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Science Forum Index » Geology Forum » Theory of formation of the moon
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| Timberwoof |
 Posted: Sat Mar 22, 2008 2:25 am |
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In article
<12b1cb20-97f8-4285-a030-f95042fedf1b@m34g2000hsc.googlegroups.com>,
BradGuth <bradguth@gmail.com> wrote:
Quote: On Mar 18, 9:12 am, rAgAv <ragav.pa...@googlemail.com> wrote:
I watched a show on Natgeo which showed the formation of earth and the
solar system as they are now. It supported the following theory, a
few billion years after the formation of solar system,when the earth
was still in the molten state, a planet half the size of earth
collides with earth.As a result of this collision, some part of that
planet merges with the earth and becomes part of it and the remaining
fragments form a planetesimal called the moon.
My doubt is - if the same planet formed the moon and merged with the
earth, why isn't there a similarity between the rocks found in moon
and those that are found in earth?
Isn't the moon also somewhat older than Earth?
No, some rocks on the moon are older than the oldest Earth rocks. But
the "age" of a rock means when it was last melty.
--
Timberwoof <me at timberwoof dot com> http://www.timberwoof.com
"When you post sewage, don't blame others for
emptying chamber pots in your direction." ‹Chris L. |
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| BradGuth |
| Posted: Mon Mar 24, 2008 11:03 am |
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On Mar 21, 11:25 pm, Timberwoof
<timberwoof.s...@inferNOnoSPAMsoft.com> wrote:
Quote: In article
12b1cb20-97f8-4285-a030-f95042fed...@m34g2000hsc.googlegroups.com>,
BradGuth <bradg...@gmail.com> wrote:
On Mar 18, 9:12 am, rAgAv <ragav.pa...@googlemail.com> wrote:
I watched a show on Natgeo which showed the formation of earth and the
solar system as they are now. It supported the following theory, a
few billion years after the formation of solar system,when the earth
was still in the molten state, a planet half the size of earth
collides with earth.As a result of this collision, some part of that
planet merges with the earth and becomes part of it and the remaining
fragments form a planetesimal called the moon.
My doubt is - if the same planet formed the moon and merged with the
earth, why isn't there a similarity between the rocks found in moon
and those that are found in earth?
Isn't the moon also somewhat older than Earth?
No, some rocks on the moon are older than the oldest Earth rocks. But
the "age" of a rock means when it was last melty.
--
Timberwoof <me at timberwoof dot com>http://www.timberwoof.com
"When you post sewage, don't blame others for
emptying chamber pots in your direction." ‹Chris L.
But lo and behold, it seems we have no such rock samples as obtained
from the bedrock our moon, other than whatever previously fell towards
Earth as that icy proto-moon got summarily nailed by some sort of god-
offal horrific stuff. Possibly those Russian obtained moon rocks, or
rather mostly of a surface soil comprised of primary and secondary
impact debris as having little if anything to do with the moon itself,
can by way of your government trustworthy standards be somewhat
trusted, although oddly they’ve never once demonstrated such purely
robotic fly-by-rocket of any such complex lander and much less sample-
return expertise, or even any tidbit worth of their R&D, have they?
NASA couldn’t even win the Google X-Prize if they tried as of today,
much less of nearly half a century ago.
Perhaps to those supposedly smart USSR/Russians and of their Semitic
Third Reich wizards as having been extracted or rather plucked safely
away from their German Third Reich cozy box, whereas film as a method
of R&D documentation wasn’t invented as of way back then.
Those once-upon-a-time melty rocks of our moon, being that there
should be any number of raw mega-tonnage if not giga-tonnage worth of
such moon rocks to being found upon our terrestrial surface, or under
whatever ice and otherwise resting upon the mostly ocean bottom areas
of this Earth, as such and by all the common law rights of physics
should have their thorium and/or lead dating rechecked, whereas that
measured age of thorium, lead or perhaps even of sodium (as somewhat
recently identified as being of an off-world type of rock w/sodium)
shouldn’t have been age altered by whatever melty aspects.
. – Brad Guth |
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| BradGuth |
| Posted: Mon Mar 24, 2008 11:07 am |
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On Mar 21, 11:23 pm, Timberwoof
<timberwoof.s...@inferNOnoSPAMsoft.com> wrote:
Quote: In article
a6f64194-e0a5-4c23-808a-d8d14182a...@z38g2000hsc.googlegroups.com>,
BradGuth <bradg...@gmail.com> wrote:
On Mar 18, 8:39 pm, Timberwoof <timberwoof.s...@inferNOnoSPAMsoft.com
wrote:
In article
b8a425c1-e21b-4b64-b2fc-a155d0078...@e23g2000prf.googlegroups.com>,
rAgAv <ragav.pa...@googlemail.com> wrote:
I watched a show on Natgeo which showed the formation of earth and the
solar system as they are now. It supported the following theory, a
few billion years after the formation of solar system,when the earth
was still in the molten state, a planet half the size of earth
collides with earth.As a result of this collision, some part of that
planet merges with the earth and becomes part of it and the remaining
fragments form a planetesimal called the moon.
My doubt is - if the same planet formed the moon and merged with the
earth, why isn't there a similarity between the rocks found in moon
and those that are found in earth?
The hypothesis has the impact a few million or tens of million years
after the formation of the Earth. And most of the impactor sails away
into space.
And in fact, the moon and the Earth have similar compositions.
Here, check this out for a start to your research:
http://en.wikipedia.org/wiki/Moon#Origin_and_geologic_evolution
--
Timberwoof <me at timberwoof dot com>http://www.timberwoof.com
"When you post sewage, don't blame others for
emptying chamber pots in your direction." ?Chris L.
Lots of older than Earth moon rocks exist. Go figure, where do you
think the bulk of those moon crater displaced rocks ended up?
They're not that much older than the oldest Earth rocks, and given your
hypothesis that the moon came from elsewhere, that makes their ages
downright coincidental.
--
Timberwoof <me at timberwoof dot com>http://www.timberwoof.com
"When you post sewage, don't blame others for
emptying chamber pots in your direction." ‹Chris L.
I'll buy "downright coincidental", especially since the vast bulk of
this universe was supposedly cerated as of only one BB, along with
billions of interactions having since made lots of solid stuff melty
from time to time.
. - Brad Guth |
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| Aidan Karley |
| Posted: Sun Mar 30, 2008 11:12 am |
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In article <b8a425c1-e21b-4b64-b2fc-
a155d0078cbf@e23g2000prf.googlegroups.com>, RAgAv wrote:
Quote: It supported the following theory, a
few billion years after the formation of solar system,when the earth
was still in the molten state, a planet half the size of earth
collides with earth.
The most widely accepted model for the formation of the Earth-
Moon double planet is from the impact of a (approximately) Mars-sized
body with the proto-Earth when that was still accreting. There is
dispute if the proto-Earth had reached half it's present mass, or 2/3 .
After the impact and the very rapid (geologically - a few hundreds of
thousands of revolutions only) stabilisation of the double-planet
system, there may have been some more accretion onto the molten proto-
planets ; one would reasonably model this as happening in proportion to
the masses. "To those that have, shall be given." is how planetary
accretion (and Capitalism) works. This additional material input
probably ceased at the latest by the end of the "Late Heavy
Bombardment", which is dated to about 3700 Ma from Lunar materials.
Quote: As a result of this collision, some part of that
planet merges with the earth and becomes part of it and the remaining
fragments form a planetesimal called the moon.
The most widely accepted range of models of this event has both
impactor and target planetesimals differentiated into (at least) a
metallic core and a rocky "mantle" ; when these planetesimals impact
(inside computers, of course), then in most cases *both* cores end up
in the larger original body, while much of the "mantle" of the lighter
body (and some of the heavier body) ends up spraying around in near
-"heavier body" orbit and re-accreting in a matter of hours. Some of
the material sprayed off accretes into one (or more) satellites after
briefly forming a ring of debris (similar but not identical to Saturn's
rings).
Both bodies (impactor and target) are largely dismantled and re
-constructed in the impact and it's aftermath.
Quote: My doubt is - if the same planet formed the moon and merged with the
earth, why isn't there a similarity between the rocks found in moon
and those that are found in earth?
In many respects there are strong similarities between the rocks
of Earth and Moon. But they're not identical because Earth and moon
have had very different life histories since. The Moon has never had
significant volatile material (and hence no atmosphere or chemical
weathering) since the Giant Impact, while the Earth has ; on the Earth
those volatiles (delivered in the post-impact accretion) appear to have
played a vital role in lubricating the movement of the upper parts of
the planet. That leads to plate tectonics, re-processing of mantle
melts through multiple generations to yield granitic continents.
Meanwhile on the Moon, the main events seem to have been total fusion
(courtesy of impact-generated heat) leading to cumulate segregation of
olivine (towards the core) and the cumulate *floating* of a plagioclase
feldspar phase to produce what on Earth are rare rocks called
Trondjeimites, but very common on the Moon. These formed an early crust
onto which meteorites continued to fall (producing the rough landscape
of the "Lunar Highlands", where most of the Apollo landers went).
During the Late Heavy Bombardment (probably) a number of particularly
large impacts managed to fracture through the trondjeimitic crust to
liberate large amounts of (more-or-less) basaltic melt, which came up
to form the dark Mare which so-obviously mark the visible face of the
Moon.
These historical differences between the Earth and Moon lead to
different rocks on both, using "rocks" in the sense of "arrangements of
mineral grains". However, if you look at the atoms and nuclei that make
up those minerals, they are much more similar. In the early Solar
System there were non-trivial differences in the atomic and
particularly isotopic composition of material at different distances
from the Sun. We still see the same when meteorites from Mars, or the
members of the asteroid belt - are analysed : different sources have
different atomic and isotopic signatures. Looking at the composition of
different bodies in the Solar System, the Earth and Moon stand out very
clearly as a double planet compared to the others.
Hmmm, time for Sunday afternoon shopping soon.
--
Aidan Karley, FGS,
Aberdeen, Scotland |
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| Aidan Karley |
| Posted: Sun Mar 30, 2008 11:12 am |
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In article <db0a9ac6-bc66-483c-bb98-
87ea83566db9@s37g2000prg.googlegroups.com>, BradGuth wrote:
Quote: Then why can't other simulations be run? What are you afraid of?
[ Simulations of the "Giant Impact" which is the best-supported
model for forming the double-planets of Earth-Moon and Pluto-Charon.]
The last time I looked in any detail at this was around about
2000, when Robin Canup of SWRI (?Boulder, Colorado, USA) was publishing
the statistics of a number of hundreds of such simulations. In quite a
good proportion of the runs, several well-spaced smaller satellites
formed alongside the main one, rather like the 3rd and 4th satellites
of Pluto. A great piece of prediction.
Look up Canup's more recent publications and I'm certain that
you'll find a number of other compilations of simulations. I recall
seeing (in passing) her having published something on Arxiv in the last
few months, so you don't necessarily need to have a subscription to
relevant journals. You'll also get (from the references) the names of
some of her collaborators AND the people she disagrees with.
Do your homework.
--
Aidan Karley, FGS,
Aberdeen, Scotland |
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