The "Containers" appear to be made by the dead creatures themselves. And stacked into layers with almost endless rows and almost endless "layers". A horrific work ! So much so that it seems it was recorded down through time on mars. And memorials were made of this back breaking process. To view all your creatures dead once you got up from being underground after the dust has settled must of been heart breaking at the very least. That is why I think you see all these creature memorials. Today's generation of martians did not experience it of course. But just like the Viet Nam Memorial where 58,200 veterans lost their lives, we Americans had to make memorials to the dead of that war. So did the martians make memorials to the oceans and seas lost and the creatures in them and so much more!
Don't forget to learn of the "white" layers in the photo below, zoom in and understand how the "white" lined "gestures" work. I call them "action or movement" markers. It is I think the martian way to show what they had to do to clean up their devastated land after being ruined by a calamity that ruined their atmosphere and forced the martians (in my opinion) to go underground! In extreme ancient times!
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!