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The Planet Mercury Fact Sheet


Mercury is the first planet in our solar system and the closest to the sun. It completes a rotation around the sun in just 88 days while it takes the Earth 365 days. Wow that means that for every year we have here on Earth four years goes by on Mercury! That's probably why Mercury was named after the Roman god of speed.

Although it's fast it also happens to be the second smallest planet in our Solar System after Pluto, the most distant planet. Mercury is so small and so close to the sun that it is almost impossible to see. With telescopes, just after dawn or before sunset, the planet can be seen as a small spot in front of the Sun's surface. Mercury's surface also looks a lot like our Moon's, because It's covered in craters.

Life on Mercury is impossible. Temperatures on the planet can be extremely hot or extremely cold depending on which side of it is facing the Sun (From 375c to -200c). Mercury spins on its axis very slowly, so one side of the planet can be in complete frozen darkness for days. The planet is also very heavy for its size. Astronomers believe that it has a large iron core which may explain why the planet weighs so much.

Mercury, unlike the planet Earth, is a geologically dead planet. This means that the surface shows no sign of volcanic activity or any other form of geological activity. It is for this reason that astronomers believe Mercury's core to be extremely cold. Earth on the other hand is a geologically living planet. Its continents still move, and hot lava is churned out of its core through volcanic eruptions and of course there is life on Earth!

Some Mercury Quick Facts

  • Most astronomers believed that Mercury would have a smooth surface before the first space-crafts flew to the planet. When Mariner 10 took pictures of Mercury, scientists soon discovered that Mercury was not a smooth surfaced planet at all. Actually it turned out to be the most cratered planet in the Solar System!


  • Mercury has no atmosphere at all which causes sunlight to reflect off its surface. This is very similar to how light reflects directly off our Moon's surface. Mercury's lack of atmosphere also means that sunlight isn't spread through the atmosphere, so the planet's sky is dark.


  • Mercury (4,878km wide) is slightly bigger than Earth's Moon (3475.6km wide).


  • Mercury can only be seen just after the Sun has risen and just before the sun sets, because it's so close to the sun.


  • If you were to stand on Mercury, the Sun would appear two and a half times bigger than it appears on Earth.


  • Mercury is about 100 times closer to the Sun than Pluto, the most distant planet in the Solar System.


  • Mercury's fast speed is caused by the Sun's strong gravitational pull. Hold a short piece of string with something tied to the end of it and spin it around. Try it again with a longer piece of string. Notice how much longer it takes for the object tied to the end of it to spin round. Your finger acts like the Sun, and the object acts like a planet orbiting the Sun.


  • Despite being the closest planet to the Sun, Mercury is not the warmest. Venus is warmer. In fact, Mercury can be one of the coldest planets in the Solar System, because it has no atmosphere to keep the sun's warmth in.


  • Printable Version of Mercury Facts Sheet


    Learn More About The Rest of The Planets:


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