Mineralogical mapping of the Kerwan quadrangle on Ceres

Abstract

The Ceres surface is globally composed of Mg-phyllosilicates, ammoniated clays, carbonates and dark components. To obtain a more detailed mineralogical and geological investigation, the dwarf planet surface has been divided into fifteen quadrangles. The aim of this work is to investigate the abundance of phyllosilicates and ammoniated clays in the Kerwan quadrangle, classified as Ac-H-7 and spanning from 22°S to 22°N in latitude and from 72°E to 144°E in longitude. Maps of band depth distribution at 2.7 µm and 3.1 µm have been performed and compared with a map of geometric albedo estimated at 1.2 µm. Phyllosilicates and ammoniated clays generally correlate in the Kerwan quadrangle, even if departure from this behavior is observed in the floor of Kerwan, Inamahari and Homsuk craters. The greatest abundance of ammoniated phyllosilicates is found in Rao and Kerwan ejecta, while Bonsu and Tafakula floors are the most depleted in volatile, as well as Inamahari and Dantu ejecta. Six bright spots are detected in the Kerwan quadrangle, and the one richest in carbonate is related to Dantu ejecta in the southeast region. Some younger features (such as Rao or Kerwan ejecta) show deeper band depths than older terrain, a contrast trend with respect to the entire Ceres surface. Since this correlation is observed in a few other places on other quadrangles but not on the entire Ceres surface, it is possible that recent impact events could have been masked this correlation.