Pluto
Mercury
Diameterkm
2,377
4,879
Mass (Earth = 1)x
0.00
0.06
Surface Gravitym/s²
0.62
3.70
Mean Temperature°C
-230
+167
Distance from SunAU
39.48
0.39
Orbital Perioddays
90,560
87.97
Day Lengthhours
153.29
4222.60
Known Moons
5
0
Axial Tilt°
122.53
0.03
Orbital Velocitykm/s
4.67
47.36
Quick Facts
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.
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.