NASA's Cassini spacecraft has revealed the presence of an enormous cloud located around the Saturnian moon Titan's southern polar region. The discovery comes as the spacecraft nears the end of its mission, which has stretch over a decade-long mission, and characterizes the ringed giant and its moons in spectacular fashion.
Titan's winter season lasts for an impressive seven and a half Earth-years. This has allowed Cassini to observe the slow passing of the enigmatic moon periodically since arriving around Saturn in June 2004
The cloud seen shrouding the southern extremes of the enigmatic moon was created through a process unlike anything that occurs here on Earth. On our planet, rain clouds are created when water vapour rising through Earth's atmosphere rises to an altitude with the correct temperature and pressure to induce condensation.
Whilst some clouds are created through a similar process in Titan's atmosphere, the polar cloud is believed to have developed via a different method. A smog-like, icy cloud of gasses most likely comprised of hydrocarbons and nitrates, which was transferred from the warmer northern hemisphere to the colder south falls through Titan's atmosphere.
As the gasses descend, they gradually condense to form the highly layered cloud located in a stable atmospheric region in the planet's low-mid stratosphere, which is observable by Cassini's Composite Infrared Spectrometer.
By analyzing Cassini data, NASA scientists are able to deduce the severity of the weather the moon's winter. It is estimated that temperatures at Titan's south pole could dip beneath -238 ºF (-150 ºC).
"The opportunity to see the early stages of winter on Titan is very exciting," states Robert Samuelson, a researcher at NASA's Goddard Space Flight Center, Greenbelt, Maryland. "Everything we are finding at the south pole tells us that the onset of southern winter is much more severe than the late stages of Titan's northern winter."
Moving forward, the Cassini spacecraft will continue to make periodic observations of Titan's atmosphere prior to the termination of its solstice mission in 2017.