Martian Dust Storms Engulf Planet

Since late June 2007, Mars has been having a series of regional dust storms, which have obscured most of the planet--and the Mars rovers--with dust. The Mars Reconnaissance Orbiter image from June 22, 2007 (top) shows the first in the series of storms. The July 17, 2007 image (bottom) shows a global "veil of dust" encircling the planet. Credit: NASA/JPL/Malin Space Science Systems

The surface of Mars is now obscured by a globe-engulfing veil of dust, officials report, posing a potentially longer-lasting threat to the plucky NASA rovers on the planet's surface.

A collection of massive regional dust storms, first reported by SPACE.com, have been whipping up a "planet-encircling veil of dust" on the red planet since late June of this year, according to a recently published release by Malin Space Science Systems (MSSS) in San Diego, Calif.

"The dust raised by these individual storms has obscured most of the planet over the past few weeks," the company said.

A series of images shows how the regional storms, which covered about 10 million square miles (25.9 million square kilometers) two weeks ago, have lifted enough dust to blot out the surface of the red planet.

Sun-obscured explorers

The Mars rovers Spirit and Opportunity weathered the regional storms by cutting back their activity, but the global dust event may escalate danger to the rovers that depend on sunlight to survive the bone-chilling cold of the planet.

Steve Squyres of Cornell University, who is the lead scientist of the Mars Exploration Rover Project, reported on Monday that the dust levels are some of the worst the rover team has seen.

"To give you a sense of the 'thickness' of the dust, the brightness of the sun as viewed from the surface is now down to less than 5 percent of what it would be with a perfectly transparent atmosphere," Squyres told SPACE.com in an e-mail. "Of course, Mars never has a perfectly transparent atmosphere, but the sun is still very faint."

The saving grace for the rovers, however, is that the dust creates a glow of indirect sunlight. The effect is similar to Earth's cloudy weather, which blocks the sun but does not completely prevent light from reaching the ground.

"Even if it's cloudy enough that the sun is obscured completely, it's not pitch black out," Squyres said. "The sunlight gets scattered through the clouds. Same thing with the dust clouds on Mars."

'Actively doing science'

Despite the thick haze of red dust that gobbles up most of the rovers' solar power, Squyres said on Monday that Spirit and Opportunity were "both actively doing science" near their respective sites at Gusev Crater and Meridiani Planum.

"One side benefit of the high winds that have caused this dust storm is that they have done a wonderful job of removing dust from the solar arrays on both rovers" he said, going so far as to say that Opportunity's solar panels are cleaner than they were just months after landing in 2004.

Still, Squyres noted that energy collected by the rovers' solar panels is about one-third of the level the first generated, so their activity is limited-and may be limited for months.

"As with previous large dust-raising events on Mars, once the active storms die down, many weeks to months will pass before the dust settles out and the atmosphere clears," MSSS said.