The god Pluto ruled the underworld in Roman mythology, presiding over a realm of darkness and death. In astronomy, this association isn’t too far off: the dwarf planet Pluto is a dim and isolated land, far, far away from his brother planets of Neptune and Jupiter. Hundreds of millions of years ago, amid the shocking cold, Pluto raged, spewing forth his fury from icy volcanoes.
Such frigid ferocity is the subject of research, thanks to a team of scientists studying data from the New Horizons spacecraft. Images highlight an otherworldly region of mountainous domes. The summits soar up to four miles high and stretch up to sixty miles wide. Known as cryovolcanoes, these mountains didn’t violently erupt, instead oozing “lava” of frozen water and chemical compounds. In keeping with its mythological namesake, Pluto clutches its secrets close: the cryovolcanoes are unlike anything else in the solar system.
Like volcanoes on Earth, Pluto’s cryovolcanoes probably spilled their slush from vents in the landscape. This theory fascinates scientists because it suggests that the interior of Pluto was unexpectedly warm—warm enough to support partially liquid water, perhaps even an ocean. As the water, mixed with compounds such as ammonia and methane, oozed forth from the vents, it reshaped Pluto’s surface. Over time, the frozen deposits have built up, forming hilly terrain as well as the towering domes of the cryovolcanoes themselves. And though Pluto may be the god of the dead, scientists think that the volcanoes may still be alive and erupt episodically—mountains of a sleeping god just waiting to be roused.