February 2, 2018 : Researchers Confirm The Presence Of Vinyl Cyanide High In Titan's Atmosphere And Suggest It May Play A Key Role In The Development Of A Potential Methane-Based Life
Scientists from NASA have confirmed, on the basis of data obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) located in the desert of Chile, the presence of vinyl cyanide at a high altitude in the atmosphere of Saturn's largest moon Titan. Vinyl cyanide is an organic molecule whose chemical formula is C3H3N. The identification of vinyl cyanide in the opaque atmosphere of the Hazy Moon is captivating because researchers believe that vinyl cyanide may represent a key molecule in the development of a potential methane-based life on the giant moon. Molecules of vinyl cyanide in an hypothetical methane-based life on Titan may represent the equivalent of well-known phospholipids in the structure of typical cell membranes in our biosphere. The data from ALMA were in line with the data obtained from the mass spectrometer of the Cassini spacecraft which had led researchers to deduce the presence of vinyl cyanide in the environment of Titan.
Thanks to radar data acquired from the Cassini spacecraft, in particular, we have discovered exotic environments on Titan which are reminiscent of typical environments on Earth. There are mountains, hills, canyons, lakes, seas, rivers and islands on the Opaque Moon. Most lakes or seas are found at high latitudes on the giant moon. The high latitudes of the northern hemisphere appear to be the most humid areas at the present time with major seas or lakes like Kraken Mare, Ligeia Mare or Punga Mare. The first body of surface liquids clearly identified on Titan was Ontario Lacus, a kidney-shaped lake or sea located in the high latitudes of the southern hemisphere. Titan unveils a methane cycle implying evaporation processes, condensation processes, cloud formation and rainfall. Water can't appear in its liquid form on the surface of Titan since the environmental temperature is around minus 179 degrees Celsius or minus 290 degrees Fahrenheit. Can liquid methane play the same role as liquid water on Earth for the development of a biosphere on Titan ? Is there a methane-based life on the Orange Moon ?
Some researchers imagine that Titan could host a basic life form based on liquid methane or liquid ethane because there is a meteorological cycle like on Earth and because Titan is rich in organics or hydrocarbons. Can liquid methane or liquid ethane represent efficient solvents for the development of an exotic life form on Saturn's largest moon ? Scientists try to imagine or to simulate the chemical interactions or the chemical soup that can lead to life on Titan, on the basis of our knowledge regarding the chemistry and the physics of Titan. For instance, what kind of cell membrane may we find in the hypothetical creatures of Titan ? Would we find cell membranes composed of phospholipids like in our biosphere ? Phospholipids represent molecular chains containing phosphorus-oxygen heads and carbon-chain tails that connect to each other to generate a flexible membrane in water. The pools of liquid methane on Titan appear to be devoid of phosphorus or oxygen. That's why a potential methane-based life on Titan would have to use other elements or compounds. Vinyl cyanide, which was identified or confirmed via the highly sensitive eye of ALMA, seems to be the perfect molecule for the development of any cell membrane in a biosphere based on liquid methane or liquid ethane.
Maureen Palmer, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, is part of the team who performed the study regarding the identification and the potential role of vinyl cyanide in the environment of Titan. Maureen Palmer led the work of a paper describing the study in Science Advances. She gathered archival data and determined the presence of the organic molecule vinyl cyanide at a high altitude in the deep atmosphere of the Opaque Moon. Vinyl cyanide was identified at altitudes higher than 200 kilometers above the ground and the organic compound appeared to be mostly concentrated above the southern pole of the Hazy Moon. Can a microscopic life form based on liquid methane or liquid ethane develop in the region of Ontario Lacus ? Is vinyl cyanide involved in the chemistry of the hypothetical life form ? The team of Maureen Palmer carried out a modeling work that revealed that there is enough vinyl cyanide in the north polar lake or sea Ligeia Mare to produce approximately 10 million cells per cubic centimeter, about 10 times more than the amount of bacteria thriving in coastal oceans on our planet.
Maybe one day, we'll manage to demonstrate that vinyl cyanide can play a major role in the development of any methane-based life on Titan but at the present time, that scenario is just an hypothesis based on simulations or analyses. A previous analysis led by Cornell University scientists and released in Science Advances had clearly shown that the hypothesis for a methane-based life involving vinyl cyanide was a serious possibility. The work was led by Paulette Clancy who is a Professor of Chemical and Biological Engineering. Paulette Clancy and her collaborators simulated a potential biological environment without liquid water. The typical lipid bilayer membrane can't take shape in the environment of Titan's seas or lakes dominated by liquid methane or liquid ethane. However, vinyl cyanide seems to represent an interesting molecule or even the most interesting molecule for the development of any cell membrane in the hypothetical biosphere of Titan. The cell membranes taking shape in the exotic creatures of the Orange Moon and hypothesized by the team of Paulette Clancy are known as azotosomes. Azotosomes are likely to appear in an environment of liquid methane.
Planetologists believe that any cell membrane taking shape in the organisms of the pools of liquid methane or liquid ethane in the high latitudes of the Hazy Moon would probably be composed of nitrogen, hydrogen and carbon rather than phosphorus and oxygen which are absent or quasi-absent in the methane seas or lakes. Nitrogen, hydrogen and carbon are widespread on the Orange Moon. For instance, the Titanian atmosphere is mostly composed of molecular nitrogen and contains significant concentrations of methane especially at a low altitude. Some molecular modeling studies mobilizing various molecules composed of nitrogen, carbon and hydrogen have demonstrated that the vinyl cyanide molecule may be the best compound to produce a stable and flexible membrane in the environment of Titan. The cell membrane of any biological life form in the lakes or seas of Titan should have the same properties or qualities as the typical cell membranes in our biosphere. Chemical reactions in the hypothetical biological system of the Orange Moon are likely to be particularly slow due to extremely low environmental temperatures.
Any life form mobilizing vinyl cyanide would have to find ways to remain flexible, stable and to produce and manage its own energy in an environment where solar radiations are particularly weak. Yet, Maureen Palmer pointed out that « if membranes can be made in a lab with a simulation of Titan's ocean conditions, it would make us more optimistic about them really forming on Titan. » She added that because of its complex haze or varied atmospheric soup and because of its pools of surface liquid dominated by liquid hydrocarbons, the Opaque Moon is « an interesting chemical laboratory to study the boundaries of possible biochemistry for creating life. » Paulette Clancy advanced that the lab discoveries of Maureen Palmer were « an exciting validation of our prediction, since they also find that the concentration of vinyl cyanide is considerable enough to make self-assembly into azotosome-like vesicles a viable process. » She concluded : « It also shows the power of molecular simulation to shine a flashlight onto the most promising candidates for prebiotic life in conditions that are difficult to emulate in the lab.»
Researchers are particularly interested in the chemistry of organics on Titan because complex interactions between UV light from the Sun and hydrocarbons or organics in the upper atmosphere of the Hazy Moon occur and because there are pools of liquid hydrocarbons at high latitudes. The pools of methane or ethane can act as solvents for any potential life form like liquid water on Earth. Even if there is not any life form on Titan, the environment of the Opaque Moon is likely to produce complex molecules which may help us better understand the complex puzzle or lego game which can lead to life. Do the hypothetical organisms of Titan mobilize some amino acids we know on Earth ? What is the structure of their biological code if they are devoid of any typical DNA ? Do they use vinyl cyanide for the structure of their cellular membranes ? The study of Maureen Palmer was supported by the NASA Astrobiology Institute via funding granted to the Goddard Center for Astrobiology and by the National Science Foundation. The Cornell study was financed by a grant from the Templeton Foundation to perform a research work on non-water-based life.
The image above represents a portion of a radar swath captured from the Radar Mapper of the Cassini spacecraft during the T29 Flyby of April 26, 2007. One can notice the sharp contrast between the land which appears irregular or bright and the pools of liquids which appear dark and relatively uniform. A remarkable network of large interconnected drainage channels can be seen in particular. Some islands can be observed as well. Is there a life form based on liquid methane or liquid ethane in that humid environment ? Do the hypothetical creatures mobilize vinyl cyanide in their metabolism ? Image Credit: NASA/JPL/Cassini RADAR Team/Jason Perry.
- To get further information on that news, go to: https://www.astrobio.net/alien-life/titans-hydrocarbon-soup-hold-recipe-life.