Solar Exploration

Titan is Saturn's largest moon and the second-largest moon in the solar system, bigger than the planet Mercury. It's the only moon known to have a dense atmosphere, so thick that surface pressure is about 1.5 times that of Earth — thick enough that a person could theoretically glide with strapped-on wings in Titan's low gravity and dense air, if they could survive the cold.

Even more remarkably, Titan is the only place in the solar system besides Earth known to have stable liquid on its surface — but instead of water, Titan's lakes, rivers and seas are made of liquid methane and ethane, kept liquid by temperatures around -179°C. This gives Titan an entire weather cycle, complete with hydrocarbon rain, rivers carving channels, and seasonal cloud formation, all running on chemistry entirely different from Earth's water cycle.

Beneath its hazy orange nitrogen atmosphere, Titan's surface is surprisingly Earth-like in shape if not in substance: dune fields of hydrocarbon-coated ice grains, river deltas, and the largest liquid sea, Kraken Mare, that's bigger than the Caspian Sea. Scientists also suspect Titan hides a subsurface liquid-water ocean beneath its icy crust, making it, alongside Europa and Enceladus, one of the leading candidates in the search for life beyond Earth.