Machine Cataloging of Lunar Craters from Digital Terrain Model

Introduction: An accurate and representative catalog of impact craters on the surface of the Moon is necessary to infer information about the age of surfaces and the sequence of geological events [1]. The existing global catalogs of lunar craters contain ~2700 craters [2] and ~8500 craters [3], respectively. They suffer from uneven areal coverage as they were compiled from images having different resolutions and solar illumination angles. Recently, the Lunar Orbiter Laser Altimeter (LOLA) [4], an instrument on board the Lunar Reconnaissance Orbiter (LRO) spacecraft, has acquired altimetry data which enable construction of global digital terrain model (DTM) with resolution of 64 pixels/degree. As the LOLA instrument will add new measurements even higher resolution DTM will be constructed. A DTM-based dataset is ideally suited for extraction of a global catalog of craters because it is spatially uniform and accurate. In fact, the first crater catalog of lunar crater based on the 64 pixels/degree DTM has already been constructed [5]; it contains 5185 manually identified craters with diameters ≥20 km. However, the 64 pixels/degree DTM contains many more small craters and forthcoming higher-resolution DTMs will contain even larger numbers of small craters. Catalogs incorporating smaller craters will allow finer spatial resolution of the stratigraphy. However, the only viable means to obtain such comprehensive catalogs is through automating the process of crater detection. This contribution reports on our campaign to construct global catalogs of lunar craters from LOLA-based DTM by means of automatic crater detection algorithm. The approach follows a similar effort to auto-detect craters on the surface of Mars [6] that resulted in a global catalog of 75,919 craters listing coordinates of each crater, its diameter and depth [7]. Based on our previous experience, we expect to catalog all craters with diameters ≥3 km from the 64 pixels/degree DTM. In addition to dating surfaces, the catalog will be used for construction of global depth-to-diameter ratio maps. Here we report on our approach to constructing the catalog and on preliminary results from a limited number of sites.