Titan's Strange Chemical World Gets Simulated in Tiny Tubes

Eric Niiler writes via Wired: The landscape of Titan, Saturn's largest moon, is both familiar and strange. Like Earth, Titan has rivers, lakes, clouds, and falling raindrops, as well as mountains of ice and a thick atmosphere. But instead of water, Titan's chemical cycle is composed of liquid methane, an organic molecule made from one carbon and four hydrogen atoms. Researchers believe this swirling mixture of methane, combined with the moon's nitrogen-laden atmosphere, surface water ice, and maybe some energy from either a volcano or a meteor impact, might have been the perfect recipe to create some kind of simple life form. [...] Now, A researcher has recreated Titan's environment in a small glass cylinder and mixed organic chemicals under the same temperature and pressure conditions found on that moon. Organic molecules that are liquid on Earth -- such as methane and benzene -- become solid icy mineral crystals on Titan because it's so cold, sometimes down to -290 Fahrenheit, according to Tomce Runcevski, an assistant professor of chemistry at Southern Methodist University, and the principal investigator on a study presented this week at the American Chemical Society meeting. In a series of experiments, Runcevski took tiny glass tubes, sucked the air out of them with a pump, and added water ice. Then, one at a time, he added nitrogen, methane, its chemical relative ethane, and other organic compounds. Each time, he varied the composition of the chemical mixture inside the glass cylinders to see what would happen. He next applied pressure -- equivalent to about 1.45 times Earth's atmosphere -- and reduced the temperature by surrounding the vials with extremely cold air. [...] Under that moon's atmospheric pressure and temperature, he found that two organic molecules abundant on Titan and toxic to humans here on Earth -- acetonitrile and propionitrile -- become a single crystalline form. On Titan, these two molecules are formed by the combination of nitrogen and methane, plus energy from the sun, Saturn's magnetic field, and cosmic rays. Acetonitrile and propionitrile start as a gas in the atmosphere, then condense into aerosols, and then rain down onto the moon's surface and become chunks of solid minerals in several forms. It's the first time that these two chemicals have been combined into a crystal shape on Earth under the conditions present on Titan. Another important finding is that the outer facet of the crystal also has a slight electric charge, or polarity, on its surface. That surface charge can attract other molecules such as water -- which would be necessary to form the building blocks of carbon-based life. This new experiment doesn't prove that there's life on Titan, but it means that researchers can discover new things about its weird, frigid surface environment even before the NASA Dragonfly spacecraft lands there.

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