Mikhail Zolotov:Research results

 

Ceres

 

Ceres physical properties (shape and density) could be explained by organic-rich interior composition with 20-30 vol% of high molecular weight organic matter.

 

         Bright spots on Ceresí surface could have formed through post-impact hydrothermal activity. In particular, carbonates detected in Occator crater suggest a rapid isochemical emplacement by post-impact plumes. Salts could have deposited in ice grains from plumes and accumulated at the boiling depth. Other bright materials are excavated plume and subsurface salt deposits.

 

         Hydrated and ammonium salts are unstable at the surface in Occator.

 

         Recent Dawn images of the dwarf planet Ceres indicate a vivid topography, large and deep impact craters without fluidized outflows. These features are consistent with a rocky and undifferentiated internal structure without water mantle. The undifferentiated structure of Ceres was predicted in 2009.That paper demonstrated that Ceres could be a porous rocky body with mineral grain density similar to that of carbonaceous chondrites.

 

         The unusual carbonate-bearing surface mineralogy of the dwarf planet Ceres could have formed by impacts of ice-bearing surface materials. The results were published in Icarus (2014) pdf. Dawn images are consistent with impact-induced chemical processes leading to formation of low-albedo surface materials such as salts (carbonates, chlorides, etc.).

Mars

Our models for chemical weathering reproduce clay-bearing Noachian stratigraphies. Models show that acid sulfate weathering is more likely than weathering at a dense CO2 atmosphere. Geochemical models indicate the formation of martian clays together with sulfate and chloride salts during the Noachian epoch. We argue that massive sulfate deposits on Mars formed in the Hesperian epoch could be remobilized Noachian salts.

Equilibrium thermodynamics and kinetic models are used to conclude that silica rich deposits on Mars (e.g., in Gusev crater) could have formed through low-temperature weathering in acid springs. pdf

Kinetic models of mineral dissolution demonstrate that preferential dissolution of pyroxene in acid fluids may explain data obtained from Mars orbiters and Mars Exploration Rovers. pdf

Coupled thermodynamic/kinetic modeling of aqueous weathering shows that Martian surface could have been affected by short-term acid rainfalls caused by strong meteoritic impacts. A presence of silica and a deficiency of pyroxene observed in some low-albedo regions imply low-pH weathering without neutralization.

Carbonaceous chondrites and early asteroids

It is shown that neither elevated temperature nor H2 escape are needed to form sulfates on parent bodies of carbonaceous chondrites. Sulfates could have formed through aqueous parent body interaction of sulfides with products of ice radiolysis (O2, H2O2) in the solar nebula (pdf-2013; LPSC-2016-abstract-1778).

Models for water-rock interactions in CR chondrites demonstrate chemically contrast alteration microenvironments in matrices, around Fe-Ni metal grains, and at matrix-metal interfaces. pdf

Numerical models are used to evaluate the composition of aqueous fluids formed through interaction of water with CI-type carbonaceous chondritic materials on solar system bodies. pdf

 

Enceladus

Thermodynamic models for water-chondrite interaction show that cooling of strongly SiO2-undestaurated chondritic fluids to ~0 oC may not cause precipitation of silica. These results question the ideas about formation of nano-phase particles in the Saturnís system through cooling of hydrothermal fluids on Enceladus. The results were presented at the 46th Lunar and Planetary Science Conference(2014) pdf

Sodium chloride and sodium bicarbonate salts predicted in the interior of Saturnís moon Enceladus are detected in E ring of Saturn with Cassini. This discovery indicates past or present aqueous processes on Enceladus. Equilibrium thermodynamics and mass balance constraints were used to evaluate oceanic composition on early and today's Enceladus.

 

Mercury

The extremely low oxidation state of S-rich magma on Mercury is evaluated with use of metallurgical and petrological data. pdf

It is shown that pyroclastic explosions on Mercury could be driven by oxidation of magma in crustal magma chambers. Volcanic gases on Mercury could be rich in N2. The high S content detected with MESSENGER in Mercuryís surface materials is consistent with our predictions and models.