Long sand dunes that ripple across Saturn’s moon Titan may have been there for thousands of years, results from NASA’s Cassini spacecraft suggest.
Scientists have had a harder time pinning down the factors that shape Titan’s dunes. These are made of hydrocarbon particles — so they are more similar to mounds of soot than to Earth’s sand, which is mostly silica — and are some of the biggest in the Solar System. They stretch for hundreds of kilometres over a total area as big as the United States (including Alaska). Various ideas for what shaped them include winds from the east or the west, which may be driven by daily, seasonal or other regular changes. Dunes can even assume different forms depending on how much sediment is available to feed them2.
Ewing’s team analysed about 10,000 dune crest lines mapped by a radar instrument aboard Cassini, which has been orbiting Saturn since 2004. They used an algorithm that enabled them to extract finer detail from the images than ever before. This sharper view allowed them to see features down to about 1 kilometre across — including, for the first time, star-shaped dunes where three or more crest lines intersect.