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. This time-lapse composite, acquired the evening of Spirit's martian sol 590 (Aug. 30, 2005) from a perch atop "Husband Hill" in Gusev Crater, shows Phobos, the brighter moon, on the left, and Deimos, the dimmer moon, on the right. In this sequence of images obtained every 170 seconds, Phobos is moving from top to bottom and Deimos is moving from bottom to top. The bright star Aldebaran forms a trail on the right, along with some other stars in the constellation Taurus. Most of the other streaks in the image mark the collision of cosmic rays with pixels in the camera.

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 composite using Spirit's panoramic camera with the camera's broadband filter, which was designed specifically for acquiring images under low-light conditions.