Geochemical arguments for an Earth-like Moon-forming impactor.

Area of Science:

• Geochemistry
• Planetary Science
• Cosmochemistry

Background:

• Earth's building blocks likely originated from a uniform inner protoplanetary disc.
• Enstatite meteorites share isotopic similarities with Earth but have distinct chemical evolutions.
• No single chondrite type perfectly represents Earth's accretionary material.

Purpose of the Study:

• Investigate the isotopic and chemical composition of Earth's building blocks.
• Explain the isotopic similarities between lunar and terrestrial rocks.
• Determine the origin of heavy silicon isotope values in the Earth-Moon system.

Main Methods:

• Analysis of geochemical and isotopic data from meteorites, lunar, and terrestrial samples.
• Modeling of giant impact scenarios for Moon formation.
• Application of an inversion method to calculate Hf/W ratios and W isotopes.

Main Results:

• Earth and enstatite meteorites originated from the same nebular reservoir but evolved differently.
• Isotopic similarities between Moon and Earth are attributed to a common origin of the Moon-forming impactor.
• Heavy silicon isotope values may result from nebular fractionation, not core partitioning.
• Tungsten isotopic similarity can be explained by a giant impact involving embryos with different accretion histories.

Conclusions:

• Earth's accretion material was isotopically uniform, similar to enstatite chondrites.
• The Moon-forming impactor shared the same isotopic composition as Earth.
• Silicon isotope variations are likely due to nebular processes.
• Tungsten isotope similarities support a specific giant impact model for Moon formation.