Mercury Fact File


Planetary Fact Files
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The planet closest to the Sun, is also the smallest within our Solar System

It is likened to our moon for colour and appearance. However, the planet has the second highest density in the solar system (only Earth is denser).

Mercury's size means it has a very thin atmosphere, so does not absorb as much heat from the sun as Venus.

A year on Mercury (the time it takes to complete a full orbit of the sun) is only 88 Earth days long.

One interesting fact is that Mercury does a full rotation on its axis in 58.67 Earth days, yet its day and night cycle takes 176 Earth days to complete because the planet rotates in the opposite direction to it's orbit of the sun.

Mercury is one of the four terrestrial planets in our solar system, meaning it is made up mostly of rocks and/or metals

MESSENGER probe image of Mercury


It is very hard to get exploration equipment to Mercury. It's proximity (closeness) to the sun makes any orbits of the planet unstable. Also, additional speed is required for the crafts to navigate to the planet rather than being pulled directly into the Sun.

The image shown above, and most other mapping information is as a result of NASA's MESSENGER probe which maintained orbit of the planet from 2011 until 2015

On 20th October 2018, a new mission (BepiColombo) was launched towards Mercury. This mission involves two seperate orbiting probes from the ESA (European Space Agency) and JAXA (Japan Aerospace Exploration Agency), these are due to reach Mercury in December 2025. Researchers at Aberystwyth University have been working with the ESA for this mission, providing predictive surface and exosphere modelling.


Use the information above to answer these questions:

  1. Why is the surface temperature of Venus higher than Mercury's?
  2. How many Mercury years are in five Earth years?
  3. Why does Mercury have no moons?
  4. Based on our current understanding, why can Mercury not support life?


To check your answers please see the answer sheet. This should only be used after attempting all questions.

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