Fuzzy time tables

Earlier this year, the Spirit and Opportunity rovers, which are still sending images back from Mars, celebrated their sixth anniversary on the red planet.

The mission was slated to last only three months.

In 1997 the Mars Pathfinder mission lasted more than three months when it was originally expected to cease functioning in a week to a month.

Am I the only one who suspects that these extended mission times have more to do with NASA's inability to calculate the expiration date of their...