The strange chemical world of Titan is simulated in tiny tubes

The landscape of Titan, Saturn’s largest moon, is both familiar and super weird. 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 made up of liquid methane, an organic molecule made up of one carbon and four hydrogen atoms. Researchers believe this swirling mixture of methane, combined with the moon’s nitrogen-charged atmosphere, surface water ice, and possibly the energy of a volcano or meteor impact , could have been the perfect recipe to create some kind of simple life form. This is why Titan is one of the potential hotspots for life in the solar system, along with Jupiter. ice moon europe.

Several expeditions are preparing to embark on these distant worlds in the coming decade: one European Mission in Europe in 2022, NASA’s Europa Clipper in 2024, and the innovative NASA Dragonfly helicopter at Titan in 2027.

But before these spaceships leave, scientists want to get a feel for how planetary chemistry works on these moons. Now a researcher has recreated Titan’s environment in a small glass cylinder and mixed organic chemicals under the same temperature and pressure as on this moon. Organic molecules that are liquid on Earth, such as methane and benzene, become solid icy mineral crystals on Titan because it is so cold, sometimes down to -290 degrees Fahrenheit, according to Tomče Runčevski, assistant professor of chemistry at Southern Methodist University, and principal investigator of the experiment presented this week at the American Chemical Society meeting.

In a series of experiments, Runčevski took tiny glass tubes, sucked air out of them with a pump, and added water ice. Then, one at a time, he added nitrogen, methane, its relative chemical 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 then applied a pressure equivalent to about 1.45 times Earth’s atmosphere and reduced the temperature by surrounding the vials with extremely cold air.

“We are introducing a sequence of chemicals as they would be on Titan,” Runčevski explains. “We will put first [the glass tube] in a vacuum to remove all the oxygen, then we put methane to mimic the atmosphere on Titan. And then we put the other organic molecules in and study them.

Under the atmospheric pressure and temperature of this moon, he discovered that two organic molecules abundant on Titan and toxic to humans here on Earth – acetonitrile and propionitrile – became 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 off as gases in the atmosphere, then condense into aerosols, then rain down on the moon’s surface and become lumps of solid minerals in many forms.

I understand if you’ve hit chemistry overload. But if you care about biology, or more precisely exobiology, the science of life to other planets, then the shape and form of chemical compounds are critical. This is the first time that these two chemicals have been combined into a crystalline form on Earth under the conditions present on Titan.

Another important finding is that the outer facet of the crystal also has a slight electrical charge, or polarity, on its surface. This surface charge can attract other molecules such as water, which would be needed to form the building blocks of carbon-based life.

This new experiment doesn’t prove there is life on Titan, but it does mean researchers can discover new things about its eerie, icy surface environment before NASA’s Dragonfly spacecraft even lands there. . “We cannot say that there is or that there is no life on Titan, but we can certainly say that the conditions are there,” Runčevski said. “Titan is the closest thing to Earth that can harbor life in a way that we perceive to be similar to life on Earth.”

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