Scientists have discovered an 8cm meteorite that is chemically different from any of the 50,000 kinds of meteorites that have been held in collections by researchers.
The meteotite, called Österplana 65, was discovered in a limestone quarry in Thorsberg, Sweden, that produces floor tiles.
Researchers said that the dating of the rocks suggests that the meteorite’s parent body of rock was involved in a huge collision in the asteroid belt between Mars and Jupiter around 470 million years ago.
Birger Schmitz and colleagues tell the journal Nature Communications that this was the same collision that produced a large class of the rocks known as L chondrites.
The L chondrites are present in significant quantities in the Thorsberg sediments of Ordovician age.
Dr Schmitz’ team recovered more than a hundred of these “fossil” objects in the quarry.
The Ordovician period in the one in Earth history when the Northern Hemisphere was submerged under water and marine lifeforms such as the trilobites were flourishing.
However, the new meteorite is distinct because of its oxygen and chromium signatures.
“We’ve been hunting these Ordovician meteorites for 25 years. We found 50, then 60, then 70 – and it was getting boring,” Dr Schimtz told BBC News.
“Then in 2011, we found one meteorite that was entirely different. For a long time we called it ‘the mysterious object’ because it didn’t resemble anything. For five years, we have done all types of analysis and now we’re certain of what it is.”
The hypothesis of the researchers is that Öst 65 comes from the “second asteroid” in the collision, based on cosmogenic dating.
Cosmogenic dating reveals the length of the time for which the fresh surface of a broken object has been exposed to space radiation. The exposure to space radiation exposes the meteorite to high energy particles that generate isotopes in the rock.
The more of these isotopes that are present, the greater the time since the fragmentation event.
“We show that Öst 65 was liberated from its parent body at the same time as the L chondrites were released from their parent body, and that’s very strong empirical evidence that this new meteorite comes from the same impact,” said Dr Schmitz.
Different types of meteorites
The discovery of this meteorite shows that different types of meteorite have fallen to Earth.
The presence of different types of rocks shows the presence of a somewhat different Solar System to the one that existed 500 million years ago.
Dr Schmitz refers to his find as an “extinct meteorite”.
Dr Schmitz’ meteorite said,
“It used to be that they threw away the floor tiles that had ugly black dots in them. One of my co-authors on the paper, Mario Tassinari, contacted the quarry owners to ask them not to do that. The very first fossil meteorite we found was in one of their dumps.”