Spatial Distribution and Thermal Diversity of Surface Volatile Cold Traps at the Lunar Poles

Abstract

The polar regions of the Moon host some of the most extreme low temperatures in the inner solar system due to its low obliquity, lack of atmosphere, and topographic relief. Some of these regions are already confirmed to host water ice. Proposed sources of water and other volatiles include lunar volcanic outgassing, solar wind, and comet impacts. Each of these possible sources would carry a potentially identifiable compositional signature beyond water. Determining the dominant sources of lunar volatiles, therefore, requires assessing the long-term thermal stability of an array of compounds. We present results of mapping the surface thermal stability locations of multiple key volatiles, including water, from the Diviner Lunar Radiometer data from 60° to 90° latitude in both hemispheres. We find the annual maximum temperature for each pixel of interest in the map (∼300 m) to determine which volatiles of interest would be stable there. We report on the thermal stability area of each volatile, as well as the geologic context in some cases. We find that while the thermal stability area for volatiles is larger in the south pole generally, both the north pole and south pole host areas where potential tracer volatiles from lunar volcanism, solar wind, and cometary impacts would be thermally stable for billions of years if such volatiles were ever delivered. We find several areas equatorward of ∼80° on the lunar nearside that could host water ice, where future missions could potentially access volatile deposits in order to place constraints on water delivery to the Moon.