Pluto’s heart-shaped region full of ice and nitrogen snow, known as Sputnik Planitia, is probably the planet’s most prominent feature. Locked in alignment with Pluto’s moon Charon, Sputnik Planitia is constantly facing the moon and NASA may have found the reason why.

NASA’s spacecraft New Horizons has been collecting data on the planet and believe there could be evidence that an ocean could be harbored beneath the ice surface of the area which caused Pluto to roll over and create the alignment with Charon. Pluto ad Charon are tidally locked which means the two are always showing the same side to each other.

“If you were to draw a line from the centre of Pluto’s moon Charon through Pluto, it would come out on the other side, almost right through Sputnik Planitia. That line is what we call the tidal axis” stated co-author of one study, James Keane from the University of Arizona.

It was Francis Nimmo and his co-authors of a separate study that prompted a theory that sub-icy ocean is lurking beneath the surface of this exact alignment: “It’s a big, elliptical hole in the ground, so the extra weight must be hiding somewhere beneath the surface. And an ocean is a natural way to get that,” stated Nimmo.

It’s thought a massive meteorite made impact with the planet at some point creating the basin that makes up the heart-shaped region which would have caused anything beneath the surface such as a sub-icy ocean to push the crust outward. This in turn would have created a “positive gravitational anomaly” that would have caused Pluto to roll over from its axis.

James Keane believes that although a subsurface ocean is a possibility, there could be other explanations such as a build up of icy nitrogen in the heart, causing weight and dictating Pluto’s orientation.

Details of both studies were published in the journal Nature.