Silicates Eroded under Simulated Martian Conditions Effectively Kill Bacteria—A Challenge for Life on Mars

Abstract

The habitability of Mars is determined by the physical and chemical environment. The effect of low water availability, temperature, low atmospheric pressure and strong UV radiation has been extensively studied in relation to the survival of microorganisms. In addition to these stress factors, it was recently found that silicates exposed to simulated saltation in a Mars-like atmosphere can lead to a production of reactive oxygen species. Here, we have investigated the stress effect induced by quartz and basalt abraded in Mars-like atmospheres by examining the survivability of the three microbial model organisms Pseudomonas putida, Bacillus subtilis, and Deinococcus radiodurans upon exposure to the abraded silicates. We found that abraded basalt that had not been in contact with oxygen after abrasion killed more than 99% of the vegetative cells while endospores were largely unaffected. Exposure of the basalt samples to oxygen after abrasion led to a significant reduction in the stress effect. Abraded quartz was generally less toxic than abraded basalt. We suggest that the stress effect of abraded silicates may be caused by a production of reactive oxygen species and enhanced by transition metal ions in the basalt leading to hydroxyl radicals through Fenton-like reactions. The low survivability of the usually highly resistant D. radiodurans indicates that the effect of abraded silicates, as is ubiquitous on the Martian surface, would limit the habitability of Mars as well as the risk of forward contamination. Furthermore, the reactivity of abraded silicates could have implications for future manned missions, although the lower effect of abraded silicates exposed to oxygen suggests that the effects would be reduced in human habitats.

Amorphization of S, Cl‐Salts Induced by Martian Dust Activities

“…Wang, Yan, Dyar et al, (2020) (and this study), A. Wang, Bradley, Yan (2020) and by another group in Denmark (Bak et al, 2016(Bak et al, , 2018Bak, Larsen et al, 2017;Bak, Zafirov et al, 2017;Knak Jensen et al, 2014;Thoegersen et al, 2019).…”

“…The potential effects in chemistry and biology of ESD induced by Mars dust activities have been investigated and reported by Wu et al (2018), and A. Wang, Yan, Dyar et al, (2020 (and this study), A. Wang, Bradley, Yan (2020) and by another group in Denmark (Bak et al, 2016(Bak et al, , 2018Bak, Larsen et al, 2017;Bak, Zafirov et al, 2017;Knak Jensen et al, 2014;Thoegersen et al, 2019).…”

“…Above expectations were validated by our experimental observations (Wu et al., 2018) of CO 2+ , CO + , O I , H III , H II , OH, Ar I , N 2 , N 2 + by in situ plasma emission spectroscopy (also O 2 , NO, and O + because of the overlapping of plasma lines used for detection, Figure ) and O 3 in the output gas by UV and mid‐IR spectroscopy (Figure 5 of Wu et al., 2018), generated by normal glow discharge (ESD‐NGD) under simulated Mars atmospheric composition and pressure. During a simulated saltation experiment on silicates upon contact of water (Bak, Zafirov et al., 2017), H 2 O 2 and •OH were detected. Furthermore, Aerts et al.…”

“…In a set of experiments simulating grain saltation using silicates under Mars atmospheric composition and pressure, Bak, Zafirov et al. (2017) detected light emissions (red colored glow from quartz sand and blue colored glow from basaltic sand) that are similar to NGD in a Mars chamber simulated in our laboratory (A. Wang, Bradley, Yan, 2020; A. Wang, Yan, Dyar et al., 2020; A. Wang, Yan, Jolliff et al., 2020; Wu et al., 2018).…”

Surviving Mars: new insights into the persistence of facultative anaerobic microbes from analogue sites

“…For example, plants grow worse in MGS-1 than in other artificial Martian soils (Eichler et al, 2021). In other experiments, it has been shown that basalt as a Mars analogue regolith and also silicates in combination with a movement that mimics wind-driven saltation can have a negative or even deadly influence on microorganisms (Bak et al, 2017(Bak et al, , 2019. A slight negative influence of Martian regolith for the fungal species Cryomyces antarcticus was recently demonstrated by Aureli et al (2020).…”