Originally posted by kenshiro2012
I prefer the "capture theory myself.
The 4th scenerio, has a couple of drawback to it for me to accept it.
If you go by it, then you would (probably) have more than one moon.
Also the ejection of material to the Roche limit would require one heck of a collision.
The lack of a large amount of iron in the moon's core I have to question how they were able to determine this. As the normal method of determining the composition of extra-terrestrial bodies is through the use of spectral analysis.
This method would indicate iron deposits on - near the surface.
The moon being as cold as it is, the core could very well be solid. Without there being an expedition to drill down to the core to verify it's composition, how can they be sure?

They can measure the "weight" of the Moon, and determine its density from that and it just doesn't leave room for much Iron.

Basically, the Moon is "underweight" for a body of its size, which means it doubtfully accreted as a normal planet would have. Because of its lesser elemental composition the only plausible explanation left is that it was formed from Crustal and Mantle material from the Earth only some time after the Earth had differentiated (most of the heavy material such as Iron sank to the Core).

The other three reasons are the least likely from current studies, and are archaic, left over from the 1800s.

Originally posted by Raven_on_a_pedestal
Well i haven't followed this particularily because i have just joined but, how could we test the splash method when most of the crust then is now liquid mantle? most of the current soil and rock is more recent than... well however long ago it supposedly happened. its just decayed plants animals and other living beings and the rock is from plate tectonics and volcanoes more recent than 3 billion years. i don't sound proffesional because im only 14 and doing a project about the moon and its phases. and since we havent tested the moons core we couldnt tell whether it was the splash method or not.

[edit on 28-1-2006 by Raven_on_a_pedestal]

I already explained the reason the impact theory is most plausible.

You are wrong about the age of rocks, cratons, continental interiors, stable platforms are names for areas where the rock often is older than 3 and as old as 4 billion years.

These are the oldest continents, before accretion created the larger continents we know today...

Thus we can get an idea of what composition was like of the Earth's crust back then...and mantle material.

P.S. Another reason that the Moon probably came from the Earth is that the Moon has been moving away from the Earth...hundreds of millions of years ago it was so close that the lunar cycle was only a matter of about 20 days, instead of today's 27 or so...this is recorded in laminae caused by tides in now lithified sediments.

If an object were captured, it'd be in a highly irregular orbit (much like asteroids and other bodies in motion that were captured by the sun's gravity or other object's gravity).

Objects that are in very circular orbits were formed while in orbit of what they orbit...the Moon's moving further away at such a rapid speed suggests that it began very close, and has slowly progressed away.

[edit on 9-2-2006 by Stratrf_Rus]

I'm kind of confused... How is what possible?

I think he is confused by the calculation showing that at the rate of the moon moving from the earth it would have been touching the Earth 9 billion years ago, (older then the age of the universe). I think he is thinking of the old, and now discredited “Dumbbell” theory.

If we accept the deduction (based on calculations of lunar density indicating it cannot have a planetary core of Iron) that the moon came out of the Earth surface layers (crust and mantle) then what about this theory: after the cosmic event that ejected the moon from the earth, there was a truly gaping "hole" in the earth's sphere. To "compensate" and "try to even out" the surface shape, the earth started to split the bulge in the crust that up to then was "pangeia," or the original single land mass continent, and that was what started continental drifting. The Pacific Basin therefore would have been much larger prior to continental drifting, and if we were to figure out the original size of the massive hole or original Pacific Basin, we would have to include the basins of the other oceans, especially the Atlantic Ocean Basin, which is where the mid oceanic ridge now continues to widen the Atlantic Basin a few inches per year. I haven't seen this theory spoken about though it seems simple enough.

Originally posted by michaelanteski
If we accept the deduction (based on calculations of lunar density indicating it cannot have a planetary core of Iron) that the moon came out of the Earth surface layers (crust and mantle) then what about this theory: after the cosmic event that ejected the moon from the earth, there was a truly gaping "hole" in the earth's sphere. To "compensate" and "try to even out" the surface shape, the earth started to split the bulge in the crust that up to then was "pangeia," or the original single land mass continent, and that was what started continental drifting. The Pacific Basin therefore would have been much larger prior to continental drifting, and if we were to figure out the original size of the massive hole or original Pacific Basin, we would have to include the basins of the other oceans, especially the Atlantic Ocean Basin, which is where the mid oceanic ridge now continues to widen the Atlantic Basin a few inches per year. I haven't seen this theory spoken about though it seems simple enough.

this is the one for me, it just leaves the question what collided with earth. could the remnants of the asteroid belt have something to do with it despite it being the other side of mars.

also, as for the moon moving away from the earth at a rate of 4cm a year mean that theres a possibility of it slowing down and eventually start getting closer to earth? if it indeed was a portion of our crust and got to where it is now, would the moon have the power to keep going outwards and leave the gravity pull of the earth or would earths gravity slow it down and eventually bring it crashing back.