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NEWS
Ancient bacteria could persist beneath Mars’ surface
MICROBES
Ancient bacteria could persist beneath Mars’ surface
Radiation-tolerant microbes might survive there for hundreds of millions of years
Radiation-tolerant bacteria similar to this Deinococcus radiodurans would be particularly well-suited to surviving Mars’ harsh,
freezing environment, a new study suggests.
MICHAEL J. DALY/USU
By Sid Perkins
NOVEMBER 2, 2022 AT 9:00 AM
Radiation-tolerant microbes might be able to live beneath Mars’ surface for hundreds
of millions of years and may yet persist today, thanks in part — counterintuitively — to
the Red Planet’s frigid, arid conditions.
In addition to being cold and dry, the Martian surface is constantly bombarded by
cosmic rays, charged particles and other radiation from space. Previous studies have
shown that desiccation vastly extends a microbe’s potential for surviving by limiting
the production of highly reactive oxygen-bearing chemicals that can damage proteins
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Ancient bacteria could persist beneath Mars’ surface
and DNA, among other vital molecules within its tissues. To see how long microbes
might survive such an onslaught on Mars, researchers desiccated five species of
bacteria and one type of yeast, stored them at −80° Celsius and then irradiated them.
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Some of the microbes might remain viable for only a few tens of thousands of years,
experiments showed. But one species — Deinococcus radiodurans, a particularly
radiation-hardy greebly that some scientists have nicknamed “Conan the bacterium”
— might survive for as long as 280 million years if protected from radiation at soil
depths of 10 meters or more, physical chemist Brian Hoffman and colleagues report
online October 25 in Astrobiology.
D. radiodurans resists radiation damage by having multiple copies of chromosomes
and other genetic material in each cell, as well as high levels of manganese-bearing
antioxidants that help remove DNA-damaging chemicals (SN: 9/3/10). If similar
microbes evolved on Mars, they too could persist for lengthy intervals, even possibly
until now — which is “improbable but not impossible,” says Hoffman, of Northwestern
University in Evanston, Ill.
Even if microbes that evolved on Mars ultimately succumbed to the harsh conditions,
remnants of their proteins or other macromolecules may remain — offering hope that
future missions, if equipped with the proper equipment, might be able to detect those
signs of former life.
CITATIONS
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Ancient bacteria could persist beneath Mars’ surface
W.H. Horne et al. Effects of desiccation and freezing on microbial ionizing radiation survivability: Considerations for Mars sample
return. Astrobiology. Published online October 25, 2022. doi: 10.1089/ast.2022.0065.
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