Kavli Affiliate: Laura Schaefer
| First 5 Authors: Kaveh Pahlevan, Laura Schaefer, Don Porcelli, ,
| Summary:
The Martian isotopic record displays a dichotomy in volatile compositions.
Interior volatiles from the mantle record a chondritic heritage (e.g., H, N,
Kr, Xe) whereas the atmospheric reservoir of Kr and Xe – which do not currently
experience escape – record heritage from a solar-like source. Motivated by
disparate inferences on the source of Martian atmospheric volatiles (outgassed
versus nebular captured), we consider hybrid-source accretionary atmospheres in
which a high molecular weight (e.g., CO2-rich) outgassed component is mixed in
with the low molecular weight H2-rich nebular atmosphere. We conduct
calculations of nebular capture with and without a high molecular weight
outgassed component mixed into the atmosphere during the lifetime of the solar
nebula. Mixing an outgassed component into the nebular layer enhances the
captured gas inventory by 1-3 orders of magnitude – depending on the outgassed
inventory – relative to "pure" nebular capture. These observations and
calculations suggest that the Martian atmosphere arose as a subequal mixture of
outgassed and nebular-derived components, and provide a framework for assessing
the role of various mechanisms of gas loss over the entire history of the
planet.
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