Pluto's density is 1.8 g/cm³. Iron has a density of about 5 g/cm³. Rock (e.g. basalt) has a density of about 3 g/cm³. Ice and water have densities of 1.0 g/cm³. Which of the following can be deduced from those densities? A) Pluto has a large iron-nickel core. B) Pluto is about one-third water and two-thirds rocky material. C) Pluto is solid rock all the way through. D) Pluto is composed entirely of water or water ice.

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Quizplus · Accepted Answer

Pluto's density (1.8 g/cm^3) is higher than that of ice/water (1.0 g/cm^3) but lower than that of rock (3.0 g/cm^3) and much lower than iron (5.0 g/cm^3). This suggests a composition that is a mix of materials less dense than rock but denser than ice, indicating a combination of water (or ice) and rocky material, rather than being composed mainly of iron or being entirely rock or water/ice.

Pluto's Density Is 1