Titan’s plains may 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, 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. 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 arrive 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.

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Craggy coastlines appear to have been carved out by waves around the methane seas and lakes of Saturn’s largest moon, Titan – and a NASA mission launching in 2028 could give us a closer look.

Titan is the only body in the solar system apart from Earth that has liquid on its surface, in the form of lakes and oceans made up of hydrocarbons like liquid methane, ethane and other organic molecules. Scientists think that winds in Titan’s thick nitrogen-rich atmosphere might produce rippling waves on these lakes, but these have never been directly observed because the moon’s atmosphere is too hazy to peer through.

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Now, at the US Geological Survey in Florida and her colleagues have found that the shape of Titan’s coastlines are best explained by the existence of waves on the ocean surface that have eroded them over time.

Palermo and her team looked at the coasts around Titan’s largest seas and lakes, like the Kraken Mare and Ligeia Mare, and compared them with coastlines on Earth whose origin we understand, such as Lake Rotoehu in New Zealand, which was initially made through flooding and later eroded from waves. They then created different simulations of Titan’s oceans, in which coastal erosion came from waves or just from dissolving at the edges.

They found that the images of Titan’s coastline were best represented by the simulation with waves, and bore a resemblance to wave-eroded coastlines on Earth.

“Although it’s tentative, I find it very exciting,” says at Imperial College London. While we haven’t seen the waves themselves, this is very strong evidence that they exist, he says, and adds to a large body of indirect evidence, such as the presence of .

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The only way to truly verify that waves are there would be to send a spacecraft to the surface, says Mueller-Wodarg, such as NASA’s planned Dragonfly drone mission due to launch in 2028.

Studying Titan’s coastline might also help us investigate how the first coasts on Earth formed, says Palermo. “Titan is a unique laboratory for coastal processes because it is untouched by people and plants. It’s really a place where we can investigate the coast as a physical process alone.”

The seas of Saturn’s moon Titan have weird “magic islands” that seem to appear and disappear over the course of hours to weeks. These so-called islands might actually be porous, sponge-like clumps of snow that slowly fill up with fluid and then sink.

Titan’s thick atmosphere is full of complex organic molecules that can clump together and fall down to the moon’s surface like snow. at the University of Texas at San Antonio and her colleagues thought the “snow” could be responsible for the magic islands. To test their idea, they used what we know about these atmospheric compounds and how they are expected to interact with Titan’s seas.

Typically, we expect any solids on the surfaces of these seas to sink immediately because the liquid on Titan is methane rather than water. While water molecules tend to cling to one another and push away other materials, methane easily grabs on to other molecules, so a pool of liquid methane has very little surface tension.

“Water molecules just love themselves to the exclusion of some types of molecules,” says at NASA’s Jet Propulsion Laboratory in California, who was not involved in this work. “But put methane on the same surface and it will crawl all over.” That means that the methane oceans and lakes on Titan should immediately swallow up any solids, even those that might otherwise be expected to float.

But that clearly doesn’t happen with the magic islands, which appeared as ephemeral bright spots in observations from the Cassini spacecraft. “For us to see the magic islands, they can’t just float for a second and then sink,” Yu said in a . “They have to float for some time, but not for forever, either.”

The researchers found a solution to this problem: if large chunks of snow amassed on the shore, they could form ices that are full of holes, like sponges. When these porous “icebergs” broke off from the land, they could float on Titan’s seas for long enough to match the Cassini observations. This would work if, the researchers calculated, the sponge-like structures contained enough empty space – a minimum of about 25 to 50 per cent depending on the exact composition of the ice.

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This doesn’t mean that the mysterious islands are definitely porous icebergs, though. “We are narrowing the different scenarios for the magic islands, but we still don’t yet know the answer,” says Malaska. Other possible explanations include bubbles of nitrogen gas, waves caused by wind or solid sediments in the oceans. But this does provide evidence that Titan’s transitory islands could actually be floating matter from this strange world’s atmosphere.