Mercury
Pluto
Diameterkm
4,879
2,377
Mass (Earth = 1)x
0.06
0.00
Surface Gravitym/s²
3.70
0.62
Mean Temperature°C
+167
-230
Distance from SunAU
0.39
39.48
Orbital Perioddays
87.97
90,560
Day Lengthhours
4222.60
153.29
Known Moons
0
5
Axial Tilt°
0.03
122.53
Orbital Velocitykm/s
47.36
4.67
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.
Pluto
- -Pluto was reclassified from planet to dwarf planet in 2006 by the International Astronomical Union.
- -Pluto's largest moon Charon is so large (half Pluto's diameter) that they orbit a point between them, forming a binary system.
- -Pluto's famous heart-shaped feature, Sputnik Planitia, is a vast plain of nitrogen ice over 1,000 km across.
- -One year on Pluto takes 248 Earth years -- it hasn't completed a single orbit since its discovery in 1930.