Automated precision counting of very small craters at lunar landing sites

Abstract

Automated analysis of multiple LROC NAC images of the same area on the lunar surface, with each image exposed under different illumination conditions, can result in confident detection rates for craters as small as 3 m in diameter. The use of automatically generated templates improves the measurement accuracy of crater diameters and centre locations, relative to expertly counted benchmarks. By matching craters across multiple images, false positives can be eliminated and false negatives included. The requirement that all craters be matched in at least two images establishes a uniform detection threshold that enables different areas of the Moon to be compared quantitatively. Crater Size Frequency Distribution (CSFD) curves from a number of landing/impact sites on the nearside maria reveal significant differences in crater counts that require explanations in terms of different production and/or erosion rates. At some sites, crater populations can be rationalised in terms of just two distinct components, namely craters up to a few tens of metres in diameter formed within the last few hundred million years and an ancient component that has survived for billions of years. Some sites are more complex than this, their crater populations having been affected by secondary impacts.