Exploring a Reducing Greenhouse Environment for Early Mars in the Aftermath of an Impact
Abstract
Collision induced absorption between CO 2 and reducing greenhouse gases H 2 and CH 4 has been shown to be capable of increasing atmospheric opacity for early Mars and potentially raising surface temperatures above freezing. Several potential sources have been proposed to introduce these gases into the early Martian climate, including volcanic outgassing, serpentinization, and impact degassing. Here we explore the impact degassing hypothesis and the potential resulting climate from such an event using the NASA Ames 3-D early Mars Global Climate Model (eMGCM). If an impactor delivered sufficient quantities of reductants (such as Fe and organics) to the early Martian atmosphere, these could react with H 2 O and CO 2 in the extremely hot post-impact environment to produce reducing gases like H 2 and CH 4 . In this study, we focus on the production of H 2 through the reaction of reduced Fe delivered by an impactor and H 2 O vaporized during crater formation from the impactor itself and from Martian subsurface ice. We estimate that in a 2-bar CO 2 atmosphere, a 100-km diameter asteroid that is 30% Fe by weight could produce H 2 with a molar mixing ratio of up to 0.054. We simulate this post-impact climate scenario with the eMGCM accounting for H 2 degassing as well as a scenario of the same impactor size and atmospheric surface pressure in which no H 2 is produced. We examine the global distribution of rainfall and of warm surface temperatures in the aftermath of this 100-km diameter impactor in a 2-bar CO 2 atmosphere and assess whether such an environment is consistent with geologic evidence of fluvial activity such as crater degradation and the formation of nontronite-rich clays.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P23B3477S
- 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