How discoveries from the edge of the solar system transformed what was known about Pluto, thanks to the New Horizons space probe that took the first-ever close-up images of the dwarf planet. Pluto was once thought to be geologically dead, but the pictures revealed it to be an active world of stunning complexity, with mountains carved from ice, a nitrogen glacier that appeared to be moving and a recently active volcano. The data even led some scientists to speculate there may even be life on Pluto today