Evidence for this mysterious space rock comes from a diamond-encrusted meteor that exploded over Sudan in 2008.
NASA spotted 9 tons (8,200 kg), 13 feet (4 meters) meteor Heading towards the planet long before the collision, researchers appeared in the Sudanese desert to collect an unusually large number of remains. Now, a new study of one of those meteors suggests that the meteorite may have broken off from a giant asteroid – the size of the dwarf planet Ceres, the largest object in the asteroid belt.
Like about 4.6% of meteorites on Earth, this meteorite – known as Station Sita (AhS) – is made from a substance known as carbon 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 about the « parent asteroid » that gave birth to a particular meteor. The 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 Vicky Hamilton, a planetary geologist at the Southwest Research Institute in Boulder, Colorado, in the statement. « The formation of other meteorites indicates heating in the absence of water. »
The team analyzed a small sample of 0.0018 ounces (50 milligrams) of EFA under a microscope and found that it had a unique mineral composition.
The meteorite was harboring an unusual group of minerals that form at « average » temperatures and pressures (higher than what you would find in a typical asteroid, but lower than inside a planet). One mineral in particular, amphibole also requires long exposure to water to develop.
Amphibole is common enough on Earth, but it only appeared once before in trace amounts in a meteorite known as Allende – the largest carbon chondrite ever found, which fell in Chihuahua, Mexico, in 1969.
The high amphibole content of AhS indicates that the fragment fractured an original asteroid that had not left meteors on Earth before.
In their study, the researchers write that samples brought from the asteroids Ryugu and Bennu by NASA’s Hayabusa2 and OSIRIS-REx probe, respectively, will likely reveal more space-based rock minerals that are rarely seen in meteorites.
Hamilton said: Perhaps some types of carbonic chondrites do not survive plunge into the atmosphere either, and this has prevented scientists from studying the flavor of chondrites that may be more common in space.
« We think there are more carbon chondrites in the solar system than there are our groups of meteorites, » she said.
The paper was published December 21 in the journal Natural Astronomy.
Originally published on Live Science.