Astronomers find a piece of comet inside a meteorite

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The beginnings of the solar system are difficult to reconstruct from our point of view, billions of years later. Now a team of scientists has discovered a tiny piece of an ancient comet in an ancient meteorite. They say that it highlights the beginnings of the solar system, while the planets were still forming.

The new research detailing this discovery was published in Nature Astronomy and its lead author is Larry Nittler of the Carnegie Institution. It is centered on an old meteorite called LaPaz meteorite, which was found in the LaPaz ice field in Antarctica. It is a carbonaceous chondrite, one of the most primitive meteorites we know. About 5% of meteorites observed are of this type.

Meteorites observed are different from so-called "found meteorites". Observed meteorites are seen by a person, or increasingly, by an automated observer, and are found and examined before they are subject to severe weathering. They are in a more pristine state than anything that could have been on the surface of the Earth for years, decades, or even longer. They are therefore desirable scientific objects.

The LaPaz meteorite is a 42-gram rock found by ANSMET, the Antarctic Meteorite Research, in 2002. It is in near perfect condition and has not been modified by the weather. Its official name is LaPaz IceField 02342.

A slice of the LaPaz 02342 meteorite with white arrow showing the carbon-rich fragment from an old comet. Image credit: Carles Moyano-Cambero
A slice of the LaPaz 02342 meteorite with white arrow showing the carbon-rich fragment from an old comet. Image credit:
Carles Moyano-Cambero

Nittler and his team studied the meteorite by cutting it into a thin layer and subjecting it to sophisticated chemical and isotopic analysis. Inside, they found something unusual. There were some very primitive materials that looked like old extraterrestrial dust particles that probably came from comets that formed on the distant edges of the solar system.

The asteroid develops gradually by accumulating more and more material. They are also exploded as a result of collisions, which happened much earlier in the early days of the solar system. About 3 to 3.5 billion years after the formation of the solar system, while the Earth was still becoming it, this tiny piece of comet only a tenth of a millimeter in diameter was captured by the 39; asteroid.

Then, at one point, the asteroid broke and LaPaz 02342 fell to Earth, his little passenger being shielded from destruction as he was crossing the road. ;atmosphere.

Their analysis showed that this tiny passenger probably came from the icy regions of the solar system, the same place where the objects of the Kuiper belt are and from which come many comets.

An illustration showing how a fragment of cometary construction material was swallowed by an asteroid and stored inside a meteorite, where it was discovered by a team of scientists led by Carnegie. The picture is courtesy of Larry Nittler and NASA.
An illustration showing how a fragment of cometary construction material was swallowed by an asteroid and stored inside a meteorite, where it was discovered by a team of scientists led by Carnegie. The picture is courtesy of Larry Nittler and NASA.

"Because this sample of cometary building block material had been swallowed by an asteroid and preserved inside this meteorite, it was protected from the damage caused by the penetration of the Earth's atmosphere," he said. explained Nittler in a press release. "This gave us a glimpse of materials that would not have survived to reach the surface of our planet by themselves, helping us understand the chemistry of the solar system in the beginning."

The story of this event helps to shed light on the originally formed solar system. Carbonaceous chondrites, such as LaPaz 02342, have formed in an area beyond Jupiter, while comets have formed in the far frozen fringes of the solar system. The surrounding gas trail caused migration of the tiny comet particle from the distant solar system to the formation zone of the carbonaceous chondrites.

The existence of this tiny rock trapped in a meteorite shows how the structure of the early solar system was shaped in the early days of Earth and other planets.

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