In 2015, NASA's New Horizons space probe flew by Pluto and found the presence of ammonia on the surface of the dwarf planet.

Now, a new study suggests that the whiff of ammonia in the reddish ice of the distant world was left over from a recent geological activity — one where a volcano spewed liquid water instead of molten lava.

The findings, which were published in the journal Science Advances, hints at the existence of an ocean full of liquid water beneath the surface of Pluto.

Evidence Of Liquid Water In Pluto

The study used images of Pluto taken by the New Horizons space probe during a flyby in 2015. A team of scientists analyzed the wavelengths of light in the images to determine the chemical compounds found the dwarf planet's surface.

They found signs of ammonia, a fragile molecule broken down over time by ultraviolet sunlight and cosmic rays. The ammonia-rich water ice was found around a large crack called Virgil Fossa, just west of the large heart-shaped feature of Pluto. The team claimed that Virgil Fossa might have been a fissure from which liquid water once spewed out of a cryovolcano. They also said that the eruption happened not too long ago.

"If you find it at all, it suggests that it has been put there fairly recently," Dale Cruikshank, a planetary scientist at NASA Ames Research Center and one of the authors of the study, told Science News. "There is really no limit [to how recently], as far as I can see in the geology."

Ammonia can also lower the freezing point of water by 100 degrees Celsius. If there is a subsurface ocean underneath the icy crust of the dwarf planet ammonia can explain the existence of liquid water. Pluto, on average, is 39.5 AU away from the sun, and the surface temperature reaches -270 degrees Celsius.

Finding An Ocean In Pluto

Cristina Dalle Ore, also a planetary scientist from NASA Ames Research Center and the first author of the study, said that the extent of the ocean underneath the surface of Pluto is still unknown. She noted that it might only be a few pockets or liquid water or the entire planet might be covered by a watery layer beneath the crust.

"My next task is to try to determine the location of all the vents from which water and ammonia might have been sprayed in an attempt to map the size of the ocean," stated Dalle Ore.