One of the most interesting things about Saturn's largest moon Titan is the array of dunes that adorns its surface. Given that there's sand and dunes, it stands to reason that the structures were produced by winds blowing in a certain direction. When the first atmospheric models of the celestial body were created, researchers determined that the winds most likely blow from east to west. But observations of the dunes themselves point to a totally different conclusion – the predominant wind patterns are oriented west to east. Researchers are now looking to clear up this contradiction.

The first models seeking to explain how the moon's atmosphere behaved were derived from data sent back by the European Space Agency (ESA) Huygens lander. This was a component of the Cassini mission to Saturn, which took off in 1997, and reached the gas giant on July 1, 2004. The small lander parachuted itself on Titan, collecting readings from the atmosphere as it headed for the surface. Additionally, basic principles of planetary sciences, including those describing the rotation of planetary atmospheres, agreed with the Huygens readings.

When the simulations were first presented, they made perfect theoretical sense. But when Cassini began relaying back data from direct observations of Titan's surface, image the experts' surprise when learning that the dunes were actually oriented the other way around. Explaining this paradox is the goal of a new research paper published in the esteemed journal Aeolian Research by expert Tetsuya Tokano, who is based in Germany, at the University of Cologne, experts at the JPL report. The main conclusion of the report is that the winds suffer seasonal variations, in which their regular direction changes by 180 degrees. These uncommon winds are also a lot stronger than the usual ones, Tokano adds.

“It was hard to believe that there would be permanent west-to-east winds, as suggested by the dune appearance. The dramatic, monsoon-type wind reversal around equinox turns out to be the key,” Tokano explains. “This is a subtle discovery – only by delving into the statistics of the winds in the model could this rather distressing paradox be resolved. This work is also reassuring for preparations for proposed future missions to Titan, in that we can become more confident in predicting the winds which can affect the delivery accuracy of landers, or the drift of balloons,” explains Cassini radar scientist Ralph Lorenz. He holds an appointment at the Lauyrel, Maryland-based Johns Hopkins University Applied Physics Laboratory.