What Have We Done? The issues with interplanetary contamination

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Humans have been trying to endure the final frontier for decades, with the first historic cosmonaut, Yuri Gagarin, leaving the safety of our planet in 1961 to spend an hour and 45 minutes orbiting Earth. Since then, space exploration has only grown in investment and enthusiasm; the first space walk in 1965, the first human on the moon in 1969, the first pictures of Mars surface in 1976, flybys of Uranus (1986), Neptune (1989) and Pluto (2015). But as our contact with the astronomical grows, how much of our planet are we leaving in space?

Interplanetary contamination is the transferral of biological material from one planet to another.  There are two forms of interplanetary contamination:

• Forward contamination – From Earth to another planet.
• Backward contamination – From another planet to Earth.

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This can be achieved by incautious space crews and/or unsterile space exploration equipment transmitting biological materials to other planets. The terminology is the same whether the act of contamination was committed deliberately or unintentionally. Interplanetary contamination is taken very seriously, to the point where there are laws in place to restrict it as much as possible, and there is good reason as to why.

The fundamental reason to restrict backward contamination is pretty simple; to prevent the spread of any possible extra-terrestrial infections or invasive species on our home planet. Forward contamination is restricted for a similar reason – there is so much of space to explore, we don’t want to compromise it by transferring any of our microbial life or invasive species to new celestial terrain! There are few Earthly organisms that could actually colonise (or even survive) other planets, but that doesn’t mean that it’s impossible. ‘Extremophile’ is a term coined for microorganisms that can thrive in extreme environments, the domain Archaea residing comfortably within that bracket. Archaea can be found in the most ruthless of Earth’s ecosystems; thermophilic archaea can be found in 100^oC< geysers, halophiles can be found in salt lakes with salinities as high as 25%, and acidophiles can be found at pH’s of 0! So, it’s not unthinkable that planets with similar properties could become a new home for archaea, which causes ethical concerns.

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Some may argue that the concern of microbial colonisation on planets other than our own is all theoretical, but there is evidence that it has happened before. The 2019 ‘Beresheet incident’ involved the Israeli lunar lander ‘Beresheet’ crash landing on the moon due to a computer error, and was carrying some notoriously resilient microbes: tardigrades, and they were in a state of cryptobiosis, which sparked huge concern for the ecology of our moon. When tardigrades enter cryptobiosis, they are almost indestructible – they tuck in their legs, expel all moisture from their bodies, and reduce their metabolism by 99.99%, preserving themselves until they excrete the chemicals required to ‘unfreeze’. Could these hardy water bears be the future inhabitants of our moon?

In order to prevent this, space programmes invest millions in robotic spacecraft. This is because robots are the easiest and most reliable way to concoct non-contaminating exploration methods; the equipment can be sterilised before transport, it will not excrete any biological material, and it can stay in space for long periods of time without having to return to Earth, eliminating the possibility of backward contamination. But plans to deliver humans deeper into space are already being explored for more complex missions, such as NASA’s Mars exploration programme to deliver cosmonauts to Mars surface in 2033. As our technological advancements and eagerness to answer the question “What is out there?” is only growing with time, we have to make sure we match our efforts in reducing interplanetary contamination, to avoid the second question we could be asking ourselves … “What have we done?”.

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Where to find out more:

• Space Law: http://www.nlujlawreview.in/space-missions-v-environmental-integrity-of-extra-terrestrial-bodies-the-conundrum-of-interplanetary-contamination/
• Archaean habitats: https://www.ingentaconnect.com/content/tandf/usyb/2001/00000050/00000004/art00003?token=006816aea94129333f25703568293c6c567e504f58602f433e402c3541333c4a2f5f316a4d57404647233f253ec3879bd3d33ee2
• The Beresheet incident: https://www.vox.com/science-and-health/2019/8/6/20756844/tardigrade-moon-beresheet-arch-mission
• NASA’s Mars exploration programme: https://www.nasa.gov/sites/default/files/atoms/files/journey-to-mars-next-steps-20151008_508.pdf