They are among the Earth's toughest organisms, but can they survive in a moon of Mars?

The LIFE project of the Planetary Society of Pasadena, Calif., which was launched in a rocket together with a Russian spacecraft, brings with it some of the Earth's toughest organisms that can survive extreme temperatures and the vacuum of space in low-Earth orbit.

The bacterium Deinococcus radiodurans and water bears - tiny invertebrates that can survive extreme temperatures and the vacuum of space in low-Earth orbit, are only two of the 10 living organisms that will be sent to the Martian moon Phobos as part of the Living Interplanetary Flight Experiment.

The other organisms are Bacillus subtilis, Saccharomyces cerevisiae Strain, Arabidopsis thaliana, Haloarcula marismortui, Pyrococcus furiosus, Methanothermobacter wolfeii and an arid soil sample from the Negev desert in Israel.

The guidelines that governed the selection of the organisms include: the organisms selected would represent the three domains of life - eukaryotea, bacteria, and archaea; that organisms should be very well studied to make it possible to accurately assess the effects of the long exposure to space and, finally, a strong preference was given to organisms that appear to stand the best chance of surviving the journey.

The project will test an idea called transpermia, in which organisms "could be ejected off one planet in impacts, travel through space inside rocks, then be deposited on another world," said Bruce Betts, LIFE's lead scientist.

If the organisms survive the three-year period, it would strengthen the idea that life on Earth might have come from other planets, or has travelled to other planets, he added.

LIFE has stirred up questions on what will happen if the mission crashes and the microbes are allowed to get loose. Catharine Conley, NASA's planetary protection officer, who is charged with ensuring that agency projects do not contaminate other solar system bodies with terrestrial life gave the assurance that the risk of contaminating Mars is "extremely slim."

Pascal Lee of the Mars Institute explained that to cause contamination, the LIFE capsule would have to miss Phobos, enter the Mars's fiery atmosphere and open up on the surface. And the organisms should not be able to survive the barrage of ultraviolet solar radiation. In any case, these organisms would not be able to reproduce, the scientist said.