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Minerals deep inside Earth might contain telltale traces of collisions with dark matter — the elusive stuff that researchers think makes up most of the matter in the Universe. Experiments designed to search for these traces could one day complement or even compete with ongoing efforts to detect dark matter directly.

Researchers using sophisticated detectors sunk deep underground have searched for signs of dark matter for decades. But now, Katherine Freese, a physicist at the University of Michigan in Ann Arbor, and her colleagues suggest that minerals such as halite (sodium chloride) and zabuyelite (lithium carbonate), can act as ready-made detectors1.

Astronomers can detect the gravitational influence of dark matter on the motion of galaxies and galactic clusters, but have never been able to spot it directly. The prevailing explanation for dark matter is that it’s made of material known as weakly interacting massive particles (WIMPs), which interact with normal matter mainly through gravity.

Direct-detection experiments aim to find the faint after-effects of WIMPs colliding with the nuclei of atoms in materials such as germanium, silicon or sodium iodide inside a detector.

Such experiments must be positioned deep underground, to guard against the cosmic rays that bombard Earth’s surface. These rays can also leave faint traces of their collisions with detector materials, which can swamp any potential signals from dark matter. So far, only one experiment — the DAMA/LIBRA experiment at the Gran Sasso National Laboratory in Italy — says it has detected dark matter, but the claim remains unverified.

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Category: Science