Characterization of the LCROSS impact plume from a ground-based imaging detection

Abstract

The Lunar CRater Observation and Sensing Satellite (LCROSS) mission was designed to search for evidence of water in a permanently shadowed region near the lunar south pole. An instrumented Shepherding Spacecraft followed a kinetic impactor and provided -from a nadir perspective -the only images of the debris plume. With independent observations of the visible debris plume from a more oblique view, the angles and velocities of the ejecta from this unique cratering experiment are better constrained. Here we report the first visible observations of the LCROSS ejecta plume from Earth, thereby ascertaining the morphology of the plume to contain a minimum of two separate components, placing limits on ejecta velocities at multiple angles, and permitting an independent estimate of the illuminated ejecta mass. Our mass estimate implies that the lunar volatile inventory in the Cabeus permanently shadowed region includes a water concentration of 6.3 ± 1.6% by mass.

Properties of comet 9P/Tempel 1 dust immediately following excavation by deep impact

“…Laboratory impact experiments (e.g. Strycker et al, 2013;Schultz et al, 2007Schultz et al, , 2009Hermalyn et al, 2013) provide evidence that at early stages of the crater development, the ejecta plume can be filled and the ejecta cone becomes hollow later. This can especially be expected for oblique impacts, where a hydrodynamic explosion occurring almost immediately after impact lifts all the material above the impactor and initially fills the typical hollow cone created by expanding shockwave.…”

Characterization and Analysis of Near-Earth Objects via Lunar Impact Observations

“…Inspired by the success of Strycker et al (2013) in using Principal Component Analysis (PCA) to detect the lunar flash caused by the LCROSS spacecraft mission collision, PCA was investigated as a potential detection technique for lunar meteoroid impacts. The intent was to increase the sensitivity of detections beyond what impacts LunarScan could commonly find for a particular observation.…”

The effect of craters on the lunar neutron flux

“…If one ascribes the lack of an epithermal central count rate bump entirely to hydrogen in the PSR, then the factor of 0.35 in neutron count rate can be converted using the formula supplied by Lawrence et al [] into ∼4.5 wt% WEH. This is a factor of 4 greater than was inferred by Teodoro et al [] and consistent with the LCROSS results [ Colaprete et al , ; Strycker et al , ]. As Cabeus does not have a simple crater morphology and the possibility that additional compositional variation is being suggested by the thermal neutron profile, this value should be taken with a pinch of salt.…”

“…While statistically consistent with the LPNS result, the most probable value is over 5 times the LPNS‐inferred value. The reanalysis of the LCROSS data by Strycker et al [], which gave (6.3 ± 1.6)wt% WEH, is inconsistent with the LPNS result. These comparisons would be affected if the hydrogen detected by the LPNS was not uniformly spread across the surface within the large resolution element, which is approximately 1000 times as long as the crater produced by the LCROSS impact [ Schultz et al , ].…”