Tucson Standard

Saturn's moon Titan, known for its rivers of liquid methane and hazy atmosphere, has long intrigued scientists as a potential host for life. A new study by an international team, including Antonin Affholder from the University of Arizona and Peter Higgins from Harvard University, explores the possibilities of life on Titan. The researchers focused on Titan's organic content, utilizing realistic bioenergetic models to estimate life possibilities.

Affholder noted, "In our study, we focus on what makes Titan unique when compared to other icy moons: its plentiful organic content." The research, published in The Planetary Science Journal, suggests Titan's subsurface ocean, reaching depths of approximately 300 miles, might support life forms that consume organic material. Yet, the study concludes that if life exists, it would be limited to a small biomass, equivalent to the weight of a small dog.

Titan, often compared to Earth due to its surface conditions and interior ocean, is a future exploration target for NASA's Dragonfly mission. Affholder criticized earlier estimates for assuming abundant organics equate to life, explaining, "We point out that not all of these organic molecules may constitute food sources." The study's "back-to-basics" approach considered fermentation as a metabolic process that could exist on Titan, explaining that fermentation uses organic molecules without oxidants like oxygen.

The research specifically examined glycine, the simplest amino acid. Affholder stated, "We know that glycine was relatively abundant in any sort of primordial matter in the solar system." However, simulations indicated only a small portion of Titan's organics might be suitable for microbial use. Glycine-consuming microbes would require a steady glycine supply from the surface through a thick ice shell. The research team previously showed meteorite impacts could create melt pools transferring materials to Titan's ocean.

Affholder highlighted, "Our new study shows that this supply may only be sufficient to sustain a very small population of microbes weighing a total of only a few kilograms at most." The rare potential for life on Titan could result in its ocean having less than one cell per liter of water.

The study suggests finding life in Titan's oceans could be as challenging as seeking a needle in a haystack unless life is not just surface-derived. Funding for the research came from the International Space Science Institute in Bern, Switzerland. "We conclude that Titan's uniquely rich organic inventory may not in fact be available to play the role in the moon's habitability to the extent one might intuitively think," Affholder remarked.