Latest news with #impactcrater
Forbes
2 days ago
- Science
- Forbes
Earth's Oldest Impact Crater May Be Far Younger Than Thought
A satellite image of Gosses Bluff Crater located near the center of Australia. The crater is ... More believed to have been created by an asteroid impact around 142 million years ago. In March 2025, researchers from the Curtins School of Earth and Planetary Sciences and the Geological Survey of Western Australia announced the discovery of Earth's oldest impact crater, located in the very heart of the Pilbara region of Western Australia. Based on their field investigations, the crater formed about 3.5 billion years ago, making it the oldest known by more than a billion years — the previous record holder being the Vredefort structure in South Africa. However, a new study challenges the initial findings by reassessing the age of the impact crater. As study authors Aaron J. Cavosie, Professor for Earth and Planetary Sciences, Curtin University, and Alec R. Brenner, Postdoc at Yale University, write for the online magazine The Conversation, they discovered geological evidence suggesting the impact happened almost one billion years later than previously thought. Both studies mapped the distribution of shatter cones, cone-shaped branching structures forming at the moment of impact, when shock waves shatter the bedrock. Example of shatter cones preserved in limestone. The first study discovered shatter cones in 3.47 billion year-old sediment layers, deducing that the impact happened over 3 billion years ago. However, a more recent field survey discovered shatter cones also in lava covering the sediment layers, and therefore of younger age. The impact had to occur after the formation of the youngest rocks that contained shatter cones, meaning sometime after the 2.77-billion-year-old lavas. The authors of the new study also propose to name the crater 'Miralga impact structure," after the Aboriginal name of the region. The study," Geology and Mars analog potential of the <2.7-billion-year-old Miralga impact structure, North Pole Dome, Pilbara Craton, Australia," was published in the journal Science Advances.
The Independent
6 days ago
- Science
- The Independent
New study challenges discovery of Earth's ‘oldest' impact crater
Ever been late because you misread a clock? Sometimes, the 'clocks' geologists use to date events can also be misread. Unravelling Earth 's 4.5-billion-year history with rocks is tricky business. Case in point: the discovery of an ancient meteorite impact crater was recently reported in the remote Pilbara region of Western Australia. The original study, by a different group, made headlines with the claim that the crater formed 3.5 billion years ago. If true, it would be Earth's oldest by far. As it turns out, we'd also been investigating the same site. Our results are published in Science Advances today. While we agree that this is the site of an ancient meteorite impact, we have reached different conclusions about its age, size and significance. Let's consider the claims made about this fascinating crater. One impact crater, two versions of events Planetary scientists search for ancient impacts to learn about Earth's early formation. So far, nobody has found an impact crater older than the 2.23-billion-year-old Yarrabubba structure, also in Australia. (Some of the authors from both 2025 Pilbara studies were coauthors on the 2020 Yarrabubba study.) The new contender is located in an area called North Pole Dome. Despite the name, this isn't where Santa lives. It's an arid, hot, ochre-stained landscape. The first report on the new crater claimed it formed 3.5 billion years ago, and was more than 100 kilometres in diameter. It was proposed that such a large impact might have played a role in forming continental crust in the Pilbara. More speculatively, the researchers also suggested it may have influenced early life. Our study concludes that the impact actually happened much later, sometime after 2.7 billion years ago. This is at least 800 million years younger than the earlier estimate (and we think it's probably even younger; more on that in a moment). We also determined the crater was much smaller – about 16km in diameter. In our view, this impact was too young and too small to have influenced continent formation or early life. So, how could two studies arrive at such different findings? Subtle clues of an impact The originally circular crater is deeply eroded, leaving only subtle clues on the landscape. However, among the rust-coloured basalts are unique telltale signs of meteorite impact: shatter cones. Shatter cones are distinctive fossilised imprints of shock waves that have passed through rocks. Their unique conical shapes form under brief but immense pressure where a meteorite strikes Earth. Both studies found shatter cones, and agree that the site is an ancient impact. This new crater also needed a name. We consulted the local Aboriginal people, the Nyamal, who shared the traditional name for this place and its people: Miralga. The 'Miralga impact structure' name recognises this heritage. Determining the timing of the impact The impact age was estimated by field observations, as neither study found material likely to yield an impact age by radiometric dating, a method that uses measurements of radioactive isotopes. Both studies applied a geological principle called the law of superposition. This states that rock layers get deposited one on top of another over time, so rocks on top are younger than those below. The first group found shatter cones within and below a sedimentary layer known to have been deposited 3.47 billion years ago, but no shatter cones in younger rocks above this layer. This meant the impact occurred during deposition of the sedimentary layer. Their observation seemed to be a 'smoking gun' for an impact 3.47 billion years ago. As it turns out, there was more to the story. Our investigation found shatter cones in the same 3.47 billion-year-old rocks, but also in younger overlying rocks, including lavas known to have erupted 2.77 billion years ago. The impact had to occur after the formation of the youngest rocks that contained shatter cones, meaning sometime after the 2.77-billion-year-old lavas. At the moment, we don't know precisely how young the crater is. We can only constrain the impact to have occurred between 2.7 billion and 400 million years ago. We're working on dating the impact by isotopic methods, but these results aren't yet in. Smaller than originally thought We made a first map showing where shatter cones are found. There are many hundreds over an area 6km across. From this map and their orientations, we calculate that the original crater was about 16km in diameter. A 16km crater is a far cry from the original estimate of more than 100km. It's too small to have influenced the formation of continents or life. By the time of the impact, the Pilbara was already quite old. A new connection to Mars Science is a self-policing sport. Claims of discovery are based on data available at the time, but they often require modification based on new data or observations. While it's not the world's oldest, the Miralga impact is scientifically unique, as craters formed in basalt are rare. Most basalts there formed 3.47 billion years ago, making them the oldest shocked target rocks known. Prior to impact, these ancient basalts had been chemically altered by seawater. Sedimentary rocks nearby also contain the earliest well-established fossils on Earth. Such rocks likely covered much of early Earth and Mars. This makes the Miralga impact structure a playground for planetary scientists studying the cratered surface (and maybe early life) of Mars. It's an easily accessible proving ground for Mars exploration instruments and imagery, right here on Earth. Aaron J. Cavosie is a Senior Lecturer in the School of Earth and Planetary Sciences at Curtin University. Alec Brenner is a Postdoc in Earth and Planetary Sciences at Yale University.
