asteroids

Asteroids, comets, meteoroids, meteors, and meteorites — what each one is, where they come from, and how scientists study them.

Planetary differentiation is how a hot, partly molten world sorts itself by density, with iron sinking to a core and lighter rock rising to form a mantle and crust. Here is what drives it, how fast it happens, and how we know.

In September 2022, NASA's DART spacecraft deliberately hit a small asteroid and shortened its orbit by about 33 minutes. It was the first real test of planetary defense. Here is how humanity finds, tracks, and might one day redirect a dangerous asteroid.