What astronauts teach us about microbes

Even in a confined area like a space rocket, the microbial ecosystem remains dynamic and potentially pathogenic.

During a space flight, each astronaut introduces billions of microorganisms into the rocket--some of which could be a threat to the crew. The specific conditions of this kind of flight (lack of privacy, stress, microgravity, etc.) make infection more likely by affecting the immune system, and may also affect the structure of the microbial ecosystem. Because of its length, a trip to Mars is thus a real challenge in terms of the crew’s health and safety.

To measure this risk, six crew members took part in the Mars500 project, the first simulation of a trip to Mars lasting longer than six months. They lived together for 520 days in a replica spaceship and participated in the MICHA project on the microbial ecology of confined habitats and its impact on human health.

To no one’s surprise, the living area harbored the greatest number of germs, with staphylococci and bacilli predominant. However, huge variations existed depending on the sample site: the toilets, office, and individual compartments were the most contaminated. Although the crew was the primary source of germs, the length of their confinement was an important factor. As proof, the nature of the species varied over time, with more opportunistic and stress-tolerant bacteria emerging as their diversity dwindled. The composition of the intestinal microbiota of these “marsonauts” was also changed, although their health was unaffected.

The authors conclude that, even in conditions of extreme confinement, the microbial ecosystem remains very dynamic and adapts to environmental conditions. As a result, to maintain a healthy environment for the astronauts, it seems appropriate to take steps to prevent the development of potentially pathogenic or highly antibiotic-resistant microorganisms.


Schwendner P. et al. Microbiome (2017)5:129. Preparing for the crewed Mars journey: microbiota dynamics in the confined Mars500 habitat during simulated Mars flight and landing.