NASAs rovers back in action following lull in Martian dust storm activity

NASAs twin Mars rovers, Spirit and Opportunity, have started to move again after being immobilised for six weeks due to severe dust storms on the Red Planet.

London, Aug 28 : NASA's twin Mars rovers, Spirit and Opportunity, have started to move again after being immobilised for six weeks due to severe dust storms on the 'Red Planet'.

The storms hit in late June, just as Opportunity was poised to enter the 800-metre-wide Victoria crater, which astronomers believe might contain crucial geological records of past conditions on Mars.

Lofting dust high in the atmosphere, the storms blocked precious sunlight needed for the rover solar panels, cutting the rovers off adequate power. Both rovers had to stop driving, and Opportunity was so starved of power that its handlers believed it might freeze to death during the cold Martian nights.

Now, the storms have finally receded and both rovers have started driving towards their much-anticipated targets.

"The opacity of the atmosphere is decreasing - the available sunlight is going up slowly," said rover scientist Ray Arvidson of the University of Washington in St Louis, US, adding that the good weather is likely to continue, as observations by NASA's Mars Reconnaissance Orbiter has revealed.

"It doesn't look like there are any major dust storms on the way," Arvidson said.

He said Opportunity is getting about 300 watt-hours of energy per day, more than twice the level it was getting during the worst part of the storms, but it is still not enough to start the descent into the Victoria crater.

"We want to make sure if we have some mobility problems that there's energy to spare to get out of the problem areas," he said.

He said Spirit is now getting 313 watt-hours of energy per day and has already made a short drive of 42 centimetres.

Over the weekend, the rover team started driving Spirit towards the top of Home Plate, a flat-topped hill thought to be the remains of a volcano that had an explosive eruption long ago, he said.

"We've been wanting to go to the top of Home Plate for a long time. Examining the rocks there should help shed more light on the history of Home Plate. Spirit is expected to arrive there around September 3," Arvidson said.

However, dust left over from the storms is still causing some problems, he said.

He said some dust seems to have fallen onto the lens of Spirit's microscopic imager when the imager's protective cover was opened. The microscopic imager is one of several instruments attached to the end of Spirit's robotic arm and is used to obtain detailed views of rocks and soil.

"We noticed that the images were a little bit degraded. We can still use the instrument and it returns fantastic data, it's just the quality of the contrast is down," Arvidson said.

Now, the handlers are trying to remove the dust by pointing the imager directly down and opening and closing the cover, hoping that gravity would pull the dust off, he said.

"Some of it does seem to have fallen off, since the image quality has improved somewhat. If that fails, the rover team hopes to shake it off. The microscopic imager is attached to the rover's robotic arm, so brushing a rock with the arm might remove the dust," Arvidson added.

He said, in order to avoid the same problem with Opportunity, the rover team is going to wait for the wind to clear dust from the microscopic imager's cover before opening it.

"Other cameras and instruments do not have covers, so they were less protected during the storm. The rover team is trying to determine if any of these other instruments have been contaminated by dust in ways that could interfere with their observations," New Scientist quoted Arvidson as saying.

"As dust settles out of the atmosphere, some is also landing on the rovers' solar panels and partly offsetting the power gains from clearer skies. But this is not going to become a serious problem. Gusts of wind help clean the panels from time to time, something that seems to have happened to Opportunity once already since the end of the storms," he said.

ANI