Fluxes of Fast and Epithermal Neutrons from Lunar Prospector: Evidence for Water Ice at the Lunar Poles

TLDR

Maps of epithermal‑ and fast‑neutron fluxes measured by Lunar Prospector were used to search for hydrogen‑enriched deposits at both lunar poles. Depressions in epithermal fluxes were observed near permanently shaded areas at both poles, with the North Pole showing a 4.6 % drop and the South Pole a 3.0 % drop relative to low‑latitude averages, while fast‑neutron fluxes showed no depression, supporting the presence of water ice covered by up to 40 cm of desiccated regolith.

Abstract

Maps of epithermal- and fast-neutron fluxes measured by Lunar Prospector were used to search for deposits enriched in hydrogen at both lunar poles. Depressions in epithermal fluxes were observed close to permanently shaded areas at both poles. The peak depression at the North Pole is 4.6 percent below the average epithermal flux intensity at lower latitudes, and that at the South Pole is 3.0 percent below the low-latitude average. No measurable depression in fast neutrons is seen at either pole. These data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles.