Dark matter secrets could lie buried in ancient rocks on Earth

Fossil traces hidden deep underground may solve the mystery of dark matter, the elusive substance that makes up 80 per cent of the universe

Nick Hawkins/NaturePL

By Sebastian Baum

MOST of our universe is missing. Observations of the smallest galaxies to structures spanning the entire universe show that ordinary matter – the stuff that makes up you, me and everything we see in the cosmos around us – accounts for only one-fifth of all matter. The remaining 80 per cent is a mystery.

After decades trying to hunt down this “dark matter” with a series of ever-more-sophisticated detectors, we remain empty-handed. It is time for a new approach. Perhaps a combination of ancient minerals snatched from the bowels of the planet and modern nanotechnology will reveal the secrets of this elusive substance.

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We cannot see dark matter because it doesn’t interact with light. However, theoretical models provide clues about what it might be made of. The most compelling explanation is that it is made of particles, just like all the ordinary stuff around us. One of the most promising candidates is the WIMP, or weakly interacting massive particle, a hypothetical entity with a mass similar to that of a normal atomic nucleus.

If dark matter is made of WIMPs, then a litre of stuff – whether it is air, rock or seemingly nothing at all – should contain a few of these exotic particles, whizzing around at speeds of hundreds of kilometres per second.

Most of the time, these particles would fly right through anything in their way as if it weren’t there. But very rarely, they could bump into the atomic nucleus of this matter and give it a little kick.

For the past 30 years, a number …