Titan solar occultation observed by Cassini/VIMS: Gas absorption and constraints on aerosol composition

Bellucci, Aurélie; Sicardy, B.; Drossart, P.; Rannou, P.; Nicholson, P. D.; Hedman, M. M.; Baines, K. H.; Burrati, B.

doi:10.1016/j.icarus.2008.12.024

Cited by 81 publications

(131 citation statements)

References 40 publications

(37 reference statements)

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“…We used the HITRAN2008 database for the CO 2 and CO linelists. An unidentified feature near 4.3 μm was previously reported (Bellucci et al 2009). We found that most of that feature can be attributed to the ν 3 +ν 6 band of C 2 H 6 (Brown, 2012, priv.…”

Section: Radiative Transfer Modelingsupporting

confidence: 60%

“…Although linelists for the 1−2 μm bands of CH 4 have been included in HITRAN and have been used for the analysis of Titan spectra (Bellucci 2008;Bailey et al 2011), significant discrepancies may remain between these linelists and laboratory data Karkoschka & Tomasko 2010). The lack of information on CH 4 weak lines in HITRAN severely limits the derivation of haze opacities from the VIMS spectra.…”

Section: Radiative Transfer Modelingmentioning

confidence: 99%

“…The Cassini/Visual Infrared Mapping Spectrometer (VIMS; Brown et al 2004) generated 63 spectra with unprecedented vertical resolution from 49 to 987 km in the 1−5 μm range by observing the Sun through the atmosphere of Titan on January 15, 2006 (Bellucci et al 2008;Bellucci et al 2009). These data provide a unique opportunity of infering the haze spectral properties because there is no contribution from the surface.…”

Section: Introductionmentioning

confidence: 99%

“…These data provide a unique opportunity of infering the haze spectral properties because there is no contribution from the surface. These VIMS data were first analyzed (Bellucci et al 2008;Bellucci et al 2009) in limited spectral intervals by constructing model spectra including CH 4 and CO lines and assuming that any residual absorption was due to the haze. Analyzing the whole 1−5 μm range is difficult because it requires accurate information on the numerous ro-vibrational lines of the various molecules present in the Titan atmosphere, information that is far from complete, especially at shorter wavelengths.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed descriptions of the Cassini/VIMS observations and data reduction were previously given elsewhere (Bellucci 2008;Bellucci et al 2009). In Fig.…”

Section: Introductionmentioning

confidence: 99%

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Spectral characteristics of the Titanian haze at 1−5 micron fromCassini/VIMS solar occultation data

Kim

Courtin

2013

A&A

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We retrieved optical-depth spectra of the Titanian haze in the range 1−5 μm from solar occultation data obtained by the Cassini/Visual Infrared Mapping Spectrometer (VIMS) at altitudes of 59−502 km. Only limited wavelength intervals within this spectral range have been analyzed before. The haze spectra we retrieved are mostly similar to those of alkane particles (or powders), with three major absorption peaks typical of alkane powders at 2.3, 3.4, and 4.3 μm. This result suggests that at least in the ∼60−500 km altitude range, the Titanian haze is mostly composed of alkane particles, possibly with some trace impurities. The absence of the 3.0 and 4.6 μm features excludes the molecules containing NH and CN bonds that are typical of laboratory-made tholins reported in the literature. The alkane-like spectral characteristics of the haze we observed at ∼60−500 km differ from previous results obtained at different or overlapping altitudes: a) the presence of aromatic compounds derived from solar-pumped emissions observed at high altitude (600−1250 km) by Cassini/VIMS near 3.3 μm; and b) the detection of HCN and NH 3 in the cores of haze particles collected at low altitude (20−130 km) by the Huygens/Aerosol Collector and Pyrolyser (ACP). We suggest that these different characteristics arise from different structural layers formed by coagulation/coalescence during particle sedimentation.

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Section: Radiative Transfer Modelingsupporting

confidence: 60%

Section: Radiative Transfer Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Detailed descriptions of the Cassini/VIMS observations and data reduction were previously given elsewhere (Bellucci 2008;Bellucci et al 2009). In Fig.…”

Section: Introductionmentioning

confidence: 99%

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Spectral characteristics of the Titanian haze at 1−5 micron fromCassini/VIMS solar occultation data

Kim

Courtin

2013

A&A

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Titan's atmosphere and climate

2017

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Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface‐atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen‐bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini‐Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth‐based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini‐Huygens comes to an end.

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An unidentified emission in Titan's upper atmosphere

Dinelli

López‐Puertas

Adriani

et al. 2013

Geophysical Research Letters

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[1] We have analyzed limb daytime observations of Titan's upper atmosphere at 3.3 m, acquired by the visual-infrared mapping spectrometer (VIMS) on Cassini. They were previously studied by García-Comas et al. (2011) to derive CH 4 densities. Here, we report an unidentified emission peaking around 3.28 m, hidden under the methane R branch. This emission is very strong, with intensity comparable to the CH 4 bands located in the same spectral region. It presents a maximum at about 950 km and extends from 600 km up to 1250 km. It is definitely pumped by solar radiation since it vanishes at night. Our analysis shows that neither methane nor the major hydrocarbon compounds already discovered in Titan's upper atmosphere are responsible for it. We have discarded many other potential candidates and suggest that the unidentified emission might be caused by aromatic compounds. Citation:

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Titan solar occultation observed by Cassini/VIMS: Gas absorption and constraints on aerosol composition

Cited by 81 publications

References 40 publications

Spectral characteristics of the Titanian haze at 1−5 micron fromCassini/VIMS solar occultation data

Spectral characteristics of the Titanian haze at 1−5 micron fromCassini/VIMS solar occultation data

Titan's atmosphere and climate

An unidentified emission in Titan's upper atmosphere

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