S African bacteria linked to life on Mars.

The discovery of bacteria living three kilometres down in a South African gold mine has sparked new speculation about the possibility of life below the surface of the planet Mars.

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The ancient bacteria were found at the bottom of Carletonville gold mine, some 80km west of Johannesburg. South African and American scientists say in a study published in the international Science journal that the microbes seem to have survived for tens of millions of years living on hydrogen and sulphate, and not oxygen.

Tullis Onstott, a geosciences professor at Princeton University and leader of the research team, says the bacteria are completely unknown, have no name or recognisable origin and live in conditions that are similar to those on Mars.

Reports Onstott: "If you look at Mars now, it is geographically inactive. It looks dead. We don't see volcanoes erupting and we don't see obvious signs of life. It's a dead planet. But it's tectonically active. We know what the rocks are like, we know there's water there and uranium radiation there."

In the depths of Carletonville mine, the bacteria live off the radioactivity from the surrounding rocks, 'breathing' chromium 6 like oxygen.

"There's no reason why a geologically inactive planet cannot still have a source of energy for an organism," says Onstott. "It's a new species and new genesis bacteria. Its closest relatives are things you find coming out of vents in the ocean floor. It could possibly be rooted deeply in the tree of life and could be quite ancient."