(CNN) – Ancient bacteria could be sleeping under the surface of Marswhere they have been shielded from the harsh radiation of space for millions of years, according to new research.
While no evidence of life has been found on the red planet, researchers simulated conditions on Mars in a laboratory to see how bacteria and fungi might survive. Scientists were surprised to discover that bacteria could probably survive for 280 million years if they were buried and protected from ionizing radiation and solar particles that bombard the Martian surface.
The findings suggested that if life ever existed on Mars, latent evidence of it could still be located in the subsurface of the planeta place that future missions could explore as they drill into the Martian soil.
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While Mars was probably a more hospitable environment for life billions of years ago, including an atmosphere and water on its surface, today the red planet looks more like a frozen desert. The arid mid-latitudes of the planet have an average temperature of minus 62 degrees Celsius. And then there is the constant threat of radiation because Mars has a very thin atmosphere.
“There is no flowing water or significant water in the Martian atmosphere, so the cells and spores would dry out.”said study co-author Brian Hoffman, the Charles E. and Emma H. Morrison Professor of Chemistry and professor of molecular biosciences at Northwestern University’s Weinberg College. of Arts and Sciences, in a statement. “It is also known that the surface temperature of Mars is more or less similar to that of dry ice, so it is, in fact, deeply frozen.”
A research team determined the survival limits of microbial life when exposed to ionizing radiation such as might be experienced on Mars. The team then introduced six types of bacteria and fungi found in the Earth in a simulated Martian surface environmentall while blasting them away with protons or gamma rays to mimic space radiation.
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A clear winner emerged called Deinococcus radiodurans. The microbe, nicknamed “Conan the Bacterium” due to its hardy nature, it seemed perfectly suited for life on Mars.
The bacterium is polyextremophilous, which means that it can survive harsh conditions such as dehydration, acid, and low temperatures. The hardy microbe is one of the most radiation-resistant organisms known to science.
This is what Conan the Bacterium looks like growing on a nutrient agar plate. Credit: Northwestern University.
Previous research has found that the bacteria could survive 1.2 million years just below the surface of Mars amid strong radiation and a dry, frozen environment, and survive some microorganisms that are known to survive on Earth for millions of years.
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The new study determined that when Conan the Bacterium dries up, freezes and buries itself deep below the Martian surface, could survive 140,000 units of radiation28,000 times more than the level of radiation exposure that could kill a human.
The bacterium, which resembles a pumpkin when viewed under a microscope, would likely survive only a few hours on the Martian surface after relentless exposure to ultraviolet light. Conan the Bacterium’s expected survival increased to 1.5 million years just 10 centimeters below the surface, and around 280 million years if the bacterium was 10 meters deep.
Magazine Astrobiology published a study detailing the findings on Tuesday.
The researchers were able to measure how much manganese antioxidants accumulated in the cells of the microorganisms when they were exposed to radiation.n. The more manganese antioxidants the team found, the more likely the microbe could withstand radiation and survive..
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Conan the Bacterium’s genomic structure links chromosomes and plasmids, meaning cells stay aligned and can repair themselves after radiation exposure. And if a Conan-like microbe evolved on Mars billions of years ago, when water still existed on the Martian surface, the dormant remains of the bacterium could be sleeping deep in the subsoil of the planet.
“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 Marssuch Martian environments are regularly altered and melted by meteorite impactsstudy author Michael Daly, a professor of pathology at the Uniformed Services University of Health Sciences and a member of the Planetary Protection Committee of the National Academies, said in a statement.
“We suggest that periodic melting could allow intermittent repopulation and dispersal. Furthermore, if Martian life ever existed, even if there are no viable life forms on Mars now, its macromolecules and viruses would survive much, much longer. That strengthens the probability that if life ever evolved on Marsthis will be revealed in future missions.”
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The findings have implications for both returning Martian samples to Earth and to land manned missions on Mars.
The Mars Sample Return program, an ambitious program run jointly by NASA and the European Space Agency, will launch multiple missions to Mars to collect and return samples that were collected by the Perseverance rover.
The rover team hopes that the rock and soil samples, taken from the site of an ancient lake and river delta in Mars’ Jezero Crater, can determine whether life ever existed on the Red Planet. The samples could even contain microfossils of ancient microbial life.
Additionally, astronauts have the potential to accidentally deliver bacteria that they hitchhike from Earth when they land on Mars.
“We concluded that terrestrial contamination on Mars would be essentially permanent, over time periods of thousands of years,” Hoffman said. “This could complicate scientific efforts to search for Martian life. Likewise, if microbes evolved on Mars, they might be able to survive to the present day. That means returning samples from Mars could contaminate Earth.”