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Scientists Confirm Discovery of ‘Hottest Rock on Earth’


Cubic zirconia from the 28-km- (17.4-mile) wide Mistastin Lake crater in Canada required >2,370 degrees Celsius melt, which is hottest recorded on Earth’s surface.

A sample of glass that recorded at 2,370 degrees Celsius. Image credit: Gavin Tolometti.

A sample of glass that recorded at 2,370 degrees Celsius. Image credit: Gavin Tolometti.

In 2011, University of Western Ontario researcher Michael Zanetti and colleagues found a glass rock that contained small zircon grains in the Mistastin Lake crater.

That rock was later analyzed and found to have been formed at 2,370 degrees Celsius as a result of an asteroid impact.

In the new study using samples collected between 2009 and 2011, the researchers were able to find four additional zircon grains that confirmed the 2011 discovery to be true.

They also located and found evidence in a different location within the same impact structure that the melt rock — rocks created after rock and soil melt into liquid after a meteor strikes — was differently superheated in more than one location, to a greater degree than previously theorized.

“The biggest implication is that we are getting a much better idea of how hot these impact melt rocks are, which initially formed when the meteorite struck the surface, and it gives us a much better idea of the history of the melt and how it cooled in this particular crater,” said University of Western Ontario postdoctoral student Gavin Tolometti.

“It can also give us insight to study the temperature and melts in other impact craters.”

“Most of the preserved evidence, such as glass samples and impact melt samples, were found close to the crater floor,” he added.

“By applying this knowledge to other impact craters, researchers might be able to find more evidence of the temperature conditions found in other craters but in less extensive studies.”

“We’re starting to realize that if we’re wanting to find evidence of temperatures this high, we need to look at specific regions instead of randomly selecting across an entire crater.”

According to the team, this is the first time reidites — a mineral formed when zircon undergoes high pressure and temperatures — have been discovered at the Mistastin site.

The researchers found three reidites that were still preserved in the zircon grains, and evidence that another two were once present but had crystallized when temperatures had exceeded 1,200 degrees Celsius, at which point the reidite was no longer stable.

This mineral allows the scientists to better constrain the pressure conditions indicating that there may have been a peak pressure condition around 30 to potentially above 40 GPa (gigapascals).

These are the pressure conditions that were created when the meteorite struck the surface at that time.

The closer something is to the impact event, the higher the pressure is going to be.

Certain minerals that have been compressed greatly by this event — referred to as ‘shocked’ — leave behind structures that can be studied.

“Considering how big the reidite was in our samples, we knew the minimum pressure it probably recorded was about 30 GPa,” Tolometti said.

“But since there is a lot of reidites still present within some of these grains, we know that it could even be above 40 GPa.”

“This provides a better idea of the amount of pressure produced outside of the melting zone when the meteorite struck the surface.”

“The melting zone will, by default, have pressures usually above 100 GPa, at which point a rock will completely melt or vaporize outside of those conditions.”

The study was published in the journal Earth and Planetary Science Letters.

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G.D. Tolometti et al. 2022. Hot rocks: Constraining the thermal conditions of the Mistastin Lake impact melt deposits using zircon grain microstructures. Earth and Planetary Science Letters 584: 117523; doi: 10.1016/j.epsl.2022.117523



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