Strange, dark-veined meteorites rained down on Earth when a fireball exploded over Chelyabinsk, Russia, in February 2013. The origin of these unusual meteorites has remained a mystery, but now, planetary scientists have discovered a possible source: a mile-and-a-half-long near-Earth asteroid.
Scientists know that the dark streaks across the Chelyabinsk meteorites are caused by a process called shock darkening. Yet only around 2% of a common type of meteorite called chondrite meteorites show signs of shock darkening, and the source of these space rocks has remained a mystery.
Now, scientists have identified the asteroid 1998 OR2 as a potential source of shock-darkened meteorites. The near-Earth asteroid was discovered in July 1998 by the Near-Earth Asteroid Tracking program at NASA’s Jet Propulsion Laboratory. Its last close approach to Earth was in April 2020, when the space rock passed within 3.9 million miles (6.3 million kilometers) of our planet.
Although that may not seem very close, NASA still considers 1998 OR2 “potentially hazardous” because changes to the asteroid’s orbit over the next 1,000 years could make it a risk to Earth.
Meteorites are created when pieces of an asteroid like 1998 OR2 break away and enter Earth’s atmosphere. The discovery that shock-darkened meteorites can originate from a near-Earth asteroid hints at the varying material strength of asteroids and has implications for protecting Earth against a potential impact, the researchers said.
“Shock darkening is an alteration process caused when something impacts a planetary body hard enough that the temperatures partially or fully melt those rocks and alter their appearance both to the human eye and in our data,” Adam Battle, a graduate student in planetary science at the University of Arizona and lead author of the study, said in a statement (opens in new tab). “This process has been seen in meteorites many times but has only been seen on asteroids in one or two cases way out in the main asteroid belt, which is found between Mars and Jupiter.”
Vishnu Reddy, a planetary scientist at the University of Arizona and co-author of the new study who detected shock darkening on these main-belt asteroids, said that it’s a much more common phenomenon on asteroids than meteorites. “Impacts are very common in asteroids and any solid body in the solar system because we see impact craters on these objects from spacecraft images,” he said in the statement. “But impact melt and shock-darkening effects on meteorites derived from these bodies are rare.”
Reddy, who co-leads the Space Domain Awareness lab at the Lunar and Planetary Laboratory, added that finding a near-Earth asteroid dominated by this process has implications for impact hazard assessment.
“Adam [Battle]’s work has shown that ordinary chondrite asteroids can appear as carbonaceous in our classification tools if they are affected by shock darkening,” Reddy said. “These two materials have different physical strengths, which is important when trying to deflect a hazardous asteroid.”
Is asteroid 1998 OR2 chondrite or carbonaceous?
Reddy, Battle and their team used the Rapid Astronomical Pointing Telescopes for Optical Reflectance Spectroscopy (RAPTORS) atop the Kuiper Space Sciences Building on the University of Arizona campus to observe the asteroid 1998 OR2.
The team collected data on 1998 OR2’s surface composition, with the asteroid visually appearing as an ordinary chondrite asteroid, a type of space rock that is light in color and contains the minerals olivine and pyroxene. But an asteroid classification tool determined that 1998 OR2 appeared to be a carbonaceous asteroid ; these space rocks are dark and featureless compared with chondrite asteroids.
The team then set about investigating the reason for this discrepancy and determining the correct classification.
“The mismatch was one of the early things that got the project going to investigate potential causes for the discrepancy,” Battle said.
They eliminated the possibility that exposure to the space environment had caused changes in the asteroid’s surface, as this process, called space weathering, would have left the space rock slightly reddened.
The team concluded that shock darkening was responsible for the disparity between the two analysis methods, because the shock darkening process can obscure olivine and pyroxene while darkening the asteroid’s surface, thus making it look like a carbonaceous asteroid.
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“The asteroid is not a mixture of ordinary chondrite and carbonaceous asteroids, but rather it is definitely an ordinary chondrite, based on its mineralogy, which has been altered — likely through the shock darkening process — to look like a carbonaceous asteroid to the classification tool,” Battle said.
Shock darkening of asteroids was first theorized in the late 20th century but wasn’t an intense area of study until the 2013 Chelyabinsk fireball seeded Earth with shock-darkened meteorites.
Interest in shock darkening grew after Reddy found asteroids affected by the process in the main asteroid belt. This new discovery showing evidence of the process in a near-Earth asteroid could further increase interest in shock darkening, the team said.
The research was published Oct. 4 in The Planetary Science Journal and presented at a conference held this week by the American Astronomical Society’s Division of Planetary Sciences..
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.
