Phobos And Deimos The Moons Of Mars 

Finding the moons of Mars is incredibly hard for the backyard stargazer. These two moons are so small and dim that Mars is about 200,000 times brighter. They are also very close to the planet. Discovered in 1877 by Asaph Hall using a 26in(650mm) telescope at the Naval Observatory.

The Martian satellites are named after the sons of Ares the god of war. Phobos(panic) and Deimos(dread).


Phobos, moon of Mars

Phobos the larger inner moon has an apparent magnitude of 11.3.

this moon orbits Mars so fast it appears in the sky twice a day.


Orbiting from west to east Phobos takes about 4.5 hours to move across the sky.

Smaller in area than the state of Delaware, Phobos is too small to become rounded by its own gravity. Orbiting about 3,700 miles from Mars, this is closer to the parent planet than any other natural satellite in the Solar System. In an equatorial orbit Phobos is not visible above the horizon at +70.4 degrees or -70.4 degrees latitude on Mars.

If you were on Mars you would see Phobos transit the Sun and cast a shadow. Phobos though is too small to cause a total eclipse.

Heavily cratered without an atmosphere for protection from impacts. Stickney crater the most prominent is named after Asaph Hall's wife.


Deimos, moon of Mars

Deimos is the smaller of the two and is the outer moon farthest away from the planet Mars.

Taking slightly longer than 30 hours to orbit Mars, 2.7 days elapse between its rising and setting for an equatorial observer.

For a stargazer on Mars, Deimos would appear to the naked eye as a star. When full it would be about as bright as Venus appears to us on Earth. During the quarter phases it would be about as bright as the star Vega. The apparent magnitude is about 12.4, not very bright.

The 2 largest craters are named for writers who used Martian moons in their writings before their discovery.

Swift Crater and Voltaire Crater are the only named features on Deimos.

Like Phobos, Deimos lies in a very equatorial orbit and observers on Mars would not be able to see it above the horizon after about +80 and -80 degrees latitude.

Finding The Moons Of Mars

Finding these two moons will take an incredible amount of patience.

In very dark skies with good seeing conditions you could find them in a 6in(150mm) telescope, but because they are always in the glare of Mars you probably need at least a 12in(300mm) scope to have a chance. 

Best time is when the moons are at eastern or western elongation which is maximum separation from the planet.

This article from Sky & Telescope will give you a tip to help you try and find them.

With calm dark skies, time, patience, and luck, you too can find panic and dread Phobos and Deimos...The sons of Ares, the moons of Mars.

› Moons of Mars
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