A vast ocean on Jupiter's moon Europa contains all the ingredients for life, according to new research.
Aliens really could be living under its surface - just like in space thriller Europa Report, say scientists.
The frozen world 400 million miles from Earth is one of the largest satellites in the solar system.
More like a planet, it has an oxygen-rich atmosphere. Its sea lies beneath an 11 mile thick crust of ice - and goes the whole way round.
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Lead author Dr Mohit Melwani Daswani, a geochemist at NASA's Jet Propulsion Laboratory in Pasadena, California, said: "We believe this ocean could be quite habitable for life."
Simulations discovered it's salty - just like those on Earth. It's also rich in chloride - the main ingredient in table salt.
His team also found the sea would originally have been mildly acidic with high levels of carbon dioxide, calcium and sulphate.
Dr Daswani said: "Indeed it was thought this ocean could still be rather sulphuric.
"But our simulations - coupled with data from the Hubble Space Telescope showing chloride on Europa's surface - suggests the water most likely became chloride rich.
"In other words, its composition became more like oceans on Earth."
Europa has long been considered among the likeliest places to find extra-terrestrial life.
Earlier this year a British expert said it is "almost a racing certainty" its sea is home to "octopus-like creatures."
The latest model supports the theory. It was based on geo-chemical reservoirs within the interior using data from the Galileo fly-by mission.
Dr Daswani said the ocean was formed by tidal forces or radioactive decay from its core generating heat - breaking down water-containing minerals.
The study presented at the virtual Goldschmidt conference suggests life could be common throughout the universe.
It may have evolved on a host of worlds in the solar system alone - including Saturn's moon Enceladus, Pluto and its moon Charon and the dwarf planet Ceres.
The Voyager missions first discovered Europa's crust was floating on a subsurface ocean more than 40 years ago. But its origins were unclear.
Dr Daswani explained: "We were able to model the composition and physical properties of the core, silicate layer and ocean.
"We find different minerals lose water and volatiles at different depths and temperatures.
"We added up these volatiles that are estimated to have been lost from the interior and found they are consistent with the current ocean's predicted mass - meaning they are probably present in the ocean."
Heating and increased pressure caused by early radioactive decay or later tidal forces would break down minerals and release trapped water - known as 'metamorphism.'
Dr Daswani said: "Europa is one of our best chances of finding life in our solar system."
NASA is planning a mission, dubbed 'Europa Clipper', to look for life in the next few years. A lander will drill for chemical evidence.
Dr Daswani said: "Our work aims to prepare for it. Our models lead us to think the oceans in other moons, such as Europa's neighbour Ganymede, and Saturn's moon Titan, may also have formed by similar processes.
"We still need to understand several points though, such as how fluids migrate through Europa's rocky interior."
He is now working with French and Czech colleagues to investigate if seafloor volcanoes may have fuelled the chloride-rich water on Europa.
NASA has recently released new high-resolution photos of the moon, identifying possible exploration sites.
Almost 2,000 miles wide, Europa is slightly smaller than Earth's Moon. The surface temperature never rises above minus 160 Celsius. The ocean's is unknown.
Planetary and space scientist Professor Monica Grady, of Liverpool Hope University, is convinced life lurks on Europa.
Speaking in February, she said: "When it comes to the prospects of life beyond Earth, it's almost a racing certainty there's life beneath the ice on Europa."
What is more, it will be as complex as an octopus - with similar intelligence. The animal is renowned for being able to solve problems - and remember the solutions.
Prof Grady also thinks there is life to be found in the caverns and caves of Mars that are protected from solar radiation.
Although the idea of octopus-like creatures living on Jupiter's moon may sound far-fetched, it was the plot in the 2013 film 'Europa Report'.
Six astronauts embark on a privately funded mission to find potential sources of life and stumble upon them living beneath the surface.
The Hubble Space Telescope spotted the presence of sodium chloride, also known as table salt, on Europa a year ago. The moon orbits Jupiter every 3.5 days.