If by some remote chance life exists on the surface of Titan, Saturn’s largest moon, one thing is certain: it will not be anything like life on Earth.
The reason is simple. All living things on this planet (assuming you don’t include viruses) comprise at least one cell, all of which feature defining membranes made primarily from lipids.
On Titan, the atmosphere is dominated by nitrogen, lakes and seas are made of methane and ethane, and the temperature hovers around a not-at-all balmy –179˚C. Lipid-encased cells could not survive. {%recommended 868%}
However, there is more than one way to make a membrane, and data from Chile’s Atacama Large Millimetre/submillimetre Array radio telescope has revealed a complex molecule in the moon’s atmosphere fit for purpose.
In a paper published in the journal Sciences Advances, a team led by Maureen Palmer of NASA’s Goddard Space Flight Center report the existence of large quantities of vinyl cyanide (C2H3CN).
On Earth, vinyl cyanide is a colourless, toxic and flammable liquid. Its ability to coalesce into a membrane is exploited in the production of acrylic resins and synthetic rubber.
Reviewing data collected by the Chilean radio telescope up until February 2014, Palmer and her colleagues confirmed and quantified the presence of vinyl cynanide in Titan’s atmosphere. Previous observations from the Cassini spacecraft had hinted at its existence but the team’s spectroscopic analysis provided the first unambiguous evidence.
The molecule is at greatest density some 200 km above Titan’s surface. However, the scientists suggest weather patterns may cause it to circulate vertically in substantial measure.
In particular, they suggest rain-like phenomena might push large quantities of vinyl cyanide downwards, causing it to be trapped in the moon’s lakes and seas.
They estimate Titan’s second-largest ocean Ligeia Mare, which is nearly pure liquid methane, might contain enough vinyl cyanide to produce up to 10 million membranes per cubic centimetre.
“Cell membranes are a crucial component of any living organism,” they write, “and simulations indicate that, at the temperature of Titan’s methane lakes, vinyl cyanide … would form the most stable membranes.”