NASA's Cassini probe has detected propylene, a chemical used to make everyday plastic, in the atmosphere of Saturn's moon Titan. This is the first time this chemical has been identified on any planet or moon other than Earth.
Propylene, or propene, is the monomer, or repeating chemical unit, in polypropylene (PP), a common plastic used in many common products.
Its toughness and flexibility combined with its low cost make it popular for packaging, textiles, and even car bumpers. It also has very good chemical resistance, making it ideal for containers and laboratory equipment.
Whilst the plastic itself has not been found on Titan, the discovery of the monomer in space is still an important discovery, as chemicals as complex as propylene are incredibly rare outside of Earth's rich mix of chemicals.
NASA's Cassini spacecraft looks toward the night side of Saturn's largest moon and sees sunlight scattering through the periphery of Titan's atmosphere and forming a ring of color. Image credit: NASA JPL
Titan is one of the most fascinating objects in the solar system. With its atmosphere of thick brown haze obscuring the surface, very little was known about its composition until quite recently.
NASA's Cassini probe, currently making its way around the Saturnian system, has gathered a wealth of data about Titan, using chemical analysis and advanced imaging techniques to tell us more about the planet's unusual thick atmosphere, and its alien surface.
Previous observations of the atmosphere on Titan, both from Earth and from space, have identified a large number of light hydrocarbons, such as ethylene and propane.
These are created when sunlight hitting the atmosphere breaks up molecules of methane into reactive fragments, which can combine to make these larger organic molecules.
As more complex chemicals continues to be discovered, propylene continued to be elusive. Now, the composite infrared spectrometer (CIRS) aboard Cassini - one of its many chemical analysis instruments - has definitively detected propylene, adding it to the detailed picture of Titan that NASA is building.
"I am always excited when scientists discover a molecule that has never been observed before in an atmosphere. This new piece of the puzzle will provide an additional test of how well we understand the chemical zoo that makes up Titan's atmosphere."
Scott Edgington, Cassini deputy project scientist at JPL