Life on Mars: Ancient Bacteria Might Lurk Beneath Mars’ Surface

Deinococcus radiodurans (affectionately known as “Conan the Bacterium”) is particularly well-suited to surviving Mars’ harsh environment. In experiments, it survived astronomical amounts of radiation in the freezing, arid environment. Credit: Michael J. Daly/USU

A new study finds the chances of uncovering life on Mars are better than previously expected.

  • Researchers simulated Mars’ harsh ionizing radiation conditions to see how long dried, frozen bacteria and fungi could survive.
  • Previous studies found ‘Conan the Bacterium’ (Deinococcus radiodurans) could survive over a million years in Mars’ harsh ionizing radiation.
  • A new study shatters that record, finding the hearty bacterium could survive 280 million years if buried.
  • This means evidence of life could still be dormant and buried below Mars’ surface.
Researchers should be on the lookout for ancient sleeping bacteria when the first samples from Mars are brought back to Earth, according to the results of a recent research.
In a groundbreaking investigation, a group of scientists discovered that ancient microorganisms might survive considerably longer than previously thought near to the surface on Mars. The bacteria can also endure much longer when they are buried because they are protected from solar protons and galactic cosmic radiation.
These results increase the likelihood that, if life ever evolved on Mars, its biological remains could be found by upcoming expeditions. ExoMars (the Rosalind Franklin rover) and the Mars Life Explorer are two of the next missions that will include drills to retrieve minerals from two meters into the surface.
Scientists have demonstrated that some kinds of bacteria may live in Mars’ hostile atmosphere. This implies that future humans and space travelers may unintentionally bring their own microbes to Mars.
The paper will be published today (October 25) in the journal Astrobiology. The research team included Northwestern University’s Brian Hoffman and Ajay Sharma.

Deinococcus radiodurans (affectionately known as “Conan the Bacterium”) is particularly well-suited to surviving Mars’ harsh environment. In experiments, it survived astronomical amounts of radiation in the freezing, arid environment. Credit: Michael J. Daly/USU

“Our model organisms serve as proxies for both forward contamination of Mars, as well as backward contamination of Earth, both of which should be avoided,” said Michael Daly, a professor of pathology at Uniformed Services University of the Health Sciences (USU) and member of the National Academies’ Committee on Planetary Protection, who led the study. “Importantly, these findings have biodefense implications, too, because the threat of biological agents, such as Anthrax, remains a concern to military and homeland defense.”
“We concluded that terrestrial contamination on Mars would essentially be permanent — over timeframes of thousands of years,” said Hoffman, a senior co-author of the study. “This could complicate scientific efforts to look for Martian life. Likewise, if microbes evolved on Mars, they could be capable of surviving until present day. That means returning Mars samples could contaminate Earth.”

Simulating Mars

The environment on Mars is severe and brutal. The Red Planet appears to be uninhabitable to life due to the dry and icy temperatures, which average -80 degrees Fahrenheit (-63 degrees Celsius) at mid-latitudes. Even worse: Protons from the sun and powerful galactic cosmic radiation are also continuously bombarding Mars.
The ionizing radiation survival limitations of microbial life were first established by Daly, Hoffman, and their collaborators in order to investigate whether or not life could endure in these circumstances. Then, they exposed six different kinds of Earthly bacteria and fungi to a dry, frozen simulation of Mars’ surface and blasted them with protons or gamma rays (to mimic radiation in space).
“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.”
In the end, the scientists came to the conclusion that some terrestrial microorganisms would be able to endure on Mars for geologic epochs of hundreds of millions of years. In fact, the researchers found that one particular hardy microbe, Deinococcus radiodurans, or “Conan the Bacterium,” is especially well-suited to surviving the severe conditions on Mars. Conan the Bacterium outlasted Bacillus spores, which may live on Earth for millions of years, by surviving huge quantities of radiation in the frigid, arid environment.

Radical radiation

The scientists exposed samples to high doses of gamma radiation and protons, which are typical of what Mars experiences in the immediate subsurface, as well as much lower doses, which would happen if a microbe was deeply underground, to investigate the impacts of radiation.
The concentration of manganese antioxidants in the cells of the exposed bacteria was then measured by Hoffman’s team at Northwestern using a sophisticated spectroscopic technique. Hoffman found a correlation between the amount of manganese antioxidants a microbe or its spores carry and the size of the radiation dosage it can sustain. Therefore, having more manganese antioxidants increases radiation resistance and improves lifespan.
In prior research, scientists discovered that Conan the Bacterium can withstand 25,000 units of radiation (or “grays”), or the equivalent of nearly 1.2 million years just below Mars’ surface, while held in liquid. However, the latest study discovered that the resilient bacterium could withstand 140,000 grays of radiation when it was dried, frozen, and deeply buried—conditions that would be characteristic of a Martian climate. The human lethal dose is 28,000 times higher than this one.
The lifespan of Conan the Bacterium increases noticeably whether it is shaded or situated directly beneath Mars’ surface, despite the fact that it could only endure a few hours at the surface while drenched in ultraviolet light. Conan the Bacterium has a 1.5 million year lifespan when buried at 10 centimeters below the Martian surface. Additionally, the orange-colored bacterium might live 280 million years if buried 10 meters below the surface.

Looking to future missions

The researchers discovered that the bacterium’s genomic structure is partially responsible for this astounding survival achievement. Long suspected, the researchers found that the chromosomes and plasmids of Conan the Bacterium are linked together, maintaining their perfect alignment and preparing them for repair following strong radiation.
This implies that any microorganism, comparable to Conan the Bacterium, that existed when water last flowed on Mars could still be hibernating in the deep subsurface.
“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. Also, if Martian life ever existed, even if viable lifeforms are not now present on Mars, their macromolecules and viruses would survive much, much longer. That strengthens the probability that, if life ever evolved on Mars, this will be revealed in future missions.”


by: Miss Cherry May Timbol – Independent Reporter
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