A high-power camera on the Mars Curiosity rover snapped a picture of a 1909 American penny featuring Abraham Lincoln. The coin is used as a calibration target for the Mars Hand Lens Imager (MAHLI) that is at the end of Curiosity’s robotic arm. In just over an Earth year on the Red Planet, you can see the bright copper is muted by lots of Mars dust…“The image shows that, during the penny’s 14 months (so far) on Mars, it has accumulated Martian dust and clumps of dust, despite its vertical mounting position,” the Planetary Science Institute stated.
I wrote about this in February 2012. There’s something to be said for electrostatic forces. You would think with vertical mounting and the jostling as the rover travels that there wouldn’t be this much dust on the penny.
We’re going to have to be smarter when humans go to Mars, especially with moving parts that can get worn down or with environmental seals. That much dust would cause some problems.