of a planetary atmosphere from an entry vehicle traveling at supersonic speeds and having a detached shock. Such a sensor has been used in the Planetary Atmosphere Experiments Test Probe (PAET) mission and is planned for the Viking-Mars mission. The study specifically considered butt-welded thermocouple sensors stretched between two support posts; however, the factors considered are sufficiently general to apply to other sensors as well. This study included: (1) an investigation of the relation between sensor-measured temperature and free-stream conditions; (2) an evaluation of the effects of extraneous sources of heat; (3) the development of a computer program for evaluating sensor response during entry; and (4) a parametric study of sensor design characteristics.

Millard, J. P.; Green, M. J.; Sommer, S. C.

1972-01-01

241

Rugged, no-moving-parts windspeed and static pressure probe designs for measurements in planetary atmospheres  

NASA Technical Reports Server (NTRS)

Instruments developed for making meteorological observations under adverse conditions on Earth can be applied to systems designed for other planetary atmospheres. Specifically, a wind sensor developed for making measurements within tornados is capable of detecting induced pressure differences proportional to wind speed. Adding strain gauges to the sensor would provide wind direction. The device can be constructed in a rugged form for measuring high wind speeds in the presence of blowing dust that would clog bearings and plug passages of conventional wind speed sensors. Sensing static pressure in the lower boundary layer required development of an omnidirectional, tilt-insensitive static pressure probe. The probe provides pressure inputs to a sensor with minimum error and is inherently weather-protected. The wind sensor and static pressure probes have been used in a variety of field programs and can be adapted for use in different planetary atmospheres.

Bedard, A. J., Jr.; Nishiyama, R. T.

1993-01-01

242

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

243

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

244

Tools for discovering and characterizing extrasolar planets  

NASA Astrophysics Data System (ADS)

Among the group of extrasolar planets, transiting planets provide a great opportunity to obtain direct measurements for the basic physical properties, such as mass and radius of these objects. These planets are therefore highly important in the understanding of the evolution and formation of planetary systems: from the observations of photometric transits, the interior structure of the planet and atmospheric properties can also be constrained. The most efficient way to search for transiting extrasolar planets is based on wide-field surveys by hunting for short and shallow periodic dips in light curves covering quite long time intervals. These surveys monitor fields with several degrees in diameter and tens or hundreds of thousands of objects simultaneously. In the practice of astronomical observations, surveys of large field-of-view are rather new and therefore require special methods for photometric data reduction that have not been used before. Since 2004, I participate in the HATNet project, one of the leading initiatives in the competitive search for transiting planets. Due to the lack of software solution which is capable to handle and properly reduce the yield of such a wide-field survey, I have started to develop a new package designed to perform the related data processing and analysis. After several years of improvement, the software package became suffi ciently robust and played a key role in the discovery of several transiting planets. In addition, various new algorithms for data reduction had to be developed, implemented and tested which were relevant during the reduction and the interpretation of data. In this PhD thesis, I summarize my efforts related to the development of a complete software solution for high precision photometric reduction of astronomical images. I also demonstrate the role of this newly developed package and the related algorithms in the case of particular discoveries of the HATNet project.

Pál, András

2009-06-01

245

Outer satellite atmospheres: Their extended nature and planetary interactions  

NASA Astrophysics Data System (ADS)

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.

1984-04-01

246

Empirical model of differential and integral cosmic ray spectra in the planetary atmospheres  

NASA Astrophysics Data System (ADS)

Galactic and anomalous cosmic rays (modulated by the solar wind) influence strongly on the ionization state of the whole atmosphere. We propose a model which generalizes the differential D(E) and integral spectra of galactic (GCR) and anomalous cosmic rays (ACR) in the planetary atmosphere during the 11-year solar cycle. The calculated integral model spectra are on the basis on mean gradients: for GCR - 3%/AU (Fuji Z. et al., 1997; Heber B et al., 1995), 7%/AU for anomalous protons (McKibben et al., 1979; Christian et al., 1999), and 8.5%/AU for anomalous helium (McKibben et al., 1985). We analyze the relationship between the model parameters and solar activity (expressed with the Wolf number). The modulated differential spectra of galactic cosmic rays are compared with a simple numerical solution of the onedimensional cosmic ray transport equation and the force field approximation to the transport equation. The model results are compared with IMAX92, CAPRICE94, AMS98 and BESS measurements. The proposed analytical model gives practical possibility for investigation of experimental data from measurements of galactic cosmic rays and their anomalous component in planetary atmosphere at different solar activity levels. The obtained parameters are used for determination of the profiles of ionization in planetary ionospheres at different conditions (quiet and disturbed) in the solar-terrestrial relationships.

Buchvarova, Marusja

247

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

NASA Technical Reports Server (NTRS)

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

Fox, Kenneth; Kim, Sang J.

1988-01-01

248

Earth as an Extrasolar Planet  

NASA Astrophysics Data System (ADS)

The NASA Astrobiology Institute's Virtual Planetary Laboratory 3-D line-by-line, multiple-scattering spectral Earth model generates spatially- and temporally-resolved synthetic spectra and images of Earth. The model can be used to simulate Earth's spectrum as it would appear to a distant observer at arbitrary viewing geometry over wavelengths from the far-ultraviolet to the far-infrared on timescales from minutes to years. We have validated our model against data from NASA's EPOXI mission, which obtained spatially- and temporally-resolved visible photometric (0.3-1.0 um) and near-infrared spectroscopic (1.05-4.8 um) observations of Earth on three dates. Further validations include comparisons to photometric Earthshine observations (0.4-0.7 um) which span a wide range of Earth phase as well as comparisons to date-specific, high spectral resolution mid-infrared observations (6-15 um) of Earth acquired by the Atmospheric Infrared Sounder aboard NASA's Aqua satellite. To reproduce the available observations we have run the model at a spatial resolution of almost 200 pixels, an atmospheric resolution of 48 pixels, and a cloud treatment with 4 categories of water clouds. Our validated model can now be used as a tool for feasibility studies for future space-based planet detection missions (e.g., NASA's Terrestrial Planet Finder). The model can also be used to better understand sensitivity to global signatures of habitability and life in disk-integrated spectra of Earth. Example applications include an investigation into the ability of Earth's atmosphere and clouds to obscure direct surface temperature measurements from thermal-infrared observations as well as a study of the phase-dependent contribution of Earth's ocean "glint spot” to the overall brightness of the planet. The "glint spot" is generated by specular reflection of sunlight on Earth's oceans and could potentially be used to detect oceans on extrasolar planets. Both clouds and oceans exhibit phase-dependent reflectance behaviors, possibly obscuring the detection of, or eliminating, the ocean glint.

Robinson, Tyler D.; Meadows, V.; Crisp, D.

2010-10-01

249

A study of nonlinear ionization processes in planetary atmospheres  

SciTech Connect

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

El-Agamaqi, M.M.

1988-01-01

250

Theoretical Studies of Important Processes in Planetary and Comet Atmospheres  

NASA Technical Reports Server (NTRS)

Using theoretical quantum chemical calculations, I have successfully described the dissociative recombination (DR) of O2(+) leading to the excited S-1 state of atomic oxygen, the upper state of the well known green line emission. The process is described by O2(+) + e(-) yields O(S-1)) + O(D-1) (1) where e(-) is an electron and the product oxygen atoms are both excited. This process is important in the atmospheres of Venus, Mars and Earth. I have shown in prior calculations that only one repulsive potential curve of O2, f(sup l)Sigma(sub u, sup +) can generate O(S-1) from DR of the lowest vibrational levels of O2(+). However, in the prior results, the calculated quantum yield (i.e. the number of O(S-1) atoms produced for every two product atoms) from the O2(+) v = 0 level was smaller than the laboratory and atmospheric measurements by more than an order of magnitude. Including only direct recombination, the calculated quantum yield for O(S-1) is only 0.0016. In a calculation that accounts for both direct and indirect recombination, the quantum yield is 0.0012. The range of experimentally determined quantum yields is between 0.01 and 0.23. Because of this large difference between the theoretical and experimental quantum yields, it was thought for some time that the ionospheric and laboratory O2(+) must be vibrationally excited since for excited levels, theory gave quantum yields that are similar to experimental yields. It was also suggested that some other process was generating O(S-1) but none could be identified. Under current NASA support, I have found that reaction (1) proceeds via an unusual mechanism. The f(sup 1)Sigma(sub u, sup,+) state does not cross the ion between the turning points of the v = 0 level of the O2(+) ground state. The lack of a favorable crossing leads to a very small calculated DR rate coefficient. However, this mechanism assumes that initial electron capture must occur into the repulsive state that leads to )(S-1). Instead, I have found that initial electron capture occurs mostly into the B(sup 3)Sigma(sup u, sub -) state which crosses the ion between the turning points of the v = 0 ion level and has a large DR rate coefficient. The B state dissociates to O(D-1) and )(P-3). After capture, some of the flux is transferred to the f(sup 1)Sigma(sup u, sub +) state via symmetry mixed intermediate Rydberg states. The neutral Rydberg states are a mixture of Sigma(sub u, sup +)-1 and Sigma(sub u, sup -)-3 symmetry.

Guberman, Steven L.

1998-01-01

251

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.

252

Planetary atmospheres with mass spectrometers carried on high-speed probes or satellites  

NASA Technical Reports Server (NTRS)

Earth satellite-borne mass spectrometers are considered, taking into account the identification of atomic oxygen in the thermosphere with an 'open' source mass spectrometer flown on a sounding rocket, the conventional closed-source instrument, the mass spectrometers on the Atmosphere Explorer satellites, and mass spectrometer electron multiplier output. A description is presented of mass spectrometers and planetary entry probes. Attention is given to an attempt to obtain an atmospheric composition profile with a terrestrial entry probe, the descending trajectory in the early orbits of the Atmosphere Explorer C satellite, and the molecular nitrogen densities for the descending legs of the orbits. It is pointed out that chemical reactions on the surfaces of the mass spectrometer make the measurement of reactive atmospheric species such as atomic oxygen very difficult.

Nier, A. O.

1977-01-01

253

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.

254

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

255

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

NASA Astrophysics Data System (ADS)

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

Fontenla, J. M.

2013-12-01

256

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

PubMed

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

Griffith, C A; Zahnle, K

1995-08-25

257

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

258

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

259

Ultra-High Resolution Spectroscopic Remote Sensing: A Microscope on Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

Remote sensing of planetary atmospheres is not complete without studies of all levels of the atmosphere, including the dense cloudy- and haze filled troposphere, relatively clear and important stratosphere and the upper atmosphere, which are the first levels to experience the effects of solar radiation. High-resolution spectroscopy can provide valuable information on these regions of the atmosphere. Ultra-high spectral resolution studies can directly measure atmospheric winds, composition, temperature and non-thermal phenomena, which describe the physics and chemistry of the atmosphere. Spectroscopy in the middle to long infrared wavelengths can also probe levels where dust of haze limit measurements at shorter wavelength or can provide ambiguous results on atmospheric species abundances or winds. A spectroscopic technique in the middle infrared wavelengths analogous to a radio receiver. infrared heterodyne spectroscopy [1], will be describe and used to illustrate the detailed study of atmospheric phenomena not readily possible with other methods. The heterodyne spectral resolution with resolving power greater than 1,000.000 measures the true line shapes of emission and absorption lines in planetary atmospheres. The information on the region of line formation is contained in the line shapes. The absolute frequency of the lines can be measured to I part in 100 ,000,000 and can be used to accurately measure the Doppler frequency shift of the lines, directly measuring the line-of-sight velocity of the gas to --Im/s precision (winds). The technical and analytical methods developed and used to measure and analyze infrared heterodyne measurements will be described. Examples of studies on Titan, Venus, Mars, Earth, and Jupiter will be presented. 'These include atmospheric dynamics on slowly rotating bodies (Titan [2] and Venus [3] and temperature, composition and chemistry on Mars 141, Venus and Earth. The discovery and studies of unique atmospheric phenomena will also be described, such as non-thermal and lasing phenomena on Mars and Venus, mid-infrared aurora on Jupiter [5], and results of small body impacts on Jupiter [6]. The heterodyne technique can also be applied for detailed study of the Earth's stratosphere and mesosphere by measuring trace constituent abundances and temporal and spatial variability as well as winds, which provide information of transport. All ground-based measurements will be described as complementary and supporting studies for on-going and future space missions [7] (Mars Express, Venus Express, Cassini Huygens, JUNO, ExoMars Trace Gas Orbiter, and the Europa Jupiter System Mission, an Earth Science Venture Class missions), Proposed instrument and technology development for a space flight infrared heterodyne spectrometer will be described.

Kostiuk, Theodor

2010-01-01

260

Extrasolar planets around intermediate mass stars  

NASA Astrophysics Data System (ADS)

One of the earliest hints for extrasolar planets came with the discovery almost 15 years ago of low amplitude, long period radial velocity (RV) variations in several K giant stars, ? Gem, ? Tau (Aldebaran) and ? Boo. Since then it has been confirmed that for ? Gem (stellar mass =1.7 Modot) these RV variations are due to a planetary companion. Aldebaran is another K giant star showing long-lived (>26 years) and coherent RV variations. These are most likely due to a planetary companion having a mass of 9 MJup using an estimated mass of 2.5 Modot for the star. Giant stars like ? Tau and ? Gem offer us the possibility of studying the process of planet formation around stars more massive than the sun. The main sequence stars with masses >1.2 Modot are ill-suited for RV surveys as there are few spectral lines for measuring the RV and these are often broadened by high rates of stellar rotation. Currently over 20 intermediate mass giant stars are known to host extrasolar planets. This sample is sufficiently large that we can begin to look at the overall properties of planets around intermediate mass stars. These suggest that more massive stars may have more massive planets that the orbital eccentricities for their extrasolar planets show the wide range of eccentricities seen for main sequence, solar mass stars, and that unlike for main sequence stars there seems to be no preference for metal rich intermediate mass stars to host extrasolar planets.

Hatzes, A. P.

2008-08-01

261

Laboratory Studies of O2 Excited States Relevant to CO2 Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Knowledge of the details relevant to the production of excited O2 is critical for the study and modeling of composition, energy transfer, airglow, and transport dynamics in CO2 planetary atmospheres. Significant gaps and uncertainties exist in our understanding of the above processes, and often the relevant input from laboratory measurements is missing or outdated. We are performing laser-based laboratory experiments to investigate the O-atom three-body recombination responsible for the generation of oxygen airglow in the upper atmosphere of Venus and Mars. In the laboratory, an ultraviolet light pulse from a laser photoinitiates O-atom recombination in a CO2 environment. Spectroscopic techniques are used to probe the excited O2 molecules produced following recombination and subsequent relaxation in CO2. We present our latest laboratory results and discuss their atmospheric implications. This work is supported by the National Science Foundation's (NSF) Planetary Astronomy Program under grant AST-1109372. K. Storey-Fisher participated at a Research Experiences for Undergraduates (REU) site at SRI International, co-funded by the Division of Physics of the NSF and the Department of Defense in partnership with the NSF REU program (PHY-1002892).

Kostko, O.; Storey-Fisher, K.; Kalogerakis, K. S.

2013-12-01

262

Effects of turbulent dispersion of atmospheric balance motions of planetary boundary layer  

NASA Astrophysics Data System (ADS)

New Reynolds’ mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion with ? 0 will increase depth of Ekman layer, reduce wind velocity in Ekman layer and produce a more satisfactory Ekman spiral lines fit the observed wind hodograph. The wind profile in the surface layer including turbulent dispersion is still logarithmic but the von Karman constant k is replaced by k 1 = ? 1 — k/2, the wind increases a little more rapidly with height.

Liu, Shikuo; Huang, Wei; Rong, Pingping

1992-06-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

264

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

265

The Georgia Tech millimeter-wavelength measurement system and some applications to the study of planetary atmospheres  

NASA Astrophysics Data System (ADS)

With the advent of new millimeter-wavelength arrays such as the Atacama Large Millimeter Array capable of providing very precise maps of planetary emission, it becomes very critical to have an accurate knowledge of the millimeter-wavelength properties of gases under those planetary conditions. A millimeter-wavelength planetary atmospheric simulator and measurement system have been developed at the Georgia Tech Planetary Atmospheres Laboratory to accurately measure the propagation properties of gases under simulated planetary atmospheric conditions. The measurement system operates in the 2-4 millimeter-wavelength range and withstands up to 3 bars of pressure. It currently operates in the 190-300 K temperature range, and with minor modifications can operate in the 300-550 K temperature range for measurements of certain highly millimeter-wavelength-opaque gases. The measurements from this system can be used for developing accurate models of the millimeter-wavelength properties of gases under various planetary conditions which can then be used for retrieving the abundances of those gases through various remote sensing techniques.

Devaraj, Kiruthika; Steffes, Paul G.

2011-04-01

266

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

NASA Astrophysics Data System (ADS)

Studies of the atmospheres of the giant planets require an accurate understanding of the vapor-liquid equilibrium for the ammonia-water system. New vapor-liquid equilibrium data for this system have been taken in the Laboratory for Chemical Thermodynamics at Cornell University using a custom-built apparatus. An extensive evaluation of the available literature data has been conducted to assess their quality and thermodynamic consistency. A refined model for the ammonia-water binary based on the analysis of both the literature data and our own new experimental measurements is presented. This model yields temperature-dependent parameters from which investigators can compute vapor-liquid equilibrium values at any temperature of planetary interest. We have applied our new model to the calculation of ammonia concentration as a function of temperature in condensing ammonia-water clouds for model Jovian atmospheres.

Parikh, N. C.; Zollweg, J. A.

1996-09-01

267

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

268

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

269

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

270

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

SciTech Connect

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

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

1994-11-20

271

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

NASA Astrophysics Data System (ADS)

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

Cooper, D. I.; Eichinger, W. E.

1994-11-01

272

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

273

Ash Dispersal in Planetary Atmospheres: Continuum vs. Non-continuum Effects  

NASA Astrophysics Data System (ADS)

The dispersal of ash from a volcanic vent on any given planet is dictated by particle properties (density, shape, and size distribution), the intensity of the eruptive source, and the characteristics of the planetary environment (atmospheric structure, wind field, and gravity) into which the ash is erupted. Relating observations of potential pyroclastic deposits to source locations and eruption conditions requires a detailed quantitative understanding of the settling rates of individual particles under changing ambient conditions. For atmospheres that are well described by continuum mechanics, the conventional Newtonian description of particle motion allows particle settling velocities to be related to particle characteristics via a drag coefficient. However, under rarefied atmospheric conditions (i.e., on Mars and at high altitude on Earth), non-continuum effects become important for ash-sized particles, and an equation of motion based on statistical mechanics is required for calculating particle motion. We have developed a rigorous new treatment of particle settling under variable atmospheric conditions and applied it to Earth and Mars. When non-continuum effects are important (as dictated by the mean free path of atmospheric gas relative to the particle size), fall velocities are greater than those calculated by continuum mechanics. When continuum conditions (i.e., higher atmospheric densities) are reached during descent, our model switches to a conventional formulation that determines the appropriate drag coefficient as the particle transits varying atmospheric properties. The variation of settling velocity with altitude allows computation of particle trajectories, fall durations and downwind dispersal. Our theoretical and numerical analyses show that several key, competing factors strongly influence the downwind trajectories of ash particles and the extents of the resulting deposits. These factors include: the shape of the particles (non-spherical particles fall more slowly than spherical particle shapes commonly adopted in settling models); the formation of particle aggregates, which enhances settling rates; and the lagging of particle motion behind the ambient wind field, which results in less widely dispersed deposits. Above all, any particles experiencing non-continuum effects settle faster and are less widely dispersed than particles falling in an entirely continuum regime. Our model results demonstrate the complex interplay of these factors in the Martian environment, and our approach provides a basis for relating deposits observed in planetary datasets to candidate volcanic sources and eruption conditions. This allows for a critical reassessment of the potential for explosive volcanism to contribute to extremely widespread, fine-grained, layered deposits such as the Medusae Fossae Formation.

Fagents, S. A.; Baloga, S. M.; Glaze, L. S.

2013-12-01

274

Commission 53: Extrasolar Planets  

Microsoft Academic Search

Commission 53 on Extrasolar Planets was created at the 2006 Prague General Assembly of the IAU, in recognition of the outburst of astronomical progress in the field of extrasolar planet discovery, characterization, and theoretical work that has occurred since the discovery of the pulsar planets in 1992 and the discovery of the first planet in orbit around a solar-type star

Michel Mayor; Alan P. Boss; Paul R. Butler; William B. Hubbard; Philip A. Ianna; Martin Kürster; Jack J. Lissauer; Karen J. Meech; François Mignard; Alan J. Penny; Andreas Quirrenbach; Jill C. Tarter; Alfred Vidal-Madjar

2009-01-01

275

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

276

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

277

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

278

Large-scale properties of lightning in extrasolar objects  

NASA Astrophysics Data System (ADS)

Mineral clouds play a special role as a catalyst for a variety of charge processes also in extrasolar objects. If clouds are charged, the surrounding environment becomes electrically activated, and ensembles of charged grains are electrically discharging (e.g. by lightning), which significantly infuences the local chemistry creating conditions similar to those thought responsible for life in early planetary atmospheres. We note that such lightning discharges contribute also to the ionisation state of the atmosphere. We apply scaling laws for electrical discharge processes from laboratory measurements and numerical experiments to Drift-Phoenix model atmosphere results to model the discharge's propagation downwards (as lightning) and upwards (as sprites) through the atmospheric clouds. We evaluate the spatial extent and energetics of lightning discharges. First attempts to show the infuence of lightning on the local gas phase indicate an increase of small carbohydrate molecules like CH and CH2 at the expense of CO and CH4. Dust forming molecules are destroyed and the cloud particle properties are frozen-in unless enough time is available for complete evaporation.

Helling, Christiane; Bailey, Rachel; Hodosan, Gabriella; Bilger, Camille; Stark, Craig

2014-05-01

279

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

Microsoft Academic Search

The long-standing problem of the existence of equatorial superrotation in a slowly rotating planetary atmosphere has been solved analytically. Each of ten terms in the averaged zonal momentum equation is analyzed systematically, first by scale analysis, then through analytic formulations and numerical evaluations, and finally by comparison with well-known planetary atmospheres. Key parameters of the analytic formulations are found to

X. Zhu

2004-01-01

280

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

281

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

NASA Astrophysics Data System (ADS)

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

Ozima, M.

2010-12-01

282

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

283

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

NASA Astrophysics Data System (ADS)

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

Steffes, Paul G.

2013-10-01

284

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

285

Astrometric Masses of Extrasolar Planets and Brown Dwarfs  

NASA Astrophysics Data System (ADS)

We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.

Benedict, George

2005-07-01

286

Astrometric Masses of Extrasolar Planets and Brown Dwarfs  

NASA Astrophysics Data System (ADS)

We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses.Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.

Benedict, George

2006-07-01

287

Astrometric Masses of Extrasolar Planets and Brown Dwarfs  

NASA Astrophysics Data System (ADS)

We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses.Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.

Benedict, George

2005-07-01

288

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

289

Inverse multiple scattering problems. III - Inadequacy of certain limb darkening and phase curves for retrieving atmospheric information and limitations of approximate scattering models. [for planetary atmospheres  

NASA Technical Reports Server (NTRS)

The paper considers three complementary inverse multiple scattering problems relating to a uniquely defined atmospheric scattering model. Consideration is given to the appropriateness, for data inversion purposes, of intensities observed in diffuse reflection under a variety of experimental conditions; the uniqueness of the inverse solution is investigated. It is found that light curves representing monotonic variations, such as limb darkening curves and phase curves for a planetary (e.g., Venus) disk center are unsuitable for inferring atmospheric and scattering parameters.

Fymat, A. L.; Lenoble, J.

1979-01-01

290

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

291

Calculation of Refraction Indices of Planetary Atmospheres Using the HITRAN and GEISA spectroscopic databases  

NASA Astrophysics Data System (ADS)

Calculations of the refractive indices from the visible to far-infrared for Earth and other planetary atmospheres are presented. The calculations have been performed using a recently developed fortran code that computes the real part of the refractive indices using as input the oscillator strengths (location on a wavenumber (wavelength) axis plus the strengths related to Einstein coefficients, transition moments, etc) from the HITRAN and GEISA spectroscopic databases. The absorption spectrum is the imaginary part of the refractive index, which essentially is a Kramers-Kronig transform of the real part. These are plugged into the numerator and denominator of the standard oscillator formula, corrected for the Claussius-Mossotti terms. The formulation used in this work is based on the work by Mathar (Ref. 1) and developed in support of astronomical observations. In this paper the effect of the variation of the refraction indices with wavelength and atmospheric conditions and comparisons with a previously developed model by Collavita et al. (Ref. 2) will be be discussed. References: 1. R. Mathar, Applied Optics 43(4), 928-932, 2004. 2. Collavita et al., Publications of the Astronomical Society of the Pacific 116, 876-885, 2004.

Martin-Torres, Javier

2010-05-01

292

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

293

Planetary Systems and the Origins of Life  

NASA Astrophysics Data System (ADS)

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

Pudritz, Ralph; Higgs, Paul; Stone, Jonathon

2013-01-01

294

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

NASA Astrophysics Data System (ADS)

Our research program is dedicated to the measurement and modeling of vacuum ultraviolet and UV molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on molecular nitrogen, carbon dioxide, sulfur dioxide, and diatomic sulfur are in progress. N2: We focus on the measurement of line f-values and line widths within the complex spectrum between 80 and 100 nm. Our measurements are incorporated into a theoretical model of the absorption spectrum of N2 which has established the mechanisms responsible for predissociation and reproduces all observed features in 14N2 and its isotopomers as a function of temperature. CO2: The photodissociation of CO2 is a fundamental photochemical process in the atmospheres of Mars and Venus. Our research centers on the measurement of high resolution cross sections from 91 to 120 nm. We have completed measurements at 295 K and 195 K over the 106 to 120 nm region, and we are analyzing recent measurements of cross sections between 91 and 106 nm. SO2: We provide astronomers with high-resolution cross section data for the complex ultraviolet absorption spectrum between 198 and 325 nm. Using the Imperial College VUV Fourier transform spectrometer, we have completed and published room temperature cross sections, and we are completing work on low-temperature measurements over the same spectral region. S2: Interpretations of atmospheric (Io, Jupiter, cometary comae) S2 absorption features are hindered by a complete lack of laboratory cross section data in the ultraviolet. We are beginning an effort to quantify the photoabsorption spectrum of S2 from 200 to 300 nm based on theoretical calculations and laboratory measurements. Coupled-channel calculations will be complemented by measurements of the absorption spectrum of S2 at high resolution.

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

2008-09-01

295

Planetary Interior Evolution and Life  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

296

Planetary and synoptic scale adjustment of the Arctic atmosphere to sea ice cover changes  

NASA Astrophysics Data System (ADS)

By means of unforced simulations with a global coupled circulation model it is shown that naturally occurring changes between high and low sea ice cover phases of the Arctic Ocean exert a strong influence on the Northern Hemisphere storm tracks. This work emphasizes the nonlinear dynamical feedback between Arctic sea ice cover and the Arctic Oscillation (AO) such as atmospheric response depending upon the wintertime sea ice distribution. Two seven year long time slices, with high and low sea ice cover, were analyzed with respect to the feedbacks between the time-mean flow, the quasi-stationary planetary and the baroclinic waves. The wave energy fluxes on time scales of 2 to 6 days increase in the middle troposphere between 30 and 60°N during the high sea ice phase and increase the zonal wind. This increase is compensated by a strong reduction in the Eliassen-Palm fluxes on time scales from 10 to 90 days between 60 and 70°N during high sea ice phases, accompanied by reduced zonal winds. High sea ice cover phases are related to the zonal wind changes during the positive phases of the AO, especially over the northern part of the Atlantic Ocean.

Sokolova, E.; Dethloff, K.; Rinke, A.; Benkel, A.

2007-09-01

297

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

298

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

299

Detecting Oceans on Extrasolar Planets Using the Glint Effect  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

300

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

Microsoft Academic Search

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

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

1998-01-01

301

Model-Atmosphere Spectra of Central Stars of Planetary Nebulae - Access via the Virtual Observatory Service TheoSSA  

NASA Astrophysics Data System (ADS)

In the framework of the Virtual Observatory (VO), the German Astrophysical Virtual Observatory GAVO project provides easy access to theoretical spectral energy distributions (SEDs) within the registered GAVO service TheoSSA (http://dc.g-vo.org/theossa). TheoSSA is based on the well established Tübingen NLTE Model-Atmosphere Package (TMAP) for hot, compact stars. This includes central stars of planetary nebulae. We show examples of TheoSSA in operation.

Rauch, T.; Reindl, N.

2014-04-01

302

A laboratory investigation of the production and properties of molecular and radical species pertinent to planetary atmospheres  

NASA Technical Reports Server (NTRS)

Vinylidene (H2C=C) is shown to be the largest photodecomposition channel in the direct photolysis of both C2H2 and C2H4. The chemistry of H2C=C as it relates to planetary atmospheres is discussed. The vinyl radical (C2H3), important in the acetylene chemistry cycle, has been directly observed spectroscopically and the kinetics of several key reactions of this species measured.

Fahr, Askar; Herron, John; Laufer, Allan H.

1990-01-01

303

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

304

Studies of Tidal and Planetary Wave Variability in the Middle Atmosphere using UARS and Correlative MF Radar Data  

NASA Technical Reports Server (NTRS)

The goals of this research effort have been to use MF radar and UARS/HRDI wind measurements for correlative studies of large-scale atmospheric dynamics, focusing specifically on the tidal and various planetary wave structures occurring in the middle atmosphere. We believed that the two data sets together would provide the potential for much more comprehensive studies than either by itself, since they jointly would allow the removal of ambiguities in wave structure that are difficult to resolve with either data set alone. The joint data were to be used for studies of wave structure, variability, and the coupling of these motions to mean and higher-frequency motions.

Fritts, David C.

1996-01-01

305

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

306

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

307

Estimating the masses of extra-solar planets  

NASA Astrophysics Data System (ADS)

All extra-solar planet masses that have been derived spectroscopically are lower limits since the inclination of the orbit to our line-of-sight is unknown except for transiting systems. In theory, however, it is possible to determine the inclination angle, i, between the rotation axis of a star and an observer's line-of-sight from measurements of the projected equatorial velocity (vsini), the stellar rotation period (Prot) and the stellar radius (R*). For stars which host planetary systems this allows the removal of the sini dependency of extra-solar planet masses derived from spectroscopic observations under the assumption that the planetary orbits lie perpendicular to the stellar rotation axis. We have carried out an extensive literature search and present a catalogue of vsini,Prot and R* estimates for stars hosting extra-solar planets. In addition, we have used Hipparcos parallaxes and the Barnes-Evans relationship to further supplement the R* estimates obtained from the literature. Using this catalogue, we have obtained sini estimates using a Markov-chain Monte Carlo analysis. This technique allows proper 1? two-tailed confidence limits to be placed on the derived sini's along with the transit probability for each planet to be determined. While we find that a small proportion of systems yield sini's significantly greater than 1, most likely due to poor Prot estimations, the large majority are acceptable. We are further encouraged by the cases where we have data on transiting systems, as the technique indicates inclinations of ~90° and high transit probabilities. In total, we are able to estimate the true masses of 133 extra-solar planets. Of these 133 extra-solar planets, only six have revised masses that place them above the 13MJ deuterium burning limit; four of those six extra-solar planet candidates were already suspected to lie above the deuterium burning limit before correcting their masses for the sini dependency. Our work reveals a population of high-mass extra-solar planets with low eccentricities, and we speculate that these extra-solar planets may represent the signature of different planetary formation mechanisms at work. Finally, we discuss future observations that should improve the robustness of this technique.

Watson, C. A.; Littlefair, S. P.; Collier Cameron, A.; Dhillon, V. S.; Simpson, E. K.

2010-11-01

308

The aurora as a source of planetary-scale waves in the middle atmosphere. [atmospheric turbulence caused by auroral energy absorption  

NASA Technical Reports Server (NTRS)

Photographs of global scale auroral forms taken by scanning radiometers onboard weather satellites in 1972 show that auroral bands exhibit well organized wave motion with typical zonal wave number of 5 or so. The scale size of these waves is in agreement with that of well organized neutral wind fields in the 150- to 200-km region during the geomagnetic storm of May 27, 1967. Further, the horizontal scale size revealed by these observations are in agreement with that of high altitude traveling ionospheric disturbances. It is conjectured that the geomagnetic storm is a source of planetary and synoptic scale neutral atmospheric waves in the middle atmosphere. Although there is, at present, no observation of substorm related waves of this scale size at mesospheric and stratospheric altitudes, the possible existence of a new source of waves of the proper scale size to trigger instabilities in middle atmospheric circulation systems may be significant in the study of lower atmospheric response to geomagnetic activity.

Chiu, Y. T.; Straus, J. M.

1974-01-01

309

Planetary-scale wave structures of the earth's atmosphere revealed from the COSMIC observations  

NASA Astrophysics Data System (ADS)

GPS radio occultation (GPS RO) method, an active satellite-to-satellite remote sensing technique, is capable of producing accurate, all-weather, round the clock, global refractive index, density, pressure, and temperature profiles of the troposphere and stratosphere. This study presents planetary-scale equatorially trapped Kelvin waves in temperature profiles retrieved using COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellites during 2006-2009 and their interactions with background atmospheric conditions. It is found that the Kelvin waves are not only associated with wave periods of higher than 10 days (slow Kelvin waves) with higher zonal wave numbers (either 1 or 2), but also possessing downward phase progression, giving evidence that the source regions of them are located at lower altitudes. A thorough verification of outgoing longwave radiation (OLR) reveals that deep convection activity has developed regularly over the Indonesian region, suggesting that the Kelvin waves are driven by the convective activity. The derived Kelvin waves show enhanced (diminished) tendencies during westward (eastward) phase of the quasi-biennial oscillation (QBO) in zonal winds, implying a mutual relation between both of them. The El Niño and Southern Oscillation (ENSO) below 18 km and the QBO features between 18 and 27 km in temperature profiles are observed during May 2006-May 2010 with the help of an adaptive data analysis technique known as Hilbert Huang Transform (HHT). Further, temperature anomalies computed using COSMIC retrieved temperatures are critically evaluated during different phases of ENSO, which has revealed interesting results and are discussed in light of available literature.

Anisetty, S. K. A. V. Prasad Rao; Brahmanandam, P. S.; Uma, G.; Babu, A. Narendra; Huang, Ching-Yuang; Kumar, G. Anil; Ram, S. Tulasi; Wang, Hsiao-Lan; Chu, Yen-Hsyang

2014-02-01

310

Basic research in meteorology and atmospheric physics  

NASA Technical Reports Server (NTRS)

A survey is reported of methods for sounding the atmospheric temperature profile by remote measurements. The emphasis for this period was placed on sounding in the microwave region of the spectrum, sounding in cloudy atmosphere, and measuring sea temperatures remotely. Summaries of the research in the following areas are included: orbital detection of stratospheric aerosols, monthly precipitation charts for the world, determining planetary cloud structure by remote polarization measurement, analysis of Mariner 6 and 7 multicolor photometric photographs of Mars, and techniques for photometric detection of extrasolar planets.

Opstbaum, R.

1972-01-01

311

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

SciTech Connect

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

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

2005-07-15

312

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

313

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

314

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

315

Extrasolar Planet Inferometric Survey (EPIcS)  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

316

Earthshine and Extrasolar Planets  

Microsoft Academic Search

The search for life on extrasolar planets requires first that we find terrestrial-mass planets around nearby stars, and second that we determine habitability and search for signs of life. The Terrestrial Planet Finder missions, a Coronagraph (TPF-C) and an Interferometer (TPF-I in the US, also Darwin in Europe) are designed to carry out these tasks. This talk will focus on

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

2006-01-01

317

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

318

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

319

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

320

Atmospheres in a Test Tube  

NASA Astrophysics Data System (ADS)

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

Claudi, R.; Erculiani, M. S.; Giro, E.; D'Alessandro, M.; Galletta, G.

2013-09-01

321

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

322

Exploration of planetary atmospheres - Current knowledge, future opportunities and the possible role of Europe  

Microsoft Academic Search

Solar system planetology has evolved into an extended branch of the earth sciences and away from the domain of astronomy. Extraterrestrial planetary meteorological studies have thus far been focused on Mars, Venus, Jupiter, Saturn and the moon Titan. Known meteorological details of each of the well-viewed planets are reviewed, and comparisons are drawn with equivalent phenomena on earth. Several new

G. E. Hunt

1985-01-01

323

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

324

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

325

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

NSDL National Science Digital Library

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

Bell, George

2004-07-16

326

Extrasolar Planets in the Classroom  

ERIC Educational Resources Information Center

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

George, Samuel J.

2011-01-01

327

Extrasolar Planets Orbiting Active Stars  

Microsoft Academic Search

New discoveries of transiting extrasolar planets are reported weekly. Ground based surveys as well as space borne observatories like CoRoT and Kepler are responsible for filling the statistical voids of planets on distant stellar systems. I want to discuss the stellar activity and its impact on the discovery of extrasolar planets. Up to now the discovery of small rocky planets

Jörg Weingrill

2011-01-01

328

Earth-like habitats in planetary systems  

NASA Astrophysics Data System (ADS)

Understanding the concept of habitability is clearly related to an evolutionary knowledge of the particular planet-in-question. However, additional indications so-called “systemic aspects” of the planetary system as a whole governs a particular planet's claim on habitability. In this paper we focus on such systemic aspects and discuss their relevance to the formation of an “Earth-like” habitable planet. This contribution summarizes our results obtained by lunar sample work and numerical models within the framework of the Research Alliance “Planetary Evolution and Life”. We consider various scenarios which simulate the dynamical evolution of the Solar System and discuss the consequences for the likelihood of forming an Earth-like world orbiting another star. Our model approach is constrained by observations of the modern Solar System and the knowledge of its history. Results suggest that on the one hand the long-term presence of terrestrial planets is jeopardized due to gravitational interactions if giant planets are present. On the other hand the habitability of inner rocky planets may be supported in those planetary systems hosting giant planets. Gravitational interactions within a complex multiple-body structure including giant planets may supply terrestrial planets with materials which formed in the colder region of the proto-planetary disk. During these processes, water, the prime requisite for habitability, is delivered to the inner system. This may occur either during the main accretion phase of terrestrial planets or via impacts during a post-accretion bombardment. Results for both processes are summarized and discussed with reference to the lunar crater record. Starting from a scenario involving migration of the giant planets this contribution discusses the delivery of water to Earth, the modification of atmospheres by impacts in a planetary system context and the likelihood of the existence of extrasolar Earth-like habitable worlds.

Fritz, J.; Bitsch, B.; Kührt, E.; Morbidelli, A.; Tornow, C.; Wünnemann, K.; Fernandes, V. A.; Grenfell, J. L.; Rauer, H.; Wagner, R.; Werner, S. C.

2014-08-01

329

Elemental Compositions of Two Extrasolar Rocky Planetesimals  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

330

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

331

On the wavelength dependence of the effects of turbulence on average refraction angles in occultations by planetary atmospheres  

NASA Technical Reports Server (NTRS)

The dependence of the effects of planetary atmospheric turbulence on radio or optical wavelength in occultation experiments is discussed, and the analysis of Hubbard and Jokipii (1977) is criticized. It is argued that in deriving a necessary condition for the applicability of their method, Hubbard and Jokipii neglect a factor proportional to the square of the ratio of atmospheric or local Fresnel zone radius and the inner scale of turbulence, and fail to establish sufficient conditions, thereby omitting the square of the ratio of atmospheric scale height and the local Fresnel zone radius. The total discrepancy is said to mean that the results correspond to geometrical optics instead of wave optics, as claimed, thus being inapplicable in a dicussion of wavelength dependence. Calculations based on geometrical optics show that the bias in the average bending angle depends on the wavelength in the same way as does the bias in phase path caused by turbulence in a homogeneous atmosphere. Hubbard and Jokipii comment that the criterion of Haugstad and Eshleman is incorrect and show that there is a large wave optical domain where the results are independent of wavelength.

Haugstad, B. S.; Eshleman, V. R.

1979-01-01

332

Effects of Temperature Variations with Height on the Nonequilibrium Populations of Vibrational States of Molecules in Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

The model of the standard problem of radiative transfer in a vibrational-rotational band that we suggested previously (Shved and Semenov, 2001) for a nonlocal thermodynamic equilibrium (non-LTE) in vibrational molecular states is used to study the populations of these states in a nonisothermal planetary atmosphere. The temperature profile in the atmosphere is specified as a temperature perturbation in the form of a Gaussian function that is superimposed on an isothermal atmosphere. We show that the temperature profile has a complex effect on the state populations, which makes it difficult to analytically represent this effect. We investigate the influence of the peculiar features of the temperature profile in an LTE layer on the non-LTE height and suggest a criterion for determining those features that weakly affect this height. Using the populations of the CO2 0110 and 0001 states in the atmospheres of the Earth and Mars as examples, we show that the formulas suggested for estimating the non-LTE height are efficient.

Semenov, A. O.; Shved, G. M.

2003-07-01

333

Detecting Life-bearing Extrasolar Planets with Space Telescopes  

Microsoft Academic Search

One of the promising methods to search for life on extrasolar planets (exoplanets) is to detect its signature in the chemical disequilibrium of exoplanet atmospheres. Spectra at the modest resolutions needed to search for methane, oxygen, carbon dioxide, or water will demand large collecting areas and large diameters to capture and isolate the light from planets in the habitable zones

Steven V. W. Beckwith

2008-01-01

334

PHOTOMETRIC ORBITS OF EXTRASOLAR PLANETS  

SciTech Connect

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

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

2009-09-10

335

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

336

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

NASA Technical Reports Server (NTRS)

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

Steffes, P. G.

1984-01-01

337

Planetary Magnetic Dynamo Effect on Atmospheric Protection of Early Earth and Mars  

Microsoft Academic Search

\\u000a In light of assessing the habitability of Mars, we examine the impact of the magnetic field on the atmosphere. When there\\u000a is a magnetic field, the atmosphere is protected from erosion by solar wind. The magnetic field ensures the maintenance of\\u000a a dense atmosphere, necessary for liquid water to exist on the surface of Mars. We also examine the impact

V. Dehant; H. Lammer; Y. N. Kulikov; J.-M. Grießmeier; D. Breuer; O. Verhoeven; Ö. Karatekin; T. Hoolst; O. Korablev; P. Lognonné

338

Planetary Magnetic Dynamo Effect on Atmospheric Protection of Early Earth and Mars  

Microsoft Academic Search

In light of assessing the habitability of Mars, we examine the impact of the magnetic field on the atmosphere. When there\\u000a is a magnetic field, the atmosphere is protected from erosion by solar wind. The magnetic field ensures the maintenance of\\u000a a dense atmosphere, necessary for liquid water to exist on the surface of Mars. We also examine the impact

V. Dehant; H. Lammer; Y. N. Kulikov; J.-M. Grießmeier; D. Breuer; O. Verhoeven; Ö. Karatekin; T. Van Hoolst; O. Korablev; P. Lognonné

2007-01-01

339

Cold Disks around Nearby Stars. An overview of the DUNES search for ExtraSolar Kuiper-Belt Analogs  

Microsoft Academic Search

The DUNES Open Time Key Programme on Herschel represents a new opportunity to sensitively probe dusty extra-solar analogs to the Edgeworth-Kuiper Belt about nearby main sequence stars. Science Demonstration Phase and routine Herschel\\/PACS observations of debris disks have uncovered the imaging capabilities of Herschel, complementing our general understanding of extra-solar planetary systems in the solar vicinity. Direct and deconvolved images

J.-C. Augereau

2010-01-01

340

Planetary Science  

NSDL National Science Digital Library

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

Strobel, Nick

2004-07-16

341

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

342

Homogeneous studies of transiting extrasolar planets - III. Additional planets and stellar models  

Microsoft Academic Search

I derive the physical properties of 30 transiting extrasolar planetary systems using a homogeneous analysis of published data. The light curves are modelled with the JKTEBOP code, with special attention paid to the treatment of limb darkening, orbital eccentricity and error analysis. The light from some systems is contaminated by faint nearby stars, which if ignored will systematically bias the

John Southworth

2010-01-01

343

Evaluated Bimolecular Ion-Molecule Gas Phase Kinetics of Positive Ions for Use in Modeling Planetary Atmospheres, Cometary Comae, and Interstellar Clouds  

Microsoft Academic Search

Recommendations of reaction rate coefficients and product distributions for bimolecular positive ion-molecule reactions of importance in planetary atmospheres, cometary comae, and interstellar clouds are presented. Two publications Anicich and Huntress, 1986, Ap. J. Supplement Series 62, 553 and Anicich, 1993, Ap. J. Supplement Series 84, 215 served as the basis for this evaluation, which covers the literature from 1965 through

Vincent G. Anicich

1993-01-01

344

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

345

Working Group on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The Working Group on Extrasolar Planets (hereafter the WGESP) was created at a meeting of the IAU Executive Council in 1999 as a Working Group of IAU Division III and was renewed for three more years at the IAU General Assembly in 2003. The charge of the WGESP is to act as a focal point for international research on extrasolar planets. The membership of the WGESP has remained unchanged for the last three years.

Boss, Alan P.; Butler, R. Paul; Hubbard, William B.; Ianna, Philip A.; Kürster, Martin; Lissauer, Jack J.; Mayor, Michel; Meech, Karen J.; Mignard, Francois; Penny, Alan J.; Quirrenbach, Andreas; Tarter, Jill C.; Vidal-Madjar, Alfred

2007-03-01

346

Improved Ages Estimates for Extrasolar Planet Host Stars  

NASA Astrophysics Data System (ADS)

Accurate ages of extrasolar planet host stars are useful for e.g., theoretical constraints on tidal interactions between Hot Jupiters and their host stars, dynamical modeling of exoplanetary systems, and predicting planetary luminosities. We have estimated ages for 146 extrasolar planet host stars using mean Ca H & K chromospheric activity measurements (log R'HK) from the literature combined with the improved chromospheric activity-rotation-age calibrations from Mamajek & Hillenbrand (2008). The results we obtained show a fair correlation to those derived isochronally from Takeda et al. (2007), when available. We discuss some new observational constraints on the rotational evolution of solar-type dwarf stars (from spectroscopic surveys of samples of isochronally age-dated cluster and field stars), and show the limitations of the modern gyrochronology relations.

Slipski, Marek; Mamajek, E. E.

2010-01-01

347

Planetary Habitability of the Solar System  

NASA Astrophysics Data System (ADS)

Habitability is a qualitative concept generally defined as the suitability of an environment to support life. Although there are many works related to planetary habitability, there is no practical quantitative definition of habitability. The search for habitable environments in the Solar System and beyond requires a method to quantify and compare their significance. Therefore, this study presents a quantitative approach to assess the habitability of Earth and other planetary bodies. A Quantitative Habitability Model (QH Model) was develop and used to model the terrestrial habitability as a standard for comparison. The QH Model provides a simple ecophysiology-based framework that can be used to predict the potential distribution, abundance and productivity of life in planetary bodies from local to global scales. The simplest QH Model calculates habitability from the environment temperature and relative humidity in gas phases (i.e. atmospheres), and from temperature and salinity in liquid phases (i.e. oceans). The model was used to explain the latitudinal gradients of primary producers on Earth and was validated with ground and satellites observations of net primary productivity (NPP). The potential global habitability for prokaryotes of the upper-troposphere of Venus, the subsurface of Mars, Europa, Titan, and Enceladus was compared. Results show that Enceladus has the zone with the highest mean habitability in the Solar System although to deep for direct exploration. Results also show that the current global terrestrial environment of land areas is not optimized for primary producers, but it was during some paleoclimates. The QH Model has applications in ecosystem modeling, global climate studies including paleoclimates and global warming, planetary protection, and astrobiology. It can also be used to quantify the potential for life of any terrestrial-size extrasolar planet as compared to Earth. This study was partially supported by UPR Arecibo and NASA Astrobiology Institute.

Mendez, Abel

2009-09-01

348

Detecting Life-bearing Extrasolar Planets with Space Telescopes  

Microsoft Academic Search

One of the promising methods to search for life on extra-solar planets\\u000a(exoplanets) is to detect life's signatures in their atmospheres. Spectra of\\u000aexoplanet atmospheres at the modest resolution needed to search for oxygen,\\u000acarbon dioxide, water, and methane will demand large collecting areas and large\\u000adiameters to capture and isolate the light from planets in the habitable zones\\u000aaround

Steven V. W. Beckwith

2007-01-01

349

Application of asymptotic expressions for computing the polarized radiation in optically thick planetary atmospheres  

NASA Astrophysics Data System (ADS)

For optically thick plane-parallel homogeneous atmospheres the internal and emerging radiation may be calculated using one of the standard methods to solve radiative transfer problems. Alternatively, this radiation may be approximated by using so-called asymptotic expressions, which involve the reflection properties of the corresponding semi-finite atmosphere and the leading eigensolution of the equation of radiative transfer. In this paper we illustrate the accuracy of these approximations for an atmosphere containing Venus cloud particles. It is shown that for conservative and near conservative scattering in this Venus atmosphere the approximations give accurate results for the reflected, midlevel and transmitted polarized radiation if the optical thickness is larger than 3, 20 and 10, respectively. In addition, accurate numerical values of quantities pertaining to the asymptotic expressions have been tabulated.

Wauben, W. M. F.; de Haan, J. F.; Hovenier, J. W.

1994-01-01

350

Planetary atmosphere representation for Monte-Carlo simulation of aerospace vehicle trajectories  

NASA Technical Reports Server (NTRS)

Methods of simulating large scale random atmospheric variations are examined for use in Monte Carlo simulations of hypervelocity vehicles. Random density, temperature, and pressure variations have a significant impact on the performance of such vehicles. Methods for generating random atmosphere profiles are described and compared in the context of a Monte Carlo simulation of the Aeroassist Flight Experiment (AFE). It is seen that these techniques result in statistically significant differences in key simulation point statistics.

Dutton, K.; Moerder, D.; Queen, E.; Suit, W.

1990-01-01

351

A Grant from NASA's Office of Space Station Science, Planetary Atmosphere's Program to Boston University  

NASA Technical Reports Server (NTRS)

In the past three years of this program we have made contributions to a variety of subjects in research on Jupiter's Atmosphere, the Ultraviolet Spectroscopy of Jupiter, the abundance of CH4 in Pluto's atmosphere, and the emissivity of Pluto's Surface. We also performed work on two projects related to Titan, and an analysis of the visible spectrum of a brown dwarf. The highpoints are briefly summarized and a list of papers supported partly or wholly by this program is also provided.

Yelle, Roger V.

2000-01-01

352

Program package for the computer-aided aerodynamic design system for descent vehicles in planetary atmospheres  

NASA Astrophysics Data System (ADS)

The mathematical support for the calculation of the aerodynamics and flight trajectory of descent vehicles (DVs) entering the Earth's atmosphere from space is considered. The study of the aerodynamics of a segment- and cone-shaped DV is carried out under a wide range of atmospheric entry conditions. Comparison of the results of the calculations of aerodynamic characteristics of the "Phobos-Grunt" DV and of the data of wind tunnel tests of its models is presented.

Golomazov, M. M.; Finchenko, V. S.; Ivankov, A. A.; Shmatov, S. I.

2012-12-01

353

A method for computing visible and infrared polarized monochromatic radiation in planetary atmospheres  

NASA Astrophysics Data System (ADS)

In this paper we present a computational method, based on the so-called adding principle, for calculating the polarized monochromatic radiation in plane-parallel vertically inhomogeneous atmospheres. Our computer code is verified by comparing numerical results with those obtained by other investigators using different methods. We consider not only the well-known case of illumination by a unidirectional beam of light at the top of the atmosphere, but also illumination by isotropically radiating internal sources and illumination by an isotropically radiating ground surface below the atmosphere. Numerical results for all relevant Stokes parameters are tabulated for a two-layer atmosphere containing molecules and haze particles. These results pertain to the three types of illumination mentioned above. Furthermore, we describe some general features of polarized radiation in an optically thick homogeneous atmosphere containing cloud C1 water droplets. It is shown that multiple scattering of radiation in such a cloudy atmosphere may not be ignored at infrared wavelengths if molecular absorption is negligible.

Wauben, W. M. F.; de Haan, J. F.; Hovenier, J. W.

1994-02-01

354

Toward a Model for Detecting Life on Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The search for life extraterrestrial life has rapidly expanded during the past several years. In addition to missions to Mars and Europa, NASA now envisions launching an orbiting telescope, Terrestrial Planet Finder (TPF), capable of resolving Earth-sized planets around stars as far away as 50 parsecs within the next 10-15 years. By that time we need to develop our understanding of the effects of life on such planets in order to confidently distinguish inhabited planets from barren ones. Our group is in the process of developing a fully coupled generalized 1-D radiative transfer-atmospheric chemistry model. Around this core we are building the Virtual Planetary Laboratory (VPL) to generate synthetic spectra of hypothetical extrasolar terrestrial planets. Computational modules mimicking the influence of life on atmospheric chemistry/climate are of central importance for analyzing data from TPF and related missions. Here we describe our rationale and initial efforts to parameterize the effects of life using a Virtual Microbial Community (VMC). At first glance, the task of modeling hypothetical inhabited planets appears intractable. However, we may assume that most planets settle into a fairly small number of stable climate/chemistry regimes during their history. These regimes are maintained by negative feedback loops. Transitions from one stable solution to another are singularities, times during which the system is unregulated and may vary wildly. In this context, life is one of several processes modifying the chemical composition of a planetary atmosphere, potentially modifying climate. We seek to elucidate those processes and signatures unique to life and visible from space. The VMC is a first attempt at quantifying the possible range of effects of life on the atmosphere of a planet. We start from the presumption that kinetics and thermodynamics are the same throughout the universe. Given the remarkable metabolic diversity of life on Earth, we assume that all available energy sources may be used by biology on detectably colonized planets. Simple feedback loops such as those governing Lovelock?s famous Daisyworld or the Walker CO2 feedback, offer starting points for thinking about global scale feedbacks. Feedbacks in microbial communities, e.g. those postulated in anaerobic methane oxidation communities, involving the use of one or more organisms? waste products as nutrients by another, hint at the local complexity from which we need to scale up. Our first attempt at bridging this gap involves describing the processes that may have helped stabilize the Archean climate. Archean biogenic methane production could have been rapid enough to provide 100s ppm atmospheric CH4. At such CH4 levels Earth would have remained ice free. Sudden increases in CH4 production might have led to runaway greenhouse conditions. However, if CH4/CO2 > 1 a UV absorbing aerosol haze should form. UV-labile ammonia could have accumulated in the atmosphere under the haze, quickly making rain pH > 7, dramatically slowing chemical weathering on the continents and interrupting vital phosphate delivery to the oceans. The residence time of P is ca.10,000 years. Thus, over a time scale of ca.10,000 years primary productivity dropped sharply. Biogenic methane production, near the base of the trophic ladder, suffered disproportionately. With little CH4 production CH4/CO2 fell to < 1. The UV screen and atmospheric NH3 disappeared in a few years. Rain pH dropped. Weathering restarted. Biological productivity recovered. The above testable scenario serves as an example of a plausible feedback involving interplay between biological, geochemical, atmospheric and stellar processes. Feedback loops of this sort will be central features of the fully realized VMC module for the VPL.

Rye, R.; Storrie-Lombardi, M.

2001-12-01

355

STEM Colorado: Simplified Planetary Transits  

NSDL National Science Digital Library

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

Mccray, Richard; Koelemay, Andrew

2008-10-22

356

Outer satellite atmospheres: Their nature and planetary interactions. [atmospheric models for Amalthea, Ganymede, Callisto, and Titan are presented  

NASA Technical Reports Server (NTRS)

Results show that Amalthea is likely to form a tightly-bound partial toroidal-shaped hydrogen cloud about its planet, while Ganymede, Callisto and Titan may have rather large, complete and nearly symmetric toroidal-shaped clouds. The toroidal cloud for Amalthea compares favorably with spacecraft data of Pioneer 10 for a satellite escape flux of order 10 to the 11th power atoms/sq cm/sec. Model results for Ganymede, Callisto and Titan suggest that these extended hydrogen atmospheres are likely to be detected by the Voyager spacecrafts and that Titan's cloud might also be detected by the Pioneer 11 spacecraft. Ions created because of atoms lost through ionization processes from these four extended hydrogen atmospheres and from the sodium cloud of Io are discussed.

Smyth, W. H.

1978-01-01

357

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

NASA Technical Reports Server (NTRS)

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

Smyth, W. H.

1980-01-01

358

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

PubMed

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

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

2011-06-01

359

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

PubMed Central

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

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

2011-01-01

360

The outer limit of the life supporting zone of exoplanets having CO2-rich atmospheres: Virtual exoplanets and Kepler planetary candidates  

NASA Astrophysics Data System (ADS)

CO2 rich atmospheres have been considered for the outer limit of the classic water habitable zone. Here we provide a database for the outer limit of the life supporting zone consisting of a sulfuric acid, a water and a water/ammonia mixture (15 wt% ammonia) habitable zone for virtual exoplanets having CO2-rich atmospheres and orbiting G-, K-, or M-dwarf stars. We used recent CO2 line and continuum absorption data for CO2 pressures up to 100 bar for our simulations. Scenarios for different stellar spectra, stellar fluxes, planetary surface albedos, atmospheric pressures and planetary masses are explored. One notable result is that the surface temperature does not strongly increase if CO2 pressure is larger than approximately 25 bar, due to increased Rayleigh scattering or CO2 condensation at the surface and a thereby reduced greenhouse effect in these cases. The database is created for virtual exoplanets and applied to Kepler planetary candidates. All of the considered planetary candidates likely lie within the outer limit of the life supporting zone.

Neubauer, David; Leitner, Johannes J.; Firneis, Maria Gertrude; Hitzenberger, Regina

2013-08-01

361

Zeppelin NT - Measurement Platform for the Exploration of Atmospheric Chemistry and Dynamics in the Planetary Boundary Layer  

NASA Astrophysics Data System (ADS)

The planetary boundary layer (PBL) is the chemically most active and complex part of the atmosphere where freshly emitted reactive trace gases, tropospheric radicals, atmospheric oxidation products and aerosols exhibit a large variability and spatial gradients. In order to investigate the chemical degradation of trace gases and the formation of secondary pollutants in the PBL, a commercial Zeppelin NT was modified to be used as an airborne measurement platform for chemical and physical observations with high spatial resolution. The Zeppelin NT was developed by Zeppelin Luftschifftechnik (ZLT) and is operated by Deutsche Zeppelin Reederei (DZR) in Friedrichshafen, Germany. The modification was performed in cooperation between Forschungszentrum Jülich and ZLT. The airship has a length of 75 m, can lift about 1 ton of scientific payload and can be manoeuvered with high precision by propeller engines. The modified Zeppelin can carry measurement instruments mounted on a platform on top of the Zeppelin, or inside the gondola beneath the airship. Three different instrument packages were developed to investigate a. gas-phase oxidation processes involving free radicals (OH, HO2) b. formation of secondary organic aerosols (SOA) c. new particle formation (nucleation) The presentation will describe the modified airship and provide an overview of its technical performance. Examples of its application during the recent PEGASOS flight campaigns in Europe will be given.

Hofzumahaus, Andreas; Holland, Frank; Oebel, Andreas; Rohrer, Franz; Mentel, Thomas; Kiendler-Scharr, Astrid; Wahner, Andreas; Brauchle, Artur; Steinlein, Klaus; Gritzbach, Robert

2014-05-01

362

4-8 day planetary waves in the middle and upper atmosphere: What can theory and modeling tell us about the observations we make.  

NASA Astrophysics Data System (ADS)

Planetary waves with periods ranging from four to eight days are often observed in the mesosphere and lower thermosphere. At times these global scale waves exhibit characteristics like those of the 1st symmetric Rossby normal mode for zonal wave number one, often referred to as the 5-day wave. At other times the period and seasonality of these waves suggest behavior unexpected from a normal mode propagating upward from the troposphere. Planetary wave propagation theory and a series of modeling experiments will be used to study global scale oscillations with periods around 5 days. Vertical propagation characteristics will be examined over the course of a year using realistic representations of the atmosphere, dissipation, and of lower atmospheric forcing. Mechanisms other than lower atmospheric forcing, such as an in-situ realization of normal mode in the face of broad-band forcing, and instabilities of the mean state will also be examined.

Meyer, C. K.

2001-12-01

363

High resolution infrared spectroscopy: Some new approaches and applications to planetary atmospheres  

NASA Technical Reports Server (NTRS)

The principles of spectral line formation and of techniques for retrieval of atmospheric temperature and constituent profiles are discussed. Applications to the atmospheres of Earth, Mars, Venus, and Jupiter are illustrated by results obtained with Fourier transform and infrared heterodyne spectrometers at resolving powers (lambda/delta hyperon lambda of approximately 10,000 and approximately 10 to the seventh power), respectively, showing the high complementarity of spectroscopy at these two widely different resolving powers. The principles of heterodyne spectroscopy are presented and its applications to atmospheric probing and to laboratory spectroscopy are discussed. Direct absorption spectroscopy with tuneable semiconductor lasers is discussed in terms of precision frequency-and line strength-measurements, showing substantial advances in laboratory infrared spectroscopy.

Mumma, M. J.

1978-01-01

364

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

NASA Technical Reports Server (NTRS)

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

Abbas, M. M.

1978-01-01

365

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

NASA Technical Reports Server (NTRS)

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

Lewis, J. S.

1976-01-01

366

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

NASA Technical Reports Server (NTRS)

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

Fox, J. L.

1984-01-01

367

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

Microsoft Academic Search

A telescope floating in the polar stratosphere can continuously monitor planets for more than 24 hours. Thin, clear and stable air of the stratosphere makes it possible to observe planets in a condition free from cloud with fine seeing and high atmospheric transmittance. Moreover, a balloon-borne telescope system is less expensive compared with a huge terrestrial telescope or a direct

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

2007-01-01

368

Molecular nitrogen photoabsorption cross section measurements and models in support of planetary atmospheres  

Microsoft Academic Search

A detailed understanding of the N2 photoabsorption spectrum in the 80 to 100 nm region is essential for interpretations of occultation and airglow measurements of the nitrogen-rich atmospheres of the Earth, Titan, and Triton. We report measurements of fundamental parameters of the absorption spectrum of 14 N2 in the 90 to 100 nm spectral region along with the development of

Glenn Stark; Peter Smith; Brenton Lewis; Alan Heays; Kenji Ito

2008-01-01

369

Planetary wave coupling of the low latitude atmosphere-ionosphere system  

Microsoft Academic Search

The lower middle and upper atmosphere regions compose a strongly coupled system in which phenomena occurring at one height can have profound effects elsewhere The mesosphere lower thermosphere MLT region is a critical region in the vertical coupling since here the physical processes filter and shape the flux of waves and tides ascending through the mesosphere into the overlaying thermosphere

D. V. Pancheva; P. J. Mukhtarov; M. G. Shepherd; N. J. Mitchell; D. C. Fritts; D. M. Riggin; P. P. Batista; M. A. Abdu; I. S. Batista; B. R. Clemesha; T. Kikuchi

2006-01-01

370

The Martian atmospheric planetary boundary layer stability, fluxes, spectra, and similarity  

Microsoft Academic Search

This is the first analysis of the high frequency data from the Viking lander and spectra of wind, in the Martian atmospheric surface layer, along with the diurnal variation of the height of the mixed surface layer, are calculated for the first time for Mars. Heat and momentum fluxes, stability, and zO are estimated for early spring, from a surface

James E. Tillman

1994-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

372

Planetary quarantine  

NASA Technical Reports Server (NTRS)

Those areas of future missions which will be impacted by planetary quarantine (PQ) constraints were identified. The specific objectives for this reporting period were (1) to perform an analysis of the effects of PQ on an outer planet atmospheric probe, and (2) to prepare a quantitative illustration of spacecraft microbial reduction resulting from exposure to space environments. The Jupiter Orbiter Probe mission was used as a model for both of these efforts.

1977-01-01

373

Clouds in the atmospheres of extrasolar planets. I. Climatic effects of multi-layered clouds for Earth-like planets and implications for habitable zones  

Microsoft Academic Search

Aims: The effects of multi-layered clouds in the atmospheres of Earth-like planets orbiting different types of stars are studied. The radiative effects of cloud particles are directly correlated with their wavelength-dependent optical properties. Therefore the incident stellar spectra may play an important role for the climatic effect of clouds. We discuss the influence of clouds with mean properties measured in

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

2010-01-01

374

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

NASA Technical Reports Server (NTRS)

The existence of ice covered rivers on Mars is considered. It is noted that the evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. It is determined that even with a mean Martian insolation rate above the ice of approximately 10 to the -8th g per sq cm/sec, a flowing channel of liquid water will be covered by ice which evaporates sufficiently slowly that the water below can flow for hundreds of kilometers even with modest discharges. Evaporation rates are calculated for a range of frictional velocities, atmospheric pressures, and insolations and it is suggested that some subset of observed Martian channels may have formed as ice-choked rivers. Finally, the exobiological implications of ice covered channels or lakes on Mars are discussed.

Wallace, D.; Sagan, C.

1979-01-01

375

Molecular Nitrogen Photoabsorption Cross Section Measurements and Models in Support of Planetary Atmospheres  

Microsoft Academic Search

The analyses of existing and planned vacuum ultraviolet occultation measurements of the N2-rich atmospheres of Titan, Triton, and Pluto require reliable photoabsorption cross sections for the approximately 100 bands of N2 in the 80 to 100 nm wavelength region. We report measurements of fundamental parameters of the absorption spectrum of 14N2 along with the development of a new, physically-based, quantum-mechanical

G. Stark; P. L. Smith; B. R. Lewis

2007-01-01

376

Vacuum ultraviolet molecular nitrogen photoabsorption cross sections for planetary atmospheric transmission models  

Microsoft Academic Search

The analyses of VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2. In particular, there is a need for reliable photoabsorption f-values and line widths for the ~ 100 electronic bands of N2 in the 80 to 100 nm wavelength region. As part of our continuing program

G. Stark; P. L. Smith; K. Yoshino; J. Rufus; K. P. Huber

2001-01-01

377

Molecular Nitrogen Photoabsorption Cross Section Measurements and Models in Support of Analyses of Planetary Atmospheres  

Microsoft Academic Search

The analyses of existing and planned vacuum ultraviolet occultation measurements of the N2-rich atmospheres of Titan, Triton, and Pluto require reliable photoabsorption cross sections for the approximately 100 bands of N2 in the 80 to 100 nm wavelength region. We report measurements of fundamental parameters of the absorption spectrum of 14N2 along with the development of a new, physically-based, quantum-mechanical

Glenn Stark; B. R. Lewis; S. T. Gibson; A. Heays; P. L. Smith

2006-01-01

378

Noble gas components in planetary atmospheres and interiors in relation to solar wind and meteorites  

Microsoft Academic Search

We discuss observed xenon isotopic signatures in solar system reservoirs and possible relationships. The predominant trapped\\u000a xenon component in ordinary chondrites (OC) is OC-Xe and its isotopic signature differs from Xe in ureilites, in carbonaceous\\u000a chondrites, in the atmospheres of Earth and Mars, and in the solar wind. Additional minor Xe components were identified in\\u000a type 3 chondrites and in

K. Marti; K. J. Mathew

1998-01-01

379

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

Microsoft Academic Search

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

N. C. Parikh; J. A. Zollweg

1996-01-01

380

New planetary atmosphere simulations: application to the organic aerosols of Titan.  

PubMed

The atmosphere of Titan partly consists of hazes and aerosol particles. Experimental simulation is one of the powerful approaches to study the processes which yield these particles, and their chemical composition. It provides laboratory analogues, sometimes called tholins. Development and optimization of experimental tools were undertaken in order to perform chemical and physical analyses of analogues under conditions free from contamination. A "Titan aerosol generator" was developed in the frame of the Cassini-Huygens mission, in order to produce Titan's aerosol analogues within conditions closer to those of the titanian atmosphere: cold plasma simulation system, low pressure and low temperature. The direct current (DC) glow discharge is produced by applying a DC voltage between two conductive electrodes inserted into the gas mixture-model of the studied atmosphere- at low pressure. A high-impedance power supply is used to provide the electrical field. All the system is installed in a glove box, which protect samples from any contamination. Finally the research program expected with this new material is presented. PMID:11541340

Coll, P; Cosia, D; Gazeau, M C; Raulin, F

1997-01-01

381

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

NASA Technical Reports Server (NTRS)

Laboratory measurements of microwave and millimeter wave properties of the simulated atmosphere of the outer planets and their satellites has continued. One of the focuses is on the development of a radiative transfer model of the Jovian atmosphere at wavelengths from 1 mm to 10 cm. This modeling effort led to laboratory measurements of the millimeter wave opacity of hydrogen sulfide (H2S) under simulated Jovian conditions. Descriptions of the modeling effort, the Laboratory experiment, and the observations are presented. Correlative studies of measurements with Pioneer-Venus radio occultation measurements with longer wavelength emission measurements have provided new ways for characterizing temporal and spatial variations in the abundance of both gases H2SO4 and SO2, and for modeling their roles in the subcloud atmosphere. Laboratory measurements were conducted on 1.35 cm (and 13 cm) opacity of gaseous SO2 and absorptivity of gaseous SO2 at the 3.2 mm wavelength under simulated Venus conditions. Laboratory measurements were completed on millimeter wave dielectric properties of liquid H2SO4, in order to model the effects of the opacity of the clouds of Venus onto millimeter wave emission spectrum.

Steffes, Paul G.

1991-01-01

382

STEM Colorado: Planetary Transits  

NSDL National Science Digital Library

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

Mccray, Richard; Koelemay, Andrew

2008-08-30

383

Planet Finder: Discovering Extra-solar Planets Exercise  

NSDL National Science Digital Library

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

Mccray, Richard; Koelemay, Andrew

2008-11-04

384

Data analysis on the extrasolar planets using robust clustering  

NASA Astrophysics Data System (ADS)

We use both the conventional and more recently developed methods of cluster analysis to study the data of extrasolar planets (exoplanets). Using the data set with planetary mass M, orbital period P and orbital eccentricity e, we investigate the possible clustering in the lnM, lnP, lnP-lnM, e and ln P-e spaces. There are two main implications: (1) mass distribution is continuous, and (2) orbital population could be classified into three clusters, which correspond to the exoplanets in the regimes of tidal, ongoing tidal and disc interaction, respectively.

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

2006-08-01

385

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

NASA Technical Reports Server (NTRS)

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

Valentin, J. R.

1989-01-01

386

Planetary Interior Evolution and Life  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

387

Mathematics of Radiation Propagation in Planetary Atmospheres: Absorption, Refraction, Time Delay, Occultation, and Abel Inversion  

NASA Astrophysics Data System (ADS)

Forward integration calculation of air mass, refraction, and time delay requires care even for very smooth model atmospheres. The literature abounds in examples of injudicious approximations, assumptions, transformations, variable substitutions, and failures to verify that the formulas work with unlimited accuracy for simple cases and also survive challenges from mathematically pathological but physically realizable cases. A few years ago we addressed the problem of evaluation of the Chapman function for attenuation along a straight line path in an exponential atmosphere. In this presentation we will describe issues and approaches for integration over light paths curved by refraction. The inverse problem, determining the altitude profile of mass density (index of refraction) or the concentration of an individual chemical species (absorption), from occultation data, also has its mathematically interesting (i.e., difficult) aspects. Now we automatically have noise and thus statistical analysis is just as important as calculus and numerical analysis. Here we will describe a new approach of least-squares fitting occultation data to an expansion over compact basis functions. This approach, which avoids numerical differentiation and singular integrals, was originally developed to analyze laboratory imaging data.Forward integration calculation of air mass, refraction, and time delay requires care even for very smooth model atmospheres. The literature abounds in examples of injudicious approximations, assumptions, transformations, variable substitutions, and failures to verify that the formulas work with unlimited accuracy for simple cases and also survive challenges from mathematically pathological but physically realizable cases. A few years ago we addressed the problem of evaluation of the Chapman function for attenuation along a straight line path in an exponential atmosphere. In this presentation we will describe issues and approaches for integration over light paths curved by refraction. The inverse problem, determining the altitude profile of mass density (index of refraction) or the concentration of an individual chemical species (absorption), from occultation data, also has its mathematically interesting (i.e., difficult) aspects. Now we automatically have noise and thus statistical analysis is just as important as calculus and numerical analysis. Here we will describe a new approach of least-squares fitting occultation data to an expansion over compact basis functions. This approach, which avoids numerical differentiation and singular integrals, was originally developed to analyze laboratory imaging data.

Huestis, D. L.

388

Vibrational Spectroscopy of Ions and Radicals Present in the Interstellar Medium and in Planetary Atmospheres: A Theoretical Study  

NASA Technical Reports Server (NTRS)

Anharmonic vibrational frequencies and intensities are calculated for OH(H2O)n and H(H2O)n radicals (that form on icy particles of the interstellar medium), HCO radical (the main intermediate in the synthesis of organic molecules in space), NH2(-) and C2H(-) anions, H5(+) cation, and other systems relevant to interstellar chemistry. In addition to pure ions and radicals, their complexes with water are studied to assess the effects of water environment on infrared spectra. The calculations are performed using the correlation-corrected vibrational self-consistent field (CC-VSCF) method with ab initio potential surfaces at the MP2 and CCSD(T) levels. Fundamental, overtone, and combination excitations are computed. The results are in good agreement with available experimental data and provide reliable predictions for vibrational excitations not yet measured in laboratory experiments. The data should be useful for interpretation of astronomically observed spectra and identification of ions and radicals present in the interstellar medium and in planetary atmospheres.

Chaban, Galina M.

2004-01-01

389

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

390

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

NASA Astrophysics Data System (ADS)

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

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

2006-02-01

391

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

392

Compact remote Raman and LIBS system for detection of minerals, water, ices, and atmospheric gases for planetary exploration  

NASA Astrophysics Data System (ADS)

At the University of Hawaii, we have developed a compact, portable remote Raman and Laser-Induced Breakdown Spectroscopy (LIBS) system with a 532 nm pulsed laser for planetary exploration under the Mars Instrument Development Program. The compact time-resolved remote Raman and LIBS system consists of (i) a regular 85 mm Nikon (F/1.8) camera lens with clear aperture of 50 mm as collection optics, (ii) a miniature spectrograph that occupies 1/14th the volume of a comparable commercial spectrograph from Kaiser Optical Systems Inc., (iii) a custom mini-ICCD detector, and (iv) a small frequency-doubled 532 nm Nd:YAG pulsed laser (30 mJ/pulse, 20 Hz) with a 10x beam expander. In the standoff Raman mode the system is capable of measuring various minerals, water, ices, and atmospheric gases from a 50 meter range with a 10 s integration time. At shorter distances of 10 m or less, good quality Raman spectra can be obtained within 1 s. The time-gated system is capable of detecting both the target mineral as well as the atmospheric gases before the target using their Raman fingerprints. Various materials can easily be identified through glass, plastic, and water media. The time-gating capability makes the system insensitive to window material, which is highly desirable for future missions to Venus where instruments are expected to be within the lander. The standoff LIBS range is 10 m and LIBS spectra of various minerals can be obtained with single laser pulse excitation. The standoff LIBS capability provides additional elemental verification of the targeted material.

Misra, Anupam K.; Sharma, Shiv K.; Acosta, Tayro E.; Bates, David E.

2011-05-01

393

ExoMol: Large-scale production of line lists for molecules important for modelling of planetary atmospheres  

NASA Astrophysics Data System (ADS)

The spectral characterization of astrophysical objects cool enough to form polyatomic molecules (the atmospheres of planets, brown dwarfs, planetary discs etc.) requires a huge amount of fundamental molecular data. With a few exceptions the existing molecular line lists are not sufficiently accurate and complete. The aim of ExoMol [1] is to generate comprehensive line lists for all molecules likely to be observable in exoplanet atmospheres in the foreseeable future (see www.exomol.com for more details). We identified the following 40 species that are important sources of opacity in (exo)planets and brown dwarfs and where there is currently a lack of fundamental data on wavelength and temperature-dependent absorption: • Diatomics: AlO, AlH, BeH, CaH, C2, CrH, FeH, HF, HCl, KCl, MgH, MgO, NaH, NaCl, NiH, O2,SiO, SiH, S2, SH, TiH, TiO, VO, YO • Triatomics: C3, H2S, SO2 • Tetratomics: H2CO, H2CS, HCCH, HOOH, PH3,SO3 • Pentatomics: CH4, HNO3 • Larger molecules: C2H4, C2H6, C3H8, P2H2, P2H4 The production of comprehensive and very large rotation-vibration and rotation-vibration-electronic line lists requires a mixture of first principles quantum mechanical methods and empirical tuning based on laboratory spectroscopic data and makes extensive use of state-of-the-art computing. These and other aspects of molecular line lists, their production and astrophysical applications will be discussed. The contribution will make specific reference to molecules for which line lists have recently been completed or are nearing completion: phosphine, hydrogen sulphide, hydrogen peroxide, methane, formaldehyde, nitric acid as well as to a number of diatomic molecules of astrophysical importance, see Fig. 1.

Yurchenko, S.; Tennyson, J.

2013-09-01

394

Radio Search For Extrasolar Planets  

NASA Astrophysics Data System (ADS)

Theoretical justification and ongoing observational efforts in view of detecting radio emissions from extrasolar planets will be presented. On the "prediction" side, a heuris- tic scaling law has been established relating the radio output of any magnetized flow- obstacle system to the incident magnetic energy flux on the obstacle. Its confirmation by the observation of radio emission from extrasolar planets would help to understand the energy budget of such a system. On the "detection" side, specific procedures have been developed for interference mitigation and weak burst detection.

Zarka, P.

395

The Synergistic Use of NASA's A-Train Observations to Characterize the Planetary Boundary Layer and Enable Improved Understanding and Prediction of Land-Atmosphere Interactions  

Microsoft Academic Search

The planetary boundary layer (PBL) serves as a short-term memory of land-atmosphere (L-A) interactions through the diurnal integration of surface fluxes and subsequent evolution of PBL fluxes and states. Recent advances in satellite remote sensing offer the ability to monitor PBL and land surface properties at increasingly high spatial and temporal resolutions and, consequently, have the potential to provide valuable

B. Zavodsky; J. A. Santanello; M. A. Friedl; J. Susskind; S. P. Palm

2010-01-01

396

Impact induced dehydration of serpentine and the evolution of planetary atmospheres  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

397

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

398

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

NASA Technical Reports Server (NTRS)

Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines