Nature 436, 670-672 (4 August 2005) | doi:10.1038/nature03824; Received 10 February 2005; Accepted 18 May 2005

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

R. A. West1, M. E. Brown2, S. V. Salinas3, A. H. Bouchez4 & H. G. Roe2

  1. MS 169-237 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA
  2. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
  3. Centre for Remote Imaging, Sensing and Processing, National University of Singapore, Blk SOC 1, Level 2, Lower Kent Ridge Rd, Singapore 119260
  4. W. M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, Hawaii 96743, USA

Correspondence to: R. A. West1 Correspondence and requests for materials should be addressed to R.A.W. (Email: Robert.A.West@jpl.nasa.gov).

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 models1, 2, 3 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 sampled4. Here we present ground-based observations (at near-infrared wavelengths) and calculations showing that there is no evidence thus far for surface liquid5. 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.


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