Titan is the only moon in the solar system with a thick atmosphere, and the only world besides Earth known to have lakes and seas on its surface. However, with a frigid surface temperature of around -290° F (94 K), the rain falling on Titan isn’t water. It’s liquid methane and ethane, compounds that are gases at room temperature on Earth.

Most of Saturn’s moons display their ancient faces pockmarked by thousands of craters. Titan, Saturn’s largest moon, looks younger than it really is because its craters are being eroded. Radar observations by the Cassini spacecraft show that dunes of hydrocarbon sand are filling in the craters.

This image taken with the Cassini radar shows two craters on Titan. On the left is crater Sinlap which is a relatively ‘fresh’ crater, with a depth-to-diameter ratio similar to is found on other large moons in the solar system such as Ganymede. One the right is Soi, an extremely eroded crater with a very small depth compared to similar craters on Ganymede. These craters are both about 80 km (almost 50 miles) in diameter.

Image Credit: NASA