DEPTH PENETRATION OF AGGLUTINATES IN THE LUNAR REGOLITH

Agglutinate deposition in the lunar regolith may be a model for determining micrometeorite depth penetration by progenitor meteoroids of < 2 mm. Regolith of 1 m depth has been proposed for future lunar habitat shielding from meteorites based on modeling of flux data (Lindsey, 2003). Agglutinate deposits from lunar core sample data acquired at the six Apollo landing sites are measured for ascertaining maximum depth penetration by micrometeorites into the lunar surface. These core samples were taken from three geological provinces of maria, highlands, and transitional and are thus representative of the lunar near-side surface. By measuring the depositional regime of agglutinates, small intact impact glass from micrometeorites from the lunar core samples, an assessment may be made for penetration capacity by unaltered agglutinates versus burial of partial remnants. While the sampling locations are too small to run meaningful statistics, some important results were determined. The mature soils of fully-formed agglutinates ranges from depths of 12.5 – 25 cm. No intact agglutinates exceeded a 30 cm depth profile. No mature or remnant agglutinate layer exceeded 50 cm, and, in several occurrences, there were multiple stratigraphic layers of mature/sub-mature/immature soils before 1 m depth was reached. In addition, a 2013 meteorite impact on the moon exhumed an 18-meter diameter crater and was observed by both a ground-based team (Suggs et. al., 2014) and in lunar orbit by the Lunar Reconnaissance Orbiter (Robinson et. al., 2015). This impactor created a radially uneven ejecta blanket of regolith debris extending up to 30 km from the new crater. Those secondaries from the ejecta based on orbital measurements didn’t achieve a crater depth greater than 1 m. Through empirical evidence and correlation, a 1 m depth of lunar regolith is more than adequate as future habitat protection against micrometeorites and ejecta debris of < 2 mm that continually impact the lunar surface.