On Earth, butane is a gas used in lighters and camping stoves (it’s a liquid under pressure) while acetylene is a gas most often used in welding because of the high temperature of its flame. On Titan, Saturn’s largest moon that is actually larger than the planet Mercury, the temperature is so cold that these two chemical compounds freeze together to form ‘alien’ crystals that can’t form in nature on Earth. Scientists recently created these alien crystals in a lab and think they may be what forms the mysterious rings around liquid lakes on the surface of Titan. Do bathtubs on Titan have them too?
One of the things that attracts kids to science is the appeal of mixing substances together and seeing what happens … while wearing protective gear and under adult supervision, of course. (Yeah, right.) That appeal never goes away – it’s the way scientists at NASA's Jet Propulsion Laboratory discovered the alien crystals. According to their paper presented this week at the 2019 Astrobiological Science Conference in Seattle, Washington, the researchers built a mini Titan in a cryostat, a container used to maintain low cryogenic temperatures. To chill things off, they first filled the crystat with liquid nitrogen, every scientist’s favorite form of entertainment. After freezing flowers and making ice cream, they raised the temperature enough to turn the nitrogen into gas, thus creating a Titan atmosphere in the cryostat.
Then it was time for mixing up stuff. Based on atmospheric and surface data from Cassini–Huygens flybys and landing, they tossed in methane, ethane, acetylene, butane and other carbon-containing molecules. The first things to form were benzene crystals – nothing unusual there. But then the ethane molecules combined with the benzene to form benzene-ethane co-crystals that don’t naturally exist on Earth. Following that came the next alien co-crystals – a combination of acetylene and butane that’s also unheard of in nature.
Is this a big deal? Well, it got the JPL scientists excited, as mixing things to see what happens usually does. Is it big enough to inspire governments to budget future space missions to Titan? That’s a tough one. A robotic mission to the surface would confirm that Titan’s lakes are a liquid hydrocarbon soup and that what look like bathtub rings around their edges are made of these or other kinds of alien crystals that form as the lake evaporates and the gases combine in new ways with the liquids. Does it mean there could be life on Titan? No, and that’s the holy grail of space funding as missions to nearby space bodies seem to be implicitly apocalyptic as they search for signs that either there’s life already there or they have the elements for sustaining human life and colonization.
The alien crystals are Interesting, but the days of exploring space for the sake of pure exploration are not here yet.
Will they ever be?