Collision With Earth's "Little Sister" Created the Moon

astroengine writes The primordial planet believed to have smashed into baby Earth, creating a cloud of debris that eventually formed into the moon, was chemically a near-match to Earth, a new study shows. The finding, reported in this week's Nature, helps resolve a long-standing puzzle about why Earth and the moon are nearly twins in terms of composition. Computer models show that most of the material that formed the moon would have come from the shattered impactor, a planetary body referred to as Theia, which should have a slightly different isotopic makeup than Earth.

I Knew It!

[TechnoLuddite]

It was only a matter of time before Earth-Two [wikipedia.org] was discovered!

Re:

[Bigbuzzman]

Or Earth 2 [imdb.com].

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[StripedCow]

Another Earth (2011) [imdb.com]

Quite an interesting movie.

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[BoogieChile]

Little sister wouldn't do that anyway, she's too busy out in the back yard, playing like this [youtube.com]

Re:

[hcs_$reboot]

Or maybe the Moon was here first, and Earth crashed into it. So we're actually on the Moon, and the thing in the sky at night is actually Earth!

Kind of makes sense

[meglon]

....if both planetary bodies formed in the same area of the accretion disk.

Re:

[jbengt]

You got it backwards. They had been asking: If the moon was made by collision of two different planetary bodies, why are their compositions so similar to each other? Previous studies have indicated that mixing of the materials from the two bodies doesn't resolve the issue. Now a study has come out with simulations of solar system formation showing that a potential Thea and a potential Earth often have very similar compositions, therefore the similar composition is not inconsistent with the collision theo

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[Memnos]

And if the gravitational force of accreting Jupiter did not pul other bodies out of collisive orbits, in which case we wouldn't exist to talk about this, or anything else.

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[meglon]

I've always preferred a hybrid explanation for the event. Prior to the whole Theia hypothesis, one of the main ideas for the moons creation was it simply accreted with Earth as a binary planet system. The Theia hypothesis (man doesn't that sound like a good name for a sci-fi book) simply started off saying there was an impact and the moon was re-coalesced around the remaining Theian core from some of the ejecta.

That required, as you alluded to, that another planet/proto-planet was just kinda wandering

Re:

[Memnos]

Good point, and possibly a correct one (until I get my time machine's glitches fixed I can't offer a firm answer.) But the Earth (and by that I mean us) was a bit bit lucky. Too many collisions, life can't take hold. Too few, and likely the same result, but for different reasons, And we're "lucky" that one relatively recent collision did happen, perhaps some intelligent descendants of velociraptors might be having this discussion instead of us fragile mammals.

Another explanation

[Tablizer]

What about this explanation: a planetoid smashed into early Earth and split Earth into two. The two halves eventually smashed back together, but created the moon in the process. One "half" may have mixed more with the collider than the other due to the angle of impact, creating the slightly different isotopes in the parts of it that became the moon.

Re:Another explanation

[confused one]

Orbit is too circular for that solution to work.

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[garyisabusyguy]

There was a theory put out earlier this year about Jupiter 'roving' about the inner solar system and eliminating the super-earth that is seen in other solar systems
http://astronomynow.com/2015/0... [astronomynow.com]

Is there any correlation between these two theories?
Like Jupiter breaking up an earlier Super Earth, and then the remnants of that larger world becoming the Earth and Moon...

Is there any chance of Jupiter having drug the leftovers into a more distant orbit and forming the asteroid belt with them?

Earth/Theia not Earth/Moon ?

[perpenso]

Like Jupiter breaking up an earlier Super Earth, and then the remnants of that larger world becoming the Earth and Moon

Or perhaps Earth and Theia.

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[Billly Gates]

The general theory is the early Jupiter or Saturn entered the sun. Reason being we have a lot of copper and lithium that should not be there. Another large body slammed it into the Sun.

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[Tablizer]

Collisions can happen because objects share similar orbits. Thus, the collider(s) don't have to have odd orbits. Plus, the current orbits are probably shaped by tidal forces with neighboring planets and don't necessarily reflect original orbit.

I remember it like it was yesterday...

[jfdavis668]

The huge bulk of Theia growing larger in the sky...

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[Anonymous Coward]

I know you're lying because your user ID is too high.

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[wallsg]

Get off my lawn!

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[MightyYar]

I remember when most of the Slashdot stories revolved around fire and the wheel.

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[jfdavis668]

Imagine a Beowulf cluster of them!

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[turbidostato]

In Soviet Russia!

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[BoogieChile]

With hot grits poured down their pants!

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[Fire_Wraith]

But where does Natalie Portmann fit in?

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[BoogieChile]

In the garden, filling a valuable niche as an ornamental statue

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[ClickOnThis]

In Soviet Russia, Beowulf cluster of Natalie Portman overlord garden ornaments with hot grits poured down their pants welcomes you!

[Soviet Russia is sounding good right about now...]

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[ColdWetDog]

Bigger than a Brontosaurus, no feathers. Lame.

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[ClickOnThis]

I remember when most of the Slashdot stories revolved around fire and the wheel.

Eh? Speak up, sonny..

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[wonkey_monkey]

I remember when all this was orange groves...

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[Bob the Super Hamste]

I remember when Slashdot would stay up while slashdotting other sites.

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[jfdavis668]

This from an Anonymous Coward.

planet/planetoid

[alzoron]

Wouldn't Earth and Theia have been both planetoids at that point? One of the new requirements for being a planet is clearing your orbital path. It's pretty clear neither body had done that yet before that point, given the fact they smashed into each other.

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[Mashiki]

Unless of course something smashed into it at one point. Where it then traveled back into a semi-stable orbit and got smashed into a million itty-bitty-pieces. Which would explain the debris field between mars and Jupiter.

Re:planet/planetoid

[RubberDogBone]

You can call planets planets or call them aardvarks. It makes no difference. The name we give it has no meaning except to the person giving the name. Another person might call it something else. Who can say which is right? You because you give it a name in English, or a first nation's person who named it in their language? Which is correct? And which is wrong?

But no matter.

The planet itself does not care what we call it. Our names mean nothing to it. The planet simply is what it is, as it was before humans gave it names and as it will be long after humans have faded from this universe.

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[Coisiche]

Wasn't it the Greeks that called them planets? Or near enough as makes no difference.

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[Triklyn]

classification does matter to a certain extent, i mean, they've refined the definitions of those words. so, true, the planet/oids don't care what we call them, and calling them something different won't change a thing about them, but it's useful when talking about them to group them according to shared characteristics.

satellites, moons, planets, planetoids, asteroids, stars, black holes... humans. it's kinda the point of language.

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[toddestan]

The problem is that their definition of a planet is terrible. For example, there is only eight planets in the entire Universe because, by their definition, a planet can only orbit "the Sun". Yes, with that capitalization, thus referring to our Sun. I would have hoped they would have come up with something a bit more generic that could be applied to other solar systems.

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[Triklyn]

exoplanet? also, it's not immutable,

hard to classify something that we barely see as a planet... it's just not useful.

i'm like, super confident it'll change if and when we develop the capability of seeing if planet-sized satellites of extrasolar stellar objects.

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[rossdee]

Back in those days the IAU wasn't around to set the rules about what is or is not a planet.

Although it would be nice to send them back in time so they could witness the event.

LittleSister collisions

[Mal-2]

Collisions with someone's little sister -- a series of carefully controlled and mutually pleasurable collisions -- often produce new bodies. Why should planet-fuckers be any different?

Ghia's little sister

[JWSmythe]

So Gaia banged her little sister and made the moon? I assume rule 34 has already been satisfied for this, right?

Re:So how rare is this occurance?

[kenwd0elq]

Our substantial magnetic field may be due to the merging of the iron cores of the Proto-Earth and Theia. Earth is the most dense planet in the solar system, and from what we know of Mars and Venus, we suspect that our iron core is far larger than the other terrestrial planets.

Venus has a super-thick poisonous atmosphere; it's at least possible that our large Moon has, over a period of 4+ billion years, "skimmed away" enough of our atmosphere to have protected the Earth from a similar fate.

Of course, we only think that our atmosphere is right because we evolved here, in this atmosphere; if the atmosphere had been different, we would have evolved differently, and (had intelligent life developed at all) we'd think that THAT was the right sort of atmosphere.

Earth's atmosphere was different

[perpenso]

Of course, we only think that our atmosphere is right because we evolved here, in this atmosphere; if the atmosphere had been different, we would have evolved differently, and (had intelligent life developed at all) we'd think that THAT was the right sort of atmosphere.

IIRC earth's atmosphere was different. Our current atmosphere the result of life polluting that environment with oxygen. Causing an environmental catastrophe at the time.

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[account_deleted]

Comment removed based on user account deletion

Re:Earth's atmosphere was different

[TapeCutter]

Causing an environmental catastrophe at the time.

Yep, oxygen build up was a disaster for the cyanobacteria that created it and had reigned Earth for 3+ billion years. On the plus side the free oxygen enabled collagen to form, which is the substance that holds single cells together in multi-cellular organisms. We call that transition "The Cambrian explosion". The collision we are talking about occurred 3.5 billions years before the Cambrian explosion.

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[Triklyn]

well, oxygen does kinda wreck everything.

it kinda just like... super-wants all the electrons... all of them, in everything, everywhere.

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[AK Marc]

Venus and Mars both have no usable atmosphere because of the lack of a strong magnetic field. Venus has a dense (and poisonous) atmosphere because all the lighter gasses are forced to the top, and whisked away by the solar wind, leaving only the heaviest behind. If the planet had a magnetic field, the wind effect stripping away the atmosphere wouldn't have been as strong, and an equilibrium could have been achieved. Mars has the same effect, but not as much concentration of "heavy" because the lighter gr

Why different?

[kenwd0elq]

Why should the material composition of Theia have differed all that much from the Proto-Earth? They formed from the same planetary nebula, and at relatively similar distances from the Sun; shouldn't they have been similar in composition? And how can anyone state with any certitude, 4+ billion years later, how much of the merged Earth's crust was from Theia, and how much from the proto-Earth, and whether the lunar material was one, the other, or mostly mixed? It was a long time ago, and the Early Heavy Bombardment period would have stirred things up further. In fact, it's not unlikely that the Early Heavy Bombardment material was long-period debris from the original collision.

If Theia had formed substantially closer, or substantially farther away from the Sun, then the debris from the collision could hardly have remained close enough that the shards would coalesce to form the Moon. The differing orbital velocities would have seen to that.

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[Trax3001BBS]

If Theia had formed substantially closer, or substantially farther away from the Sun, then the debris from the collision could hardly have remained close enough that the shards would coalesce to form the Moon. The differing orbital velocities would have seen to that.

Theia was in the same orbit as Earth just a bit faster, it didn't collide as much as hit off center. Theia is made up of it's self and Earth's crust and why the Moon has no iron core. The series "How the Universe works" has a great animation of it.

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[Trax3001BBS]

Theia was in the same orbit as Earth just a bit faster, it didn't collide as much as hit off center. Theia is made up of it's self and Earth's crust and why the Moon has no iron core. The series "How the Universe works" has a great animation of it.

Video https://www.youtube.com/watch?... [youtube.com]

moon

[JohnVanVliet]

not really new news

this was a hypothesis pre Apollo
and confirmed from the sample returns
then reconfirmed using computer models of a highly tangential impact

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[TapeCutter]

There was also the theory that explained the Moon's density by proposing it was like honeycomb inside, only a handful of people thought either of those theories made any sense.

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[ledow]

The same could apply to evolution, to most of cosmology, to archaeology, to Egyptology, how the pyramids were made, to how cells formed, to just about every aspect of science.

It's just sheer ignorance to suggest that it's not worth pursuing.

Science is about looking what's ALREADY out there. Formulating a theory that ties some parts of it together and maybe how it originated.
Then testing your theory on other, sometimes unrelated parts of the universe. If they work, great, we have a certain amount of knowle

little sister, don't do what your big sister done

[mix_left_and_right]

little sister, don't you.... little sister, don't you.... little sister, don't you me kiss once or twice and then you run.... little sister, don't you do what your big sister done...

Junk science

[freak0fnature]

So the theory is that there were 2...they collided...and are still 2. They are made of similar stuff too, before and after. I'm sorry, how do we know they impacted again? Oh right...they are slightly different ages...we've mastered that whole dating thing back to 14 billion years. Wait, that doesn't mean they collided...hmmm I'm stumped.

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[account_deleted]

Comment removed based on user account deletion

Band name?

[gstoddart]

OK, am I the only one to read that summary and thin "shattered impactor" would be an awesome name for a band?