Why scientists think upcoming samples from Mars may contain evidence of life

Over the next decade, various space agencies plan to return a Martian rock back to Earth for the first time — and according to a new study published Tuesday in the journal Astrobiology, whoever analyzes these precious samples may one day stumble upon something amazing: evidence of extraterrestrial life.

In short, a team of researchers says that if organisms really did live on Mars long ago when it was a watery oasis, a group of them could have withstood the planet’s toxic transformation over the next many millennia, standing strong as that world became the wasteland we see today. But here’s the kicker.

The researchers specifically hypothesized that any organisms buried underground would have survived the longest, and therefore believe that the remains of these creatures may still be hiding beneath the Martian soil. As upcoming missions, such as ExoMars by Roscosmos and the European Space Agency, are poised to retrieve sediment from underground mars maybe we’ll see some groundbreaking extraterrestrial evidence soon.

“If life on Mars ever existed, even if viable life forms were not present on Mars now, their macromolecules and viruses would survive much, much longer,” Michael Daly, a pathologist at the Uniformed Services University of the Health Sciences and lead author of the study, said in a statement. “This increases the likelihood that if life ever evolved on Mars, it will be revealed in future missions.”

And in fact, thanks to Daley’s experimental simulations, we may already know the name of the tiny organism (or at least its sibling) waiting to be forensically excavated on Mars: Conan — Conan the Bacteria, that is.

But more on Conan in a moment.

Also, as an important side note, the team’s findings highlight how all future Mars missions should exercise extreme caution. Basically, looking at the experimental results in reverse leads to the knowledge that if we contaminate Mars with Earth bacteria in some way, perhaps from astronaut boots or scientific equipment, those transferred microbes won’t just die. They could survive on the virgin planet for an excruciatingly long time.

“We concluded that terrestrial pollution on Mars would be essentially constant — over time frames of thousands of years,” Brian Hoffman, a Northwestern University chemist and co-author of the study, said in a statement. “This could complicate scientific efforts to search for Martian life.”

“Similarly,” he continues, “if microbes evolved on Mars, they could survive to the present day. This means that returning samples from Mars could contaminate Earth.”

Time to blast organisms with extreme radiation

Despite humanity’s nascent excitement over the idea of ​​settling Mars, the planet (as we currently know it) doesn’t seem to want settlement.

It has almost no air, constantly experiences frightening cosmic radiation and boasts temperatures comparable to the coldest Antarctic winters.

Thus, it is rather doubtful that any life that may have once existed on Mars was able to leave behind traces easily visible today. Presumably, most of its fingerprints—molecules, viruses, or other bits—would simply disappear with the planet’s descent into habitability.

“There is no flowing water or significant water in the Martian atmosphere, so the cells and spores will dry out,” Hoffman said. “It is also known that the surface temperature of Mars is roughly similar to that of dry ice, so it is indeed deep frozen.”

This annotated image of Mars shows the area where water ice is near the surface.


The goal of the study by Hoffman, Daly and other researchers was to alleviate some of that skepticism. Or in other words, they asked: What is the realistic chance that our Mars expeditions will find evidence of extraterrestrial life?

To answer this question, the team first determined the relevant radiation survival limits of microbial life as a whole. They then exposed six species of Earth bacteria and fungi to a simulated Martian terrain and threw things like gamma rays and fast particles at the organisms to mimic the levels of cosmic radiation on the Martian surface.

In short, the researchers conclude that some terrestrial creatures could potentially survive in the harsh Martian climate for hundreds of millions of years.

Which brings us back to Conan the Bacteria.

Also known as Deinococcus radiodurans, the microbe nicknamed the Conan Bacteria seems particularly suited to the extreme conditions fostered by the team, surviving what the researchers call “astronomical amounts of radiation in a frozen, dry environment.”

But the likelihood of finding Martian life increases when we move things underground. Even for Conan.

Microscopic image of Conan the Bacteria.  It looks like a 2D, red-orange, mottled, sort of spherical spot on a yellow surface.

D. radiodurans (affectionately known as the Conan Bacteria) is particularly suited to survive in the harsh environment of Mars.

Michael Daly/USU

Inside the Martian underground culture

Part two of the team’s latest experiment involves exposing organisms to subsurface levels of radiation, as well as Deep subsurface radiation levels on Mars. As you might expect, the samples seem to show much greater resistance to survival in both cases when contrasted with full surface radiation.

Conan the Bacteria actually beat his previous record.

Previous studies found that this microbe survived 25,000 units of radiation when suspended in liquid, but testing Conan while dry, as the new study did, found that the microbe survived 140,000 units of radiation. That’s a whopping 28,000 times more than what would kill a human.

In terms of survival lengthhowever, these numbers suggest that Conan may have lived 10 centimeters below the surface of Mars for 1.5 million years and 10 meters below the surface for 280 million years.

The Martian landscape shows a layered rock face with a nearby small rock balanced on top of a larger rock.

A landscape on Mars shows a layered rock face with a nearby small rock balanced impressively on top of a larger rock.


And even more promising is the thought that Mars undergoes something like periodic melting and freezing over time, which would further help strong bacteria like Conan to thrive in a changing world.

“Although D. radiodurans buried in the Martian subsurface could not survive in a dormant state for the approximately 2 to 2.5 billion years since flowing water disappeared on Mars, such Martian environments are regularly altered and melted by meteorite impacts.” , Daly said. “We hypothesize that intermittent melting may allow periodic repopulation and dispersal.”

All in all, there’s a good chance that ancient Martian bacteria are just below the Martian surface and will soon be dug up by humans—carefully, of course. Otherwise, our pursuit of extraterrestrial life may accidentally leave a microbial footprint that creates a terrible butterfly effect across space and time.

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