The vast majority of meteorites, about 99.8%, come from asteroids in the belt between Mars and Jupiter. The remaining 0.2% is split roughly equally between rocks blasted off the surface of Mars and the Moon. These aren’t random wanderers. Each meteorite followed a specific gravitational pathway from its parent body to Earth, a journey that often took millions of years.
The Asteroid Belt: Source of Nearly All Meteorites
The asteroid belt sits between Mars and Jupiter, spanning a broad region of space filled with rocky remnants left over from the solar system’s formation. These objects never assembled into a planet, largely because Jupiter’s enormous gravity kept stirring them up. The belt is considered the prime contributor of near-Earth asteroids, and by extension, the overwhelming source of meteorites that land on our planet.
But asteroids don’t just fall out of the belt on their own. They need a push. That push comes from collisions between asteroids, which break off fragments ranging from pebble-sized to boulder-sized. Those fragments then drift slowly through the belt, nudged by the faint pressure of sunlight (a phenomenon called the Yarkovsky effect), until they wander into one of several gravitational “escape routes” that funnel material toward the inner solar system.
How Jupiter Sends Rocks Toward Earth
Jupiter is the engine behind meteorite delivery. Its gravity creates zones within the asteroid belt called Kirkwood Gaps, regions that are nearly empty of asteroids because Jupiter’s gravitational pull makes orbits there unstable. The most important of these is the 3:1 resonance, located around 2.5 astronomical units from the Sun, where an asteroid orbits the Sun exactly three times for every one orbit Jupiter completes. Any fragment that drifts into this zone has its orbit stretched into a more elongated ellipse, eventually crossing Earth’s path.
Asteroids entering the chaotic zone near the 3:1 resonance can evolve from stable belt orbits to Earth-crossing orbits in as little as one million years. A second major pathway, called the ν6 secular resonance, operates at the inner edge of the belt and works on longer timescales. Together, these two resonances are responsible for delivering the majority of asteroidal material to Earth. Several additional resonances contribute smaller fractions, but the 3:1 and ν6 do the heavy lifting.
Rocks From Mars and the Moon
A small but scientifically fascinating fraction of meteorites originated on other worlds. Over 200 meteorites in our collections have been identified as Martian, and a comparable number came from the Moon. These rocks were launched into space by massive asteroid impacts on those surfaces.
Getting a rock off Mars is no easy feat. Mars has enough gravity that material needs to reach about 5 kilometers per second (over 11,000 miles per hour) to escape. A direct hit from a large asteroid generates shock pressures intense enough to do this, but those same pressures would destroy or melt the rock. The solution lies in a process called spallation: when the shockwave from an impact bounces off the surface, it creates a rebound effect that accelerates near-surface material to high velocities without subjecting it to the full crushing force of the impact. The rocks that survive this process were launched from at least a meter below the surface. Once free of Mars’s gravity, they orbited the Sun for thousands to millions of years before eventually crossing Earth’s path.
Lunar meteorites follow the same general mechanism, though the Moon’s weaker gravity makes escape easier. These rocks give scientists a way to study parts of the Moon and Mars that no rover or lander has visited.
What Meteorites Are Made Of
Meteorites fall into two broad categories based on what happened inside their parent bodies. Chondrites are rocks from asteroids that were heated but never fully melted. They preserve tiny round grains called chondrules that formed in the early solar nebula, making them some of the most primitive material in the solar system. Chondrites come in several families: ordinary chondrites (the most common type to fall on Earth), carbonaceous chondrites (rich in carbon compounds and water-bearing minerals), and enstatite chondrites.
The second category includes everything that experienced melting and internal separation inside a larger parent body. When an asteroid grows large enough, heat from radioactive decay melts its interior, causing heavy metals like iron and nickel to sink to the core while lighter rocky material rises to the surface. Iron meteorites are samples of those ancient cores. Stony-iron meteorites, including the striking olivine-studded pallasites, come from the boundary between core and mantle. Achondrites are pieces of the outer rocky layers. This second group represents a much larger number of distinct parent bodies than the chondrites, because many different asteroids went through this melting process independently.
The Oldest Material in the Solar System
Some meteorites contain tiny mineral grains called calcium-aluminum-rich inclusions that are the oldest solid objects ever dated. The oldest known inclusion, found in a carbonaceous chondrite called Northwest Africa 2364, formed 4,568.2 million years ago. This predates previous estimates by up to 1.9 million years and represents the very first solids to crystallize from the cloud of gas and dust that became our solar system. When you hold a meteorite containing these inclusions, you’re holding something older than any planet, moon, or asteroid that exists today.
Confirming the Connection: Bennu and Beyond
For decades, scientists matched meteorites to asteroids using telescopic observations of color and reflected light. In 2023, NASA’s OSIRIS-REx mission returned a physical sample from the asteroid Bennu, providing the first direct chemical comparison between a known asteroid and meteorites in our collections. The Bennu sample contained 14 of the 20 amino acids that life on Earth uses to build proteins, plus all five nucleobases used in DNA and RNA. These same building blocks had previously been detected in carbonaceous chondrite meteorites found on Earth, confirming the link between these meteorite types and carbon-rich asteroids.
The sample also revealed 11 minerals that form when salt-laden water slowly evaporates, preserving a record of liquid water activity on Bennu’s parent body that lasted thousands of years or longer. Some of these minerals, like trona, had never been found in extraterrestrial material before. Meteorites that fall through Earth’s atmosphere inevitably pick up contamination, so having a pristine sample confirmed that the organic molecules and water-formed minerals scientists had been finding in meteorites were genuinely extraterrestrial.
Where Meteorites Are Found on Earth
Meteorites land everywhere on Earth’s surface at roughly equal rates, but finding them is another matter. Antarctica is the best place in the world to recover meteorites. Dark rocks stand out against white ice, and the continent’s glacial dynamics actively concentrate them. Meteorites that fell across a wide area over thousands of years get trapped in the ice sheet, which slowly flows toward the coast. Where that flow hits buried mountain ranges, it’s forced upward, and fierce winds ablate the surface ice away, leaving behind a growing collection of meteorites on exposed patches of blue ice. Since systematic searches began, over 11,000 meteorites have been collected from just one Antarctic site, the Grove Mountains, by Chinese expeditions alone. Hot deserts like the Sahara and the deserts of Oman serve a similar role: dry conditions prevent weathering, and the pale, featureless landscape makes dark stones easy to spot.
Earth gains a substantial amount of extraterrestrial material every year, though most of it arrives as dust too fine to notice. The meteorites large enough to find on the ground represent a tiny fraction of what enters the atmosphere, since most incoming material burns up entirely during its descent.