Geologic investigation of lobate scarps in the vicinity of Chandrayaan-3 landing site in the southern high latitudes of the moon

Abstract

The Chandrayaan-3 primary landing site (PLS) is located in the southern high latitude region between 68–70° S and 31–33° E of the Moon. We have found two scarps (scarp #1 and #2) in the surrounding area of PLS. Since lobate scarps are one of the youngest tectonic structures on the Moon and they are seismically active recently, we have conducted a detailed morphological and topographic investigation of the scarps to examine their origin. Subsequently, chronological and seismic investigation of the inferred lobate thrust fault scarps in the PLS region was carried out to assess the safety and the possible hazards to the lander/rover of the Chandrayaan-3 mission. Our analysis reveals that out of the two scarps located in the PLS region, scarp #2 is a typical lobate thrust fault scarp, which is generally comparable in vergence direction, maximum relief, and maximum slope on the scarp face to the scarps found elsewhere on the Moon. Scarp #1 could be potentially a non-fault related scarp. The crater size-frequency distribution (CSFD) based best-fit ages derived for the scarp face, and hanging and footwalls of the scarp reveal that the scarp is a younger generation scarp (∼20–30 Ma). We have found evidence of fresh and faded boulder-fall trails on the rims and walls of multiple craters located around the scarp #2. The seismic measurements reveal potential shallow moonquakes induced by the lobate scarp #2 could have generated a moonquake of a cumulative or maximum possible moment magnitude of Mw 6.3. Based on our analysis of the potential ground shaking caused by the shallow moonquake, it appears that the landing site is safe from seismic hazards. Nevertheless, we propose that the Instrument for Lunar Seismic Activity (ILSA) onboard the Chandrayaan-3 lander could possibly detect recent Mw 4 shallow moonquakes, provided that they occur currently at a focal depth of <1 km.