While scientists know that Pluto, like Earth, flipped on its side sometime in its past, Pluto's orientation before the flip and the degree to which it reoriented itself has not been well understood. Scientists who use New Horizons data to study Pluto's geologic past hope to find clues that explain this event. Now, a group of researchers has attributed Pluto's flip to the formation of Sputnik Planitia, a 620-mile-wide (1,000 km) basin that makes up half of the iconic heart-shaped region on Pluto. Researchers previously knew that Sputnik, which is filled with nitrogen ice, played a profound role in realigning...