NASA’s Mars rovers, Opportunity and Spirit, ere affected by a series of Martian summer dust storms. NASA announced that dust storms has blocked 99 percent of direct sunlight to the rover Opportunity and the Spirit is also affected, but to a lesser extent.

The rovers, which rely on solar energy, must remain inactive when dust blocks out the sun.

"We're rooting for our rovers to survive these storms, but they were never designed for conditions this intense," said Alan Stern, associate administrator of NASA's Science Mission Directorate, Washington.

The NASA scientists fears that the dust storms will not stop for several days, maybe even weeks. If the sunlight is further cut back for an extended period, the rovers will not be able to generate enough power to keep themselves warm and operate at all, even in a near-dormant state.

The rovers use electric heaters to keep some of their vital core electronics from becoming too cold.

NASA said that the rovers have been on Mars more than 3 years

"We are taking more aggressive action with both rovers than we needed before," said John Callas, project manager for the twin rovers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

In order to preserve the Opportunity‘s energy, the scientists in the rover team suspended driving and most observations, including use of the robotic arm, cameras and spectrometers to study the site where Opportunity is located.