Why Is It That Terrestrial Planets Are Thought to Have

question 605

Multiple Choice

Why is it that terrestrial planets are thought to have dense iron cores?

• A) Thermonuclear reactions produced iron as a fusion product in the earlier phases of planetary evolution (thermonuclear accretion).
• B) During the formation of the planets, heavy elements accumulated first, followed by the accretion of lighter elements onto them (bimodal accretion).
• C) The planets were molten early in their life, and the heavy elements sank and lighter materials floated to the surface (planetary differentiation).
• D) Magnetism in the iron was sufficiently powerful to pull iron atoms to the center as the planet formed (magnetic sorting).