The Willamette Meteorite, weighing in at 15.5 tons and on display at the American Museum of Natural History in New York City, is metallic iron likely formed from the collision of two protoplanets orbiting the Sun billions of years ago. It is surmised that the Willamette is what was left of one planet’s iron-nickel core after its encounter with Earth. Just the fact that it is iron, however, makes it rare. Iron meteorites make up about a twentieth of all space rocks arriving on Earth.
