Bob McDonald's blog

Our lowly microbes could kill off Martian life, scientists fear

If we continue to send 'dirty' robots to look for life on Mars, our instruments could indeed detect microbes there, but they might have come from Florida.

A colony on Mars could be a microbiome of organisms that hitched a ride on a spaceship or human bodies

There's an urge to send humans to Mars by the 2030s. (Pat Rawlings/SAIC/NASA)

This week, researchers announced that erosion on steep slopes of Mars exposed multiple sites of huge ice deposits. It could be a useful source of water for future missions to the Red Planet.

But it may give scientists one more reason to worry that any native life that might exist on Mars today could be infected or even killed off by the presence of humans.

There's an urge to send humans to Mars by the 2030s, either through NASA, or private companies such as Space-X, 

But no one knows if Martian life even exists.

In the classic story, The War of the Worlds by H.G. Wells, malevolent Martians invade the Earth with horrifying machines more powerful than our most destructive weapons. The unstoppable aliens begin destroying cities in an apparent attempt to wipe out humanity and take over our planet. When all seems lost, the aliens and their machines suddenly collapse, not because of our weapons fired against them, but because of a virus they picked up on our planet for which they had no immunity. The lowly microbe brought down the mighty Martians.

At the 2017 International Astronautical Congress, Elon Musk revealed new plans about vehicles that will take people to Mars. (SpaceX)

In a report issued last October, biologists searching for life on Mars expressed concerns that humans, along with our associated microbes, could do the same thing, in the opposite direction, as we invade Mars with our astronauts and space colonies. They are concerned that human microbes brought to Mars could contaminate or even wipe out native Martian life and suggest a series of robotic missions to first identify whether or not any life exists on Mars and if it is similar or different to our own — before the first boot prints and flags are planted in the red soil.

Since the 1970s, a number of robots have landed on Mars, with two rovers, Opportunity  and Curiosity, still driving around on the surface today. In the early days, there was a protocol for planetary protection that demanded spacecraft be free of Earthly contaminants before landing on another world. The two Viking landers in 1976, the first to carry experiments to look for life, were dried and baked at high temperature, then sealed in airtight capsules before launch.

Sadly, the life experiments on Viking were inconclusive, so the search continues. But since then, the standards for cleanliness on robots have been lowered, because Mars turns out to be an incredibly hostile environment, including:

  • Extremely low temperatures.
  • Ultra-dry soils.
  • No oxygen in the atmosphere.
  • No ozone layer to filter UV radiation from the sun or cosmic radiation from space.

Earthly microbes would have a hard time surviving there, let alone proliferating and spreading. Because of that, spacecraft that land on Mars today are still clean, but dirtier than Viking, and do carry some microbes.

But beyond contaminating Mars, the scientists are also concerned about two of the most fundamental questions in science: Is there life beyond Earth, and if so, is it the same type of carbon-based, DNA replicating life as ourselves?

A series of robotic missions could first identify whether or not any life exists on Mars before the first boot prints are planted in the red soil. (Getty Images)

If we continue to send "dirty" robots to look for life on Mars, our instruments could indeed detect microbes there, but they might have come from Florida. And if we do identify truly alien life on Mars, how do we study it without contaminating it?

Cross-contamination between planets is a serious issue as humans begin leaving Earth. The human body is a microbe factory, with billions of organisms living on our skin, which we shed constantly, more microbes in our exhaled breath, coughs and sneezes, along with our water and food products.  A colony on Mars would harbour more than humans. It would also be a microbiome of life that hitched a ride on bodies and in our spaceships.

Before going to another world, we must identify who lives there and what kind of threat they pose to us, or more likely, that we pose to them.

No one wants another war of the worlds on any scale.

About the Author

Bob McDonald

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.