Cubic zirconia, originating from the Mistastin Lake crater in Canada—a geological formation spanning 28 kilometers (17.4 miles) in diameter—necessitated temperatures exceeding 2,370 degrees Celsius for its formation. This temperature represents the highest ever recorded on Earth’s terrestrial surface.
A sample of glass that registered at 2,370 degrees Celsius. Image attribution: Gavin Tolometti.
In the year 2011, a researcher from the University of Western Ontario, Michael Zanetti, along with his associates,
uncovered a vitrified rock containing minute zircon crystals within the
Mistastin Lake crater.
Subsequent analysis of that particular rock revealed that it was formed at a scorching 2,370 degrees Celsius as a direct consequence of an extraterrestrial impact event.
In a more recent investigation, utilizing specimens gathered between 2009 and 2011, the scientific team succeeded in identifying four additional zircon fragments, thereby corroborating the findings from the 2011 discovery.
Furthermore, they detected and documented evidence in a separate area within the same impact structure, indicating that the impact melt—rock material that liquefies following a meteor strike—experienced differential superheating across multiple locations, reaching temperatures even higher than previously hypothesized.
“The most significant implication stemming from this research is the enhanced understanding we are gaining regarding the extreme temperatures attained within impact melt rocks, which initially form upon a meteorite’s impact with the surface. This consequently provides us with a more comprehensive insight into the thermal history of the melt and its cooling progression within this specific crater,” expounded Gavin Tolometti, a postdoctoral student at the University of Western Ontario.
“This knowledge can also furnish us with valuable perspectives for examining the thermal conditions and melt formations at other impact craters.”
“The majority of the intact evidence, such as vitreous samples and impact melt specimens, were situated in close proximity to the crater floor,” he further elaborated.
“By applying this acquired knowledge to different impact craters, researchers may be able to unearth further evidence pertaining to the thermal environments present in other craters, even with less extensive investigative efforts.”
“We are beginning to apprehend that if our objective is to discover evidence of such elevated temperatures, a strategic focus on particular regions is imperative, rather than adopting a random selection approach across an entire crater.”
According to the research collective, this marks the inaugural instance of reidites—a mineral phase that crystallizes when zircon is subjected to intense pressure and heat—being detected at the Mistastin site.
The investigators identified three reidites that remained preserved within the zircon grains, alongside evidence suggesting the prior existence of two additional reidites that had subsequently decomposed once temperatures surpassed 1,200 degrees Celsius, a threshold beyond which reidite loses its stability.
This particular mineral constituent allows scientists to more precisely delineate the pressure regimes, hinting at the potential for peak pressure conditions ranging from approximately 30 to potentially exceeding 40 GPa (gigapascals).
These pressure conditions are understood to have been engendered during the meteorite’s impact event on the planetary surface at that historical juncture.
The proximity of an object to the impact event directly correlates with the magnitude of the pressure it would experience.
Certain minerals that have undergone substantial compression due to this event—collectively referred to as ‘shocked’—retain microscopic structures that are amenable to scientific scrutiny.
“Considering the substantial size of the reidites observed in our samples, we ascertained that the minimum pressure it likely registered was in the vicinity of 30 GPa,” stated Tolometti.
“However, given the considerable presence of reidites within some of these grains, we infer that the pressure could have even exceeded 40 GPa.”
“This finding offers a more refined understanding of the pressure levels generated in the peripheral zones surrounding the molten core during the meteorite’s impact with the surface.”
“It is understood that the central melting zone would, by definition, typically experience pressures exceeding 100 GPa, a condition under which rock would undergo complete liquefaction or vaporization outside of these extreme parameters.”
The research paper detailing these findings was published in the esteemed 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
