After overcoming the sand dune, Curiosity came to a new type surfaces that turned out to be much more comfortable for movement than previous stones. Besides fine gravel and sand, on which it is so convenient to ride, a new plain gave a new riddle: strips of unusually smooth sand, free of stones. 
Photos from open sources The size is larger. More here. On the desktop: one, two. Someone immediately wanted to see in traces similar to those left by “stray stones” in the Valley Deaths in the USA: 
Photos from open sources True difference can be seen right away – on Mars there are no stones that could leave such traces. Yes and the scales are different. The width of the stripes found by Curiosity does not exceed 10-15 cm. These “traces” interested NASA scientists themselves, therefore they tried to consider them in more detail. They produced additional shooting, allowing to consider the bands in detail: 
Photos from open sources Even larger (10 mb). Seen that they filled only with a fine fraction of sand and fine gravel, the size of less than 1 cm across. Some internet users pay attention to the fact that along the edges of these “tracks” you can see a cluster of large stones, as if something had parted them. Let’s try still figure out what’s in front of us. Most likely these are cracks, falling asleep later under the influence of wind. On some pictures you can see how cracks in the underlying geological layer turn in the “footprints”, being buried under loose soil: 
Photos from open sources “Spread Stones” in many cases may be just an illusion, due to the observed difference between empty stripes and scattered gravel nearby. However, all maybe harder. Fractured formations that are observed in this area, in fact – the bottom of the ancient Martian lake. Similar deposits were previously studied by the rover Opportunity, and he determined that the water in these lakes was saturated with sulfur compounds and was characterized by high acidity. Drying out of these ponds led to the deposition of salts. In that case, we can observe remnants of salt lakes, which are similar to those on Earth: 
Photos from open sources 
Photos from open sources In this case, salt crystals, protruding from the cracks could really push the stones away cracks. The fact that now we do not see the salt itself may be explained by erosion, which led to the destruction of crystals. TO For example, the same Opportunity found voids that were left in rock crystals of sulfate salts: 
Photo from open sources According to scientists, the disappearance crystals were caused by erosion or exposure to water, with low salt content. Both are possible in Gale Crater, where Curiosity works. Signs were also detected from the satellite powerful flow of water from the mountains to the late geological a period is one after which new layers no longer appear: 
Photo from open sources In the place where it is now Curiosity the intensity of this flow has already dried up. But probably it was this village that brought small rounded pebbles to this area, which NASA recorded in one of the most important open rover. Pebbles proved the existence of water flows in the past on Mars, acting for a long time, and allowing to roll stones.
Water Stones Mars NASA Mars Rover Curiosity
