An in-depth look at the lunar crater Copernicus: Exposed mineralogy by high-resolution near-infrared spectroscopy

Roberto Bugiolacchi, Urs Mall, Megha Bhatt, Susan McKenna-Lawlor, Marek Banaszkiewicz, Kjell Brønstad, Andreas Nathues, Finn Søraas, KjetilUllaland and Rolf B. Pedersen

Icarus, Volume 213, Issue 1, May 2011, Pages 43-63


DOI: dx.doi.org/10.1016/j.icarus.2011.02.023

Abstract

Newly acquired, sequentially spaced, high-resolution near-infrared spectra across the central section of crater Copernicusí interior have been analyzed using a range of complementary techniques and indexes. We have developed a new interpretative method based on a multiple stage normalization process that appears to both confirm and expand on previous mineralogical estimations and mapping. In broad terms, the interpreted distribution of the principle mafic species suggests an overall composition of surface materials dominated by calcium-poor pyroxenes and minor olivine but with notable exceptions: the southern rim displays strong ca-rich pyroxene absorption features and five other locations, the uppermost northern crater wall, opposite rim sections facing the crater floor, and the central peak Pk1 and at the foot of Pk3, show instead strong olivine signatures. We also propose impact glass an alternative interpretation to the source of the weak but widespread olivine-like spectral signature found in low-reflectance samples, since it probably represents a major regolith constituent and component in large craters such as Copernicus. The high quality and performance of the SIR-2 data allows for the detection of diagnostic key mineral species even when investigating spectral samples with very subdued absorption features, confirming the intrinsic high-quality value of the returned data.