The Influence of Melt Trapping and Redox Condition on the Evolution of a Martian Magma Ocean and Protoatmosphere
Abstract
Immediately following metal-silicate segregation in Mars, the planet underwent a magma ocean (MO) phase. During crystallization of the magma ocean, volatiles such as CO2 and H2O played a crucial role by creating a greenhouse atmosphere and inhibiting radiative heat loss from the young planet. Two important aspects of the coupled evolution of these reservoirs involve the dynamics of melt trapping in the freezing front of the residual mantle and the oxidation state of the Martian interior during crystallization. In this work, we investigate the influence of both processes in the evolution of the martian MO. Our calculations indicate that for a given initial volatile abundance, the redox state of the mantle plays an extremely important role in controlling the time of crystallization of the MO and the volatile content of the residual Martian mantle.
Considering an initial Martian water content of 4.3-8.6 km GEL (Global Equivalent Layer) our models indicate that the Residual Mantle will contain 600-1200 ppm water. The amount of carbon trapped in the mantle, however, depends strongly on the redox condition of the Martian mantle. Under the most reducing conditions in this study, the residual mantle stored between 550-1000 ppm C as a mixture of solid carbon and trapped carbonate melt. The redox state of the Martian mantle also influences the time of crystallization of the magma ocean. Under a strongly reducing condition, the partial pressure of CO2 in the mantle is low as more carbon is stored in the mantle, leading to a reduced greenhouse effect and fast crystallization time.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P21A..07H
- Keywords:
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- 5210 Planetary atmospheres;
- clouds;
- and hazes;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6296 Extra-solar planets;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS