This story was updated at 5:00 p.m. EST
After six weeks of waiting out globe-engulfing dust storms, NASA's Mars Exploration Rovers have resumed driving across the planet's surface.
With the improved energy supplies, mission managers said Spirit and Opportunity are back on schedule to do science. During the storm, both rovers stood still and cut back normal communication to conserve energy.
"Weather and power conditions continue to improve, although very slowly for both rovers," said John Callas, project manager for the mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Despite the energetic progress, the rovers aren't out of danger yet. Dust that was lifted into the air "could take months" to clear, said rover Project Scientist Bruce Banerdt. "There is a lot of very fine material suspended high in the atmosphere," Banerdt said, noting that the dust is accumulating on the rovers' energy-gathering solar panels.
Rover panoramic camera scientists said that the sun was nearly blotted out during the peak of the dust storm, as shown in an image released today. Although 99 percent of direct sunlight never made it to the rovers' solar panels, indirect sunlight glowing through the dust charged the rovers' batteries enough to warm and protect delicate circuits from snapping.
Now that the storm is clearing, rover scientists are eager to roll Opportunity inside the 2,400-foot-wide (730-meter-wide) Victoria Crater and scope out its inner slope.
"This is a magnificent crater with a lot of exposed bedrocks and walls showing geologic detail with extensive layering that makes the team geologist very happy," said Thanasis Economou, a senior scientist at Chicago's Enrico Fermi Institute. "What you can see is amazing."
Opportunity's descent was delayed when the dust storms began in mid-June. Mission managers, however, are still deciding when to continue the much-anticipated crater dive.
Meanwhile, Spirit's microscopic imager has been sprayed with dust from the storm to slightly reduce its image quality. The team is experimenting with ways to try dislodging dust on the lens and is planning to drive the rover onto a platform informally named "Home Plate."
Both rovers will start a new atmosphere-monitoring project using their Alpha Particle X-ray Spectrometer (APXS) instruments, which engineers initially designed to examine rocks and boulders on the surface. The APXS instruments will measure argon, which the orbiting Mars Odyssey spacecraft discovered is responsible for mixing the thin martian air between summer and winter.
Scientists hope the rover's finer measurements from the ground will reveal some climatological secrets of Mars.
"It gives you a way of inferring aspects of the Martian circulation that you can't observe at all with any other instrument that's out there," said Ray Pierrehumbert, a planetary geophysicist at the University of Chicago in Illinois.
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