NASA estimates that about 44 metric tons (48.5 US tons) of material from space reach Earth every day. It arrives as everything from dust grains to the occasional rock the size of a fist, and three different words describe it, depending on where it is at that moment.
These words do not name three kinds of objects. They name one kind of object in three places. A meteoroid is the rock in space, a meteor is the streak of light it makes while crossing the sky, and a meteorite is any piece that survives and lands. Once you know where the object is, you know which word to use.
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The short answer: one rock, three words
Ask one question: where is the object right now? The answer picks the word. The table puts the three side by side.
| Word | Where the object is | What you see or hold | Typical size |
|---|---|---|---|
| Meteoroid | In space, orbiting the Sun | Nothing, unless a telescope or spacecraft finds it | Dust grain to small asteroid |
| Meteor | In the atmosphere | A streak of light, often called a shooting star | Often sand grain to small pebble |
| Meteorite | On the ground | A rock you can pick up | Typically pebble to fist |
The same rock can pass through all three stages. It starts as a meteoroid circling the Sun, becomes a meteor when it hits the upper atmosphere at high speed, and becomes a meteorite only if something is left when it reaches the ground. Most rocks never get to the third stage. NASA notes that less than 5% of the original mass of most space rocks smaller than a football field reaches the ground.
Meteoroid: the rock in space
NASA describes meteoroids as space rocks that range in size from dust grains to small asteroids. The exact limits depend on who is writing. A 2010 paper by meteorite scientists Alan Rubin and Jeffrey Grossman, listed on the USGS site, defines a meteoroid as a natural solid object from 10 micrometers to 1 meter across, moving through interplanetary space. A micrometer is one thousandth of a millimeter. NASA's Center for Near-Earth Object Studies uses nearly the same range: about ten microns to a meter or so.
Where do meteoroids come from? The American Meteor Society (AMS) calls a meteoroid "a small natural object in space, often a fragment of an asteroid or comet." NASA says most meteorites found on Earth come from shattered asteroids, and the grains behind meteor showers come from comets and, in a few cases, asteroids. At the large end, the label blends into "asteroid." A small asteroid and a large meteoroid can be the same kind of body, which is why NASA's own range runs up to small asteroids. For the bigger bodies, see what asteroids are and where they live.
Meteoroids move fast. The AMS gives entry speeds of roughly 11 to 72 km/s (25,000 to 160,000 mph). At those speeds, a particle as small as a sand grain can make a streak you can see.
Meteor: the streak of light
A meteor is not an object at all. The AMS defines it as the streak of light produced when a meteoroid enters the atmosphere. NASA puts it in plain terms: meteoroids that enter the atmosphere at high speed and burn up make the light people call a shooting star. NASA adds that this can happen at other planets with an atmosphere, such as Mars.
Most visible meteor activity happens about 80 to 120 km (50 to 75 miles) above the ground, according to the AMS. That is far above airliners and above all weather. Many visible meteors come from particles ranging from sand-grain size to a small pebble, the AMS adds, so the glow comes from something tiny.
Meteors come in two kinds. Sporadic meteors arrive from random directions on any clear night; NASA says several per hour can usually be seen. Shower meteors arrive in bursts from one part of the sky when Earth crosses a stream of comet debris. Why meteor showers happen explains that pattern.
Meteorite: what reaches the ground
NASA's definition is short: when a meteoroid survives the trip through the atmosphere and hits the ground, it is called a meteorite. Meteorites typically range from the size of a pebble to a fist. More than 50,000 have been found on Earth, and NASA says 99.8% of them come from asteroids. The remaining 0.2% is split roughly equally between Mars and the Moon.
The Rubin and Grossman definition is broader. It says a meteorite is a natural solid object larger than 10 micrometers, derived from a celestial body, that was carried away from that body and later collided with a natural or artificial body larger than itself. Weathering does not change the name as long as something recognizable of the original minerals or structure remains. Under that wording, the name is not limited to Earth.
Scientists sort meteorites by makeup into stony, iron and stony-iron groups, and the main types of meteorites describes each one. If you are holding a suspicious rock, a checklist for testing a possible meteorite covers the first screening steps.
Fireballs, bolides and micrometeorites
Three more words sit at the edges of the main three. A fireball is a very bright meteor. The AMS uses a brightness cutoff: brighter than magnitude -4, roughly the glare of Venus. Astronomers measure brightness in magnitudes, and a lower number means a brighter object. The CNEOS pages draw the line a little differently, at magnitude -3 as seen straight overhead, while NASA's pages simply say meteors brighter than Venus.
A bolide is a fireball that ends in a bright flash, often with visible breakup, according to the AMS. CNEOS says fireballs that explode in the atmosphere are technically called bolides, though the two words are often used as if they meant the same thing. NASA describes bolides as very bright meteors that can even be seen in daylight. For sound, detection and reporting, see how fireballs and bolides are detected and reported.
A micrometeoroid is a meteoroid between 10 micrometers and 2 mm (about 0.08 inch) across. Once such a grain lands, Rubin and Grossman call it a micrometeorite. These are the dust-sized end of the meteorite family.
Common mistakes and myths
- "A shooting star is a star." It is a meteor: a bit of rock or dust glowing high in the air. It has nothing to do with a real star, which is far larger and far more distant.
- "Friction makes meteors glow." The NASA Night Sky Network lists this as a common misconception. The air in front of a fast object is squeezed and heated, and that hot gas, together with the object's glowing surface, makes the light.
- "Every meteor ends up as a meteorite." Almost none do. NASA says most meteor shower debris is between a grain of sand and a pea in size and burns up before it reaches the ground, and the AMS says most particles behind meteor showers do not survive the trip.
- "A meteorite is hot or glowing when it lands." The Night Sky Network lists this one too. Only the thin outer skin is heated during the brief flight, and the whole rock does not stay hot.
- "Meteorites are easy to find and worth a fortune." The same guide calls both ideas misconceptions. Many rocks that look like meteorites turn out to be ordinary Earth rocks.
Frequently asked questions
Is a shooting star a meteor or a meteorite?
A shooting star is a meteor. The name describes the streak of light in the sky. Only a piece that survives and reaches the ground is a meteorite.
How big can a meteoroid be?
The USGS-listed definition and CNEOS both give a range of about 10 micrometers to roughly a meter. NASA's wording is looser and runs from dust grains to small asteroids. NASA's fact page calls the house-sized object that exploded over Chelyabinsk, Russia, in 2013 a meteoroid.
How much material falls on Earth each day?
NASA estimates about 48.5 US tons (44 metric tons) of meteoritic material each day. The figure covers everything from dust to rocks, and only a small part of it ever becomes a meteorite someone could pick up.
What is a micrometeorite?
A micrometeorite is a meteorite between 10 micrometers and 2 mm in size, in the Rubin and Grossman definition. It is the same kind of object as a larger meteorite, only much smaller.
Sources
- Meteors and Meteorites. NASA Science, accessed November 2026. https://science.nasa.gov/solar-system/meteors-meteorites/
- Meteors and Meteorites: Facts. NASA Science, accessed November 2026. https://science.nasa.gov/solar-system/meteors-meteorites/facts/
- Meteor FAQ. American Meteor Society, accessed November 2026. https://www.amsmeteors.org/faq/
- Meteorite and meteoroid: New comprehensive definitions. A. E. Rubin and J. N. Grossman, Meteoritics and Planetary Science, 2010 (USGS publication record). https://www.usgs.gov/publications/meteorite-and-meteoroid-new-comprehensive-definitions
- Fireballs and Bolides: introduction. NASA JPL Center for Near-Earth Object Studies. https://cneos.jpl.nasa.gov/fireballs/intro.html
- Fireballs. American Meteor Society, accessed November 2026. https://www.amsmeteors.org/fireballs/
- Meteorite or MeteorWrong activity guide. NASA Night Sky Network. https://nightsky.jpl.nasa.gov/documents/806/MeteoriteOrWrong.pdf