NEWS FROM TITAN

Understanding the atmosphere

Titan’s atmosphere is an enigma. Ever since its discovery, astronomers have been trying to explain how such a dense atmosphere and surface liquid arose and were preserved for millions of years. “Because Titan is the only moon in our Solar System with a substantial atmosphere, scientists have wondered for a long time what its source was,” says Kelly Miller, a research scientist at the Southwest Research Institute in San Antonio, Texas. “The main theory has been that ammonia ice from comets was converted into nitrogen to form Titan’s atmosphere. While that may still be an important process, it neglects the effects of a very substantial portion of comets: complex organic material.”

Changing seasons

Much like seeing the seasons change from summer to winter on Earth, scientists have spotted signs of changing seasons on Titan using valuable data from NASA’s Cassini spacecraft. Using pictures of the moon’s northern hemisphere, Rajani Dhingra of NASA’s Jet Propulsion Laboratory and her team have seen rainfall at the north pole. The rainfall also provides the first indication of the beginning of a summer season, courtesy of Cassini and its Visual and Infrared Mapping Spectrometer instrument. The spacecraft’s near-infrared capabilities allowed it to peer inside the atmosphere and observe this rainfall. Compared to

Earth’s yearly cycle of four seasons, a season on Titan lasts seven Earth years.

Dust storms sweeping the surface

Cassini spotted giant dust storms sweeping across Titan’s surface, with astronomers trying to work out what is generating these powerful gusts around the equatorial region. In the same way the weather changes with the seasons on Earth, a similar phenomenon occurs on Titan. In this case, when the Sun crosses Titan’s equator, massive clouds are formed in these tropical regions, creating powerful methane storms. After more modelling scientists discovered that these are actually clouds of organic molecules raised from the dune – the first observation of a dust storm on Titan.