Ac-H-11 Sintana and Ac-H-12 Toharu quadrangles: Assessing the large and small scale heterogeneities of Ceres’ surface

Mineralogical maps of the Ac-H-11 Sintana and the Ac-H-12 Toharu quadrangles of the dwarf planet Ceres were produced in order to access the composition of this planetary body. We used data from NASA's Dawn spacecraft, in particular the spectra returned by VIR, the imaging spectrometer on board. Different spectral parameters in the infrared range have been computed to study the composition of this portion of Ceres’ surface and its large and small scale variability. We studied the variation and distribution of the phyllosilicate bands at 2.73 µm and 3.07 µm, the reflectance at 1.2 µm, and the overall spectrum in specific locations. We did not observe variations of the center of the bands at 2.73 µm and 3.07 µm, with the exception of a few pixels in the Kupalo crater. We found that this southern region, extending from 0° to 180° and from 21°S to 66°S, show an overall increase of phyllosilicate band intensity from the equatorial areas to the southern areas. Superimposed to the large-scale trend, we observe many smaller localized variations of band intensity. The observed variations can indicate large and small-scale heterogeneities in the abundance of the different species in the Ceres subsurface. However, the small-scale variation that is mostly associated with young craters, can be also due to processes related with impacts, such as de-hydration or delivery of exogenous material that, mixed with the original surface, could change the band intensity. Several craters, such as Kupalo and Juling, show a different composition with respect to the background, displaying water ice and sodium carbonates.