Abstract
The Huygens Probe returned the first in situ data on Titan's surface composition in January 2005. Although Huygens landed on a dry plain, the Gas Chromatograph Mass Spectrometer (GCMS) showed evidence of methane moisture in the near subsurface suggesting methane precipitation at some time in the past. Heavier organic molecules were not found to be abundant in the atmosphere or at the surface, but the GCMS surface results did show ethane to be present and tentatively identified cyanogen, benzene, and carbon dioxide. During descent, aerosol particles were processed with the Aerosol Collector and Pyroliser; results suggested that the aerosols contain both nitrites and hydrocarbons. The Descent Imager/Spectral Radiometer (DISR also carried by the probe) measured the visible and near-infrared spectral reflectance of the dark plain surface at the landing site. Those data suggest a mixture of water ice, tholin-like materials, and dark neutral material with a blue slope in the near infrared; identification of water ice is suggested but inconclusive. Most remarkably DISR did not detect spectral features, beyond those for methane, for a wide range of spectrally active hydrocarbon and nitrile compounds that had been expected to be present on the surface.