Structures similar to the first Earth cells may form independently on Saturn’s moon Titan. This is stated in a new NASA study published in the International Journal of Astrobiology.
Titan is Saturn’s largest moon and the second largest in the Solar System. It is covered by a thick, hazy atmosphere containing large amounts of methane. Its surface also features lakes, seas, and rain made of liquid methane and ethane. It is the only known place in the Solar System, apart from Earth, where there is stable liquid on the surface.
Thanks to these features, as well as data obtained from NASA’s Cassini mission, scientists have determined that Titan has an active hydrological cycle similar to Earth’s, except that methane is involved instead of water. In particular, tiny “bubbles” of molecules similar to those that make up cell walls can form there. When a raindrop falls into a sea of hydrocarbons, two layers of such molecules can form on its surface. A closed bubble-like structure, called a vesicle, is formed.
On Earth, such structures are considered one of the first steps toward the emergence of life. According to scientists, if they can form on Titan, it means that even in completely different conditions (without water!), life can emerge (although perhaps not at all like life on Earth).
“If vesicles really exist on Titan, it means that the conditions for life to arise are present there. This opens up new avenues of research and could change our approach to the search for life in space,” says Conor Nixon of NASA’s Goddard Space Flight Center.
This also suggests that Titan may have a non-biological environment where structures capable of storing, protecting, and possibly transmitting information could still develop. These properties bring them closer to protocells — primitive structures that may have been the first step toward the emergence of life. Although these structures on Titan may have different chemistry and not be alive in the usual sense, they potentially perform functions that once led to the formation of the first cells on early Earth.
“The presence of any vesicles on Titan would demonstrate an increase in order and complexity, which are necessary conditions for the emergence of life,” adds Conor Nixon.
NASA is already preparing to explore Titan more closely. The Dragonfly mission is scheduled to launch in 2028. It will be an autonomous rotary-wing drone capable of flying from point to point, studying the surface and chemical composition of the moon’s atmosphere and searching for signs of habitability. Although Dragonfly will not land in the lakes, it will collect samples from dunes, craters, and plains where organic molecules may have accumulated. This will be the first study of its kind in a hydrocarbon environment.
This study overturns scientists’ ideas about where life is possible. If protocells can arise even in liquid methane at extremely low temperatures, then the possibility of life existing in our galaxy now seems much more realistic than previously thought.
