Mercury Radar Imaging: Evidence for Polar Ice

• DOI: 10.1126/science.258.5082.635
• Publication Date: 2006-10-05T23:03:06Z
• Authors: Martin A. Slade; Bryan J. Butler; Duane O. Muhleman
• Keywords: 550; 13. Climate action; 0103 physical sciences; 551; 01 natural sciences

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 (μ c ) was 1.0 to 1.4; values < ∼0.1 are typical for terrestrial planets. Such high values of μ c have hitherto been observed in radar observations only from icy regions of Mars and icy outer planet satellites.