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Our solar system is unique among the possible 100 billion planetary systems: it is the only system confirmed to have life. It also may be the only system to have two celestial bodies with life on them – Earth and Titan. Titan boasts an array of unique features suitable for life: an atmosphere, liquid lakes, and a possible subterranean ocean of water. It is because of these features that NASA should return to Titan in the hopes of discovering life.

Titan’s geological and astrobiological features make it a prime hotspot for alien life in our solar system compared to Enceladus and Europa. Titan contains an ocean of water which may host familiar life-forms. Also, whenever sunlight hits its atmosphere, the nitrogen and methane break down into organic molecules which contain hydrogen and carbon, the building blocks of life. Titan’s inorganic compounds also play a role in its potential habitability. In the Miller-Urey experiment, electrical charges would generate amino acids in an atmosphere containing hydrogen, water vapor, ammonia, and methane. This experiment, which models Earth in its earliest form, also resembles Titan’s environment. Therefore, Titan can be used to analyze the origins of life on Earth.

If Titan does contain life, it would expand our understanding of life on Earth as well as on other astronomical bodies. Most of our understanding of life is restricted to just terrestrial organisms. This preconceived notion of life leads us to use Earth’s parameters as the criterion for determining an exoplanet’s habitability. Because of this, we are looking for planets that resemble Earth, but we have not considered the possibility of other non-Earth-like planets hosting life. For example, we are looking for exoplanets within their stars’ Goldilocks zone. But discovery of life on Titan would require us to alter our understanding of life as Titan is not even remotely close the Goldilocks zone. Titan may help us determine if we are being too selective in our quest for alien life.

Also, Titan’s life forms would most likely not resemble our planet’s organisms. They might have different metabolic functions and biochemistry. For example, cells on Earth have lipid bilayers, an organelle that determines what enters the cells. But this organelle is useless in Titan’s methane lakes. So in their research paper, “Membrane alternatives in worlds without oxygen: Creation of an azotosome”, Stevenson and al. proposed the azotosome, a theoretical membrane composed of organic nitrogen compounds which can sustain the frigid temperatures of Titan. This hypothetical membrane demonstrates the same flexibility of Earth’s cellular membrane. The azotosome suggests that alien life would offer a sharp contrast to what we expect from life on other worlds.

Titan can be seen as a stepping stone that will help expand the field of astrobiology. It will also augment our knowledge of Earth-based life (e.g. the origins of life) while also advancing our search for alien life. Since Titan has the highest potential for life and research opportunities, NASA should make a return to this moon its top priority.