It appears to be (by my calculations) a size 8 NIKE tennis shoe.
I was looking at the new page about water being found on MARS and found the print.
Although its possible that this mark was left by the mars scooper,
it doesnt appear to have the sharp lines produced by the other scoop marks
2 different angles. (just to the right of the obvious"scoop" marks)
It looks almost like a stream of water left an impression stopping at the large rock.
Download the original 11mb file here