Saturn's moon Titan is one of the most bizarre places in the solar system, and now, to make things even weirder, scientists have found traces of propylene, the chemical used to make Tupperware, floating in its thick orange atmosphere.
Bigger than Mercury, Titan is an icy world where temperatures hover around 228 degrees below zero Fahrenheit. It is the only moon in our solar system with clouds, and it has weather like we have on Earth. But when it rains on Titan, it rains liquid methane.
Titan is also the only moon in our solar system with lakes and rivers, but they are filled with liquid methane and ethene, rather than water.
"Methane takes the same role as water on Titan," explained Conor Nixon, a planetary scientist at NASA's Goddard Space Flight Center. "It evaporates on the surface and then rains back down."
The discovery of propylene in this mysterious world's smoggy atmosphere is more satisfying than surprising, Nixon said. Ever since Voyager 1 gave researchers their first close-up look at Titan's atmosphere in 1980, they have been expecting to find it.
Propylene is a three-carbon gas like propane and propyne. More than 30 years ago, Voyager's instruments detected both propane (like what we use in a camper stove) and propyne in the planet's atmosphere, but not propylene.
"We were kind of sure it had to be there at some level," said Nixon. "It just doesn't make sense to have propyne and propane and not propylene."
To find the elusive gas, Nixon used data collected by the Cassini spacecraft's Composite Infrared Spectrometer. The instrument, one of 12 aboard Cassini, measures the spectral signature of heat coming off planets and other bodies in the solar system.
"Each molecule has its unique fingerprint -- it's own way of vibrating that gives off a particular color of heat," he said.
The propylene fingerprint was hard to find because its heat signature was very similar to that of another molecule, and also, there isn't much of it in the atmosphere, Nixon said.
But now that we know for certain it is there, the next step is to find out how much of it is there and where the concentrations are the highest, said Nixon.
Nixon's research is published in the Sept. 30 edition of the Astrophysical Journal letters.
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