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Cassini searches for elusive clouds on Titan

Morgan Rehnberg, Correspondent
Sep 4, 2015, 14:48 UTC

Sen—How much do you trust the weather forecast? While it might seem straightforward, predicting when it will rain and whether it will be cloudy is one of the most challenging tasks in science. Now imagine doing it from more than a billion kilometers away. That is the challenge Cassini worked to advance with observations this week when it turned its cameras towards Saturn’s giant moon Titan.

NASA's Cassini has been studying this hazy world up close for 11 years; Earth-based observations have been monitoring it for decades.

Aside from Earth, Titan may well be the most fascinating object in the Solar System. Second in size among moons only to Jupiter’s Ganymede, Titan possesses a thick atmosphere and a liquid-covered surface. This combination, unique for a moon, means that Titan has weather much like the Earth.

Just like our planet, Titan’s atmosphere is dominated by nitrogen, but instead of oxygen filling out the rest, the remainder is primarily comprised of methane. This gas gives it a famously hazy appearance. Unlike the Earth, however, clouds are rare on this world. At any given time, clouds can be seen covering only around two per cent of the moon’s surface.

Occasionally, though, an enormous outburst of clouds can be observed. Some astronomers believe that the location of these outbursts may be tied to Titan’s seasons. In 2004, a huge formation occurred near the moon’s south pole during southern summer.

Now that summer on Titan has moved to the northern hemisphere, Cassini has been keeping an eye out for new cloud formations. None has been observed at lower latitudes for more than three years.

The Cassini-Huygens mission is a collaborative effort between NASA, ESA, and the Italian Space Agency. Launched in 1997, it reached Saturn in 2004 and has since been studying the planet, its moons, and its rings. In 2005, the Huygens probe made the first landing on Titan, Saturn’s largest moon. After completing its second mission extension in 2017, Cassini will make a series of close passes to the planet and then end its time at Saturn by plunging into the planet’s atmosphere.