There’s a giant asteroid somewhere in the solar system, and it hurled a big stone at it Soil.
The evidence for this mysterious space rock comes from a diamond-studded meteor that exploded over Sudan in 2008.
NASA had the 9 tons (8,200 kilograms), 13 feet (4 meters) meteor headed for the planet well before the collision, and researchers turned up in the Sudanese desert to collect an unusually rich amount of remains. Now, a new study of one of those meteorites suggests the meteor may have broken off from a giant asteroid – one roughly the size of the dwarf planet Ceres, the largest object in the asteroid belt.
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Like about 4.6% of Earth’s meteorites, this one – known as Almahata Sitta (AhS) – is made from a material known as carbonaceous chondrite. These black rocks contain organic compounds as well as a variety of minerals and water.
The mineral composition of these space rocks provides clues to the ‘parent asteroid’ that spawned a particular meteor, researchers said in a statement.
“Some of these meteorites are dominated by minerals that provide evidence of exposure to water at low temperatures and pressures,” said study co-author Vicky Hamilton, a planetary geologist at the Southwest Research Institute in Boulder, Colorado, in the statement. “The composition of other meteorites indicates heating in the absence of water.”
The team analyzed a small sample of 0.0018 ounces (50 milligrams) of AhS under a microscope and found that it had a unique mineral composition.
The meteorite was home to an unusual array of minerals that form at “intermediate” temperatures and pressures (higher than what you’d find in a typical asteroid, but lower than the inside of a planet). One mineral in particular, amphibole, also requires long-term exposure to water to develop.
Amphibole is common on Earth, but it has only appeared in trace amounts once before in a meteorite known as Allende – the largest carbonaceous chondrite ever found, which fell in Chihuahua, Mexico, in 1969
The high amphibole content of AhS suggests that the fragment has broken off an overlying asteroid that has never left meteorites on Earth before.
And samples brought back from the asteroids Ryugu and Bennu by Japan’s Hayabusa2 and NASA’s OSIRIS-REx probes, respectively, are likely to reveal more space rock minerals rarely found in meteorites, the researchers wrote in their study.
Perhaps some types of carbonaceous chondrite just won’t survive the dive through the atmosphere, Hamilton said, and that kept scientists from studying a flavor of chondrite that may be more common in space.
“We think there are more carbonaceous chondrite materials in the solar system than represented by our collections of meteorites,” she said.
The article was published in the magazine Dec. 21 Nature astronomy.
Originally published on Live Science.