By Freda Kreier
Scattered across a swath of the Atacama Desert in Chile lie twisted chunks of black and green glass. How the glass ended up there, sprinkled along a 75-kilometer-long corridor, has been a mystery.
Now, analyses of space dust in the glass show that the glass probably formed when a comet, or its remnants, exploded over the desert 12,000 years ago, researchers report November 2 in Geology.
This corridor is the best evidence yet of a comet impact site on Earth, says Peter Schultz, a planetary geologist at Brown University in Providence, R.I.
There are only about 190 known impact craters on Earth (SN: 12/18/18). Falling space rocks carved out these sites, but none are known to have been created by a comet. That’s because comets, which are made of mostly ice and some rock, tend to explode before reaching the ground, a fate they share with some small asteroids. These fiery events — known as airbursts — are dramatic, generating massive amounts of heat and strong winds. But the effects are temporary and often fail to leave lasting imprints, like craters, behind.