Ancient comet explosion turned the world's driest desert into glass

The dark glass fields that dot the world's driest Atacama Desert were created by a comet that exploded about 12,000 years ago.

The Atacama Desert in Chile is famous for being used as a simulation site for extraterrestrial environments, such as those on Mars. According to a new study, researchers believe this desert was the site of a comet explosion powerful enough to create giant slabs of silicate glass that have survived to this day.

Researchers believe that the Atacama Desert was the site of a massive comet explosion that melted sand into silicate glass. (Photo: Pete Schultz/Brown University)

Roughly 12,000 years ago, intense heat turned the Atacama's sandy soils into vast swaths of glass, stretching 75km, but researchers aren't sure, according to research published November 3 in the journal Geology. What caused such a drastic change?

The Atacama Desert is the driest land on Earth, with extremely low humidity and rainfall. Desert glass, which is already fragmented, contains many small mineral fragments commonly found in meteorites that fall to Earth.

The minerals found in this glass match those collected by NASA's Stardust mission, which sampled a comet known as Wild 2 . The researchers are confident that the minerals found in the Chilean desert are what was left behind by a comet similar to Wild 2, when it exploded in the desert and 'melted' the sand.

Pete Schultz, study author and Professor Emeritus of Geosciences at Brown University, said : 'This is the first time we have unequivocal evidence of glass on Earth being made by heat and wind radiation from a fireball exploding just above the surface'.

'To create such a powerful effect over such a large area, this has to be a really big explosion. Many of us have seen fireballs in the sky, but those are small blisters compared to this explosion,' added Professor Schultz.

The European Space Agency (ESA) tested the Mars rover in the Atacama Desert. (Photo: ESA)

Fancy glass fields, dark green or black, stretch across the eastern region of the  Pampa del Tamarugal plateau , between the Andes and the Chilean coastal strip. Although volcanic activity can also produce this type of glass, there is no evidence that Atacama glass was formed that way.

Previously, researchers thought that ancient fires could be the cause of glass. This area used to be a grassy swamp. If those ancient blades of grass were burned in widespread wildfires, some believe it could produce glass.

However, the composition of the glass at Atacama is more complex . On closer inspection, it appears that the pieces of glass have been twisted, folded, rolled and tossed while they are still molten. Scientists think this can only happen in a big bang, creating winds that are comparable to tornadoes.

Silicate glass is scattered across the Atacama Desert, which is also known as "Mars on Earth".

A chemical analysis of Atacama glass showed that the zircons , or minerals, had decomposed thermally to form baddeleyite crystals . This reaction can only happen when the temperature spikes above 1,650 degrees Celsius, which is certainly much higher than a grass fire.

The analysis also revealed that minerals such as cubanite and troilite were both found in comet Wild 2 and meteorites.

"Those minerals tell us that this object has all the hallmarks of a star ," said Scott Harris, study co-author and planetary geologist at the Fernbank Science Center in Georgia. broom. This glass has the same mineralogical composition that we have seen in the samples of the Stardust mission, which is indeed strong evidence that what we are witnessing is the result of a stellar gas explosion. broom'.

The researchers now want to focus on dating the Atacama glass to find out its exact age, as well as the size of the comet. They speculate that the collision occurred about 12,000 years ago, which is consistent with the time when large mammals disappeared from the area.