Mastcam Special Filters Help Locate Variations Ahead

This pair of images from the Mast Camera (Mastcam) on NASA's Curiosity rover illustrates how special filters are used to scout terrain ahead for variations in the local bedrock. The upper panorama is in the Mastcam's usual full color, for comparison. The lower panorama of the same scene, in false color, combines three exposures taken through different "science filters," each selecting for a narrow band of wavelengths. Filters and image processing steps were selected to make stronger signatures of hematite, an iron-oxide mineral, evident as purple. Hematite is of interest in this area of Mars -- partway up "Vera Rubin Ridge" on lower Mount Sharp -- as holding clues about ancient environmental conditions under which that mineral originated. In this pair of panoramas, the strongest indications of hematite appear related to areas where the bedrock is broken up. With information from this Mastcam reconnaissance, the rover team selected destinations in the scene for close-up investigations to gain understanding about the apparent patchiness in hematite spectral features. The Mastcam's left-eye camera took the component images of both panoramas on Sept. 12, 2017, during the 1,814th Martian day, or sol, of Curiosity's work on Mars. The view spans from south-southeast on the left to south-southwest on the right. The foreground across the bottom of the scene is about 50 feet (about 15 meters) wide. Figure 1 includes scale bars of 1 meter (3.3 feet) in the middle distance and 5 meters (16 feet) at upper right. Curiosity's Mastcam combines two cameras: the right eye with a telephoto lens and the left eye with a wider-angle lens. Each camera has a filter wheel that can be rotated in front of the lens for a choice of eight different filters. One filter for each camera is clear to all visible light, for regular full-color photos, and another is specifically for viewing the Sun. Some of the other filters were selected to admit wavelengths of light that are useful for identifying iron minerals. Each of the filters used for the lower panorama shown here admits light from a narrow band of wavelengths, extending to only about 5 to 10 nanometers longer or shorter than the filter's central wavelength. The three observations combined into this product used filters centered at three near-infrared wavelengths: 751 nanometers, 867 nanometers and 1,012 nanometers. Hematite distinctively absorbs some frequencies of infrared light more than others. Usual color photographs from digital cameras -- such as the upper panorama here from Mastcam -- combine information from red, green and blue filtering. The filters are in a microscopic grid in a "Bayer" filter array situated directly over the detector behind the lens, with wider bands of wavelengths. The colors of the upper panorama, as with most featured images from Mastcam, have been tuned with a color adjustment similar to white balancing for approximating how the rocks and sand would appear under daytime lighting conditions on Earth. https://photojournal.jpl.nasa.gov/catalog/PIA22065