Meteorites

Meteorites are pieces of rock that formed in space that have made it all the way through Earth's atmosphere and hit the ground. 

Meteorites record billions of years of history from the formation of the very first solids through to the evolution of planets and, in some cases, the complete destruction of early planetary bodies. Researchers study meteorites to understand what was happening in the early solar system, how we went from small lumpy asteroids to planets, and what made Earth turn out so different to the other planets.

There are lots of words that we use to talk about distinct periods in a meteorite's life. For instance, "asteroid" is the name we give to a body of rock in space. These can vary in size quite dramatically, but very small ones can also be referred to as a "meteoroid". If an asteroid or meteoroid travels into Earth's orbit and gets close enough, it can enter the atmosphere. At this point, it becomes a "meteor".

Meteors fall through the atmosphere at break-neck speeds and the friction of the air against the meteor causes it to heat up, the outer layer to melt and be stripped away, and for the meteor to glow. If it's very bright, we call this a "bolide" or a "fireball". In recent years, scientists have used fireballs to work out where a meteorite might have landed so that they can go and collect it, and to calculate the orbit of meteor.

Finally, if any material survives its journey through the atmosphere and hits the ground, it becomes a "meteorite".

Meteorites can come from asteroids (or be asteroids) and from other planets. With few exceptions, each type of meteorite has its own origin or "parent body". The ordinary and enstatite chondrites come from the inner solar system, but the carbonaceous chondrites originate in the outer solar system. Igneous meteorites called achondrites come from various different planetary bodies including the Moon, Mars, and large asteroids like Vesta. Some groups like the iron meteorites don't have an obvious parent body at all because it was completely destroyed in the early solar system!

Researchers study the mineral and isotope compositions of meteorites to look for similarities and differences, helping them to work out where each particular meteorite might have come from and to understand the geology of it's parent body.