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The “weird” molecules found on Titan have never been found in any atmosphere



Saturn’s originally weird Saturn Moon has become a bit strange. Astronomers have detected cyclopropene (C3H2) in their atmosphere, an extremely rare carbon-based molecule that has high reactivity and can only exist on Earth under laboratory conditions.

In fact, it is so rare that it has never been found in the atmosphere, the solar system or elsewhere. The only place it can remain stable is the cold sky of interstellar space. But this may be the basis of more complex organic molecules, which may one day lead to life.

Melissa Trainer, an astrobiologist at NASA’s Goddard Space Flight Center, said: “We think of Titan as a real laboratory where we can see chemicals similar to ancient Earth. “It will land on the moon in the Dragonfly mission launched in 2027.

“We will look for molecules larger than C3H2, but we need to know what is going on in the atmosphere to understand the chemical reactions that cause complex organic molecules to form and descend to the surface.”

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Cyclopropenyl (and even described by NASA researchers as a “very strange small molecule”) does not last long under atmospheric conditions because it reacts very quickly and easily with other molecules to form other compounds.

Once this is done, it is no longer cyclopropene. In interstellar space, any gas or dust is usually very cold and very dispersed, which means that the interaction between the compounds is small and the cyclopropenyl group can linger.

Titans are very different from interstellar space. A bit humid, lakes with hydrocarbons, clouds of hydrocarbons, mainly nitrogen, and a little methane. The thickness of the atmosphere is four times that of the earth’s atmosphere (the latter is also the main source of nitrogen). Below the surface, scientists believe that there is a huge ocean of salt water.

In 2016, a team led by planetary scientist Conor Nixon of NASA’s Goddard Space Flight Center used Chile’s Atacama Large Millimeter/Submillimeter Array (ALMA) to explore the lunar atmosphere and find organic molecular.

It is located in the fragile upper atmosphere higher above the surface, where they detected unknown chemical signatures. By comparing it with a chemical signature database, the research team identified the molecule as cyclopropene. The thin atmosphere at that height may help the molecule’s survival, but why it appeared on Titan but no other world is a mystery.

Nixon said: “When I realized that I was working on cyclopropenyl, my first thought was,’Well, this is really unexpected.’ “Titanium is unique in our solar system. Facts have proved that it is a treasure trove of new molecules. “

The cyclopropene subunit is of particular interest because it is a so-called ring molecule. Its three carbon atoms are connected together in a ring (well, a triangle, but the principle is the same). Although the cyclopropene subunit itself has no biological effect, the nucleobases of DNA and RNA are based on such molecular rings.

Alexander Seren, an astrobiologist at NASA’s Goddard Space Flight Center, said: “Their cyclical nature opens up this additional branch of chemistry, allowing you to build these biologically important molecules.”

The smaller the molecule, the greater its potential-reactions involving smaller molecules with fewer bonds are expected to occur faster than reactions involving larger, more complex molecules. This means that reactions involving smaller molecules, purely through numbers, will lead to a more diverse range of results.

Previously, benzene (C6H6) was considered the smallest hydrocarbon ring molecule found in any atmosphere (including the Titans). Cyclopropenyl has a certain rhythm.

Titan is already a honeycomb of organic chemical activity. Nitrogen and methane decompose in the sun, triggering a series of chemical reactions. Whether these reactions can lead to life is a question that scientists are eager to answer.

Rosalie Lopez, a geologist at NASA’s Jet Propulsion Laboratory, said: “We are trying to determine whether Titan is suitable for habitation.” “So we want to know what compounds in the atmosphere reach the ground, and then, the substance Is it possible to reach the ocean below through the ice shell, because we think the ocean is a habitable condition.”

Finding out which compounds are present in the atmosphere is a very important step in this research process. Cyclopropenyl may be small and strange, but this extremely rare molecule may be a key part of Titan’s chemistry puzzle. Now, we just need to figure out its location.

The research has been published in Astronomy Magazine.


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