As reported by Tech Times, research conducted aboard the ISS has shown that Earth bacteria
could survive the rigors of travel to Mars better than might be expected
"Research into bacterial colonization on the red planet was not part of the plan to terraform the alien world ahead of human occupation. Instead, three teams investigated how to prevent microbes from Earth from hitching a ride to the red planet aboard spacecraft. It is nearly impossible to remove all biological contaminants from equipment headed to other planets. By better understanding what organisms can survive in space or on the surfaces of other worlds, mission planners can learn which forms of microscopic life to concentrate on during the sanitation process. 'If you are able to reduce the numbers to acceptable levels, a proxy for cleanliness, the assumption is that the life forms will not survive under harsh space conditions,' Kasthuri Venkateswaran of the Jet Propulsion Laboratory and co-author of all three papers, said."