The chance of discovering microbial life on Mars might be better than scientists expected, suggests a new paper published Tuesday in the journal Astrobiology. Researchers say there’s a possibility that ancient, dormant bacteria still exist beneath the Red Planet’s surface.
One microbe seems especially well-suited for surviving in Mars’ incredibly harsh conditions: Conan the Bacterium. Formally known as Deinococcus radiodurans—which roughly translates to “strange berry that withstands radiation”—this Earth-dwelling, orange, multi-celled species earned the moniker Conan for its ability to survive extreme conditions.
Now, experiments suggest the tough microbe, if buried 33 feet below the Martian surface, may be able to survive for about 280 million years. It’s evidence that there may be similar species lying dormant in the ground on Mars.
“If Martian life ever existed, even if viable lifeforms are not now present on Mars, their macromolecules and viruses would survive much, much longer,” says study lead author Michael Daly, a pathologist at Uniformed Services University of the Health Sciences, in a statement. “That strengthens the probability that, if life ever evolved on Mars, this will be revealed in future missions.”
Mars is an exceedingly hostile place. The planet’s surface is dry and frozen, and cosmic radiation and solar protons are constantly bombarding it. But that may not have always been the case—scientists believe water flowed on Mars between 2 and 2.5 billion years ago, which would’ve made the planet slightly more hospitable.
Researchers were curious to know what kind of life might have evolved—and, potentially, survived into the present—on the Red Planet. To attempt to answer that question, they mimicked the cold, arid conditions of Mars here on Earth with six species of microorganisms.
They exposed these microbes and fungi to ultraviolet light and blasted them with varying doses of protons and gamma rays to simulate radiation in space. Large doses mimicked the conditions of Mars’ near subsurface, while smaller doses replicated what a microbe might endure if buried far underground.
The results of their simulations suggest some microorganisms may be able to survive the conditions on Mars for hundreds of millions of years. If frozen, dried and deeply buried, Conan the Bacterium may be able to endure 140,000 grays of radiation, they found. (Humans, on the other hand, would die after prolonged exposure to about five grays of radiation and can suffer serious health issues after exposure to just 0.3 grays.) On the Martian surface, this hardy microbe could only survive for a few hours. But if buried about four inches below the surface, the researchers believe it could persist for as long as 1.5 million years. At 33 feet below ground, its lifetime extends to 280 million years, they estimate.
If a microbe like Conan the Bacterium once roamed Mars, there’s a possibility that its “sleeping” remains are still buried underground. Even if dormant, the microbes could not have survived the full 2 to 2.5 billion years since water flowed on Mars. But meteorite collisions over the years could have melted the Martian surface and altered the environment just enough to allow the microbes to intermittently wake up, reproduce and spread, the researchers say.
These findings suggest that scientists should treat with caution any future samples brought back to Earth—such as those planned for missions like ExoMars and the Mars Life Explorer—because of the possibility of contamination by extraterrestrial bacteria.
And, similarly, all future missions to the Red Planet should take into account the potential for hitchhiking microorganisms from Earth, experts say. Currently, scientists sterilize robotic missions to Mars before launch, but the process is not completely fool-proof.
If astronauts ever venture out to the Red Planet, they’ll need to be extra careful of their impact. As Keith Cooper writes for Space.com, humans will bring “many more microbes with them, which could escape out into the Martian environment and either destroy the native microbial biosphere or confuse experiments looking for life on Mars.”