PHYS.org by Thamarasee Jeewandara 2/7/2020
Astrobiologists are focused on resolving two central questions to understand the environmental and chemical limits of life. By understanding life's boundaries, they intend to identify possible biosignatures in exoplanet atmospheres and in the solar system. For example, the lipid bilayer membrane is a central prerequisite for life as we know on Earth. Preceding studies based on simulations of molecular dynamics have suggested that polarity-inverted membranes known as azotosomes made of small nitrogen-containing molecules may be kinetically abundant on cryogenic liquid worlds such as Saturn's moon Titan.
In a new report on Science Advances, H. Sandström and M. Rahm at the department of Chemistry and Chemical Engineering at the Chalmers University of Technology, Sweden, formed a next potential step to investigate the thermodynamic viability of azotosome formation. Using quantum mechanical calculations, they predicted that azotosomes are unable to self-assemble in liquid water unlike lipid bilayers. They propose that due to stringent anhydrous and low-temperature conditions, cell membranes may be unnecessary for hypothetical astrobiology on Titan. These efforts on predictive computational astrobiology will be of importance for the Dragonfly mission's scheduled landfall on Titan in 2034.
Saturn's moon Titan features rich atmospheric chemistry and a dynamic surface morphology driven by seasonal rainfall predominantly of methane and ethane cycles. Scientists have observed hydrocarbon lakes and seas near the polar regions of Titan to draw comparisons with the hydrologic cycle of Earth relative to the origin of life. The surface conditions of Titan are, however, a frigid 90 to 94 K and in contrast to Earth, Titan's outermost surface is free of oxygen and covered by products of its atmospheric photochemistry. Researchers also suspect the presence of a frozen water ice crust underneath the outermost organic layer. As the strictest test for the limits of life, Titan offers a unique environment to explore the chemical complexity of nature and its progression without liquid water at low temperatures at timescales nearing the age of the solar system.
More:
https://phys.org/news/2020-02-polarity-inverted-membranes-self-assemble-saturn-moon.html
