A molecule that might form cellular structures discovered on Titan

Titan and a vinyl cyanide molecule (Image B. Saxton (NRAO/AUI/NSF); NASA)
Titan and a vinyl cyanide molecule (Image B. Saxton (NRAO/AUI/NSF); NASA)

An article published in the journal “Science Advances” describes the detection of vinyl cyanide molecules on Titan, one of the planet Saturn’s moons. Using archive data of observation carried out with the ALMA radio telescope between February and March 2014, a team of researchers found evidence of the presence of those molecules in significant amounts. The importance of the discovery is due to the fact that it’s a substance considered to be among the best candidate for the formation of membranes and vesicles similar to those of Earth organisms’ cells.

Vinyl cyanide, also commonly known as acrylonitrile or with other names, is a monomer that has its importance in the synthesis of plastic materials. However, in an environment such as Titan’s lakes and seas, it’s considered an important molecule for its astrobiological potential, meaning that for the possibility that it’s part of a local biochemistry in the event that there are life forms on that moon.

The existence of vinyl cyanide on Titan was inferred by analyzing mass spectrometry data collected by the Cassini space probe but there was no direct evidence. The ALMA (Atacama Large Millimeter / submillimeter Array) radio telescope, inaugurated in March 2013, is typically used to observe distant galaxies but its power and sensitivity can also be exploited to study relatively close objects. Instead of looking for the “signatures” of molecules contained in interstellar clouds or in distant galaxies millions if not billions of light years away, it was used to find them in what is astronomically the neighborhood.

Titan has been considered for many years one of the most interesting moons of the solar system and perhaps was the most interesting before the discoveries about Europa and Enceladus. Titan is a moon where it’s very cold, with average temperatures around -290° Celsius or 95 Kelvin, and that’s why there are lakes and seas of methane and ethane along with many other organic molecules. They’re generated by non-biological processes but their presence makes them similar to primordial Earth.

On Titan it’s too cold for Earth-like life forms to develop but many scientists hypothesized some different types of biochemistry. To be clear, vinyl cyanide is toxic and also carcinogenic to human beings and other Earth’s species but might be part of a very different kind of life forms on Titan.

The Cassini mission originally had among its own goals Titan’s study to see if those assumptions had actual substance and only later the discoveries on Enceladus, another moon of Saturn covered by a layer of ice but with a underground ocean of liquid water, stole at least part of the missions time from Titan.

The unique environment of Titan’s hydrocarbon seas may be suitable for the formation of some type of membrane and vinyl cyanide could be a key substance in that type of biochemistry. Between February and May 2014, the ALMA radio telescope was used to observe Titan and studying the data collected Maureen Palmer of NASA’s Goddard Space Flight Center and her colleagues found the chemical signature of vinyl cyanide in this moon’s atmosphere at an altitude of at least 200 kilometers.

Titan’s atmosphere is a kind of chemical factory because the sunlight that reaches this moon is dim but has enough energy to turn simple organic molecules into more complex substances. The vinyl cyanide generated in the atmosphere condenses in colder areas and falls to the ground as rain. This way it can enrich the hydrocarbon seas and lakes.

We’re still very far from understanding if some type of biochemical or at least prebiotic reactions are actually happening on Titan. Certainly, the confirmation of the presence of vinyl cyanide is very interesting because it offers new possibilities to study an environment that is extremely different from the Earth but also from the ocean of Europa and Enceladus and to try to figure out if life forms totally different from the Earth’s ones can really emerge.

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