Pluto's frozen heart may hide underground ocean that flipped planet over

Evidence is mounting for an ocean at Pluto, buried beneath its frozen heart.

Scientists said on Wednesday that Pluto might have rolled over on its axis eons ago, the result of tidal forces with jumbo moon Charon. The extra weight of an underground sea is the most likely explanation, they said.

These latest findings are based on observations by Nasa's New Horizons, which made an unprecedented flyby of Pluto last year. The spacecraft is now 365 million miles from Pluto and en route to a 2019 close approach of another faraway orb.

Published in this week's journal Nature, the studies focus on a 600-mile basin in the left lobe of Pluto's heart-shaped region. This basin is known as Sputnik Planitia, named after the Russian satellite that launched the Space Age in 1957.