Humans Could Kill Life On Mars, If It Doesn’t Kill Us First

A human visitor to the Red Planet could bring along a devastating microbe on his spacesuit, or bring one back to Earth when he returns.

A human visitor to the Red Planet could bring along a devastating microbe on his spacesuit, or bring one back to Earth when he returns.

Humans may some day visit Mars, but if — and when — we do, we run the risk of bringing a bacterium or virus that could wipe out all life on the red planet, USA Today is reporting. What’s worse, when we return home from Mars, we may bring a deadly pathogen home with us — one that could wipe out all life on Earth.

The microbiology community has known for a century or so that our immune systems don’t always respond very well to “foreign” microbes to which they’ve never had exposure. That’s why, when Europeans first visited the Western Hemisphere, they brought with them smallpox, a devastating disease that had been in their own populations for millennia, but which were new to the Native American tribes. By some accounts, smallpox killed a large proportion of the contemporary Native Americans, per PBS.

And in the case of a literal alien organism, the effects could be much, much worse.

A spacecraft is, in some ways, a vector of human and other Earth-bound diseases. That’s why NASA sent the Cassini probe to a fiery death in Saturn’s atmosphere after it had completed its mission; scientists were concerned that the craft might have brought along some Earthly microbes that could infect whatever rock it landed on. Instead, they sent it to its certain death, according to PBS.

The problem is magnified exponentially when it comes to Mars. Already scientists take great care to sanitize and disinfect any craft that winds up there, lest it introduce a fatal disease into the Martian ecosystem. Pardis Sabeti, professor of immunology and infectious diseases at Harvard University, says that — even unintentionally — an Earth microbe could devastate Mars.

“There’s all sorts of ways that when different life forms interact for the first time, all sorts of intentional and unintentional destruction can happen.”

That’s why we’ve been sending robots up there: besides being cheaper, they’re also cleaner. Indeed, Sabeti notes that a Mars-bound spacecraft is subjected to high heat for days to kill off all microbes, something that can’t be done with humans. And when we do figure out a way to send humans up there, each one will be bringing along with them literally trillions of bacteria and viruses.

Even worse, an astronaut or spacecraft returning from Mars could bring with it a potentially-lethal Martian microbe, says Sabeti.

“There’s not a high reason to think that there’s an infectious disease there that can infect us and become problematic to us, but if it could, then it could rapidly become really problematic.”

That’s why any returning Martian spacecraft, or human visitor, will have to spend days in a containment lab once they get back. But if we do manage to bring back a sample of a living Martian organism, it will all be worth it, says Casey Dreier, chief advocate and senior space policy adviser at The Planetary Society.

“If we find life on a sample from Mars, or some hint of life from the past, that would be one of the biggest discoveries in human history.”