File:Io_highest_resolution_natural_color.png · Wikimedia Commons · See Wikimedia Commons

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Io

Also known as Jupiter I, Io (moon)

innermost of the 4 Galilean moons of Jupiter

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Io is the innermost of Jupiter's four largest moons, discovered by Galileo in the early 1600s. It is scientifically significant because it is the most volcanically active body in our solar system, with hundreds of active volcanoes driven by intense internal heating.

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Wikidata facts

Area: 41910000
Diameter: 3660
Radius: 1821.6
Mass: 89.296
Orbital period: 1.769137786
Image: Image of Io from Juno JunoCam from December 2023.png

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time of discovery or invention: 1610-01-08
Commons category: Io (moon)
Commons gallery: Io
periapsis: 420000
apoapsis: 423400
orbital eccentricity: 0.0041
volume as quantity: 2530000000
density: 3.528
albedo: 0.63
apparent magnitude: 5.02
semi-major axis of an orbit: 421800
temperature: 130
orbital inclination: 2.213
surface gravity: 1.796
provisional designation: Jupiter I

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Apparent magnitude 5.02 (opposition) Angular diameter 1.2 arcseconds Atmosphere Surface pressure 0.5 to 4 mPa (4.93×10 to 3.95×10 atm) Composition by volume90% sulfur dioxide

Io (/ˈaɪ.oʊ/) is the innermost and second-smallest of the four Galilean moons of Jupiter. Slightly larger than Earth's Moon, Io is the fourth-largest natural satellite in the Solar System, has the highest density and strongest surface gravity of any natural satellite, and the lowest amount of water by atomic ratio of any known astronomical object in the Solar System.