Covered with liquid methane, icy rocks and soot-like “sand” dunes, Saturn’s moon Titan has long fascinated scientists and led to speculation as to whether life forms might lurk in a thick, hazy atmosphere.
An international team of researchers have sought to develop a realistic scenario of what Saturn’s moon life looks like, where it is most likely and how much it exists.
“Our study focuses on what makes Titan unique when compared to other ice moons. Its rich organic content” explained Antonin AFFOLDER of the Arizona University Bureau of Ecology and Evolutionary Biology and is the lead author of the study.
Evidence of small amounts of life in the seas of Titan
Using bioenergy modeling, the team discovered that Titan’s underground ocean, estimated at around 300 miles, could support life forms that consume organic materials.
They discovered that while Titans could have a simple, microscopic life, they could only support a few pounds of biomass overall.
Often called “the inner ocean world, like the surface Earth,” Titans are the targets of future exploration through NASA’s Dragonfly mission. Researchers speculate about scenarios that could generate organisms in Titan based on abundant organic chemistry, but previous estimates suffer from what affolder considers an oversimplification approach.
“Because Titan has such abundant organic matter, there was a sense that there was no shortage of food sources that could sustain life,” he said.
“I’ll point out that not all of these organic molecules constitute a food source. The ocean is really big and there is a limited exchange between the ocean and the surface.
Returning to basics through fermentation
At the heart of the research is a fundamental approach that attempted to come up with a plausible scenario for Saturn’s moon life. This envisioned the simplest and most prominent fermentation of all biological metabolic processes.
For the use of sourdough in its role in breadmaking, brewing beer and ruining forgotten leftovers, fermentation familiar to people on Earth requires only organic molecules, but no “oxidants” such as oxygen.
Affholder said: “Fermentation probably evolved early in the history of Earth’s life, and there is no need to open the door to unknown or speculative mechanisms that may or may not have happened in Titan.
“We asked if Titan has similar microorganisms. If so, could Titan’s underground oceans supply the biosphere from a seemingly vast inventory of abiotic organic molecules synthesized in Titan’s atmosphere, accumulate on its surface and be present in its core?”
Only a small amount of Titan microorganisms can support your life
The researchers have focused specifically on glycine, the simplest organic molecule of all known amino acids.
“We know that glycine is relatively abundant in all kinds of primitive matter in the solar system,” affolder said. “When you look at clouds of particles and gases where stars and planets form, like asteroids, comets, our solar system, we find glycine or its precursors in almost every place.”
However, computer simulations reveal that only a small fraction of Saturn’s moon’s organic material may be suitable for microbial consumption. Microorganisms that consume Titan’s sea glycine rely on a stable supply through thick, ice-like shells of amino acids from the surface.
Previous studies by the same team showed that metstones that impact ice could leave behind “melting pools” of liquid water.
Overall, this new study shows that this supply may be sufficient to maintain very few microorganisms in just a few kilograms of microorganisms. Such a small biosphere is less than one cell per liter on the vast oceans of Titan.
Knowledge of Saturn’s future missions to the moon
For Saturn’s future mission to the moon, the possibility of finding life might be like searching for needles in a haystack, if in fact it’s there.
“We conclude that Titan’s unique, rich organic inventory may not be available to play a role in the habitability that we may intuitively consider in lunar livability,” concluded abbholder.
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