May 20, 2022

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Traces of impact 36 million years ago

A fist-sized piece of black glass, discovered in 2011 in a meteorite crater in Canada and first studied in 2017, may have formed at a temperature of 2,370 degrees Celsius, well above the temperatures encountered. . This discovery was not accepted by the entire scientific community, because the values ​​seemed too high.

Now, a new, in-depth analysis of the minerals found within that rock has confirmed that what was discovered in 2017 is real without a doubt. The rocks in question were collected from a group of rock masses that formed after the surface crust melted after an asteroid impact that occurred about 36 million years ago, in what is now Labrador, Canada.

effect shape Mystastin nozzleWith a diameter of 28 km. There Michael Zanetti, then a doctoral student at Washington St. Louis University, collected glass rocks during a study funded by the Canadian Space Agency, which aims to find the best way to train astronauts who will one day serve. Moon or another planet. Mistystein crater looks a lot like the crater of the Moon and is often a place used to train astronauts. The collection of that sample, which was done at random, proved to be very important.

The most prominent rock analysis exist zirconMetals that crystallize at very high temperatures. During the first study, by studying the structure of those zircons, it was possible to trace the temperature that was present when they were formed with remarkable accuracy.

New search. To confirm the validity of the data, other zircons extracted from other rock samples had to be studied. In the new study, Gavin Tolomiti (Western University, Canada) and colleagues analyzed four other zircons in samples collected in the crater of rocks of different types, to get a more complete view of how the impact warms the Earth’s crust.

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consequences Study – published in Earth and Planetary Science Letters – Conclusively prove that zircon formed exactly at a temperature of 2370 ° C. Among other things, the study also highlighted the presence of another mineral, which is re, inside zircon granules. Reidites form when zircon exceeds certain temperatures and pressures, thus it is possible to trace the stresses made during the impact.

The collision between the asteroid and Earth has been shown to produce pressures ranging from 30 to 40 . GPa (10 GPa is the minimum pressure needed to form a diamond). Pressures that not only melted a large area of ​​the Earth’s crust, but in some areas must have already evaporated. This study will be important for the analysis of craters and other terrestrial craters that have formed on the Moon and Mars.