Mercury
Earth
Diameterkm
4,879
12,742
Mass (Earth = 1)x
0.06
1.00
Surface Gravitym/s²
3.70
9.81
Mean Temperature°C
+167
+15
Distance from SunAU
0.39
1.00
Orbital Perioddays
87.97
365.25
Day Lengthhours
4222.60
24.00
Known Moons
0
1
Axial Tilt°
0.03
23.44
Orbital Velocitykm/s
47.36
29.78
Quick Facts
Mercury
- -Mercury's day-night cycle lasts 176 Earth days -- longer than its year of 88 Earth days.
- -A person weighing 68 kg on Earth would weigh only 25.7 kg on Mercury.
- -Mercury has ice in permanently shadowed craters near its poles despite surface temperatures reaching 430°C.
- -Mercury is shrinking -- its circumference has decreased by about 14 km as its core slowly cools and contracts.
Earth
- -Earth is the only planet not named after a Greek or Roman deity.
- -Earth's rotation is gradually slowing -- days are getting about 1.4 milliseconds longer per century.
- -About 71% of Earth's surface is covered by water, but 96.5% of that water is in the oceans.
- -Earth's magnetic field has flipped its polarity hundreds of times over millions of years.