Mercury facts – Orbit, physical overview

Mercury is the smallest planet in our solar system. It is the closest planet to the Sun and is the fastest to complete one revolution around the Sun. Let’s learn some interesting facts about Mercury.


  • Mercury orbits at a distance of 36 million miles (average) from the Sun. 36 million miles is approximately equal to 0.4 Astronomical Units (AU). 1 Astronomical Unit is the average distance of Earth from the Sun. In other words, the distance of Mercury from the Sun is 0.4 times the distance of Earth from the Sun.

36 million miles = 58 million kilometers

  • Mercury takes 88 Earth days to complete one revolution around the Sun. It completes one rotation around its axis in 59 Earth days.
Mercury facts

Physical overview

  • Mercury is the smallest of all planets. It is even smaller in diameter than Jupiter’s largest moon Ganymede and Saturn’s largest moon Titan. However, it is heavier than Ganymede and Titan.
Diameter (km)Mass (kg)
Mercury4879.1 0.33011 * 10^24 kg
Ganymede (Jupiter’s largest moon)5,2620.1482
Titan (Saturn’s largest moon)5,1500.1346
  • Mercury is the second densest planet after Earth.

Mercury mean density = 5,427 kg / m3
Earth average density = 5,514 kg / m3

  • Mercury’s core is about 4,148 kilometers wide in diameter, 85 percent of planet’s mean diameter.

Mercury core diameter = 4,148 km
Mercury mean diameter = 4,879.4 km

  • Although Mercury is closest to the Sun, it is not the hottest planet. Venus is the hottest planet of our Solar System.

Interesting facts about Mercury

  • Mercury is the fifth brightest object in the night sky (excluding artificial satellites).
  • Mercury was named after the Roman God of commerce and communication, also credited as the “swiftest God”.
  • Venus and Mercury are the two planets with no moons.
  • The axis of Mercury has the least tilt angle of all planets. Its axis is tilted at about 2 degrees with respect to its orbital axis.
  • Mercury does not experience seasons because of its low tilt angle.
  • Two spacecraft have visited Mercury – Mariner 10 and MESSENGER.
  • Mercury has many craters on its surface formed due to asteroid collisions. As of 2019, 401 craters have been named.
  • The atmosphere on Mercury is very thin. The atmospheric pressure is just 5 x 10-15 bar (Earth’s atmospheric pressure is 1.014 bar).
  • The temperatures on Mercury can reach 430 ℃ during the day. On the contrary. nights can get extremely cold with temperatures as low as -180 ℃.
  • Mercury has no rings.

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