Mercury   – The closest planet to the sun

Mercury is a small terrestrial planet with no rings or moons and is just a little bigger than our moon. It is named for the swiftest of the ancient Roman gods, Mercury was the god of commerce.

Its orbit is close to the Sun and speeds through a year in just over 87 days. Since it is the closest planet to the Sun, its orbit is the shortest in length and it travels the fastest.  Although it has a fast revolution, Mercury spins very slowly on its axis, taking 58.6 days to make one turn.

Being so close to the sun, Mercury is hard to see, often lost in the glare of the sun. Mercury has a surprising temperature range changing from a high of 427°C in the sunlight of day, to a low of -173°C in the darkness of night.

With no real atmosphere, there is no method for the heat on the sunny side to flow to the cold night side. The lack of any real atmosphere is also why it is covered in craters. Meteors do not burn up so more hit the surface and there is no weathering to make them erode away.


  • 1974 Mariner 10 flybys took photographs of about half Mercury’s surface
  • 1991 Earth-based radar telescope finds signs of ice in craters at the poles
  • 2008 Messenger makes three flybys
  • 2011 Messenger orbital mission sends images and data back to earth

Mercury  Venus  Earth Mars  Jupiter  Saturn  Uranus  Neptune