By far the biggest difficulty for robotic operations on the Martian surface are Sun-blocking dust storms. Not only do red-tinted dust clouds block the Sun from penetrating the atmosphere, the dust grains fall on solar panels, creating a layer of dusty sunscreen, reducing the amount of light falling on the photovoltaic cells. This is a special problem for long-term missions on the Red Planet. The rovers Spirit and Opportunity have been pottering around in the Martian regolith for over five years, mission planners had little idea their tough explorers would live much beyond their designed 3 month lifespan; long-term accumulation of dust was of no concern… until now.
No anti-dust system was built into the rovers design, so it is little wonder Spirit’s power-making solar cells are covered with dust. Not only covered, they are so encrusted that only a quarter of the sunlight incident on the panels was collected and converted into electricity. However, a few days ago, the usually unforgiving Martian atmosphere gave Spirit a helping hand, rather than dropping more dust onto the stained robot, a gust of wind swept some of the dust away, boosting the amount of light Spirit can now use.
There has been a measured 3% increase in the amount of sunlight being used by Spirit’s solar panels, from 25% before the “cleaning event” (i.e. a gust of wind) to 28% after. Spirit’s energy has now been increased from 210 watt-hours to 240 watt-hours (that’s an increase that could power a 30W lightbulb for an hour). As Spirit’s basic energy consumption is 180 watt-hours (for communications and basic survival), its discretionary (surplus) power supply has doubled from 30 watt-hours to 60 watt-hours. This is great as mission control can now do more stuff with the rover, such as giving it longer drives and carry out more science.
Not bad for a decrepit old Mars rover…