Gas gives new clue to life on Mars

Scientists which could be a sign of life on the red planet.

Massive telescopes in Hawaii and Chile have been used to detect methane, which can only survive a short time. The scientists believe there are only two possible explanations - the gas comes from active volcanoes or microbes.

So far volcanoes have not been found, fuelling theories that this is the latest evidence of primitive-life on the planet. The findings have been supported by instruments on the European Space Agency's orbiting Mars Express craft.

Both explanations for the existence of methane represent major leaps in scientists' understanding of Mars. The failure of the various spacecraft orbiting Mars to find volcanic hotspots throws up the possibility the gas is due to life. On earth, bacteria produce methane from hydrogen and carbon dioxide. Terrestrial microbes that produce the gas do not need oxygen to thrive.