A small asteroid crashed into Earth three years ago – and now scientists know where it came from. Researchers have traced the origins of the resulting rare meteorite fragments, which began the journey to Earth some 23 million years ago.
The asteroid, called 2018 LA, shot across the sky like a fireball before landing in Botswana on June 2, 2018. Researchers later recovered 23 meteorites from the Central Kalahari Game Reserve, a huge area known for its diverse fauna.
“The meteorite is named ‘Motopi Pan’ after a local waterhole,” Mohutsiwa Gabadirwe, senior curator of the Botswana Geoscience Institute, said in a statement, referring to the first sample they found. “This meteorite is a national treasure of Botswana.
Scientists first spotted the asteroid using the University of Arizona’s Catalina Sky Survey, which tracks asteroids as part of NASA’s planetary defense program. This was the second time scientists could study an asteroid in space before it reached Earth – usually they don’t know until it happens.
At the time, the asteroid was estimated to be around six feet in diameter, small enough to separate safely in Earth’s atmosphere. It arrived at the rapid speed of 38,000 miles per hour, according to NASA.
“This is only the second time we’ve spotted an asteroid in space before it hits Earth above Earth,” Jenniskens said. “The first was the 2008 asteroid TC3 in Sudan ten years earlier.”
By accurately mapping the orbit and path of the boulder-sized asteroid to Earth, as well as analyzing the samples at the University of Helsinki, the researchers determined that they belonged to the group Howardite-Eucrite-Diogenite (HED) meteorites, named for their composition. They published their results in the journal Meteoritics and Planetary Science.
This group of meteorites likely came from Vesta, the second largest asteroid in our solar system, located in the asteroid belt between Mars and Jupiter.
“Combining observations of the small asteroid in space with information gleaned from meteorites shows that it likely originated from Vesta, the second largest asteroid in our solar system and the target of NASA’s DAWN mission,” said the lead author Peter Jenniskens. “Billions of years ago, two giant impacts on Vesta created a family of larger and more dangerous asteroids. The recently recovered meteorites have given us a clue as to when these impacts might have occurred. “
Researchers now believe the Veneneia Impact Basin formed around 4.2 billion years ago.
Researchers observed more diversity than expected in the appearance of meteorites. They classified the asteroid as a breccia, a mixture of pieces of rock from various parts of Vesta.
“We have studied the petrography and mineral chemistry of five of these meteorites and confirmed that they belong to the HED group,” said co-author Roger Gibson. “Overall, we classified the material in asteroid 2018 LA as Howardite, but some individual fragments had more affinity for diogenites and eucrites.”
A third of all HED meteorites that arrive on Earth were ejected from the asteroid around 22 million years ago.
Further research “showed that this meteorite had also been in space as a small object for about 23 million years,” said Kees Welten of UC Berkeley, “but it takes about 4 million years ”.
Researchers say they are excited to uncover more secrets surrounding the mysterious asteroid Vesta. A more recent expedition, in November 2020, led researchers to locate another Motopi Pan meteorite – at 2.3 ounces, this is the largest find to date.
banner image – 2018 LA asteroid fragment recovered from the Central Kalahari Game Reserve in central Botswana. SETI INSTITUTE