Washington: A new study has found that following the dramatic cooling off of the atmosphere, there is a huge toxic cloud which is floating over Titan, the south pole of Saturn's largest moon.
Scientists analysing data from the international Cassini mission found that this giant polar vortex contained frozen particles of the toxic compound hydrogen cyanide.
Lead author Remco de Kok said that the discovery suggested that the atmosphere of Titan's southern hemisphere was cooling much faster than expected.
Unlike any other moon in the Solar System, Titan has been shrouded by a dense atmosphere dominated by nitrogen, with small amounts of methane and other trace gases. Almost 10 times further from the Sun than Earth, Titan is very cold, allowing methane and other hydrocarbons to rain onto its surface to form rivers and lakes.
In May 2012, images from Cassini revealed a huge swirling cloud, several hundred kilometers across, taking shape at the South Pole. This polar vortex appeared to be an effect of the change of season, with large amounts of air being heated by sunlight during the northern spring and flowing towards the southern hemisphere.
A puzzling detail about this swirling cloud was its altitude, some 300 km above Titan's surface, where scientists thought it was too warm for clouds to form. They turned to the rich data from Cassini to understand what could give rise to this mysterious cloud.
After careful scrutiny, they found that a spectrum splits the light from a celestial body into its constituent colours, revealing signatures of the elements and molecules that are present. The Visual and Infrared Mapping Spectrometer on Cassini takes spectra at many different points on Titan, mapping the distribution of the chemical compounds in its atmosphere and on its surface.
The study is published in the journal Nature.