Sand dunes serve as 'windsocks' on distant planets


Telling what the weather is like on distant planets might be possible, if they're covered in sand dunes. A four-year experiment has revealed how prevailing winds create sand dunes on Earth. The data could enable astronomers to determine weather patterns on other worlds by monitoring wind-formed sand dunes on the surface.


Working in the remote Tengger desert of Inner Mongolia, Clément Narteau of the Global Institute for Physics in Paris, France, and his colleagues used a bulldozer to flatten 160,000 square metres of sand dunes in 2008. Over the next three-and-a-half years, they watched the dunes rebuild and closely tracked the accompanying winds.


"There are very few studies of how sand dunes are initiated and grow," says Nicholas Lancaster of the Desert Research Institute in Reno, Nevada, who was not involved in the research. "This field experiment is unique."


A line in the sand


Narteau found that the newly-created dunes pointed in directions dictated by two prevailing winds, which buffet the desert at different times of the year. The final orientation of each dune was a compromise between the two wind directions, their durations and their relative strengths.


"As the dune is growing, each individual wind contributes to its final shape," says Narteau. "You build up grains perpendicular to each individual wind to build a major structure with an intermediate orientation."


"We've demonstrated that dunes can be used to derive wind orientations and wind strength," says Narteau. He now plans to examine dunes on Mars and Titan, the largest moon of Saturn.


"We don't have weather networks yet on Mars or Titan, so the pattern of sand dunes is one of the best indicators we have of winds," says Ralph Lorenz of Johns Hopkins University in Laurel, Maryland.


Journal reference: Nature Geoscience, DOI: 10.1038/ngeo2047


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