Which type of planet is Jupiter's moon Io? You are able to measure the diameter of the Moon to be about 3640km By watching the way a spaceship is attracted to it, you determine that its mass is 8.89x1022kg.
We can figure out what type of planet it is based on it's density. Density is mass per unit volume. Mass is 8.89x1022kg or 8.89x1025g. Volume can be estimated assuming that Io is roughly spherical. The formula for the volume of a sphere is 4/3 times pi times radius cubed. The radius = 1820km or 1.82x108cm. pi = 3.14159. The volume = 2.53x1025cm3. Mass/Volume = 3.5g/cc, which is in the density range of the rocky (terrestrial) planets.
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