Scientists studying a shard meteorite have found evidence that it comes from a previously unknown asteroid that could be the size of the dwarf planet Ceres. The meteorite, Almahata Sitta (AhS), fell to Earth in 2008, and the researchers studied its composition to learn more about the asteroid from which it came.
A meteorite is the name for a piece of debris that falls on Earth, and this particular one comes from an asteroid, a small object orbiting the sun. Asteroids are typically much smaller than planets and are usually clustered in the asteroid belt between Jupiter and Mars. Within this asteroid belt, the largest known object is a dwarf planet called Ceres.
Now the new evidence suggests that an asteroid the size of Ceres could still exist elsewhere in the solar system.
The Southwest Research Institute (SwRI) researchers looked at a small sample of meteorite AhS to learn more about the body from which it came. “We were assigned a 50 milligram AhS sample to study,” explains Dr. Vicky Hamilton, lead author of the article, in a statement. “We mounted and polished the small shard and used an infrared microscope to examine its composition. Spectral analysis identified a range of hydrated minerals, particularly amphibole, indicating intermediate temperatures and pressures and a prolonged period of aqueous change on a parent planoid at least 400 and up to 1100 miles in diameter. “
This means that the asteroid from which the sample came must have been large and formed in the presence of water. It is rare to find the mineral amphibole in this type of meteorite, called a carbonaceous chondrite (CC) meteorite, making AhS an unusual specimen and one particularly helpful for learning more about the early solar system.
We may well learn more about the early solar system from the study of two recently visited asteroids, Ryugu and Bennu. Ryugu has been visited by Japan’s Hayabusa 2, who recently returned a sample to Earth, and Bennu has been visited by NASA’s OSIRIS-REx, which is due to return a sample in 2023.
These samples, collected directly from asteroids, may differ from those such as AhS that fell to Earth and were affected by their travel through the atmosphere.
“If the compositions of the Hayabusa2 and OSIRIS-REx samples are different from what we have in our meteorite collections, it could mean that their physical properties are not causing the processes of ejection, transit and penetration through Earth’s atmosphere. survive. in their original geological context, ”said Hamilton. “However, we think there are more carbonaceous chondrite materials in the solar system than represented by our collections of meteorites.”
The findings are published in the journal Nature.
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