Ancient Crystals Have Revealed the Oldest Meteorite Crater on Earth

The Yarrabubba impact structure in Australia dates back some 2.2 billion years, 200 million years older than any other known crater.
January 21, 2020, 4:08pm
​Concept art of asteroid impact. Image: Marc Ward/Stocktrek Images
Concept art of asteroid impact. Image: Marc Ward/Stocktrek Images

Scientists have identified Yarrabubba crater, which stretches for more than 40 miles across Western Australia, as the oldest impact structure on Earth, according to a new study.

The crater was formed about 2.229 billion years ago by a huge extraterrestrial rock that slammed into our planet—an event that may have played a major role in climate changes during that era.

While Yarrabubba crater has been recognized as one of the oldest craters on our planet for years, a team led by Timmons Erickson, a research scientist at NASA’s Johnson Space Center, used ancient crystals to produce the first precise age of this momentous impact.

The results, published on Tuesday in Nature Communications, extend “the terrestrial record of impact craters by 200 million years” and demonstrate “the potential for discovery of ancient impact structures” in landscapes similar to Yarrabubba crater, said Erickson’s team in the study.

Erickson and his colleagues were able to pinpoint this new timeline by extracting samples of zircon and monazite from the base of Yarrabubba crater. These robust minerals were shocked into a crystallized form by the sheer energy of the impact with the space rock, which the team estimates was several miles in diameter.

The scientists used uranium-lead dating to estimate the age of the crystals, which turned out to be hundreds of millions of years older than other ancient craters such as Vredefort Dome in South Africa or the Sudbury structure in Canada.

Impact craters that date back billions of years are relatively rare on Earth because our planet is so geologically active. Processes such as plate tectonics and volcanism are constantly eroding and erasing the record of Earth’s past collisions with random space rocks.

One consequence of this planetary amnesia is that “connections between impact events and punctuated changes to the atmosphere, oceans, lithosphere, and life remain difficult to establish, with the notable exception of the Cretaceous–Paleogene impact,” which wiped out the dinosaurs, the team said in the study.

This is particularly tantalizing in the case of the Yarrabubba impact, which seems to have struck during an icy period in our planet’s history, when glaciers covered what is now Western Australia.

To get a sense of how the impact may have influenced global processes at the time, Erickson’s team modeled the potential climate outcomes of a large impactor crashing into a snow-packed continent.

The results revealed that such a collision would have sent a half-trillion tons of water vapor into the atmosphere, which may have sparked a warming period. Erickson and his colleagues cited evidence that glaciers retreated in the era following the Yarrabubba impact as a potential link between the collision and worldwide climate changes.

“The effects of impact cratering have long been recognized as drivers of climate change,” the team noted in the study. While the Yarrabubba structure represents Earth’s oldest dated impact crater, the researchers added, its coincidence with melting glaciers “prompts further consideration of the ability of meteorite impacts to trigger climate change.”