Tests conducted by the University of Ediburgh on the habitability of the surface of Mars has shown that the environment is more hostile to life as we know it on Earth than previously believed. The tests checked the effect of perchlorates, chlorine based compounds, on micro-organisms. After simulating conditions on Mars, the research showed that the UV light in the thin atmosphere of Mars heated up the perchlorates, making them more poisonous to microorganisms typically found in spacecraft, as well as the surface of Earth.
The tests showed that chemicals commonly found on the surface of the red planet, including iron oxides and hydrogen peroxide compounded the harmful effects of perchlorates alone. In tests conducted with all three chemicals present, there was a ten fold increase in the death of bacterial cells compared to tests conducted with only perchlorates. Jennifer Wadsworth, from the UK Centre for Astrobiology and School of Physics and Astronomy says "Our findings have important implications for the possible contamination of Mars with bacteria and other materials from space missions. This should be taken into account in designing missions to Mars."
According to a report published in Popular Science, the finding does not rule out the possibility of life on Mars. A commonly held belief is that it will be necessary to dig deep into the surface to find microbial life. The tests were conducted using bacteria that were not extremophiles, or organisms that can survive in extreme environments that are normally toxic to other living things. This leaves the possibility that Mars can be contaminated by especially hardy organisms from Earth that make the jump through space probes. Space agencies will continue to have to carefully sterlise any craft that they send to Mars, to prevent potential contamination, and the introduction of foreign species.