How did Earth form?

• A. Earth formed from dust and gas in the solar nebula, eventually leading to the aggregation of materials into Earth.
• B. Earth formed after a collision with Mars destroyed Earth.
• C. Earth formed by accreting from comets only.
• D. Earth formed from a single giant rock that split.

Answer: (A)

Earth formed through accretion in the solar nebula. In the early solar system, dust and gas in a rotating disk cooled and condensed into solid particles. These particles stuck together, grew into planetesimals, and then merged into larger protoplanets. In the inner region, rocky material accumulated to build up a growing Earth-like body that differentiated into a metallic core and a rocky mantle, becoming a mature rocky planet. This fits the idea that Earth formed from the material in the solar nebula through aggregation of solids. The other scenarios don’t reflect how planets form: Earth wasn’t created by a collision with Mars destroying it; it didn’t form by accreting only from comets; and it didn’t originate from a single giant rock that split.