Mercury

Mercury, the closest planet to the Sun, is a small, barren, crater-covered planet similar to Earth's Moon.

Marvel Comics Continuity
An Autobot unit consisting of Inferno, Sandstorm and Broadside caught a Furnacian Firebug which was setting fire to human settlements, and exiled the creature to Mercury in a message pod.

Blaster mentioned sunbathing on Mercury following a vacation to II.

Sailor Moon
Mercury (水星; Star of Water) is the closest planet to the Sun in this Solar System.

In the Sailor Moon series, Mercury was protected by Sailor Mercury, even though in the present she resided on Earth with the other Sailor Senshi of the system.

In the manga, Mariner Castle orbited Mercury, and was the palace of Princess Mercury.

Exosquad
Mercury is the smallest planet of the terrestrial planets, or Homeworlds, and the only planet yet to be terraformed. It is inhabited by humans; though only to a limited degree of scientific outposts due to the Outer Space Treaty of 1967. Though Mercury served little strategic importance and was not rich in resources, it was conquered by the Neosapien Commonwealth during “Operation Destiny” of the Neosapien War in 2119 A.D. as an exclamation point on the Neosapien Order’s complete dominance over the Homeworlds. A Neosapien outpost was maintained throughout the war until 2120 A.D. when ExoFleet and the Pirate Clans captured Mercury for use as a base of operations to liberate Venus.

Geography
Mercury is the closest planet to the Sun, orbiting it every 88 Earth days and a single day on Mercury lasts exactly two Mercury years, or about 176 Earth days. The planet is named after the Roman god Mercury, the messenger to the gods. Mercury is smaller than the largest Moons in the Solar System, Ganymede and Titan. Mercury’s surface is very similar in appearance to that of the Moon, showing extensive mare-like plains and heavy cratering, indicating that it has been geologically inactive for billions of years. There are two geologically distinct plains regions on Mercury. Gently rolling, hilly plains in the regions between craters are Mercury's oldest visible surfaces, predating the heavily cratered terrain.

Mythology
In Roman mythology, Mercury, also known as Hermes in the Greek pantheon, was primarily known as a fleet-footed messenger. He was also a god of commerce and invention, and escorted the souls of the departed to Hades. He was the son of Maia and Jupiter. According to legend, Mercury was the one to invent the lyre, such as the one used by Sailor Mercury to perform Mercury Aqua Rhapsody.

Astrology
Mercury is usually associated with the mind and the inward self; it can symbolize intellect, memory, perception, or travel. Mercury is associated with Wednesday. Dante Alighieri associated Mercury with the art of dialectic.

In Chinese astrology, Mercury is ruled by the element water. In Indian astrology, Mercury represents communication.

Trivia

 * In the Japanese calendar, Wednesday is called "suiyoubi" (水曜日), meaning "the day of water."