GEOLOGICAL MAPPING AND MINERALOGICAL CHARACTERIZATION OF IMPACT MELT DEPOSITS AT LUNAR CRATER COPERNICUS: PEEKING INTO THE CRATERING PROCESS AND TARGET PROPERTIES

The morphological character, mineralogy and distribution of impact melt deposits hold important clues to understand various aspects of the cratering process. We are carrying out systematic geological mapping of impact melt deposits at young, complex craters on the Moon in an effort to identify scientifically useful trends. One of the key study locations in our effort is Copernicus crater (96 km diameter) on the nearside of the Moon. This geologically young, complex crater is well known for exhibiting lateral and vertical mineralogical heterogeneity in its target rocks. We are utilizing this mineralogical diversity to track the fate of impact melt after it was produced and study aspects such as melt mobility and mixing. In addition, we are also utilizing the morphological diversity of impact melt deposits, along with their distribution, to infer systematic trends.

Some of the interesting observations from this investigation include:

i) Systematic mineralogical trends on the crater floor. Clast-poor NW quadrant of the crater floor exhibits olivine and low Ca-pyroxene mineralogy. Clast-rich southern floor section mostly exhibits high Ca-pyroxene mineralogy.

ii) Potential influence of topography on melt morphology. The smooth NW quadrant also has the lowest elevation on the crater floor. The smooth (clast-poor) morphology of this melt unit could therefore be the result of melt drainage from topographically higher floor sections or it may be primary in nature.

iii) Wider areal coverage of the central uplift. Large coherent blocks, coated with impact melt, occur close to the central peaks and could be subdued sections of the central uplift.

Some of the observed trends at Copernicus have also been noted at other craters [1] indicating some systematics which could perhaps be utilized in interpreting the cratering process. These results from Copernicus would be presented and contrasted with observations from other mapped craters.

1. Dhingra D., James W. Head and Carle M. Pieters (2017) Geological mapping of impact melt deposits at lunar complex craters: New insights into morphological diversity, distribution and the cratering process, Icarus, DOI: 10.1016/j.icarus.2016.05.004