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/He-rich nebular atmosphere. We conduct
calculations of nebular capture with and without a mixed-in high molecular
weight outgassed component during the lifetime of the solar nebula. Mixing in
an outgassed component enhances the captured nebular 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 hybrid mixture of outgassed and nebular-derived
components and that – irrespective of the precise composition of the outgassed
component – was mainly composed of molecular hydrogen. The consequences for
Martian atmospheric history are discussed.
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