Carbonaceous chondrites reveal mineralogical, chemical, and isotopic signs of aqueous alteration of reduced and anhydrous precursors, both inorganic and organic. The apparent net oxidation led to the formation of ferrous and ferric minerals, sulfates, phosphates, and specific organic compounds observed in chondrites. Some mineral transformations (e.g., cronstedtite to serpentine, magnetite to fayalite) indicate reduction. The redox processes on carbonaceous bodies imply actions of accreted oxidized volatiles such as water and C oxides and the generation of reduced byproducts (hydrogen, methane, etc.). During parent body alteration, the primary and secondary volatiles may separate into the gas phase, migrate and escape, affecting the pressure and redox processes throughout a body. We will quantify these processes based on observations in chondrites and physical-chemical modeling. In particular, we will evaluate (1) behavior of water in competitive redox and hydration/dehydration processes; (2) effects of amounts and types other accreted volatiles, both oxidized and reduced; (3) gas separation and pressure buildup within parent bodies. Modeling will be performed through calculations of partial and complete chemical equilibria in isobaric and isochoric rock-water-gas type systems. Kinetic models that include rates of mineral dissolution will be applied as well. The major attention will be devoted to processes on parent bodies of CM and CI carbonaceous chondrites. Our work will help to constrain formation of observed secondary minerals, alteration pathways in asteroids, chemical and isotopic patterns in chondrites, and the origin of volatiles accreted on parent bodies of carbonaceous chondrites.
|Effective start/end date||5/1/14 → 4/30/19|
- NASA: Goddard Space Flight Center: $285,544.00