Billions of years ago, in the icy outskirts of the solar system, a dramatic collision forged the unusual pairing of Pluto and its moon, Charon. This celestial dance defied expectations ...

Planitia structure on its surface. Ever since NASA's New Horizons sent back the first-ever photos of Pluto in 2015, the dwarf planet's mysterious heart-shaped region has puzzled scientists.

Pluto seemed hopelessly cold and distant until 2015, when NASA’s New Horizons space probe beamed back images of the giant heart-shaped mark that dominates the dwarf planet’s surface.