The Distribution of Molecular Water in the Lunar South Polar Region Based upon 6 μm Spectroscopic Imaging

Abstract

The amount and distribution of water on the lunar surface are related to the input and production of water by solar wind and meteoroid bombardment, balanced by photodestruction and mobility across the surface. Using the Stratospheric Observatory for Infrared Astronomy (SOFIA), we imaged the 6.1 μ m feature that uniquely traces molecular water, covering 1/4 of the lunar nearside surface south of −60° latitude with 5 km resolution on 2022 February 17 UTC. The water feature strength varies significantly across the region, being drier at +28° longitude to more wet (170 ppm) at −7° longitude, and also decreasing toward the pole. Significant local enhancements are found, associated with south-facing, high-altitude topographic features. This includes relatively high H _2 O concentrations in a “wet ridge” just north of the Curtius crater; the south-facing, northern, inner rims of the most prominent craters; the south face of the central peak of the Moretus crater; and permanently shadowed polar regions.

Keywords

• Earth-moon system
• Lunar composition
• Lunar surface