Very nicely written article about an extremely interesting subject. It will be very interesting to see what the rover is able to find after it is landed.
Also, this brings up another interesting question. Since the targeting was designed to preclude the upper stage, that had not been cleaned, from hitting Mars, what will it hit eventually? Will it be pulled into the sun, or another planet or.... There is a lot of space out there but also a lot of objects in it and sooner or later it will likely be captured by gravitational pull from something.