The LCROSS Impact Crater as Seen by ShadowCam and Mini‐RF: Size, Context, and Excavation of Copernican Volatiles.

The Lunar CRater Observations and Sensing Satellite (LCROSS) impacted a Centaur rocket stage into a permanently shadowed region (PSR) in Cabeus crater, excavating water ice and other volatiles. We used the Miniature Radio Frequency (Mini‐RF) instrument on the Lunar Reconnaissance Orbiter and the ShadowCam instrument on the Korean Pathfinder Lunar Orbiter to detect the probable 22‐m diameter crater that resulted from the LCROSS impact. The crater formed superposed upon a dense small crater population along a crater ray from a larger pre‐existing crater. From its geologic context, the ice and regolith excavated by LCROSS were likely modified within the last 0.1–0.5 Gyr. An upper limit for the excavated volatiles is ~0.9 Gyr, as the location was not a PSR prior to that time. A young age for the LCROSS‐detected volatiles supports the idea that they were mostly emplaced by an exogenic mechanism, such as from comets or the solar wind. Plain Language Summary: The LCROSS experiment formed an impact crater in an area of permanent shadow on the Moon, striking the surface at 2.5 km/s with a 2,300 kg spent rocket body on 9 October 2009. The impact ejecta from this cratering event included detectable amounts of water and other volatiles, which is perhaps the most direct evidence for significant water deposits on the Moon. However, since the impact location is in permanent shadow (no direct solar illumination), it proved hard to observe definitively the crater that LCROSS formed. Here, we use data from Mini‐RF, which illuminated the surface with S‐band radar, combined with ShadowCam, which acquires images within permanent shadows, to find the probable LCROSS impact crater. The impact crater is 22‐m in diameter, a bit smaller than was inferred indirectly after LCROSS. We also present new evidence that the volatiles in the ejecta likely got there in the last 20% of lunar history, which is important for understanding their origin and evolution. Key Points: We used Mini‐RF and ShadowCam to locate the 22‐m crater formed by LCROSS within a permanently shadowed region near the Moon's south poleGiven the crater's size, the regolith that was excavated, including volatiles, likely came from approximately the upper 2 mThe geologic context of the LCROSS crater suggests that the volatiles it excavated were relatively young, from the Copernican epoch [ABSTRACT FROM AUTHOR]