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Science 5 May 2006:
Vol. 312. no. 5774, pp. 724 - 727
DOI: 10.1126/science.1123257
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Reports

The Sand Seas of Titan: Cassini RADAR Observations of Longitudinal Dunes

R. D. Lorenz,1* S. Wall,2 J. Radebaugh,1 G. Boubin,1 E. Reffet,1 M. Janssen,2 E. Stofan,3 R. Lopes,2 R. Kirk,4 C. Elachi,2,5 J. Lunine,1,2 K. Mitchell,2 F. Paganelli,2 L. Soderblom,4 C. Wood,6 L. Wye,7 H. Zebker,7 Y. Anderson,2 S. Ostro,2 M. Allison,8 R. Boehmer,2 P. Callahan,2 P. Encrenaz,9 G. G. Ori,10 G. Francescetti,11 Y. Gim,2 G. Hamilton,2 S. Hensley,2 W. Johnson,2 K. Kelleher,2 D. Muhleman,12 G. Picardi,13 F. Posa,14 L. Roth,2 R. Seu,13 S. Shaffer,2 B. Stiles,2 S. Vetrella,11 E. Flamini,15 R. West2

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show ~100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of ~0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

1 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
3 Proxemy Research, Bowie, MD 20715, USA.
4 U.S. Geological Survey, Flagstaff, AZ 86001, USA.
5 RADAR Team Leader, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
6 Planetary Science Institute, Tucson, AZ 85719, USA and Wheeling Jesuit College, Wheeling, WV 26003, USA.
7 Stanford University, Stanford, CA 94305, USA.
8 Goddard Institute for Space Studies, National Aeronautics and Space Administration, New York, NY 10025, USA.
9 Observatoire de Paris, 92195 Meudon, France.
10 International Research School of Planetary Sciences, Universita' d'Annunzio, 65127 Pescara, Italy.
11 Facoltá di Ingegneria, 80125 Naples, Italy.
12 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
13 Universitá La Sapienza, 00184 Rome, Italy.
14 Istituto Nazionale per la Fisica della Materia (INFM) and Dip. Interateneo di Fisica, Politecnico di Bari, 70126 Bari, Italy.
15 Agenzia Spaziale Italiana, 00131 Rome, Italy.

* To whom correspondence should be addressed. E-mail: rlorenz{at}lpl.arizona.edu

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