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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 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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Figure 1: A cylindrical projection map of Titan at 2-µm wavelength11.
Figure 2: The 2.1-µm brightness of four locations on the surface of Titan measured over four days as a function of solar zenith angle.
Figure 3: Synthesized images and plots of reflectivity.

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  1. Flasar, F. M. Oceans on Titan. Science 221, 55–57 (1983)

    Article  ADS  CAS  Google Scholar 

  2. Lunine, J. I., Stevenson, D. J. & Yung, Y. L. Ethane ocean on Titan. Science 222, 1229–1230 (1983)

    Article  ADS  CAS  Google Scholar 

  3. Yung, Y. L., Allen, M. & Pinto, J. P. Photochemistry of the atmosphere of Titan: Comparison between model and observations. Astrophys. J. Suppl. 55, 465–506 (1984)

    Article  ADS  CAS  Google Scholar 

  4. Campbell, D. B., Black, G. J., Carter, L. M. & Ostro, S. J. Radar evidence for liquid surfaces on Titan. Science 302, 431–434 (2003)

    Article  ADS  CAS  Google Scholar 

  5. Porco, C. C. et al. Imaging Titan from the Cassini Spacecraft. Nature 434, 159–168 (2005)

    Article  ADS  CAS  Google Scholar 

  6. Evans, K. F. & Stephens, G. L. A new polarized radiative transfer model. J. Quant. Spectrosc. Radiat. Trans. 46, 413–423 (1991)

    Article  ADS  CAS  Google Scholar 

  7. Deuze, J. L., Herman, M. & Santer, R. Fourier series expansion of the transfer equation in the atmosphere-ocean system. J. Quant. Spectrosc. Radiat. Trans. 41, 483–494 (1989)

    Article  ADS  Google Scholar 

  8. Brown, R. H. et al. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) investigation. Space Sci. Rev. 115, 111–168 (2004)

    Article  ADS  Google Scholar 

  9. West, R. A. & Smith, P. H. Evidence for aggregate particles in the atmospheres of Titan and Jupiter. Icarus 90, 330–333 (1991)

    Article  ADS  CAS  Google Scholar 

  10. Brown, M. E., Bouchez, A. H. & Griffith, C. A. Direct detection of variable tropospheric clouds near Titan's south pole. Nature 420, 795–797 (2002)

    Article  ADS  CAS  Google Scholar 

  11. Bouchez, A. H., Brown, M. E., Schaller, E. L. & Roe, H. G. Cloud frequency and wind speed in Titan's troposphere. Bull. Am. Astron. Soc. 36, 1696 (2004)

    Google Scholar 

  12. Wizinowich, P. et al. Performance of the W.M. Keck observatory natural guide star adaptive optic facility: the first year at the telescope. Proc. SPIE 4007, 2–13 (2000)

    Article  ADS  Google Scholar 

  13. Gibbard, S. G. et al. Titan's 2 µm surface albedo and haze optical depth in 1996–2004. Geophys. Res. Lett. 32, L17S02 (2004)

    Google Scholar 

  14. Lemmon, M. T. Properties of Titan's Haze and Surface. PhD thesis, Arizona Univ. (1994)

    Google Scholar 

  15. Grieger, B., Lemmon, M. T., Markiewicz, W. J. & Keller, H. U. Inverse radiation modeling of Titan's atmosphere to assimilate solar aureole imager data of the Huygens probe. Planet. Space Sci. 51, 147–158 (2003)

    Article  ADS  Google Scholar 

  16. Khare, B. N. et al. Optical constants of organic tholins produced in a simulated Titanian atmosphere—from soft-x-ray to microwave-frequencies. Icarus 60, 127–137 (1984)

    Article  ADS  CAS  Google Scholar 

  17. Martonchik, J. V. & Orton, G. S. Optical constants of liquid and solid methane. Appl. Opt. 33, 8306–8317 (1994)

    Article  ADS  CAS  Google Scholar 

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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.

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Correspondence to R. A. West.

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West, R., Brown, M., Salinas, S. et al. No oceans on Titan from the absence of a near-infrared specular reflection. Nature 436, 670–672 (2005).

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