Two Moons Passing in the Night (Labeled)

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. "It is incredibly cool to be running an observatory on another planet," said planetary scientist Jim Bell of Cornell University, Ithaca, N.Y., lead scientist for the panoramic cameras on Spirit and Opportunity. In this animation, both martian moons, Deimos on the left and Phobos on the right, travel across the night sky in front of the constellation Sagittarius. Part of Sagittarius resembles an upside-down teapot. In this view, Phobos moves toward the handle and Deimos moves toward the lid. Phobos is the brighter object on the right; Deimos is on the left. Each of the stars in Sagittarius is labeled with its formal name. The inset shows an enlarged, enhanced view of Phobos, shaped rather like a potato with a hole near one end. The hole is the large impact creater Stickney, visible on the moon's upper right limb.

Spirit acquired these enhanced-brightness images with the panoramic camera on the night of sol 585 (Aug. 26, 2005). 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. Spirit took the six images that make up this animation using the camera's broadband filter, which was designed specifically for acquiring images under low-light conditions.