Which Moon formation model posits that the Moon is a piece of Earth that split off early during the planet's formation?

Which Moon formation model posits that the Moon is a piece of Earth that split off early during the planet's formation?

• A. The Fission model
• B. The Capture model
• C. The Double-Impact model
• D. The Giant-Impact model

Answer: (A)

This question tests a Moon-formation idea in which the Moon originates from material that was once part of Earth itself. In the fission scenario, the young Earth was spinning so rapidly that material at the equator could be flung outward and shed as a separate body. That material would then coalesce into the Moon in orbit around Earth. Why this fits the description well: the Moon would be composed largely of Earth's mantle material, not a separate body formed elsewhere, so its rocks and chemistry would reflect Earth’s mantle characteristics and it would have only a small iron core, since the core of the Moon would come from the mantled material rather than core material from another object. The other models describe the Moon forming from material outside Earth—either being captured by Earth's gravity or arising from debris produced by a colossal impact with another body. Those scenarios involve external material rather than a chunk that split off from Earth, which is why the fission model is the best match for this description.

This question tests a Moon-formation idea in which the Moon originates from material that was once part of Earth itself. In the fission scenario, the young Earth was spinning so rapidly that material at the equator could be flung outward and shed as a separate body. That material would then coalesce into the Moon in orbit around Earth.

Why this fits the description well: the Moon would be composed largely of Earth's mantle material, not a separate body formed elsewhere, so its rocks and chemistry would reflect Earth’s mantle characteristics and it would have only a small iron core, since the core of the Moon would come from the mantled material rather than core material from another object. The other models describe the Moon forming from material outside Earth—either being captured by Earth's gravity or arising from debris produced by a colossal impact with another body. Those scenarios involve external material rather than a chunk that split off from Earth, which is why the fission model is the best match for this description.