Samples from the Apollo mission support an intriguing new theory for how the Moon formed called the “Giant Impact Hypothesis”
How Did the Moon Come to Be?
Published: July 16, 2019
Katie Joy: There were several theories for how the moon was first formed. One is the “capture” theory, whereby the moon was actually thought to be an early planet that got captured by Earth’s gravity and went into orbit around it.
There’s also a slightly strange idea that maybe the early Earth is spinning really fast on its axis and spun off a piece of the moon. And this is what we call the “fission hypothesis.”
However, our ideas have changed since we collected the Apollo samples. The samples told us that, actually, the moon and the earth are chemically similar. And this gave rise to this new model, called the “giant impact hypothesis.”
We’re still figuring out the details, but maybe the earth was hit by a body the size of Mars, creating a massive shower of super-heated material: gas, dust, magma that then cooled down slowly and coalesced, forming the earth at the center and the moon trapped in orbit around it.
Back to the Moon
Executive Producers for Bigger Bang: Iain Riddick & Ben Bowie
Produced by: Christopher Riley
Digital Production: Rachel Swansburg
© WGBH Educational Foundation 2019