Saturn’s moon Titan is often referred to as one of the worlds in the solar system where life could theoretically exist. A new analysis has shown that this is indeed possible, albeit incredibly unlikely.
Titan is known for being the only moon in the solar system with a dense atmosphere, and for having liquids on it, including liquid water hidden under deep layers of ice. But unfortunately, an international team of astronomers determined that the conditions on Titan could only support enough biomass to sustain one medium-sized cat.
It’s been 20 years since Titan was visited by the Cassini-Huygens mission, a joint effort between NASA, the European Space Agency (ESA) and the Italian Space Agency. While the Cassini probe continued its journey through space, collecting data on Saturn and its moons, the Huygens lander separated to get even closer to one of them. When it descended through the atmosphere and landed on Titan on January 15, 2005, it became the first human-made object to do so.
Although several places have been identified in the solar system that may be habitable, the data collected by the probe indicated that Titan might be one of the most likely candidates. Huygens discovered a dense atmosphere where the chemical processes necessary for the formation of organic compounds (the building blocks of life) could take place.
However, just as an egg yolk is not a chicken, organic compounds do not necessarily indicate that life can form. To investigate the possibility of microbial life on Titan, Antonin Affholder, a postdoctoral researcher at the University of Arizona, led a team that assessed how likely such a scenario might be. They did this by assuming that if life had originated on Titan, it would have survived through one of the most primitive processes known: fermentation, in which the body converts organic compounds into energy without the use of oxygen.
Yes, the process you’ve been carelessly playing around with to make sourdough starter during covid-19 is a sign of life – life that you used to make avocado toast, but life nonetheless.
They determined that the organic compound most likely involved in the fermentation of titanium is glycine, an amino acid valuable for protein building. Glycine has been found on Titan’s surface, but scientists have wondered whether sufficient quantities of it could make it to the moon’s liquid oceans. These oceans – where life would have the best chance of survival – are buried under ice 31 to 124 miles (50 to 200 kilometers) thick.
Unfortunately, the results are not favorable for those hoping to find microscopic extraterrestrials on the distant moon. As the astronomers explained in The Planetary Science Journal, this is not a definitive “no,” but it seems unlikely. At least, if there is life there, it is very, very small. The amount of glycine that would get into liquid water would only be able to hold 16.5 pounds (7.5 kilograms) of carbon. Again, this is the weight at which most domestic cats are on a diet.
“There is a belief that because there is so much organic matter on Titan, there is no shortage of food sources that could sustain life,” Affolder said in a statement. “We point out that not all of these organic molecules can be food sources, the ocean is very large, and the exchange between the ocean and the surface, where all this organic matter is, is limited, so we advocate a more subtle approach.”
“Such a tiny biosphere would average less than one cell per liter of water in the entire vast Titan Ocean,” he concluded.
