shoemaker

Shoemaker is a lunar crater that is located near the southern pole of the Moon, within a half crater diameter of Shackleton crater. It lies to the south of Malapert crater, and just to the west of the similar-sized Faustini crater. The rim of Shoemaker is circular and worn, with some small craters along the inner wall. Due to the lack of illumination, the albedo of the interior floor surface remains unknown.

Prior to being given its current name by the IAU, this formation had been informally named Mawson crater (after the Antarctic explorer Douglas Mawson). It was officially named Shoemaker in honor of the geologist whose remains were on board the Lunar Prospector spacecraft that impacted this crater floor.

Cold trap deposits

This crater became of interest to scientists when the Lunar Prospector detected unusually high concentrations of hydrogen on the floor of this and other nearby craters using a neutron spectrometer. The floor of this crater is kept in permanent shadow from the Sun, and thus maintains a temperature below 100 kelvins. Thus the floor forms a cold trap, and any molecules of water that wander into the crater from cometary impacts can deposit on the floor and remain here almost permanently. The instruments on board the Prospector gave a concentration of about 146 ppm of hydrogen, compared to 50 ppm for the average lunar surface.

The topography of this crater was subsequently measured using the Goldstone 70-meter antenna to irradiate it with 3.5 cm radar. Two 34-meter antennas, located 20 kilometers apart, received the echoes, and the results were used to generate a coarse topographic map.

On July 31, 1999, the Prospector was deliberately crashed into the floor of this crater to determine if a plume of water vapor would be detected. The apparent detection of water and the shallow rim of this crater made it a suitable target for this experiment. However the outcome was unsuccessful. Subsequent tests have failed to confirm the presence of water in the crater floor, so the hydrogen found in the crater bottom is likely to prove more difficult to extract than had been originally hoped.

References

• "Arecibo radar shows no evidence of thick ice at lunar poles, despite data from previous spacecraft probes, researchers say", Cornell University News, November 12, 2003. Retrieved on 2007-08-08. 
• "No Water Ice Detected From Lunar Prospector Impact", Science Daily, October 14, 1999. Retrieved on 2007-08-08. 

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