Pluto is covered in huge red patches and we don't know what they are

By Leah Crane

When NASA’s New Horizons spacecraft flew past the dwarf planet Pluto in 2015, it found that huge swathes of the surface are covered in a strange red material. Planetary scientists thought they knew the identity of this material, but it turns out their best guess isn’t a good match, leaving it a mystery.

Many assumed that these red patches were made of tholins, organic substances that form in a world’s atmosphere and then drift down to the surface. Pluto’s atmosphere, while extremely tenuous, …