If life really exists on Titan, as the media reported this week, its chemistry will be very different from that of life on Earth. Beginning with the fact that there is no water on Titan, this great moon of Saturn.
The keyword behind the discovery described on July 28 in the journal Science Advances is "membrane", that is, the thin film that protects the living cell from the external environment. On Earth, the membranes of our cells, like those of all living organisms, are composed of molecules called lipids. But lipids could not survive in a waterless world. Would there be an alternative in a world where there are oceans of hydrocarbons, as is the case there? This is the question that biologists have been asking since we know that there is liquid on Titan.
One hypothesis is that vinyl cyanide (or acrylonitrile) can be used for such membranes: and this is what the observations revealed in Science Advances tend to confirm. Astronomers have detected this vinyl cyanide in very large quantities in Titan's atmosphere, thanks to observations of the ALMA (Atacama Large Millimeter / submillimeter Array) telescope, in Chile, enough to estimate that 10 million of these molecules Could fall in rain in every cubic centimeter of ocean. The estimate is perhaps optimistic, admits in Space.com the principal researcher, Maureen Palmer, of the Goddard Center of NASA. But the detection of this membrane would fulfill one of the three conditions necessary for the presence of life on Titan:
Something to protect the material that constitutes life-that's what they may have found;
A form of internal energy source or chemical reactions to keep the body alive and reproduce - what biologists call metabolism;
And something to convey information - like our genes. It is currently impossible to know more about the other two conditions.