Meteorites are a bit like fruitcake: pieces of ore joined by a stone matrix. These mineral inclusions may contain some fascinating insights into the solar system, but now scientists have found something they had never seen before.
In a meteorite recovered from Antarctica in 2002, there is a small, old strip of kite building blocks: enclosed, according to researchers, like an insect in amber.
The meteorite is called LaPaz Icefield 02342 (LAP 02342 for short), and is a type of meteorite known as carbonaceous chondrite.
Meteorites come in a variety of types, separated from larger pieces of space rock such as asteroids or even planets, and sent through space until they collide with Earth, after surviving the often explosive effects of entry to the Earth. atmosphere.
Its composition can vary, and that is used for meteorite clbadification. Carbonaceous chondrites are among the most primitive, thought to originate from the asteroids that formed about 4.5 billion years ago, when the solar system was also forming, beyond the orbital range of Jupiter.
Comets were also formed from the same protoplanetary disk of dust and gas that surrounded the newborn Sun, but much farther than the asteroids, so its composition is different. They have much more water ice: that is what the famous tail creates when they approach the Sun. And they have much more carbon.
The team was not really looking for cometary trifles. Meteorites are a kind of time capsule for the early Solar System, rich in presolar grains, and information on the heating and chemical processes present during the formation of the system.
But the giblets of the comet are what they have.
(Larry Nittler / Carnegie Institution for Science)
"When I saw the first electronic images of the carbon-rich material," said cosmochemist Jemma Davidson of Arizona State University, "I knew we were seeing something very strange, it was one of those exciting times for those who live as a scientist."
That tiny carbon-rich splinter, measuring only a tenth of a millimeter, had strong similarities to interplanetary dust particles and micrometeorites that are thought to have originated in comets that formed in the Kuiper Belt in the icy neighborhoods of the Solar System.
The team performed an isotopic badysis of the splinter and concluded that it probably formed in the same place and in the same way.
Its inclusion in a meteorite suggests that it must have migrated inward from this initial position, slowly approaching the Sun until it reached the region where the carbonaceous chondrites formed.
Then, about 3 to 3.5 million years after the formation of the Solar System, this microscopic splinter somehow, perhaps through a collision, was incorporated into the asteroid that would fragment to produce LAP 02342.
The butte of the comet has opened a window to the dynamics and chemistry of the primitive Solar System, and the chemistry of the protoplanetary disk at various distances.
"Because this sample of cometary building block material was swallowed up by an asteroid and conserved within this meteorite, it was protected from the ravages of entry into Earth's atmosphere," said cosmochemist Larry Nittler of the Carnegie Institute. for Science.
"He gave us a look at the material that would not have survived to reach the surface of our planet by itself, helping us to understand the chemistry of the primitive solar system."
The research has been published in. Nature astronomy.