Phobos and Deimos: Chariots of Fear and Terror

The moons of Mars Phobos and Deimos are suitably named as they refer to the mycological characters Phobos (panic/fear) and Deimos (terror/dread) who accompanied the god of war Ares into battle. Ares as you may remember is what the ancient Greeks called Mars.  Deimos was discovered 138 years ago on this very day (12 August) by the American astronomer Asaph Hall.  Phobos was also discovered by Hall six days after that (18 August). The Martian moons are among the smallest in our solar system.

Phobos is slightly larger than his brother but still rather small at only about 17 miles long (27km) at its greatest diameter. Its surface is covered in craters the largest being a 6 miles wide.  The impact that created this crater not only almost destroyed Phobos but also caused extraordinary streak patterns across the moon’s surface.  It hurtles around Mars three times a day ,orbiting only 3,700 miles (6,000 km) above the Martian surface and is gradually getting closer.  It is spiralling inward at about 2 meters each century meaning that sometime within the next 50 million years, it will either crash into Mars or be destroyed but tidal gravitational forces and form a ring around the planet.

Deimos orbits at a much further distance than his brother at around 14,573 miles (23,460 km) and also has a much longer orbital period of about 30 hours. Deimos is just a little over 9 miles long (15 km) making it one of the smallest moons in the entire solar system. Its surface has much less detail due to the thick layer of dust.  Deimos is slowly moving farther away from Mars, just like our own moon is slowing moving away from earth.  Eventually it will break free of the gravitational pull of Mars and will leave orbit, never to be see again.

The two Martian moons have been a lot more interesting than I had first belived them to be, Mars has been in the spotlight a lot in recent years and it is easy to forget about its two be it small companions.  Below are a few links to the sites I gathered my information on but I would like to advise you to check out and Photo Credit:  Reto Stöckli, Nazmi El Saleous, and Marit Jentoft-Nilsen, NASA GSFC.

Thanks To:,,,,,,


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