Real reason.
They need the extra time to fit the frikkin' laser beams to it.
NASA will delay the launch of its nuclear-powered robotic tank to the surface of Mars by two years because of unresolved technical issues. The space agency is now aiming for a 2011 lift-off date for the Mars Science Laboratory. The delay will add $400m to the already over-budgeted Mars rover and likely force NASA to delay …
As TeeCee hints, MSL does indeed carry a laser, designed to ablate the outer coating of rocks and allow spectrographic analyses to determine whether it is, in fact, rock or compressed shoes.
http://www.youtube.com/watch?v=fEZ5dEi4oPo
The scariest thing about the whole MSL project is the Skycrane EDL system. There are nice CG of the incredibly complicated process needed to soft land a vehicle of MSL's (high) mass onto the surface. (Airbags and chutes, as used by the MER rovers, are out because the mass is too high and the atmosphere's too thin for the chutes to slow the backshell enough.)
http://uk.youtube.com/watch?v=noy8o0lN1fE
I must say this scares the crap out of me. If it lithobrakes, that may well be it for Mars surface operations for the next 10-15 years. (The putative ESA rover project has been delayed 6 years already and may well get defunded long before flight hardware gets hammered on.)
Nasa is history, they continually cover up information. NASA is DOD. Our money (I'm a yank) is being horrendously mis-spent. If you look closely at NASA's information stream, it becomes clear
that they ain't shooting straight. Mars is awash with life right now. Geysers shoot water into the air, the greenish band on mars advances and recedes seasonally, and the sky on the planet is blue, not red. If you want the very best photo of the Moon, don't look for it from NASA, it is from private astronomers, the real future of exploration and discovery is not going to be NASA unless we see huge changes in the structuring at the top of the pyramid. Presently not enough people know or care that NASA is not at all what it appears. N ever A S traight A nser is really true unfortunately.
-Bryan