October 27, 2010
Icy or Ice-Free?
LRO DTM image from NASA/ASU
The south pole of the Moon is where the black lines cross on the rim of Shackleton crater. In this high resolution digital topography image the entire 19 km wide crater is shown as if by X-rays. The walls are smooth because of downslope movement of debris but the flat floor includes some mounds and 8-10 small impact craters. By counting craters on deposits beyond Shackleton's rim Paul Spudis and colleagues estimated that the young looking crater was actually 3.6 billion years old. The craters on the floor of Shackleton suggest that any ice there has been heated and churned repeatedly. This may explain why the Kaguya team found no evidence for ice at the surface of the floor. Obviously the unique history of cratering within each polar crater may determine if comet-deposited ice is preserved. This might help explain why the recent LCROSS results did not include ice in some permanently shadowed crater floors.
Admission: I can't find where I got this image on the LRO website - sorry!
Rükl plate 73