Large craters on Saturn's largest moon, Titan, are the prime locations to search for the building blocks of life, according to a study.
Using imagery and data from the Cassini spacecraft and Huygens probe, scientists led by Catherine Neish from the University of Western Ontario in Canada, zeroed on the best places to look for biological molecules on the surface of Titan.
The surface of Titan has abundant carbon-rich molecules (hydrocarbons) that have been shown to form amino acids, the building blocks of proteins needed for life, when exposed to liquid water in laboratory simulations.
However, Titan is much too cold for liquid water to be present on the surface.
Radar measurements from Cassini, which orbited Saturn for 13 years, were able to peer through Titan's optically thick atmosphere, revealing the terrain of this enigmatic world.
Cassini's radar instrument unveiled lakes, dunes, mountains, river valleys, and not many craters, indicating that there are processes happening that resurface Titan and either fill in or erode older craters.
Discovering a similar world to Earth over nine times its distance from the Sun was monumental, researchers said.
Although the methane lakes may have seemed like the obvious choice to look for signs of life, researchers instead found craters and cryovolcanoes (regions where liquid water erupts from beneath Titan's icy surface) to be the two most enticing locations.
Both features hold promise for melting Titan's icy crust into liquid water, a necessary step to form complex biomolecules.
"When we mix tholins (organics produced when simple gas mixtures are subject to cosmic radiation) with liquid water we make amino acids really fast," said Morgan Cable from NASA's Jet Propulsion Laboratory in the US.
"So any place where there is liquid water on Titan's surface or near its surface could be generating the precursors to life - biomolecules - that would be important for life as we know it, and that's really exciting," Cable said.