Mars Dust Storm Weakens -- But Won't Doom -- Rovers

Victoria Jaggard
National Geographic News
July 6, 2007

A massive dust storm covering about a quarter of Mars's southern hemisphere is "starving" NASA's Mars rovers Spirit and Opportunity, forcing mission managers to put the robots on regular nap-time schedules to save energy.

The storm, which currently covers about 7 million square miles (18 million square kilometers) of the red planet, is blocking sunlight form reaching the solar-powered rovers' light-collecting arrays (see a Mars map).

As the power supply dwindles, NASA scientists are sending commands to shut off the rovers during noncritical hours.

"We only plan to stay up for a short period of time, and then we command the vehicle to go to sleep," said Jacob Matijevic, chief of the rover engineering team, who is based at NASA's Jet Propulsion Laboratory in California.

"Fortunately this [storm] came at a time when it's the summer season in the south of Mars, so we don't need the energy for survival heat."

During southern winter, when temperatures can plummet as low as -125°F (-87°C), a loss of self-generated heat would expose the rover to surface temperatures that would likely cause extensive damage.

Although some experts worry that the continuing storm will eventually drain the rovers and cause a final powering down, Matijevic is confident that the storm will soon pass.

"It's a low-activity period," he told National Geographic News, "but we're not in a position that threatens our survival."

The Coming Storm

When the budding storm was first reported last week, NASA anticipated that it would delay a planned mission to send the rover Opportunity into Mars's enormous Victoria Crater.

Mission leaders had carefully weighed the risks that trip would pose to the aging robot, which was designed to last a mere 90 days but has now been in operation for more than three years.

Over the course of a week and a half the storm escalated, becoming a conglomeration of squalls with fingers reaching as far as the rover Spirit at the Gusev Crater halfway around the planet.

Opportunity, perched on the rim of Victoria Crater, has been under the heaviest part of the storm, and it can only gather enough energy to power the equivalent of three 90-watt light bulbs.

Some experts have speculated that the growing tempest could be the start of one of Mars's global dust storms, which are known to engulf the planet about every six years.

The Mars Viking landers experienced such a storm in 1976, and the last global storm was observed in 2001.

"The intensity [of the current storm] is comparable to what was seen by the first Viking lander in the 1970s," Matijevic said.

"But right now we think it's only a regional storm. We assume it will clear up over the next couple days, and we'll resume operations at that time."

And that means Opportunity's "toe-dip" into Victoria Crater is still on the docket, he said.

"Once the skies are clear, energy will be back up to levels where we can drive and do science."

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