Steve
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Deinococcus radiodurans is not from Mars?

Deinococcus radiodurans is a species of bacterium which appeared to be so well adapted to life on the surface of Mars that a number of scientists seriously suggested that it could have evolved on Mars rather than the Earth.  Now its place in a group of Earth bacteria is more established, this theory may need to be re-examined.

Radiation Resistance

Deinococcus radiodurans can survive, and even grow actively, at radiation levels which would kill most organisms.  Its radiation resistance is higher than that of any other organism so far discovered. The surface of Mars gets much more radiation than that of the Earth; this bacterium would not be worried by even the peaks of radiation hitting Mars.

Relatives of Deinococcus radiodurans can also survive high doses of radiation.  Deinococcus geothermalis sometimes makes a nuisance of itself by living in nuclear reactors.

Extremophile

Organisms that can survive under extreme conditions that would kill most things are called extremophiles.  Deinococcus radiodurans certainly qualifies because of its extreme resistance toradiation.

Polyextremophile

A polyextremophile is an organism that can survive more than one extreme condition.  Apart from radiation, Deinococcus radiodurans can survive under extreme conditions of dryness, ultraviolet light and strong oxidising agents like peroxides.

Martian Conditions

The things this bacterium can survive are exactly the things a Martian organism would need to survive, so the theory that they came from Mars is understandable.  However, although there is now some evidence that they are an Earth organism, if they are eventually found on Mars, the theory will need to be reconsidered.

NASA goes to a lot of trouble to sterilise its spacecraft, but this bacterium is hard to kill. It could easily have hitched a ride on an American or Russian spacecraft that landed on Mars. 
There are several other ways it could get to Mars from the Earth, or from Mars to the Earth.

I will be interested to see what is found on Mars.



 
 
Transmission electron microgragh (TEM) of
Deinococcus radiodurans
Acquired in the laboratory of Michael Daly,
Uniformed Services University, Bethesda, MD, USA