Also of note, LRO found bright spots not just on Shackleton's floor, an indication of highly reflective water ice, but also even brighter areas on the crater's walls, an unexpected and puzzling finding.
"We found that extremely interesting," Zuber said. "If the only explanation of what was in the crater was water ice then one would expect the ice to be concentrated in the coldest, darkest part of the crater, which would be the floor. So it suggests to us that there was some space weathering going on, with material sliding down the walls."
HOWSTUFFWORKS: Water on the Moon
One theory is that the moon may have periodic "moonquakes" from meteorite impacts or gravitational tugs by Earth which caused the crater walls to shake and shed their older material, revealing fresher, brighter soil.