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Solar System Exploration
Io: Facts & Figures
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Discovered By
Galileo Galilei
Date of Discovery
Orbit Size Around Jupiter (semi-major axis)
Metric: 421,800 km
English: 262,094 miles
Periapsis (closest)
Metric: 420,071 km
Apoapsis (farthest)
Metric: 423,529 km
Sidereal Orbit Period (Length of Year)
0.004843258 Earth years
1.769 Earth days
Orbit Circumference
Metric: 2,650,236.42 km
Average Orbit Velocity
Metric: 62,423.1 km/h
Orbit Eccentricity
Orbit Inclination
0.036 degree
Mean Radius
Metric: 1821.6 km
By Comparison: 1830 x 1818.7 x 1815.3 km, tri-axial
Equatorial Circumference
Metric: 11,445.5 km
Metric: 25,319,064,907 km3
Metric: 89,319,379,731,108,900,000,000 kg
Scientific Notation: 8.9319 x 1022 kg
Metric: 3.528 g/cm3
Surface Area
Metric: 41,698,064.74 km2
Surface Gravity
Metric: 1.796 m/s2
Escape Velocity
Metric: 8,552 km/h
English: 5,314 mph
Scientific Notation: 2376 m/s
Sidereal Rotation Period (Length of Day)
1.769 Earth days
42.456 hours
By Comparison: Synchronous with orbit period
Atmospheric Constituents
Sulfur dioxide
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Last Updated: 12 Aug 2013