Saturn's largest moon, Titan, is the only moon in our solar system that has a dense atmosphere of nitrogen and methane – four times denser than Earth's. And according to a study published earlier this month in the Astronomical Journal, it is in this atmosphere that scientists recently discovered a molecule that has never been found in any other atmosphere.
Titan is usually compared to Earth for its specific properties, such as its atmosphere, its earth-like liquid on the surface, and its subsurface ocean. Researchers are wondering if Titan may be habitable.
The particle, called cyclopropenylidene, or C3H2, is composed of carbon and hydrogen, a simple carbon-based molecule that could be the basis for potential life on Titan.
According to CNN, this molecule was first noticed by researchers who, thanks to the radio telescope observatory of the Atacama Large Millimeter/submillimeter Array (ALMA) of telescopes in Chile, caught a range of light signatures which revealed the molecule.
"When I realized I was looking at cyclopropenylidene, my first thought was, 'Well, this is really unexpected,'" said lead study author Conor Nixon, planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a statement.
C3H2 is the second cyclic molecule detected at Titan, reported the study. Benzene, the first one discovered in 2003, is also an organic chemical compound composed of carbon and hydrogen atoms.
Cyclic molecules are crucial because they form the backbone rings for the nucleobases of DNA, according to NASA.
"The cyclic nature of them opens up this extra branch of chemistry that allows you to build these biologically important molecules," said study co-author Alexander Thelen, an astrobiologist at Goddard, in a statement.
The molecule has already been detected across our galaxy, mainly in molecular clouds of gas and dust including the Taurus Molecular Cloud. But finding it in an atmosphere is very different.
"Titan is unique in our solar system," Nixon said. "It has proved to be a treasure trove of new molecules."
Titan will be explored by NASA's Dragonfly mission in the future. Dragonfly will launch in 2026 and reach Titan in 2034.
Dragonfly will spend two and a half years flying around Titan. It only has propellers, with skids to land but no wheels to allow it to roam over the surface. The mission will also explore Titan's atmosphere, surface properties, subsurface ocean and liquid on the surface.
"We're trying to figure out if Titan is habitable," said Rosaly Lopes, a senior research scientist and Titan expert at NASA's Jet Propulsion Laboratory, in a statement.
"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 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 and Dragonfly mission deputy principal investigator, in a statement.
"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."
Earth and Titan could be very similar. Understanding the organic material sitting on Titan's surface could reveal more about Earth's history.