Asteroids traveling at high speeds collide with Earth, leaving behind meteor impact craters. Such cataclysmic events have been part of Earth’s history and are still taking place on other celestial bodies.
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Even though many significant asteroid impacts predetermined millions of years ago, their traces can still be seen on the Earth’s landscape today. The rocks at impact sites went through drastic heat and pressure when the asteroids struck.
One noteworthy site is West Clearwater Lake in Q , Canada, situated on the Canadian Shield close to Hudson Bay. This crater, which has since filled with water, was created when an asteroid hit our planet roughly 285 million years ago.
Understanding the Earth’s Temperature Grid
Zircon, a mineral prevalent in various rock types on Earth and found in some lunar rocks, stands out for its durability. It dates back to the beginnings of our planet. Because it’s so tough, zircon plays an essential role in examining geological events.
When exposed to sufficiently high temperatures, zircon breaks down into zirconia (ZrO₂) and silica (SiO₂). Depending on heat levels, zirconia can take different forms known as polymorphs—minerals that share the same chemical makeup but vary in crystal structures based on physical conditions. One notable polymorph of zirconia is cubic zirconia, named for its cube-like formation, as discussed in geological research.
Discovering natural cubic zirconia is exceedingly rare due to the high temperatures required to maintain its structure. The formation of cubic zirconia only happens in extreme conditions where temperatures soar above 2,370 °C. Earth’s surface progresses to such hot temperatures only during impact events, as noted by researchers.
At West Clearwater Lake, we uncovered signs of natural cubic zirconia safeguarded in glass formed from the intense heat caused by the ancient asteroid impact. To put things in perspective, hot spots found in active Hawaiian volcanoes reach temperatures only between 800 to 1,200 °C.
Cubic zirconia exists in a few forms due to varying temperature and pressure. These include monoclinic, tetragonal, and cubic shapes.
Monoclinic zirconia stands stable at lower temperatures and is the most common variant found naturally. In contrast, tetragonal zirconia is uncertain at cooler temperatures and exists at who maintains moderate heat invoices. Cubic zirconia remains stable exclusively at temperatures exceeding 2,370 °C, making its occurrence incredibly fleeting in the geological record.
A Glimpse into The Past
You might wonder how cubic zirconia came to be incorporated into these ancient rocks.
When the West Clearwater Lake asteroid collided with Earth millions of years back, it generated enough heat to both melt and vaporize some of the rock ! Surviving molten materials captured tiny zircon crystals initially found in the target rock as it solidified.
At extreme heat over 2,370 °C, zircon crystals began decomposing into cubic zirconia. This provided tangible evidence regarding the initial event of extreme heat, noted during our research detailed in a recent study.
These discoveries give fascinating insights into the intense temperatures arising from meteor impacts—a challenging feat to measure many eons later.
Cubic Zirconia in The Market
Artificially produced cubic zirconia is crafted by heating zirconium oxide under high temperatures, followed by controlled cooling which allows it to form crystals akin to diamonds. Many jewelry stores gravitate towards synthetic cubic zirconia as it’s a cost-effective substitute that retains a similar sparkle to real diamonds.
Manufactured cubic zirconia is bolstered with stabilizers like yttrium, helping it stay intact and sparkle over time. Without these additives, natural zirconia tends to morph into different types as they cool, leading to the rarity of naturally occurring cubic zirconia, only found where super-hot conditions once prevailed.
A Deeper Understanding of Asteroid Impacts
Finding cubic zirconia isn’t simply striking for geology lovers; it assists scientists in understanding the circumstances involved during asteroid impacts. These ancient events not only caused havoc but also profoundly altered the Earth’s surface—something we’re still attempting to unravel.
While cubic zirconia’s presence at West Clearwater Lake is exciting news, it represents only a tiny fraction of what we know. Asteroid impacts are pervasive in our solar system, with craters found on nearly everything rocky out there. For instance, cubic zirconia has been identified in moon rocks on Apollo mission returns.
These meteorite craters like West Clearwater Lake are critical, weaving into the larger narrative of the Earth’s past. Studies suggest that during its turbulent early years, Earth endured significant asteroid bombardment thanks to leftover debris from the solar system’s formation, simple colliding with our planet helped pen its geological story. Moreover, there’s solid evidence indicating asteroid impacts could have been key in creating environments conducive to the origin of life through the fostering of complex chemicals.
Further Reading: Neeraja S. Chinchalkar et al, Zircon microstructures record high temperature and pressure conditions during impact melt evolution at the West Clearwater Lake impact structure, Canada, Earth and Planetary Science Letters (2024). DOI: 10.1016/j.epsl.2024.118714
This article has been adapted from The Conversation under a Creative Commons license. You can check out the original piece here.
Article sourced by The Conversation. Originally published on Phys.org.
