re: ESA should just buy and fly an MER...
To echo Gary's pet peeve, why not use a proven design? Just buy an MER and fly it on a Soyuz. Hmm, if they insist on using different instrucments -- which does have scientific justification -- I wonder how much easier it'd be to put different stuff on an MER platform than to build from scratch?
Of course, the not-invented-here syndrome is easy compared to the not-invented-in-this-country syndrome...