Exogenic origin for the volatiles sampled by the Lunar CRater Observation and Sensing Satellite impact

TL;DR

This paper investigates the origin of volatiles in lunar PSRs, providing evidence that they are likely from cometary impacts rather than volcanic outgassing, which has implications for lunar history and volatile delivery.

Contribution

It demonstrates that the volatiles sampled by LCROSS are best explained by cometary impacts, ruling out volcanic outgassing as their source.

Findings

Volatiles are unlikely from volcanic outgassing.

Cometary impacts are the most plausible source.

Volatiles may be younger than 1 billion years.

Abstract

Returning humans to the Moon presents an unprecedented opportunity to determine the origin of volatiles stored in the permanently shaded regions (PSRs), which trace the history of lunar volcanic activity, solar wind surface chemistry, and volatile delivery to the Earth and Moon through impacts of comets, asteroids, and micrometeoroids. So far, the source of the volatiles sampled by the Lunar Crater Observation and Sensing Satellite (LCROSS) plume has remained undetermined. We show here that the source could not be volcanic outgassing and the composition is best explained by cometary impacts. Ruling out a volcanic source means that volatiles in the top 1-3 meters of the Cabeus PSR regolith may be younger than the latest volcanic outgassing event (~1 billion years ago; Gya).