Opportunity Showing Signs of Age

It is amazing that the Mars landers that were expected to only last for 90 days on the Red Planet are still trekking along for nearly 4 years. This does not mean that Spirit and Opportunity haven't had a few bumps and bruises along the way, but they have weathered the Martian winters, dust storms, and the occasional equipment breakdown that has occurred. Recently a encoder on Opportunity broke and an attempt to override it resulted in a few bent bristles on a brush. Also dust has started to build up on Opportunity causing temporary blindness. After 4 years the rovers are expected to show some signs of wear and tear, but they are still doing remarkably well and scientists hope that they will continue working and providing data on the Maritain surface for years to come.