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I know that the composition of planets is dependant on the equilibrium temperature at its orbit - for example, if below a certain temperature, water and other volatiles become solid, allowing them to accrete to form an ice planet or ice giant.

Is it possible for such an ice planet to be orbited by a moon of a different composition?

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  • $\begingroup$ Not a planet, but Io which is a mostly composed of silicate rocks and iron (unlike icy moons) orbits Jupiter. Even 92% of Europa is solid rock. $\endgroup$ Aug 5, 2021 at 6:40
  • $\begingroup$ A planet cannot orbit another planet as an object orbiting a planet is called a moon. As such the question is whether planet and moon can be of different composition. Our solar system shows: yes, they can. $\endgroup$ Aug 5, 2021 at 7:41
  • $\begingroup$ Perhaps you mean if a moon can be icy around a earth like planet. From the gravitational pov no problem, of course. About the formation of such a sistem we don't have example in the solar system. Or perhaps think of Jupiter. Though it is a gas giant, surely its inner part is something dense.... $\endgroup$
    – Alchimista
    Aug 5, 2021 at 10:53

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Uranus and Neptune would be primary known examples of ice giants. Miranda - Uranus moon. That density suggests a composition of more than 60% water ice. Though it is far rockier than its corresponding satellites in the Saturn system, indicating that heat from radioactive decay may have led to internal differentiation, allowing silicate rock and organic compounds to settle in its interior.

An ice planet is still a theoretical type of exoplanet

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  • $\begingroup$ Alternatively, Triton may qualify. Though the crust is a mixture of frozen nitrogen and water-ice, its core is solid making up two-thirds of Triton's mass. Its density is also high, which concludes that percentage of water-ice is around 15-35%. $\endgroup$ Aug 6, 2021 at 3:00

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