Mercury

Mercury (or Sol I) is the first planet in the Sol system and is named after the Roman god Mercury, envoy of the gods according to Earth mythology.

Having only a minimal atmosphere and orbiting Sol at a distance of just 0.39 astronomical units, temperatures on the Mercurian surface range from 100 to 700 Kelvin.

Mercury was seen on a map depicting the Sol system watched by Nomad. (TOS: "The Changeling")

Mercury was featured in an amusing story a holographic Doctor Stephen Hawking told his holographic poker partners Albert Einstein and Sir Isaac Newton and Data. He said that "in that frame of reference the perihelion of Mercury would have precessed in the opposite direction!" Albert Einstein found this "a great story"; Sir Isaac Newton, however, did not understand the joke. (TNG: "Descent")

In the The Adventures of Captain Proton holoprogram series, Mercury was controled by Doctor Chaotica. When he tried to conquer earth, he claimed that those who oppose him "will face a dire fate as slaves in the mines of Mercury." (VOY: "Bride of Chaotica!")

Mercury is the innermost and smallest planet in the solar system,Pluto was once considered the smallest, but is now classified as a dwarf planet. orbiting the Sun once every 88 days. Mercury is bright when viewed from Earth, ranging from −2.0 to 5.5 in apparent magnitude, but is not easily seen as its greatest Elongation angular separation from the Sun is only 28.3°. It can only be seen in morning or evening twilight. Comparatively little is known about it; the first of two spacecraft to visit Mercury was Mariner 10|Mariner 10, which mapped only about 45% of the planet’s surface from 1974 to 1975. The second is the Messenger spacecraft, which mapped another 30% during its flyby of January 14, 2008. Messenger will make one more pass by Mercury in 2009, followed by orbital insertion in 2011, and will then survey and map the entire planet.

Mercury is similar in appearance to the Moon: it is heavily impact cratered, has no natural satellites and no substantial Celestial body atmosphere. However, unlike the moon, it has a large iron planetary core, which generates a magnetic field about 1% as strong as that of the Earth. It is an exceptionally dense planet due to the large relative size of its core. Surface temperatures range from about 90 to 700 K (−183 °C to 427 °C, −297 °F to 801 °F),with the subsolar point being the hottest and the bottoms of craters near the Geographical pole|poles being the coldest.

Recorded observations of Mercury date back to at least the first millennium BC. Before the 4th century BC, Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, which they called Apollo; the other visible only at sunset, which they called Hermes. The English name for the planet comes from the Romans, who named it after the Roman god Mercury, which they equated with the Greek Hermes. The astronomical symbol for Mercury is a stylized version of Hermes' caduceus.