Where did the meteorites that actually hit Earth come from? | Asteroids

Meteorites – rocks that fall to Earth from space – strike our planet from its birth, about 4,500 million years ago, until today, often causing minor damage, but occasionally causing catastrophes. But where exactly do these space rocks come from? New research has the answer.

By studying the composition of the meteorites that have landed over the years and the asteroids that inhabit our solar system, astronomers have determined that about 70% of known meteorite impacts come from just three families of asteroids that are found in the large asteroid belt of the Earth's solar system between Mars and Jupiter.

In total, three different studies have now been able to explain the origins of most of the tens of thousands of known meteorites that have fallen to Earth.

As part of the research, astronomers conducted numerical simulations that allowed them to model the formation and evolution of families of asteroids orbiting the Sun in the large asteroid belt.

“This is a group of asteroids that have similar orbits because they were fragments created during the collision between two asteroids,” said astronomer Miroslav Broz, of Karolina University in Prague, and lead author of two of the studies, which were published in the journals. nature And aastronomy And astrophysics.

Collisions in the large asteroid belt send rock fragments flying randomly through space, some of which end up colliding with Earth.

“Although more than 70,000 meteorites are known, only 6% of them have been clearly identified by their composition as coming from the Moon, Mars, or Vesta, which is one of the largest asteroids in the large asteroid belt,” said astronomer Michael Marcet, of European Southern Observatory (ESO) in Chile, and lead author of one of the two published studies: “The origin of the other meteorites has not been determined.” In the magazine nature.

Three families of asteroids

The Massalia asteroid family, which formed about 40 million years ago, is responsible for a class of meteorites called L chondrites, which account for 37% of known terrestrial meteorites, according to the investigation. He revealed that the Karen family, which formed 5.8 million years ago, and the Coronis family, which formed 7.6 million years ago, are responsible for a class of meteorites called H chondrites, which represent 33% of known terrestrial meteorites.

Another 8% of terrestrial meteorites can be attributed to the Flora and Nyssa asteroid families found in the large asteroid belt, according to the investigation. He revealed that about 6% of meteorites could be attributed to Vesta. Previous studies revealed that less than 1% of meteorites come from Mars and the Moon.

Researchers are still exploring the origin of approximately 15% of known terrestrial meteorites. Space rocks have played an important role in shaping the direction of life on Earth.

The new research did not examine the origin of the dinosaurs that struck the Earth 66 million years ago and wiped out the dinosaurs, except for the birds descended from them, and allowed mammals to become dominant. Another study, published in August, concluded that this body formed outside Jupiter and may have migrated to our solar system, becoming part of the large asteroid belt, before it was thrown towards Earth, perhaps due to a collision.

As the collision that killed the dinosaurs showed, a large space rock could pose a deadly threat to life on Earth. In 2022, the spacecraft She turnedof NASA, intentionally collided with the asteroid Demorpho, in a planetary defense mission that demonstrated that a spacecraft could alter the course of a celestial body enough to keep Earth safe. Last October, the European Space Agency (ESA) launched a space probe Ivywhich you will check Demorpho, to evaluate the results of the collision with the NASA probe in detail.

Some meteorites that have fallen to Earth may give clues about the early history of the solar system. They are primitive remnants from a time when planets formed in a large disk of matter – It is called the protoplanetary disk – “Chondrites are primitive meteorites that have mostly maintained their original composition since their formation in our planetary disk,” Michael Marcet said.