re: Nukes on Mars
They might be able to inwardly retract the outer solar panels so that gravity (even that bit of Martian gravity) could do the work of releasing some the Martian dust down to the surface. They wouldn't even have to retract them inward all the way, thus protecting the inside panel. Love that Mars Sun Dial "They will use the colored blocks in the corners of the sundial to calibrate the color in images of the martian landscape".
If Pu238/equiv. was used in Apollo, I don't see why they didn't use it in the case of the MERs.