A new paper using data from NASA's Cassini probe has described in detail how aerosols begin to form in the highest part of the atmosphere of Saturn's moon Titan. The research, say scientists, could help predict how "smoggy aerosol layers" behave on Earth.
The study, published this week in the journal Proceedings of the National Academy of Sciences, states that the smog on Titan begins to form when solar radiation excites nitrogen and methane molecules in the ionosphere, creating a "soup" of negative and positive ions. Collisions among these molecules allows them to grow into more complex aerosols, which coagulate when they reach a lower part of the atmosphere. Eventually the molecules produce the hydrocarbon rain that famously creates the lakes seen on Titan's surface.
The researchers, based at the University of Reims, looked at data from three different Cassini instruments during the study. Data from Cassini's plasma spectrometer, its ion and neutral mass spectrometer, and its radio and plasma wave science experiment were examined and compared to data from the Huygens probe, which descended to the surface of Titan in 2005.
Titan is the only other object in the soar system known to have stable liquid on its surface. In December of 2012 the ESA released a high-definition photo of a river valley that runs for over 400 km (248 miles) on the surface of Titan. The picture above shows a flash of sunlight that is reflected off a lake on Titan. The phenomenon is known as a specular reflection.