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The Willamette Meteorite

Willamette Meteorite_HERO AMNH/D. Finnin


The Willamette Meteorite weighs 15.5 tons. This iron meteorite, which was found in Oregon, is the largest ever found in the United States and the sixth-largest in the world. The smooth surface melted during its blazing entry into the atmosphere, while the pits formed on the Earth's surface.

Iron meteorites form when large enough asteroids have had molten interiors catastrophically collide with other asteroids. These huge collisions blast out material from the molten iron core of the asteroid on orbits that reach Earth after millions of years.

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The internal structure of the 15.5-ton Willamette meteorite, made of metallic iron, suggests that a complicated chain of events led to its formation:

Billions of years ago, an early planet orbiting the Sun was shattered, perhaps in a collision with another protoplanet. The fragment now known as the Willamette meteorite was probably part of the planet’s iron-nickel core.

While planets including Earth gradually formed and matured, the fragment orbited the Sun. It was hit at least twice by other planetary fragments, knocking it into a collision course with Earth.

Thousands of years ago, this meteorite, traveling some 64,000 kilometers per hour, crashed into Earth’s surface.

Over many centuries, rainwater interacting with its iron sulfide deposits produced sulfuric acid, which slowly etched and carved large cavit