Mars has never been easy on the robots we have the temerity to send there. The temperatures occasionally rise above zero, but mostly it’s frigid. The atmosphere, mostly carbon dioxide, is one percent as thick as ours. And the dust–there is a raging dust storm over much of the Martian surface now, and for the two Mars rovers, Spirit and Opportunity, it’s getting dangerous. The image above is a composite of pictures from Opportunity, shot over the last month. click HERE to get a larger version. You’re looking at the same slit of the horizon, shot at the same time of day, as the dust gets thicker and thicker. NASA’s posted more information HERE. There are also images from Mars Reconnaissance Orbiter, which is mapping the planet from above. They show much the planet consumed by the storm. Take a look HERE. The dust does two worrisome things for the rovers, especially Opportunity: –It gets into every little nook and cranny it can, though the rovers are well-sealed. –More troublesome is that it’s blocked 99 percent of the direct sunlight reaching Opportunity’s solar panels. The panels had been producing 700 watt hours of electricity per day; on Wednesday they only generated 128. To save power, engineers on earth ordered both rovers to stop driving and running their scientific experiments. Our staff here did a very nice slide show on the plans to send Opportunity into a steep crater called Victoria–you can find it HERE–but that’s on hold for now. Even so, Opportunity was using more power than it took in from the sun, draining its batteries. So the engineers have taken one more step–they’ve ordered the rover to stop talking to them for a couple of days. This is the first time, since the rovers arrived on Mars in January 2004, that one of them hasn’t been heard from daily. "We’re rooting for our rovers to survive these storms, but they were never designed for conditions this intense," says Alan Stern, associate administrator of NASA’s Science Mission Directorate, in a statement. NASA thinks–thinks–the dust is clearing slightly around Opportunity. With luck, it will survive to explore another day. It was designed for 90; it’s already lasted 1,239.