by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
The disappearing “magical islands” on Saturn’s largest moon Titan have fascinated scientists since NASA’s Cassini mission spotted them during flybys a decade ago. Now, researchers believe they have uncovered the secrets of the phenomenon.
The ephemeral features were originally thought to be made of fizzing gas bubbles, but astronomers now believe they may be a honeycomb-like glacier made of organic material that falls onto the moon’s surface.
Scientists consider Titan to be one of the most interesting moons in our solar system because it has certain similarities to Earth. In many ways, however, it presents a baffling alien landscape.
Titan, which is larger than both our moon and the planet Mercury, is the only moon in our solar system with a thick atmosphere. The atmosphere is composed mostly of nitrogen with a little methane, which gives Titan its fuzzy orange appearance. Atmospheric pressure on Titan is about 60% greater than Earth’s, so it creates the kind of pressure people feel swimming about 50 feet (15 meters) below the ocean’s surface, according to NASA.
Titan is the only other world in our solar system with Earth-like liquid bodies on its surface – but the rivers, lakes and seas are made up of liquid ethane and methane, which form clouds and emit liquid gases rain down from the sky. .
The Cassini mission orbiter, which carried the Huygens probe that landed on Titan in 2005, made more than 100 flybys of Titan between 2004 and 2017 to reveal much of what scientists know about the moon today.
Among the most fascinating features of Titan are its magical islands, which scientists see as moving bright spots on Titan’s ocean surfaces that last for a few hours, several weeks or longer. Cassini radar images captured the unexplained bright regions in Ligeia Mare, the second largest liquid body on Titan’s surface. The sea is 50% larger than Lake Superior and is composed of liquid methane, ethane and nitrogen.
Astronomers thought that these regions could be clusters of bubbles of nitrogen gas, actual islands made of floating solids or features attributed to waves (although the waves only reach a few millimeters in height).
Planetary scientist Xinting Yu, an assistant professor at the University of Texas at San Antonio, focused on analyzing the connections between Titan’s atmosphere, liquid bodies and solid materials that fall like snow to see if they could be related to the magical islands. .
“I wanted to investigate whether the magical islands could be organisms floating on the surface, like phoenixes that can float on water here on Earth before finally disappearing,” said Yu, lead author of a study published 4 January in the journal Geophysical Research Letters.
The scientists aim to understand as much as they can about Titan before sending a dedicated mission to the moon. The Dragonfly mission, led by the Johns Hopkins Applied Physics Laboratory in partnership with NASA, is expected to launch in 2028 and reach Titan in the 2030s.
Analyze an unusual world
Titan’s upper atmosphere contains a diverse range of organic molecules, including nitriles, hydrocarbons and benzene. The surface temperature is so cold at minus 290 degrees Fahrenheit (minus 179 degrees Celsius) that the rivers and lakes were carved with liquid methane – the way rocks and lava helped form features and channels on Earth.
The organic molecules in Titan’s atmosphere bind together in clumps before freezing and falling to the moon’s surface. Dark plains and dunes of organic matter can be seen across Titan, and scientists think the features were mostly created by Titan’s “snows”.
But what happens when the hydrocarbon snow falls on the smooth surfaces of Titan’s liquid gas lakes and rivers? Yu and her colleagues investigated the different scenarios that could occur.
Yu’s team determined that solid organic material falling from the upper atmosphere would not dissolve when it landed on Titan’s liquid bodies because they are already saturated with organic particles.
“For us to see the magic islands, they cannot float for a second and then sink,” Yu said. “They have to swim for a while, but not forever, either.”
But liquid ethane and methane have a low surface tension, which means it’s harder for solids to float on top.
Yu’s team simulated various models and determined that the frozen solid material would not float unless it was porous, like honeycomb or Swiss cheese. The small particles probably wouldn’t float on their own unless they were big enough.
The team’s analysis led to a scenario where the frozen hydrocarbon solids come together near the shore, then break off and float across the surface like glaciers on Earth. Liquid methane slowly seeps into the frozen lumps, causing them to disappear from view.
In addition, a thin layer of frozen solids on Titan’s seas and lakes could explain why the moon’s liquid bodies are so smooth, according to the researchers.
Get close to Titan
Over the next decade, Dragonfly is expected to investigate mostly the plains of organic matter in Titan’s equatorial region, rather than its liquid bodies.
The rotorcraft lander will sample materials on Titan’s surface, study the potential habitability of its unique environments and determine which chemical processes are taking place on the moon.
Organic chemicals essential to life on Earth are also found on Titan, such as nitrogen, oxygen and other carbon-based molecules. Under the thick crust of Titan, made of ice, there is an internal ocean of salty water unlike other moons of the world orbiting oceans orbiting Saturn such as Enceladus, or Jupiter’s moon Europa — which are considered to be the best places to search for the life beyond Earth.
Titan sounds unwelcoming, but it’s possible that conditions that could support life depend on different chemistry and forms in ways beyond our current understanding, according to NASA.
For more CNN news and newsletters create an account at CNN.com
