Jupiter's Atmospheric Composition from the Cassini Thermal Infrared Spectroscopy Experiment

Kunde, V. G.; Flasar, F. M.; Jennings, Donald E.; Bézard, Bruno; Strobel, D. F.; Conrath, B. J.; Nixon, C. A.; Bjoraker, G. L.; Romani, P. N.; Achterberg, R. K.; Simon-Miller, A. A.; Irwin, Patrick; Brasunas, J. C.; Pearl, J. C.; Smith, M. D.; Orton, Glenn S.; Gierasch, P. J.; Spilker, L. J.; Carlson, R.; Mamoutkine, A. A.; Calcutt, S. B.; Read, P. L.; Taylor, F. W.; Fouchet, Thierry; Parrish, P.; Barucci, A.; Courtin, R.; Coustenis, A.; Gautier, D.; Lellouch, E.; Marten, A.; Prangé, Renée; Biraud, Y.; Ferrari, C.; Owen, Tobias; Abbas, M. M.; Samuelson, R. E.; Raulin, F.; Ade, Peter A. R.; Césarsky, C. J.; Grossman, K.; Coradini, A.

doi:10.1126/science.1100240

Cited by 64 publications

(67 citation statements)

References 33 publications

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“…Photochemical aerosols are observed in multiple regions of the atmospheres of both Jupiter and Saturn, along with intense hydrocarbon chemistry. Observations reveal the presence of hydrocarbons reaching up to the complexity of benzene (42,43), and particles become observable below the stratosphere, with a typical radius of 0.1 μm, which increases toward lower altitudes (3,44). Until recently, the aerosol was assumed to form from the homogeneous nucleation of low-mass aromatic compounds, such as anthracene and pyrene.…”

Section: Discussionmentioning

confidence: 99%

Aerosol growth in Titan’s ionosphere

Lavvas

Yelle

Koskinen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

140

134

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Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere.planetary sciences | heterogeneous chemistry | particles charging | plasma P hotochemical aerosols are observed in many atmospheres of our solar system (1-3), and their presence is also detected in exoplanet atmospheres (4). Apart from their direct influence on the atmospheric properties through their interaction with the radiation field, aerosols have further astrobiological implications; their presence in the early Earth's atmosphere could have protected the surface and any life evolving there from UV radiation (5), and laboratory studies of Titan aerosol analogs have identified an in vitro formation of amino acids during aerosol production (6). However, the general mechanisms involved in the production and growth of photochemical aerosols from atmospheric gases have remained elusive. Titan, as the most extreme example of an aerosol-dominated atmosphere, provides a unique opportunity to investigate these mechanisms.Cassini observations revealed the presence of aerosols in multiple regions of the atmosphere, from the troposphere (7), stratosphere (8), and mesosphere (9, 10) up to the thermosphere where the detection of large mass positive and particularly negative ions has been suggested to be the signature of aerosol formation (11)(12)(13)(14). During a recent flyby (T70), the Cassini spacecraft penetrated to deeper regions of Titan's thermosphere than usual, reaching altitudes close to 880 km that had not previously been sampled with in situ measurements. Measurements from the Langmuir probe (LP) during this unique flyby reveal a high abundance of negative ions at closest approach, comparable to the positive ion density, and a corresponding decrease in the electron density (15). This conclusion is supported by the analysis of multiple Cassini observations, which reveals that the observed electron density is smaller than the density anticipated from photochemical equilibrium, implying that the photochemical models are missing a significant electron loss mechanism (16, 17). Thus, current observations demonstrate a significant decrease of the electron density relative to the positive ion density in the lower ionosphere with a concurrent increase in the density of the negative ions.Aerosols, or dust particles in general, are known to interact with free electr...

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Section: Discussionmentioning

confidence: 99%

Aerosol growth in Titan’s ionosphere

Lavvas

Yelle

Koskinen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

140

134

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“…The analysis of biological spectral signatures on an exoplanet is thus optimised if its physical properties, such as its mass and radius, can be also determined. [102]) and the brown dwarf 2M0415 [103] are compared to a model spectrum of hot-Jupiter HD189733b [104]. Figure adapted from [103, 105].…”

Section: Biosignaturesmentioning

confidence: 99%

The physical properties of extra-solar planets

2009

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Abstract. Tremendous progress in the science of extrasolar planets has been achieved since the discovery of a Jupiter orbiting the nearby Sun-like star 51 Pegasi in 1995. Theoretical models have now reached enough maturity to predict the characteristic properties of these new worlds, mass, radius, atmospheric signatures, and can be confronted with available observations. We review our current knowledge of the physical properties of exoplanets, internal structure and composition, atmospheric signatures, including expected biosignatures for exo-Earth planets, evolution, and the impact of tidal interaction and stellar irradiation on these properties for the short-period planets. We discuss the most recent theoretical achievements in the field and the still pending questions. We critically analyse the different solutions suggested to explain abnormally large radii of a significant fraction of transiting exoplanets. Special attention is devoted to the recently discovered transiting objects in the overlapping mass range between massive planets and low-mass brown dwarfs, stressing the ambiguous nature of these bodies, and we discuss the possible observable diagnostics to identify these two distinct populations. We also review our present understanding of planet formation and critically examine the different suggested formation mechanisms. We expect the present review to provide the basic theoretical background to capture the essential of the physics of exoplanet formation, structure and evolution, and the related observable signatures.

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“…The recent detection of oxygen compounds that are unambiguously in the stratospheres of the giant planets (aside from the Comet Shoemaker-Levy 9 impact debris on Jupiter) indicates that external material from meteoritic dust, ring/satellite debris, and/or cometary impacts frequently enters giant-planet atmospheres (e.g., Feuchtgruber et al 1997Feuchtgruber et al , 1999Bergin et al 2000;Moses et al 2000b;Lellouch et al , 2006Kunde et al 2004;Flasar et al 2005a;Burgdorf et al 2006;Hesman et al 2007). The relative importance of each of these sources is not well understood and may differ from planet to planet.…”

Section: Giant Planetsmentioning

confidence: 99%

“…Observers have now mapped the meridional distribution of several stratospheric constituents on Jupiter and Saturn (e.g., Kunde et al 2004;Flasar et al 2005a;, Prangé et al 2006, Nixon et al 2007Howett et al 2007), and the observations indicate the need for coupled photochemistry-transport models (see Liang et al 2005;Lellouch et al 2006;Moses et al 2007). Another focus of current research is the extent to which auroral chemistry affects the stratospheric composition locally and perhaps even globally on Jupiter and Saturn (e.g., Wong et al , 2003Friedson et al 2002).…”

Section: Giant Planetsmentioning

confidence: 99%

Neutral Atmospheres

et al. 2008

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This paper summarizes the understanding of aeronomy of neutral atmospheres in the solar system, discussing most planets as well as Saturn's moon Titan and comets. The thermal structure and energy balance is compared, highlighting the principal reasons 192 I.C.F. Mueller-Wodarg et al. for discrepancies amongst the atmospheres, a combination of atmospheric composition, heliocentric distance and other external energy sources not common to all. The composition of atmospheres is discussed in terms of vertical structure, chemistry and evolution. The final section compares dynamics in the upper atmospheres of most planets and highlights the importance of vertical dynamical coupling as well as magnetospheric forcing in auroral regions, where present. It is shown that a first order understanding of neutral atmospheres has emerged over the past decades, thanks to the combined effects of spacecraft and Earth-based observations as well as advances in theoretical modeling capabilities. Key gaps in our understanding are highlighted which ultimately call for a more comprehensive programme of observation and laboratory measurements.

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Jupiter's Atmospheric Composition from the Cassini Thermal Infrared Spectroscopy Experiment

Cited by 64 publications

References 33 publications

Aerosol growth in Titan’s ionosphere

Aerosol growth in Titan’s ionosphere

The physical properties of extra-solar planets

Neutral Atmospheres

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