Saturn’s Largest Moon Most Likely Uninhabitable: Study

News Desk

Islamabad: A research initiative spearheaded by Astrobiologist Catherine Neish from Western University has revealed that the subsurface ocean of Titan, Saturn’s largest moon, is deemed a non-habitable environment.

This conclusion extinguishes any optimism for the possibility of discovering life in this icy celestial body.

The findings of this study significantly diminish the likelihood of space scientists and astronauts encountering signs of life in the outer solar system, where the four ‘giant’ planets—Jupiter, Saturn, Uranus, and Neptune—reside.

The revelation underscores the challenges and limitations in the quest for habitable environments beyond Earth, particularly in the distant realms of our solar system.

“Regrettably, our optimism in the search for extraterrestrial life within our own solar system needs to be tempered,” expressed Neish, a professor in Earth sciences. “The scientific community’s enthusiasm for discovering life in the icy realms of the outer solar system may now face greater challenges than previously anticipated.”

The quest for life beyond Earth in the outer solar system holds immense interest for planetary scientists, astronomers, and space agencies like NASA. This is primarily because many icy moons surrounding the giant planets are believed to harbor substantial subsurface oceans of liquid water.

For instance, Titan is thought to possess an ocean beneath its icy surface that surpasses Earth’s oceans in volume by more than 12 times.

“Life, as we understand it on Earth, relies on water as a solvent, making planets and moons with abundant water crucial in the search for extraterrestrial life,” explained Neish, who is affiliated with Western’s Institute for Earth and Space Exploration.

In their study, recently published in the journal Astrobiology, Neish and her research collaborators set out to quantify the transfer of organic molecules from Titan’s organic-rich surface to its subsurface ocean, drawing insights from data obtained through impact cratering.

Throughout Titan’s history, comets colliding with the moon have caused surface melting, resulting in pools of liquid water that mingled with surface organics. The resulting melted mixture, being denser than the icy crust, sinks through the ice, potentially reaching Titan’s subsurface ocean.

By estimating the rates of impacts on Titan’s surface, Neish and her team calculated the number of comets of varying sizes that would impact Titan each year over its history. This enabled them to predict the flow rate of water carrying organics from Titan’s surface to its interior.

The study revealed that the weight of organics transferred in this manner is relatively small, not exceeding 7,500 kg/year of glycine—the simplest amino acid constituting proteins in life. To put it in perspective, this mass is approximately equivalent to that of a male African elephant.

It’s worth noting that all biomolecules, including glycine, rely on carbon as the backbone of their molecular structure.

“One elephant’s worth of glycine per year into an ocean 12 times the volume of Earth’s oceans is not sufficient to sustain life,” Neish commented. She emphasized that while water has been historically associated with the potential for life, it’s essential to consider other elements, particularly carbon, which is crucial for the molecular structure of biomolecules.

The study’s findings underscore the challenges of transferring carbon from Titan’s surface to its subsurface ocean, highlighting the difficulty of having both the necessary water and carbon for life in the same location.

This poses implications for the habitability of other icy worlds in the solar system, especially those lacking carbon on their surfaces. Titan, being the most organic-rich icy moon, provides valuable insights into the broader understanding of habitability in icy celestial bodies.

What is Titan made of?

Despite the recent findings, much remains to be uncovered about Titan, leaving astrobiologist Catherine Neish with the overarching question: What is Titan made of? Neish, a co-investigator on the NASA Dragonfly project, anticipates answers from a planned spacecraft mission set for 2028.

The Dragonfly mission aims to deploy a robotic rotorcraft (drone) to Titan’s surface to delve into its prebiotic chemistry, exploring how organic compounds formed and self-organized, shedding light on the origins of life on Earth and potentially beyond.

Determining the composition of Titan’s organic-rich surface poses a considerable challenge as traditional telescopic observation is hindered by its organic-rich atmosphere. Neish emphasized the necessity of a direct landing on Titan to sample its surface and unravel its composition.

To date, the Cassini–Huygens international space mission in 2005 remains the only successful endeavor to land a robotic probe on Titan, marking the farthest landing from Earth a spacecraft has ever achieved.

Neish expressed the potential for valuable insights even if the subsurface ocean proves uninhabitable. The exploration of Titan’s surface can provide essential information about prebiotic chemistry, both on Titan and Earth. The focus is on understanding reactions occurring on Titan’s surface, particularly where organic molecules intersect with liquid water produced in impact events.

The Dragonfly mission, with its planned landing on Titan, holds promise for unraveling more of the moon’s mysteries and contributing to our understanding of prebiotic chemistry in extraterrestrial environments.

At the outset of her recent study, Neish harbored concerns about potential negative implications for the upcoming Dragonfly mission. However, the study’s outcomes have not only deepened the understanding of Titan but have also spurred additional inquiries.

Contrary to initial worries, Neish sees the study as a catalyst for more questions rather than a deterrent to the Dragonfly mission. She elaborated, “If all the melt produced by impacts sinks into the ice crust, we wouldn’t have samples near the surface where water and organics have mixed.

These are regions where Dragonfly could search for the products of those prebiotic reactions, teaching us about how life may arise on different planets.”

While the study’s findings paint a more challenging picture regarding the habitability of Titan’s surface ocean, Neish remains optimistic about the prospect of uncovering intriguing prebiotic environments near Titan’s surface.

These regions, where water and organics have interacted, present opportunities for Dragonfly to sample and analyze, offering valuable insights into the potential for life to emerge in diverse planetary environments.

The study has not dampened the enthusiasm for the Dragonfly mission but has rather opened up new avenues for exploration and discovery.