They also warn that future Martian expeditions run the risk of tainting the red planet -- permanently.
Over the next decade, several space agencies plan on bringing Martian rock back to Earth for the very first time -- and, according to a new study published Tuesday in the journal Astrobiology, whoever gets to analyze those seminal samples might stumble on something incredible: proof of alien life.
Basically, a crew of researchers says that if organisms really did live on Mars long ago, when it was a watery oasis, a bunch 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 suggest that any organisms buried beneath the ground would've survived the longest, and therefore, believe those beings' remains could still be lying under Martian soil. So as upcoming missions, such as ExoMars by Roscosmos and the European Space Agency, are poised to extract sediment from beneath the Martian ground,perhaps we're soon to see some groundbreaking extraterrestrial evidence.
"If Martian life ever existed, even if viable lifeforms are not now present on Mars, their macromolecules and viruses would survive much, much longer," Michael Daly, a pathologist at Uniformed Services University of the Health Sciences and lead author of the study, said in a statement. "That strengthens the probability that, if life ever evolved on Mars, this will be revealed in future missions."
And in fact, thanks to Daly's experimental simulations, we may already know the name of the little organism (or at least its sibling) waiting to be forensically dug up on Mars: Conan -- Conan the Bacterium, that is.
But more on Conan in a bit.
Also, as an important side note, the team's findings emphasize how all future Mars missions ought to practice extreme caution. In a nutshell, viewing the experimental results in reverse leads to the knowledge that if we contaminate Mars with Earthling bacteria somehow, maybe from astronaut boots or scientific equipment, those transmitted microbes won't just die. They could survive on the pristine planet for an excruciatingly long time.
"We concluded that terrestrial contamination on Mars would essentially be permanent -- over time frames of thousands of years," Brian Hoffman, a chemist at Northwestern University and co-author of the study, said in a statement. "This could complicate scientific efforts to look for Martian life."
"Likewise," he continues, "if microbes evolved on Mars, they could be capable of surviving until present day. That means returning Mars samples could contaminate Earth."
Time to blast organisms with extreme radiation
Despite humanity's budding excitement about the idea of settling Mars, the planet (as we know it right now) doesn't seem to want settling.
It pretty much has no air, is constantly experiencing zaps of frightening cosmic radiation and boasts temperatures comparable to the coldest Antarctic winters.
Thus, it's rather doubtful whether any life that may have existed on Mars once upon a time managed to leave behind traces of itself easily visible today. Presumably, the bulk of its fingerprints -- molecules, viruses or other bits and pieces -- would've simply vanished alongside the planet's descent into inhabitability.
"There is no flowing water or significant water in the Martian atmosphere, so cells and spores would dry out," Hoffman said. "It also is known that the surface temperature on Mars is roughly similar to dry ice, so it is indeed deeply frozen."
This annotated image of Mars shows the area where water ice is close to the surface.
The goal of Hoffman, Daly and fellow researchers' study was to ease 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 that question, the team first determined the relevant radiation survival limits of microbial life in general. Then, they exposed six types of Earthling bacteria and fungi to simulated Martian terrain and threw things like gamma rays and zippy particles at the organisms to mimic cosmic radiation levels on Mars' surface.
In short, the researchers concluded that some surface-based beings could potentially survive in Mars' harsh climate for hundreds of millions of years.
Which brings us back to Conan the Bacterium.
Also known as Deinococcus radiodurans, the microbe nicknamed Conan the Bacterium appeared particularly well suited to the extreme conditions fostered by the team, surviving what the researchers call "astronomical amounts of radiation in the freezing, arid environment."
But the probability of finding Martian life shoots way up when we take things underground. Even for Conan.
D. radiodurans (affectionately known as Conan the Bacterium) is particularly well-suited to surviving Mars' harsh environment. Michael Daly/USU
Inside the Martian underground culture
Part two of the team's latest experiment involved exposing organisms to subsurface radiation levels as well as deep underground radiation levels on Mars. As you might expect, the samples appeared to exhibit much greater survival strength in both cases when contrasted with full-on surface radiation.
Conan the Bacterium actually beat its previous record.
Previous studies found this microbe to survive 25,000 units of radiation when suspended in liquid, but testing Conan while dry, as the new study did, found the microbe to withstand 140,000 units of radiation. That's a whopping 28,000 times greater than what would kill a human.
In terms of survival length, however, those numbers suggest Conan could've lived 10 centimeters below the Martian surface for 1.5 million years, and 10 meters below the surface for 280 million years.
A Mars landscape shows a layered cliff face with a nearby small rock balanced impressively atop a larger rock. NASA/JPL-Caltech/ASU
And even more promising is the thought of Mars going through a sort of on-and-off melting and freezing over time, which would further help strong bacteria like Conan thrive on the changing world.
"Although D. radiodurans buried in the Martian subsurface could not survive dormant for the estimated 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 suggest that periodic melting could allow intermittent repopulation and dispersal."
All in all, there's a fair chance of ancient Martian bacteria being right under the Martian surface, soon to be dug up by humans – carefully, of course. Otherwise, our pursuit of alien life may accidentally leave a microbial footprint that casts a terrible butterfly effect across space and time.
First published on Oct. 25, 2022 at 7:12 a.m. PT.
