Scientists have identified the oldest known impact crater on Earth — and the ancient structure could tell us how our planet emerged from a long-ago frozen phase.
Yarrabubba Crater, a 43-mile-wide (70 kilometers) geological feature in Western Australia, is 2.229 billion years old, plus or minus 5 million years, a new study reports. That’s about half the age of Earth itself and 200 million years older than the previous record holder, the 190-mile-wide (300 km) Vredefort Dome in South Africa.
Intriguingly, the Yarrabubba impact appears to have occurred just as our planet started coming out of a “Snowball Earth” period, when much of the planet was covered by ice. And that may not be a coincidence, study team members said.
“The age of the Yarrabubba impact matches the demise of a series of ancient glaciations,” co-author Nicholas Timms, an associate professor in the School of Earth and Planetary Sciences at Curtin University in Western Australia, said in a statement.
“After the impact, glacial deposits are absent in the rock record for 400 million years,” Timms added. “This twist of fate suggests that the large meteorite impact may have influenced global climate.”
Ancient craters such as Yarrabubba are difficult to find on our active Earth. Many get buried when crustal plates dive beneath each other, and most others are worn away by wind and water over the eons.
Indeed, “Yarrabubba no longer even looks like a crater,” study lead author Timmons Erickson, from NASA’s Johnson Space Center in Houston and Curtin University’s School of Earth and Planetary Sciences, told Space.com.
But a different team of scientists — led by Francis Macdonald, now a geology professor at the University of California Santa Barbara — recognized Yarrabubba as such back in 2003, thanks to measurements of magnetic anomalies in the area and the presence of rocks shocked by an impact.
It was clear that the Yarrabubba strike occurred long ago, but its exact age had remained elusive until now. In the new study, which was published online today (Jan. 21) in the journal Nature Communications, Erickson and his colleagues analyzed tiny pieces of Yarrabubba’s shocked rock.
Specifically, the researchers studied grains of monazite and zircon that were recrystallized by the impact, measuring the amounts of uranium, thorium and lead contained in each. Monazite and zircon readily take up uranium but not lead when they crystallize, and uranium and thorium radioactively decay into lead at known rates. So, these measurements told the team how long ago that recrystallization occurred.
Yarrabubba’s age is intriguing, because a lot was going on 2.229 billion years ago. For example, photosynthesizing cyanobacteria had just started pumping large amounts of oxygen into Earth’s atmosphere, initiating a dramatic process known as the Great Oxidation Event.
The planet also came out of a deep freeze — one of multiple snowball phases Earth has experienced during its 4.5-billion-year history — around the time of the Yarrabubba impact. To see if these two events might possibly have been connected, Erickson and his colleagues performed computer simulations of the Yarrabubba strike.
This is not a crazy thought; after all, the catastrophic, dinosaur-killing impact of 66 million years ago is thought to have wrought much of its destruction via rapid and dramatic climate change.
The researchers’ models slammed a 4.3-mile-wide object (7 km) into a frigid Western Australian landscape, one covered by an ice sheet that ranged from 1.2 miles to 3.1 miles (2 to 5 km) thick in various runs. They found that such a strike would instantly vaporize between 23 cubic miles and 58 cubic miles (95 to 240 cubic km) of ice and cause up to 1,300 cubic miles (5,400 cubic km) of total melting.
This suggests that between 200 trillion lbs. and 440 trillion lbs. (90 trillion to 200 trillion kilograms) of water vapor, a potent greenhouse gas, were blasted into Earth’s upper atmosphere immediately after the Yarrabubba impact.
Not enough is known about the ancient Earth’s atmospheric structure and composition to confidently model how this injection of water vapor would have affected climate, Erickson and his colleagues stressed.
“Nevertheless, considering that Earth’s atmosphere at the time of impact contained only a fraction of the current level of oxygen, a possibility remains that the climatic forcing effects of H2O vapor released instantaneously into the atmosphere through a Yarrabubba-sized impact may have been globally significant,” they wrote in the new study.
Discovering and dating additional ancient craters could help answer such questions. And there should be more such features out there to find, Erickson said. After all, Earth got pummeled by far more impactors in its youth than it does now. (By the way, the new study does not present the evidence of the oldest known impact. Researchers have found ejecta — bits of rock blasted out by asteroid or comet strikes — that are up to 3.4 billion years old. But their associated craters have not been identified.)
And geologists could conceivably get windows onto an even deeper past than that afforded by Yarrabubba, Erickson said. Researchers probably can’t untangle the complicated history of the oldest known rocks on Earth, which are 4 billion years old, he said, but they might have some luck with the ancient nuclei known as cratons.
“They stretch back to 2.5 to 3.5 billion years old,” Erickson said. “I think, theoretically, it’s possible to find impact craters in that age range.”
Mike Wall’s book about the search for alien life, “Out There” (Grand Central Publishing, 2018; illustrated byKarl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter@Spacedotcom orFacebook.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
