Brent, that picture is gorgeous.  Far, far better than the Canyonlands "official" photo.  They should replace their brochure photo with yours.  Your photo shows what Shoemaker is talking about in his 1998 paper, at least from the air . After posting, my subconscious continued to work on the question of why so many impact craters back east and not in the west.  Then there was a "duh" moment.  The answer to the question is geological, at least in part.  Roger and/or Don can respond on this.