When the New Horizons spacecraft whizzed by Pluto in 2015, we Earthlings were dazzled by the breathtaking images it beamed home. They revealed a never-before-seen alien landscape - a world of mountains made of ice mixed with plains of frozen-solid methane and nitrogen. After over two years of poring over the data, NASA has made remarkable new discoveries about everyone's favorite dwarf planet. But New Horizons didn't stop there.