The international Cassini mission has revealed a giant cloud of toxic gas over the south pole of Saturn's moon Titan.
Following a detailed analysis the researchers determined the cloud was made up of particles of highly toxic hydrogen cyanide, the European Space Agency (ESA) reported. Titan is almost 10 times farther from its host star than Earth is from the Sun. Its extremely cold weather causes methane and other hydrocarbons to rain onto its surface and form rivers and lakes.
"The discovery suggests that the atmosphere of Titan's southern hemisphere is cooling much faster than we expected," said Remco de Kok of Leiden Observatory and SRON Netherlands Institute for Space Research, lead author of the study published in the journal Nature.
Titan has a nitrogen-based atmosphere containing trace amounts of methane and other gases. The moon experiences seven-year-long seasons throughout its 29-year orbit, in 2009 summer transitioned into autumn on the chilly moon.
In May 2012 Cassini images revealed a giant swirling cloud on the moon's south pole. The cloud was puzzling because researchers had previously believed clouds could not form at that altitude (close to 200 miles above the surface) because of the extremely cold air. The "polar vortex" is believed to be a result of the changing seasons, as large amounts of air are warmed by the Sun and pushed southwards.
Upon further examination the researchers found clues about the object's composition in reflected sunlight. The Visual and Infrared Mapping Spectrometer on Cassini allowed the team to look at the light spectrum and map out the distribution of chemical compounds in the atmosphere and on the moon's surface.
"The light coming from the polar vortex showed a remarkable difference with respect to other portions of Titan's atmosphere," de Kok said. "We could clearly see a signature of frozen hydrogen cyanide molecules."
The findings were published in a recent edition of the journal Nature.
