Scientists close in on mysterious dark matter By Robert Evans GENEVA (Reuters) - Scientists said on Wednesday they may be close to tracking down the mysterious "dark matter," a substance that makes up more than a quarter of the universe but has never been seen. A final identification of what makes up the enigmatic material would open up whole new areas of research including the possibility of multiple universes and other dimensions, said physicists. An international team at Geneva's CERN research center said it had picked up what might be the first physical trace left by dark matter while studying cosmic rays recorded on board the International Space Station over the past 18 months. They had found a surge of positron particles which may have been created by decaying dark matter - a substance so central to the universe it sets the position of planets and stars. Samuel Ting, chief of the project that built CERN's giant AMS particle detector, told a crowded seminar at the center more data was needed to be sure that dark matter had been sighted. "Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or if they have some other origin," he said. Ting said it was also possible the surges came from pulsars - rotating neutron stars that emit a pulsing radiation. But CERN physicist Pauline Gagnon told Reuters after hearing Ting that the precision of the AMS could make it possible "to get a first hold on dark matter really soon." That would be terrific, like discovering a completely new continent. It would really open the door to a whole new world," said Gagnon. Dark matter, which surrounds galaxies across the universe, is invisible because it does not reflect light. Its presence has been established by the gravitational pull it exerts on planets and stars. Last week, the European Space Agency's Planck telescope revealed data from just after the Big Bang 13.8 billion years ago showing the mysterious substance made up 26.8 percent of the density of the universe, more than previously thought. Normal matter, the galaxies and planets that can be seen by astronomers with ever-increasing powerful telescopes, makes up only 4.9 per cent. The rest is an even more enigmatic "dark energy" believed to be driving the expansion of the universe. Ting has described dark matter as "one of the most important mysteries of physics today." Its traces are being sought not only through the AMS, or Alpha Magnetic Spectrometer, but in laboratories on earth and deep below ground. Editing by Andrew Heavens