Planetary science: Compounds on the surface may not support life on Mars

The surface of Mars may be bacteriocidal owing to the presence of chemical compounds called perchlorates, according to a study in Scientific Reports.

Perchlorates have been detected on the surface of Mars, raising questions about their influence on the habitability of the planet.

Jennifer Wadsworth and Charles Cockell investigated the potential reactivity of perchlorates and their effect on the viability of Bacillus subtilis, a common contaminant found on spacecraft. The authors found that when magnesium perchlorate was irradiated under short-wave UV radiation (similar to conditions encountered on the surface of Mars), it became bacteriocidal. At perchlorate concentrations similar to those found in Martian surface regolith (the mixture of dust, soil and broken rocks) vegetative cells of B. subtilis lost viability within minutes under Martian analogue conditions. The authors also suggest that two other components of the Martian surface, iron oxides and hydrogen peroxide, act in synergy with perchlorates resulting in a 10.8-fold increase in cell death when compared to the reaction with perchlorates.

Although the toxic effects of the Martian surface have been suspected for some time, the authors’ observations suggest that the surface of Mars is highly deleterious to cells, caused by a toxic cocktail of oxidants, iron oxides, perchlorates, and UV irradiation. The findings could have implications for planetary protection, specifically concerning the potential contamination of Mars by robotic and human exploration.