What are all these gaps / circular structures found on a photo taken by Mars rover Curiosity at Dingo Gap? Have a look at the image I made to see what gaps I mean.
(I know the quick paint job looks terrible)
As you can see on the image I marked the area green where I found all these strange gaps. On the left I placed a zoomed view of the gaps, where I highlighted one.
You can find the original picture on nasa.gov. Here is the accompanying article