Moscow - A microbe which is resistant to radiation may have come from Mars, Russian scientists say.
The researchers suggest the bug may have begun life on the red planet before being blasted to earth by an asteroid.
Deinococcus radiodurans can withstand a thousand times the dose of radiation that would kill a human being. To find out how this resistance was acquired, Anatoli Pavlov and his team from St Petersburg's Ioffe Physico-Technical decided to blast another microbe, E.coli, with gamma rays, according to New Scientist magazine.
The bugs were exposed to enough radiation to kill 99,9 percent of them and the remainder were left to recover before being exposed to an increased dose.
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'It's certainly a mystery how this trait has developed and why it persists' After 44 cycles it took 50 times the initial dose to kill the same proportion of the bugs, but the researchers found it would take thousands more cycles for E.coli to build up the same level of resistance as Deinococcus.
On earth, that could take up to 100 million years, but on Mars the bugs could receive the same exposure in only a few hundred thousand years. This led the researchers to speculate that the bugs evolved on Mars before being knocked into space by an asteroid and falling to earth in meteorites.
However, Nasa astrobiologist David Morrison said it was unlikely the bug came from Mars, as its genome was very similar to other Earthly bacteria. Nonetheless he could not explain why Deinococcus was so resistant to radiation.
"It's certainly a mystery how this trait has developed and why it persists," he told New Scientist. - Sapa-DPA
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