Saturday, December 4

Astronomers map the asteroid’s 22-million-year journey to Earth | Asteroids


Astronomers have reconstructed the 22-million-year journey of an asteroid that passed through the solar system and exploded over Botswana, spewing meteorites across the Kalahari desert.

It is the first time that scientists have traced a shower of space rocks back to its origin, in this case Vesta, one of the largest bodies in the asteroid belt that surrounds the sun between Jupiter and Mars.

The six-ton ​​asteroid hit Earth’s atmosphere at 37,000 mph in June 2018 and broke over the central Kalahari game reserve, creating a fireball almost as bright as the sun. Immediate searches of the suspected landing site found a small meteorite, which was named Motopi Pan.

NASA researchers had tracked the dangerous object from as far away as the moon using telescopes in Arizona and Hawaii. After the impact, they asked astronomers in Australia to verify images of the SkyMapper Telescope in New South Wales, used to study black holes and the like, in case it had also captured the asteroid’s flight path. To the amazement of the researchers, it was.

“We would not have realized it if it had not been for the warning from the American discoverers, and it comes very close to us,” said Christian Wolf, an astronomer at the Australian National University. “Of course, it’s the Kalahari and I’ve never been there, but when your day job involves orienting yourself along a chain of black holes with an average step size of one billion light years between landmarks, the Kalahari is feels very close to your keyboard. “

Skymapper images of asteroid 2018LA in transit
Sky map images of asteroid 2018LA in transit. Photography: Brochure

Snapshots of the asteroid, called 2018LA, from three telescopes placed widely apart on Earth’s surface allowed astronomers to reconstruct the rock’s path and determine its origin. The trail led to Vesta, a 300-mile-wide asteroid that is occasionally visible without a telescope.

Armed with a good idea of ​​the asteroid’s trajectory, the scientists were able to refine the location of its landing in the game reserve. This led to expeditions that recovered more than 20 other meteorites spread over a 3-mile patch of land.

Mineralogical analyzes of the fragments suggest that the chunk of rock that became 2018LA was originally buried deep within Vesta’s surface, but was blown into space during an impact that left a crater in the asteroid about 22 million years ago. .

The ejected space rock wandered the solar system, its surface hit by cosmic rays, until it fell into the gravitational arms of the Earth and collapsed to the ground.

Laboratory tests showed that the oldest grains within the discovered meteorites date back to 4.56 billion years ago, a time when the solar system was still forming from a super-hot disk of interstellar gas and dust. Details are published in Weather and planetary science.

“This is a really exciting study,” said Ashley King, a planetary scientist at the Museum of Natural History who was not involved in the work. “It is only the second time a rock has been detected in space before entering Earth’s atmosphere and eventually ending up as meteorites on the ground.”

He said the recovered rocks were a mixture of types of igneous meteorites known as HED, an acronym for howardites, eukrites and diogenites, which were long thought to be fragments of the asteroid Vesta. The asteroid was visited by NASA’s Dawn mission a few years ago.

“Because the team tracked the rock from space to the impact site, they were able to calculate a very precise orbit that is consistent with an origin near Vesta, providing one of the best links we have between an asteroid and meteorites,” he said. King. “Knowing where meteorites come from gives us context for how they formed and is really important for understanding the history of our solar system.”


www.theguardian.com

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