Two Moons and the Pleiades from Mars (Inverted Black and White)

Taking advantage of extra solar energy collected during the day, NASA's Spirit rover settled in for an evening of stargazing, photographing the two moons of Mars as they crossed the night sky. In this inverted black-and-white view, the Pleiades, a star cluster also known as the "Seven Sisters," is visible in the lower left corner. The bright star Aldebaran and some of the stars in the constellation Taurus are visible on the right. Spirit acquired this image the evening of martian day, or sol, 590 (Aug. 30, 2005). The image on the right provides an enhanced-contrast view with annotation. Within the enhanced halo of light is an insert of an unsaturated view of Phobos taken a few images later in the same sequence.

On Mars, Phobos would be easily visible to the naked eye at night, but would only be about one-third as large as the full Moon appears on Earth. Astronauts staring at Phobos from the surface of Mars would notice its oblong, potato-like shape and that it moves quickly against the background stars. It fact, Phobos moves so fast relative to the 24-hour-and-39-minute  sol on Mars (the length of time it takes for Mars to complete one rotation), taking only 7 hours, 39 minutes to complete one orbit of Mars, that it rises in the west and sets in the east. Earth's moon, by comparison, rises in the east and sets in the west. The smaller martian moon, Deimos, takes 30 hours, 12 minutes to complete one orbit of Mars. That orbital period is longer than a martian sol, and so Deimos rises, like most solar system moons, in the east and sets in the west.

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 five images that make up this composite with the Pancam broadband filter, which was designed specifically for acquiring images under low-light conditions.

Image credit: NASA/JPL/Cornell/Texas A&M

phobos_deimos_590A_inv_ld.txt


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This image shows two frames side by side. Inside the left frame, on the upper right side, is a small black circle against a white background representing Phobos, with a smaller black circle representing Deimos a little above and to the right of it. Inside the right frame is a large black circle representing a reverse black-on-white enhanced image of the light from Phobos with an oblong rock-like object representing Phobos itself inserted in the middle. A little above and to the right of that is a smaller black dot representing Deimos. In the lower left corner are several black pinpoints labeled "The Pleiades."