Re:Unrelated Question (Score 4, Insightful)

The answer is that "designed to last for 3 months or until its solar panels become covered in Mars dust..." is inaccurate. Dust is one of the limiting factors to the Spirit and Opportunity's lifespans, but it is not the only one. The electronics and batteries have a restricted lifespan due to the significant temperature changes that occur from day to night. Imagine putting a solar powered calculator in the oven and then the feezer over and over again. The rovers were designed to last at least 90 days and dust will not be a significantly limiting factor during those 90 days. If the electronics and batteries last significantly longer than 90 days, then dust may start to become a larger problem. Assuming the electronics/batteries last indefinately, the dust will eventually kill the Rovers. When NASA launches a rover designed to have a significantly longer lifespan, you can bet that solar panel cleaners will be part of the design.