An illustration of the Alpha Magnetic Spectrometer, which is two years into what may be a 10-year voyage.

NASA via Associated Press file ,

A cosmic ray detector on the International Space Station, shown above, may have found the footprint left by dark matter.

NASA/European Space Agency ,

Data from Space Station bolsters theory of dark matter

  • Article by: JOHN HEILPRIN and SETH BORENSTEIN  Associated Press
  • April 3, 2013 - 8:51 PM

It is one of the cosmos’ most mysterious unsolved cases: dark matter. It is supposedly what holds the universe together. We can’t see it, but scientists are pretty sure it’s out there.

Led by a dogged, Nobel Prize-winning gumshoe who has spent 18 years on the case, scientists put a $2 billion detector aboard the International Space Station to try to track down the stuff. And after two years, the first evidence came in Wednesday: tantalizing cosmic footprints that seem to have been left by dark matter.

The evidence — the detection of hundreds of thousands of particles that have features suggesting that they are debris from collisions of dark matter particles — isn’t enough to declare the case closed. The footprints could have come from another, more conventional suspect: a pulsar, or a rotating, radiation-emitting star.

‘We’re going to solve this’

The Sam Spade in the investigation, physicist and Nobel laureate Sam Ting of the Massachusetts Institute of Technology, said he expects a more definitive answer in a matter of months. He promised: “There is no question we’re going to solve this problem.”

California Institute of Technology physicist Sean Carroll, said, “It’s a sign of something.”

The results from the Alpha Magnetic Spectrometer, or AMS, are significant because dark matter is thought to make up about a quarter of all the matter in the universe. “We live in a sea of dark matter,” said Michael Salamon, who runs the AMS program for the Energy Department. Unraveling the mystery could help scientists better understand the composition of our universe and what holds galaxies together.

Ting announced the findings in Geneva at the European Organization for Nuclear Research, the particle physics laboratory known as CERN.

The 7-ton detector was sent into space in 2011 in a shuttle mission commanded by astronaut Mark Kelly while his wife, then-Rep. Gabrielle Giffords, was recovering from a gunshot wound to the head. The device, which rides a truss on the space station like a bell on a bicycle’s handlebars, is transmitting its data to CERN.

For 80 years scientists have theorized the existence of dark matter. They have looked for it in accelerators that smash particles together. They’ve looked deep underground with special detectors. But neither worked.

Then there’s a third way: looking for the results of rare dark matter collisions. If particles of dark matter crash and annihilate each other, they should leave a footprint of positrons — the anti-matter version of electrons — at high energy levels. That’s what Ting’s group is looking for.

‘80-year-old detective story’

They found some. What’s key is the curve of the plot of those positrons. If the curve is one shape, it points to dark matter. If it’s another, it points to pulsars. Ting said they should know the curve soon.

“This is an 80-year-old detective story and we are getting close to the end,” said University of Chicago physicist Michael Turner. “This is a tantalizing clue.”

The Washington Post contributed to this report.

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