Ok, let’s play a game of “Word Association”. I’ll say a word, you reply with whatever springs to mind…
Hmm. I heard “rocks”… “canyons”… “rovers”… “volcanoes”… “martians”…
All good answers, but I would have said “dust”. Mars is absolutely covered in the stuff. It’s everywhere. It covers every rock and crater slope, there’s so much of it in the air that turns the daytime sky pink, and the wind blows and sculpts it into vast areas of rippling, snaking, meandering dunes. Mars is the Dust Planet.
Which isn’t good news for solar powered Mars rovers like Opportunity. Oppy’s solar panels have been getting covered in dust from the moment she rolled off her landing stage, it just goes with the territory. If they become coated in too much dust, they start to generate less power, and less power means Oppy can do less science, and drive less far, during each sol. In a worst case scenario, a Mars rover can “drown” in the dust of a global dust storm.
Luckily, what Mars gives, it sometimes takes away too. Mars is windy, occasionally, and although that wind is very, very gentle compared to the winds we have here on Earth it can still produce gusts (sometimes, we think, ‘dust devils’) strong enough to lift some of the dust off a Mars Exploration Rover’s panels, upping its power levels and stopping it from grinding to an untimely halt. This has happened countless times to both rovers since they landed all those years ago, and it seems it has just happened to Opportunity again, because “before” and “after” images show a very dramatic cleaning of her solar panel wings has taken place.
On the picture above you can see, on the left, what Oppy’s solar arrays looked like on Sol 2274. You’ll see they look grey and dull, not very far from the same colour as the dusty ground behind and beneath them. On the right is an image from sol 2299, and the solar panels look much darker and cleaner, even shiny, so at some point a gust of wind has lifted a lot of the dust off Oppy and given her a good, and well-needed, clean…! :-)
In fact, I’ve just found this image from sol 2294…
on which Oppy’s wing looks pretty dusty, but the lighting conditions aren’t the same as they were on the 2274 image so it’s hard to draw any conclusions about more precisely when the cleaning event took place.
But really it doesn’t matter when it happened, it was GREAT timing, because Oppy has just started another push east towards Endeavour crater, covering 70m a sol for the past few sols. With her power levels boosted, even if only by just a little, she’ll have the power needed to make steady drives, and do some science during any “Hmm, that looks interesting!” stops along the way.
The fantastic day when Oppy rolls up at the foothills of Endeavour Crater just got a little bit closer… :-)