Non-thermal escape of the Martian CO2 atmosphere over time: Constrained by Ar isotopes

H.I.M. Lichtenegger*, Sergey Dyadechkin, Manuel Scherf, H. Lammer, Raven Adam, Esa Kallio, Ute Amerstorfer, Riku Järvinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

The ion escape of Mars’ CO 2 atmosphere caused by its dissociation products C and O atoms is simulated from present time to ∼4.1 billion years ago (Ga) by numerical models of the upper atmosphere and its interaction with the solar wind. The planetward-scattered pick-up ions are used for sputtering estimates of exospheric particles including 36Ar and 38Ar isotopes. Total ion escape, sputtering and photochemical escape rates are compared. For solar EUV fluxes ≥3 times that of today's Sun (earlier than ∼2.6 Ga) ion escape becomes the dominant atmospheric non-thermal loss process until thermal escape takes over during the pre-Noachian eon (earlier than ∼4.0–4.1 Ga). If we extrapolate the total escape of CO 2-related dissociation products back in time until ∼4.1 Ga we obtain a maximum theoretical equivalent to CO 2 partial pressure of more than ∼0.4 bar through non-thermal escape during quiet solar wind conditions. However, surface–atmosphere interaction and/or extreme solar events such as frequent CMEs could have increased this value even further. By including the surface as a sink, up to 0.9bar, or even up to 1.8bar in case of hidden carbonate reservoirs, could have been present at 4.1Ga The fractionation of 36Ar/ 38Ar isotopes through sputtering and volcanic outgassing from its initial chondritic value of 5.3, as measured in the 4.1 billion years old Mars meteorite ALH 84001, until the present day, however, can be reproduced for assumed CO 2 partial pressures of ∼0.01–0.4bar without, and ∼0.4–1.8bar including surface sinks, and depending on the cessation time of the Martian dynamo (assumed between 3.6 and 4.0 Ga) — if atmospheric sputtering of Ar started afterwards.

Original languageEnglish
Article number115009
Number of pages57
JournalIcarus
Volume382
Early online date2022
DOIs
Publication statusPublished - Aug 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • Atmospheric loss
  • Hybrid simulation
  • Atmospheric sputtering
  • Hot particles

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