Analyzing Lunar Polar Water Ice Using Available Datasets

Abstract:

The small tilt (1.5°) of the Moon results in a very low sun angle at the lunar poles. Inside polar craters there are Permanently Shadowed Regions (PSRs) that receive no direct sunlight and have temperatures down to 25 K. These PSRs act as cold traps for volatiles, and economically viable quantities of water-ice are believed to exist at both the north and south poles. Characterizing locations within PSRs that have a high probability of containing water ice encourages future science- and prospecting-based exploration.

We utilized previously generated temperature, altimetry, UV, IR, radio, and neutron spectrometry datasets to search for signatures which can be interpreted as water ice in 4 PSRs: Faustini, Haworth, Shoemaker, and Sverdrup. After all signatures were compiled and correlated, each dataset was made into a weighted variable based upon the confidence that the location contains an ice signature and is accessible by state-of-the-art landers. We modeled locations indicating the highest degree of confidence amongst all datasets.

Our work determined that the cold trap PSR inside Sverdrup crater at the lunar south pole was the most easily accessible location with the greatest chance of water ice at the surface. If water ice exists up to 1.5 m below the surface, then the amount of water ice contained within a 100 m landing ellipse could be ~ 42,000 metric tons. Our current study of the subsurface extent of water ice signatures will greatly constrain the volume of ice present at this and other locations. Ultimately, a ground-truth mission should be sent to locations determined by these or similar methods to obtain proof of water ice inside the lunar PSRs.