Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2024 February 26
Explanation: What if there were two moons in the sky -- and they eclipsed each other? This happens on Mars. The featured video shows a version of this unusual eclipse from space. Pictured are the two moons of Mars: the larger Phobos, which orbits closer to the red planet, and the smaller Deimos, which orbits further out. The sequence was captured last year by the ESA’s Mars Express, a robotic spacecraft that itself orbits Mars. A similar eclipse is visible from the Martian surface, although very rarely. From the surface, though, the closer moon Phobos would appear to pass in front of farther moon Deimos. Most oddly, both moons orbit Mars so close that they appear to move backwards when compared to Earth's Moon from Earth, both rising in west and setting in the east. Phobos, the closer moon, orbits so close and so fast that it passes nearly overhead about three times a day.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell (UMCP)
NASA Official: Amber Straughn;
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