TY - JOUR

T1 - 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

AU - Bak, Ebbe Norskov

AU - Nornberg, Per

AU - Jensen, Svend J. Knak

AU - Thogersen, Jan

AU - Finster, Kai

PY - 2022/10

Y1 - 2022/10

N2 - 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.

AB - 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.

KW - Methane cycling of Mars

KW - radiation

KW - reactive oxygen species

KW - saltation

KW - Viking biological experiments

KW - BACILLUS-SUBTILIS SPORES

KW - HYDROGEN-PEROXIDE

KW - LABELED RELEASE

KW - DEINOCOCCUS-RADIODURANS

KW - OXIDATIVE STRESS

KW - GALE CRATER

KW - OXIDANT ENHANCEMENT

KW - IONIZING-RADIATION

KW - HYDROXYL RADICALS

KW - VIKING MISSION

U2 - 10.1017/S1473550421000392

DO - 10.1017/S1473550421000392

M3 - Review

VL - 21

SP - 356

EP - 379

JO - International Journal of Astrobiology

JF - International Journal of Astrobiology

SN - 1473-5504

IS - 5

M1 - 1473550421000392

ER -