A team led by SwRI will search for meteoric evidence for an previously unknown asteroid

SAN ANTONIO – December 21, 2020 – A team of scientists led by the Southwest Research Institute has identified a potentially new parent meteorite asteroid by examining a small piece of meteorite that arrived on Earth from twelve years ago. The composition of a piece of the meteorite Almahata Sitta (AhS) reveals that its parent’s body was an asteroid about the size of Ceres, the largest in the main asteroid belt, and formed in presence of water under temperature and moderate pressures.

“Carbonaceous chondrite (CC) meteorites record geological activity in the earliest stages of the Solar System and provide insight into the history of their parent groups,” said SwRI staff scientist Dr. Vicky Hamilton, the first author of a paper published there Astronomy of nature carrying out this research. “Some of these mineral-controlled meteorites provide evidence for exposure to water at low temperatures and pressures. A combination of other meteorites indicates warming without water. Evidence for metamorphism is the presence of water at moderate conditions. has been virtually absent, so far. “

Asteroids – and the meteors and meteorites that sometimes come from them – have survived the creation of our Solar System 4.6 billion years ago. Most live in the main asteroid belt between the orbits of Mars and Jupiter, but crashes and other events have broken up and leftovers have entered the Inner Solar System. In 2008, a 9-ton diameter, 13-foot asteroid entered the Earth’s atmosphere, exploding into about 600 meteorites across Sudan. This marked the first time scientists had predicted the effects of an asteroid before entering and allowed 23 pounds of samples to be retrieved.

“We were given a 50-milligram sample of AhS for analysis,” Hamilton said. “We mounted and polished the tiny shard and used an infrared microscope to examine its writing. Spectrum analysis identified a range of hydrated minerals, particularly amphibians, which indicate moderate temperatures and pressures and a long period of aqueous change of a parent asteroid at at least 400, and up to 1,100, miles in diameter.

Amphibians are very rare in CC meteorites, as they have not previously been identified as partially discovered in the Allende meteorite. “AhS is a serendipitous source of information about early Solar System products that are not represented by CC meteorites in our collections,” Hamilton said.

An orbital spectroscope of Ryugu and Bennu asteroids visited by Hayabusa2 from Japan and NASA’s OSIRIS-REx spacecraft this year are consistent with strongly modified CC meteorites and suggest that the two asteroids are different from the best known meteorites in terms of irrigation status and evidence for large, low scale. -temperature hydrothermal processes. These missions have collected samples from the surface of the asteroids for return to Earth.

“If the samples of Hayabusa2 and OSIRIS-REx differ from what we have in the collections of meteorites, it could mean that their physical properties cause them to not survive processes. ejection, movement and entry through the Earth’s atmosphere, at least in their original geological context, “said Hamilton, who also serves on the OSIRIS-REx science team.” However, we believe that there is more carbonaceous chondrite materials in the Solar System than are represented by the accumulations of meteorites. “

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For more information, go to https: //www.swri.org /planetary science.