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Missing Carbonate on Mars: Exploring Buried Carbonate on Mars Using Geophysical Methods

Mars,Carbonate,Carbon Cycle

Theme 6: Life Elsewhere: Biosignature Generation and Exploration > Session 6a: Recent Advances in Astrobiology

Abstract: As our neighbor in the Solar System, life on Mars remains one of the most interesting scientific questions since the exploration on Mars began. From our understanding of life on Earth, the possibility of emergence and perseverance of life on Mars, i.e., the habitability of Mars, highly depends on the stable existence of liquid water. So far, many observations on Mars have witnessed the existence of liquid water, even hydrological systems or oceans, in ancient Mars. Ancient riverbeds and remnants of lake chains scattered throughout the old Noachian and Hesperian terrains (Fassett and Head, 2008). Hydrated minerals such as phyllosilicates are also widespread (Ehlmann et al., 2010). In light of these observations, it is commonly accepted that ancient Mars was warm enough to maintain at least periods of liquid water, which elevates the potential of life on Mars. However, a habitable ancient Mars faces the same problem as ancient Earth: the “Faint Young Sun Paradox.” Astrophysical studies have proved that the ancient sun was ~30% weaker than now, emitting less radiation to planets in the solar system. Less solar radiation provides less energy for planets to maintain their temperature. Therefore, a possible solution is that Mars used to have a thick, CO₂-enriched atmosphere to keep its greenhouse effect. Two contradictions emerged under this scenario. (a) Under high pCO₂ in the Martian atmosphere and with liquid water, massive carbonate should be formed compared with Earth. However, massive carbonate was not reported anywhere on Mars. (b) CO₂ is hard to be entirely removed by solar wind or other processes. Also, different surface processes, such as polar cap sequestration, did not provide enough sinks for atmosphere CO₂. The carbon cycle on Mars is, therefore, not in balance without the additional sink of massive carbonate. Modern Mars is covered by aeolian deposits and sediments altered by secondary processes, which could hinder our traditional detection of buried carbonate, which has been reported in crater excavation studies (Michalski and Niles, 2010). Geophysical processes, specifically ground penetrating radar, provide a method to detect underneath the Martian surface. Here, we analyze data from Zhurong and other Mars landing missions to examine buried carbonate and re-evaluate the ancient carbon cycle on Mars.



Reference

Ehlmann, B.L., Mustard, J.F., Murchie, S.L., 2010. Geologic setting of serpentine deposits on Mars. Geophysical Research Letters 37. https://doi.org/10.1029/2010GL042596

Fassett, C.I., Head, J.W., 2008. The timing of martian valley network activity: Constraints from buffered crater counting. Icarus 195, 61–89. https://doi.org/10.1016/j.icarus.2007.12.009

Michalski, J.R., Niles, P.B., 2010. Deep crustal carbonate rocks exposed by meteor impact on Mars. Nature Geosci 3, 751–755. https://doi.org/10.1038/ngeo971