Dunes on the surface of Titan, Saturn’s largest moon, formed in higher wind speeds and over longer timescales than previously thought.
The findings, presented in two independent studies published in the journals Nature and Nature Geoscience, offer new insights into the processes which shape sand dunes and may provide clues about dune formation on other planets and moons.
The dune formations on Titan are thought to be similar to those found on Earth, Mars and Venus.
Modelling studies have been performed to determine the conditions on Titan but it is unclear how accurate these are.
Wind tunnel experiments designed to simulate surface conditions on Titan, reported by Devon Burr of the University of Tennessee-Knoxville and colleagues in the journal Nature, indicate that threshold wind speeds required to move sand for dune formation are around 40% higher than predicted by current models.
These results lend support to the idea that only rare strong westerly winds control dune movement, rather than the easterly winds that are thought to be most common on Titan.
A second study by Ryan Ewing of Texas A&M University and colleagues, in Nature Geoscience, analyses images of Titan’s dunes taken by NASA’s Cassini spacecraft.
The results imply that long-term climate cycles associated with variations in Saturn’s orbit control the sand-dune patterns on Titan.
The authors estimate that the observed reorientation of some dune crests would have taken around 3,000 Saturn years (about 88,000 Earth years) or longer.
This timescale exceeds that of diurnal, seasonal, or tidal wind cycles, which have previously been suggested to be drivers of these patterns, and suggests that Titan’s dunes — like large dune fields on Earth — are shaped by long-term climate cycles.
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