Radar Evidence for Liquid Surfaces on Titan

Science

Volumn 302, Issue 5644, 2003, Pages 431-434

  Campbell, Donald B ^a   Black, Gregory J ^b   Carter, Lynn M ^c   Ostro, Steven J ^d  

^a Department of Astronomy   (United States)

^b UNIVERSITY OF VIRGINIA   (United States)

^c Department of Obstetrics Gynecology   (United States)

^d CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

DIFFUSION; HYDROCARBONS;

LIQUID HYDROCARBONS;

RADAR SYSTEMS;

HYDROCARBON;

ARTICLE; ASTRONOMY; ATMOSPHERE; INFRARED SPECTROSCOPY; LIQUID; PRIORITY JOURNAL; SIGNAL NOISE RATIO; TELECOMMUNICATION;

ASTRONOMY; ATMOSPHERE; EXTRATERRESTRIAL ENVIRONMENT; HYDROCARBONS; ICE; RADAR; SATURN; WATER;

EID: 0142116243     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1088969     Document Type: Article

References (22)

1. D. O. Muhleman, A. W. Grossman, B. J. Butter, M. A. Slade, Science 248, 975 (1990).
2. J. J. Lunine, D. J. Stevenson, Y. L. Yung, Science 222, 1229 (1983).
3. P. H. Smith, M. T. Lemmon, R. D. Lorenz, L A. Sromovsky, J. J. Calwell, M. D. Allison, Icarus 119, 336 (1996).
4. S. G. Gibbard et al., Icarus 139, 189 (1999).
5. R. Meier, B. A. Smith, T. C. Owen, R. J. Terrile, Icarus 145, 462 (2000).
6. A. Coustenis, E. Lellouch, J. P. Maillard, C. P. McKay, Icarus 118, 87 (1995).
7. C. A. Griffith, T. Owen, T. R. Geballe, J. Rayner, P. Rannou, Science 300, 628 (2003).
8. D. B. Campbell, J. F. Chandler, S. J. Ostro, G. H. Pettengill, I. I. Shapiro, Icarus 34, 254 (1978).
9. S. J. Ostro et al.,J. Geophys. Res. 97, 18227 (1992).
10. C. A. Griffith, T. Owen, G. A. Miller, T. Geballe, Nature 395, 575 (1998).
11. The uniform spacing of the sixteen 2001 spectra allows the diffuse component to be partially deconvolved so that each resultant spectrum more closely represents the diffuse scattering from a limited range of longitudes. There is no change in the amplitude or shape of the specular echoes. When estimating the diffuse cross section of the bright region, this process compensates for its limited extent in longitude. Its limited extent in latitude was compensated for by assuming that the surface south of the bright region has the same scattering properties as the trailing hemisphere. The deconvolution has the effect of symmetrizing the diffuse spectra, making the detection of a weak specular echo in the fits much easier.
12. R. D. Lorenz, S. E. Shandera, Geophys. Res. Lett. 28, 215 (2001).
13. C. Sagan, S. F. Dermott, Nature 300, 731 (1982).
14. W. R. Thompson, S. W. Squyres, Icarus 86, 336 (1990).
15. 2, a good estimate of ε can be obtained from a measurement of the specular cross section.
16. -1/2 is the (undulating) surface RMS slope (21).
17. N. A.-L. Ghafoor, J. C. Zarnecki, P. C. Challenor, M. A. Srokosz, J. Geophys. Res. 105, 12077 (2000).
18. R. D. Lorenz, Icarus 136, 344 (1998).
19. S. Rodriguez et al., Icarus 164, 213 (2003).
20. J. V. Evans, T. Hagfors, Radar Astronomy (McGraw-Hill, New York, 1968), chap. 4.
21. T. Hagfors, J. Geophys, Res. 66, 3779 (1964).
22. We thank A. Hine, A. Crespo, R. French, J-L. Margot, M. Nolan, P. Nicholson, P. Perillat, and the staffs of the Arecibo and Green Bank telescopes. J. Chandler and J. Giorgini provided the Titan observing ephemeredes. Extensive comments by C. Griffith, one of which is paraphrased in the last paragraph, are appreciated. D.B.C., L.M.C., and S.J.O. acknowledge support by the Planetary Astronomy and Planetary Geology and Geophysics Programs of the National Aeronautics and Space Administration (NASA). Part of this research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation (NSF) and with support from NASA. The Green Bank Telescope is part of the National Radio Astronomy Observatory, a facility of the NSF operated under cooperative agreement by Associated Universities, Inc.