Question

Why do we think the inner (terrestrial) planets became more dense than the outer planets

a. The sun's gravity pulled denser materials toward the center

b. The inner nebula was so hot that only metals and rocks were able to condense

c. In the collapsing solar nebula, denser materials sank toward the center

d. The rotating disk in which the planets formed spun lighter elements outward by centrifugal force

Answer 1

The densest materials on the terrestrial planets sink toward the center, creating a core of dense metals. This is due to the pull of gravity on the heavier elements. The terrestrial planets were likely molten at some point in the past.

Step-by-step explanation:

When we look at the internal structure of each of the terrestrial planets, we find that the densest metals are in a central core, with the lighter silicates near the surface. If these planets were liquid, like the giant planets, we could understand this effect as the result of the sinking of heavier elements due to the pull of gravity. This leads us to conclude that, although the terrestrial planets are solid today, at one time they must have been hot enough to melt.