Planet - Mercury


  • the nearest planet to the Sun is Mercury.
  • during its orbit – it is between 29 and 44 million miles away from the Sun.
  • Mercury has the fastest orbit – one orbit around the Sun takes just 88 days – compare our Earth takes one year around the Sun in 365 days; just over four times around the Sun as Earth around once.
  • twice during Mercury orbit – it gets very close to the Sun and speeds up so much that our Sun seems to go backwards in the Sky.
  • Mercury rotates once every 58.65 days (nearly 59 days) – the time between one sunrise and the next is 176 days.

Day and Night on Mercury

  • temperatures change from -180ºc at night to more than 430ºc during the day (hot enough to melt lead metal.)
  • the crust and mantle are made largely of rock, but the core (75% of the core’s diameter is solid iron.)


  • Mercury’s dusty surface is pocked by craters made by space debris crashing onto it.
  • with 6% of Earth’s mass, Mercury is so small that its gravity can only hold on a very thin atmosphere.
  • Mercury is so small that Mercury’s core has cooled and become solid (not the same as our Earth’s core) – as happened, Mercury shrunk and its surface wrinkled.

Mercury’s crust


  • Craters on Mercury discovered by USA’s Mariner 10 space probe have names such as Bach, Beethoven, Wagner, Shakespeare and Tolstoy.
  • discovered in 1974; the largest feature on Mercury is a huge impact crater – it called the Caloris Basin – around 810 miles across and 1¼ miles deep.

Mercury Crater:- Caloris Basin


Transits of Mercury

Across the Sun takes place when the planet Mercury passes directly between the Sun
and a superior planet, becoming visible against the Sun,
also occurs just once every eight years on average.

Next Transit of Mercury for the UK Observers

  • 2003 Transit of Mercury in the UK  (Wednesday 7th May 2003.)
  • 2016  Transit of Mercury in the UK  (Monday 9th May 2016)
  • 2019  Transit of Mercury in the UK  (Monday 11th November 2019)
  • 2032  Transit of Mercury in the UK  (Sunday 7th November 2032)
  • 2039  Transit of Mercury in the UK  (Saturday 7th May 2039)


Back to  The Solar System  /  The Planets  /  Planets to the edge of the Oort Cloud page / next to  Venus  page.

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