Dark matter eludes the human eye and just about every known instrument that astronomers have developed for observing outer space, but researchers on-board the International Space Station think that they just might have spotted its footprint. Using a cosmic ray detector, an on-board team captured particle interactions that may be the final proof that researchers have been seeking for decades for this mysterious class of matter, which they think makes up a quarter of the universe even though no one has conclusively proven its existence.
The detector, the space station’s Alpha Magnetic Spectrometer, has been scanning deep space for cosmic radiation particles, as well as particles of cosmic antimatter and dark matter, since its installation in 2011. On Wednesday, April 3, two international research teams gathered simultaneously at NASA in Washington, DC, and CERN in Switzerland, to jointly report that streams of data that the detector had gathered of 25 billion cosmic-ray events indicate higher-than-expected concentrations of positrons—the antimatter counterpart to electrons—within the cosmic radiation. This is a sign of dark matter, the researchers argued, because per the theory, whenever dark-matter particles run into each other, they destroy each other and create positrons. Positrons, being antimatter, rarely ever occur otherwise.
Dark matter does not interact with light, so even if it is out there, researchers cannot expect to see it. Instead, they must look for signs of its presence, such as high-energy collisions or, in this case, high numbers of positrons.
The researchers have not yet rules out other possible sources for the positrons, however. Pulsars—celestial bodies that give off regularly recurring pulses of light and radiation—could give rise to positrons, as well.
Further research may provide definitive answers. Much of that research might take place at CERN itself, as the science institution is scheduled to restart its large hardon collider in early 2015. The collider, which crashes particles together at accelerated speeds, is useful for simulating many deep-space particle interactions and was instrumental in proving the existence of the Higgs-Boson particle in the past year.
Proving the existence of dark matter would be another major coup for scientific researchers. Many prevalent theories about the universe include dark matter as a key lynchpin, some theories identifying it as the force behind the universe’s ongoing expansion. Dark matter has a central role in string theory, the particle physics subset that seeks to reconcile quantum mechanics and general physics, as well.