The Earth-Moon-Theia hypothesis

[Brian G Turner]

A fascinating article on the BBC about how some scientists think they have found a way to identify Theia's footprint:
BBC News - Traces of another world found on the Moon

Researchers have found evidence of the world that crashed into the Earth billions of years ago to form the Moon.

Analysis of lunar rock brought back by Apollo astronauts shows traces of the "planet" called Theia.

The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision.

The study has been published in the journal Science.

The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia 4.5 billion years ago.

Theia was named after a goddess in Greek mythology who was said to be the mother of Selene, goddess of the Moon. It is thought to have disintegrated on impact with the resulting debris mingling with that from the Earth and coalescing into the Moon.

It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no-one had found any evidence of Theia in lunar rock samples.

Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia.

 

[Dozmonic]

It's a theory that always made sense to me. The Pacific covers a third of the planet and is a pretty deep wound

 

[HareBrain]

The Pacific covers a third of the planet and is a pretty deep wound

The ocean floor stabilised much later than this event, surely? In any case, until 300m years ago the "pacific" was pretty much the whole earth, with the single ocean Panthalassa surrounding the single supercontinent Pangea.

 

[Stephen Palmer]

All true, HareBrain.

The Theia thing happened about 4.7 billion years ago - we've had any number of tectonic revolutions since then. See also Ted Nield's fantastic book Supercontinent - highly recommended.

 

[Brian G Turner]

Just following this up with a couple of later articles - one of which dismisses the claim of finding isotrope differences in the original article, but does suggest this means that Earth and Theia must have had a head-on collision: Moon was produced by head-on collision between Earth and forming planet – Astronomy Now

This later piece talks about how the Earth could have gone into a mad spin - a full rotation every 2 hours - due to the impact, as part of explaining why the moon is angled 5% from the plane of Earth's equator: Did early Earth spin on its side? – Astronomy Now

 

[Alexa]

I'm still confused how can someone afirm they have proof of another world on the Moon and call this research. Sorry Brian, but I'm skeptical about this one.

 

[Brian G Turner]

And another article on this: Earth was smashed by a rock the size of Mars to make the moon

 

[Alexa]

And that was probably the best event for our planet. Without the Moon we would probably not be here talking about it.