The distinction between a meteor, a meteoroid, and a meteorite is based solely on their location relative to Earth, not their composition or size. These terms describe the same object at different stages of its journey through space and our planet’s atmosphere. The object begins as space debris, becomes a visible phenomenon as it plunges toward Earth, and finally earns a different name if any part survives the descent to the ground.
The Object in Space
The initial object is called a meteoroid, a piece of rocky or metallic debris traveling through outer space. Meteoroids are significantly smaller than asteroids, ranging in size from tiny dust grains up to about one meter in diameter. Objects larger than this are classified as asteroids, while smaller ones are often referred to as micrometeoroids or space dust. These fragments originate primarily from the asteroid belt, though some are debris shed by comets or material ejected from the Moon or Mars after an impact. Meteoroids orbit the Sun at high speeds, and their paths occasionally intersect with Earth’s orbit.
The Atmospheric Event
When a meteoroid enters Earth’s atmosphere at high velocity, it creates the spectacular light show known as a meteor. This phenomenon, commonly called a “shooting star,” is a streak of light caused by the object’s rapid passage through the air. The immense speed of the incoming object rapidly compresses the air, generating extreme heat that vaporizes the meteoroid’s surface and causes the surrounding air to ionize and glow. Meteors typically become visible between 75 and 120 kilometers in altitude and usually disintegrate before reaching the ground. Brighter events are categorized as fireballs, and the most intense are bolides, which may explode in an air burst.
The Grounded Survivor
A meteorite is the physical piece of the meteoroid that survives its fiery atmospheric passage and lands on the Earth’s surface. Most meteoroids burn up completely, meaning the vast majority of meteors do not result in a find. The surviving fragment often bears distinctive marks from its high-speed entry, providing evidence of its extraterrestrial origin. A fresh meteorite possesses a thin, dark, glassy outer layer called a fusion crust, which is the cooled, melted surface material. Some also exhibit shallow, thumbprint-like indentations called regmaglypts, formed by hot air currents eroding the rock.
What They Are Made Of
Beyond their location-based names, meteorites are classified into three major groups based on their material composition.
Stony Meteorites
The most common are the stony meteorites, which account for the majority of observed falls and consist primarily of silicate minerals. This group includes chondrites, which contain tiny, spherical grains called chondrules. Chondrites represent some of the oldest, most primitive material in the solar system.
Iron Meteorites
Iron meteorites are almost entirely composed of metallic iron and nickel. These dense objects are thought to be fragments from the metallic cores of differentiated asteroids.
Stony-Iron Meteorites
The third and rarest group is the stony-iron meteorites, which contain a nearly equal mixture of silicate minerals and iron-nickel metal. This category, which includes pallasites with their distinctive olivine crystals, offers a glimpse into the boundary layers between an asteroid’s core and mantle.