September 30, 2013
Cassini Discovers Titan Atmosphere Loaded With Plastics Ingredient
[ Watch the Video: Plastics Chemical Found In Titan's Atmosphere ]
Brett Smith for redOrbit.com - Your Universe Online
Using the Cassini spacecraft’s examinations in the infrared spectrum, NASA researchers have identified atmospheric propylene – which is used to make plastic containers here on Earth – on Saturn’s moon Titan.
The discovery marks the first time the plastic ingredient has been seen outside of Earth and is described in a new paper, published in Astrophysical Journal Letters.
"This chemical is all around us in everyday life, strung together in long chains to form a plastic called polypropylene," said Conor Nixon, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "That plastic container at the grocery store with the recycling code 5 on the bottom -- that's polypropylene."
Referred to as one of NASA's flagship spacecrafts, Cassini is currently orbiting Saturn and gathering data on both the planet and its numerous moons. The spacecraft was able to provide evidence that led to the discovery of polypropylene in Titan's lower atmosphere through its Composite Infrared Spectrometer (CIRS). The instrument scanned Titan’s atmosphere to reveal, with a high degree of confidence, the chemical’s infrared signal at various altitudes within the lower atmosphere.
The discovery solves a riddle posed by observations of Titan made during the Voyager 1 spacecraft’s flyby of this moon in 1980. At the time, the ship identified many of the gases in Titan's atmosphere as hydrocarbons, the key molecules in Earth’s fossil fuels.
Scientists had known that hydrocarbons form on Titan after radiation from the sun breaks apart atmospheric methane, the second-most plentiful gas on the Saturnian moon. The hydrogen and carbon then re-form into longer chains with two, three or more carbons. The two-carbon family includes the flammable gas ethane, while propane belongs to the three-carbon family.
The Voyager observations found all possible affiliates of the one- and two-carbon families in Titan's atmosphere. However, the spacecraft only found propane and propyne from the three-carbon family, meaning the middle chemicals, including propylene, were missing.
Scientists continued to find more chemicals in Titan's atmosphere using ground- and space-based assets, but were unable to find any evidence of propylene. A thorough investigation of CIRS data finally revealed the missing piece of the puzzle.
[ Watch the Video: Propylene On Titan ]
"This measurement was very difficult to make because propylene's weak signature is crowded by related chemicals with much stronger signals," said Michael Flasar, Goddard scientist and principal investigator for CIRS. "This success boosts our confidence that we will find still more chemicals long hidden in Titan's atmosphere."
Scientists had seen hints of atmospheric propylene with Cassini's mass spectrometer, an instrument that looks at the makeup of Titan's atmosphere. However, the researchers were unable to make a definitive declaration based on spectrometry data.
"I am always excited when scientists discover a molecule that has never been observed before in an atmosphere," said Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "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."