Bacteria could survive in Martian soil for millions of years
Article by: Andacs Robert Eugen, on 05 November 2022, at 09:15 am Los Angeles time
New research suggests that signs of ancient Martian life could be there - or rather, hidden just beneath the Martian surface, sheltered from harmful radiation, allowing them to survive for up to 280 million years.
The discovery gives researchers renewed hope that traces of ancient life - or even organisms in a vegetative state - could one day be found on the Red Planet.
In the study, the scientists found that a terrestrial bacterium, Deinococcus radiodurans, is so resistant to radiation that it can withstand the equivalent of 280 million years of radiation present 10 meters below the Martian surface.
The tiny microorganism that was found thriving in nuclear reactors on Earth could survive as long as 1.5 million years on the Martian surface, constantly bombarded by cosmic and solar radiation.
The secret is the very dry and cold environment of Mars. When the temperature is minus 79 degrees Celsius, D. radiodurans "becomes a phenomenal, astronomically radiation-resistant bacterium," said the study's lead author, Michael Daly, a geneticist and radiation biology expert at the Uniformed Services University in Maryland.
D. radiodurans is an organism long known to be a champion of radiation resistance. It is found in the human gut and many other places on Earth and has even survived for years in the vacuum of space.
However, the new research is the first attempt to test the upper limit of the bacteria's resistance to radiation when it is in a dehydrated state. Scientists had previously discovered that the bacterium can withstand a large amount of radiation when in liquid culture, Daly told Live Science.
The researchers placed the bacteria in a dry environment, then froze it and "bombarded" it with both gamma and solar-mimicking radiation. In this context, D. radiodurans could survive an amazing amount of radiation.
D. radiodurans evolved on Earth, where the atmosphere protects the planet and its organisms from the worst radiation. Any Martian bacteria would have had to evolve in an environment without this protection and probably would have had to develop a similar resistance to radiation, Hoffman said.
Mars hasn't had large-scale liquid water for 2 billion years, so that's still too little time to suggest the planet is home to a multitude of bacteria just waiting to come back to life. But because Mars has a very thin atmosphere, the planet's surface is regularly showered with meteorites, Daly said.
The heat and liquid water released by these impacts could awaken dormant bacteria underground and allow life to temporarily flourish.
Even if this temporary oasis theory isn't true, the long-lived potential of bacteria on Mars means that bits of ancient life could still be present as traces in the rocks, Hoffman said. DNA and other signs of life could exist as fragments, even if the organisms are long dead.