Mercury Facts

Mercury is the closest planet to the Sun and the smallest in the Solar System. It cannot support life due to extreme changes in temperatures and the lack of atmosphere. It has no protection from the Sun. Here are some facts on this little planet.

Interest facts about Mercury

  • Mercury is 36 Million miles (58 Kilometres) away from the Sun. This may sound a long way, but it makes it the closest planet to the Sun.
  • The planet is 57 Million Miles (92 Million Kilometres) away from Earth.
  • Mercury was named after the Roman God of messages Mercury who was believed to be the fastest of the Greek Gods. This is due to the planets quick orbit of the Sun, travelling at a very fast speed of 30 miles (48 kilometres) per second.
  • Thanks to its speed and proximity to the Sun a year on Mercury is 88 days. This is the length of time it takes for the planet to orbit the Sun
  • The planet may be orbiting at a fast speed, but it is not so quick to rotate. It takes a total of 59 days to turn on its axis and change from day to night. This means a year on Mercury is only one and a half days in length.
  • For a long time, it was believed that Mercury didn’t rotate at all but always kept one side facing the Sun. In 1965 it was discovered that Mercury did rotate using radar observations.
  • On Mercury, there is a considerable difference in temperature on the side of the planet facing the Sun and the side facing away. The temperature on the side of Mercury facing the Sun reaches a scorching 400 degrees Celcius (750 degrees Fahrenheit) and drops to a rather chilly -200 degrees Celcius (-328 degrees Fahrenheit) on the other side.
  • The atmosphere on Mercury is very thin. This is the reason for this big heat change as there is almost no atmosphere to help protect it from the Sun or retain any of the heat levels reached during the daytime.
  • Mercury is only a little planet in comparison to Earth with a diameter measuring 3100 miles in total (4990 Kilometres)
  • Galileo Galilei was the first person to observe Mercury using a telescope in the 17th century. Although in 1639 it was Giovanni Zupi who observed the planet Mercury orbited the Sun, leading to the discovery that the Universe does not revolve around the Earth.
  • It is the smallest planet in the Solar System. It was considered a planet from 1930 to 2006 until it was reclassed as a dwarf planet. It’s only slightly bigger than the Earths moon.
  • The surface of Mercury is mostly deep pits and dry craters. This makes it look a little bit like our moon. Some of the pits are miles deep.
  • Due to Pluto having barely any atmosphere its temperatures vary than any other object in our Solar System. They can range from −173 °C (−280 °F) at night to 427 °C (800 °F) during the day.
  • Mercury does not have any moons or rings because of the lack of atmosphere. Mercury and Venus are the only planets in the Solar System without moons.
  • There are no seasons on Mercury. The axis on Mercury is not tilted and there for the Sun stays the same distance from the planet.
  • Mercury orbits the Sun within the Earth’s orbit. This means we can see it from Earth in the morning and the evening without a telescope – although this is not easy.
  • It was once believed that Mercury was two separate planets. Due to the planet being visible at two separate points during the day, Ancient Greeks believed Mercury was two different planets and named them Mercury and Apollo before realising they were the same one.
  • It’s not known who discovered the planet Mercury. All ancient civilisations observed and recorded Pluto, including; Babylonians, ancient Greeks, ancient China, Rome and ancient Egypt.
  • Two Aircraft have visited Mercury from Earth to learn more about the planet.
  • NASA launched the Mariner 10 in 1973, and the aircraft flew past Mercury three times before the mission came to an end.
  • In 2004 NASA launched MESSENGER which stayed orbiting Mercury for four years making about 4000 rotations of the planet before running out of fuel and crashing into its surface in 2015.
  • Another mission will be launched in 2016 by the European Space Agency and Japan and should reach Mercury in 2024. This will hopefully tell us more about the planet.

Related Mercury Questions


Picture of Planet Mercury

Image of the Planet Mercury

Mercury Quick Facts

Mass:330,104,000,000,000 billion kg (0.055 x Earth)
Equatorial Diameter:4,879 km
Polar Diameter:4,879 km
Equatorial Circumference:15,329 km
Known Moons:None
Notable Moons:None
Orbit Distance:57,909,227 km (0.39 AU)
Orbit Period:87.97 Earth days
Surface Temperature:-173 to 427°C
First Record:14th Century BC
Recorded By:Assyrian astronomers