Lithification Mechanisms for Planetary Regoliths: The Glue that Binds

摘要

It is understood how rocks are made on Earth. However, on the Moon, Mercury, and, to a lesser extent, Mars and Venus, there are distinct rock-forming processes that we do not fully comprehend. The surfaces and crusts of the inner planetary bodies may retain a history of disruption by hypervelocity impact resulting in the generation of disaggregated materials to several kilometers depth. The uppermost component of this is called regolith (typically 20 m thick on the Moon), which is part of a more extensive megaregolith that is up to tens of kilometers thick, and which in places may pervade the entire crust of a planetary body. It is from these pulverized materials that new rocks are reaggregated to form so-called breccias. This work reviews regolith and megaregolith structure for the inner planetary bodies and investigates how extraterrestrial breccias are produced. Three principal formation mechanisms are explored: thermal sintering, shock sintering, and the dynamic interaction of impact-generated melt with fragmental material.