Plastic is pretty much a metaphor for unnatural—a plastic smile, plastic surgery, fake plastic trees. Even when the Curiosity rover discovered plastic on Mars last year, that turned out to be fake, too.
In an authenticity-obsessed world, plastic has gotten a bad rap (or is that wrap?). Plastic is made up of organic molecules—organic meaning there’s carbon in them, not that it was raised cruelty-free under fair trade conditions. If your non-chemistry-class definition of organic requires that a plant or animal be involved, know that the petrochemicals which provide the base stock for what we commonly consider plastic is made up of the carcasses of ancient micro-organisms.
Cassini’s discovery carries with it a handful of firsts, including the first definitive discovery of plastics outside of Earth, and the first molecule that Cassini’s hard-working “composite infrared spectrometer” has discovered on Titan.
Anyway, while the things we might recognize as plastic are generally synthetic, there are naturally occurring polymers (all plastics are polymers, but not all polymers are plastics)—cellulose, rubber, amber, and shellac. And there are even a few naturally occurring plastics, like animal horns and tortoiseshell. But while pedants will be happy with these distinctions, none pass muster as, you know, plastic. It’s perhaps a Potter Stewart-ian distinction, but, well, I’m not buying Tide packaged in turtles.
But now science has discovered plastic ... in space. And blessedly, it’s not pollution from Earth (we're not counting space junk). Using its on-board spectrometer, the Cassini spacecraft has discovered propylene in the lower atmosphere of Saturn’s moon Titan. And propylene (A.K.A. propene or methylethylene) is by anyone’s definition plastic. As Conor Nixon, the lead author on a paper describing this find, explained in a release, "This chemical is all around us in everyday life, strung together in long chains to form a plastic called polypropylene. That plastic container at the grocery store with the recycling code 5 on the bottom -- that's polypropylene." Heck, here on Earth, even some trees release propylene naturally.
Cassini’s discovery carries with it a handful of firsts, including the first definitive discovery of plastics outside of Earth, and the first molecule that Cassini’s hard-working “composite infrared spectrometer” has discovered on Titan. But this first doesn’t carry with it indication of something intelligent synthesizing plastics on Titan. Based on chemical analyses dating back to Voyager 1’s flyby in the 1980s, scientists have known that Titan’s atmosphere is a hodge-podge of hydrocarbons—JPL’s Scott Edginton described it as a “chemical zoo.” Propylene was actually something scientists expected to find since its chemical kissing cousins were already known to be present.
Things like amino acids, the building blocks of life as we know it, have been found floating through the cosmos, possibly as interstellar ride-sharers. It’s all somewhat reminiscent of Douglas Adams’ Hitchhiker’s Guide to the Universe universe, where planets of mattresses and ballpoints cavort naturally: "Very few things actually get manufactured these days, because in an infinitely large Universe such as, for instance, the one in which we live, most things one could possibly imagine, and a lot of things one would rather not, grow somewhere."