There's an especially interesting picture in the article:

https://static01.nyt.com/newsgraphics/2016/10/16/exomars-lan...

Obviously anything about Mars is interesting, but this picture has a peculiar property. Look at the picture and imagine that the light is coming from the upper right -- when you do that, the crater becomes a dome. If instead you imagine that the light is coming from the lower left, it becomes a crater again.

I've seen this in other ambiguous terrain photographs, but this picture easily supports the ambiguity.