Titan鈥檚 plains may be covered in up to a metre of fluffy, organic 鈥渟now鈥�. About 65 per cent of the surface of Saturn鈥檚 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鈥檚 radar instrument bounced off Titan鈥檚 surface indicate that the surface isn鈥檛 as simple as those of most other rocky bodies in the solar system. 鈥淭he canonical models that we use to try to understand Titan鈥檚 surface, which were developed for the moon and are used for the moon, Earth, Venus 鈥� they don鈥檛 work directly on Titan,鈥� says Hayes. 鈥淭itan is a different beast in terms of the radar-scattering properties of the surface.鈥�

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鈥檚 hazy atmosphere, which researchers expect should float down to the surface like snow before getting compacted and solidified over time.

Titan鈥檚 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. 鈥淏ut this could give us a hint for how things work more broadly on Titan,鈥� says Hayes.

NASA鈥檚 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.

Free newsletter

Sign up to Launchpad

Sign up to newsletter

The history and future of space exploration: US

Embark on an extraordinary journey through the heart of the US鈥檚 space and astronomy landmarks, designed for curious minds and lifelong learners.

Read more

Our most detailed look yet at the strange lakes of Saturn鈥檚 moon Titan has revealed a diverse seascape, similar to Earth鈥檚 combination of freshwater rivers and salty oceans.

Unlike Earth鈥檚 water oceans, Titan鈥檚 lakes consist of methane and ethane, which are liquid at the planet鈥檚 average surface temperatures of about -179掳C (-290掳F).

Radar measurements from NASA鈥檚 Cassini spacecraft, which orbited Saturn between 2004 and 2017, have hinted at differences in the lakes鈥� properties, such as their composition and the waves on their surface. But there wasn鈥檛 enough information in the signals to distinguish between them.

Now, at Cornell University, New York, and his colleagues have mapped the composition and surface of Titan鈥檚 seas using a different radar technique, revealing an increasing amount of ethane as you travel down the planet from its north pole. 鈥淭he more north you go, the cleaner and purer the seas are; they鈥檙e more methane-dominated,鈥� says Poggiali.

Previous radar measurements were made using signals emitted and received at the same location, on the Cassini probe. This meant that the reflected radio waves were polarised, or twisted, in one direction.

The new study analysed signals from Cassini鈥檚 radar that had been reflected off the surface of the lakes and then received using radio antennae on Earth operated by NASA, called the Deep Space Network. The shallower angle of the reflected signal meant that it included two kinds of polarised waves, giving Poggiali and his colleagues more information about the lakes鈥� properties.

Free newsletter

Sign up to Launchpad

Sign up to newsletter

They found that many of the rivers and estuaries that fed the lakes had rough surfaces, probably caused by wind-whipped waves. This might be a sign of active tides or currents feeding into the lakes, says Poggiali. 鈥淎ctivity on the surface of the seas is super important if you want to plan a future mission, like a Titan submarine, but also to be able to better understand Titan鈥檚 environments in terms of wind and its atmospheric characteristics.鈥�

Poggiali and his colleagues also found that the rivers had a higher composition of methane before they fed the lakes. This could help us track the methane and ethane cycle on Titan, says at Imperial College London. 鈥淲hen a river enters a large, salty ocean on Earth, then you would see that, near where the river enters, you have a lower salinity of the water,鈥� he says. 鈥淚t鈥檚 kind of a similar thing happening here, only that it鈥檚 not about the content of salt, but the relative proportion of methane and ethane.鈥�

We are closer than ever to finally proving the multiverse exists

One hundred years ago, we discovered there were other galaxies beyond our own. Now, we might be on the verge of another discovery: that there are other universes

Craggy coastlines appear to have been carved out by waves around the methane seas and lakes of Saturn鈥檚 largest moon, Titan 鈥� 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. 女生小视频s think that winds in Titan鈥檚 thick nitrogen-rich atmosphere might produce rippling waves on these lakes, but these have never been directly observed because the moon鈥檚 atmosphere is too hazy to peer through.

Is an old NASA probe about to redraw the frontier of the solar system?

The New Horizons mission to Pluto, now zooming out of the Kuiper belt, has made a discovery that could upend what we know about where the solar system ends

Now, at the US Geological Survey in Florida and her colleagues have found that the shape of Titan鈥檚 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鈥檚 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鈥檚 oceans, in which coastal erosion came from waves or just from dissolving at the edges.

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

鈥淎lthough it鈥檚 tentative, I find it very exciting,鈥� says at Imperial College London. While we haven鈥檛 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 .

Free newsletter

Sign up to Launchpad

Sign up to newsletter

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鈥檚 planned Dragonfly drone mission due to launch in 2028.

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

The dunes on Saturn鈥檚 moon Titan may be made up of the remains of smaller moons that once smashed together and ground each other into sand.

Titan has sand dunes covering about 17 per cent of its surface, sweeping across its equatorial regions. Many researchers have suggested the sand may be made of organic particles that form in Titan鈥檚 thick atmosphere and then drift down to the ground. However, laboratory experiments have shown these types of particles tend to be very fragile, so they may not be able to stay intact while drifting across the moon鈥檚 surface to form dunes.

at the Southwest Research Institute in Colorado and his colleagues have come up with an alternate explanation that may be a better fit for the observations we have of Titan鈥檚 dunes: the sand particles may come from far beyond Titan鈥檚 atmosphere. He presented this work at the Lunar and Planetary Science Conference in Texas on 12 March.

Each of the giant planets in our solar system has a set of irregular satellites 鈥� relatively small moons that were once asteroids or comets before they were captured into orbit around a planet. These moons are made of particles that tend to be about the same size as Titan鈥檚 dune particles and are much stronger than the atmospheric organics.

Early in the solar system, these moons would have smashed together often, wearing each other down and releasing huge amounts of dust and grit. 鈥淚rregular satellites collisionally grind really effectively,鈥� said Bottke. But would this period of grinding produce enough ground-up remains to populate Titan鈥檚 dunes? According to the researchers鈥� simulations, Bottke said, 鈥淭itan gets on the order of about 10⁶ kilometres cubed of material, and that鈥檚 several times more than the dunes.鈥� Even more material could be added by direct impacts of meteorites and comets on Titan.

鈥淭his model might be crazy, but it is testable,鈥� said Bottke. If this is how Titan鈥檚 dune particles formed, bits of material might be left in the atmosphere, and those could have visibly different properties to organic particles that formed there.

Free newsletter

Sign up to Launchpad

Sign up to newsletter

鈥淚t might even be possible to test it with the data we have from the Cassini-Huygens mission,鈥� says at NASA鈥檚 Jet Propulsion Laboratory in California. And even if that data is inconclusive, NASA鈥檚 Dragonfly mission is slated to launch towards Titan in 2028. It is planned to fly through the dunes and measure the sand particles, which should solve this mystery once and for all.

The seas of Saturn鈥檚 moon Titan have weird 鈥渕agic islands鈥� 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鈥檚 thick atmosphere is full of complex organic molecules that can clump together and fall down to the moon鈥檚 surface like snow. at the University of Texas at San Antonio and her colleagues thought the 鈥渟now鈥� 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鈥檚 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.

鈥淲ater molecules just love themselves to the exclusion of some types of molecules,鈥� says at NASA鈥檚 Jet Propulsion Laboratory in California, who was not involved in this work. 鈥淏ut put methane on the same surface and it will crawl all over.鈥� 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鈥檛 happen with the magic islands, which appeared as ephemeral bright spots in observations from the Cassini spacecraft. 鈥淔or us to see the magic islands, they can鈥檛 just float for a second and then sink,鈥� Yu said in a . 鈥淭hey have to float for some time, but not for forever, either.鈥�

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 鈥渋cebergs鈥� broke off from the land, they could float on Titan鈥檚 seas for long enough to match the Cassini observations. This would work if, the researchers calculated, the sponge-like structures contained enough empty space 鈥� a minimum of about 25 to 50 per cent depending on the exact composition of the ice.

Free newsletter

Sign up to Launchpad

Sign up to newsletter

This doesn鈥檛 mean that the mysterious islands are definitely porous icebergs, though. 鈥淲e are narrowing the different scenarios for the magic islands, but we still don鈥檛 yet know the answer,鈥� 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鈥檚 transitory islands could actually be floating matter from this strange world鈥檚 atmosphere.