Saturn’s largest moon, Titan, is unlike any other in the solar system. It’s the only moon with a dense atmosphere. It’s also the only known place in the solar system besides Earth with liquid bodies currently on its surface. But instead of containing water, Titan’s lakes, seas, and rivers are made up of liquid methane and ethane. While life as we know it on Earth could never survive in these chemicals, alien organisms may have found a way. “The universe is much more creative and much better at solving problems than people are, so we shouldn’t rule it out,” says Sarah Hörst, a planetary scientist at Johns Hopkins University in Maryland.
Beneath the liquid on Titan’s surface is a shell of ice 200 to 300 kilometers (125 to 186 miles) thick. Underneath it lies an ocean of liquid water. Liquid water is a necessary ingredient for life on Earth—so could Titan’s hidden ocean be another likely place to find alien organisms? Probably not, says Hörst. That’s because sunlight can’t penetrate Titan’s icy outer layer to provide the light and heat energy needed to sustain life in the ocean below.
There is one other place on this moon where life might have existed long ago. In the past, huge asteroids and comets crashed into the moon’s surface. Such collisions caused enormous explosions. Heat from these blasts melted portions of Titan’s icy surface. That created pools of mineral-rich liquid water—a potential spot where microbes could have thrived, says Hörst.