A new type of meteorite, which fell to Earth about 470 million years ago, has been discovered in a limestone quarry in Sweden. The finding is described a new study published in Nature Communications this week and helps us to reconstruct the history of meteorites - debris from space that occasionally falls to Earth - in our Solar System.
One of the most common types of meteorites are known as L type chondrites, which are thought to be derived from a larger parent body that underwent a large collisional event with an asteroid about 470 million years ago. However, no evidence for this colliding asteroid had been found until now.
Birger Schmitz and colleagues found a new type of meteorite (under ten centimetres in length) which they named Ost 65 in a Swedish quarry, among over 100 L chondrites which fell to Earth about 470 million years ago. In order to classify the meteorite, the authors used a combination of petrological and chromium and oxygen isotopic analyses, and found that it is geochemically and petrologically distinct from all known meteorite types that have fallen to Earth to date. Using a dating technique known as cosmic-ray exposure, they showed that the meteorite’s age is within one million years of the L chondrite collisional event. The authors therefore suggest that this single meteorite may represent the remains of the parental asteroid which collided with and was responsible for the disruption of the large L chondrite parental body. They believe that the Ost 65 parental asteroid may have largely been destroyed during the collision with the L chondrite body, and that this is why this type of meteorite has not been recovered on Earth before.
Although the parent asteroid may have been largely destroyed, the possibility remains that its remnants could still be out in space along with the L chondrites that regularly fall to Earth.