11.08.2017 change 11.08.2017

Life in liquid methane on Titan? Why not!

Photo: Fotolia Photo: Fotolia

A few years ago, astrobiologists came up with the idea how, at least theoretically, life could appear in the methane lakes on Titan, Saturn\'s moon. It has now been discovered that there is acrylonitrile on Titan, a compound that could be of great assistance in creating such a strange life.

Maybe life does not have to have a familiar form? What if somewhere in the Universe life has appeared in an environment where there is neither liquid water nor oxygen? Astrobiologists do not ignore any clues that could lead them to a trace of unknown organisms.

Titan - the largest moon of Saturn - triggers their imagination. This body is blue even larger than Mercury. Titan has an atmosphere, denser than Earth\'s atmosphere. On top of that there are liquid lakes on the surface of satellite. It\'s a pity that they are filled with liquid methane and ethane ... At the temperature of approx. 180 degrees Celsius.

But not all researchers are discouraged from looking for traces of life there. In 2015, James Stevenson and colleagues conducted a simulation to find out whether life could exist in such conditions. And as it turned out - there is a small chance (http://advances.sciencemag.org/content/1/1/e1400067/tab-article-info).

AZOTOSOMES - POTENTIAL CELL MEMBRANES

For that, there would have to be compounds in the lakes of methane that would act as cell membranes and separate the precise cellular chemical machinery from the environment. Under earth conditions liposomes perform this function. These are phospholipid bubbles that are not permeable to water. Membranes of our cells are built of them.

But in the lakes of liquid methane cell membranes would have to work quite differently. They would have to be built of azotosomes - membranes that would be stable in liquid methane. Acrylonitrile would be a great candidate for an azotosome. But it was unknown whether the substance was present at Titan.

Recent research conducted by Maureen Palmer and colleagues, published last Friday in Science Advances (http://advances.sciencemag.org/content/3/7/e1700022), dispels doubts - acrylonitrile is indeed present in Titan\'s atmosphere. There is enough of this substance on Titan so that it could dissolve in methane lakes and - at least in theory - form... millions of cell membranes per cubic centimetre. And that\'s really a lot.

Prof. Zbigniew Kisiel from the Institute of Physics, Polish Academy of Sciences in Warsaw was involved in the research project.

TOXIC PARTICLE - A SOURCE OF LIFE?

The researcher from the Institute of Physics PAS said in an interview with PAP that acrylonitrile does not quite look like a substance that would support life. "In Earth conditions it is a flammable, poisonous liquid" - explained Prof. Kisiel. Acrylonitrile is useful in the production of synthetic resins and plastics used in construction and automotive industry.

The molecules of this compound have a valuable property - they can polymerize and, under low temperature conditions, aggregate, creating a kind of membrane. "In addition, acrylonitrile can be formed as a result of a series of simple chemical reactions from nitrogen and methane, and these are the basic elements that form Titan\'s dense atmosphere" - explained Prof. Kisiel.

That was the reason why scientists were looking for this compound on Titan with such hope. Now it has been confirmed that acrylonitrile does exist on Titan.

IN THE NETWORK OF RADIOTELESCOPES

"Acrylonitrile was detected on Titan by the radio telescope network ALMA, the most powerful tool for astrophysical spectroscopy" - says Prof. Kisiel. He added that the network collects waves with characteristic frequencies from the selected part of the cosmos. "With radio telescopes we can measure the rotational spectra of gas molecules in distant objects" - said the physicist. He explained that from this data physicists can read the chemical "fingerprints" of molecules present in a given region of the universe.

But in order to know what has been detected, you have to have a database of such "fingerprints". Professor Kisiel, who deals with laboratory spectroscopy, carefully examined the acrylonitrile molecules and determined their properties. Thanks to his research, US researchers were able to find traces of this compound in the ALMA data.

"Earlier, scientists identified a brick that appeared to be optimal for the formation of azotosomes - potential cell membranes - on Titan. We have confirmed that the desired compound - acrylonitrile - indeed exists there, and there is quite a lot of it" - concluded Prof. Kisiel.

PAP - Science and Scholarship in Poland, Ludwika Tomala

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