Meteorites, the rocks that fall to Earth from space, have been impacting our planet since its formation around 4.5 billion years ago. While many meteorites cause little damage, some have led to significant events throughout history. Recent research has shed light on where these space rocks originate.

By analyzing the composition of various meteorites and the asteroids in our solar system, astronomers have discovered that approximately 70% of known meteorite impacts come from three specific groups of asteroids located in the main asteroid belt between Mars and Jupiter. Researchers have accounted for the origins of most of the tens of thousands of meteorites that have landed on Earth through three separate studies.

The studies involved numerical simulations that modeled the formation and evolution of asteroid families orbiting the sun. “It is a group of asteroids which have similar orbits because they were fragments created during a collision between two asteroids,” said astronomer Miroslav Brož of Charles University in Prague, who led two of the studies published in the journal Nature and Astronomy and Astrophysics.

Collisions within the main asteroid belt send rocky fragments flying in various directions, and some eventually reach Earth. Despite the identification of over 70,000 meteorites, only 6% have been clearly linked to the moon, Mars, or Vesta, one of the largest asteroids in the belt. “The source of the other meteorites had remained unidentified,” said astronomer Michaël Marsset of the European Southern Observatory in Chile, who led one of the studies.

The research found that the Massalia asteroid family, formed around 40 million years ago, is responsible for a type of meteorite known as L chondrites, which make up 37% of meteorites on Earth. The Karin family, which formed 5.8 million years ago, and the Koronis family, formed 7.6 million years ago, account for H chondrites, representing 33% of known meteorites. An additional 8% can be traced back to the Flora and Nysa asteroid families, while about 6% originate from Vesta. Previous studies indicated that less than 1% of meteorites come from Mars and the moon.

Researchers are still working to determine the origins of the remaining 15% of known meteorites.

Meteorites have influenced the course of life on Earth, including the mass extinction event that wiped out the dinosaurs 66 million years ago, paving the way for mammals to thrive. A separate study released in August suggested that the asteroid responsible for this extinction event formed beyond Jupiter and later migrated inward to the main asteroid belt, eventually heading toward Earth.

The threat posed by large space rocks is significant, as demonstrated by NASA’s DART spacecraft mission in 2022, which successfully altered the trajectory of the asteroid Dimorphos to test planetary defense methods.

Some meteorites that fall to Earth provide valuable insights into the solar system's early history. They are remnants from a time before planets formed, originating from a protoplanetary disk that surrounded the young sun. “Chondrites are primitive meteorites that have mostly preserved their original composition since their formation in our protoplanetary disk,” Marsset said.