NASA Rover Gets Movie as a Mars Moon Passes Another

The larger of the two moons of Mars, Phobos, passes directly in front of the other, Deimos, in a new series of sky-watching images from NASA’s Mars rover Curiosity.

A video clip assembled from the images is at http://youtu.be/DaVSCmuOJwI.

This movie clip shows the larger of Mars' two moons, Phobos, passing in front of the smaller Martian moon, Deimos, as observed by NASA's Mars rover Curiosity. Image credit: NASA.

This movie clip shows the larger of Mars’ two moons, Phobos, passing in front of the smaller Martian moon, Deimos, as observed by NASA’s Mars rover Curiosity. Image credit: NASA.

Large craters on Phobos are clearly visible in these images from the surface of Mars. No previous images from missions on the surface caught one moon eclipsing the other.

The telephoto-lens camera of Curiosity’s two-camera Mast Camera (Mastcam) instrument recorded the images on Aug. 1. Some of the full-resolution frames were not downlinked until more than a week later, in the data-transmission queue behind higher-priority images being used for planning the rover’s drives.

These observations of Phobos and Deimos help researchers make knowledge of the moons’ orbits even more precise.

“The ultimate goal is to improve orbit knowledge enough that we can improve the measurement of the tides Phobos raises on the Martian solid surface, giving knowledge of the Martian interior,” said Mark Lemmon of Texas A&M University, College Station. He is a co-investigator for use of Curiosity’s Mastcam. “We may also get data good enough to detect density variations within Phobos and to determine if Deimos’ orbit is systematically changing.”

The orbit of Phobos is very slowly getting closer to Mars. The orbit of Deimos may be slowly getting farther from the planet.

This illustration provides a comparison for how big the moons of Mars appear to be, as seen from the surface of Mars, in relation to the size that Earth's moon appears to be when seen from the surface of Earth. Image credit: NASA.

This illustration provides a comparison for how big the moons of Mars appear to be, as seen from the surface of Mars, in relation to the size that Earth’s moon appears to be when seen from the surface of Earth. Image credit: NASA.

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