On Saturn's largest moon, a mystery has unfolded. Large sand dunes stretch across Titan's surface facing East — but the winds above blow in just the opposite direction, West. What's going on here?

The answer, say researchers at the University of Washington, is not in the winds at all: It's in the planet's methane, and the epic storms that it generates. In a new paper published in Nature Geoscience, lead author Benjamin Charnay lays out the results of a climate simulation that's supplied a possible answer to the mystery of the dunes.

Though the moon already has fairly strong winds itself, that scientists originally thought may have been the culprit, the winds that would be generated by these storms are another thing altogether. Not only are they up to 10 times faster and stronger, they also blow in the opposite direction of the normal winds on Titan. They also have another unusual quality — besides being more powerful, they are also rarer, happening approximately every 15 years, when the moon is in equinox.

Though it's a tidy explanation, Charnay says the real test won't come until we can actually see Titan during the equinox — which won't fall until eight years from now.

Image: Titan's surface / ESA/NASA/JPL/University of Arizona