phobos
Phobos: Doomed Moon of Mars. JPL, NASA

At a time when NASA’s Curiosity is busy solving Martian mysteries, a new set of sky-watching images from the rover have showed Phobos, the larger of the two moons of the red planet, passing directly in front of the other, Deimos.

The images, which were taken by Curiosity’s telephoto-lens camera, Mastcam, on Aug. 1, are the first from the Martian surface to catch one moon eclipsing the other. According to scientists, the images are clear enough to reveal how the large craters on Phobos look like from the surface of Mars. They also believe that the observations will help researchers have a better understandings of the moons' orbits.

“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,” Mark Lemmon of Texas A&M University said, in a statement.

Scientists have found from the latest observations that the orbit of Phobos is very slowly getting closer to Mars, while the orbit of Deimos may be slowly getting farther away from the planet.

“We may also get data good enough to detect density variations within Phobos and to determine if Deimos' orbit is systematically changing,” Lemmon, who is a co-investigator for the use of Curiosity's Mastcam, said.

Phobos' diameter is less than 1 percent of the diameter of Earth's moon, and as seen from the surface of Mars, Phobos looks about half as wide as what Earth's moon looks like from Earth.

And, Phobos orbits so close to Mars -- about 3,600 miles above the surface -- compared to 250,000 miles for Earth’s moon, that the planet's gravitational tidal forces are dragging it down.

In 100 million years or so, Phobos will likely crash into Mars’ surface or be shattered by stress caused by the relentless tidal forces, the debris forming a ring around Mars, according to scientists.

Phobos and Deimos, named after the Greek gods of fear and terror respectively, are very small, each measuring about twice the size of Mount Everest. Both satellites have such weak gravity that moving at a speed of more than 25 miles per hour on their surface is enough to launch one into space, according to Wired.

Scientists also have assembled a video clip from the images of the moons. Have a look at the footage here:

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