Modeling aqueous alteration of CM carbonaceous chondrites

Results from an inorganic geochemical modeling study support a scenario in which low- temperature aqueous alteration of an anhydrous CM asteroidal parent body and melt water from H20 and CO;! ices produces the altered assemblage observed in CM carbonaceous chondrites (chrysotile, greenalite, tochilinite, cronstedtite and minor calcite and magnetite). We consider a range of possible precursor mineral assemblages, varying with respect to the Fe-oxidation state of the initial anhydrous phases. The aqueous solutions produced by this alteration are generally strongly basic and reducing and a large quantity of H2, and possible CH4, gas can be released during aqueous alteration.