Credit NASA with another milestone in space exploration: On February 12, 2001, a spacecraft landed on the surface of an asteroid for the first time in history.

After a year spent orbiting the asteroid 433 Eros, the Near Earth Asteroid Rendezvous (NEAR) spacecraft made a controlled descent to the surface. But what exactly is an asteroid? And what was the NEAR Shoemaker mission about?

Photo courtesy NASA/JHUAPL
NEAR descends to the surface of 433 Eros.

In this edition of HowStuffWorks, we will examine these tiny bodies of our solar system and the successful mission to study them.