MINERALOGY OF RONGO QUANDRANGLE ON CERES

After more than one year orbit around Ceres, Dawn spacecraft covered large part of its surface, allowing for a global mineralogical mapping of the entire surface. For mapping purposes, likewise for Vesta, also Ceres’ surface has been divided in 15 quadrangles. Here we describe the quadrangle Ac-H-10 Rongo located in the equatorial region (288°-360°E, 22S-22N) of Ceres. VIR, the visible and infrared spectrometer onboard Dawn, acquired data at different spatial resolutions, allowing for identify the various mineralogical phases characteristic of Ceres surface, at global and local scale [1,2]. Ceres spectra present several bands in the spectral region between 2.5 and 4-µm. Spectral parameters retrieved by VIR data indicate a widespread distribution of NH₄-phillosilicates, and OH-rich clays [1]. Rongo quadrangle contains about five gelogical units [3], not always associated with mineralogical variations. The depth of the 3.1-µm band, due to the presence of NH₄–Phyllosicates, is quite homogeneous except for some localized regions in which this band appear shallower, and a similar trend is observed for the OH-singnature at 2.7-µm. The dominant feature of this quadrangle is Ahuna Mons, a unique case on Ceres [4]. Ahuna Mons is the largest mountain of the dwarf planet, and conversely to other geological units, shows a spectral parmeters variation with respect to other areas, linked to mineralogical differences.

[1] De Sanctis et al., 2015 Nature

[2] Ammannito et al., 2016 Science

[3] Platz et al., 2016, in preparation

[4] Ruesch et al., 2016, Science