Piece of comet found hidden inside a meteorite

Scientists have found a cometary building block in an unexpected place: deep inside a meteorite, according to a new article.

The researchers reported finding a 0.1-mm-high carbon-rich rock fragment inside a meteorite. They interpreted it as a piece of comet captured during the earliest ages of the solar system, when planets were still forming, then brought to Earth. We simply do not have many samples of comets on Earth to study, which makes this potential discovery very exciting.

The fragment "could be characteristic of cometary materials that are not represented in meteorite collections as they are too fragile to survive the entry of the atmosphere", according to the paper published today in Nature Astronomy.

Let's start by defining a few points: a meteorite is a rock of space that has already landed on the surface of the Earth. This could be part of an asteroid, rocky bodies that are thought to come from remains of matter in the solar system that did not transform into planets, or from a comet, which are similar to asteroids but contain volatile elements a coma) and a tail under the influence of the sun. These are clumsy terms, but they describe what astronomers are most interested in: the formation of the solar system and the way in which the different objects we see today can tell this story.

The researchers analyzed an Antarctic meteorite called LAP 02342, which is interesting because it was little altered or eroded during its passage on Earth. They analyzed it under an electron microscope, revealing the tiny, carbon-rich section that differed from the rest of the otherwise typical meteorite. Its composition corresponded to that of other interplanetary dust particles that astronomers previously explained as coming from comets.

Humans were not there to look at this form of meteorite, so we can not determine the exact origin of the fragment. But researchers have ideas. it was perhaps the earliest stage of a comet, forming from materials in the ultraperipheral region of the solar system, the icy Kuiper Belt. But the formation of the comet was stopped in one way or another and this piece was captured by an asteroid that moved towards the Sun and eventually hit the Earth.

Hopefully scientists will soon find more of these carbon particles in asteroids to tell more about the origin of the solar system. According to the paper, researchers specializing in ancient meteorites looking for these carbon-rich fragments "might prove useful for deepening our understanding of the full range of primitive astromaterials of the early solar system".