Earth's 2 Moons? It's Not Lunacy, But New Theory

[Snaploud]

Interesting new theory:

Earth's 2 Moons? It's Not Lunacy, But New Theory


SETH BORENSTEIN 08/ 3/11 03:26 PM ET

WASHINGTON — In a spectacle that might have beguiled poets, lovers and songwriters if only they had been around to see it, Earth once had two moons, astronomers now think. But the smaller one smashed into the other in what is being called the "big splat."


The result: Our planet was left with a single bulked-up and ever-so-slightly lopsided moon.


The astronomers came up with the scenario to explain why the moon's far side is so much more hilly than the one that is always facing Earth.


The theory, outlined Wednesday in the journal Nature, comes complete with computer model runs showing how it might have happened and an illustration that looks like the bigger moon getting a pie in the face.


Outside experts said the idea makes sense, but they aren't completely sold yet.


http://www.huffingtonpost.com/2011/08/03/earth-two-moons-theory_n_917464.html

 

[YellowSubmarine]

Earth may have had two moons

Now, first forget about the details, the picture depicting how the second moon might have disappeared at the top of the article is stunning:

http://www.space.com/12529-earth-2-moons-collision-moon-formation.html

Anyway, a summary: The surface of the far side of the moon that is completely unlike our side might be explained by another small moon that once existed but then crashed on the far side.

I always found it really startling how different the rest of the surface was compared to the one that we see, not only as composition, but visually – it's unexpected as if you're viewing a different celestial body. Pity I haven't been born when the first pictures of it have been made.

 

[Skywalker]

Good grief. They'll give anything a sequel these days.

 

[Bill Morris]

Do you suppose the side facing us had a few asteroids intercepted by the big blue planet, while the other side had no asteroid thief and ended up collecting a few more?

 

[YellowSubmarine]

Do you suppose the side facing us had a few asteroids intercepted by the big blue planet, while the other side had no asteroid thief and ended up collecting a few more?

That's the first thing that comes to mind when you see the difference. It seems to be a big coincidence how the biggest contrast occurs when you place the moon exactly as it is, so it's somehow hard to believe that the Earth is not to blame. And why would the other moon hit our moon exactly at the centre of the far side? There are so much more other spots, you know.

I personally like this explanation more though.

 

[Saquist]

The Earth small body collisioin didn't make a lot of sense to me because I think the Earth condensed the oceans itself...a collision would have boiled all that away in the early going. Scientist wanted to fit this idea by suposing the ocean came gradually from bombardment but no other inner planet has a vast ocean like Earth

 

[Finn]

^ That's a poor logic. This would have taken place long before there were oceans.

 

[Bill Morris]

The moon became tidally locked (always facing Earth) quite early in its history, back in the time when there were plenty of pebbles to clear out of the Earth-moon path, billions of years ago, and that's when the small umbrella that Earth provided one side of the moon would have made the most difference in accretion between the near and far sides of the moon. But a few did strike Earth after the oceans formed. Some still do today, with the majority of meteorites diving into the briny.

 

[Cmdr_Blop]

I say we bring the Moon here, and find out directly:

[yt]http://www.youtube.com/watch?v=1Y2NxDG_RWQ[/yt]

 

[Ronald Held]

I would have to read the article before passing judgement.

 

[Captain Craig]

Isn't there a theory that says the moon could've been formed in conjunction with the Earth?
Or another that says an asteroid hit the Earth causing enough matter to eject and form the moon.

If either of these are legit then what is/was the second moon? A captured celestial body? Could you add it into either of the above theories?

 

[Asbo Zaprudder]

Isn't there a theory that says the moon could've been formed in conjunction with the Earth?
Or another that says an asteroid hit the Earth causing enough matter to eject and form the moon.

If either of these are legit then what is/was the second moon? A captured celestial body? Could you add it into either of the above theories?

It's an extension of the scenario where a Mars-sized body collided with the early Earth. I wonder if this latest hypothesis would mean that the South Pole-Aitken Basin would have to have been formed after the slow splash event. It certainly didn't infill with lava like the near-side basins. I'm also wondering how the distribution of hydrated minerals would be affected as recent analysis seems to indicate that there's a lot more water in lunar rocks than previously thought.

 

[MLJames]

Isn't there a theory that says the moon could've been formed in conjunction with the Earth?
Or another that says an asteroid hit the Earth causing enough matter to eject and form the moon.

If either of these are legit then what is/was the second moon? A captured celestial body? Could you add it into either of the above theories?

The simultaneous formation theory was one of the older theories for the moon's formation, and it has a number of problems. If it formed at the same time out of the same cloud of materials that the Earth did it should either a) have the same composition as the Earth (which it doesn't), or b) not be there at all, since the Earth's greater gravity would have sucked in the stuff that would have formed the moon.

Some years ago Discovery had a program called "If We Had No Moon" (narrated by Patrick Stewart), which went into detail on how the Giant Impact theory of the moon's formation came to be. One of the scientists interviewed for the show said that a sizeable chunk of the scenarios she ran on the computer produced two moons instead of one. This wasn't stable in the long run; eventually the two would collide.

 

[spooky spice]

that was no moon

 

[RoJoHen]

This wasn't stable in the long run; eventually the two would collide.

Maybe they did!

 

[Saquist]

^ That's a poor logic. This would have taken place long before there were oceans.

It's really unclear when they think the impact happened in that theory. they usually just say a Young Earth and a Mars sized planet but their is no evidence that earth ever had the magma ocean...

Most of these theories are so theoretical it's nothing more than conjecture because the amount of evidence is sparse. We have no idea where oceans come from and when. I'm inclined to believe that Earth always had the oceans.

I look at Mars and Venus and if comets really did bring the oceans to the inner solar system to that degree then they should have oceans too. yes there are intervening circumstances for each but it's hard to really just trust the theory when Earth is the only real example in the entire solar system of oceans. Adversely ice is everywhere in the solar system but there isn't much agreement in all these theories at all. I tend to take them with cup of salt.

 

[sojourner]

^Who says Venus and Mars never had oceans?? Now, currently due to different circumstances, both appear pretty dry, but that's not really the case. Heck, Venus has huge oceans. Their just all evaporated.

 

[Wanderlust]

The oceans acreated with the Earth and were outgassed when the Earth cooled. Only a small fraction though, since the mantle has around 10x as much water locked inside of it than on the surface.

Mars had a huge ocean at the beginning, it was lost when the magnetic field shut down and the atmosphere withered away. Pretty much all bodies had water that came with the initial formation, but Venus and mars lost it due to adverse conditions. There still is probably a large amount of water on Venus trapped in the mantle. Same with Mars.

 

[Pavonis]

^ Actually, we don't know how much water is stored in the mantle. We know how much water the minerals of the mantle are capable of storing when saturated, but we don't know that the mantle is actually saturated. It's non-trivial to deconvolve the effects of water content, temperature, and composition on seismic signals. It's an area of active research.

 

[Saquist]

^Who says Venus and Mars never had oceans?? Now, currently due to different circumstances, both appear pretty dry, but that's not really the case. Heck, Venus has huge oceans. Their just all evaporated.

We don't know if their were oceans on either of those planets. we know there was water though. But Mars is a good point. They suspect that the planet was struck by an object 2/3 the size of moon. It's likely the reason Mars has no water right now. And there is a question of whether Mars really ever had any where near relationally the amount of water Earth has.

If the thin crust theory on Venus is true then it never had oceans at all.