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Science 23 October 1992:
Vol. 258. no. 5082, pp. 635 - 640
DOI: 10.1126/science.258.5082.635
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Articles

Mercury Radar Imaging: Evidence for Polar Ice

Martin A. Slade 1, Bryan J. Butler 2, and Duane O. Muhleman 2

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099
2 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125

The first unambiguous full-disk radar mapping of Mercury at 3.5-centimeter wavelength, with the Goldstone 70-meter antenna transmitting and 26 antennas of the Very Large Array receiving, has provided evidence for the presence of polar ice. The radar experiments, conducted on 8 and 23 August 1991, were designed to image the half of Mercury not photographed by Mariner 10. The orbital geometry allowed viewing beyond the north pole of Mercury; a highly reflective region was clearly visible on the north pole during both experiments. This polar region has areas in which the circular polarization ratio (pt) was 1.0 to 1.4; values <sim0.1 are typical for terrestrial planets. Such high values of have hitherto been observed in radar observations only from icy regions of Mars and icy outer planet satellites.

Submitted on June 3, 1992
Accepted on August 4, 1992


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