Dunes on Titan reveal clues about ancient climate

Nature : The Cassini spacecraft orbiting Saturn’s moon Titan has provided the clearest radar images of the moon’s dune-covered surface. The images show that Titan’s winds may change direction as a result of the moon’s wobbles. Unlike Earth’s dunes, which are made of silica-based sand, Titan’s dunes are more like mounds of soot and are among the largest in the solar system. Ryan Ewing of Texas A&M University and his colleagues examined 10 000 dune crest lines after improving the resolution of the Cassini images. The clearer images revealed the presence of shapes where three or more crest lines intersected, a sign that prevailing winds are blowing from multiple directions. The star-shaped dunes are also aligned differently from the long, linear dunes. Ewing’s team calculated that it would take several thousand years for Titan’s winds to shift to produce the star dunes. A separate study revealed that stronger-than-expected winds would have been required as well. That combination of information will be useful in reconstructing Titan’s historical climate.