Titan is a hostile, icy world, that harbors vast oceans of liquid methane and ethane and a toxic atmosphere without any signs of liquid water. Scientists have proven that according to current biological understandings, carbon-based life cannot exist without the presence of liquid water. Therefore, the chances of any life as we know it being found on Titan, one of Saturn’s moons, is absolutely zero. However, what if life as we do not know it could be thriving under Titan’s thick oceans of solid methane? Well, scientists may have an answer to this mindboggling question.
Generally, astrobiologists consolidate what they know about the Earth’s biosphere and their findings on other worlds far outside the Solar System in hope that an exoplanet may have some characteristics that favor carbon-based life. As of now, astrobiologists have been searching for exoplanets that orbit their host star just far away and just close enough in the “Goldilocks zone” – the area in which the presence of liquid water is most favorable. The premise of their search is based on finding a “second Earth”. Though, their idea of “following the water” to find alien life may limit the scope of terrestrial worlds that may exist.
Titan does not fall into this category; it is about un-Earth-like as astrobiologists can find. In light of this, Paulette Clancy, a molecular dynamics expert, and James Stevenson, a graduate chemical engineering student, both from Cornell University, have created a theoretical model of an oxygen-free, nitrogen-based life form that could possibly live on Titan.
The two researchers focused on creating a cell membrane composed of nitrogen compounds that are able to function in the environment on Titan which is below 292 degrees Fahrenheit – the temperature at which methane is in a liquid state. They said on Earth, water-based chemical compounds form phospholipid bilayer membranes – giving the cell the permeability to house and disperse water from inside the cell. They explained this would be impossible in the environment on Titan because liquid water is not present to build the aforementioned cell membrane structures. Clancy, the head researcher of the study, said their model facilitated positive theoretical results since they did not begin with any preconceived notions on how life can be created.
The researchers we able to create the model to emulate the metabolism and reproduction a life form must accomplish, but constructed from nitrogen and hydrogen-based compounds that have been proven to exist within the liquid methane seas below the frigid world of Titan. This chemical compound configuration gives the theoretical other-world cell the flexibility and the stability which can be mirrored by organelles on Earth.
The word liposome, the liquid body that surrounds the cell to create the membrane, is formed from the Greek word “lipos”, meaning liquid, and “soma” meaning to breath. Therefore, Clancy and the team named the theoretical cells an “azotosome”, “azote” being the French derivative for nitrogen.
By identifying a theoretical type of cell membrane that could survive in Titan’s environment, as cell on Earth might, the next step for the research team is to create a model of how a hypothetical type of life form would function on Titan. They said they might be able to show some types of observable indicators astrobiologists need to look for to reveal the presence of life forms on Titan and exoplanets throughout the galaxy.
By Alex Lemieux
Photo by Bill Lile – Flickr License