The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind^{1, 2, 3}. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model^{4, 5} for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s^-1, most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.

1. Department of Astronomy/CRSR, Cornell University, Ithaca, New York 14853, USA
2. Geological Sciences, University of Nevada, Reno, Reno, Nevada 89557, USA
3. Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4. Jet Propulsion Laboratory, Pasadena, California 90119, USA
5. Department of Geological Sciences, Arizona State University, Tempe, Arizona 85287-1404, USA
6. US Geological Survey, Flagstaff, Arizona 86001, USA
7. Malin Space Science Systems, San Diego, California 92191, USA
8. NASA Johnson Space Center, Houston, Texas 77058, USA
9. Planetary Science Institute, Tucson, Arizona 85719, USA

Correspondence to: R. Sullivan¹ Correspondence and requests for materials should be addressed to R.S. (Email: rjs33@cornell.edu).

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