A high-altitude cloud on Saturn's moon Titan has been determined to contain methane ice, according to NASA.
NASA's Cassini spacecraft spotted the condensation over the moon's north pole eight years ago, but researchers have just determined that the cloud is made of methane ice, which is denser than ethane ice, which was previously believed to make up the cloud. The stratospheric cloud over Titan's north pole is similar to the clouds found over Earth's north pole.
"The idea that methane clouds could form this high on Titan is completely new," Carrie Anderson, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and lead author of the study, told NASA. "Nobody considered that possible before."
Scientists already knew that methane clouds were found in Titan's troposphere (the lowest layer of the atmosphere). The lower methane clouds work like rain clouds on Earth, using evaporation and condensation, only on Titan, the vapor is methane instead of water, according to NASA.
Stratospheric clouds don't typically develop until the temperature dips below minus 108 Fahrenheit (minus 78 degrees Celcius), according to NASA. Titan's stratosphere south of the moon's equator usually keeps a temperature of minus 333 degrees Fahrenheit (minus 203 degrees Celcius), which is not cold enough for methane to freeze, but the study noted that Titan's stratospheric temperature is colder closer to the poles.
Eleven degrees Fahrenheit (6 degrees Celsius) is all it takes for a methane ice cloud to form.
"Cassini has been steadily gathering evidence of this global circulation pattern, and the identification of this new methane cloud is another strong indicator that the process works the way we think it does," Michael Flasar, Goddard scientist and principal investigator for Cassini's Composite Infrared Spectrometer, told NASA.
"Titan continues to amaze with natural processes similar to those on the Earth, yet involving materials different from our familiar water," Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, told NASA. "As we approach southern winter solstice on Titan, we will further explore how these cloud formation processes might vary with season."
