In the four terrestrial planets, the densest, heaviest materials are at the center and not evenly distributed throughout the planet. Scientists interpret this observation to mean that:
A) the four terrestrial planets must once have been inside the Sun
B) the four terrestrial planets must once have been hot enough to be molten (like a liquid)
C) the four terrestrial planets must have formed where Jupiter and Saturn now are
D) the four terrestrial planets must have collided with each other many times
E) none of the above

Question

Quizplus · Accepted Answer

The fact that the densest, heaviest materials are at the center of the terrestrial planets suggests that they formed by differentiation, where the lighter materials rose to the surface and the denser materials sank to the core. This process requires the planet to have been hot enough to be molten, which is option B. Option A is incorrect; the planets did not start inside the Sun. Option C is incorrect; the terrestrial planets formed much closer to the Sun than Jupiter and Saturn. Option D is also incorrect; while the terrestrial planets may have experienced impacts early in their history, this is not the cause of their differentiated interiors.

In the Four Terrestrial Planets, the Densest, Heaviest Materials Are