The main evidence supporting the giant impact theory is the similarity between the isotopic composition of Earth and Moon rocks. Here are a few specific points of evidence:
1. Isotopic similarity: Oxygen isotopes from Moon samples brought back by the Apollo missions have the same ratios as those found on Earth. This suggests a common origin for both bodies, as the chance of two bodies forming with identical isotopic compositions independently is extremely low.
2. Lack of volatile elements on the Moon: The Moon has a much lower abundance of volatile elements, such as water and gases, compared to Earth. This is expected if the Moon formed from the debris of a giant impact that vaporized volatile elements.
3. Angular momentum: The Moon has a relatively large size compared to Earth's mass, which requires a transfer of angular momentum during formation. The impact theory explains this by suggesting that the collision between Earth and a Mars-sized object, often referred to as Theia, transferred angular momentum to the Moon and caused it to orbit around the Earth.
4. Chemical composition: The chemical composition of Moon rocks is similar to Earth's mantle, particularly in terms of the abundance of refractory elements like oxygen, calcium, and aluminum. This suggests that the Moon formed from the same materials as Earth's mantle.
5. Moon's orbital alignment: The Moon's orbit is nearly coplanar with Earth's equator, which aligns with the expectations from a giant impact scenario. The impact would have caused a disc of debris to form around Earth, which eventually accreted to form the Moon in the equatorial plane.
These lines of evidence support the idea that Earth and the Moon were once part of the same body, which was disrupted by a giant impact during the early stages of the solar system's formation.
Which evidence of the giant impact theory suggests that earth and the moon may have once been the same place
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1 answer