They seem to be taking some precautions against contaminating Mars.
"The Mars Science Laboratory Rover will comply with requirements to carry a total of no more than 300,000 bacterial spores on any surface from which the spores could get into the martian environment."
I don't see any reference to spores per unit area. If they are using the value of 300k bacterial spores per square inch, that is a relatively dirty surface. Granted, human skin contains on the order of millions of colony forming units per square inch, so 300,000 might be a reasonable goal, but I would question whether this is per square inch or square centimeter, or on a general surface which might be many square units of surface area.
I just hope we don't seed Mars with terrestrial life and then "discover" it and come to the wrong conclusions. Or kill what life is there by contaminating it. I hope we send a clean spacecraft up.
