A vast ocean buried below Pluto's surface has raised fresh hopes of extraterrestrial activity, a study has suggested.
Deep beneath an ice shell over 60 miles thick, the ancient body of water could hold the ingredients to life beyond our planet.
Analysis of images from NASA’s New Horizons mission shows that Pluto was hot when it first formed, rather than a celestial snowball as previously thought.
The ocean is thought to have existed for around four and a half billion years - older even than the seas on Earth.
Planetary scientist Carver Bierson said: "Even in this cold environment so far from the sun, all these worlds might have formed fast and hot - with liquid oceans.
"By examining Pluto's features today we can begin to understand its birth four and a half billion years ago.
"We are pretty sure water is one of the ingredients for life.”
Suggestions of an underground ocean Pluto were explored in 2016, yet this new study gives a fresh indication of how it came to exist.
Previous theories of its formation suggested that the dwarf planet began melting slowly over time due to radioactive decay.
"Instead, Pluto has had an ocean that has been slowly freezing for all of solar system history,” said Mr Bierson.
Astronomers have long presumed that life would only be found on planets such as Earth, which are found in an area of space which is not too hot or too cold to sustain life - dubbed the ‘Goldilocks zone’.
Publishing their findings in the journal Nature Geoscience, the researchers from California University in Santa Cruz said this gives fresh hope of life elsewhere on icy planets known to us.
Their research suggests that other objects at the edge of the solar system were once hot with oceans, meaning similar bodies of water could still exist today.
Mr Bierson said: "The long-term chemical interactions between these oceans and the rocky materials below may have implications for ocean chemistry and the potential habitability of these distant icy worlds."