The Hiroshima bomb created an asteroid, a glass-like glass

When a 10 km wide asteroid hit the Earth about 66 million years ago, the explosion that followed wiped out the dinosaurs. When the United States dropped an atomic bomb on the city of Hiroshima, Japan on August 6, 1945, the explosion that followed killed more than 100,000 people.

When the asteroid hit, he turned the rock that he hit into molten glass. This glass, whistling through the air like ejecta, formed and solidified into small beads, or spherules, that rained on parts of the planet around the site of the impact.

When the atomic bomb exploded on Hiroshima, according to a new study published in the newspaper Anthropocenehe transformed parts of the city itself into molten glass. This glass formed spheres that rained around the city, and the scientists who discovered the pearls called them "Hiroshimaites".

Mario Wannier, a retired geologist who led the new research, retrieved 17 samples of beach sand from six beaches around the Motoujina Peninsula and Miyajima Island in Hiroshima. Wannier began by looking for tiny marine organism shells because he wanted to study the health of the local marine ecosystem. But when he examined the specimens under the microscope, he saw spherules sitting next to the shells.

"The main discovery is the elephant in the room we've never seen before," said Wannier, who explained that he had immediately recognized the spherules for what they were because they look a lot like spherules made by the dinosaur killer asteroid. . Wannier thinks pearls have survived so long without being washed away because the waters around the beaches that he sampled tend to be relatively calm.

To transform the material into glass, that is to say to vitrify it, the temperatures must reach a height of about 1800 ° C, explained Wannier. The atomic bomb, nicknamed Little Boy, caused the sand and rocks of Hiroshima Bay to reach hellish temperatures.

The rock that forms Hiroshima Bay is a Cretaceous granite and the crystals of this granite, including quartz and feldspar, constitute the majority of the sand grains of the beaches sampled by Wannier and his team. But these are not the only materials used to form pearls.

The spherules also have pieces of Hiroshima same. Some of the pearls, explains Wannier, contain iron and steel, materials probably coming from the buildings of the city.

One thing that the spherules do not have and that Christian Koeberl, a geochemist from the University of Vienna and not involved in the work, thinks he should have, it's a kind of radioactivity. Spherules collected at Alamogordo, Massachusetts, Trinity Atomic Explosion Test Site in 1945, are radioactive; so we could expect the Hiroshima beads to be similar, says Koeberl.

"The ultimate proof that these are really the fallout of Hiroshima is not there yet," Koeberl said. "[Wannier and other researchers] make a reasonable interpretation of what they have. Further studies are clearly needed. "

Koeberl tells himself that the Hiroshima logs, collected several kilometers to the south and southwest of the hypocenter of the atomic explosion, may be too far away to allow for the acquisition of a large dose of radiation.

Although the Hiroshimaites seem to lack radioactivity, this absence does not negate the idea that they were formed during the atomic explosion. To be sure, researchers need to find and study more spherule samples.

Wannier thinks there might be more such spherules in the sediments either at different sites around Hiroshima, or perhaps at the only other place where an atomic bomb was dropped on humans: Nagasaki.

-Lucas Joel, freelance journalist

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