Research shows path toward protocells on Saturn’s moon Titan

NASA search has shown that cell type compartments called vesicles could naturally form in the lakes of the Titan of the Lune of Saturn.

Titan is the only world apart from the earth which is known to have liquid on its surface. However, Titan lakes and seas are not filled with water. Instead, they contain liquid hydrocarbons such as ethane and methane.

On earth, liquid water would have been essential at the origin of life as we know it. Many astrobiologists have wondered if Titan liquids could also provide an environment for the formation of the molecules required for life – either as we know it, or perhaps as we do not know – to get the hand.

New NASA research, published in the International Astrobiology Journaldescribes a process by which stable vesicles could form on Titan, on the basis of our current knowledge of the atmosphere and chemistry of the moon. The formation of such compartments is an important step in the manufacture of precursors of living cells (or protocels).

The process implies molecules called amphiphiles, which can self-organization in vesicles under the right conditions. On earth, these polar molecules have two parts, a hydrophobic end (fearing water) and a hydrophilic end (which love water). When they are in water, the groups of these molecules can regroup and form spheres in the shape of a ball, such as soap bubbles, where the hydrophilic part of the molecule is turned outwards to interact with water, “protecting” the hydrophobic part inside the sphere. Under the right conditions, two layers can form, creating a cell type ball with a two -failed membrane which sums up a pocket of water inside.

However, when we consider the formation of vesicles on Titan, the researchers had to take into account an environment very different from the beginning of the earth.

Titan is Saturn’s largest moon and the second largest in our solar system. Titan is also the only moon in our solar system with a substantial atmosphere.

The foggy golden atmosphere of the Titan kept the moon surrounded by mystery for a large part of human history. However, when the NASA Cassini spacecraft arrived in Saturn in 2004, our Titan views changed forever.

Thanks to Cassini, we now know that Titan has a complex weather cycle that actively influences the surface today. Most of the Titan’s atmosphere is nitrogen, but there is also a significant amount of methane (CH₄). This methane forms clouds and rain, which rises to the surface to cause erosion and river canals, filling lakes and seas. This liquid then evaporates into sunlight to form clouds again.

This atmospheric activity also allows complex chemistry. The energy of the sun separates molecules like methane, then the parts then reform in complex organic molecules. Many astrobiologists believe that this chemistry could teach us how the molecules necessary at the origin of life have formed and have evolved at the beginning of the earth.

The new study examined how vesicles could form in the freezing conditions of lakes and titan hydrocarbon seas, focusing on sea spray droplets, thrown upside down, splashing the rain drops. On Titan, the two spray droppings and the surface of the sea could be coated with layers of amphiphiliac. If a droplet then landed on the surface of a pond, the two layers of amphiphiles meet to form a double layer (or bicouche) vesicle, surrounding the original droplet. Over time, many of these vesicles would be dispersed throughout the pond and would interact and compete in an evolutionary process which could lead to primitive protocels.

If the proposed path occurs, this would increase our understanding of the conditions in which life could form.

“The existence of all the vesicles on Titan would demonstrate an increase in order and complexity, which are the necessary conditions at the origin of life,” said Conor Nixon of Goddard Space Flight Center from NASA in Greenbelt, Maryland. “We are delighted with these new ideas because they can open new directions in Titan research and change the way we are looking for life on Titan in the future.”

NASA’s first mission to Titan is the next Rotorcraft of Libellule, which will explore the surface of the Saturnian moon. Although Titan lakes and seas are not a destination for the dragonfly (and the mission will not carry the light dissemination instrument required to detect such vesicles), the mission will fly from one location to another to study the surface composition of the moon, carry out atmospheric and geophysical measurements and characterize the habit of the Titan environment.