Titan

Life on Titan

Scientists believe that the atmosphere of early Earth was similar in composition to the current atmosphere on Titan. Many hypotheses have developed that attempt to bridge the step from chemical to biological evolution. The Miller-Urey experiment and several following experiments have shown that with an atmosphere similar to that of Titan and the addition of UV radiation, complex molecules and polymer substances like tholins can be generated. The reaction starts with dissociation of nitrogen and methane forming hydrocyan and ethyne. Further reactions have been studied extensively.

All of these experiments have led to the suggestion that enough organic material exists on Titan to start a chemical evolution analogous to what is thought to have started life on Earth. While the analogy assumes the presence of liquid water for longer periods than is currently observable, several theories suggest that liquid water from an impact could be preserved under a frozen isolation layer.[56] It has also been suggested that liquid ammonia oceans could exist deep below the surface.[57] Furthermore, Titan's distance from the Sun and the anti-greenhouse effect of its cloud cover, as well as the absence of CO2, would further limit the option for a fully analogous environment. With these many obstacles, the topic of life on Titan may best be described as a thought experiment for examining theories for life's origin on Earth.[58] In other words, if life were able to develop on Titan, it would provide a mirror for examining the evolution of life on Earth. This line of reasoning has been challenged, however, by an alternate explanation for life's hypothetical existence on Titan. It has been proposed that, if life were to be found on Titan, that it would be statistically more likely to have originated from Earth than to have appeared independently. Research conducted by Brett Gladman of the University of British Columbia theorizes that large asteroid and cometary impacts on Earth's surface have caused hundreds of millions of fragments of microbe-laden rock to escape Earth's gravity. Further calculations indicate that a number of these would encounter many of the bodies in the solar system, including Titan.[59][60]

While the Cassini-Huygens mission was not equipped to provide evidence for biology or complex organics, it did support the existence of an environment on Titan that is similar, in some ways, to that of the primordial Earth. However, at this time future missions and experiments are not currently being planned to research the question. Considering the time required for executing such a voyage, further scientific data would be decades away