Earth, which is mostly rock and iron, has a density of 5515 kg/m³. Ganymede, Jupiter's largest satellite, contains much water and water ice and has a density of 1940 kg/m³. Io has a density of 3570 kg/m³. What conclusions have astronomers drawn from this? A) Io must be composed of some new material other than rocks, iron, water, or ice. B) Io is composed of compressed water and water ice. C) Io is mostly rock and iron, but because of its smaller mass it cannot compress the material as much as Earth can. D) Since Io is smaller than Earth, it is expected to have a smaller density regardless of composition.

Question

Quizplus · Accepted Answer

Io's higher density compared to Ganymede suggests it is composed mainly of heavier materials like rock and iron, rather than lighter materials like water and ice. Its density is less than Earth's, likely due to its smaller size and mass, which results in less gravitational compression of its materials.

Earth, Which Is Mostly Rock and Iron, Has a Density