A team of scientists led by Southwest Research Institute has identified a new meteorite parent asteroid by studying the Almahata Sitta meteorite (AhS).
On October 6th, 2008, a small asteroid 2008 TC3 was discovered by an automated telescope. The 9-ton, 13 feet diameter asteroid was tracked closely as it entered the Earth’s atmosphere and exploded above northern Sudan’s Nubian Desert. Almahata Sitta is the first case in which meteorites have been tracked in space, during their entry into Earth’s atmosphere and have been recovered.
Analysis of the Almahata Sitta meteorite suggests that its parent asteroid was roughly about the size of Ceres and formed under intermediate temperatures and pressures in the presence of water. Ceres, at about 1000kms across, is the largest object in the asteroid belt between the orbits of Mars and Jupiter. Asteroids are remanents of our solar system formation some 4.6 billion years ago and provide insights into our planets and moons’ formation.
In the research published in Nature Astronomy, the first author and SwRI Staff Scientist Dr. Vicky Hamilton said that the meteorites’ mineral composition provides evidence of water exposure. Meteorites dominated by minerals result from exposure to water at low temperatures and pressures, whereas others point to heating in the absence of water. However, this is the first time metamorphism in the presence of water at intermediate conditions has been observed.
The AhS meteorite belongs to the Carbonaceous chondrite (CC) meteorites, which account for about 4.6% of all the meteorite falls. The spectral analysis of AhS meteorite identified a range of hydrated minerals, particularly amphibole, indicating prolonged exposure to water and intermediate temperatures and pressures on its parent. Amphiboles are especially rare in a CC meteorite, and a trace component was found previously in the Allende meteorite.
Orbital spectroscopy of asteroids Ryugu and Bennu suggests that they differ from known meteorites in terms of hydration state and indicates large-scale, low-temperature hydrothermal processes.
NASA’s OSIRIS-Rex and Japan’s Hayabusa2 visited Ryugu and Bennu, respectively, and collected surface samples to return to Earth. According to Hamilton, if their composition is different from our known collection of meteorites, it could affect their survival process of the ejection, transit, and entry through Earth’s atmosphere.
The scientists think that there are more CC materials in the Solar System than our sample collection suggests.
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