The harsh conditions that now exist on the surface of the planet mean that any remaining traces of life will be far beneath the surface, and Martian soil is too unstable for conventional drills. Holes bored the usual way are likely to collapse. “The soil is a mixture of sand, dust and rocks cemented together with salt minerals,” says John Bridges, who studies Martian geology at the Natural History Museum in London. “For the most part, it’s like digging in a sandpit.”

Now engineers have developed a long, hot spear that can melt through Martian soil and rocks to depths where they hope to find evidence of past life on Mars.
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