(inner-most and smallest planet in the solar system)
Mercury is the nearest solar system planet to the Sun
and the smallest.
- 0.055 Earth masses (about 4.5 × mass of the Moon).
- 0.38 Earth radii (about 1.4 Moon radii).
- 87 Earth days - orbital period.
- 176 Earth days - solar day.
- 0.39 AU - orbital radius.
- 0.206 - orbital eccentricity.
It has no moons.
It is a rocky planet with virtually no atmosphere, but has
a magnetic field that was not expected.
It was also thought to be tidally locked to rotate once
per orbit, but in fact rotates 1.5 times per orbit.
Two NASA spacecraft have visited: Mariner 10 flew by and MESSENGER
orbited it for over 10 years. A current ESA/JAXA mission,
BepiColombo was launched in 2018, aiming to reach Mercury in 2025.
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Referenced by pages:
equilibrium condensation model
equilibrium temperature (Teq)
late heavy bombardment (LHB)
moment of inertia factor
Solar Orbiter (SolO)