TITAN’S plains could be covered in up to a metre of fluffy, organic “snow”. About 65 per cent of the surface of Saturn’s huge moon is made up of strangely uniform and flat plains, and they seem to be coated in a porous, dry layer of particles that have fallen from the sky.
The surface of Titan is difficult to study from afar because it is obscured by a thick, hazy atmosphere. The Cassini spacecraft, which orbited Saturn from 2004 to 2017, managed to take a closer look using radar. Now, Alexander Hayes at Cornell University in New York state and his colleagues have analysed the radar data in more detail than ever before.
The way the radio waves from Cassini’s radar instrument bounced off Titan’s surface indicate that the surface isn’t as simple as those of most other rocky bodies in the solar system. “The canonical models that we use to try to understand Titan’s surface, which were developed for the moon and are used for the moon, Earth, Venus – they don’t work directly on Titan,” says Hayes. “Titan is a different beast in terms of the radar-scattering properties of the surface.”
Instead of a simple rocky surface, the radar data was a better fit to a two-layer model, with a blanket of soft, low-density material covering a harder terrain (Journal of Geophysical Research: Planets, ). The blanket layer, ranging from centimetres to a metre in thickness, is probably made up of organic molecules from Titan’s hazy atmosphere, which researchers expect should float down to the surface like snow before getting compacted and solidified over time.
Titan’s surface also experiences rain, wind and erosion, so it is important to understand how the blanket layer has built up slowly over time, shaped by these processes. “But this could give us a hint for how things work more broadly on Titan,” says Hayes.
NASA’s Dragonfly mission, which is expected to launch in 2028 and land on Titan in 2034, should be able to measure these layers and help us figure out exactly how they formed.
It is crucial not only for our understanding of Titan itself, but also for the design of any future spacecraft that will follow Dragonfly to visit this strange moon and attempt landing there.
