Probe on Titan. Artwork of a submarine probe exploring a hydrothermal vent in a hypothetical ocean on the surface of Titan, Saturn's largest moon. Titan is thought to be too cold for liquid water, but could harbour seas of ethane or similar hydrocarbons. Hydrothermal vents (or black smokers) are found on Earth along mid-ocean ridges. They release superheated water into the cold deep ocean, and form the habitat for many specialised forms of life. Similar structures on other worlds could also harbour life.