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.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Flasar, F. M. Oceans on Titan. Science 221, 55–57 (1983)
Lunine, J. I., Stevenson, D. J. & Yung, Y. L. Ethane ocean on Titan. Science 222, 1229–1230 (1983)
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)
Campbell, D. B., Black, G. J., Carter, L. M. & Ostro, S. J. Radar evidence for liquid surfaces on Titan. Science 302, 431–434 (2003)
Porco, C. C. et al. Imaging Titan from the Cassini Spacecraft. Nature 434, 159–168 (2005)
Evans, K. F. & Stephens, G. L. A new polarized radiative transfer model. J. Quant. Spectrosc. Radiat. Trans. 46, 413–423 (1991)
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)
Brown, R. H. et al. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) investigation. Space Sci. Rev. 115, 111–168 (2004)
West, R. A. & Smith, P. H. Evidence for aggregate particles in the atmospheres of Titan and Jupiter. Icarus 90, 330–333 (1991)
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)
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)
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)
Gibbard, S. G. et al. Titan's 2 µm surface albedo and haze optical depth in 1996–2004. Geophys. Res. Lett. 32, L17S02 (2004)
Lemmon, M. T. Properties of Titan's Haze and Surface. PhD thesis, Arizona Univ. (1994)
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)
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)
Martonchik, J. V. & Orton, G. S. Optical constants of liquid and solid methane. Appl. Opt. 33, 8306–8317 (1994)
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.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
About this article
Cite this article
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). https://doi.org/10.1038/nature03824
Experimental Astronomy (2012)
Space Science Reviews (2010)
Nature Geoscience (2008)
Space Science Reviews (2008)