NASA scientists identified a molecule in Titan’s atmosphere that has never been detected in any other atmosphere.
In fact, many chemists have probably barely heard of it or know how to pronounce it: cyclopropenylidene, or C3H2.
This image was returned January 14, 2005, by the European Space Agency’s Huygens probe during its successful descent to Titan’s surface.
This is the colored view that’s been processed to add reflection spectra data to give better indication of the actual color of Titan’s surface.
They noticed C3H2, which is made of carbon and hydrogen, while sifting through a spectrum of unique light signatures collected by the telescope; these revealed the chemical makeup of Titan’s atmosphere by the energy its molecules emitted or absorbed.
“When I realized I was looking at cyclopropenylidene, my first thought was, ‘Well, this is really unexpected,’” said Conor Nixon, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who led the ALMA search.
But dense atmospheres like Titan’s are hives of chemical activity.
Nixon’s team was able to identify small amounts of C3H2 at Titan likely because they were looking in the upper layers of the moon’s atmosphere, where there are fewer other gases for C3H2 to interact with.
Scientists don’t yet know why cyclopropenylidene would show up in Titan’s atmosphere but no other atmosphere.
The types of molecules that might be sitting on Titan’s surface could be the same ones that formed the building blocks of life on Earth.
“We think of Titan as a real-life laboratory where we can see similar chemistry to that of ancient Earth when life was taking hold here,” said Melissa Trainer, a NASA Goddard astrobiologist.
“We’ll be looking for bigger molecules than C3H2,” Trainer said, “but we need to know what’s happening in the atmosphere to understand the chemical reactions that lead complex organic molecules to form and rain down to the surface.
Cyclopropenylidene is the only other “cyclic,” or closed-loop, molecule besides benzene to have been found in Titan’s atmosphere so far.
Although C3H2 is not known to be used in modern-day biological reactions, closed-loop molecules like it are important because they form the backbone rings for the nucleobases of DNA, the complex chemical structure that carries the genetic code of life, and RNA, another critical compound for life’s functions.
Scientists like Thelen and Nixon are using large and highly sensitive Earth-based telescopes to look for the simplest life-related carbon molecules they can find in Titan’s atmosphere.
Recently, NASA Goddard scientist Conor Nixon, along with his team, found this unique molecule in Titan’s atmosphere; the first time it has been detected outside of a molecular cloud.
Cyclopropenylidene is the only other closed-loop molecule besides benzene to have been detected at Titan.
(The instrument – called a mass spectrometer – picked up hints of many mysterious molecules at Titan that scientists are still trying to identify.) Indeed, Cassini had spotted evidence for an electrically charged version of the same molecule, C3H3+J
Given that it’s a rare find, scientists are trying to learn more about cyclopropenylidene and how it might interact with gases in Titan’s atmosphere.
“It’s a very weird little molecule, so it’s not going be the kind you learn about in high school chemistry or even undergraduate chemistry,” said Michael Malaska, a JPL planetary scientist who worked in the pharmaceutical industry before falling in love with Titan and switching careers to study it.
But, Malaska said, finding molecules like C3H2 is really important in seeing the big picture of Titan: “Every little piece and part you can discover can help you put together the huge puzzle of all the things going on there.”!
Reference: “Detection of Cyclopropenylidene on Titan with ALMA” by Conor A.
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