NASA Has Just Released Breathtaking New Photos of Mars And They Are Marvellous

On Earth, Bourke had done previous studies of dunes in the Namib Desert near Walvis Bay, Namibia and noted arctuate striations — crusty arcs of sand cemented by water and minerals — on the surfaces of migrating sand dunes using photos taken by satellite. She subsequently assembled a team to check them out on the ground and discovered that the striations resulted when dune materials had been chemically cemented by salts left behind by evaporating groundwater. On Earth, desert dune fields are periodically flooded by water in areas of fluctuating groundwater, and where lakes, rivers and coasts are found in proximity, said Bourke. These periodic floods leave tell-tale patterns behind them. Once the material had been cemented, it hardens and remains behind as the dunes continue to migrate downwind.