Titan is the largest moon of Saturn, a frigid world with a thick atmosphere as well as rivers and lakes of liquid hydrocarbons. Data gathered from the Cassini spacecraft indicates complex chemistry on the moon – one that researchers have now tried to recreate in the lab.
The recreation led to the discovery that Titan may have crystals that wouldn’t naturally form on Earth. Unlike minerals from our planet that are made of carbonates or silicates, some of Titan’s crystals may be made of organic molecules because it’s so cold. The findings are presented at the 2019 Astrobiology Science Conference.
The team recreated the atmosphere by using liquid nitrogen to cool down the system and mixing in Titan's atmosphere of gaseous nitrogen, methane, and ethane. The first substance they produced was a peculiar co-crystal, where the traditionally hexagonal molecules of benzene (a component of gasoline) were rearranged to hold a molecule of ethane inside them.
Another particularly fascinating product they witnessed is the formation of co-crystals made of acetylene and butane. On Earth, these two substances are gasses, but on Titan's chilling -179°C (-290°F), they're in a solid state. This co-crystal is likely more abundant on Titan than the benzene one, based on what we know of the composition of Titan’s atmosphere.
Researchers have shown that these compounds would likely dissolve in the methane and ethane that makes up the lakes. As they seasonally evaporate, these crystals form deposits, a bit like the rings that can sometimes form around a bathtub. These substances might be covering the shores, beaches, and banks of Titan.
"We don't know yet if we have these bathtub rings," lead author Morgan Cable, from NASA’s Jet Propulsion Laboratory, said in a statement. "It's hard to see through Titan's hazy atmosphere."
Neither Cassini nor its lander, Huygens, were designed for such a specific task as finding traces of these possible minerals. Cassini ended its mission almost two years ago. A potential mission to Saturn called Dragonfly might be selected to launch in 2024, which would see a drone flying around Titan to study its chemistry in detail. If selected, it's possible these unearthly crystals might be just over a decade away from actually being discovered out there.