The Mast Camera, or Mastcam, aboard NASA's Curiosity Mars rover is built with two cameras – the left has a 34 mm focal length; the right, a 100 mm focal length. Behind each lens is a rotating wheel (circled in pink) arranged with filters. In addition to providing color images of the rover's surroundings, the cameras and their filters help scientists determine from afar the composition of rocks by the wavelengths of light, or spectra, they reflect in different colors. On Sept. 19, 2023, the left camera's filter wheel became stuck between the green and clear filter positions, the effects of which can be seen on the mission's raw, or unprocessed, images. The filter wheel is part of a spur-and-pinion mechanism, with the spur teeth around the filter wheel. The actuation uses a small motor that drives the pinion gear both forward and backward. Despite having been commanded at more than twice its normal torque, this motor has been unable to move in the counterclockwise direction. If unable to nudge the wheel back to the clear filter, the mission would rely on the higher resolution 100 mm right camera as the primary color-imaging system. The camera needs to take nine times more images than the left to cover the same area, which could affect how the team scouts for science targets and rover routes. The ability to observe detailed color spectra of rocks from afar would also be degraded. https://photojournal.jpl.nasa.gov/catalog/PIA26043