Scientific American shows how the dwarf planet at the fringes of our solar system was partially shaped by a cartoonish reaction to a major collision:
Its elliptical western lobe, the 1,240-mile-long Sputnik Planitia, caught the attention of planetary scientists: It appears to be a bowl carved out by a monumental ancient impact. And today it is filled with young floes of churning nitrogen ice.
New Horizons did not get quite as good a look at the other side of Pluto. But when it had a peek, it did manage to spy a spot on the part of the globe exactly opposite to Sputnik Planitia that looked like a jumbled geologic jigsaw of crevasses, mounds and pits.
According to simulations replicating that cataclysm, it sent powerful seismic waves around and through Pluto, reaching the area on the other side of the world and tearing up the land there to make the strange features seen by New Horizons. Crucially, the transmission of those potent seismic waves, and the subsequent creation of the specific dimensions of that chaotic terrain, would have only been possible if Pluto had a 93-mile-thick subsurface ocean of liquid water—an idea scientists have been considering for a while.
Help, as it happens, was hiding billions of miles away on Mercury. Its Caloris Basin, a 950-mile-long impact crater, lies on the exact opposite side of the world, or antipode, to a geologic pandemonium of shattered rock and maddeningly undulating topography. “There’s nothing like it anywhere else on the body,” [Brigham Young University planetary scientist Jani] Radebaugh says. Scientists have long thought this rough terrain resulted from Caloris’s violent creation—just as the undulating land on Sputnik Planitia’s antipode may have also been a result of Pluto’s own giant impact event.