A meteoroid (/ˈmiːtiərɔɪd/)[1] is a small ROCKY or metallic body in outer space.

Meteoroids are significantly smaller thanasteroids, and range in size from small grains to one-meter-wide objects.[2] Objects smaller than this are classified as MICROMETEOROIDS orspace dust.[2][3][4] Most are fragments fromcomets or asteroids, whereas others arecollision impact debris ejected from bodies such as the Moon or Mars.[5][6][7]

When a meteoroid, comet, or asteroid enters Earth's atmosphere at a speed typically in excess of 20 km/s (72,000 km/h; 45,000 mph), aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it LEAVES in its wake. This PHENOMENON is called a meteor or "shooting star". A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the SKY is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, it is then called a meteorite.

An estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earth's atmosphere each year.[8]