Former NASA astronaut Jack Fischer captured this photograph of Lagoa dos Barros and crescent-shaped barchan dunes on the Atlantic coastline of southern Brazil on July 9, 2017, while aboard the International Space Station.
Barchan dunes are sand dunes that form in areas with one wind direction and little vegetation. In this case, fierce winds from the Western Atlantic sculpt the sand along the coast into distinctive crescent shapes. The tips of barchan dunes point downwind, showing the prevailing wind direction. These fragile formations act as barriers keeping the wind and waves from penetrating inland, blunting the effect of storms and minimizing coastal erosion.
Image Credit: NASA/Jack Fischer