Mars seems earthlike in numerous ways, but it’s still a rugged environment for life. A team of scientists led by A. P. Johnson (Indiana University) examined just how rough Mars is for several terrestrial organisms and amino acids by subjecting them to Martian conditions. Publishing in the February 2011 issue of Icarus, the researchers found that Mars is most hostile to Earth life in two ways: dehydration and oxydation.
Surprisingly, they found that ultraviolet radiation, extreme temperatures, and reactive gases in the atmosphere — the Martian conditions usually fingered as being hardest on terrestrial organisms — all did comparatively little damage to the samples. This result leads the team to warn that spacecraft sent to Mars should probably not use dry heat and hydrogen peroxide (the commonest methods) as sterilizing agents.
The reason? These methods just aren’t deadly enough to kill off those terrestrial organisms that have the best chances of surviving under Martian conditions.