Pluto may have huge ocean under icy surface, NASA evidence shows

Image Caption: Pluto as seen from NASA's New Horizons spacecraft

New evidence, reported in two research papers published in Nature journal, suggests the existence of an ocean containing as much water as all of Earth's seas - which could potentially be a habitat for life.

The findings are based on observations by NASA's New Horizons spacecraft, which made an unprecedented flyby of the dwarf planet and its moons in 2015.

Scientists say the ocean, which is likely slushy with ice, is about 62 miles deep and believed to lie 93 to 124 miles beneath the planet's crust.

Liquid water is considered one of the essential ingredients for life.

Massachusetts Institute of Technology planetary scientist and project researcher Richard Binzel said Pluto was not a prime candidate, due to its ocean being covered by so much ice.

However, he said that "one is careful to never say the word impossible".

Despite being about 40 times further from the sun than Earth, Pluto has enough radioactive heat left over from its formation 4.6 billion years ago to keep water liquid, experts said.

Image Caption: New Horizons transmits data back to Earth in an artist's illustration

University of California Santa Cruz planetary scientist Francis Nimmo, who also took part in the research, said: "Pluto has enough rock that there's quite a lot of heat being generated, and an ice shell a few hundred kilometres thick is quite a good insulator.

"So a deep subsurface ocean is not too surprising, especially if the ocean contains ammonia, which acts like an antifreeze."

Scientists made the discovery as they were trying to figure out why a 621-mile wide impact basin known as Sputnik Planitia, which contains an unusual heart-shaped region, was located in its present position near Pluto's equator.

Computer models showed the basin likely filled with ice, in turn causing the dwarf planet to roll on its axis, cracking its crust.

That could happen only if Pluto possessed a subsurface ocean, the analysis found.

Professor Nimmo said he suspected the ocean was primarily water with some ammonia or other "antifreeze" thrown in.

Slow refreezing of this ocean would conceivably crack the planet's shell - a scenario consistent with photos taken by New Horizons.

In September, astronomers discovered what they believed to be plumes of water spewing from the surface of Jupiter's moon, Europa, using the Hubble Space Telescope.

Image Caption: New Horizons transmits data back to Earth in an artist's illustration