Seven grains of interstellar dust reveal their secrets

first_imgEight years after a NASA mission brought them back to Earth, seven grains of interstellar dust keep giving scientists fresh puzzles to ponder. The flecks of dust had streaked into a tennis racket–sized collector on board a spacecraft named Stardust, and scientists announced their existence at the Lunar and Planetary Science Conference in March 2013. Researchers now report in Science that the alien visitors are unexpectedly diverse. After extracting the particles and analyzing them with powerful x-rays, the researchers were intrigued to find that the grains contained crystalline minerals; astronomical measurements had indicated that cosmic rays whipping around the galaxy destroy most crystals. Three small particles contain sulfide, but others are sulfur-free—a hint that Stardust may have sampled two different populations of interstellar dust. Next, the researchers plan to measure the abundance of oxygen isotopes within the grains; if they differ from the sun’s, the discrepancy would confirm that the dust comes from outside the solar system. In the meantime, the team is looking for more grains embedded in the collector with the help of Stardust@home, software that lets volunteers identify possible grains by examining images of the material on their home computers, tablets, and cellphones. More than 30,000 “dusters” are listed as co-authors of the Science paper.last_img