Mercury is the closest planet to the Sun. It is also the smallest planet in the Solar System and has the slowest rotation speed (or spin). Curiously, visitors to Mercury would find that its day is about twice as long as its year.
It is quite similar to the Moon, with lots of craters, but it has no moon of its own.
The name Mercury comes from the Roman god of travel, and was probably given because the planet appears to move the fastest across the night sky.
The first spacecraft to visit Mercury was Mariner 10 in 1973, and again in 1974, but it only mapped about half of the surface. More recently (January 2008) the Messenger spacecraft captured more of the rocky planet's surface during a close approach.
|Facts and Figures||Mercury||Venus||Earth||Mars||Jupiter||Saturn||Uranus||Neptune|
|Orbital Distance (AU)1||0.38||0.72||1.0||1.52||5.2||9.45||19.2||30.06|
|Mass (Earth Masses)2||0.055||0.82||1.0||0.11||318||95.2||14.5||17.1|
|Surface Gravity (g)3||0.38||0.91||1.0||0.38||2.34||0.93||0.92||1.12|
|Surface Temperature||-200 to|
|460 °C||-80 to|
|-110 °C||-140 °C||-190 °C||-200 °C|
|Number of moons||0||0||1||2||63||60||27||13|