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Life beyond water - cell membranes possible on Saturn's moon Titan

Monday, March 2, 2015

Earth's cell membranes, also known as liposomes, have evolved in a world covered in liquid water. But how might membranes form in a world covered in liquid methane that is so cold that water is a rock? Cornell researchers James Stevenson (PhD candidate) and Paulette Clancy (Samuel W. and Diane M. Professor of Chemical Engineering) with assistance from Cornell astronomer Jonathan Lunine (David C. Duncan Professor in the Physical Sciences) have addressed this question using molecular-scale computer simulations backed by quantum mechanics. Looking at Saturn's moon Titan, with its seas of liquid methane, the Cornell team has discovered a water-free alternative to Earth's liposomes. Called "azotosomes," from the Greek "azoto-soma" (nitrogen-body), these membranes can form using nitrogen compounds already observed on Titan. In Titan's seas, polar C-N bonds fill the role which lipid tails fill in water-based life. Most surprisingly, the ability of the azotosome membrane to stretch is roughly the same as that of terrestrial liposomes, despite the cryogenic temperatures of -290 F. The temperature and chemical differences between liposomes and azotosomes neatly cancel out, producing flexible membranes in hitherto inconceivable conditions. The ability to form cell membranes is often proposed to be the first step in proto-biology, so the stability of these membranes offers intriguing evidence that life can arise via routes utterly different from ours. As Isaac Asimov wrote, and the computer models of Stevenson, Lunine and Clancy have now shown: "When the cautious astronomer speaks of life on other worlds with the qualification 'life-as-we-know-it,' we become impatient. What about life-not-as-we-know-it?"

For more details read:
The original paper can be found at: Science Advances 27 Feb 2015: Vol. 1 no. 1 e1400067,

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