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Saturn’s Moon Titan Has Disappearing ‘Magic Islands’ That May Be Accumulation of Organic Materials

(CNN) — They have piqued the interest of scientists since NASA’s Cassini mission discovered them a decade ago on the missing “magic islands” on Saturn’s largest moon, Titan. Now, researchers believe they have unlocked the secret to this phenomenon.

Although initially thought to be effervescent bubbles of gas, astronomers now believe they may be honeycomb glaciers formed from organic material that fell to the moon’s surface.

Scientists consider Titan to be one of the most fascinating moons in the solar system because it has some similarities to Earth. In many ways, however, it also presents a disturbingly alien landscape.

Titan is larger than our moon and Mercury and is the only moon in the solar system with a dense atmosphere. The atmosphere is composed mostly of nitrogen with a small amount of methane, which gives Titan its fuzzy orange appearance. According to NASA, Titan’s atmospheric pressure is about 60 percent greater than Earth’s, so it exerts a pressure equivalent to what a human would feel swimming about 50 feet (15 meters) below the surface of the ocean.

Titan is also the only world in our solar system with a surface similar to Earth’s liquid bodies, but the rivers, lakes and oceans are made of liquid ethane and methane, which form clouds and cause liquid gas to rain down from Titan. Honey.

The Cassini mission orbiter carried the Huygens probe to Titan in 2005 and conducted more than 100 flybys of Titan between 2004 and 2017, revealing what scientists know about Titan today.

One of the most puzzling aspects of Titan is its magical islands, where scientists have observed moving bright spots on Titan’s seas that can last for hours, weeks or longer. Cassini radar images captured unexplained bright areas in the Ligeia Sea, the second largest liquid body on Titan’s surface. This ocean is 50% larger than Lake Superior and is composed of liquid methane, ethane and nitrogen.

Astronomers believe these regions could be concentrated nitrogen bubbles, actual islands composed of floating solids, or features attributed to waves (although the waves only reach a height of a few millimeters).

Artist’s illustration shows a lake at the north pole of Saturn’s moon Titan, including the bulge rim observed by Cassini.

Xinting Yu, an assistant professor and planetary scientist at the University of Texas at San Antonio, focused on analyzing the connections between Titan’s atmosphere, liquid bodies, and solid matter that falls in the form of snow to see if they are related to the magical island.

“I wanted to investigate whether the magic islands could actually be organic matter floating on the surface, like pumice, that could float on the Earth,” said Yu, lead author of a study published Jan. 4 in the journal Geophysics. in the water, and then eventually sank.” Research Letters.

Scientists aim to learn as much as possible about Titan before sending specific missions to the moon. The Dragonfly mission, led by the Johns Hopkins University Applied Physics Laboratory in partnership with NASA, is scheduled to launch in 2028 and arrive at Titan in the 2030s.

Analyze an unusual world

A variety of organic molecules are present in Titan’s upper atmosphere, such as nitriles, hydrocarbons, and benzene. Surface temperatures are so cold (-179 degrees Celsius) that rivers and lakes are eroded by liquid methane, just as rocks and lava helped form the Earth’s landforms and canals.

Organic molecules in Titan’s atmosphere stick together to form clumps before freezing and falling to the moon’s surface. Dark plains and dunes of organic material have been observed on Titan, and scientists believe these features are largely caused by Titan’s “snow.”

But what happens when hydrocarbon snow falls on the unusually smooth surface of Titan’s lakes and rivers of liquid gas? Yu and his colleagues looked at different scenarios that might occur.

Yu’s team determined that solid organic materials falling from the upper atmosphere would not dissolve when landing on Titan’s liquid body because they were already saturated with organic particles.

Infrared images captured by instruments on the Cassini spacecraft provide the clearest view of Titan from beneath its thick haze.

“In order for us to see these magical islands, they can’t just float for a second and then sink,” Yu said. “They have to float for a while, but not forever.”

But liquid ethane and methane have lower surface tension, which means it’s harder for solids to float on them.

Yu’s team simulated different models and determined that frozen solid material would not float unless it was porous, like honeycomb or Swiss cheese. Small particles are also unlikely to float on their own unless they are large enough.

The team’s analysis led to a scenario in which frozen hydrocarbon solids accumulated near the coast before breaking off and floating on the surface like glaciers on Earth. Liquid methane slowly seeps into the frozen cumulus clouds, eventually causing them to disappear from view.

Additionally, the researchers say there may be a thin layer of frozen solids in Titan’s oceans and lakes, which could explain why Titan’s liquid body is so slippery.

approaching titan

Over the next decade, Dragonfly is expected to study Titan’s equatorial plains of organic matter, rather than its liquid body.

The helicopter lander will sample materials on Titan’s surface, study the potential habitability of its unique environment, and determine what chemical processes are occurring on the moon.

Organic chemicals essential for life on Earth, such as nitrogen, oxygen and other carbon-based molecules, are also found on Titan. Beneath Titan’s thick icy shell is a salty ocean, unlike other fascinating moons in the ocean world that surrounds Saturn, such as Enceladus or Jupiter’s moon Europa, which are considered one of the best places to search for life beyond. Earth.

According to NASA, Titan sounds inhospitable, but depending on its different chemical composition and shape, conditions there could be conducive to life beyond our current understanding.

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