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The swift messenger
Mercury is the smallest planet in our solar system and the closest to the Sun. Despite being closest to the Sun, it is not the hottest planet (Venus holds that title). Mercury has virtually no atmosphere to retain heat, causing extreme temperature swings between its day and night sides. Its surface is heavily cratered, resembling Earth's Moon, and it has a surprisingly large iron core that takes up about 75% of its radius.
Day Length
4,222.6h
175.9x Earth days
Year Length
87.97d
0.24x Earth years
Avg Temperature
167°C
-180° to 430°C
Moons
0
No rings
No Solid Surface
Radius
2,439.7 km
Mass
3.301 x 10^23
Surface Gravity
3.7 m/s²
Escape Velocity
4.25 km/s
Rotation Speed
10.89 km/h
Orbital Speed
47.87 km/s
Distance from Sun
57.9 million
Composition
Iron core (75%), silicate mantle and crust
~90 seconds without a spacesuit
Surface temperature of 167°C would be instantly lethal. There is no solid surface to stand on.
A day on Mercury (sunrise to sunrise) lasts 176 Earth days
Mercury is shrinking as its iron core cools
It has ice in permanently shadowed craters at its poles
Mercury has no moons or rings