NASA’s Cassini spacecraft, which has been exploring Saturn and its many moons (roughly 60 discovered so far) since 2004, recently discovered an ingredient on the moon Titan that is very common here on Earth, one which is probably in your kitchen right now. Propylene, which is used in making food-storage containers and other plastic consumer products, has never been detected anywhere outside of Earth, until now.
“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.”
The discovery came courtesy of Cassini’s Composite Infrared Spectrometer, or CIRS, which measures the infrared light emitted from Saturn and its moons in the same manner you feel heat over a campfire. CIRS can identify a particular gas in an atmosphere from its unique thermal fingerprint, and researchers isolated the same signal at different altitudes within Titan’s atmosphere to identify the plastic ingredient—which they already believed was there based on observations made by Voyager-1 in 1980 when it flew by Titan and Saturn.
“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.”
Titan has intrigued researchers for quite some time because it is the most Earth-like world known to science, with an atmosphere rich in organic compounds such as nitrogen. Organic molecules that contain carbon and hydrogen, which often include oxygen and other elements similar to what is found in Earth’s atmosphere, are also found on Titan. The chemicals that make up petroleum and other fossil fuels on Earth are also found in Titan’s atmosphere. Methane is also found in large quantities on Titan; there are even liquid seas of methane present on the surface, the only liquid lakes yet discovered anywhere besides Earth.
Video Credit: NASAexplorer
Propane also exists on Titan, which is a common fuel used in large quantities here on Earth. But, with an average temperature of -290 degrees F, it is very unlikely life could ever take hold there because that is too cold for liquid water to exist, but the organic nature of some of the chemicals found in Titan’s atmosphere might indicate that this planet-like moon could harbor some form of life. Researchers believe it actually rains methane and other gasoline-like liquids on Titan, and standing on Titan’s surface would feel much like the bottom of a swimming pool due to the fact that it’s atmospheric pressure is about 60 percent greater than Earth’s.
“With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system,” said Ralph Lorenz, Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md. “The combination of an organic-rich environment and liquid water is very appealing to astrobiologists.”
Titan remains the only outer Solar System world where mankind has actually landed a spacecraft, the Huygens lander, which flew to Saturn with Cassini before making its suicidal dive through Titan’s atmosphere on Jan. 14, 2005. The fully instrumented robotic laboratory, courtesy of the European Space Agency, captured images all the way through its descent to the surface, landing on a shoreline by parachute and sending science data back to Earth for 90 minutes before running out of power.
“The discoveries made by Cassini have revolutionized our understanding of Titan,” said JPL scientist Christophe Sotin, who has been analyzing Cassini measurements of Titan’s lakes and seas. “They open new avenues for seeking habitable worlds around exoplanets. They also trigger new questions about the exchange processes between the interior and the atmosphere—and about the composition of these organic particles—that only future missions to Titan will be able to answer.”
Cassini, which launched from Cape Canaveral Air Force Station atop a Titan-IV rocket in October 1997, is still running strong. The spacecraft took seven years to reach Saturn’s system and is expected to continue exploring Saturn and its moons until at least 2017. The mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency.