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Rain, winds and haze during the Huygens probe's descent to Titan's surface.

Authors
  • Tomasko, M G
  • Archinal, B
  • Becker, T
  • Bézard, B
  • Bushroe, M
  • Combes, M
  • Cook, D
  • Coustenis, A
  • de Bergh, C
  • Dafoe, L E
  • Doose, L
  • Douté, S
  • Eibl, A
  • Engel, S
  • Gliem, F
  • Grieger, B
  • Holso, K
  • Howington-Kraus, E
  • Karkoschka, E
  • Keller, H U
  • And 20 more
Type
Published Article
Journal
Nature
Publisher
Springer Nature
Publication Date
Dec 08, 2005
Volume
438
Issue
7069
Pages
765–778
Identifiers
PMID: 16319829
Source
Medline
License
Unknown

Abstract

The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent.

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