Awash with seas of liquid methane, Saturn's moon Titan could harbour methane-based, oxygen-free life, guess scientists.

A team of Cornell University researchers have modelled a 'different' type of life form - which is oxygen-free and methane-based - that can metabolise and reproduce similar to life on earth.

Their theorised cell membrane is composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero.

"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'," said lead researcher Paulette Clancy.

On Earth, life is based on the phospholipid bilayer membrane, the strong, permeable, water-based vesicle that houses the organic matter of every cell.

A vehicle made from such a membrane is called a liposome. Thus, many astronomers seek extraterrestrial life in what's called the circumstellar habitable zone, the narrow band around the sun in which liquid water can exist.

But what if cells weren't based on water, but 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.

The azotosome is made from nitrogen, carbon and hydrogen molecules known to exist in the cryogenic seas of Titan, but shows the same stability and flexibility that Earth's analogous liposome does.

The engineers employed a molecular dynamics method that screened for candidate compounds from methane for self-assembly into membrane-like structures.

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.A

Acrylonitrile - a colourless, poisonous, liquid organic compound used in the manufacture of acrylic fibres, resins and thermoplastics - is present in Titan's atmosphere.

Excited by the initial proof of concept, Clancy said the next step is to try and demonstrate how these cells would behave in the methane environment - what might be the analogue to reproduction and metabolism in oxygen-free, methane-based cells.

The study was published in Science Advances.