How alien life might look on Saturn's moon Titan

Alien lifeforms may exist in the solar system but they would look very different to life on Earth, scientists have suggested.

A new type of methane-based, oxygen-free life form that can survive and reproduce in a similar way as cells on Earth has been modeled by a team of researchers.

Chemical engineers and astronomers have calculated a form of life which could thrive in the harsh, cold world of Titan, the giant moon of Saturn.

Because Titan is bathed in seas of liquid methane, they speculate that the moon could harbour methane-based, oxygen-free cells.

The new lifeform is made from organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero.

The work was led by chemical molecular dynamics expert Professor Paulette Clancy and James Stevenson, a graduate student in chemical engineering at Cornell University in the US.

Prof Clancy said: "We're not biologists, and we're not astronomers, but we had the right tools.

"Perhaps it helped, because we didn't come in with any preconceptions about what should be in a membrane and what shouldn't.

"We just worked with the compounds that we knew were there and asked, 'If this was your palette, what can you make out of that?'"

On Earth, life is based on a water-based membrane, that houses the organic matter of every cell.

Astronomers usually look for life in habitable zones, where liquid water coud exist. But the scientists tried to come up with life which could be based on methane, which has a much lower freezing point.

The engineers named their theorised cell membrane an "azotosome" - "azote" being the French word for nitrogen. "Azotosome" means "nitrogen body."

The azotosome is made from nitrogen, carbon and hydrogen molecules which are known to exist in the seas of Titan. The chemical engineers looked for compounds which could self-assemble into membrane-like structures needed for cellular life.

The most promising compound they found is an acrylonitrile azotosome, which showed good stability, a strong barrier to decomposition, and a flexibility similar to that of phospholipid membranes on Earth.

Prof Clancy said the next step is to try and demonstrate how these cells would behave in the methane environment, and how they would reproduce in an oxygen environment.

Mr Stevenson said he was in part inspired by science fiction writer Isaac Asimov, who wrote about the concept of non-water-based life in a 1962 essay, "Not as We Know It."

He added: "Ours is the first concrete blueprint of life not as we know it."

The research was published in the journal Science Advances.