Coahuila Meteorite on loan to the Marion Natural History Museum from the Mineralogical & Geological Museum, Harvard University
The meteorite fell to Earth and was discovered in 1837 in the Mexican state of Coahuila (kow-uh-WEE-la, from which the meteorite got its name.) There is no record of anyone seeing it fall.
Coahuila weighs 317kg (almost 700 pounds!) and is a fragment of a much larger meteor that fell in Coahuila; many other similar fragments have been discovered in that area.
Why is Coahuila a meteorite and not a meteor or meteoroid? Rocks that come from space are often called meteors, but there is actually a difference between these terms. A meteoroid is a rock flying or floating in space. These range in size from small grains (like sand) to one meter (which is a little more than three feet.) Smaller grains are called micrometeoroids. Larger rocky bodies are classified as asteroids. A meteor is what we see when a meteoroid enters Earth’s atmosphere at high speed. During its descent, aerodynamic heating causes the object to glow and cast off glowing fragments. This streak we see in the sky is a meteor; many people know it as a “shooting star.” When multiple meteors streak through the atmosphere and seem to come from the same place in the sky, we call it a meteor shower. When a meteoroid or asteroid survives its passage through the atmosphere and impacts the ground, it becomes a meteorite.
Meteorites are classified into three broad categories based on their composition: Stony, Iron, and Stony-Iron. Coahuila is an iron meteorite with a complex crystalline internal structure caused by heating and cooling during my formation. Indentations on the surface were formed by collisions during Coahuila’s 4.5 billion year journey through space as well as by heating and ablation (melting) as it passed through Earth’s atmosphere.