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- Ganymede is the largest moon of some 60 others orbiting Jupiter and the largest moon in the entire solar system. It is 52% larger than our Moon and twice as massive. Ganymede is 8% larger than the planet Mercury, but, only 45% the mass of Mercury.
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- Ganymede’s surface is mostly water-ice. However, some regions are dark and densely cratered. Other regions are light colored and have very few craters. These younger areas appear to result from up swelling of the liquid water or icy slush to the surface.
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- The long groves on the surface appear to be caused by erupting water through cracks in the surface. The water freezes, expands, creating the groves in the surface. Ganymede also has polar icecaps.
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- Ganymede has a magnetic field that varies with Jupiter’s rotation. It is the only moon known to have a magnetosphere.
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- There could be a liquid ocean beneath the surface of Ganymede. Tidal heating from Jupiter’s gravity and radioactive decay together could be enough heat to keep the liquid layer beneath the icy surface.
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- Ganymede has an aurora belt in each hemisphere just like Earth, which are created by their magnetic fields entering the poles.
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- Evidence shows us that Ganymede’s liquid ocean lies about 90 miles under the surface and extends 60 miles thick. The rotating ions ( electric charges ) in this liquid in motion due to Jupiter’s cycling gravity pull cold create this magnetic field.
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- It has a thin oxygen atmosphere with some hydrogen. The atomic oxygen was detected using the far ultraviolet wavelengths of 130.3 and 135.6 nanometers.
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- It is tidally locked facing Jupiter and is in orbital resonance with two other moons Europa and Io.
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- Ganymede’s density is 1.94 g/cm^3 which suggests this its composition is about half water ice and half rocky material. The rocky material is suspected to be and iron core with a silicate mantle. The Iron’s density is 5.5 g/cm^3 and the silicate’s is3.5 g/cm^3.
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- Comparing Ganymede with our Moon:
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---------------------- Ganymede ------- diameter ----- 3,274 miles
--------------------------------------------- orbit ---------- 7.155 days
---------------------------------------------- orbit -------- 665,114 miles
--------------------------------------------- mass --------- 14.82*10^22 kilograms
--------------------------------------------- density ------ 1.94 g/cm^3
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----------------------- Moon ----------- diameter ------- 2,160 miles
--------------------------------------------- orbit ---------- 27.332 days
---------------------------------------------- orbit -------- 238,855 miles
--------------------------------------------- mass --------- 7.349*10^22 kilograms
--------------------------------------------- density ------ 3.34 g/cm^3
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- Ganymede / Moon ratios:
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- Ganymede is 152% larger than our Moon.
- Ganymede has 2 times the mass, but,
- It’s density is only 58% as dense as the Moon.
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- Stay tuned - there is much more to learn.
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