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. 鈥淭he soil is a mixture of sand, dust and
rocks cemented together with salt minerals,鈥� says John Bridges, who studies
Martian geology at London鈥檚 Natural History Museum. 鈥淔or the most part, it鈥檒l be
like digging in a sandpit.鈥�
Holes bored in the ground are likely to collapse, says Geoff Briggs,
scientific director of NASA鈥檚 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 掳C, while the
shaft of the drill is cooled by pumping gas from the cold Martian atmosphere
into the rear of the spear.
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鈥淭he tip melts pretty much any type of rock,鈥� 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. 鈥淭he main advantage of
this system is that it produces a self-supporting hole,鈥� 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鈥攚hich carries the drill鈥檚 power and coolant cables鈥攑ushes 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. 鈥淚f you were going to look for enrichment of
carbon-12 that might have been caused by life, you鈥檇 have problems at this
temperature,鈥� 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: 鈥淚f organic residues produced
by organisms are brought up to the surface, they鈥檒l be converted to carbon
dioxide immediately.鈥�
