Propylene, a chemical used to make commercial plastics such as food storage containers, was detected on Saturn's moon Titan.
This finding marks the first time a plastic ingredient has been found on any planetary object other than Earth, a NASA's Jet Propulsion Laboratory (JPL) press release reported.
The low concentration of the chemical was found in Titan's lower atmosphere by the Cassini spacecraft's composite infrared spectrometer (CIRS), which measures the infrared light emitted from Saturn and its moons. This substance is the first molecule to be discovered on Titan using the CIRS technology. CIRS can identify different layers of gas in the atmosphere by looking at its unique "thermal fingerprint."
"This chemical is all around us in everyday life, strung together in long chains to form a plastic called polypropylene," Conor Nixon, a planetary scientist at NASA's Goddard Space Flight Center and lead author of the paper, said. "That plastic container at the grocery store with the recycling code 5 on the bottom -- that's polypropylene."
The finding explains a mystery discover during a Voyager 1 flyby in the 1980s. The craft identified the hazy gas in Titan's atmosphere as being composed of hydrocarbons, which are contained in Earth's fossil fuels.
"On Titan, hydrocarbons form after sunlight breaks apart methane, the second-most plentiful gas in that atmosphere. The newly freed fragments can link up to form chains with two, three or more carbons. The family of chemicals with two carbons includes the flammable gas ethane. Propane, a common fuel for portable stoves, belongs to the three-carbon family," the press release reported.
Voyager had also found propane, which is the heaviest of the three-carbon family, and propyne which is considerably lighter. Researchers had been wondering if that meant propylene was present as well. The scientists found a number of chemicals Titan's atmosphere, but propylene had always remained elusive.
"This measurement was very difficult to make because propylene's weak signature is crowded by related chemicals with much stronger signals," Michael Flasar, Goddard scientist and principal investigator for CIRS, said. "This success boosts our confidence that we will find still more chemicals long hidden in Titan's atmosphere."
Other Cassini equipment had hinted at proylene's existence in the past, but had never been able to find true evidence of its existence on Titan.
"I am always excited when scientists discover a molecule that has never been observed before in an atmosphere," Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory, said. "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."
