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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

To go where no germ has gone before: Does Mars rover have a stowaway?

Guest Blog by Carol A. Kemper, MD, FACP, clinical associate professor of medicine, Stanford University, division of infectious diseases, Santa Clara Valley (CA) Medical Center

A recent fascinating article delves into a previously unrecognized area of Infectious Disease for me - Space ID! The 1967 “Outer Space” treaty between the United States, England, and the Soviet Union that governs space travel stipulates that countries should avoid contamination of other worlds and planets with microbial life from Earth. Not quite the “Prime Directive” Gene Roddenberry had in mind, which governed Star Fleet interstellar travel (remember, “the right of each sentient species to live in accordance with its normal cultural evolution is considered sacred”), but something close.

Similar to the Prime Directive, this treaty provision is variably applied by NASA depending on where the mission is going, and which vehicle is employed to get there. The space agency actually classifies missions according to the estimated risk of bacterial cross-contamination, although budget concerns help to frame the guidelines. While travel to the space station is considered lower risk, travel to Mars is higher risk. Therefore, when the space rover Curiosity was being developed, she spent her life in a “clean room” at the Jet Propulsion Laboratory, tended to by engineers and technicians wearing protective gear. The shell of the Rover and all external equipment was specifically designed to diminish the risk of bacterial and fomite carriage, with a goal of total surface bacterial colonization less than 300,000 colonies (a wee amount when compared with the human body). Alcohol is routinely used to decontaminate hands equipment and surfaces. The implementation of a second drill bit on Curiosity, which had not been stored in the same manner as another, reportedly created a serious disagreement between engineers and microbiologists supervising the project.

The author reminds us that several Earth species have a phenomenal ability to survive in extreme conditions, such as the recently recognized thermophiles and halophiles found in lava shafts, which use iron in basalt rock as an energy source. Tardigrades, which are those bizarre pod like creatures that hang out in lichens and moss, have been found to withstand heating to 150 degrees for a few minutes, extreme cold to as low as -200 C for days, and have been found under layers of ice in the Himalayas. They can even withstand lethal amounts of gamma rays. Tardigrades can actually suspend their metabolism and go into a state of cryptobiosis for nearly 10 years. So you can understand why microbiologists are concerned about the risk of colonizing another planet. I just worry about what kind of terrifically durable species they might bring back.