https://www.vice.com/en_us/article/wxdzpb/how-scientists-will-look-for-alien-life-on-ocean-moons

Life on Earth likely emerged in our planet’s oceans, which is why scientists hoping to find extraterrestrial life elsewhere are particularly interested in ocean worlds. Fortunately, there are multiple moons right here in our own solar system that fit that description, some of which host watery depths and, in one case, strange seas made of hydrocarbons. 

Jonathan Lunine, who serves as David C. Duncan Professor in the Physical Sciences and Chair of the department of astronomy at Cornell University, has spent his career studying these fascinating ocean moons and their potential to host life. He was one of the first people to see images from Saturn’s moon Titan after the successful landing of the Huygens Probe in 2005, which revealed an otherworldly surface covered in liquid methane.