Saturn’s moon Titan has many of the ingredients we think are necessary for life. However, a new study argues the separations between them present a drastic obstacle. The amount of life for the whole moon that could depend on the most plausible reaction would fit in the luggage allowance of a passenger flight.
Titan boasts the most Earth-like atmosphere within our solar system, more akin to ours than Venus’s corrosive environment or Mars’s virtually nonexistent one. Even though temperatures are extremely low, there was significant optimism about potential life forms present before the Voyager spacecrafts flew by. However, these missions uncovered that Titan is the only known world aside from Earth where liquids persist at the surface (not counting water ice). Io’s lava ) and lakes composed of rain, which consists of hydrocarbons and lacks the crucial characteristics needed for water to sustain life.
Not everyone gave up on Titan, however, particularly after evidence emerged of an internal ocean , likely composed of water rather than hydrocarbons. In certain aspects, this resemblance might be seen in those of Europa and Enceladus However, certain astrobiologists suggest it could be a more promising option for life. This is due to the possibility that some of the organic matter on the surface might make its way to the ocean.
However, a team headed by University of Arizona PhD student Antonin Affholder has presented what they believe serves as a reality check for those who are overly optimistic. "Our research zeroes in on what sets Titan apart from other icy moons due to its abundant supply of organic material," explained Affholder. statement .
"Titan’s abundance of organic materials suggests an ample supply of potential energy sources for life," Affholder noted additionally. Nonetheless, being classified as organic merely indicates the presence of carbon, which doesn't necessarily mean these compounds serve as nourishment for terrestrial organisms, nor probably do they for entities on Titan too. Furthermore, the extent of interaction between the subsurface ocean and the planet's exterior remains unclear; according to Affholder and colleagues, their interplay might be minimal.
Life is incredibly intricate, making it a monumental challenge to model all its processes; therefore, the group concentrated on fermentation, responsible for producing both bread and beer. According to Affholder, fermentation likely emerged early in Earth’s biological timeline and doesn’t necessitate exploring any mysterious or hypothetical scenarios that might or might not occur on Titan.
The group refined their investigation to focus on fermenters within Titan’s underground sea that consume glycine. They selected glycine due to its status as the most basic amino acid, which can form from prevalent compounds found in Titan’s atmosphere. Additionally, the process of glycinolysis doesn’t require oxidizers, unlike many biochemical reactions essential for life forms elsewhere. This factor is crucial since such oxidizing agents would probably be scarce in an environment akin to Titan’s ocean.
Affholder stated, “We understand that glycine was quite plentiful within the early materials present throughout the Solar System.” He further explained, “If we examine asteroids, comets, as well as the stellar nurseries composed of dust and gases where star systems similar to ours originate, traces of glycine or its building blocks appear almost everywhere.” Organisms capable of surviving through fermentation using glycine thrive in environments inhospitable to most other life forms here on Earth.
However, any organisms in Titan’s oceans dependent on glycine from above would be little Oliver Twist’s desperately asking for more. That’s because Titan’s icy shell is so thick – possibly 300 kilometers (180 miles). This isn’t like Enceladus with crevasses suspected of linking the ocean with the surface .
The same group demonstrated in a previous paper It’s likely that transient links form between Titan's surface and its subsurface ocean since asteroid impacts would cause localized melting of the icy crust, forming pools of liquid water that then descend. Should these watery pools be sufficiently extensive, they could penetrate all the way to the ocean beneath without freezing solid, potentially transporting organic compounds along with them.
However, Titan’s atmosphere means that, just as on Earth, most incoming objects burn up before they hit the surface and even those that don’t lose enough speed to make smaller pools. Consequently, pools big enough to carry all the way to the ocean are probably very rare.
The latest research indicates that these resources might support just a modest microbial community with an overall weight not exceeding several kilograms – comparable to that of a small canine, as stated by Affholder. This limited ecosystem would equate to fewer than one cell per liter across all of Titan’s extensive sea.
For biology to continue thriving under those circumstances might necessitate the scarce glycine being highly concentrated. The team doesn’t address exactly how life may have originated.
This study does not dismiss the chance of life on Titan relying on nutrients from an alternative source; however, under those circumstances, the massive moon ceases to have an edge over similar celestial bodies possessing their own internal seas. These latter typically have such oceans nearer to the surface, making them more accessible and thus seemingly more promising locations to search for life.
The study is available as an open-access resource in The Planetary Science Journal .