English: Taking advantage of extra solar energy collected during the day, NASA's Mars Exploration Rover Spirit settled in for an evening of stargazing, photographing the two moons of Mars as they crossed the night sky. The first two images in this sequence show gradual enhancements in the surface detail of Mars' largest moon, Phobos, made possible through a combination technique known as "stacking." In "stacking," scientists use a mathematical process known as Laplacian sharpening to reinforce features that appear consistently in repetitive images and minimize features that show up only intermittently. In this view of Phobos, the large crater named Stickney is just out of sight on the moon's upper right limb.

Spirit acquired the first two images with the panoramic camera on the night of sol 585 (August 26, 2005). The far right image of Phobos, for comparison, was taken by the High Resolution Stereo Camera on Mars Express, a European Space Agency orbiter. The third image in this sequence was derived from the far right image by making it blurrier for comparison with the panoramic camera images to the left. More information about the Mars Express image is available at http://www.esa.int/SPECIALS/Mars_Express/SEM21TVJD1E_1.html"

Scientists will use images of the two moons to better map their orbital positions, learn more about their composition, and monitor the presence of nighttime clouds or haze.