The Rockiness of Lunar Tectonic Features

The uppermost lunar regolith is composed of fine-grained, porous material, where density and conductivity increase with depth along with the occurrence of larger rock fragments. Such regolith properties strongly affect the surface and subsurface temperatures. The Diviner Lunar Radiometer Experiment onboard the Lunar Reconnaissance Orbiter measures such surface temperatures and has been used to derive rock abundance. Rock abundance measurements are resultant by the fractional area of exposed rocks large enough (> 1 m) to be thermally isolated from the surrounding regolith. A key finding of using Diviner for regolith surface materials and temperature is that subtle differences among geologic features have been noted previously, but not studied in greater detail. The lunar surface has an array of varying tectonic features, such as wrinkle ridges, scarps, and rilles. Here we investigate how the rock abundance on localized scales vary across these tectonic features. We propose that rock abundance measurements can provide us insight to the tectonic evolution and morphology on a localized scale at these various geologic surface features. To evaluate this hypothesis, we used rock abundance data rendering on LROC QuickMap and Java Mission-planning and Analysis for Remote Sensing (JMARS). We observe that there are different levels of varying rock abundance across these tectonic features. For example, wrinkle ridges show higher rock abundances at the center, whereas rock abundances are highest at rille and graben walls and ends. We observed that the most variations of rock abundance were found at mare regions, especially at the connection between Mare Serenitatis and Mare Tranquillitatis (~ 18.5°, 26.3°). We suggest that these tectonic features should be categorized based on rock abundances and imply the variations of tectonic evolution from rock abundance measurements.