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Mercury is the first and the smallest Planet in the Solar System. It is also the first of the four Terrestrial planets of our Solar System and the closest to the Sun. Mercury is very similar to our own Moon, it is gray and has a lot craters. However, Mercury is 1.4 times bigger than the Moon and it doesn't have any known natural satellite. Mercury is also the second hottest planet after Venus. Its the closest planet to the Sun and it's the second hottest planet in the Solar System. Its orbit around the Sun takes almost 87.97 days. The first recorded observation goes back to one millennium BC. Greek astronomers believed that it consisted of two objects: Apollo and Hermes. Hermes was only visible at evening twilight while Apollo was visible overday. Later the Romans called it Mercury, after their god of messengers.

Exploration of Mercury[]

There were two flyby missions from NASA: Mariner 10 and MESSENGER. MESSENGER made a fly-by of Mercury on 14 January 2008, to further investigate the observations made by Mariner 10 in 1975. A third mission, BepiColombo will carry two probes to Mercury. BepiColombo is an collaboration between Japan and ESA.

Atmosphere[]

Mercury's gravity is too weak to hold an atmosphere. However, there is a sort of 'exosphere' which holds: oxygen, sodium, hydrogen, helium and potassium. There are traces of argon, nitrogen, carbon dioxide, water vapor, xenon, krypton and neon. The source of these elements is still uncertain. However, scientists believe that the oxygen and helium is coming from the solar winds. The other elements come from evaporating volcanoes.

 The Solar System v·d·e 
Solar System XXVII
The Sun · Mercury · Venus · Earth · Mars · Ceres* · Jupiter · Saturn · Uranus · Neptune · Pluto* · Haumea* · Makemake* · Eris* · Dwarf Planet Candidates*
Planets · Dwarf Planets · Moons: Terran · Martian · Asteroidal

· Jovian · Saturnian · Uranian · Neptunian · Plutonian · Eridian

'Ceres * Pluto * Haumea * Makemake * Eris
Small bodies:   Meteoroids · Asteroids (Asteroid belt) · Centaurs · TNOs (Kuiper belt/Scattered disc) · Comets (Oort Cloud)
Hypothetical Bodies:   Vulcan · Planet 9 · Planet 10 · Tyche · Nibiru · Nemesis · more...
Planets with '*' are dwarf planets.
See also astronomical objects and the solar system's list of objects, sorted by radius or mass.
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