Weird molecule found in Titan's atmosphere hints at complex chemistry
NASA scientists have discovered a “weird” molecule called cyclopropenylidene, or C3H2, in the atmosphere of Saturn’s moon Titan. The simple carbon-based molecule has never been seen in an atmosphere before, and it could give rise to more complex compounds and contribute to the conditions needed for life.
Titan is one of the most fascinating place in the solar system. It’s the only world besides Earth that we know to have stable liquid on its surface, forming lakes, rivers and seas – but instead of water, it’s liquid methane and ethane. That leads to a weather cycle much like ours, with evaporation, rain, erosion, organic dust storms and tectonic activity shaping its landscape.
Now, astronomers have discovered a weird new quirk of Titan. Using the Atacama Large MIllimeter/submillimeter Array (ALMA), scientists observed the light spectrum of the moon, which can provide insight into the chemical composition of its atmosphere by studying the wavelengths that are emitted or absorbed by the molecules there.
In two separate data sets, the team identified a strange fingerprint as that of cyclopropenylidene. Its presence is surprising – it’s a very reactive molecule, so in a warm(ish) environment like Titan’s atmosphere it should readily break down into other forms. As such, C3H2 has previously only been detected in interstellar dust clouds, where it’s too cold and diffuse for these kinds of chemical reactions to take place.
Titan is already considered one of the most promising places to search for extraterrestrial life, thanks to its Earth-like dynamics, and this latest discovery lends weight to the idea. So-called “closed loop” molecules form an important part of the backbone of DNA and RNA, and while C3H2 itself isn’t known to play a role in these reactions, it’s the simplest and smallest closed-loop molecule ever found in any atmosphere. There could be weird life-giving chemistry at work on this moon, resulting in life that’s not water-based.
“We’re trying to figure out if Titan is habitable,” says Rosaly Lopes, a Titan expert at NASA’s Jet Propulsion Laboratory (JPL). “So we want to know what compounds from the atmosphere get to the surface, and then, whether that material can get through the ice crust to the ocean below, because we think the ocean is where the habitable conditions are.”
We may get a closer look in the not-too-distant future. NASA plans to send a robotic rotorcraft called Dragonfly to Titan in 2034, where it will hop around looking for signs of past or present life. Eventually it could even be joined by a submarine exploring the depths of those alien oceans.
The new study was published in the Astronomical Journal.