Deimos (dread) and Phobos (fear i.e. phobia) in Greek mythology, were he twin sons of Ares (Aries in English; Latin Mars) who accompany their father into war. Ares along with Eris (goddess of chaos) & Enyo (goddess of war and destruction) were the only children born of the union between Zeus and his wife Hera; Zeus obviously did better elsewhere.
Deimos and Dr. Hall
“I repeated the examination in the early part of the night of 11th [August 1877], and again found nothing, but trying again some hours later I found a faint object on the following side and a little north of the planet. I had barely time to secure an observation of its position when fog from the River stopped the work. This was at half past two o’clock on the night of the 11th. Cloudy weather intervened for several days.Dr. Hall’s notes on Deimos discovery
When Dr. Asaph Hall (Asteroid ASPH is named in his honour) discovered the twin satellites, long thought to revolve around the planet Mars, he named the first Deimos (discovered on August 12th) and Phobos (August 18th, almost a week later) appropriately enough. Both because of their very odd shapes, more like peanuts than our globular satellite the Moon, were argued to be asteroids. Their size did not help the argument, Phobos, is only 14 miles across (22 kilometers), while the smaller, Deimos, is only 8 miles (13 km), making them the smallest moons in the solar system; in comparison, our Moon has a diameter of 2,519 miles which sounds enormous but is still about 80% the size of our favorite planet, Earth.
“I dare not affirm that I was able to observe the phases of Mars; nevertheless, if I am not mistaken, I believe that I have seen that it is not perfectly round.”Galileo, December 30 1610 in a letter to a friend
Galileo’s observation is thought to because Phobos — its orbit is the closest to its native planet of any moon in the solar system — was too close to Mars to be seen separately. It’s shape does not help as it seems to hug its mother planet.
Asteroid vs Satellite
So what’s a moon a satellite and not an asteroid?
Well Phobos’s orbit is the key. Despite what astrology says, the Moon is not a planet — it is a satellite because it, like other moons in the Solar System, revolves around a major planets accompanying them in their revolutions around the sun. The Sun is the key, for it literally is the center by which all other bodies revolve. It’s size is tremendous — greater than 600 times as massive as all the other bodies combined. This incredible mass makes it central and gives the whole thing, its name (solar is Latin for Sun) — Solar System.
As so, because the satellite’s long axis is always directed toward Mars; like like our Moon to the Earth, and its rotational period is equal to its orbital period, Dr. Hall was able to prove conclusively it and Phobos’s were Moons.
If you enjoyed this post, please give us a like. We appreciate it.