Titan is the biggest moon of Saturn. It is even bigger than the planet Mercury. Titan has thick air, and it has lakes and seas.

But they are not water! It is about minus 180 degrees Celsius there, so methane, a gas on Earth, becomes a liquid. Methane rain falls from the sky. As of writing, NASA plans for a flying robot called Dragonfly to arrive at Titan in 2034.

Saturn's largest moon, Titan, is bigger than the planet Mercury and has a thick atmosphere made mostly of nitrogen. Its surface temperature is about minus 180 degrees Celsius, so cold that water ice is as hard as rock. At this temperature, methane and ethane, which are gases on Earth, become liquids. They fall as rain, run in rivers and collect in lakes and seas.

In fact, Titan is the only world besides Earth known to have liquids on its surface. Because a thick orange haze hides the ground, scientists used radar on the Cassini spacecraft to find dark lakes near the north pole. As of writing, NASA plans to send a drone-like rotorcraft called Dragonfly, expected to arrive in 2034.

Saturn's moon Titan, about 5,150 kilometers across and larger than the planet Mercury, is unusual among moons in having a thick atmosphere, with a surface pressure about 1.5 times Earth's. At roughly minus 180 degrees Celsius, water ice is as hard as rock, while methane and ethane exist as liquids that fall as rain and gather in lakes and seas.

According to NASA, Titan is the only world besides Earth known to have liquid on its surface. An orange haze hides the ground, so the Cassini spacecraft relied on radar. In 2007, researchers identified numerous radar-dark areas near the north pole as hydrocarbon lakes, and later observations revealed vast seas. In 2014, radar echoes from the seabed showed that Ligeia Mare is up to about 160 meters deep.

For radar to pass through that much liquid, it has to be extremely clear. That same year, researchers reported a bright feature that appeared in the sea and then vanished. Nicknamed the "magic island," it may have been waves, bubbles or floating solids, though no one has pinned down which. As of writing, NASA's Dragonfly rotorcraft is scheduled to launch no earlier than July 2028 and arrive in 2034 to study prebiotic chemistry.