re: I still wouldn't send the rover into it.
I know what Lee means. If I was there in a spacesuit, I'd toss a big rock ahead of me before I went down there. If there is still water flowing up through the ground from the deep layers in low areas, I remember what water welling up through round sand grains on Earth produces: quicksand.
Of course, odds heavily favor the same hard-packing dirt we've seen in Opportunity's crater and everywhere else.