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Our planet Earth offers many natural treasures, from gold and other precious metals to diamonds and other carbon-based compounds. But some treasures come from beyond Earth. They’re bits of asteroids or other bodies.
These rocks are known as meteorites, and they’re treasures in many ways. Collectors will pay dearly for them, and scientists value them for the information they contain about the history of the solar system.
Most meteorites are pieces of asteroids — rocky bodies left over from the solar system’s birth. Collisions break off small chunks that spiral around the Sun. Occasionally, one of these chunks plows into Earth’s atmosphere, forming a blazing streak of light known as a meteor. If it’s big enough, then part of the rock may survive and hit the ground.
Most meteorites are known as chondrites. They’re made mainly of rock. They contain small, round bits of crystallized rock that melted, then cooled and solidified. These bits may have formed when shockwaves hit asteroids as the solar system was taking shape, or when asteroids collided with enough force to melt some of their rock.
Other meteorites consist almost entirely of iron and nickel, or of a roughly equal mix of metal and rock.
A few meteorites appear to come from the Moon or Mars. Most of them are a lot younger than the meteorites that come from asteroids, and their chemistry matches what we know about the Moon or Mars — special treasures from beyond Earth.