Since March 2015 NASA’s Dawn mission has been studying the structure and composition of Ceres, the largest object in the main asteroid belt. Results from the Visible and Infrared Mapping Spectrometer (VIR-MS) on Dawn have indicated water-rich minerals, namely NH4-bearing clays and Mg-rich serpentines, on the surface. Magnetite and Mg-rich carbonates are abundant (over 10%), whilst Fe-sulphides and organics are also likely present. This complex mineral assemblage is consistent with extensive aqueous alteration, and is comparable to that of the hydrated CM and CI carbonaceous chondrite meteorites. In these meteorites we find that progressive aqueous alteration results in increasingly Mg-rich phyllosilicates and carbonates. However, even the most altered CM and CI chondrites do not contain NH4-bearing clays, and their abundance of magnetite and carbonates are significantly lower (less than 5%).

The surface of Ceres records a degree of aqueous alteration not currently represented in the meteorite collection. It has been speculated that Ceres lost its original ice shell, and that the present day surface may represent a deeper region of the asteroid. Higher temperatures and/or greater fluid availability at increased depth within Ceres could have produced more extreme aqueous reactions. Alternatively, Ceres may have accreted from different materials to the CM/CI parent bodies, perhaps because it formed in the outer disk. We will discuss how studying hydrated meteorites and terrestrial analogues in the laboratory can help us constrain the history of Ceres and better understand the nature and distribution of volatiles in the solar system.