Searching for Theia, the mother of the Moon

The current preferred theory about how the Moon was formed is that early
on in the solar system, an object the size of Mars, located nearly at
the same distance from Sun as the Earth is now, impacted the Earth. It
is believed that it was located at one of the Lagrangian points, L4 or
L5 of the Earth, and then eventually spun in and hit it. The ejected
material then became the Moon.

There are currently two spacecraft being sent to both of these
locations, called STEREO. Their main mission is to observe the Sun from
both sides, and provide stereoscopic pictures of stuff coming off the
Sun (flares, CME's, etc.) heading towards Earth and other places. Since
they will be parked at the same L4 & L5 Lagrangian points where it's
believed Theia came from, they may also provide clues as to whether
Theia actually existed.

NASA - STEREO Mission
http://www.nasa.gov/mission_pages/st...ain/index.html

More about the Theia hypothesis:

Tom’s Astronomy Blog » Blog Archive » Hunting for Theia
http://tomsastroblog.com/?p=3271

iTWire - The Theia hypothesis goes STEREO
http://www.itwire.com/content/view/24366/1066/

NASA - STEREO Hunts for Remains of an Ancient Planet near Earth
http://science.nasa.gov/headlines/y2...htm?list970856

Yousuf Khan

Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is
believed that it was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the Moon.

Unlikely that it would have been in a stable orbit and somehow
lost angular momentum. Note that three are no L4 or L5 points
without a pre-existing Moon.

David A. Smith

"N:dlzc D:aol T:com (dlzc)" wrote in message
...
Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is believed that it
was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the Moon.

Unlikely that it would have been in a stable orbit and somehow lost
angular momentum. Note that three are no L4 or L5 points without a
pre-existing Moon.

David A. Smith

Trojans?
Look it up, Smiffy.
http://www.rssd.esa.int/SA-general/P...L/node118.html
http://www.dtm.ciw.edu/sheppard/trojans/

On Apr 11, 9:23*am, Yousuf Khan wrote:
The current preferred theory about how the Moon was formed is that early
on in the solar system, an object the size of Mars, located nearly at
the same distance from Sun as the Earth is now, impacted the Earth. It
is believed that it was located at one of the Lagrangian points, L4 or
L5 of the Earth, and then eventually spun in and hit it. The ejected
material then became the Moon.

There are currently two spacecraft being sent to both of these
locations, called STEREO. Their main mission is to observe the Sun from
both sides, and provide stereoscopic pictures of stuff coming off the
Sun (flares, CME's, etc.) heading towards Earth and other places. Since
they will be parked at the same L4 & L5 Lagrangian points where it's
believed Theia came from, they may also provide clues as to whether
Theia actually existed.

NASA - STEREO Missionhttp://www.nasa.gov/mission_pages/stereo/main/index.html

More about the Theia hypothesis:

Tom’s Astronomy Blog » Blog Archive » Hunting for Theiahttp://tomsastroblog.com/?p=3271

iTWire - The Theia hypothesis goes STEREOhttp://www.itwire.com/content/view/24366/1066/

NASA - STEREO Hunts for Remains of an Ancient Planet near Earthhttp://science.nasa.gov/headlines/y2009/09apr_theia.htm?list970856

* * * * Yousuf Khan

The current preferred theory as to our moon sucks, and any attempt to
simulate alternatives has been intentionally and systematically
foiled.

Our USAF could have mapped our physically dark Selene/moon at one
meter or better resolution as of nearly 4 decades ago.

~ BG

N:dlzc D:aol T:com (dlzc) wrote:
Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is
believed that it was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the Moon.

Unlikely that it would have been in a stable orbit and somehow
lost angular momentum. Note that three are no L4 or L5 points
without a pre-existing Moon.

I have my own doubts about this theory, but according to the article the
theorists think that the object grew in the L4 or L5, and then a
gravitational tug from a growing Venus destabilized it and slung it
towards Earth. And also note they're talking about the Earth-Sun
Langrangian points, not the Earth-Moon Lagrangians, so why wouldn't
there be an L4 or L5 without a moon?

Now, my problem with the Theia hypothesis is what we were talking about
from a previous thread:

http://groups.google.com/group/sci.a...91fd57fdf174f0

That thread was about missing asteroid mass in the Asteroid Belt. It
seemed to imply that most of the asteroids were thrown around by about
100 million years after the Solar System formed. And in fact, the
majority of the Moon's craters were formed at that time. However, 100
million years is not a lot of time by geological standards. Is there
enough time for an Earth-Theia impact, followed by a coalescing of the
Moon, followed by a solidification of the Moon, followed by a major
asteroid bombardment on the Moon that have would still leave scars on
its surface? It would seem to me that the Moon would still be mostly
molten by the time the asteroid bombardment happened, thus most of its
scars would've been healed over by now.

Yousuf Khan

"Yousuf Khan" wrote in message
...
N:dlzc D:aol T:com (dlzc) wrote:
Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is believed that it
was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the Moon.

Unlikely that it would have been in a stable orbit and somehow lost
angular momentum. Note that three are no L4 or L5 points without a
pre-existing Moon.

I have my own doubts about this theory, but according to the article the
theorists think that the object grew in the L4 or L5, and then a
gravitational tug from a growing Venus destabilized it and slung it
towards Earth. And also note they're talking about the Earth-Sun
Langrangian points, not the Earth-Moon Lagrangians, so why wouldn't there
be an L4 or L5 without a moon?

Now, my problem with the Theia hypothesis is what we were talking about
from a previous thread:

http://groups.google.com/group/sci.a...91fd57fdf174f0

That thread was about missing asteroid mass in the Asteroid Belt. It
seemed to imply that most of the asteroids were thrown around by about 100
million years after the Solar System formed. And in fact, the majority of
the Moon's craters were formed at that time. However, 100 million years is
not a lot of time by geological standards. Is there enough time for an
Earth-Theia impact, followed by a coalescing of the Moon, followed by a
solidification of the Moon, followed by a major asteroid bombardment on
the Moon that have would still leave scars on its surface? It would seem
to me that the Moon would still be mostly molten by the time the asteroid
bombardment happened, thus most of its scars would've been healed over by
now.

Yousuf Khan

You seem to have the time scale incorrect.
The Theia hypothesis is much as you describe it, except the asteroid
struck the Earth 4000 million years ago, not 100 million years ago.
Upon striking the Earth enough material was ejected to form a
Saturn-like ring around the Earth which then merged to form the
Moon.
I'm not saying its correct or not, but the Moon definitely got here
somehow. My own view is that it is much more likely to have been
captured than part of some cataclysmic collision, perhaps like this
(example 10, but stable):
http://faculty.ifmo.ru/butikov/Proje...llection1.html

On Apr 11, 8:31*pm, "Androcles" wrote:
"Yousuf Khan" wrote in message
Now, my problem with the Theia hypothesis is what we were talking about
from a previous thread:

http://groups.google.com/group/sci.a...m/thread/184e4...

That thread was about missing asteroid mass in the Asteroid Belt. It
seemed to imply that most of the asteroids were thrown around by about 100
million years after the Solar System formed. And in fact, the majority of
the Moon's craters were formed at that time. However, 100 million years is
not a lot of time by geological standards. Is there enough time for an
Earth-Theia impact, followed by a coalescing of the Moon, followed by a
solidification of the Moon, followed by a major asteroid bombardment on
the Moon that have would still leave scars on its surface? It would seem
to me that the Moon would still be mostly molten by the time the asteroid
bombardment happened, thus most of its scars would've been healed over by
now.

Yousuf Khan

You seem to have the time scale incorrect.
The Theia hypothesis is much as you describe it, except the asteroid
struck the Earth 4000 million years ago, not 100 million years ago.

No, no, that's not what I said. I said 100 million years *after* the
formation of the Solar System.

In other words, if the Solar System formed 4.5 billion years ago, then
the asteroid strikes were supposedly 4.4 billion years ago.

Upon striking the Earth enough material was ejected to form a
Saturn-like ring around the Earth which then merged to form the
Moon.
I'm not saying its correct or not, but the Moon definitely got here
somehow. My own view is that it is much more likely to have been
captured than part of some cataclysmic collision, perhaps like this
(example 10, but stable):
*http://faculty.ifmo.ru/butikov/Proje...llection1.html

This would require the Earth to have had a smaller satellite already
in orbit around it, wouldn't it? That smaller satellite gets booted
out, and the Moon moves in.

Yousuf Khan

Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
N:dlzc D:aol T:com (dlzc) wrote:
"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is
believed that it was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the
Moon.

Unlikely that it would have been in a stable orbit and
somehow lost angular momentum. Note that three
are no L4 or L5 points without a pre-existing Moon.

I have my own doubts about this theory, but according
to the article the theorists think that the object grew in
the L4 or L5,

There *were* no L4 or L5 points without a Moon. (I see below
they meant solar L4 / L5)

and then a gravitational tug from a growing Venus
destabilized it and slung it towards Earth.

Total bull. Would take an en passant maneuver to strip the
angular momentum.

And also note they're talking about the Earth-Sun Langrangian
points, not the Earth-Moon Lagrangians,
so why wouldn't there be an L4 or L5 without a moon?

Sorry. Still takes an en passant...

Now, my problem with the Theia hypothesis is what
we were talking about from a previous thread:

http://groups.google.com/group/sci.a...91fd57fdf174f0

That thread was about missing asteroid mass in the
Asteroid Belt. It seemed to imply that most of the
asteroids were thrown around by about 100 million
years after the Solar System formed. And in fact,
the majority of the Moon's craters were formed at
that time. However, 100 million years is not a lot of
time by geological standards. Is there enough time
for an Earth-Theia impact, followed by a coalescing
of the Moon,

This will take some time. All / most-of the light stuff had to
sort out after the "mixing event", as that is what the Moon got.

followed by a solidification of the Moon,

No atmosphere, possibly no shielding by Earth (assuming it was
"lobed off") but meters of crust won't hold a crater impression.
Are there *any* mares on the far side?

followed by a major asteroid bombardment on the
Moon that have would still leave scars on its surface?

I would expect the bombardment to be stretched out over a longer
time, as it would seem "100 milloin years" might be tight to get
to an impressionable state.

It would seem to me that the Moon would still be mostly molten
by the time the asteroid bombardment happened,

Agreed.

thus most of its scars would've been healed over by now.

.... like the mares...

David A. Smith

"YKhan" wrote in message
...
On Apr 11, 8:31 pm, "Androcles" wrote:
"Yousuf Khan" wrote in message
Now, my problem with the Theia hypothesis is what we were talking about
from a previous thread:

http://groups.google.com/group/sci.a...m/thread/184e4...

That thread was about missing asteroid mass in the Asteroid Belt. It
seemed to imply that most of the asteroids were thrown around by about
100
million years after the Solar System formed. And in fact, the majority
of
the Moon's craters were formed at that time. However, 100 million years
is
not a lot of time by geological standards. Is there enough time for an
Earth-Theia impact, followed by a coalescing of the Moon, followed by a
solidification of the Moon, followed by a major asteroid bombardment on
the Moon that have would still leave scars on its surface? It would seem
to me that the Moon would still be mostly molten by the time the
asteroid
bombardment happened, thus most of its scars would've been healed over
by
now.

Yousuf Khan

You seem to have the time scale incorrect.
The Theia hypothesis is much as you describe it, except the asteroid
struck the Earth 4000 million years ago, not 100 million years ago.

No, no, that's not what I said. I said 100 million years *after* the
formation of the Solar System.

In other words, if the Solar System formed 4.5 billion years ago, then
the asteroid strikes were supposedly 4.4 billion years ago.

===============================================
Oh, ok. My mistake, I should have read carefully.


Upon striking the Earth enough material was ejected to form a
Saturn-like ring around the Earth which then merged to form the
Moon.
I'm not saying its correct or not, but the Moon definitely got here
somehow. My own view is that it is much more likely to have been
captured than part of some cataclysmic collision, perhaps like this
(example 10, but stable):
http://faculty.ifmo.ru/butikov/Proje...llection1.html

This would require the Earth to have had a smaller satellite already
in orbit around it, wouldn't it? That smaller satellite gets booted
out, and the Moon moves in.

Yousuf Khan

Err... no. The three bodies involved are the Sun, Earth and Luna, although
Butikov modelled them as Earth, Luna and a small asteroid of insignificant
mass which eventually collides.
In reality we would have to include Mercury, Venus, Mars and Jupiter,
making the already chaotic 3-body model hideously complicated.
There is no general solution to the 3-body problem, so modelling the
Solar System without knowing the exact initial conditions is an impossible
task.
The point to notice in Butikov's model is the complete orbit of the
satellite around the primary seen at the start, not just the secondary
capture process. One would ask how it is possible for the orbit to
degenerate so quickly, but naturally Butikov has chosen parameters
to make it so. We are not going to sit staring at the screen for 10
orbits, let alone a million. Yet it would be quite reasonable if it took
a million years or ten million or a hundred million for the capture to
occur.

The reason I would choose capture is really quite simple, the other (outer)
planets also have moons and even Mars has two small satellites. Are we
to say Mars was hit by an asteroid, Jupiter was hit by an asteroid, Saturn
was hit by an asteroid?

That doesn't mean I'm right, I'm merely saying capture has a higher
probability than the Theia impact theory, although less exotic. I take the
view that there is far too much wild theorising about things we can never
know, let alone prove, and not enough searching for simpler solutions.

I'll leave it for the children to get excited over planetary collisions,
Santa
Claus and the Easter Bunny, I'll remain the wet blanket putting the fire
out.
That the Earth-Moon system even exists and the Earth has a hot interior
is exciting enough for me, for therein lies the evolution of life.

In sci.astro message , Sat, 11 Apr
2009 10:22:21, "N:dlzc D:aol T:com (dlzc)" posted:
Dear Yousuf Khan:

"Yousuf Khan" wrote in message
...
The current preferred theory about how the Moon was
formed is that early on in the solar system, an object
the size of Mars, located nearly at the same distance
from Sun as the Earth is now, impacted the Earth. It is
believed that it was located at one of the Lagrangian
points, L4 or L5 of the Earth, and then eventually spun
in and hit it. The ejected material then became the Moon.

Unlikely that it would have been in a stable orbit and somehow
lost angular momentum. Note that three are no L4 or L5 points
without a pre-existing Moon.

Your sagacity is imperceptible.

Granted, the Lagrange points of the Earth-Moon system would not exist
without the Moon.

But the Sun-Earth system also has Lagrange points, independently of the
existence of the Moon, and it is at one of those (L4/L5) that Theia has
been supposed to have existed. The citation of those distances above
strongly suggests that.

So does "of the Earth"; a body can in its capacity of a secondary have
only one set of five Lagrange points, but a body acting as a primary can
have multiple sets of five Lagrange points.

The Sun-Jupiter system has Lagrange points, of course; two of them are
homes to asteroids named after heroes of the Trojan wars.

Any gravitationally-bound two-body system has five Lagrange points; if
the mass ratio is less than about 25:1, or if there are other
sufficiently massive bodies near by, no points are dynamically stable,
except in special cases - in which case they would not be the points for
which Lagrange is known.

More details via below, with Gravity Tractor material.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.