Facts about the third Moon from Jupiter Ganymede

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The largest moon of Jupiter is orbital resonance pattern because for every four orbits Io makes around Jupiter, Europa makes about two orbits and Ganymede about one.

Ganymede is larger than Mercury and Pluto, but is not considered a planet because it orbits Jupiter.  Pluto’s diameter is 2,360 kilometers),  Callisto’s diameter is 4821 kilometers, Io’s diameter is 3643 kilometers, and Europa’s diameter is 3122 kilometers.  Ganymede’s mass is 14.819x10^22 kilograms, Callisto’s mass is 10.8x10^22 kilograms, Io’s mass is 8.9x10^22 kilograms, and Europa’s mass is 4.8x10^22 kilograms.  Callisto is the farthest from the planet of the four Galilean moons.  Its orbit is 1,882,709 kilometers from Jupiter.  Ganymede’s orbit is 1,070,412 kilometers from Jupiter.  Europa’s orbit is 671,034 kilometers from Jupiter.  Io’s orbit is the closest to Jupiter at 421,700 kilometers. 

The orbital period (amount of time it takes each of the moons to orbit Jupiter) that causes the orbital resonance between three of the Galilean moons is 16.69 days for Callisto, 7 days 3 hours 41 minutes 45.6 seconds for Ganymede, 3.55 days for Europa, and 1.77 days for Io.  Callisto is not included in the orbital resonance. 

Ganymede is composed of silicate rocks and water ice.  The mantle may contain a layer of liquid water.  There are mountains, valleys, craters, and lava on the surface of Ganymede.  The Hubble satellite’s telescope discovered evidence that there might be oxygen in the atmosphere of Ganymede.  Galileo discovered that Ganymede has a magnetic field.  It is the first and only magnetic field discovered around a moon.  There is thought to be an ocean containing salt water below its surface.  This is evidence there might be life on Ganymede, but Europa is considered to be a better prospect for life because its ocean is much closer to its surface. 

Ganymede rotates on its axis every 9 hours 55 minutes 30 seconds.  This makes its day less than half of earth’s day.  The escape velocity is 2.741 kilometers per second.  The surface temperature is minus 163 degrees celsius.  It is the seventh of the known 63 moons of Jupiter counting from the closest.  Ganymede and the moon are the only two satellites that can be seen with the naked eye.       

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