Comparative Study of the Ability of Three Martian Simulants to Support Bacterial Growth

Abstract:

One key question about Mars is whether life has been or still is present on or beneath its surface. For life to flourish, it requires a habitable environment with the appropriate physical and chemical regolith parameters. To better understand the parameters that constitute a habitable environment, leachates of three martian simulants (JSC Mars-1, MMS-1 fine, and MGS-1) were analyzed for their soluble ionic composition, pH, and conductivity in order to determine the presence of any beneficial or toxic elements and their effects on the two bacteria E. coli and Eucapsis.

E.coli was cultured in minimal media where acetic acid was the only organic source, and tested its requirements for a carbon source (acetic acid), nitrogen source ((NH₄)₂SO₄) as well as trace elements (Ca, Mn, Zn, Cu, Fe, Co, Mo). In minimal culture media with all nutrients available for healthy growth, E. coli showed substantial growth. In the case of a carbon-only source or nitrogen-only source in MMS-1 soil leachate, E. coli showed limited growth compared to that observed in the full minimal culture media. Assessing Eucapsis growth, among the three leachates tested MMS-1 displayed the best growth. Additionally, we observed that MMS-1+Allen’s minimal and full Allen’s medium groups displayed similar growth curves, indicating that MMS-1 can provide all the trace elements needed for Eucapsis growth.

Among all the leachates, MMS-1 showed the most promising results. MMS-1 + Allen’s medium provided the highest Eucapsis growth. MGS-1 + Allen’s minimal media also showed significantly higher growth than MGS-1 alone. However, JSC and JSC + Allen’s minimal did not show any significant difference regarding Eucapsis growth. The results indicated that Eucapsis grew best in both MMS-1 F leachate only and MMS-1 F leachate with Allen’s minimal medium.