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Published August 4, 2005 | public
Journal Article

No oceans on Titan from the absence of a near-infrared specular reflection


With its substantial atmosphere of nitrogen, hydrocarbons and nitriles, Saturn's moon Titan is a unique planetary satellite. Photochemical processing of the gaseous constituents produces an extended haze that obscures the surface. Soon after the Voyager fly-bys in 1980 and 1981 photochemical models led to the conclusion that there should be enough liquid methane/ethane/nitrogen to cover the surface to a depth of several hundred metres. Recent Earth-based radar echoes imply that surface liquid may be present at a significant fraction of the locations sampled. Here we present ground-based observations (at near-infrared wavelengths) and calculations showing that there is no evidence thus far for surface liquid. Combined with the specular signatures from radar observations, we infer mechanisms that produce very flat solid surfaces, involving a substance that was liquid in the past but is not in liquid form at the locations we studied.

Additional Information

© 2005 Nature Publishing Group, a division of Macmillan Publishers Limited. Received 10 February; accepted 18 May 2005. We benefited from radiative transfer benchmark calculations provided by H. Gordon and from discussions with D. Campbell, R. Lorenz and S. Ostro. Part of this work was performed by the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. Author Contributions: M.E.B., A.H.B. and H.G.R. supplied the Keck observations and data analysis. S.V.S. provided the light-scattering model calculations.

Additional details

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October 19, 2023