Acidalia Planitia Crater

This image of a crater in Acidalia Planitia was acquired March 8, 2003, during northern summer. The ejecta and small mounds surrounding the crater are yellowish. Just to the top of the image there are small mounds whose appearance is identical to the lower mounds, yet their color is bluish. While the forms are the same, the material contained in the mounds might be slightly different. False color images are necessary to find such differences.
The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.