Could Human Contamination Kill Life on Mars?

InSight, NASA’s robotic probe, is just days away from its descent onto the surface of Mars. And while the American space agency is excited about the prospect, not everyone shares the feeling about the lander’s mission and what it means for the exploration of the red planet.

David Weintraub, Professor of Astronomy at Vanderbilt University and the author of Life on Mars: What to Know Before We Go, voices concerns in his op-ed for The robotic probes are the first step in humanity’s plan to send manned missions to the red planet. If Mars is a sterile planet, he says, a human presence creates no dilemmas. But what if it’s not – what if life does exist on Mars? In that case, a disruption by humans could lead to extinction of life on Mars.  

For life to exist on Mars, there must be liquid water, a source of heat and energy, and essential elements, including hydrogen and oxygen. Scientists hypothesize that while there’s no water on the planet’s surface, it is likely to be underground. NASA’s upcoming 2020 Mars rover will search for traces of organic life in dried-up bed lakes. Recently, NASA’s Curiosity rover discovered that the production of methane on Mars increased dramatically – which could be evidence of microbial life. Weintraub writes that because the environment on Mars is so harsh, life, “if it currently exists, almost certainly must be hiding beneath the planet’s surface.”

Robotic missions do not pose a large contamination threat because the undergo strict sterilisation procedures before launch. “The vacuum of space combined with exposure to harsh X-rays, ultraviolet light and cosmic rays would almost certainly sterilise the exteriors of any spacecraft sent to Mars,” Weintraub writes.

At the same time, “any bacteria that sneaked inside one of the rovers might arrive at Mars alive. But if any escaped, the thin Martian atmosphere would offer virtually no protection from high-energy, sterilising radiation from space. Those bacteria would be likely to be killed immediately.”

However, the picture is quite different for human travel. Astronauts and their habitats, food, tools and energy supply systems cannot possibly be sterilised the same way as a rover. What’s more, humans will produce waste and disturb the planet by attempting to extract water from underground, thus potentially contaminating the source.

The United Arab Emirates’ Mars 2117 project, SpaceX, Mars One and Blue Origin already have plans to send humans to Mars in the foreseeable future. The solution to the potential contamination, Weintraub writes, is to slow down and take a step back. “It is critical that every attempt be made to obtain evidence of any past or present life on Mars well in advance of future missions to Mars that include humans. What we discover could influence decisions on whether to send colonists there.”

He adds that there are also many ethical and legal questions: “If life already exists on Mars, then Mars, for now at least, belongs to the Martians. Mars is their planet, and Martian life would be threatened by a human presence there.” Therefore, if humans are able to survive on Mars, does that mean that they have the right to do so? He ends his op-ed with the hypothetical question: “Do ethics demand that we use those tools to answer definitively whether Mars is inhabited or sterile before we put human footprints on the Martian surface?”