I see this effect over and over. And obviously I would think that sculptures would need a type of fabric underlayment if they wanted to have outdoor sculptures, to help in separating the sand from the sculptures etc.
The analysis I use for the photos and imagery are not mean't to be exacting, only to get you closer to understanding that there is intelligent life on mars (martians). Many of the rocks you may think are rocks, are in fact highly designed sculptures, mechanical objects etc.
Nasa is trying to leak out anomalous imagery with out of course talking about it public! Though most images have been doctored, Nasa is trying to humbly and quietly nudge us along with out going too public about it vocally. Though it is work and painstaking effort to find objects in the images that have not been altered in some way!