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Chao Meng-Fu (crater)
Chao Meng-Fu is a 167 kilometer-diameter crater on Mercury named after the Chinese painter and calligrapher Zhao Mengfu (1254–1322). Due to its location near Mercury's south pole (132.4° west, 87.3° south) and the planet's small axial tilt, an estimated 40% of the crater lies in permanent shadow. This combined with bright radar echoes from the location of the crater leads scientists to suspect that it may shelter large quantities of ice protected against sublimation into the near-vacuum by the constant -171 °C temperatures.
==Radar evidence for ice==
Radar studies involving Arecibo (Puerto Rico), Goldstone (California, United States), and the Very Large Array (New Mexico, United States) detected a number of highly-radar-reflective depolarized areas on Mercury, including several locations at the planet's poles. Many of these reflective features appear to coincide with craters imaged by Mariner 10, with the largest feature at the south pole corresponding to Chao Meng-Fu crater.
The luminosity and depolarization of the radar reflections are much more characteristic of ice than of the silicate rocks making up Mercury's crust. Still, these reflections are too dim to be pure ice; it has been hypothesized that this is due to a thin or partial layer of powder over the underlying ice. However, with no direct confirmation, it is always possible that the observed radar reflectivity from Chao Meng-Fu and similar craters is due to depositions of metal-rich minerals and compounds. NASA's MESSENGER mission may provide additional evidence for or against the presence of ice when it begins orbiting Mercury in 2011.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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