Carbon Photochemical Escape Rates from the Modern Mars Atmosphere
Abstract
We present an updated comprehensive picture of photochemical escape of carbon from the Martian atmosphere today. Using updated photochemical and escape models, we characterize the main processes behind the production of hot atomic C and the escape probabilities of the hot C under high and low solar activity scenarios. We find that CO photodissociation rates are an order of magnitude higher than previously reported in the literature. CO photodissociation involves transitions to CO pre-dissociating states, and previous studies have neglected to use sufficiently high spectral resolutions to resolve the sharp peaks associated with these transitions. Our results show that the use of high spectral resolution is critical in the accurate calculation of CO photodissociation rates. We also characterize the contribution to C escape from a newly-identified branch of CO2 photodissociation. This contribution from CO2 photodissociation to C escape is potentially bigger than the contribution from CO photodissociation. The contributions of many minor reactions, such as electron impact reactions, are reported for the first time. With the additional contributions from CO2 photodissociation and the other minor reactions, the total C escape rate is significantly higher than what has been previously reported in the literature. Finally, we compare our model results against observations by MAVEN/IUVS. While IUVS is unable to directly observe escaping C, many of the same reactions producing escaping C also produce electronically excited C via another branch that can be observed. We provide a comparison between the C I 156 nm and C I 166 nm emission profiles from our model results with those observed by MAVEN/IUVS, and offer a perspective into the various processes driving the two emissions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P21A..04L
- 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