NOVA

- [Narrator] It's estimated as many as 50 meteorites hit Earth every day.

Many burn up in our atmosphere, creating shooting stars and meteor showers, but some of the largest ones do make it to Earth.

In 2018, the Hamburg meteor fireball streaked across the American Midwest sky.

- It's particularly pristine 'cause it landed on a frozen lake, so that keeps it in cold storage.

- It was like the meteor selected where to land because it wanted to be studied.

- [Narrator] A few years later, a meteorite the weight of a grand piano exploded in the skies near McAllen, Texas.

- It's like an explosion of dynamite.

That big explosion, that was a sonic boom.

(meteor whooshing) (text beeping) (pensive music) - [Narrator] The cows weren't the only witnesses that night in Winchcombe.

Doorbell and CCTV cameras never sleep, and networks of dedicated meteor cameras captured in from different angles.

That meant it was possible to calculate its trajectory.

(pensive music) (cow mooing) Back over the skies of England, out of Earth's atmosphere, past the orbit of Mars into the dark, this is where the meteorite's journey began.

(pensive music) A mysterious realm of countless rocky worlds rubble leftover from the formation of the solar system: asteroids.

(pensive music)