Could the moon of another planet be a source for life as we know it?
Antonin Affholder, post-doctoral researcher at the University of Arizona, discusses.
Faculty Bio:
Antonin Affholder obtained his PhD from the École Normale Supérieure, in Paris, France, working on developing models of ecosystems on other worlds to assess their habitability and to research biosignatures. He then moved to Tucson to become a post-doctoral researcher at the University of Arizona, focusing on microbial ecosystems degrading soil organic matter.
Transcript:
Saturn’s largest moon is a strange world. Under a thick, icy shell lies a vast ocean. Titan has an atmosphere, dunes of sand-like organic material and lakes of hydrocarbons. As alien as it seems, Titan may be similar to the early Earth when its atmosphere was hazy with organic molecules undergoing all kinds of chemistry, driven by sunlight.
Early life on Earth could have fed on organic matter of non-biological origin before learning how to turn carbon dioxide into complex organic compounds.
Titan has no oxygen, so instead of relying on respiration like we do, microbes could use fermentation to extract energy from organic matter. Fermentation is how beer and yogurt are made. But carbs, the molecules used in the process, probably don’t exist on Titan. Most organics there are hydrocarbons – like tar or plastic– not something that’s typically fermented by the microbes that we know.
But, Titan likely has one class of molecules that we know can be fermented: amino acids. The simplest is glycine, so we designed a computer simulation of glycine fermenting microbes, using data from actual bacteria.
On Titan, there aren’t many ways for glycine to get into the ice-covered ocean, where life is most likely to occur. A previous study indicates “melt pools” blasted by meteorites could sink through the ice shell and take glycine with them.
Our model estimates the amount of glycine that could reach the ocean could sustain a minuscule population of microbes – no more than the mass equivalent of a small dog.
We conclude that Titan’s most striking feature-its organic-rich surface-may not hold as much potential for life as previously thought. Instead, we must investigate other processes that could support life, such as the circulation of hot water in the rocky core, to fully assess Titan’s potential for life.
