Refining Constraints on the Origin of Lunar Irregular Mare Patches via Mini-RF and DFSAR Data Analysis

Irregular mare patch (IMP) is one of the most enigmatic volcanic features in the lunar nearside maria. Their apparently fresh surface morphology and derived young model ages contradict the currently proposed thermal evolution history of the Moon. Lunar orbital synthetic aperture radar (SAR) data of Mini-RF onboard Lunar reconnaissance orbiter and dual-frequency SAR (DFSAR) flying on Chandrayaan-2 are analyzed in this article, to constrain the properties of IMPs within some depth from a radar perspective. The SAR datasets are first orthorectified and coregistered with the optical images, which allow for the interpretation of different terrains in small IMPs. Then, the polarimetric and scattering characteristics of different IMP-associated terrains are extracted and analyzed. Results show that the higher mounds in Ina, Sosigenes and Cauchy-5, as well as the lower uneven units in Ina and Sosigenes IMPs might be covered by a layer of rock-poor materials, which is similar to the surrounding maria regolith. This layer can be as thick as
$>$
0.6 m for the higher mounds and lower uneven units in Ina. Importantly, radar-bright IMPs are found, whose scattering characteristics are similar to these of the rocky units in Ina and the ejecta of degraded craters. Based on the radar characteristics of IMPs, their possible origins and evolution processes are discussed.