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Radar Reflectivity of Titan

Muhleman, Duane O. and Grossman, Arie W. and Butler, Bryan J. and Slade, Martin A. (1990) Radar Reflectivity of Titan. Science, 248 (4958). pp. 975-980. ISSN 0036-8075. doi:10.1126/science.248.4958.975.

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The present understanding of the atmosphere and surface conditions on Saturn's largest moon, Titan, including the stability of methane, and an application of thermodynamics leads to a strong prediction of liquid hydrocarbons in an ethane-methane mixture on the surface. Such a surface would have nearly unique microwave reflection properties due to the low dielectric constant. Attempts were made to obtain reflections at a wavelength of 3.5 centimeters by means of a 70-meter antenna in California as the transmitter and the Very Large Array in New Mexico as the receiving instrument. Statistically significant echoes were obtained that show Titan is not covered with a deep, global ocean of ethane, as previously thought. The experiment yielded radar cross sections normalized by the Titan disk of 0.38 ± 0.15, 0.78 ± 0.15, and 0.25 ± 0.15 on three consecutive nights during which the sub-Earth longitude on Titan moved 50 degrees. The result for the combined data for the entire experiment is 0.35 ± 0.08. The cross sections are very high, most consistent with those of the Galilean satellites; no evidence of the putative liquid ethane was seen in the reflection data. A global ocean as shallow as about 200 meters would have exhibited reflectivities smaller by an order of magnitude, and below the detection limit of the experiment. The measured emissivity at similar wavelengths of about 0.9 is somewhat inconsistent with the high reflectivity.

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Butler, Bryan J.0000-0002-5344-820X
Additional Information:© 1990 American Association for the Advancement of Science. This work was supported by NASA grant NAGW-1499 administered by J. Rahe and NSF grant AST 860111 administered by V. Pankonin. This is contribution number 4797 from the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125. We wish to thank the staff at the VLA and at JPL for their excellent performance during this complex experiment. We acknowledge several useful discussions with G. L. Berge and D. Stevenson, and we thank P. Goldreich and R. Goldstein for carefully reading the manuscript and for their suggestions. JPL is operated by California Institute of Technology under contract with the National Aeronautics and Space Administration.
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Caltech Division of Geological and Planetary Sciences4797
Issue or Number:4958
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Official Citation:Radar Reflectivity of Titan Duane O. Muhleman, Arie W. Grossman, Bryan J. Butler, and Martin A. Slade Science 25 May 1990: 248 (4958), 975-980. [DOI:10.1126/science.248.4958.975]
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56853
Deposited By: Tony Diaz
Deposited On:22 Apr 2015 16:47
Last Modified:10 Nov 2021 21:04

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