The mystery of the crystals of the Atacama desert

Around 12,000 years ago, something burned a vast swath of the Atacama Desert in northern Chile. The heat was so intense that it turned the sandy soil into large plates of silicate glass. Now, a research team has come to a conclusion about what caused that inferno that covered the Atacama desert with crystals. As published in the magazine ‘geology’It was the impact of a comet.

The researchers noticed that desert glass samples contain small fragments with minerals often found in rocks of extraterrestrial origin. Those minerals match the composition of the material returned to Earth by the mission stardust NASA, which sampled the particles of a comet called Wild 2. The team concludes that these mineral assemblages are likely the remains of an extraterrestrial object, most likely a comet with a composition. similar to Wild 2, whose explosion melted the sandy surface below.

crystals on earth

“This is the first time we have clear evidence of crystals on Earth that were created by thermal radiation and winds from a fireball that exploded just above the surface.”says Pete Schultz, a professor at Brown University. “To have such a drastic effect over such a large area, this was a truly massive explosion. Many of us have seen fireballs streaking across the sky, but those are tiny dots compared to this.”.

The crystals are concentrated in patches throughout the Atacama Desert east of Pampa del Tamarugal, a plateau in northern Chile located between the Andes Mountains to the east and the Chilean Coastal Range to the west. The dark green or black glass fields lie within a corridor that stretches about 75 kilometers. There is no evidence that the crystals could have been created by volcanic activity, Schultz says, so their origin has been a mystery until now.

Tornado force winds

Some researchers have postulated that the glass was the result of ancient grass fires, as the region was not always a desert. During the Pleistocene epoch, there was an oasis with trees and grassy wetlands created by rivers that spread from the mountains to the east. It has been suggested that widespread fires may have burned hot enough to melt sandy soil into large glassy slabs.

But the amount of glass present along with several key physical characteristics make simple fires an impossible formation mechanism. The crystals show evidence of being twisted, bent, rolled, and even thrown while still in molten form. That’s consistent with a large blast from an incoming meteorite, which would have been accompanied by tornado-force winds.

Together with researchers from the Fernbank Science Center in Georgia, Chile’s Universidad Santo Tomás, and Chile’s Geology and Mining Service, Schultz and colleagues conducted a detailed chemical analysis of dozens of samples taken from glass deposits throughout the region.

The analysis found minerals called zircons that had thermally decomposed to form baddeleyite. That mineral transition typically occurs at temperatures above about 1,650 degrees C, much hotter than what could be generated by grass fires.

alien minerals

The analysis also revealed exotic mineral assemblages found only in meteorites and other extraterrestrial rocks. Specific minerals such as cubanite, troilite, and calcium- and aluminum-rich inclusions matched mineral signatures of cometary samples recovered from NASA’s Stardust mission.

“Those minerals are what tell us that this object has all the markings of a comet”says Scott Harris, a planetary geologist at the Fernbank Science Center and co-author of the study. “Having the same mineralogy that we saw in the Stardust samples in these crystals is really powerful evidence that what we’re seeing is the result of a cometary outburst.”. Although the researchers acknowledge that more work is needed to establish the exact age of these crystals, Schultz believes that the impact coincides in time with the disappearance of large mammals from the region.

“It’s too early to say if there was a causal connection or not, but what we can say is that this event happened around the same time as when we think the megafauna disappeared, which is intriguing.”he points out. “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,” he adds. The team also hopes to collect more data to learn the size of the impactor. In addition, he believes this study could help identify similar blast sites elsewhere.

Font: ABC

Reference article: https://www.abc.es/ciencia/abci-misterio-cristal-cubre-desierto-atacama-202111090106_noticia.html#ancla_comentarios