Researchers discovered the oldest meteorite impact crater known to science in Australia.
Researchers discovered the oldest meteorite impact crater known to science in Australia.
Researchers have discovered the oldest meteorite impact crater known to science in Western Australia’s Pilbara region. The feature is more than one billion years older than the previous first-place contender, and could hold important implications for understanding the origin of life on our planet. The discovery is detailed in a study published Thursday in Nature Communications.
“Before our discovery, the oldest impact crater was 2.2 billion years old, so this is by far the oldest known crater ever found on Earth,” Curtin University’s Tim Johnson, a geologist and co-author of the study, says in a statement. The team dated the crater to 3.5 billion years ago.
Curiously, the discovery of the world’s oldest meteorite impact crater actually began with a question about Earth: how did the first continents—our planet’s oldest rocks—form more than three billion years ago? While many theories involve geological processes powered by heat from Earth’s core, Johnson and his colleagues have previously argued that the formation of Pilbara would have required extraterrestrial energy.
They suggest that large meteorite collisions could have caused Earth’s mantle to form “blobs” of volcanic material that over time became continental crust. To make a compelling case, however, they had to find evidence of a meteor impact that corresponded with that timeline—which is exactly what they did.
“The crater was exactly where we had hoped it would be,” Johnson and some of his co-authors wrote in an article in the Conversation. But the team didn’t find a giant crater basin—after all, 3.5 billion years is plenty of time for erosion to do its thing. Instead, they found the next best option: a rock formation known as shatter cones, in an area of the Pilbara region called the North Pole Dome.
"They're these beautiful, delicate little structures that look a little bit like an inverted badminton shuttle cock with the top knocked off," Johnson explains to ABC’s Peter de Kruijff. “So, upward facing cones with delicate feathery-like features. The only way you can form those in natural rocks is from a large meteorite impact.”
This particular meteorite would have struck Earth at over 22,300 miles per hour, sending debris across the planet and creating a crater more than 62 miles in diameter, according to the statement.
Furthermore, “uncovering this impact and finding more from the same time period could explain a lot about how life may have got started, as impact craters created environments friendly to microbial life such as hot water pools,” Chris Kirkland, a geologist at Curtin University who co-led the study, explains in the statement. In fact, previous research has even suggested that we should be searching for evidence of bygone Martian life in the Red Planet’s impact craters.
While Marc Norman, a planetary scientist from Australian National University who was not involved in the study, confirms that shatter cones are strong evidence of a meteorite impact crater, he adds that “the study lacks solid evidence for the size of this particular crater or how it relates to the role of impacts on the early Earth,” per ABC.
Nevertheless, “we had argued that meteorite impacts played a fundamental role in the geological history of our planet,” the researchers concluded in the Conversation article. “Now we and others have the chance to test these ideas based on hard evidence.”