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Planetary News: Mars (2007)

New Images Reveal Threatening Dust Storms on Mars

 

August 29, 2007
Spirit's dimming Sun
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Spirit's dimming Sun
Several times a sol, the Mars Exploration Rovers take images of the Sun (using a very dark solar filter) to determine the opacity of the atmosphere (a property that is referred to as "tau"). Here, images of the Sun taken since sol 1220 of Spirit's mission have been calibrated to show how dim the Sun appeared through the dust storm. Wherever a circle with an "X" appears, for example, for sols 1263-1265 (July 23-25, 2007), the skies were so dark that Spirit could not muster enough power to perform its usual tau measurements. Credit: NASA / JPL / Cornell / Emily Lakdawalla

The Mars Exploration Rovers, Spirit and Opportunity, continue to persevere in brutal conditions on Mars. Today, Cornell University released images of the Sun as seen from the Martian surface that show how opaque the Martian atmosphere has been in the face of a raging, two-month dust storm.

To understand the gravity of the storm, engineers and astronomers monitor the situation by examining the images of the Sun and measuring the amount of dust or the opacity of the atmosphere.

The Planetary Society's Emily Lakdawalla assembled the mosaic of images, which were taken daily by the panoramic cameras (Pancams) on both rovers. The images were calibrated by students in Cornell's MarsLab image-processing facility and made available through collaboration with Jim Bell, Cornell professor of astronomy and the principal investigator on the rovers' Pancam imaging team.

"Emily's mosaics are quite remarkable. They show a rover's-eye view of the storm getting worse, and this little light bulb we call the Sun getting dimmer and dimmer and dimmer as the dust clouds built up," said Bell.

Since June, a massive dust storm has engulfed much of the Martian surface. The storm has put the rovers in danger, as they depend upon solar power to run during the day and to survive the harsh, cold Martian nights. As dust clouds block the sunlight and dust settles on the solar panels, the rovers' energy is depleted. Only wind can remove the dust, Bell said.

For the rover Spirit, the Jet Propulsion Laboratory (JPL), reports that even though the Martian sky above Gusev Crater is clearing, solar power levels remained fairly low and constant dust now appears to be accumulating on the solar panels. Between sol 1283 (August 12) and sol 1286 (August 16), the atmosphere cleared by about 35 percent, leading to daily energy levels of about 300 watt-hours (the amount of energy needed to light a 100-watt bulb for three hours). Typical levels for the rovers before the dust storms were around 700 to 900 watt-hours.

Opportunity's dimming Sun
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Opportunity's dimming Sun
Credit: NASA / JPL / Cornell / Emily Lakdawalla

On the other side of Mars, Opportunity -- now waiting to enter Victoria Crater from the rim -- is currently experiencing its lowest power levels to date. According to JPL, the sky was so dark in mid-July that less than 200 watt-hours of daily energy was available. But skies are slowly clearing, offering hope that the rover will be ready for a descent into the crater soon. Opportunity benefited from wind blowing some dust off solar panels on August 22. Under gradually clearing skies, Opportunity's solar panels were producing about 300 watt hours daily by August 24.

"Through the worst of the storm, each daily image of the Sun conveyed powerfully how oppressively dark the Martian skies became," said Lakdawalla. "Now that each day is bringing slightly brighter images of the Sun, I feel more and more relieved. The rovers are out of immediate danger."

Emily Lakdawalla has posted images and more information on this story at The Planetary Society's Blog.

A complete report on the adventures and activities of Spirit and Opportunity this month, will be posted on Friday, August 31, 2007 in the Mars Exploration Rover Update.