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Sand dune patterns on Titan controlled by long-term climate cycles

Nature Geoscience volume 8, pages 15–19 (2015)Cite this article

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Abstract

Linear sand dunes cover the equatorial latitudes of Saturn’s moon Titan and are shaped by global wind patterns1,2,3. These dunes are thought to reflect present-day diurnal, tidal and seasonal winds1,3,4,5,6, but climate models have failed to reproduce observed dune morphologies with these wind patterns4,6. Dunes diagnostic of a specific wind7,8 or formative timescale9,10,11 have remained elusive3,5,12. Here we analyse radar imagery from NASA’s Cassini spacecraft and identify barchan, star and reoriented dunes in sediment-limited regions of Titan’s equatorial dune fields that diverge by 23° on average from the orientation of linear dunes. These morphologies imply shifts in wind direction and sediment availability. Using a numerical model, we estimate that the observed reorientation of dune crests to a change in wind direction would have taken around 3,000 Saturn years (1 Saturn year ~ 29.4 Earth years) or longer—a timescale that exceeds diurnal, seasonal or tidal cycles. We propose that shifts in winds and sediment availability are the product of long-term climate cycles associated with variations in Saturn’s orbit. Orbitally controlled landscape evolution—also proposed to explain the distribution of Titan’s polar lakes13—implies a dune-forming climate on equatorial Titan that is analogous to Earth.

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Figure 1: Comparison of sand dune patterns in the solar system.
Figure 2: Despeckled Cassini radar images of barchan, star and reoriented dunes.
Figure 3: Modelled dune reorientation timescales of Titan’s dunes.

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Acknowledgements

Comments from C. Newman and T. Farr greatly improved our manuscript. This research was supported by NASA through the Cassini Data Analysis Program by grant NNX14AD52G to R.C.E. and A.G.H. A.L. thanks the French Space Agency (CNES) for its support. We thank C. McCormick, D. Parker and S. Troy at the University of Alabama and C. Ballard from University of California at Berkeley for assistance with mapping.

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Authors and Affiliations

  1. Department of Geology and Geophysics, Texas A&M University, College Station, Texas 77843, USA

    Ryan C. Ewing

  2. Department of Astronomy, Cornell University, Ithaca, New York 14853, USA

    Alex G. Hayes

  3. Laboratoire AIM, Université Paris-Diderot CEA-SACLAY, 91191 Gif sur Yvette, France

    Antoine Lucas

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  1. Ryan C. Ewing
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  2. Alex G. Hayes
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  3. Antoine Lucas
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Contributions

R.C.E. and A.G.H. contributed to the design, research, analysis and writing of the study. A.L. contributed the de-noised Titan data and manuscript editing.

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Correspondence to Ryan C. Ewing.

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The authors declare no competing financial interests.

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Ewing, R., Hayes, A. & Lucas, A. Sand dune patterns on Titan controlled by long-term climate cycles. Nature Geosci 8, 15–19 (2015). https://doi.org/10.1038/ngeo2323

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