https://phys.org/news/2018-07-image-spiders-mars.html > Over time the trapped carbon dioxide gas builds in pressure and is eventually strong enough to break through the ice as a jet that erupts dust. The gas is released into the atmosphere and darker dust may be deposited around the vent or transported by winds to produce streaks. The loss of the sublimated carbon dioxide leaves behind these spider-like features etched into the surface. Explore further: Image: Frosted dunes on Mars > Provided by: NASA