A 75-kilometre (47-mile) swath of desert is strewn with strange, dark, glassy rocks that have long puzzled scientists. New research finds that those rocks are quite similar to comet particles collected by a NASA mission called Stardust. The scientists behind the work think that all those years ago, one or more huge comets exploded together in the skies over the region, causing tornadoforce winds, scorching the grassy landscape and scattering the area with warped and twisted glass that still contains minerals generally found only in meteorites. “This is the first time we have clear evidence of glasses on Earth that were created by the thermal radiation and winds from a fireball exploding just above the surface,” said Pete Schultz, a geologist at Brown University.