<i>Atmospheric</i> moons Galileo would have loved

Atreya, S. K.

doi:10.1017/s1743921310007349

Cited by 4 publications

(8 citation statements)

References 22 publications

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“…This combined with advances in understanding the high-pressure microwave absorption of ammonia, which possesses a strong inversion band just longward of 1-cm wavelength, led to a consistent story of deeply convective atmospheres with ammonia as the dominant absorber (Gulkis and Poynter, 1972;Berge and Gulkis, 1976;Klein and Gulkis, 1978). The whole disk spectrum through the microwave region for Saturn led to a value for the deep atmosphere mixing ratio of ammonia of about three times the solar abundance, value consistent with previous work (de Pater, 1990;Atreya, 2010), and our analysis in L13. The measured disk temperature spectrum of Saturn may be found in de Pater and Massie (1985) and van der Tak et al (1999).…”

Section: Introductionsupporting

confidence: 83%

“…The JAMRT program has the capability to compute radiometric brightness temperatures for user-selectable absorber concentrations and cloud properties of condensable species, including their relative humidities in the cloud regions. Table 4 gives an estimate of Saturn's deep atmosphere composition based on values derived from Atreya (2010). Fig.…”

Section: Emission Modelmentioning

confidence: 99%

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Saturn’s thermal emission at 2.2-cm wavelength as imaged by the Cassini RADAR radiometer

Janssen

Ingersoll

Allison

et al. 2013

Icarus

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a b s t r a c tWe present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10°planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at À35°latitude; occasional large oval features with depleted ammonia around À45°latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.

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Section: Introductionsupporting

confidence: 83%

Section: Emission Modelmentioning

confidence: 99%

Saturn’s thermal emission at 2.2-cm wavelength as imaged by the Cassini RADAR radiometer

Janssen

Ingersoll

Allison

et al. 2013

Icarus

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“…At very low temperatures ( T ≲ 300 K), H 2 O itself condenses out of the upper atmosphere, making spectroscopic observations of H 2 O in super-Earths extremely challenging, similar to the challenges in measuring H 2 O abundances in giant planets in the solar system (see e.g. Atreya 2010). On the other hand, even for warmer atmospheres ( T ~300–1000 K), several other volatile species, such as NaCl, KCl, Na 2 S, etc., can condense out leading to cloudy super-Earth atmospheres in this temperature range, as is likely the case with the super-Earth GJ 1214b (Bean et al 2011; Morley et al 2013).…”

Section: Constraints From Atmospheric Spectramentioning

confidence: 99%

Optimal measures for characterizing water-rich super-Earths

Madhusudhan

Redfield

2014

International Journal of Astrobiology

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The detection and atmospheric characterization of super-Earths is one of the major frontiers of exoplanetary science. Currently, extensive efforts are underway to detect molecules, particularly H 2 O, in super-Earth atmospheres. In the present work, we develop a systematic set of strategies to identify and observe potentially H 2 O-rich super-Earths that provide the best prospects for characterizing their atmospheres using existing instruments. Firstly, we provide analytic prescriptions and discuss factors that need to be taken into account while planning and interpreting observations of superEarth radii and spectra. We discuss how observations in different spectral bandpasses constrain different atmospheric properties of a super-Earth, including radius and temperature of the planetary surface as well as the mean molecular mass, the chemical composition and thermal profile of the atmosphere. In particular, we caution that radii measured in certain bandpasses can induce biases in the interpretation of the interior compositions. Secondly, we investigate the detectability of H 2 Orich super-Earth atmospheres using the HST WFC3 spectrograph as a function of the planetary properties and stellar brightness. We find that highly irradiated super-Earths orbiting bright stars, such as 55 Cancri e, present better candidates for atmospheric characterization compared to cooler planets such as GJ 1214b even if the latter orbit lower-mass stars. Besides being better candidates for both transmission and emission spectroscopy, hotter planets offer higher likelihood of cloud-free atmospheres which aid tremendously in the observation and interpretation of spectra. Finally, we present case studies of two super-Earths, GJ 1214b and 55 Cancri e, using available data and models of their interiors and atmospheres. Subject headings: planetary systems -planets and satellites: general -planets and satellites: individual (GJ 1214 b, 55 Cancri e)

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“…Table 1 gives the atmospheric constituents and their respective abundances in the model atmosphere, including the values used for the solar abundances. H 2 O, NH 3 , PH 3 , and H 2 S are the condensable gases (Atreya, 2010). H 2 S reacts with NH 3 to form an NH 4 SH cloud with a base around 5 bars.…”

Section: Observations and Radiative Transfer Modelmentioning

confidence: 99%

“…The water cloud is deeper (base $10 bars) and out of the sensitivity range of the 2.2-cm Table 1 Abundances of atmospheric constituents in the JAMRT program. Solar and enrichment values are from Atreya (2010), who calculated solar abundances from the photospheric values of Grevesse et al (2005 weighting function. In the model, the presence of the ammonia ice cloud particles does not affect the 2.2-cm brightness temperature significantly, although the depletion of ammonia vapor by the formation of the clouds does.…”

Section: Observations and Radiative Transfer Modelmentioning

confidence: 99%

Analysis of Saturn’s thermal emission at 2.2-cm wavelength: Spatial distribution of ammonia vapor

Laraia

Ingersoll

Janssen

et al. 2013

Icarus

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This work focuses on determining the latitudinal structure of ammonia vapor in Saturn's cloud layer near 1.5 bars using the brightness temperature maps derived from the Cassini RADAR (Elachi et al. [2004], Space Sci. Rev. 115, 71-110) instrument, which works in a passive mode to measure thermal emission from Saturn at 2.2-cm wavelength. We perform an analysis of five brightness temperature maps that span epochs from 2005 to 2011, which are presented in a companion paper by Janssen et al.

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Atmospheric moons Galileo would have loved

Cited by 4 publications

References 22 publications

Saturn’s thermal emission at 2.2-cm wavelength as imaged by the Cassini RADAR radiometer

Saturn’s thermal emission at 2.2-cm wavelength as imaged by the Cassini RADAR radiometer

Optimal measures for characterizing water-rich super-Earths

Analysis of Saturn’s thermal emission at 2.2-cm wavelength: Spatial distribution of ammonia vapor

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