An asteroid is a smaller-than-a-planet rock orbiting in the inner solar system. A meteor is the streak of light of a space rock plunging into the atmosphere, and a meteorite is the remnant of space rock that survives the fiery descent and comes to rest on the ground.

Thus, one might think that meteorites that fall on Earth ought to be just like the asteroids that pass through Earth’s neighborhood.

“That’s what everybody would have expected,” said Philipp R. Heck, the curator in charge for the meteorite and physical geology collections at the Field Museum of Natural History in Chicago.

Planetary scientists were surprised almost a decade ago when they discovered that the most plentiful types of meteorites they had collected and studied on Earth were actually not common in space.