Tuesday, July 15, 2014


There are two small asteroid-like moons that orbit Mars: Phobos and Deimos. Both are named after ancient Greek gods. The larger moon, Phobos, passes across the Martian sky from west to east three times in one Martian day (one sol). On Mars it would appear as half the size of a full moon on Earth. It is so close to the surface that it would not be visible from the Martian poles.

Deimos orbits at about 12,470 miles from the planet and moves slowly from east to west. This moon takes about 30 hours, a little over one Martian sol, to orbit its host. Because of its distance from the planet and the fact that it is only 8 miles across, it appears as a small dot of light in the sky, more like a star than a moon. The surface of this moon is covered with a layer of powdery dust that could be several hundred feet deep. Only the tips of giant boulders can be seen peeking above the dust. Scientists believe the dust formed as a result of billions of years of meteorite impacts. 

Phobos is the larger of the two moons at 14 miles across, and it orbits Mars from only 3,700 miles from the surface of the planet. Phobos is interesting because of its grooves and distinctive crater. It is believed that Phobos survived a powerful impact that may have fractured its interior. The impact may also be responsible for a series of long, deep grooves that appear to radiate away from the crater to an oddly shaped area on the other side of the moon. This impact gouged a large crater which has been named the Stickney crater. Asaph Hall discovered the moons in 1877. He named the crater on Phobos “Stickney,” his wife’s maiden name. He said if it were not for her encouragement he would have given up his search for the Martian moons.

Scientists can only speculate if these moons were born of Mars itself or if they are captured meteors, though the more popular belief is the latter. Much like our Earth moon, both Martian moons always face the same side to the planet. Both moons were named after the sons of Aries, the Greek god to Mars. Phobos means “fear” and Deimos means “dread.” Deimos seems to be slowly spiraling away from the planet while Phobos is drawing closer, which may cause it to collide with the planet in about 50 million years.

I’m wondering: Will Deimos disintegrate and form a ring around Mars before it would collide? Scientists believe there may be water on Phobos; if so, will we create a base on Phobos to store supplies? What do you think will happen?

Visit this link for images of Phobos and Deimos:

My resources are: NASA, Starry Skies, Universe Today, and Space.com

Discover my Lill and Mewe series books about Mars on my website: www.authorjeanelane.com

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