By Stacey Leasca
January 31, 2020

If you want a good look at Earth’s history, you’re going to have to travel to the town of Meekatharra in Australia. That’s where you’ll find Yarrabubba, the oldest known crater in the world.

In January, scientists studying the crater concluded that it was around 2.2 billion years old, or just about half the life of planet Earth. And this isn’t just any old asteroid or crater. According to the scientists, the asteroid’s impact may have been the event that kicked off the glacial warming period that ended the ice age.

“We studied tiny ‘impact-shocked’ crystals found at the site, which show the crater formed 2.229 billion years ago (give or take five million years),” the scientists, who studied the area, wrote in a new piece for The Conversation. “This new, precise date establishes Yarrabubba as the oldest recognized impact structure on Earth. It is some 200 million years older than the next oldest, the Vredefort impact in South Africa.”

Artist rendering of an asteroid in front of the Earth in Space.
Stocktrek Images/Getty Images

To discover the crater’s true age, the scientists looked at all the minerals along the crater walls. They then used the minerals’ “isotopic clocks” to date them. Inside the minerals, the team found small amounts of uranium, which degrade over time, allowing the scientists to estimate a timeline.

“The average Earth-crossing asteroid travels at over 15 kilometers per second [9.3 miles per second], which during an impact event results in extreme temperatures and pressures,” Timmons Erickson, who works at NASA’s Johnson Space Center and is one of the authors of the study, told Gizmodo. “These conditions can recrystallize the zircon and monazite, kick out the lead in the crystal lattice, and thus reset the clock to zero. By targeting the specific domains that had recrystallized, we were able to date the impact event.”

Following the asteroid’s impact, Erickson explained, the Earth released “significant water vapor, which is an even more efficient greenhouse gas than carbon dioxide.” That water vapor then entered the Earth’s atmosphere and could have caused it to warm over many years. So, the next time you want to thank something for all of human existence, send a little shout-out to this intergalactic asteroid, too.

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