The influence of carbon escape on the evolution of the Martian atmosphere
Abstract
The purpose of this study is to investigate the evolution of atmospheric composition in the early Martian atmosphere. Not only hydrogen and oxygen escapes but also carbon escape to space is considered in this study for two reasons. The first reason is that thermal escape of atomic carbon could be stronger than atomic oxygen on early Mars. The early Martian atmosphere was exposed to stronger Sun' EUV and FUV radiations than today. The escape parameter, defined as the ratio of the gravitational potential to kinetic energy at a given altitude, could be small enough to allow massive escapes of these species under such strong radiations. For example, the escape parameter of atomic carbon in the Martian atmosphere was estimated 0.75 times smaller than that of atomic oxygen, and because of an efficient dissociation of CO2 the densities of these species at the exobase level were comparable at 4.1 Gyr ago (Tian et al., 2009). Hence, we consider that on early Mars, thermal escape of atomic carbon could be stronger than atomic oxygen. The second reason is the discovery of the concentration of Mn in Gale Crater by Curiosity, which suggests that the early Martian atmosphere could have several mbar or more of O2 partial pressure (Noda et al., 2019). Previous 1-D photochemical models that considered hydrogen and oxygen escapes on current Mars suggested that the O2 partial pressure could increase only up to 10-5 bar (e.g., Chaffin et al., 2017). This is because the atmosphere self-regulates the loss of hydrogen and oxygen to 2:1 (McElroy, 1972), which limits the imbalance between the hydrogen and oxygen escapes and hence prevents a massive oxygen buildup in the atmosphere. In this study, we consider atomic carbon escape as an agent toaccumulate O2 in the atmosphere. To investigate this effect, we use a 1-D photochemical model of the early Martian atmosphere that takes into account atomic carbon escape. In this presentation, we will show the influence of the atomic carbon escape to the evolution of O2 partial pressure left behind in the early Martian atmosphere.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P23B3483Y
- 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