20 Facts About Mercury

1. Circumference at Equator: 15,329.1 km.

2. Mass: 330,104,000,000,000 billion kg (0.055 x Earth).

3. Average Distance from Sun: 57,909,227 km (0.39 AU).

4. Known Satellites: None.

5. Notable Satellites: None.                 

6. Length of Orbit: 87.97 Earth days.

7. Surface Temperature: -173 to 427°C.

8. For every two orbits of the Sun Mercury completes three rotations about its axis and up until 1965 it

was thought that the same side of Mercury constantly faced the Sun.                                                                                     
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9. Thirteen times a century Mercury can be observed from Earth passing across the face of the Sun in an

event called a transit, the next will occur on the 9th May 2016.                                                                                                                                                                  

10. Mercury is almost the densest planet in the solar system and is second only to Earth.

11. The largest known crater on Mercury, the Caloris Basin, has a diameter of 1,550 km.

12. As of 2012 Mariner 10 and MESSENGER are the only two spacecraft to have visited Mercury.

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13. It is estimated Mercury’s core makes up 42% of its volume, for comparison Earth’s core makes up 17%.

14. Mercury has the highest orbital eccentricity of all the planets with its distance from the Sun ranging

from 46 to 70 million km.   

15. While Mercury has at atmosphere it is constantly being stripped and replenished.

16. Mercury is named after the Roman messenger to the gods

17. Before the first space-crafts flew to Mercury to take pictures of its surface, some astronomers believed that the planet would have a smooth surface. When Mariner 10 took pictures of Mercury during its flyby of Venus and Mercury in November 1973, scientists discovered that Mercury is the most cratered planet in the Solar System with a surface similar to Earth's Moon.                                                                                                                     Source

18. Mercury has no atmosphere at all. Sunlight reflects off its surface, similar to how light is reflected directly off the Moon's surface. The lack of atmosphere means that sunlight cannot be spread through the atmosphere. The planet's sky is dark, just like the Moon's and, if you were able to stand on the side of the planet not facing the Sun, you would be able to see billions of stars in the sky.

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19. Mercury can only be seen just after the Sun has risen and just before the sun sets.

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