Hot, strong winds would have burned the sand, turning it into silicate glass. The fragments in the area in Chile may have originated from the explosion of a large comet.
The peculiar and mysterious glass fragments, which are scattered in the Atacama Desert in Chile, may have originated from the explosion of a large comet in the Earth's atmosphere about 12 thousand years ago. That's what a new study conducted by Brown University claims. The blast, or a series of consecutive flares, would have produced strong winds like tornadoes and scorching heat, capable of burning the sand in the area, turning it into silicate glass or a solid that contains silicon and oxygen.
Research on the material in the Atacama Desert
The glass deposits in the Chilean desert were discovered, for the first time, about a decade ago, but their origins had remained a mystery until now. The silica fragments, some dark green, some black, are found concentrated along a corridor of about 75 kilometers. According to Brown University, they are "twisted and bent" and stretch up to 50 centimeters in diameter, or slightly larger than a pizza box.
Researchers who first discovered the fragments assumed they came from a bolide, or fireball that exploded in the atmosphere; while another study believed they were the result of intense grass fires. At that time, according to the analysis of Brown University, the area was not a desert, had sandy soil, but also trees.
The analysis of fragments in the Atacama Desert
Scientists from the United States and Chile conducted a chemical analysis on dozens of glass samples found in the desert. Inside, they found minerals called zircons, some of which had decomposed into baddeleyite, a rare zirconium oxide mineral. This transition from zircon to baddeleyite typically occurs at temperatures above 3,040 degrees Fahrenheit (1,670 degrees Celsius), much hotter than the temperature that grass fires would have reached.
The minerals found in the fragments previously had only been observed in meteorites and other rocks originating in space. Some of them, such as cubanite and troilite, were similar to minerals discovered in samples from a comet called Wild 2 collected by Nasa's Stardust mission. "This is the first time we have clear evidence of glass fragments on Earth that were created by thermal radiation and winds from a fireball that exploded just above the surface," said the study's lead author Pete Schultz, professor emeritus in the Department of Earth, Environmental and Planetary Sciences.
The researchers estimated that the explosion occurred about 12,000 years ago, but they hope further studies will help pinpoint the date and size of the comet more accurately. Meanwhile, still regarding the stars, the largest meteor ever observed would be on its way to Earth, while a strange object half asteroid and half comet has been spotted in space.
Stefania Bernardini