Researchers find rarest groups of meteorites originating as far out as Neptune

An international team of scientists has been exploring the samples of asteroid Ryugu brought back to Earth in 2020 by Hayabusa2 and may have stumbled upon their source, according to a press release published by the Natural History Museum on Thursday.

An extremely rare group of meteorites

“Carbonaceous chondrites, such as the Winchcombe meteorite which fell to Earth and was retrieved in Gloucestershire in 2021, are an extremely rare group of meteorites which have been known to contain organics and amino acids – ingredients for life. They are the most primitive and pristine materials of the solar system and can provide unique information on where water and the building blocks of life were formed, and what planets are made from,” stated the press release.

In their latest research, the astronomers discovered that Ryungu was among the group of asteroids known as the Cb-type which formed billions of kilometers away from Earth, towards the edge of the Sun's influence. The celestial objects would have been located in a region of space named the Kuiper Belt, or perhaps even further into space.

Professor Sara Russell, a Senior Research Lead at the Museum who co-authored the paper, says, “It's only within the last decade we've begun to appreciate just how far objects in the solar system can move towards, and away from, the Sun.”

“While there is general acceptance that material from the outer solar system could have been moved inwards by the giant planets, this is one of the first studies which suggests the asteroid belt contains material originating as far out as Neptune. This adds an extra layer of detail to our knowledge of how the solar system formed.”

Searching for the parent bodies

The purpose of the research was to establish whether Cb-type asteroids, such as Ryugu, could be the parent bodies of a rare group of meteorites known as CI chondrites. In order to truly help astronomers understand the solar system, the formation location of asteroid remnants needs to be known. Determining where they originated from is crucial to answering some of the biggest questions about space, our universe and beyond.

The scientists have now concluded that both Ryugu and the CI chondrites came from the same region of space and could have even originated from the same celestial object.

“By comparing the forms of iron in both the asteroids and meteorites, we learnt that Ryugu is a remarkably close match to CI chondrites. These are the rarest type of carbonaceous meteorite, and I'm really excited as the type specimen, Ivuna, is within the Museum's collections,” said Russell.

“This discovery is very exciting for me as it means that the Museum's meteorite collection is sampling the whole of our solar system. Along with other types of meteorites, such as the enstatite chondrites from the inner solar system and ordinary chondrites from the asteroid belt, we can study huge swathes of space from here in London.”