This may change everything … or at least some widely-accepted theories about how the Earth’s moon was made. Scientists using state-of-the-art equipment and moon rock samples have determined that the Moon was created when a still-forming planet crashed head-on with it – vaporizing the baby planet and knocking out the chunk that became the Moon. How big is this discovery?
The prevailing theory on the Moon's birth takes us back 4.5 billion years. The still-young Earth (100 million years old) was believed to have received a glancing blow from an even younger, still-forming planet called Theia. That hit smashed Theia into chunks, one of which became the Moon. Previous research seemed to confirm this … until now.
According to a new report in the journal Science, a team of geochemists working at UCLA compared seven lunar rocks from the Apollo 12, 15 and 17 missions with five volcanic rocks from Hawaii and one from Arizona. Using instruments not available before, including UCLA's new mass spectrometer, they focused on the oxygen atoms that make up 50 percent of the weight and 90 percent of the volume of a rock. Both the moon and the Earth rocks were primarily O-16 oxygen – made of eight protons and eight neutrons – with traces of the isotopes O-17 (one extra neutron) and O-18 (two extra neutrons).
Knowing that each planet in the solar system has a unique O-16-to-O-17 ration, they compared Earth’s to the Moon and found …
We don't see any difference between the Earth's and the moon's oxygen isotopes; they're indistinguishable.
That’s Edward Young, lead author of the study and a UCLA professor of geochemistry and cosmochemistry. The ratios would have been different if the Moon was made primarily of Theia. What happened to the other
vehicle planet in this accident, Dr. Young?
Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them. This explains why we don't see a different signature of Theia in the moon versus the Earth.
Young estimates that Theia was about the size of Earth, so that was some massive collision.
To put this another way - Earth was a chuck of chocolate ...
... and Theia was a blob of peanut butter.
Instead of a chuck of chocolate orbited by peanut butter fudge ...
... the collision created two Reese’s peanut butter cups.
If this ruined your diet, blame Theia.