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Drilling for Martians

New Scientist

NASA plans to burn holes in the red planet

ENGINEERS have developed a new tool to help them hunt for signs of life on Mars. Their metre-long, white-hot spear can melt its way through soil and rocks to depths where evidence of past life may be lurking.

If life ever existed on Mars, harsh conditions on the surface could mean the only remaining traces may be buried more than a kilometre down. But conventional drilling is unlikely to unearth them. "The soil is a mixture of sand, dust and rocks cemented together with salt minerals," says John Bridges, who studies Martian geology at London's Natural History Museum. "For the most part, it'll be like digging in a sandpit."

Holes bored in the ground are likely to collapse, says Geoff Briggs, scientific director of NASA's Center for Mars Exploration at the Ames Research Center in California. So Briggs and his colleagues developed a drill bit that reinforces the holes as it goes. Its tip heats up to 1500 °C, while the shaft of the drill is cooled by pumping gas from the cold Martian atmosphere into the rear of the spear.

"The tip melts pretty much any type of rock," says Briggs. As it pushes through the ground, it forces molten rock into the surrounding porous soil where it turns to glass, locking the surrounding soil in place. "The main advantage of this system is that it produces a self-supporting hole," says Briggs.

His drill bit is not heavy enough to sink through molten soil, so it is connected to a reel of metal tubing on the surface. Unwinding the tubing-which carries the drill's power and coolant cables-pushes the drill bit through the soil. In tests at the Los Alamos National Laboratory in New Mexico, the drill went through 30 metres of basalt with no difficulty.

Bridges points out that heat from the drill bit would be likely to destroy any traces of life it encounters. "If you were going to look for enrichment of carbon-12 that might have been caused by life, you'd have problems at this temperature," he says. But Briggs points out that after the hole has been bored, other tools can be lowered into it to dig around the bottom and retrieve soil samples unaffected by the heat. However, great care will be needed. Colin Pillinger of the Open University in Milton Keynes, who is leading the Beagle 2 Mars lander programme scheduled for 2003, warns: "If organic residues produced by organisms are brought up to the surface, they'll be converted to carbon dioxide immediately."

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Author: Ian Sample

New Scientist issue: 13th January 2001

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