Strange, Alien Shores of Titan’s Lakes

Lakes of Saturn's Titan


“To confirm whether the lakes of Saturn’s moon, Titan, has shoreline rings of co-crystals and other, undiscovered, hydrocarbon crystals, scientists will have to wait until a spacecraft can visit its shorelines,” said Morgan Cable of NASA’s Jet Propulsion Laboratory at the California Institute of Technology.

The frigid lake shores of Saturn’s moon Titan might be encrusted with strange, unearthly minerals, according to new research. Scientists re-creating Titan-esque conditions in their laboratory have discovered new compounds and minerals not found on Earth, including a co-crystal made of solid acetylene and butane.

“The atmosphere of Titan is very complex, and it does synthesize complex organic molecules — the bricks of life,” said Cyril Grima, a research associate at the Institute for Geophysics at the University of Texas at Austin who was not part of the JPL research. “It may act as a laboratory of sorts, where you can see how basic molecules can be transformed into more complex molecules that could eventually lead to life. On top of that, it’s also thought to have an ocean of liquid water beneath its icy crust.”

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Acetylene and butane exist on Earth as gases and are commonly used for welding and camp stove fuel. On Titan, with its extremely cold temperatures, acetylene and butane are solid and combine to form crystals, the new research found.

The new mineral might be responsible for the bathtub rings that are suspected to exist around Titan’s hydrocarbon lakes, according to Cable, who will present the new research at the 2019 Astrobiology Science Conference.

Titan’s lakes are filled with liquid hydrocarbons. Previous research using images and data gathered during the Cassini mission has shown that lakes in the moon’s dry regions near the equator contain signs of evaporated material left behind, like rings on a bathtub.

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To create Titan-like conditions in the laboratory, the researchers started with a custom-built cryostat, an apparatus to keep things cold. They filled the cryostat with liquid nitrogen to bring the temperature down. They then warmed the chamber slightly, so the nitrogen turned to gas, which is mostly what Titan’s atmosphere contains. Next, they threw in what abounds on Titan, methane and ethane, as well as other carbon-containing molecules, and looked for what formed.

The first things to drop out of their Titan hydrocarbon soup were benzene crystals. Benzene is perhaps best known as a component of gasoline and is a snowflake-shaped molecule made out of a hexagonal ring of carbon atoms. But Titan benzene held a surprise: The molecules rearranged themselves and allowed ethane molecules inside, creating a co-crystal.

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The researchers then discovered the acetylene and butane co-crystal, which is probably a lot more common on Titan than benzene crystals, based on what’s known about the moon’s composition, Cable said.

In the moon’s cold climate, the acetylene-butane co-crystals might form rings around the moon’s lakes as the liquid hydrocarbons evaporate and the minerals drop out – in the same way that salts can form crusts on the shores of Earth’s lakes and seas, according to Cable.

“We don’t know yet if we have these bathtub rings,” Cable said. “It’s hard to see through Titan’s hazy atmosphere.”

The Daily Galaxy, Max Goldberg, via AGU 

The image at the top of the page: An artist’s rendering of the surface of Titan, with thanks to Benjamin de Bivort, / CC BY-SA 3.0.

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