The Martian Lunar System

Diagram of the
Martian moon system by David Buth

The Martian Lunar System

The discovery of "hurtling moons of Barsoom" to use Edgar Rice Burrough's colorful phrase contains a curious puzzle of literary history. The tiny moons Phobos and Deimos were discovered and named by Asaph Hall in 1877. Hall was working with the new 26 inch refracting telescope at the U.S. Naval Observatory in Washington. Beginning in August of that year Hall began a systematic search for possible Martian satellites. He found Deimos on Aug. 11 and Phobos on Aug. 18. They were named after the attendants of the God of War. Both moons are very tiny and orbit Mars quite closely which explains why they were not discovered until the late 19th Century. Deimos orbits Mars at an altitude of 23,500 km. (14,600 mi.) with a period of 30 hours and 18 minutes. Phobos, the inner moon orbits Mars at an altitude of 9400 km. (5,800 mi.) with a period of only 7 hours and 38 minutes.

The puzzle lies in the fact that Jonathan Swift (1667-1745) in his famous satire "Gullivers' Travels" (1726) written to "vex the world" as he put it, describes Mars as having two tiny moons as Hall discovered in 1877, some 151 years later! This delightful satire certainly did vex the powers that be in the early 18th Century and is a story loved by young and old alike today. It also vexes historians to this day, how did he know? Was it just a lucky guess? Did he have access to an unusually powerful telescope during unusually good seeing conditions? We may never know. What ever the results of this puzzle, I highly recommend the original "Gullivers' Travels" (1726), but be warned, it is not a children's story in the original like it is in some later adaptations.

Because the Martian moons orbit so close to their primary, they neatly bracket the Martian Clarke or Synchronous orbit as you can see in the map above. This fortuitous arrangement will allow resupply and shielding of a Martian Synchronous Space Station with significantly greater ease than the Terrestrial Geosynchronous equivalent being resupplied and shielded from Earth's Moon. This applies to Martian Comsats and Powersats as well. The down side of the tinyness of the Martian Moons is that no Lagrange Points can be established in the Martian System.

Since the Martian Moons are actually Carbonaceous Asteroids captured from the inner Asteroid Belt millions of years ago, they are considerably richer in volatiles than the Earth's Moon. This allows them to be used as fuel depots and life support raw materials supply as well as shielding and structural materials supply for the Mars Synchronous Station, the Low Mars Orbit Station, and the Mars Colony. They would also be the primary source of carbon black for the Martian poles if large scale terraforming of Mars were ever undertaken.

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Last rev: August 30, 1999 - counter