Asteroid 2018 LA Likely Came From Vesta, Researchers Find | Planetary science, space exploration

2018 LA, a 1.5m-wide asteroid that harmlessly disintegrated over Botswana, Africa, just hours after its discovery on June 2, 2018, is just the second asteroid detected in the space before its impact on the earth. According to new research, 2018 LA originated from the inner main asteroid belt, where the large asteroid Vesta is located, and the impact that ejected 2018 LA into orbit towards Earth occurred about 23 million years ago. ‘years.

The asteroid 2018 LA in space (top left image from Catalina Sky Survey) and the first 23 meteorites recovered from the ground as photographed in situ (the scale of each figure is approximately 4 x 4 cm). Meteorites are displayed in order of discovery (MP-01 top left, MP-23 bottom right). Image Credit: Jenniskens et al., doi: 10.1111 / maps.13653.

“This is only the second time we’ve spotted an asteroid in space before it hits Earth above Earth. The first was the 2008 asteroid TC3 in Sudan ten years earlier, ”said Dr Peter Jenniskens, meteorologist at the SETI Institute.

Dr Jenniskens and his colleagues were able to triangulate the location of the LA 2018 Fireball main torch over Botswana.

Twenty-one days after the fall, foot excavations in the Central Kalahari Game Reserve (CKGR) in Botswana initially recovered a single meteorite weighing 17.92 g, named “Motopi Pan” (MP-01).

The researchers then found 22 more fragments of LA 2018 at the bottom of the CKGR.

“One of these meteorites is called Motopi Pan after a local water point. This meteorite is a national treasure of Botswana, ”said Dr Mohutsiwa Gabadirwe, a geoscientist at the Botswana Geoscience Institute.

Non-destructive analysis has shown that Motopi Pan belongs to the Howardite-Eucrite-Diogenite (HED) group of meteorites, known to have probably originated from Vesta, which was recently studied in detail by NASA’s Dawn mission.

“We were successful in measuring the metal content as well as securing a reflectance spectrum and X-ray elemental analysis of a thin crusted portion of the interior of the exposed meteorite,” said Dr Tomas Kohout, researcher at the University of Helsinki.

“All the measurements added up well and indicated values ​​typical of HED-type meteorites.”

Dynamic studies have shown that the 2018 LA orbit is consistent with an origin in the inner part of the asteroid belt where Vesta is located.

The asteroid was delivered into an orbit impacting Earth via the resonance located in the inner face of the asteroid belt.

“Another HED meteor fall that we studied in Turkey in 2015, called Sariçiçek, impacted an equally short orbit and produced mostly small meteorites of 2-5 grams,” noted Dr Jenniskens.

“We have studied the petrography and mineral chemistry of five fragments of LA 2018 and confirmed that they belong to the HED group,” said Dr Roger Gibson, researcher at Witts University.

“Overall, we classified the material in asteroid 2018 LA as Howardite, but some individual fragments had more affinity for diogenites and eucrites.”

A previous hypothesis has proposed that Sariçiçek originated from Vesta in the collision that created the Antonia impact crater imagined by the Dawn spacecraft.

Still showing visible ejecta blanket, this young crater formed about 22 million years ago.

A third of all HED meteorites that fall to Earth were ejected 22 million years ago. Does Motopi Pan originate from the same crater?

“Measurements of noble gas isotopes and radioactive isotopes have shown that this meteorite has also been present in space as a small object for about 23 million years, but that it would take or take 4 million years,” it could therefore come from the same source crater on Vesta, ”said Dr. Kees Welten, researcher at the University of California, Berkeley.

The teams results were published in the journal Meteorites and planetary science.

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Peter Jenniskens et al. The impact and recovery of the asteroid 2018 LA. Meteorites and planetary science, published online 23 April 2021; doi: 10.1111 / maps.13653


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