We have news this week of yet another interesting molecule found in the atmosphere of a world we hope harbors life. This time, that world is Saturn’s moon, Titan, and that molecule is, bear with me here, cyclopropenylidene, which is three carbon atoms and two hydrogen atoms. Scientists think this compound could be the precursor to even more complex molecules that could feed life on Titan.

A team of researchers looked through spectra collected by the Atacama Large Millimeter/submillimeter Array (ALMA) to understand the composition of Titan’s atmosphere and found the molecule in their analysis. While C3H2 has been found elsewhere in the galaxy, it has not been found in an atmosphere. The molecule has only been found in pockets of interstellar gas and dust because it is highly reactive with other molecules, and in interstellar space, the conditions are too cold for those reactions. In this instance, cyclopropenylidene was found in the upper layers of Titan’s atmosphere, where there are not many other gases to react with.

The findings are intriguing because Titan’s thick atmosphere and meteorological conditions are unique among moons in our solar system. As the press release states: Titan’s atmosphere is made mostly of nitrogen, like Earth’s, with a hint of methane. When methane and nitrogen molecules break apart under the glare of the Sun, their component atoms unleash a complex web of organic chemistry that has captivated scientists and thrust this moon to the top of the list of the most important targets in NASA’s search for present or past life in the solar system.

To find out if Titan is habitable, we need to understand what kinds of compounds make it from the atmosphere to the surface, which is where the upcoming Dragonfly mission comes in. Titan’s surface could have similar conditions to early Earth as it was 3.8 to 2.5 billion years ago when our atmosphere had more methane than oxygen.

Melissa Trainer, deputy principal investigator of Dragonfly stated: 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. We’ll be looking for bigger molecules than C3H2, 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, like benzene, is a closed-loop molecule that could be involved in creating the structure of DNA and RNA. For now, scientists are working to learn more about this small compound and understand how it might react with other gases in Titan’s dense atmosphere. We will have to wait for Dragonfly to arrive before we answer the question of what compounds make it to the surface and how habitable that surface might be for primordial life.

More Information

NASA article 

“Detection of Cyclopropenylidene on Titan with ALMA,” C.A. Nixon, et al., 15 October 2020, Astronomical Journal.