Two years ago, a fireball and an explosion in the night sky near Waco, Texas, triggered a celestial “gold rush.” Collectors descended on Central Texas to look for the fireball’s remnants. Within days, they found them: meteorites — bits of debris from beyond Earth.
The Texas meteorites are similar to most of those found around the world — rocks known as chondrites. They’re some of the original building blocks for the planets and moons. They formed as small, solid grains in the cloud of material around the newborn Sun stuck together. Some of the material partially melted, forming small, round blobs known as chondrules — hence the name “chondrites.”
These objects were never incorporated into a planet or other large body, so they haven’t changed much since their formation. That means they preserve a record of the conditions when Earth and the other planets were being born — four-and-a-half billion years ago.
A few meteorites are chips of larger bodies — mainly the giant boulders known as asteroids. Some meteorites were knocked off the surfaces of these objects — including many that appear to have come from the asteroid Vesta. A spacecraft that’s orbiting Vesta right now may help confirm the origin of those meteorites. But other meteorites, which are made mainly of iron and nickel, came from deep inside the asteroids.
And a few appear to have an even more exciting pedigree: they came from the Moon or Mars. More about those tomorrow.
Script by Damond Benningfield, Copyright 2011
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