The Alphonsus region - A geologic and remote-sensing perspective

A number of interesting questions exist concerning the composition and origin of a number of geologic units in the west-central highlands crater Alphonsus. This paper utilizes a variety of newly obtained remote sensing data to address these questions and improve the current understanding of the geologic history of the Alphonsus region. Near-infrared and UV/VIS reflectance spectra were obtained and analyzed for many of the geologic features, the results of which are presented here. Spectra collected for pyroclastic debris associated with three endogenic dark halo crater complexes on the floor of Alphonsus indicate a basaltic assemblage rich in olivine. These pyroclastic deposits exhibit generally low returns on the depolarized 3.8 cm radar image. An exogenic dark halo crater was identified on the interior of Alphonsus and appears to be composed of a mixture of pyroclastic debris and highlands material. The light plains deposits and other highland units in the Alphonsus region generally exhibit a noritic compostion. However, the Alphonsus central peak is composed of pure anorthosite. This composition is unique within the region.