Analysis of boulders population around a young crater using very high resolution image of Orbiter High Resolution Camera (OHRC) on board Chandrayaan-2 mission

Abstract

The Orbiter High Resolution Camera (OHRC) is a very high spatial resolution panchromatic camera (0.45–0.70 μm) on-board Chandrayaan-2 orbiter. Its spatial resolution of 0.25 m from 100 km altitude is highest among all lunar orbiter missions. A simple crater with substantial boulder population was observed in an OHRC image of a region near Boguslawsky E crater. Boulders are distinctly seen in this image because of high spatial resolution of 0.28 m and low sun elevation angle (6°) which enhanced the boulders' shadows. We have identified and mapped >2000 boulders around this young un-named simple crater (74.9216° S, 54.5148° E). It is observed that the OHRC is capable of extending the lower limit of size for identifiable boulders below 1 m. The distributions of mapped boulders are studied and compared with previous studies. It was found that the coefficient values estimated by fitting power laws to various distributions, such as size-frequency, size-range, etc., are well within the ranges reported in literature for craters distributed on lunar surface around the landing sites. Weibull distribution was also fit to the data, and the fitting coefficients were compared with the values obtained in similar studies. The crater age was estimated to be in the range of 50‐90 Ma using empirical relations, and comparison with areal density of other craters near lunar landing sites. This study also provides a glimpse of the low-light imaging capability of the OHRC showing inside the shadow regions, which were illuminated by reflected light from adjoining areas.