The Lincoln head penny was first minted in 1909, in honor of the centennial of Abraham Lincoln’s birth. Ken Edgett, principal investigator of the Mars Hand Lens Imager, or MAHLI, must be a coin collector, because he bought one of the rarer 1909 pennies (with his own money) to fly on the Mars rover Curiosity. This one has the VDB initials of the coin’s designer – Victor David Brenner — on the reverse. The penny is part of a set of different color paints and various size lines to help calibrate the camera and interpret the color and brightness of images. One of the coatings fluoresces in ultraviolet light, which is a phenomena I have studied in the past. Some paints fluoresce more or shift to a different color when exposed to space, which can interfere with cameras or telescopes operating in those wavelengths. Other coatings lose their fluorescence.
It will be interesting to see how these hold up over time.