A giant dust storm that now covers nearly the entire southern hemisphere of Mars could permanently jeopardize the future of the Mars Exploration Rovers mission, officials told SPACE.com today.

The new and potentially bleak outlook is a stark shift from the prognosis earlier this week. Further compounding the threat to the rovers, a second large dust storm has recently appeared on the Red Planet.

The first and largest dusty squall has reduced direct sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for the solar-powered rovers. If the storm keeps up and thickens with even more dust, officials fear the rovers' batteries may empty and silence the robotic explorers forever.