Saturn’s Moon Titan May Host The Building Blocks Of Life

Recently, I finished reading Stephen Baxter’s science fiction novel entitled “Titan.” Published in 1997, before NASA’s shuttle error had come to an end, the story takes place in an America between 2004 and 2016 where anti-science and anti-intellectualism dominate the political and social landscape.

After a NASA shuttle crashes on landing, the government slashes funding to the agency. NASA scientists and engineers decide to launch one more mission, a Hail Mary to Titan, based on findings from the Cassini probe circling Saturn, that the moon harbours life. The crew struggle over a six-year mission that makes it to Titan, where indeed, there is life, but unlike anything found on Earth.

Titan is the only moon in the Solar System that shares characteristics with Earth. It has a thick atmosphere, lakes, rivers and seas. These liquid bodies aren’t like those found on Earth because, instead of water, what flows on Titan is liquid methane. Methane falls as rain, snow and hail. Titan is rich in organic chemistry with continents made of ice. Beneath the surface lies a liquid ocean.

Its atmosphere is largely nitrogen-based, like Earth’s. It contains a chemical, acrylonitrile, that rains out and forms spherical structures called azotosomes. Acrylonitrile was recently discovered by the ALMA telescope in Chile’s high northern desert.

Recently, a study of Titan appeared in the International Journal of Astrobiology. It described the mechanism for the natural formation of membrane-enclosed vesicles that could contain the building blocks for life. These vesicles it called amphiphiles. They sound like the azotostomes ALMA. Each consists of two molecules, one hydrophobic (rejects water) and the other hydrophilic (attracts water). These vesicles resemble soap bubbles. The study notes that as they rain out of the atmosphere and coat the surfaces of Titan’s lakes and oceans. Amphiphiles can trap liquid water within their bubble membranes. Water, when interacting with organic compounds, can create the conditions to form the necessities for the emergence of early life.

These findings make NASA’s future Dragonfly mission to Titan all the more compelling. Dragonfly will parachute into Titan’s atmosphere and then fly like a helicopter to a landing site that its onboard instrumentation and software chooses. Dragonfly is equipped with cameras, lidar, and an array of navigational and landing-assist sensors. It plans to make numerous flights and multiple landings over a planned three-year mission. It will gather data and samples from the atmosphere and each landing site.

Dragonfly is a different type of rotorcraft than Ingenuity, the duocopter that accompanied Perseverance to Mars. It has eight rotors (called an octocopter) and is 3.85 metres square (12.5 x 12.5 feet), weighing 875 kilograms (1,900 pounds). That sounds heavy and bulky, but Titan’s weak gravity, 1/7th of Earth’s, and an atmosphere four times denser, should make flying easier on Titan than the thin atmosphere conditions that Ingenuity faced on Mars.

Dragonfly is nuclear-powered by a radioisotope thermoelectric generator (RTG). It has a lithium-ion battery pack. Each Titan day lasts about eight Earth days. The plan is to fly during the day and land, recharge and stay warm through each Titan night. With average surface temperatures at -180°C (-292°F), NASA has been using a Titan Chamber on Earth to simulate conditions Dragonfly will face, not just the cold but also the thicker atmosphere dynamics that will make the flying experience very different from here on Earth, or on Mars.

Dragonfly’s mission costs an estimated US$3.35 billion. It is scheduled for launch using a SpaceX rocket in 2028.

What do we hope to find?  If not life, what scientists hope for is the identification of preconditions for abiogenesis. Abiogenesis is the scientific theory behind the origin of life here on Earth. It is a natural process that turns natural chemical processes and non-living organic compounds into self-organizing and self-replicating living things. The exact mechanisms of life’s origins are hard to identify on Earth, 4.5 billion years after our planet formed.

On Titan, however, evidence of abiogenesis may be far easier to find. That’s because the Moon is chemically active with complex organic molecules, hydrogen cyanide, acetylene and many other hydrocarbons, all seen as key chemical building blocks for life.

The uniform cold temperatures and conditions on Titan’s lakes and ocean surfaces provide a degree of stability for life’s chemistry to organize into protected bubble membranes, which, in the absence of free oxygen in the atmosphere, are not subject to chemical degradation from the gas.