Most moons look ancient because their faces are pockmarked by thousands of craters but Titan, Saturn's largest moon, gets constant retouching because its craters are getting erased. Dunes of exotic, hydrocarbon sand are slowly but steadily filling in its craters, according to new research.
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 minus 290 degrees Fahrenheit (94 kelvins), the rain that falls from Titan's skies is not water but instead liquid methane and ethane, compounds that are normally gases on Earth.