Puzzling Photographs from Mars Need Explanation!

NASA has released recent photographs taken by the Mars Rover Spirit, after it had climbed out of the crater in which it had landed and took panoramic pictures from the crater’s top.  The photographs captured, according to JPL/NASA, a “dust devil” in the distance (about 2 miles away).

But as one looks closely at the photographs – there are many of them – one notices incredible features:  What looks like a long sandcovered wall, a black stone ring, a sandblown conical structure & rectangular areas marked off by stone boundaries…

Enlargements of the photos on the JPL/NASA website by Erik Poltorak, our webmaster, only enhance the puzzle.  An explanation by the rover mission scientists would be most welcome.

Spirit Navigation Camera Sol 581
Click to Enlarge - Navigation Camera Sol 581 Panoramic Camera Sol 581
Click to Enlarge - Naviagtion Camera Sol 581

NASA site of Original Images