After overcoming the sand dune, Curiosity entered a new type of surface that proved to be much more comfortable to move around than the previous rocks. In addition to the fine gravel and sand, which are so comfortable to ride on, the new plain presented a new mystery: strips of unusually flat sand, free of stones.
The size is bigger. On the desktop: one and two.
Someone immediately wanted to see footprints in them, similar to those left by the "wandering stones" in Death Valley in the USA:
True, the difference is immediately visible - there are no stones on Mars that could leave such traces. And the scale is different. The width of the stripes found by Curiosity does not exceed 10-15 cm.
These "traces" interested NASA scientists themselves, so they tried to consider them in more detail. They made an additional survey, allowing you to see the stripes in detail:
Even larger (10 mb).
Promotional video:
It can be seen that they are filled only with a fine fraction of sand and fine gravel, less than 1 cm across. Some Internet users also pay attention to the fact that along the edges of these "tracks" an accumulation of large stones can be seen, as if something had pushed them apart.
Let's try to figure out what is in front of us. Most likely these are cracks that were filled in later by the wind. In some images, you can see how cracks in the underlying geological layer turn into "traces", being buried under loose soil:
"Spread rocks" in many cases can be just an illusion, due to the observed difference between empty lanes and scattered gravel nearby.
However, everything can be more complicated. The cracked strata that are observed in this area are actually the bottom of an ancient Martian lake. Similar deposits were previously studied by the Opportunity rover, and it determined that the water in these lakes was saturated with sulfur compounds and was highly acidic. Drying up of these reservoirs led to the deposition of salts. In this case, we can observe the remnants of salt lakes, which are similar to those on Earth:
In this case, salt crystals protruding from the cracks could really push the stones away from the crack. The fact that now we do not see the actual salt can be explained by erosion, which led to the destruction of the crystals. For example, the same Opportunity found voids that were left in the rock by crystals of sulfate salts:
According to scientists, the disappearance of the crystals was caused by erosion or exposure to water with a low salt content. Both are possible in Gale Crater, where Curiosity operates. Even from the satellite, signs of a powerful flow of water that came from the mountains were identified in the late geological period - one after which new layers did not appear:
In the place where Curiosity is now, the intensity of this flow has already dried up. But, probably, it was this mudflow that brought small rounded pebbles to this area, which NASA recorded in one of the important open rover. Pebbles proved the existence of water streams on Mars in the past, which operated for a long time, and allowed them to dump stones.
