Quick Facts  Mythology  The Surface  The Core  Caloris Basin  Atmosphere

The Winged Messenger

Quick Facts:
Mercury is the closest planet to the Sun and the eighth largest.
Mercury's magnetic field has a strength of about 1% that of Earth's.
Temperature variations on Mercury are the most extreme in the solar system ranging from 90 K to 700 K.
Distance from the Sun: 57,910,000 km (36 million miles or 0.38 AU) 
Period of Revolution: 88 days
Diameter: 4,880 km (3,100 miles)
Mass: 3.30e23 kg
Satellites: 0

Mythology:
In Roman mythology Mercury is the god of commerce, travel and thievery. Mercury has a Greek counterpart known as Hermes, the messenger of the Gods. The planet was probably given this name because of how quickly it moves across the sky.

The Surface:
The surface of Mercury has enormous escarpments, some up to hundreds of kilometers in length and as much as three kilometers high. Some cut through the rings of craters and other features in such a way as to indicate that they were formed by compression. It is estimated that the surface area of Mercury shrank by about 0.1% .
In addition to the heavily cratered terrain, Mercury also has regions of relatively smooth plains. Some may be the result of ancient volcanic activity but some may be the result of the deposition of ejecta from cratering impacts.

The Core:
Mercury has only a relatively thin silicate mantle and crust. Mercury's interior is dominated by a large iron core whose radius is 1800 to 1900 km. Mercury's dense iron core is larger than Earth's, taking up the majority of the planet. The silicate outer shell is only 500 to 600 km thick. At least some of the core is probably molten.

Caloris Basin:
One of the largest features on Mercury's surface is the Caloris Basin. It is thought to be like the large basins on the Moon. Like the lunar basins, it was probably caused by a very large impact early in the history of the solar system.
 
Atmosphere:
Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind. Because Mercury is so hot, these atoms quickly escape into space. Thus in contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly being replenished.