The surface of Mars contains a toxic cocktail of chemicals that can wipe out living organisms, according to a study that has dealt a blow to the hopes of finding alien life on the red planet.

Researchers at the University of Edinburgh in the UK investigated the behaviour of chemical compounds, called perchlorates, which are found on the surface of Mars.

They found that, when exposed to ultraviolet (UV) light in environmental conditions mimicking those on Mars, the chemicals can kill bacteria commonly carried by spacecraft.

“Our findings have important implications for the possible contamination of Mars with bacteria and other materials from space missions,” said Jennifer Wadsworth from Edinburgh's School of Physics and Astronomy.

“This should be taken into account in designing missions to Mars,” said Wadsworth.

The study also suggests that the effect of perchlorates can be compounded by two other types of chemicals found on Mars' surface, iron oxides and hydrogen peroxide.

In experiments in which all three were present, the combination led to a more than 10-fold increase in death of bacterial cells compared with perchlorates alone.

Scientists have speculated on the influence that perchlorates may have on the habitability of the planet, since their discovery there several years ago.

Researchers investigated the potential reactivity of perchlorates and their effect on Bacillus subtilis, a bacterium found on spacecraft and common in soils and rocks.

Their experiments showed that when magnesium perchlorate was exposed to UV radiation similar to that on Mars, it became capable of killing bacteria much more effectively than UV light alone.

At concentrations of perchlorate similar to those found on the Martian surface, cells of B subtilis quickly died.

Although the Martian surface has been suspected for some time to have toxic effects, the latest study suggests that it may be highly damaging to living cells.

This is owing to a toxic mix of oxidants, iron oxides, perchlorates and UV energy, researchers said.

The study was published in the journal Scientific Reports.