The Cassini spacecraft reached Saturn in 2004 and spent thirteen years orbiting it — studying the planet, its rings and its moons, and sending back hundreds of thousands of pictures.

The rings are enormous — wider than the distance between Earth and the Moon — but in many places only tens of metres thick. They're made of countless pieces of ice and rock, from specks of dust to chunks as big as houses.

Cassini discovered geysers of water shooting from the small moon Enceladus, suggesting an ocean beneath its icy crust. To make sure the spacecraft could never crash into such a moon and contaminate it, NASA sent Cassini plunging into Saturn itself on 15 September 2017. It sent data back until the very end.