Planet Mercury is named after the Roman messenger god. It is the closest planet to the Sun and is the second smallest.

The picture to the left shows Mercury's surface being almost identical to the Moon. It is covered in a massive number of craters and is definitely more cratered than the Moon.

The craters would have been formed in the early life of Mercury when it would have been struck by hundreds of meteorites left over from the creation of the Solar System. The biggest crater is the Caloris Basin, which is 808 miles wide.

The core of the planet, which is visible in the illustration below, appears to be slightly molten. It is made out of iron and accounts for 70% of Mercury's mass.

Interestingly the sky of Mercury is black because the planet has no atmosphere to scatter the Sun's light.

Mercury orbits the Sun at an incredible speed because of its close proximity to the Sun. The Sun's massive gravity creates a warp that directly affects the orbit of Mercury.

The picture at the top was taken by the only 20th century space probe that visited Mercury, Mariner 10 in 1974.

In 2008, a new space probe called Messenger did a flyby of Mercury and imaged the whole planet. It also discovered never before seen surface features that included surface faults.

Name: Mercury

Distance from Sun: 35,983,095 miles

Diameter: 3032 miles

Length of Day: 58.7 days

Length of Year: 88 days

Number of moons: 0