Sunday, October 16, 2011

Dark Ice on a Hot Planet

     Despite basking in the sun's fiery glow,  tiny Mercury, the innermost planet in our  solar system, is probably home to extensive  ice fields. Twenty years ago, radar obser-vations from Earth revealed small, highly  reflective areas close to Mercury's poles,  suggesting the presence of ice. Now, NASA's  MESSENGER spacecraft, which has orbited  Mercury since March, has confirmed that  these radar-bright patches coincide with  deep craters near the poles that never receive  sunlight. This color-coded photo mosaic  of Mercury's south polar region, presented  5 October at a joint meeting of the European  Planetary Science Congress and the Division for Planetary Sciences of the American  Astronomical Society, shows these 'freezer' areas as dark blotches. 
     According to MESSENGER instrument scientist Nancy  Chabot of the Johns Hopkins University's  Applied Physics Laboratory in Laurel, Mary-land, one-fifth of the region within 200 kilometers of Mercury's south pole is in permanent shadow. "It's all consistent with there being water ice," she says.



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