2014 Annual Science Report
Arizona State University Reporting | SEP 2013 – DEC 2014
Task 3: Evaluate the Habitability of Europa's Subsurface Ocean
We developed models for oceanic composition on Europa and provided arguments for a sulfate-rich oceanic water chemistry.
Zolotov has developed new models for water-rock interactions aimed to evaluate Mg and S concentrations in putative Europa’s ocean. It was shown that Mg is abundant only in oxidized sulfate-rich oceanic water. In reduced water, the Mg concentration is less than 0.1 part per million and is controlled by low solubility of putative clay minerals at the oceanic floor. It was shown that sulfur species may not be abundant in a reduced sulfate-less ocean that interacts with mafic aor ultramafic rocks. Zolotov concludes that recent tentative detection Mg salts at the surface of Europa (Brown and Hand, 2013) is consistent with the sulfate-rich oceanic composition. A sulfate-bearing ocean agrees with a high abundance of S species in endogenic surface features. Sulfate-bearing oceanic water is consistent with sulfate-rich leaches from carbonaceous chondrites, which could be among the building blocks of Europa. Oceanic sulfates could have originated from oxidation of Fe sulfides by O2 and H2O2 formed through radiolysis of water ice. The oxidation could have occurred on CI/CM type chondritic planetesimals followed by leaching of sulfates from accreted rocks. Accretion of irradiated ices could have led to sulfate formation in the interior of Europa. Both scenarios imply formation on an ocean rich in Na, Cl, Mg, sulfate, and diverse C species.
Zolotov has investigated formation of magnesium hydroxide (brucite) and Mg-bearing carbonates observed the surface of the dwarf planet Ceres. The plausible scenario involves formation of these minerals in water and CO2-rich impact plumes, which implies an icy target and/or a carbonaceous impactor. If this scenario is correct, it also suggests formation of brucite and Mg carbonates on the surface of icy satellites such as Europa, Ganymede, and Callisto. These minerals may not be indicative of oceanic compositions and habitability of the moons.
PROJECT MEMBERS:Mikhail Zolotov