A team of scientists at Cornell University are convinced that Titan, one of Saturn’s moons, could harbor life, however, not in the form that we all know it. Methane-based life forms could exist on Saturn’s moon, the team of scientists claims, after constructing a solid model of an oxygen-free life form which could thrive in the icy, harsh conditions that Titan provides.
After studying the types of cell membranes encountered on Earth, which consist of lipid-bilayer structures, the team of Cornell scientists explained that such membranes wouldn’t be suitable in an environment where liquid water wouldn’t exist.
Possible Structure for Other Types of Cell Membranes
Saturn’s moon, for instance, has an abundance of methane-filled lakes, so that it may not be a habitable zone in the way that we have previously defined habitability. However, James Stevenson and his colleagues believe that differently structured membranes would provide the basis for life to exist on Titan. Their model used small organic nitrogen compounds, so that the newly-obtained structure could perfectly function on Titan: at cryogenic temperatures and in the abundance of methane in liquid form found on the moon.
The team than began running simulations, hoping to prove that such a nitrogen membrane could compare against Earth’s characteristic lipid bilayered membranes when considering elasticity and stability.
According to lead study author, James Stevenson, it was Isaac Asimov, the renowned sci-fi writer, who provided the basic inspiration for the concept in his “Not as We Know It” essay on non-water-based life forms. Because Titan is, apart from Earth, the only known celestial body in our solar system to present naturally occurring liquids on its surface (in the form of liquid methane), the team of scientists (fueled by previous research) considered it a perfect cradle for possible life forms to develop.
Dr. Paulette Clancy, who led the team, managed to construct an “azotosome”. Similar in name origin to “liposome” which stems from the Greek words “lipos” and “soma” (meaning “lipid body”), an azotosome stems from the French word for nitrogen. Consequently, the word describes a nitrogen body.
Organic Nitrogen Compound Membrane Characteristics
By constructing this organic nitrogen compound, which also contains carbon and hydrogen molecules, the team of scientists stepped out of the box where the majority of scientists had been running in. Instead of seeking alien life within the circumstellar habitable zone (or the area surrounding the Sun where water in liquid form is able to exist), the team simply imagined a different type of cell, based on methane instead of water. Clancy and her colleagues were stunned that this new proposed model presented a similar stability to the cell membranes found here on Earth.
“We’re not biologists, and we’re not astronomers, but we had the right tools,”
Clancy mentioned, while also noting that the lack of preconceptions that the team started off with may have actually worked in the team’s favor. Instead of questioning each step that the team made, Clancy added, the researchers simply asked themselves what would be possible with the palette of elements that had been put at their disposal.
What the team did in order to obtain these models was to employ molecular dynamics methods. Candidate compounds then emerged as possibly self-assembled membrane-like structures, however, among the many candidates, the acrylonitrile azotosome was by far the most promising structure.This azotosome wasn’t only particularly stable, it also provided a powerful barrier against decomposition and showed a similar elasticity to phospholipid membranes found on Earth. This poisonous organic compound is present in Titan’s atmosphere, the research team said.
Further Directions in Searching for Life on Titan
After coming this far, Dr. Clancy seemed excited to continue the team’s work and understand how such compounds would actually work in the methane environment. If cells did indeed possess such membranes, could it be possible that they would also develop analogue mechanisms of metabolism and reproduction despite the lack of oxygen?
Dr. Jonathan Lunine, an expert in Saturn’s moons and co-author of the study, believes that it may be possible in the future to actually test such theories by sampling organic material from Titan itself. Perhaps, in the years to come, Lunine explained, probes could be sent to Saturn’s moons and collect the required material by floating on the methane seas of Titan.
Image Source: NASA , Daily Galaxy and Sci News, (Image Credit James Stevenson et al.)