Move Over, Mars: The Search for Life on Saturn’s Largest Moon Alien microbes could be flourishing in the underground seas of Titan and the solar system’s other ocean worlds. But scientists believe this enigmatic world might harbor alien life. Larger than our moon and even Mercury, which is roughly two-fifths the size of Earth, Titan hosts plenty of intriguingly unique environments. But it is possible that on some of the ocean worlds, alien microbes could instead glean energy from hydrothermal—hot water—vents found near volcanoes rising from the bottom of these vast oceans. On the ocean worlds, the necessary force is provided by the constant gravitational pull of close orbits around the colossi of Saturn and Jupiter.