Study shows Saturn’s moon Titan could host early cell structures

As humanity’s search for extraterrestrial life signs continues, scientists are getting increasingly more evidence that Saturn’s moon Titan might be suitable for supporting life – primitive at least – in the form of early cell structures or the building blocks of life.

Specifically, NASA research has suggested that cell-like compartments called vesicles could form naturally in the lakes of Titan, the only world other than Earth so far discovered to have liquid on its surface, according to the Phys report published on July 14.

Now, Titan’s ponds and seas don’t contain water but liquid hydrocarbons like ethane and methane. However, new research by NASA, published in the International Journal of Astrobiology, has described a possible process that might form stable vesicles on Titan, based on existing data about its atmosphere and chemistry.

As it happens, these compartments represent an important link in creating the precursors of living cells (or primitive protocells). The process also involves molecules called amphiphiles, which can self-organize into vesicles under suitable conditions – even the freezing ones on Titan.

On Earth, these polar molecules consist of two parts – a hydrophobic and a hydrophilic end. In water, groups of these molecules can bunch together into ball-like spheres like soap bubbles, where the hydrophilic part faces outward to interact with the water and ‘protect’ the hydrophobic part inside.

If the conditions are right, they can lead to the formation of two layers, creating a cell-like ball with a bilayer membrane that encapsulates a pocket of water on the inside of the sphere. That said, things on Titan are a lot different than from the early Earth.

Saturn’s moon and its life-supporting qualities

On Titan, most of the atmosphere is nitrogen, but there’s a lot of methane (CH4) as well, forming clouds and rain that causes erosion and river channels on the surface, filling up the lakes and seas, and then evaporating in the sunlight to form clouds once again.

Thanks to this atmospheric activity, complex chemistry can happen too, such as energy from the sun breaking apart molecules like methane, the pieces of which then reform into complex organic molecules, and many astrobiologists think this could tell us how the molecules required for the origin of life formed and evolved on the early Earth.

As for Titan, the new study took into account how vesicles might form in the extremely cold conditions of Titan’s hydrocarbon ponds and seas by focusing on sea-stray droplets that move upwards by splashing raindrops. These spray droplets and the sea surface could both be coated in layers of amphiphiles. 

Then, if a droplet lands on the surface of a lake, the two layers of these amphiphiles meet to form a double-layered vesicle, enclosing the original droplet. In time, many of these vesicles would spread throughout the lake and interact and compete in an evolutionary process, resulting in protocells.

As a reminder, scientists have earlier hypothesized that Titan’s rich organic composition could be suitable for life but that the life forms potentially existing there would be minuscule.