For a visual perpective, here's an image of what happened to Mars over the last two weeks:
The dusty squall has reduced direct sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for the solar-powered robotic explorers. If the storm keeps up and thickens with even more dust, officials fear the rovers' batteries may empty and silence the robotic explorers forever.
A dust storm caught by amateur astronomer Paul Maxso of Phoenix, Arizona. On June 23 (top), the storm appears as a bright red blemish on the visible light "RGB" image, just northeast of the planet's center. On June 26, 2007, the storm has more than quadrupled in size and is a large blotch occupying the northeastern region of Mars on the "RGB" image. Credit: Paul Maxson
This may prove the end of one of our most beloved robots in history. However, even if it happens, we shouldn't be in despair. Those rovers have defeated all odds and long outlived their warranty. For those who remember, they were officially only supposed to live 90 days. Right now they've past the two year mark. That's a GOOD DEAL, and they've gotten more science done than thought possible. They've really exceeded what was needed of them, and that's something we should celebrate. Don't get me wrong, I hope they make it through and do another year of science, but we shouldn't be depressed if they don't. Ok, I'll stop getting all mushy.