Nitrogen-Based Life is Possible on Titan!

Since the Huygens probe dropped down to the surface of Saturn’s largest moon Titan, astronomers have pondered the idea of life on the distant world.  With a liquid cycle not unlike Earth’s water cycle in form, but consisting of frigid liquid hydrocarbons, could a new variation of life exist, not as we know it?

Credit: James Stevenson

Jonathan Lunine, director for Cornell’s Center for Radiophysics and Space Research, is an expert on Saturn’s Moons and is a scientist on the Cassini-Huygens mission, which originally discovered the Methane-Ethane lakes on Titan a decade ago.  Given a grant to study non-aqueous life, he needed help.  Lunine looked to other Cornell faculty, specifically chemical molecular dynamics expert Paulette Clancy and chemical engineering graduate student James Stevenson.

On Earth, the phospholipid bilayer membrane, a permeable water-based structure, is the housing for organic material in every cell.  A vesicle made from this membrane is called a liposome (from the Greek for ‘lipid body’).  This is why we search habitable zones of stars to find life.  Liquid water is required for the liposome.

The researchers took this idea and used Methane as a base molecule instead of water, and used an algorithm to search for Methane-based compounds that has a tendency for self-assembly into membrane-like structures, analogous to the liposome.  They called all of their resulting structures azotosome, in Greek meaning ‘Nitrogen Body,’ since the molecules were Nitrogen-based rather than Oxygen-based, as in Earthbound life.

The best candidate molecule was an acrylonitrile azotosome, which amazingly is already present in Titan’s atmosphere!

Acrylonitrile azotosome showed good stability, a strong barrier to decomposition, and a flexibility similar to that of phospholipid membranes on Earth. Acrylonitrile is a colorless, poisonous, liquid organic compound used in the manufacture of acrylic fibers, resins and thermoplastics here on Earth

Excited by the result, the researchers say the next step is to try and demonstrate how these cells would behave in the methane environment.  How would they replicate? How would they interact with other chemicals? It’s almost as if we’ve started making synthetic Nitrogen-based life before we’ve even discovered it!

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