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Astronomy: Massalia asteroid family could be a major source of meteorites (N&V)
The most common types of meteorites that reach Earth are likely to have come from just a few asteroid breakup events — some relatively recent — according to two papers published in Nature.
A class of meteorites called ordinary chondrites make up around 80% of meteorites that have impacted Earth, including those involved in an intense period of impact events approximately 466 million years ago that appear to have triggered an ice age. Previous research has demonstrated that about 70% of meteorites on Earth have compositions known as H and L chondrites. Argon–argon dating of L chondrite meteorites on Earth revealed that these samples likely originated from the catastrophic disruption of a single asteroid that experienced a supersonic impact approximately 470 million years ago.
Michael Marsset and colleagues compiled spectroscopic data of asteroids in the main belt between Mars and Jupiter and found that a group of asteroids known as the Massalia family is closely similar to the composition of L chondrite meteorites on Earth. Through computer modelling, the researchers propose that an impact event broke up an L chondrite asteroid approximately 450 million years ago, forming the Massalia family and providing the debris that fuelled the meteorite influx.
In a second paper, Miroslav Brož and colleagues go on to show that the current influx of H and L chondrite meteorites was likely caused by three more recent breakups. These events occurred about 5.8, 7.6, and 40 million years ago, and saw the destruction of asteroids larger than 30 kilometres in diameter. More specifically, Brož and colleagues deduced that the collisional formation of the relatively young Karin and Koronis asteroid families, and a second collisional event (about 40 million years ago) in the older Massalia family, explain the majority of the meteorites currently falling to Earth.
These findings offer insights into the mysteries surrounding where the most common meteorites that have impacted Earth so far came from and how those impacts may have shaped Earth’s history.
