Did a Comet Explode Over South America 12,000 Years Ago?

Glass slabs in the Atacama
Concentration of glassy slabs (darkish plenty) at Quebrada de Chipana.
P. Schultz et al. / Geology 2021

A decade in the past, researchers found enormous chunks and slabs of darkish green and black glass strewn throughout a 75 kilometer–lengthy swath of the Atacama Desert in northern Chile.  New proof suggests they have been created by an incoming fireball.

The glass items are uncannily just like trinitite, the glassy mineral solid by the warmth of the primary atomic bomb check within the New Mexico desert in 1945. Carbon-14 relationship of natural matter in soil straight beneath and involved with the glass indicated that the chunks fashioned about 12,000 years in the past, when the world was a grassy wetland dotted with timber.

Early investigators speculated that intense grassfires melted sandy soil to create the huge fields of glass. But new findings by a crew led by Peter Schulz of Brown University disprove that rationalization. Reporting November 2nd in Geology, the crew as an alternative suggests a much more violent — and cosmic — origin.

Schultz and his colleagues subjected 300 glass samples, collected at extensively separated websites, to a complete chemical evaluation. They discovered that grains of the mineral zircon (zirconium silicate) embedded within the glass had been partially transformed into baddeleyite, a uncommon type of primarily pure zirconium oxide. That transformation requires temperatures exceeding 1,670°C (3,040°F), a lot hotter than any grass hearth.

Impact glass
Detailed pictures of zircon inclusions within the affect glass present that among the zirconium silicate has reworked into zirconium oxide, indicating excessive warmth.
Schultz et al. / Geology 2021

Volcanic eruptions can transport baddeleyite to the floor from the higher mantle, the place it coats zircon particles within the diamond-bearing rock kimberlite. Yet there’s no proof that volcanic exercise created the Atacama Desert glass.

The glass can be riddled with inclusions of a number of “alien” minerals present in samples of Comet Wild 2, which NASA’s Stardust mission retrieved in 2006. Many of the slabs seem twisted and folded, as if subjected to tornado-force winds whereas molten.

To Schultz and his colleagues, the chemical signature of exceptionally excessive temperatures, the otherworldly composition of the entrained particles, the contorted types of many glass shards, and the absence of an affect crater are compelling proof that a cosmic intruder exploded over South America at an altitude of lower than a mile. The fireball’s intense radiant warmth fused the underlying soil into molten glass; a sequence of blast waves then sheared and tossed the glass about earlier than it solidified.

Twisted glass slab
This twisted glass slab was present in Puquio de Núñez.
P. Schultz et al. / Geology 2021

The elongated form of the glass area could also be the results of a single cometary physique with a grazing trajectory or a cluster of comet fragments that entered the ambiance at a greater angle, just like the collision of tidally disrupted Shoemaker-Levy 9 with Jupiter in 1994. According to Schultz, the power of the airburst over Chile dwarfed the 12-megaton Tunguska Event that felled 80 million timber in a distant Siberian wilderness in 1908.   

The age of the Atacama Desert glass coincides with the re-advance of glaciers within the Andes and the sudden disappearance of greater than 80% of the massive mammals in South America. Schultz doesn’t declare a direct causal hyperlink to those local weather and extinction occasions, however he does discover the timing intriguing.

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