Detection and mapping of hydrocarbon deposits on Titan

Roger N. Clark, John M. Curchin, Jason W. Barnes, Ralf Jaumann, Larry Soderblom, Dale P. Cruikshank, Robert H. Brown, Sébastien Rodriguez, Jonathan Lunine, Katrin Stephan, Todd M. Hoefen, Stéphane Le Mouélic, Christophe Sotin, Kevin H. Baines, Bonnie J. Buratti, Philip D. Nicholson

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Abstract

We report the identification of compounds on Titan's surface by spatially resolved imaging spectroscopy methods through Titan's atmosphere, and set upper limits to other organic compounds. We present evidence for surface deposits of solid benzene (C6H6), solid and/or liquid ethane (C 2H6), or methane (CH4), and clouds of hydrogen cyanide (HCN) aerosols using diagnostic spectral features in data from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). Cyanoacetylene (2-propynenitrile, IUPAC nomenclature, HC3N) is indicated in spectra of some bright regions, but the spectral resolution of VIMS is insufficient to make a unique identification although it is a closer match to the feature previously attributed to CO2. We identify benzene, an aromatic hydrocarbon, in larger abundances than expected by some models. Acetylene (C2H2), expected to be more abundant on Titan according to some models than benzene, is not detected. Solid acetonitrile (CH 3CN) or other nitriles might be candidates for matching other spectral features in some Titan spectra. An as yet unidentified absorption at 5.01-μm indicates that yet another compound exists on Titan's surface. We place upper limits for liquid methane and ethane in some locations on Titan and find local areas consistent with millimeter path lengths. Except for potential lakes in the southern and northern polar regions, most of Titan appears "dry." Finally, we find there is little evidence for exposed water ice on the surface. Water ice, if present, must be covered with organic compounds to the depth probed by 1-5-μm photons: a few millimeters to centimeters.

Original languageEnglish (US)
Article numberE10005
JournalJournal of Geophysical Research E: Planets
Volume115
Issue number10
DOIs
StatePublished - Nov 1 2010

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ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Clark, R. N., Curchin, J. M., Barnes, J. W., Jaumann, R., Soderblom, L., Cruikshank, D. P., Brown, R. H., Rodriguez, S., Lunine, J., Stephan, K., Hoefen, T. M., Le Mouélic, S., Sotin, C., Baines, K. H., Buratti, B. J., & Nicholson, P. D. (2010). Detection and mapping of hydrocarbon deposits on Titan. Journal of Geophysical Research E: Planets, 115(10), [E10005]. https://doi.org/10.1029/2009JE003369