As the data being transmitted by the New Horizons space probe continues to flow back to Earth, scientists poring over the information continue to find new surprises, including possible evidence that Pluto has a subsurface ocean of liquid water. Scans of the western lobe of the dwarf planet’s "heart" show that, for some unknown reason, there is extra mass in the region. This came as a surprise to the researchers: the area, dubbed Sputnik Planum, is thought to have been formed by a meteor impact, meaning that it should have negative mass, as one would assume from an impact crater.

"An impact crater is basically a hole in the ground. You’re taking a bunch of material and blasting it out, so you expect it to have negative mass anomaly, but that’s not what we see with Sputnik Planum," explains assistant professor Brandon Johnson, head of the research team at Brown University.

But after running computer simulations to try to determine why there would be positive mass in what should be a hole in the ground, the researchers at Brown University found that the anomaly could be explained by the presence of a liquid ocean deep beneath Pluto’s surface that welled up into the crater after it was formed — despite the former planet only being a few dozen degrees above absolute zero.

This ocean, thought to be roughly 100 kilometers (62 miles) below the surface, would have to have an extremely high salt content for it to remain liquid at those temperatures, in an effect similar to the rivulets of brine found flowing on the surface of Mars. Along with the Earth-bound water we’re quite familiar with, this may mean that Pluto could join the liquid ocean club, along with Enceladus and Europa, and possibly Ceres and Ganymede, both theorized to have their own subsurface oceans. Needless to say, further investigation needs to be done to determine the chemical makeup of the ocean, how deep it is — and even why it exists to begin with.