As Curiosity continues on her journey up Mount Sharp (the mound in the centre of Gale crater), rocks we encounter contain evidence for changing environmental conditions. The fine-grained mudstones of the Murray formation show us that lakes were present in the past, whilst the sandstones of the Stimson formation are evidence for ancient dune fields.
During 2015-2017, we crossed the Bagnold dune field, a 35-km long by 1-2 km wide dune field that wraps around the northwest side of Mount Sharp. This was the first time that scientists have explored an active dune system on another planet. In the Martian fall/winter, we investigated two barchan dunes. Barchan dunes are crescent shaped and are formed by winds blowing in one direction, and when sediment supply is limited. Later on, during the Martian summer, we examined a linear dune. Linear dunes are formed by winds blowing in two directions, with more abundant sediment supply, and can be very long (on Earth, they can reach 160 miles in length e.g., Namib Sand Sea, Namibia)… [More at link]