Find liquid water on Mars, and life may not be far behind. Many scientists believe that this water can only exist thousands of metres beneath the planet's surface. So a team of engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, is developing a robotic mole that can drill deep into Mars and return samples to the surface through a tube that it constructs as it digs.
JPL's Martian mole moves through the ground like a piledriver, repeatedly raising an internal weight and then hammering it into the ground. On Mars it will be wired up to a set of solar panels on the surface that provide only enough power to illuminate a few light bulbs. So the designers had to make a machine that could penetrate the ground using only this meagre power.
The design JPL came up with has a hammer head that spins at up to 20,000 revolutions per minute before engaging a central thread that drives it into the ground. This delivers roughly twice the force of a sledgehammer blow on Earth, and enables the mole to burrow at up to 10 metres per day.
As it digs, the mole extrudes a tiny tube containing two passageways which provide a link to the surface and back. Liquid xenon circulating through these tubes will carry samples that can be sieved and analysed on the surface.
One possible target for the mission is a potential aquifer that many scientists believe may exist about 5 kilometres down near the Martian equator, says Brian Wilcox, the project leader. Another option is to aim for one of the planet's polar ice caps and study Mars's climate history over the past few million years by examining ice samples.
The group has already built a prototype of the hammer mechanism and is now planning the tube extruder. In 2002, Wilcox plans to test the complete system in the Alaskan permafrost. He says his team could be ready to tackle Mars within a decade.
"Drilling may well be the only way we can get to places that have a chance of having life on Mars today," says Michael Carr, a geologist at the US Geological Survey who is reviewing NASA's Mars programme.
Author: Mark Schrope
New Scientist issue: 16th September 2000
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