Did moon come from earth?

Anonymous · Oct 15, 2007

My question is: Where did moon come from? Did it come from earth, or is it an alien particle? In space, the things attach to one another i.e. come closer and form a mass altogether. Can this happen in case of earth and moon also? If, moon originated from earth, then from where and is it due to rotation at high speed, the famous belief? <div class="Discussion_UserSignature"> <img id="a9529085-d63d-481e-9277-832ea5d58917" src="http://sitelife.space.com/ver1.0/Content/images/store/9/2/a9529085-d63d-481e-9277-832ea5d58917.Large.gif" alt="blog post photo" /> Oops! this is my alien friend.╬→Ť╠╣є ’ M€ ’ ╬→ Ðôŵņ2Ëãřŧĥ ๑ ╬→ ЙДm€ :Varsha </div>

pyoko · Oct 15, 2007

Short answer: yes. Same piece as Earth. In fact, prbably from Earth. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

alokmohan · Oct 15, 2007

Origin of moon is interesting subject,there are many theories.What you state is only one of the viewa,

MeteorWayne · Oct 15, 2007

The most likely current theory is that early in the earth's history, it was whacked by a Mars sized object when there were such leftovers floating around the solar system. Some of the material from that collision became a ring around the earth which condensed to form the moon. This explains both the similaraties and the differences in the material that the earth and moon are made of, as well as the angular momentum (spin) of the earth/moon system Wayne <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Saiph · Oct 15, 2007

to go into a bit more detail about the collision theory: The moon's composition is very similar to the earths crust, and has a very low iron content. If the moon formed from the same proto-planetary cloud as the earth we would expect it to have a much more similar composition (i.e. a similar iron content to the earth's). Due to how similar the composition is, it's unlikely to be a captured moon, especially when you throw in the size, and low eccentricity of it's orbit. The main theory for it's formation then rests upon a monumental collision, shortly after the earth formed, and had time for it's components to differentiate (a lot of it's iron sinking to the core). If a large impactor came by and grazed earth, a massive amount of debris would be sent into space, a lot of it escaping entirely. Some would remain in orbit, the rest return to earth. Of what remained in orbit, it would eventually congeal into it's own massive object, in this case the moon. Due to orbital frictionial forces the orbit would be of a lowish eccentricity. Since the blow in this case is theorized to be a grazing blow, most of the material would be crustal in origins, with very little of the core iron content involved (essentially only the iron in left in the upper mantle and locked in the crust would remain). Thus we can, with this theory, explain the high similarity with earth's crust, but low iron and heavy metal content of the moon. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

willpittenger · Oct 15, 2007

It should be noted that the impactor's core would have been two massive to remain with the orbital debris or even on the Earth's crust. Instead, it would have sank to merge with the Earth's core. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

adrenalynn · Oct 15, 2007

Errr - let me do my homework and ask a less stupid question later. For anyone reading my previous post, I'm wishing to retract it. I was making the newb size to mass mistake. If I do some simple numbers, I get a mass of 1:81, earth to moon, assuming that the numbers from a quick online search are correct. (5.9742 * (10^24))kg / (7.36 * (10^22))kg = 81.1711957 So 1/81th the total mass of the earth was ejected, give or take whatever other junk was already floating around, and that is small enough to leave me not asking stupid questions. "Sorry and/or My bad". (attrib: Mr. Slowskie) <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

3488 · Oct 15, 2007

I am not sure at all of the Impact hypothesis. I think the moon, formed at on of the lagrange points in Earth's orbit, & over time the Moon drifted towards Earth & was captured. The impact theory, remember is just that, a theory. The lack of iron bearing materials (siderophiles) worries me about that theory, as does the Moon's overall fairly high density & very large size. I think either the impacting body was in a retrograde orbit around the Sun, so the explanation of a planet like Mars forming in a retrograde orbit will need explainingm if that is so, surely the Earth would have ended up with several, smaller moons, not just one massive planetary sized one. Thats my take on it. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

Saiph · Oct 15, 2007

The moon's density isn't that high, at ~3 g/cm, a whole 2 g/cm less than earths average density. As for the moon forming at a lagrange point, the only lagrange points it could have formed at are the "trojan" points, and I don't find it likely for such an object to attain the moon's size, and then leave the lagrange point, especially since they're quite stable. Also, no objects in a planetary trojan point approaches the size ratio of the earth moon system. As for the impactor requiring a retrograde orbit...I dont' see why. Any intersecting orbital parameter would easily provide enough energy for debris dispersal required. A fully retrograde orbit would probably provide far to much energy. As for the lack of iron bearing materials that the impact theory produces....that's actually one reason why it's favored, as a co-formation model produces a moon with similar iron levels as the earth, not a deficiency, and a capture model is hard pressed to explain what compositional similarities do exist. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

adrenalynn · Oct 16, 2007

I'm going to go ahead and ask this one, but I still feel I'm overlooking something obvious. I promise to be adequately embarassed. Now, we're talking about crust, so I assume the earth was cooled and such. Now if there was a collision with something say 10% the size of the earth, and it ejected ~1/80th the mass of the earth - shouldn't there be some pretty major physical evidence left behind? I mean, that's a pretty fair sized chunk of crust material to just vanish into thin "ether" - isn't it? <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

willpittenger · Oct 16, 2007

You are missing one key element of the theory: The crust would have completely melted during the impact. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

adrenalynn · Oct 16, 2007

Ok - I'll buy that, but only if the entire planet's crust melted. Or something close to it. Because covering that up otherwise would be significant. Further, melting and the reforming the crust has got to leave geophysical evidence, no? <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

willpittenger · Oct 16, 2007

<blockquote>In reply to:<hr />Further, melting and the reforming the crust has got to leave geophysical evidence, no?<hr /></blockquote> I have no information on that. However, I would have to question that. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

alokmohan · Oct 16, 2007

Suppose thhe moon splashed out from pacific ocean?

adrenalynn · Oct 16, 2007

Well, just from a logic standpoint, if you melt and cool a sedimentary deposit, any decent geologist/geophysics wonk is going to throw up one real big red flag. Especially in the volume we're talking about. Just to keep running my fingers off and thinking aloud, there almost wouldn't be sedimentary deposits predating the event. By definition it would have to be metamorphic, right? So if you look at the age of the moon, and then look for sedimentary formations older than that on earth, you pretty well have your answer - at least to the potential negative. Sometimes not eliminating a theory tells you a lot. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

adrenalynn · Oct 16, 2007

>> Suppose thhe moon splashed out from pacific ocean? Given the age of the moon, it wouldn't be "the pacific", right? It'd be THE ocean, from a PANGEA perspective. Besides, we do have a fair bit of sea-floor sampling. <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

alokmohan · Oct 16, 2007

The moon did not come that way.Correct.

adrenalynn · Oct 16, 2007

Woah there. I'm not ready to say THAT. That's a little too... statement-of-fact for my taste. I'm just saying that I'm having some problems with wrapping my head around a few tenets of this theory. I'm not even trying to be argumentative. I'm sure I'm missing something. (As I just mentioned to a geologist-friend on the phone a second ago. She's working on countering my position as I write this.) Here - let's just run down my basic line of reasoning: In order to crust and become spherical, the crust would have had to liquefy over a sizable region. But nothing else. We couldn't have run around knocking off much of the core (due iron content of the moon). If the planet were still cooling, the moon would have a high iron content under this theory since there wouldn't have been time for differentiation to "set in". So we have a cooled sphere, we graze it and knock a percent or two of the entire planet's mass off and we don't have a sphere unless it liquefies and gravity/centrifugal force spreads it out. Ok, so we do that, and we find that unless the entire surface liquefied, we have a very huge differential in the thickness of the crust of the impact region. Ok - so the whole thing liquefied. Now we need to look at sedimentary strata vs classic volcanic metamorphic strata vs fast-heated metamorphic strata. There's *got* to be a geologic record of that event. You can't run around knocking a point or two of the entire mass of a planet off, near instantaneously, and not leave any trace of the event. Ok - so that's effectively where I am. <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

MeteorWayne · Oct 16, 2007

Indeed, that is probably the last "full melting" reset of the geological record. Continental cratons that still exist formed after this event. IIRC, the whack occurred less than 100 ky after the earth finished accreting. I'm stil looking for the article <img src="/images/icons/frown.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Saiph · Oct 16, 2007

not a bad question at all. But there's a few things to consider, the impact occured over 4.5 billion years ago, and the earth's crust gets recycled. Some of the oldest rock on the ocean floor is only 2 billion years old.... another intersting point, but certainly not definitive, is the difference between Venus, nearly our size, and Earth. Venus has little tectonic activity, it's basically one or two giant plates, with a thick crust. Earth has a much thinner crust, and a lot more activity. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

adrenalynn · Oct 16, 2007

But if the earth were still cooling, then it was pre-differentiation. Which would have provided a large iron content in the crust, right? I'm not the geologist, so I'd need to look up the period for differentiation <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

MeteorWayne · Oct 16, 2007

I believe the differentiation would have been mostly complete by that time. But I am not an expert in this area. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

adrenalynn · Oct 16, 2007

Ok. But the crust in the ocean is naturally thin as it's the effective re-birthplace of the earth. The Vishnu Schist in the bottom of the grand canyon is around 2B years old, if my memories serve. Early life was starting to form as the theories had it back when I was studying this stuff as a kid. Primitive algaes and such. (Marble lensing) The Acasta Gneisses, again via memory, are some of the oldest rocks (at least I was taught so eons ago) at about 4.07B yrs. These are igneous and sedimentary rocks(!) So this theory as it's being presented leaves less than 500M yrs for an effective total re-creation AND then form life a couple billion years following. 500M yrs seems a bit short in geologic time, doesn't it? The advantage I could see to this impactor is that it might have deposited life here. ;-) Thanks again for the most stimulating discussion! <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

MeteorWayne · Oct 16, 2007

I believe recent indications of continental crust as old as 4.2 BY have been made. I will check after the STS 120 News conference. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

adrenalynn · Oct 16, 2007

So that leaves us even less time. 300M yrs. I also find this: "mineral grains (zircon) with U-Pb ages of 4.4 Ga have recently been reported from sedimentary rocks in west-central Australia" (Source: http://pubs.usgs.gov/gip/geotime/age.html) [...] "These calculations result in an age for the Earth and meteorites, and hence the Solar System, of 4.54 billion years with an uncertainty of less than 1 percent." [Ibid] So now we have 140M years to reaccreate and differentiate? That's like a geologic sneeze... <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

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