A startling new discovery on Pluto shows that we have a lot to learn about the former ninth planet from the sun.

NASA’s New Horizons probe continues to send back amazing new details about Pluto ever since its flyby last summer, and the latest data suggests that the dwarf planet might have once had a liquid ocean deep below its crust — and may even still have one, according to a Brown University release.

Scientists had thought such an ocean would have frozen over millions of years ago, but new analysis indicates that the ocean may still be liquid even today.

An image released from the New Horizons spacecraft shows a section of highlands bordering a section of icy plains, indicating that there may be plate tectonics at work that could herald a liquid ocean beneath the surface.

If Pluto’s ocean had forzens millions of years ago, the entire dwarf planet would have shrunk, but there are no such signs of this — if anything, Pluto is expanding.

“Thanks to the incredible data returned by New Horizons, we were able to observe tectonic features on Pluto’s surface, update our thermal evolution model with new data and infer that Pluto most likely has a subsurface ocean today,” said Noah Hammond, a graduate student in Brown’s Department of Earth, Environmental and Planetary Sciences, and the study’s lead author.