Scientists discover completely new type of meteorite
Scientists at UC Davis believe they have made the first ever discovery of an ‘extinct meteorite’ – a meteorite of a type that no longer falls to Earth. The find could revolutionize thinking about the evolution of life on our planet.
Most of the rocks that fall from space, around 85 percent, are known as ordinary chondrites. They consist of round pellets called chondrules, which form when molten mineral droplets quickly cool in space, and are thought to come from rocky asteroids
Around half of these ordinary chondrites are L-types, and about 470 million years ago there was at least a hundredfold increase in the number of L-types that fell to Earth. This suggests the parent asteroid of all the L-type chondrites experienced a major collision with another asteroid around that time.
This coincided with the Ordovician Period, during which coral reefs first appeared and other major changes in marine life diversity took place. The lead author of a study into the extinct meteorite, Birger Schmitz, a geologist at Lund University in Sweden, explained that the two events may be related.
“If we see that changes in the asteroid belt correlate with changes in Earth’s biosphere or climate, then there is probably a connection and we will be able to better tie Earth’s history to the history of the solar system,” Schmitz told Space.com.
“Earth scientists have for the past 200 years had a tendency to look on Earth as a closed system, but the discovery of the asteroid impact that killed off the dinosaurs 65 million years ago made at least some earth scientists understand that the history of life and Earth is connected to the astronomical realm.”
“The single meteorite that we found on the Ordovician seafloor is of a type that we do not know of from today’s world,” he added. “This hints that the types of meteorites that fell on Earth in the ancient past were very different than those falling today.”
Credit: Nature Communications
Revising understanding of how the solar system formed
The newly uncovered meteorite, which is about 3.15 inches (8 centimeters) long and was found in a quarry near the Swedish village Österplana, is thought to be a remnant of the asteroid that smashed into the parent of the L-type chondrites. The quarry is also home to roughly 100 L-type chondrites of similar age.
The unique meteorite differs from others in its ratio of chromium to oxygen isotopes, as well as having grains of crystals known as spinels.
“For a long time we called the meteorite the ‘Mysterious Object’ because we could not understand what it was,” Schmitz said. It is now known as Österplana, or Ost 6.
A dating technique that measures exposure to cosmic rays was used to assess that the impact that created Ost 6 occurred around 1 million years before it fell to Earth, and the same applied to the impact that created the L-types. This led to the theory that the extinct meteorite was from the same impact that destroyed the parent of the L-type chondrites.
The asteroid of Öst 65 may have been almost completely destroyed during its collision with the progenitor of the L-type chondrites, perhaps explaining why its type has not been seen on Earth before.
“This is the first documented example of an extinct meteorite — that is, a type of meteorite that no longer falls on Earth today,” Schmitz said. “We knew of extinct animals, and it has been speculated that there is something like extinct meteorites, but this is the first one found.”
Our understanding of the very formation of the solar system may even be called into question by the find.
“We base our view of how the solar system formed and evolved on the meteorites that fall on Earth today,” Schmitz explained. “If these meteorites are not representative of what has been falling on Earth in the past, we have to take that into consideration when reconstructing how the original nebula condensed into solid planets and asteroids.”
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Image credit: UC Davis
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