Bad batteries killed Mars Pathfinder
There was a SNAFU with the type of battery selected for Mars Pathfinder. Mars Pathfinder died suddenly because its batteries crapped out. It believe(?) with MER they over compensated for this earlier error by selecting extra reliable batteries. Tired batteries will
probably kill the MERs assuming they don't fall off a cliff or down a hole. Let's hope it's a long time before that happens.
Gary