Nature 374, 238 - 240 (16 March 2002); doi:10.1038/374238a0

Tidal effects of disconnected hydrocarbon seas on Titan

Stanley F. Dermott^* & Carl Sagan^†

^*Department of Astronomy, PO Box 112055, University of Florida, Gainesville, Florida 32611-2055, USA
^†Laboratory for Planetary Studies, Cornell University, Ithaca, New York 14853, USA

THERMODYNAMIC and photochemical arguments^1–4 suggest that Titan, the largest satellite of Saturn, has a deep ocean of liquid hydrocarbons. At visible wavelengths, Titan's surface is obscured by a thick stratospheric haze, but radar observations^5–7 have revealed large regions of high surface reflectivity that are inconsistent with a global hydrocarbon ocean. Titan's surface has also been imaged at infrared wavelengths^8–10, and the highest-resolution data (obtained by the Hubble Space Telescope) show clear variations in surface albedo and/or topography¹⁰. The natural interpretation of these observations is that Titan, like the Earth, has continents and oceans. But Titan's high orbital eccentricity poses a problem for this interpretation, as the effects of oceanic tidal friction would have circularized Titan's orbit for most configurations of oceans and continents^1,11. Here we argue that a more realistic topography, in which liquid hydrocarbons are confined to a number of disconnected seas or crater lakes, may satisfy both the dynamical and observational constraints.

References

1.	Sagan, C. & Dermott, S. F. Nature 300, 731−733 (1982). | Article | ISI |
2.	Flasar, F. M. Science 221, 55−57 (1983). | ISI |
3.	Lunine, J. I., Stevenson, D. J. & Yung, Y. K. Science 222, 1229−1230 (1983). | ISI | ChemPort |
4.	Lunine, J. I. Rev. Geophys. 31, 133−149 (1993). | Article | ISI |
5.	Muhleman, D. O., Grossman, A. W., Butler, B. J. & Slade, M. A. Science 248, 975−980 (1990). | ISI |
6.	Muhleman, D. O., Grossman, A. W., Slade, M. A. & Butler, B. J. (abstr.) Bull. Am. astr. Soc. 24, 954−955 (1992).
7.	Grossman, A. W. & Muhleman, D. O. (abstr.) Bull. Am. astr. Soc. 24, 954 (1992).
8.	Lemmon, M. T., Karkoschka, E. & Tomasko, M. Icarus 103, 329−332 (1993). | Article | ISI |
9.	Griffith, C. A. Nature 364, 511−514 (1993). | Article | ISI |
10.	Smith, P. H., Lemmon, M. T., Caldwell, J. J., Allison, M. D. & Sromovsky, L. A. (abstr.) Bull. Am. astr. Soc. 26, 1181 (1994).
11.	Sears, W. D. (abstr.) Bull. Am. astr. Soc. 26, 1184 (1994); Icarus (in the press).
12.	Lambeck, K. The Earth's Variable Rotation: Geophysical Causes and Consequences 295 (Cambridge Univ. Press, Cambridge, 1980).
13.	Webb, D. J. Contemp. Phys. 23, 419−442 (1982).
14.	Burns, J. A. in Satellites (eds Burns, J. A. & Matthews, M. S.) 117−158 (Univ. Arizona Press, Tucson, 1986).
15.	Dermott, S. F. Icarus 37, 310−321 (1979). | Article | ISI |
16.	Smith, B. A. et al. Science 212, 163−191 (1981). | ISI |
17.	Engel, S., Hartmann, W. K. & Lunine, J. I. (abstr.) Bull. Am. astr. Soc. 26, 1183 (1994).
18.	Merian, J. R. Über die Bewegung tropfbarer Flüssigkeiten in Gefässen (Basle, 1828).
19.	Turcotte, D. L. & Schubert, G. Geodynamics (Wiley, New York, 1982).
20.	Sagan, C. & Dermott, S. (abstr.) Bull. Am. astr. Soc. 26, 1183 (1994).
21.	Chapman, C. R. & McKinnon, W. B. in Satellites (eds Burns, J. A. & Matthews, M. S.) 492−580 (Univ. Arizona Press, Tucson, 1986).
22.	Peale, S. J., Cassen, P. & Reynolds, R. T. Icarus 43, 65−72 (1980). | Article | ISI |