New data from two experiments — one in space, one on a balloon floating above Antarctica — hint at a tantalizing detection of dark matter, the mysterious stuff comprising 85% of the universe's matter. The evidence is a reported excess of high-energy electrons and their antimatter counterparts, positrons, which could be created as dark matter particles annihilate or decay. The signal from Fermi, the orbiting gamma-ray telescope, is subtle, whereas that claimed by the balloon-borne Advanced Thin Ionization Calorimeter (ATIC) is much more pronounced. The differences are puzzling, but the findings — according to some — could herald the birth of a new age of dark matter exploration.
“We may very well be seeing the beginning of the discovery era,” says Dan Hooper, a theorist at Fermi National Accelerator Laboratory in Batavia, Illinois, who is not affiliated with either of the experiments. Peter Michelson, principal investigator for the instrument on Fermi that made the detection, cautions that his group is not yet claiming to have found a smoking gun for dark matter. The signal could also come from more mundane sources nearby, such as pulsars, the spinning remnants of supernovae. “But if it isn't pulsars, it is some new physics,” says Michelson, of Stanford University in California.