Ice Volcanoes of Titan May Harbor Life

Titan, the sixth and largest moon of the planet Saturn, is thought to be made largely of ice. Some of that ice may melt during meteor impacts or in underground processes, producing "ice volcanoes" that emit a "lava" containing ammonia mixed with water.

New observations of Titan by the Cassini spacecraft suggest the presence of cryovolcanism on the moon's surface. Cryovolcanism has important astrobiological implications, as it provides a means of exposing Titan's organics to liquid water, transforming hydrocarbons and nitriles into more evolved and oxidized prebiotic species.

Ganesa Macula, a mountain on Titan, is believed to be an '"ice volcano" that periodically belches "lava" containing liquid water. Simulated lab research by University of Arizona graduate student Catherine Neish suggests this water may react with organic compounds in Titan's atmosphere to create complex molecules similar to those on the early Earth.

To assess the potential of Ganesa Macula for prebiotic chemistry, its height is estimated using radarclinometry and other methods, to calculate the freezing timescale assuming an initially completely liquid dome. Given height constraints of ~200 m to 4 km, liquid water or water-ammonia environments could be sustained in Ganesa Macula for timescales of the order of 102-105 years. These timescales open a window for prebiotic chemistry far wider than can be explored in terrestrial laboratory experiments.

For almost thirty years, scientists have known that complex carbon compounds called tholins exist on comets and in the atmospheres of the outer planets. Theoretically, tholins might interact with water in a process called hydrolysis to produce complex molecules similar to those found on the early Earth.

Could tholins formed in Titan's atmosphere react with liquid water temporarily exposed by meteor impacts or ice volcanoes to produce potentially prebiotic complex organic molecules — before the water freezes?

Laboratory research by Catherine Neish, a graduate student working on her doctorate in planetary science at the University of Arizona, suggests, not without controversy, however, that, over a period of days, compounds similar to tholins can be react with water at near-freezing temperatures.

Liquid water exposed on Titan is believed to persist for hundreds to thousands of years — plenty of time for such reactions to take place, similar to processes may have occurred on the early Earth.

Posted by Casey Kazan.