Water ice exists in large quantities in many small craters near the Moon's north pole, according to a new study. Spudis et al. present initial results from the miniature synthetic aperture radar (Mini-SAR) experiment on board India's Chandrayaan 1 spacecraft, which mapped most of the area near the north pole of the Moon between February and April 2009. The Mini-SAR instrument collected data on the polarization of radio waves reflected off the lunar surface. These data give the researchers insight into lunar surface features. For instance, high values of the circular polarization ratio (CPR) indicate either surface roughness or ice.