A fireball turned kilometers of the Atacama desert into glass thousands of years ago

(CNN) – The Atacama Desert in Chile has been used to simulate extraterrestrial environments, such as Mars, on Earth. Now, researchers believe that a comet here exploded with enough intensity to create gigantic plates of silicate glass, according to a new study.

The research was published Tuesday in the journal Geology.

About 12,000 years ago, intense heat turned the sandy soil of the Atacama into vast areas of glass that stretched for 75 kilometers, but researchers weren’t sure what caused such a drastic change.

The Atacama Desert is the driest region on Earth, with an incredibly low level of humidity and rainfall. Fractionated desert glass contains tiny mineral fragments commonly found in meteorites that reach Earth.

The minerals found in this glass match the particles collected by NASA’s Stardust mission, which sampled a comet known as Wild 2. Researchers are sure that the minerals they found in the Chilean desert are what was left after that a comet similar to Wild 2 exploded on the sand and melted it.

“This is the first time that we have clear evidence of glass on Earth that was created by thermal radiation and winds from a fireball that exploded just above the surface,” study author Pete Schultz said in a statement. , Emeritus Professor of Geological Sciences at Brown University and Research Professor in Brown’s Department of Earth, Environmental, and Planetary Sciences. “To have such a drastic effect on such a large area, this was a truly massive explosion. Many of us have seen fireballs (bright meteors) streaking across the sky, but those are small flashes compared to this,” he explained.

How are the amazing glass fields of Atacama

The surprising fields of glass, with a dark green or black appearance, extend through an area to the east of the Pampa del Tamarugal plateau, located between the Andes mountain range and the Chilean coast mountain range. Although volcanic activity can create this type of glass, there is no evidence to show that Atacama glass was formed this way.

Investigators had previously suggested that fires were the cause. The area was once home to wetlands derived from rivers. If those ancient grasses had been burned in widespread wildfires, some believe they could have created the glass.

However, the glass itself is more complicated. Up close, the pieces of glass appear to have been twisted, bent, rolled, and thrown while still molten. This, according to the researchers, would only be possible with an air blast that could unleash winds that compete with those of tornadoes.

A chemical analysis of the glass revealed the presence of zircons, minerals that thermally decomposed to form baddeleyite crystals. This change can only occur when the temperature rises above 1,600 degrees Celsius, which would definitely exceed the heat generated by fires.

The analysis also showed minerals such as cubanite and troilite, both found in Comet Wild 2 and in meteorites.

“Those minerals are what tell us that this object has all the markings of a comet,” said Scott Harris, a co-author of the study and a planetary geologist at the Fernbank Science Center in Georgia, in a statement. “Having the same mineralogy that we saw in the Stardust (mission) samples in these glasses is really powerful evidence that what we’re seeing is the result of a cometary air blast.”

The investigation continues

The researchers want to focus on dating the glass to determine its exact age, as well as the comet’s potential size, but their current expectation that the impact occurred 12,000 years ago aligns with when the large mammals disappeared from the area. .

“It’s too early to say whether there was a causal connection or not, but what we can say is that this event happened around the same time we think the megafauna disappeared, which is intriguing,” Schultz said. “There is also the possibility that this was witnessed by the first inhabitants, who had just arrived in the region. It would have been quite a spectacle.”