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The Question

(Submitted May 20, 1997)

If all of the planets are named after Roman gods, why is it that the moons of Mars (the Roman god of war) are Deimos and Phobos when those are the sons of the Greek god of war Ares?

The Answer

Aseph Hall, the discoverer of the moons of Mars in 1877, named them: see, for example

The names of the planets came down to us from the Romans, i.e. from Western Civilizations significant roots in the Roman Empire. However, the names of the satellites were chosen by their discoverers, and while they often chose to stay within the mythic traditions, they were at a bit more liberty to choose names (including some taken from English literature). Galileo was the first to discover and name satellites orbiting another planet, using one of the early telescopes. While observing Jupiter, he found 4 moons of the big planet, which he named Io, Europa, Ganymede, and Callisto. These were all names from Greek myths associated with Zeus, or Jupiter to the Romans.

Since these people were Greeks, it is reasonable to use the Greek names. When the Romans adopted the Greek myths, they would have changed their names, but most of their best stories involved Greeks.

Jim Lochner, Gail Rohrbach, Koji Mukai and David Palmer
for 'Ask an Astrophysicist'

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