Microbial Growth in Martian Soil Simulants Under Terrestrial Conditions: Guiding the Search for Life on Mars

The search for life elsewhere in the Universe goes together with the search for liquid water. Life as we know it requires water; however, it is possible for microbial life to exist under hyperarid conditions with a minimal amount of water. We report on the ability of two typical terrestrial bacteria ( and sp) and two extremophiles ( -20201027-1 sp and ) to grow and survive in three martian soil (regolith) simulants (Mohave Mars Simulant-1 [MMS-1] F, Mars Global Simulant-1 [MGS-1], and JSC Mars-1A [JSC]). Survival and growth were assessed over a 21-day period under terrestrial conditions and with water:soil (vol:wt) ratios that varied from 0.25:1 to 5:1. We found that and sp grew best in the simulants MMS and JSC, respectively, while growth rates were better in the JSC simulant. As expected, did not show significant growth. Our results indicate that these martian simulants and thus martian regolith, with minimal or no added nutrients or water, can support the growth of extremophiles such as and . Similar extremophiles on early Mars may have survived to the present in near-surface ecological niches analogous to those where these organisms exist on Earth.