杏吧原创

NASA鈥檚 twin Mars rovers Spirit and Opportunity are starting to move again after being immobilised for six weeks by severe dust storms.

The storms hit in late June, just as Opportunity was poised to enter the 800-metre-wide Victoria crater, which may 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 to generate power. Both rovers had to stop driving, and Opportunity was so starved of power that its handlers worried it might freeze to death during the cold Martian night.

Now, the storms have finally receded and both rovers are about to start driving towards much-anticipated targets.

鈥淭he opacity of the atmosphere is decreasing 鈥� the available sunlight is going up slowly,鈥� says rover scientist Ray Arvidson of Washington University in St Louis, Missouri, US.

And the good weather looks set to continue, according to the latest observations from NASA鈥檚 Mars Reconnaissance Orbiter. 鈥淚t doesn鈥檛 look like there are any major dust storms on the way,鈥� Arvidson told New 杏吧原创.

Dust veil

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.

鈥淲e鈥檝e been wanting to go to the top of Home Plate for a long time,鈥� Arvidson says. Examining the rocks there should help shed more light on the history of Home Plate. He says Spirit is expected to arrive there around 3 September.

Dust left over from the storms is still causing some problems, however. Some dust seems to have fallen onto the lens of Spirit鈥檚 microscopic imager when the imager鈥檚 protective cover was opened. The microscopic imager is one of several instruments attached to the end of Spirit鈥檚 robotic arm and is used to obtain detailed views of rocks and soil.

鈥淲e noticed that the images were a little bit degraded,鈥� Arvidson says. 鈥淲e can still use the instrument and it returns fantastic data, it鈥檚 just the quality of the contrast is down.鈥�

Shake off

To try to remove the dust, the team has been pointing the imager directly down and opening and closing the cover, hoping that gravity would pull the dust off. 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鈥檚 robotic arm, so brushing a rock with the arm might remove the dust, Arvidson says.

To avoid the same problem with Opportunity, the rover team is going to wait for the wind to clear dust from the microscopic imager鈥檚 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.

Wind gusts

As dust settles out of the atmosphere, some is also landing on the rovers鈥� solar panels and partly offsetting the power gains from clearer skies. But Arvidson says he does not expect this 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.

Opportunity has also started driving and was expected to arrive as early as Monday at a spot on Victoria crater鈥檚 rim, where it will make some new observations. These will help the team evaluate science targets in the crater and possible routes to get inside.

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 crater, Arvidson says: 鈥淲e want to make sure if we have some mobility problems that there鈥檚 energy to spare to get out of the problem areas.鈥�

Mars Rovers 鈥� Mars is full of surprises; learn more in our continually updated .