It may have been relegated to dwarf planet status, but Pluto’s surface has one thing that no other planets in our solar system have: a France-sized, heart-shaped mysterious formation filled with nitrogen ice on the hemisphere facing away from the big moon Charon.

Known as Sputnik Planitia, this large basin astounded astronomers because its surface is crater free (meaning it’s very young), is surrounded by tall water-ice mountain ranges and has glacier-like flows that are on the move.

And here’s the kicker: no one is totally sure how these icy plains appeared. Statistically, there’s only a 5% chance that it formed where it is now - almost precisely opposite Charon. Some say this because Sputnik Planitia dragged the crust of Pluto to the current arrangement - a phenomenon known as “true polar wander.”