Mercury is the closest planet to the Sun and due to its proximity it is not easily seen except during twilight. For every two orbits of the Sun Mercury completes three rotations about its axis and up until 1965 it was thought that the same side of Mercury constantly faced the Sun. Thirteen times a century Mercury can be observed from Earth passing across the face of the Sun in an event called a transit, the next will occur on the 9th May 2016.

Planet Profile

  • Circumference at Equator: 15,329.1 km
  • Mass: 330,104,000,000,000 billion kg (0.055 x Earth)
  • Average Distance from Sun: 57,909,227 km (0.39 AU)
  • Known Satellites: None
  • Notable Satellites: None
  • Length of Orbit: 87.97 Earth days
  • Surface Temperature: -173 to 427°C

Facts about Mercury

  1. Mercury is almost the densest planet in the solar system and is second only to Earth
  2. The largest known crater on Mercury, the Caloris Basin, has a diameter of 1,550 km
  3. As of 2012 Mariner 10 and MESSENGER are the only two spacecraft to have visited Mercury
  4. It is estimated Mercury’s core makes up 42% of its volume, for comparison Earth’s core makes up 17%
  5. Mercury has the highest orbital eccentricity of all the planets with its distance from the Sun ranging from 46 to 70 million km
  6. While Mercury has at atmosphere it is constantly being stripped and replenished
  7. Mercury is named after the Roman messenger to the gods