How do planets and their moons get their names?
How do planets and their moons get their names?
Answer:
The official names of planets and their moons are governed by an  organization called the International Astronomical Union (IAU). The IAU  was established in 1919. Its mission is "to promote and safeguard the  science of astronomy in all its aspects through international cooperation".  Its individual members are professional astronomers from all over the  World.  The IAU is the internationally recognized authority for  assigning names to celestial bodies and any surface features on them.
The IAU recognizes that astronomy is an old science and many of its  names come from long-standing traditions and/or are founded in history.  For many of the names of the objects in the solar system , this is  especially so. Most of the objects in our solar system  received names long ago based on Greek or Roman mythology . The IAU has  therefore adopted this tradition in its rules for naming certain  types of objects in the solar system.
Planets
With the exception of Earth, all of the planets in our solar system  have names  from Greek or Roman mythology. This tradition was continued when  Uranus, Neptune, and Pluto were discovered in more modern times.
Mercury is the god of commerce, travel and thievery in Roman mythology.  The planet probably received this name because it moves so quickly across the  sky.
Venus is the Roman goddess of love  and beauty. The planet is aptly named since it makes a beautiful sight in the  sky, with only the Sun and the Moon being brighter.
Earth is the only planet whose English name does not derive from  Greek/Roman mythology. The name derives from Old English and Germanic.  There are, of course, many other names for our planet in other  languages.
Mars is the Roman god of War. The planet probably got this name  due to its red color.
Jupiter was the King of the Gods in Roman mythology, making the name  a good choice for what is by far the largest planet in our solar system.
Saturn is the Roman god of agriculture.
Uranus is the ancient Greek deity of the Heavens, the earliest supreme  god.
Neptune, was the Roman god of the Sea. Given the beautiful  blue color of this planet, the name is an excellent choice!
Pluto is the Roman god of the underworld in Roman mythology.  Perhaps the planet received this name because it's so far from the  Sun that it is in perpetual darkness.
Natural Satellites
For those moons have been known for a long time (such  as the Galilean moons of Jupiter), the names were assigned from  mythological characters. For example, the moons of Jupiter were named  for characters who had roles in the life of Zeus (the Greek mythology  counterpart of the Roman God Jupiter).
For recently discovered natural satellites of the planets, they are first  given a "provisional" or  temporary name while additional observations are made to confirm their  existence. This temporary name (usually consisting of the year of  discovery and some number indicating the order of discovery in that year)  is assigned by an organization called the Central Bureau  for Astronomical Telegrams (CBAT). For example, when Voyager 2 found  a bunch of new moons in its 1989 Neptune encounter, they were  named S/1989 N 1, S/1989 N 2, etc. When the existence of the object is  confirmed (and its orbit determined), it is given a final name.  The name is suggested by the discoverer(s), but following tradition is  strongly encouraged.
Note that the moons of Uranus are a special case in our solar system.  They are named after literary characters (from works by William Shakespeare and Alexander Pope) rather then characters from mythology.
Surface Features
Landscape features on planets and natural satellites follow a set of  complicated conventions set by the IAU Nomenclature Committee. The rules set restrictions on allowable names such as: a planetary feature may not bear  the name of a living person or of a political or religious figure from the  last 200 years.