Physical and chemical mechanisms that impact the detection, identification, and quantification of organic matter and the survival of microorganisms on the Martian surface – a review

Abstract

The iconic Viking Landers that landed on Mars in 1976 demonstrated that the Martian surface is an extreme place, dominated by high UV fluxes and regolith chemistry capable of oxidizing organic molecules. From follow-on missions, we have learned that Mars was much warmer and wetter in its early history, and even some areas of Mars (such as crater lakes, possibly with sustained hydrothermal activity) were habitable places (e.g. Grotzinger et al. (2014). Science (New York, N.Y.) 343; Mangold et al. (2021). Science (New York, N.Y.). However, based on the Viking results we have learnt that the search for life and its remains is challenged by abiotic breakdown and alteration of organic material. In particular, the harsh radiation climate at the Martian surface that directly and indirectly could degrade organics has been held accountable for the lack of organics in the Martian regolith. Recent work simulating wind-driven erosion of basalts under Mars-like conditions has shown that this process, comparable to UV- and ionizing radiation, produces reactive compounds, kills microbes and removes methane from the atmosphere. and thereby could equally jeopardize the success of life-seeking missions to Mars. In this review, we summarize and discuss previous work on the role of physical and chemical mechanisms that affect the persistence of organics, and their consequences for the detection of life and/or its signatures in the Martian regolith and in the atmosphere.

Special issue: Open questions and next steps in astrobiology in Europe – celebrating 20 years of EANA

“…This review is focused on abiotic alterations of organic material on Mars such as those caused by UV-and ionizing radiation and wind-driven erosion. Bak et al (2022) reviewed extensively the role of physical and chemical mechanisms for the preservation of organics in the Martian surface regolith. Their comprehensive review demonstrates the difficulties for the identification of life on Mars and emphasises the crucial importance of laboratory experiments to distinguish between abiotic breakdown and biological alteration of organic material in the Martian regolith.…”