'Giant impact' theory of moon's formation gets another boost


Oct 22, 2019
The space.com report states "Shortly after the mammoth collision occurred, Earth was just able to stay together while pieces of both planets that were blasted into space coalesced to form the moon. Both of these blobby bodies had a mix of light and heavy chlorine isotopes at first, but that mix began to change as Earth's gravity pulled on the newly forming moon."

My observation, a great deal of Theia original chemical composition and the proto-Earth is required to be known in the giant impact model to explain such chemical differences. Oxygen isotopes must be explained that Theia and the proto-Earth had a similar chemical composition when they formed in the protoplanetary disks, Oxygen Isotopes and the Moon-Forming Giant Impact, https://ui.adsabs.harvard.edu/abs/2001Sci...294..345W/abstract, October 2001. Theia elements are not yet identified in lunar rocks, Identification of the giant impactor Theia in lunar rocks, https://ui.adsabs.harvard.edu/abs/2014Sci...344.1146H/abstract, June 2014

Carbon in the Moon is a problem too for Theia impact, "The findings by the researchers suggest that the moon has a large amount of ancient carbon beneath its surface, and it has likely been there since the moon was formed. How it could have persisted on a very hot early moon remains a mystery.", Carbon emissions on the moon put theory of moon birth in doubt, https://phys.org/news/2020-05-carbon-emissions-moon-theory-birth.html

Metal content differences cause problems too, Higher concentration of metal in Moon's craters provides new insights to its origin, https://phys.org/news/2020-07-higher-metal-moon-craters-insights.html

The giant impact model is the only game in town now it seems but studies continue. I note that the Moon forms after Theia impact near 3 earth radii and moves out to some 10 earth radii over a short period of time. However, testing and showing the Moon actually orbited Earth so close has not been done.
Mar 5, 2020
I doubt if more than 2% of the recovered moonrocks are more than 3 billion years old. Likely about 50% of Houston’s moon rocks are around 300 million years old or less.

Ordinary surface bombardment will liberate a higher number of lighter isotopes than heavier isotopes. Chlorine vaporizes at a low temperature and the lighter isotopes will have a higher velocity so they will have a higher probability of reaching lunar escape velocity.

This study is a nothing burger. The surface material is pretty worthless for determining the moon’s bulk isotopic properties.

When will Houston publish the Uranium content and isotopic composition of the Lunar KREEP component? Houston does not publish this data since it would look a lot like the Uranium signature in black shale (the source rock for oil). The heavier uranium isotopes found in black shale are a marker for a very high energy event which blasted the lighter uranium isotopes from the Earth’s surface. That event was likely an interstellar asteroid impact since higher impact velocities equate to higher energies and impact temperatures.
Apr 7, 2020
It’s really hard to see any other way it could have happened. The details still need hashed out but as of now this theory is the only game in town.