Sorry, space tourists: Mars is less habitable than we hoped

I have bad news for you if you're a bacteria trying to survive on the surface of Mars. Scottish astrobiologists have discovered that the Red Planet is rather more hostile to life than we initially believed.

Jennifer Wadsworth and Charles Cockell from the University of Edinburgh's School of Physics and Astronomy have published a new study showing that salt minerals called perchlorates kill bacteria within minutes under conditions similar to those on the Martian surface.

Normally, perchlorates are stable at room temperatures - only becoming active at high heat. As such, the perchlorates found on Mars by Nasa's Phoenix Lander in 2008 were assumed to be inactive, as the surface of the planet is so cold.

But Wadsworth and Cockrell found that perchlorates can also be activated by ultraviolet (UV) light, without heat at all. That's a problem because Mars, which lacks Earth's protective ozone layer, is constantly bombarded by UV radiation.

Other life forms

The pair emphasised that they had only tested the effect of perchlorates and UV on one species of bacteria - B. subtilis. Further tests will need to be done to see whether the same effects would occur with other life forms.

But on the bright side, it means that the bacteria carried to Mars on robotic probes (of which B. subtilis is common) are unlikely to have survived for very long and been able to contaminate the environment.

"If we want to find life on Mars, we have to take this into consideration and look at trying to find sub-surface life that wouldn't be exposed to these conditions," Wadsworth told AFP.

The details of the discovery were published in the journal Scientific Reports.