"I used a Celestron 11-inch telescope," says Squyres. "The image is a stack of 80 15-second exposures."
The comet is green because its vaporizing nucleus emits diatomic carbon, C2, a gas which glows green in the near-vacuum of space. Mars is red because its rocky surface is widely rusted. The two colors make a heavenly ensemble. Amateur astronomers, if you have a GOTO telescope, enter these coordinates, and let the exposures begin.