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Difficulty: MediumAssessing Model Support and Contradiction

### Origin of the Moon

Three scientific models have been proposed to explain the origin of the Moon:

* Fission Model: The Moon was once part of the Earth but was thrown off early in the solar system's history due to the Earth's rapid rotation. Since it split directly from the young Earth's mantle, the Moon's chemical composition (such as oxygen isotope ratios) should be identical to Earth's mantle, and its orbit should lie along Earth's equatorial plane.
* Capture Model: The Moon formed independently elsewhere in the solar system, with its own unique composition, and was later captured by Earth's gravity during a close pass. This model suggests that the Moon's chemical composition should be distinct from Earth's.
* Giant Impact Model: A Mars-sized protoplanet collided with the young Earth. The impact blasted debris from both the protoplanet and Earth's outer mantle into orbit, which then accreted to form the Moon. Because the Moon formed from mantle debris, it should have a very low iron content compared to Earth, which retained its massive iron core.

Match each new scientific finding and the model evaluated to its correct relationship (whether the finding supports, contradicts, or has no effect on that model).

  • Finding: Lunar rock samples show oxygen isotope ratios that are completely identical to Earth's mantle. Model evaluated: Capture Model.Contradicts the evaluated model
  • Finding: Seismic data indicates the Moon's iron core constitutes less than 3% of its mass, while Earth's is 30%. Model evaluated: Giant Impact Model.Supports the evaluated model
  • Finding: The lunar surface is covered in a layer of regolith (rocky dust) created by meteorite impacts. Model evaluated: Fission Model.Has no effect on the evaluated model

Answer

The finding of identical oxygen isotope ratios contradicts the Capture Model; the finding of a tiny lunar iron core supports the Giant Impact Model; and the presence of impact regolith has no effect on the Fission Model.
The correct matches are determined by comparing each model's predictions with the empirical findings. The identical oxygen isotope ratios directly oppose the Capture Model's expectation of distinct compositions, representing a contradiction. The tiny iron core directly aligns with the Giant Impact Model's prediction of formation from iron-depleted mantle debris, representing support. The presence of impact regolith is a universal space weathering feature that does not depend on the formation mechanism, representing no effect.

Step-by-Step Solution

1
Evaluate the first finding against the Capture Model. The Capture Model predicts that the Moon and Earth should have distinct chemical compositions since they formed separately. Because the finding reveals that the oxygen isotope ratios are completely identical, this observation directly opposes the model's prediction, representing a contradiction.
Identical oxygen isotope ratios match with 'Contradicts the evaluated model' for the Capture Model.
To determine contradiction, identify if the observed data directly conflicts with the model's core predictions.
2
Evaluate the second finding against the Giant Impact Model. The Giant Impact Model posits that the Moon formed from rocky mantle materials blasted into space after Earth's core had already differentiated. This means the Moon should have very little iron. Finding a tiny iron core of less than 3% compared to Earth's 30% aligns with this prediction, representing support.
A tiny iron core matches with 'Supports the evaluated model' for the Giant Impact Model.
To determine support, identify if the physical observation aligns with the unique outcomes predicted by the model.
3
Evaluate the third finding against the Fission Model. The presence of regolith is a surface feature caused by ongoing meteorite impacts over billions of years. Since meteorite bombardment occurs on all atmosphere-free solar system bodies regardless of their original formation mechanism, this finding does not provide evidence for or against the Fission Model.
Meteorite-produced regolith matches with 'Has no effect on the evaluated model' for the Fission Model.
To determine neutrality, identify if the finding is an independent process that does not differentiate between the validity of the models.

Key Concept

Assessing how new empirical observations either support, contradict, or remain neutral toward proposed scientific models based on the models' core predictions.

Alternative Method

Draft a simple prediction table for each model (e.g., composition relative to Earth, core size) and match the observations directly to the predictions to quickly determine the relationship.
Estimated Time:2m 0s
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Topics

Assessing Model Support and Contradiction

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