Friday, November 2, 2012

Hunting dark matter with DNA

Particle physicists propose a new way to detect dark matter using the molecule of life

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In a proposed method for detecting dark matter, particles of dark matter would smack into gold, kicking off atomic nuclei that would sever strands of DNA in their paths.

Credit: Dukier et al., diagram in arXiv preprint. (

RALEIGH, N.C. ? Physicists racing to detect the mysterious substance known as dark matter are thinking outside the box by looking inside the cell. A new proposal for tracking dark matter particles relies on strands of DNA.

All the ordinary stuff in the universe, from the atoms in people to the hot plasma in stars, makes up only about 5 percent of the universe?s mass and energy. About one-quarter of the universe?s composition is dark matter. (The rest is an even more puzzling entity known as dark energy.) Though several experiments claim to have detected dark matter, the results don?t agree and aren?t definitive.

Katherine Freese, a theoretical physicist at the University of Michigan in Ann Arbor, proposed October 28 at the New Horizons in Science meeting that a new kind of DNA-based detector could not only spot a leading candidate for dark matter, called WIMPs, but could also determine incoming particles? direction of flight. The proposal also appeared online earlier this year at

?It?s a very smart way to apply technology developed from biology to a fundamental particle physics problem,? says Jocelyn Monroe, a dark matter physicist at MIT and the University of London.

A halo of WIMPs, short for weakly interacting massive particles, is thought to encircle the galaxy. As the sun orbits the galaxy?s center, it should encounter a ?wind? of WIMPs from the direction of the constellation Cygnus. At any point on Earth, such a wind would strengthen and weaken daily as the planet rotated.

Freese and her colleagues? proposed detector, which would be sensitive to these fluctuations, consists of a stack of thin gold sheets with single strands of DNA hanging from them. When a WIMP smacked into the nucleus of a gold atom, the nucleus would whiz off, cutting through the DNA strands in specific locations. Scientists would then collect and sequence the DNA to reconstruct the path traveled by the nucleus, which provides the path of the WIMP. If the detector spotted the daily fluctuation and the particles? paths proved consistent with the Cygnus wind?s direction, it would be compelling evidence that the signals came from dark matter.

The DNA detector would have a spatial resolution about a thousand times better than current detectors.

?The advantage of these detectors is that the difference between DNA bases is a nanometer, so it?s much better resolution,? says Freese.

The device could be a fraction of the size of others, and cheaper, too.

Still, the technique hasn?t yet been demonstrated, says Joel Schnur, a biomolecular scientist at George Mason University in Fairfax, Va. ?What is the real sensitivity to cleavage of DNA? How many particles will come down over time? And, can it detect them?? he asks. Other technical challenges will also have to be overcome before the proposed detector could become a reality.

R. Cowen. Signs of dark matter from Minnesota mine. Science News, Vol.179, No. 12, June 4, 2011, p. 10. Available online: [Go to]

R. Cowen. XENON100 fails to find dark matter. Science News, Vol.179, No. 10, May 7, 2011, p. 12. Available online: [Go to]

N. Drake. Dark matter search turns up empty. Science News, Vol.181, No. 10, May 19, 2012, p. 5. Available online: [Go to]


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