Pluto's surface, fitting for a world whose surface shivers at a cryogenic -364 F (-220 C), is frozen solid. But beneath that nitrogen ice may lie a subsurface ocean of liquid water. A recent study ...

This cutaway image of Pluto shows a section through the area of Sputnik Planitia, with dark blue representing a subsurface ocean and light blue for the frozen crust. Disclaimer: AAAS and EurekAlert!

The heat might be coming from a hidden ocean or radioactive elements beneath Pluto's surface. This would be a real turn-up for the books as, until now, astronomers thought Pluto was too old to ...