The risk that Martian microbes exist, and could cause disease in humans, is considered to be very small. It is one of the aspects of planetary protection. Other vectors for illnesses might be viruses or prions.
Precautions to manage this risk include the following:
- rules that limit direct and indirect human contact with the martian environment, particularly when relatively warm and wet conditions are present (e.g. "airlock procedures, sample transportation and handling, and in-situ resource utilization"). A specific example would be procedures specifying how and under what circumstances space suits will be decontaminated upon return to spacecraft/habitats.
- rules that limit where humans may travel, including use of robots to conduct initial evaluation of unexplored sites
- life support systems designed to prevent contamination of air and water supplies
- medical monitoring, including markers of immune system function
- monitoring of normal human microbiomes and free-living microbes inside spacecraft/habitats
- habitats designed to separate living areas from research facilities (e.g. lab facilities that meet biosafety level 2 standards)
- a facility for quarantine of someone who may have been infected with a martian microbe
A related risk is the possibility that microbes carried from earth could evolve to become more pathogenic in a different environment. There is also the possibility that the human immune system could weaken in the absence of the normal scope of interactions with earth microbes, leading to infections with normally benign microbes carried from earth.
Planetary protection measures would be implemented upon completion of a Mars exploration mission to ensure that any microbes carried by astronauts, equipment, or samples cannot be transferred to the Earth environment. For example, Apollo astronauts were quarantined for 21 days after returning.
National Research Council. 2002. Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface. Washington, DC: The National Academies Press. https://doi.org/10.17226/10360.
- Rummel JD, Race MS, Conley CA, Liskowsky DR. (2010). The Integration of Planetary Protection Requirements and Medical Support on a Mission to Mars. Journal of Cosmology 12:3834-3841. Retrieved from http://journalofcosmology.com/Mars126.html
- Netea MG, van de Veerdonk FL, Strous M, van der Meer JWM. (2010). Infection Risk of a Human Mission to Mars. Journal of Cosmology 12:3846-3854. Retrieved from http://journalofcosmology.com/Mars129.html