Mars Microbes Could Evade Astronaut Immune Systems

New research stemming from a Radboud University Ph.D. thesis suggests that common Earth pathogens could not only survive simulated Martian conditions but also become more dangerous to humans. The study subjected four well-known terrestrial pathogens, including the bacterium responsible for pneumonia, to a combination of extremely low pressure, desiccation, high ultraviolet radiation, and concentrated perchlorate brines.

While initial findings showed some microbes surviving up to 16 days of desiccation, a more comprehensive analysis revealed a stark contrast. When exposed to the cumulative harshness of Mars' environment—a combination of water scarcity, intense UV radiation, low atmospheric pressure, and perchlorates—survival rates plummeted, with some strains lasting only a single day. Interestingly, Martian regolith, with its jagged surfaces, appears to offer some protection by trapping water and shielding microbes from UV rays, though this benefit is offset by the presence of toxic perchlorates.

Beyond mere survival, the research highlights a concerning adaptation: physical changes in these microbes could render them less detectable by human immune systems. In some instances, bacteria physically shrank, leading to a reduced production of cytokines and reactive oxygen species by human immune cells. This suggests that microbes resilient enough to endure Mars might be more pathogenic to astronauts due to their altered physiology.

The thesis also explored the impact of Martian and lunar dust on human health. In vitro human airway cells and mice exposed to simulants of both lunar and Martian regolith experienced inflammation, increased white blood cell activity, and elevated gene expression related to mucus production and lung fibrosis, indicating a risk of chronic respiratory disease. The lunar simulant proved to be more damaging than the Martian dust, even when laced with perchlorates.

Furthermore, the study examined planetary protection protocols by testing the resilience of eukaryotic microbes like yeasts to conditions simulating journeys to Jovian or Saturnian moons. Some microbes, such as R. frigidalcoholis, were found to intentionally pause their growth cycles to prioritize DNA repair, demonstrating a survival strategy. However, the sequential nature of these experiments, rather than a simultaneous exposure to all hazards, means that real-world space conditions might present different challenges.