Despite sharing a name with a popular Disney Character, if Pluto were a person, it might very well suffer from an inferiority complex. It is only 1,400 miles wide, about half the width of the United States and slightly smaller than the Earth’s Moon. It sits 3.6 billion miles from the sun in the icy outer reaches of our solar system. With an average temperature of -380 degrees Fahrenheit, it is not on many people’s list of places they would like to visit. Pluto is not even a planet anymore, it has been reclassified as a “dwarf planet.”

Pluto does, however, have a sort of mini solar system of its own, with three known moons. There may also have once been warm water on Pluto or, at least, on its largest moon Charon.

The moons around some of the gas giants, such as Jupiter’s moon Europa and Saturn’s moon Enceladus, have cracked surfaces with indications of subterranean oceans. As these moons move around their planets, there is a gravitational tug of war between the moons, other moons and the planets. This constant push and pull causes an eccentric, oval-shaped orbit.

All of this is believed to cause tidal movements in the oceans which generate heat and keep the oceans from freezing. It also causes the the interior to flex and stress the surface, causing cracks.

Pluto’s moon Charon is extremely large compared to the planet it orbits. It is roughly one-eighth of Pluto’s mass, a record in this solar system. Like our Moon, it is believed to have formed after a large impact ejected material from Pluto’s surface. The size and proximity of Charon would have caused strong tides on Pluto and its moon, causing the two to bulge toward each other.

“Depending on exactly how Charon’s orbit evolved, particularly if it went through a high-eccentricity phase, there may have been enough heat from tidal deformation to maintain liquid water beneath the surface of Charon for some time. Using plausible interior structure models that include an ocean, we found it wouldn’t have taken much eccentricity (less than 0.01) to generate surface fractures like we are seeing on Europa,” said Alyssa Rhoden of NASA’s Goddard Space Flight Center in Greenbelt, Maryland in a statement.

Charon and Pluto now seem to be tidally locked with one another, with the same side of Charon facing the same side of Pluto constantly. This means that if there ever were warm oceans, it is likely that they have since frozen. The tidally locked position would not generate enough tidal activity to cause warming.

In July of 2015, NASA’s New Horizons spacecraft will arrive at Pluto and Charon and will provide researchers with their best views to date of the distant planet and its moons. This latest research, now available online in the journal Icarus, will give NASA scientists some idea of what to look for once New Horizons arrives.

“This research gives us a head start on the New Horizons arrival – what should we look for and what can we learn from it. We’re going to Pluto and Pluto is fascinating, but Charon is also going to be fascinating,” Rhoden said.