Mars' Missing Angular Momentum

On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of captures or of
processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place both
of Mars' moons in near-circular orbits almost dead-on Mars' equatorial
plane.

I have already read "in the literature" that the fact that the Sun's
angular momentum is so much lower than the rest of the Solar system's
total angular momentum is considered a "flaw" in the presently held
condensation theory. So what you say here is evidently still at

That was a view held in the 1940s or 50s. What literature still says it is
a problem? Since then the reason for the Sun's slow rotation has been found
(and I already explained this). The Sun's equatorial rotational velocity is
currently 1.2 km/sec approximately. Typical rotational velocities for very
young solar type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular momentum as the
planets (mainly Jupiter) and gradually lost it as the result of a strong
stellar wind (which is stronger for rapid rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find that
you're correct.

Take for example, the computer model that yields the presently-held
"Giant Impact Hypothesis" for the origin of the Moon. How much does
this model have to be "tweaked" to be held plausible, let alone
probable? A "Mars-sized" object in the early Solar system, before
Earth became a "planet" and was still a "proto-planet", would have
most likely come from outside the Solar system from another stellar
system. What are the chances of an object that size from outside the

Why do you say it would have to come from outside? The inner solar system
was like a shooting gallery when the (proto)planets were young.

Yes, a shooting gallery of smaller chunks of material, not Mars-sized
objects, which would be planet-sized objects soaring around while
Earth was still in proto- stage? Doubtful.

Solar system hitting, colliding with, proto-Earth? What are the

Chances are next to nil. But there were lots of planetesimals within the
solar system at the very early stages.

Planetesimals. Not planets. Think about it. A Mars-sized object on
some weird kind of trajectory in a forming Solar system with lots of
small chunks of stuff soaring around. The bigger chunks that were
that close to the Sun were on stable orbits similar to what we see
today, weren't they? Where could such a large chunk have come from
within the Solar system? And even if it did come from within the
Solar system, again, what are the chances of such a collision so
perfect so as to place enough material beyond the Roche limit so that
when that material accreted into the Moon, it would orbit Earth in an
almost perfect circle and almost dead-on the ecliptic?

You might like that GIH, but I think it stinks to high-heaven.

chances that said impact would place enough material outside the Roche
limit of proto-Earth to accrete into the Moon? Computer models can
only take you so far. Sometimes it takes too many "tweaks" to get a
scientist what he (or she) wants.

The only real requirement was a "glancing" blow rather than a head on
collision. Given that, the chances are pretty good.

You didn't strike me as such a dreamer!

--
Happy Holidays!
and Warm Wishes for the New Year!
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
"There is a great warrior within all of us. What wakes yours up?"

Painius wrote:
On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of captures
or of processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place both
of Mars' moons in near-circular orbits almost dead-on Mars' equatorial
plane.

Tidal friction could cause this over a long time span.


I have already read "in the literature" that the fact that the Sun's
angular momentum is so much lower than the rest of the Solar
system's total angular momentum is considered a "flaw" in the
presently held condensation theory. So what you say here is
evidently still at

That was a view held in the 1940s or 50s. What literature still
says it is a problem? Since then the reason for the Sun's slow
rotation has been found (and I already explained this). The Sun's
equatorial rotational velocity is currently 1.2 km/sec
approximately. Typical rotational velocities for very young solar
type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular momentum
as the planets (mainly Jupiter) and gradually lost it as the result
of a strong stellar wind (which is stronger for rapid rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find that
you're correct.

Take for example, the computer model that yields the presently-held
"Giant Impact Hypothesis" for the origin of the Moon. How much does
this model have to be "tweaked" to be held plausible, let alone
probable? A "Mars-sized" object in the early Solar system, before
Earth became a "planet" and was still a "proto-planet", would have
most likely come from outside the Solar system from another stellar
system. What are the chances of an object that size from outside
the

Why do you say it would have to come from outside? The inner solar
system was like a shooting gallery when the (proto)planets were
young.

Yes, a shooting gallery of smaller chunks of material, not Mars-sized
objects, which would be planet-sized objects soaring around while
Earth was still in proto- stage? Doubtful.

The inner solar system around the time of the Moon's origin had only a few
larger objects left.

Solar system hitting, colliding with, proto-Earth? What are the

Chances are next to nil. But there were lots of planetesimals
within the solar system at the very early stages.

Planetesimals. Not planets. Think about it. A Mars-sized object on
some weird kind of trajectory in a forming Solar system with lots of
small chunks of stuff soaring around. The bigger chunks that were
that close to the Sun were on stable orbits similar to what we see
today, weren't they? Where could such a large chunk have come from
within the Solar system? And even if it did come from within the

Coalescence of those smaller chunks. Just like all the planets.

Solar system, again, what are the chances of such a collision so
perfect so as to place enough material beyond the Roche limit so that
when that material accreted into the Moon, it would orbit Earth in an
almost perfect circle and almost dead-on the ecliptic?

You might like that GIH, but I think it stinks to high-heaven.

You're welcome to your own opinion.


chances that said impact would place enough material outside the
Roche limit of proto-Earth to accrete into the Moon? Computer
models can only take you so far. Sometimes it takes too many
"tweaks" to get a scientist what he (or she) wants.

The only real requirement was a "glancing" blow rather than a head on
collision. Given that, the chances are pretty good.

You didn't strike me as such a dreamer!

Suit yourself, the evidence supports a collisional origin for the Moon and
explains its composition (similar to the Earth's mantle), while capture is
difficult dynamically because it requires three bodies in close proximity.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

On Mon, 19 Dec 2011 05:58:14 -0500, Painius
wrote:

On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of captures or of
processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place both
of Mars' moons in near-circular orbits almost dead-on Mars' equatorial
plane.

I have already read "in the literature" that the fact that the Sun's
angular momentum is so much lower than the rest of the Solar system's
total angular momentum is considered a "flaw" in the presently held
condensation theory. So what you say here is evidently still at

That was a view held in the 1940s or 50s. What literature still says it is
a problem? Since then the reason for the Sun's slow rotation has been found
(and I already explained this). The Sun's equatorial rotational velocity is
currently 1.2 km/sec approximately. Typical rotational velocities for very
young solar type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular momentum as the
planets (mainly Jupiter) and gradually lost it as the result of a strong
stellar wind (which is stronger for rapid rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find that
you're correct.

Well, it appears that your doubt is actually realized. There are
recent publications that still list the Solar system's "angular
momentum problem" as having yet to be solved. I did read where the
idea about the Solar wind as having whisked away much of the Sun's
angular momentum is strongly credible. I read where other stars
similar in age to our Sun were also spinning slowly. I was unable to
find anything definitive about younger stars and their faster spins,
though. Perhaps you could provide a link as a pointer? To be clear,
I was unable to find any published material about observations of
differently aged stars and their associated spin rates.

One aspect that I read has to do with the Solar wind idea. This may
explain how the Sun lost a good deal of its angular momentum; however,
it fails to explain the second part of the angular momentum problem,
which is the extremely high angular momentum, compared with the Sun's
angular momentum, of all the bodies in the Solar system that orbit the
Sun. If the condensation theory is correct, then how did all the
material in the accretion disk take on so much angular momentum? I
don't see how the Solar wind in and of itself could have imparted to
all the orbiting bodies such a relatively high level of angular
momentum. Do you?

--
Happy Holidays!
and Warm Wishes for the New Year!
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
"There is a great warrior within all of us. What wakes yours up?"

On Mon, 19 Dec 2011 13:02:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of captures
or of processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place both
of Mars' moons in near-circular orbits almost dead-on Mars' equatorial
plane.

Tidal friction could cause this over a long time span.

Tidal friction from Phobos and Deimos would have little effect on
Mars, so instead of imparting angular momentum out to Phobos and
Deimos so they would slowly increase their orbital radii, they are
instead destined to crash into Mars. Please explain how the tidal
effect would have anything to do with how circular their orbits are,
and with their orbits being on Mars' equatorial plane. Perhaps you
can cite a scholarly reference that lends these abilities to the tidal
effect?

I have already read "in the literature" that the fact that the Sun's
angular momentum is so much lower than the rest of the Solar
system's total angular momentum is considered a "flaw" in the
presently held condensation theory. So what you say here is
evidently still at

That was a view held in the 1940s or 50s. What literature still
says it is a problem? Since then the reason for the Sun's slow
rotation has been found (and I already explained this). The Sun's
equatorial rotational velocity is currently 1.2 km/sec
approximately. Typical rotational velocities for very young solar
type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular momentum
as the planets (mainly Jupiter) and gradually lost it as the result
of a strong stellar wind (which is stronger for rapid rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find that
you're correct.

Take for example, the computer model that yields the presently-held
"Giant Impact Hypothesis" for the origin of the Moon. How much does
this model have to be "tweaked" to be held plausible, let alone
probable? A "Mars-sized" object in the early Solar system, before
Earth became a "planet" and was still a "proto-planet", would have
most likely come from outside the Solar system from another stellar
system. What are the chances of an object that size from outside
the

Why do you say it would have to come from outside? The inner solar
system was like a shooting gallery when the (proto)planets were
young.

Yes, a shooting gallery of smaller chunks of material, not Mars-sized
objects, which would be planet-sized objects soaring around while
Earth was still in proto- stage? Doubtful.

The inner solar system around the time of the Moon's origin had only a few
larger objects left.

Where did they come from? How can you be so certain? You assert that
the inner Solar system had larger objects? Yes, and they had accreted
material while on fairly stable, nearly circular orbits around the
Sun. So, from where did this Mars-sized object originate? Did it
accrete in a very elliptical orbit that just happened to cross Earth's
path so that it might one day give Earth just the perfect glancing
blow that would be required to knock off enough material that would
rise beyond the Roche limit, accrete into the Moon, have an almost
perfectly circular orbit around Earth only five degrees off the
ecliptic?

I only wish you could even begin to see all the flaws in this idea.

Solar system hitting, colliding with, proto-Earth? What are the

Chances are next to nil. But there were lots of planetesimals
within the solar system at the very early stages.

Planetesimals. Not planets. Think about it. A Mars-sized object on
some weird kind of trajectory in a forming Solar system with lots of
small chunks of stuff soaring around. The bigger chunks that were
that close to the Sun were on stable orbits similar to what we see
today, weren't they? Where could such a large chunk have come from
within the Solar system? And even if it did come from within the

Coalescence of those smaller chunks. Just like all the planets.

On what? an extremely elliptical orbit that eventually took it into
the path of the Earth? Again, what are the chances? The liklihood of
such an event is such that astronomers should not consider it to be
credible. It is, in fact, incredible that this is such a widely
accepted origin theory. There are too many variables that require
just the right "tweaks" of the computer model to make it work.

It's just another case of fixing the facts to the theory, rather than
the other way around.

Solar system, again, what are the chances of such a collision so
perfect so as to place enough material beyond the Roche limit so that
when that material accreted into the Moon, it would orbit Earth in an
almost perfect circle and almost dead-on the ecliptic?

You might like that GIH, but I think it stinks to high-heaven.

You're welcome to your own opinion.


chances that said impact would place enough material outside the
Roche limit of proto-Earth to accrete into the Moon? Computer
models can only take you so far. Sometimes it takes too many
"tweaks" to get a scientist what he (or she) wants.

The only real requirement was a "glancing" blow rather than a head on
collision. Given that, the chances are pretty good.

You didn't strike me as such a dreamer!

Suit yourself, the evidence supports a collisional origin for the Moon and
explains its composition (similar to the Earth's mantle), while capture is
difficult dynamically because it requires three bodies in close proximity.

The conventional idea of capture is worse than difficult, it is less
likely than the GIH. However, if two bodies began to form in almost
the exact same orbit around the Sun, and one body was just far enough
out in front so that there would be little mutual gravitational
effect, then another kind of capture might be possible. While the
body out in front would gather up all the "good stuff", the rearward
body would be able to accrete only the remaining dregs. That would
also explain the composition similarities and differences, as well as
the size disparity between Earth and Moon.

The frontal body is a tiny bit nearer to the Sun, so it orbits a tiny
bit faster than the rearward body. By the time it slowly gets out in
front far enough for the rear body to have a clear path for accretion,
most of the material has been taken by the front body, proto-Earth.
Due to the similarity of orbital distances from the Sun, it would take
a very long time before proto-Earth would come around to be behind
proto-Moon. By the time this happens, the accretion process might be
finished or nearly so. Earth creeps up on the Moon very slowly. At
some point, Earth's gravitational field begins to interact with that
of the Moon.

When this begins to happen, the Moon would appear from Earth to be
sizable and in what we presently call "last-quarter phase". By the
time Earth and Moon are perhaps 25-30,000 miles apart, their
gravitational effects would "sync in", and as they continued together
around the Sun at about 66,000 mph, the Moon continued to "lose
ground" and passed to the left of the Earth. It moved into what today
we call "new-Moon phase". Then Earth would move out in front, while
the Moon moved back around to the rear, or "first-quarter phase". The
Earth can no longer keep gaining on the Moon, because they have
captured each other gravitationally. So as both Earth and Moon keep
orbiting the Sun, the Moon, very near to the ecliptic, eases around to
the right of Earth, or "full Moon phase". Then to come full "circle"
(an almost perfect circle), the Moon begins to take the lead again,
slowly coming around to be out in front of Earth, or "last-quarter
phase" again, and the synchronized cycle continues to repeat itself to
this day.

Back then, the Earth and Moon both rotated on their axes much faster
than today. Full rotations would have been a matter of a few hours.
The longer time the Earth and Moon spent together, the more they
interacted tidally. The tidal effect caused both Earth and Moon to
slow their rotations. The smaller Moon slowed more quickly, and
became tidal-locked to the Earth, so it began to always show the same
face to Earth, its rotation rate synching in to be the same as its
orbital rate around the Earth. The Moon continued to sap angular
momentum from the Earth, which kept slowing the Earth's spin rate
while the Moon's orbital radius increased.

That brings us to the present day. The Earth and Moon continue to
orbit the Sun together in a race-like fashion. First the Moon is out
front (last quarter), then they are neck-in-neck (new Moon). Then
Earth goes out ahead (first quarter), and then they are neck-in-neck
again (full Moon).

This is called a "gentle capture". I don't expect it to become
popular, because too many people like the WHAM BAM, SORRY MA'AM giant
impact idea, which would probably raise more grant bucks for
astronomers, even though it's even more incredible than the Andromeda
galaxy colliding with the Milky Way!

It's just an idea, a gentle, mutual capture idea.

--
Happy Holidays!
and Warm Wishes for the New Year!
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
"There is a great warrior within all of us. What wakes yours up?"

Painius wrote:
On Mon, 19 Dec 2011 05:58:14 -0500, Painius
wrote:

On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of
captures or of processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place
both of Mars' moons in near-circular orbits almost dead-on Mars'
equatorial plane.

I have already read "in the literature" that the fact that the
Sun's angular momentum is so much lower than the rest of the Solar
system's total angular momentum is considered a "flaw" in the
presently held condensation theory. So what you say here is
evidently still at

That was a view held in the 1940s or 50s. What literature still
says it is a problem? Since then the reason for the Sun's slow
rotation has been found (and I already explained this). The Sun's
equatorial rotational velocity is currently 1.2 km/sec
approximately. Typical rotational velocities for very young solar
type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular
momentum as the planets (mainly Jupiter) and gradually lost it as
the result of a strong stellar wind (which is stronger for rapid
rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find
that you're correct.

Well, it appears that your doubt is actually realized. There are
recent publications that still list the Solar system's "angular
momentum problem" as having yet to be solved. I did read where the
idea about the Solar wind as having whisked away much of the Sun's
angular momentum is strongly credible. I read where other stars
similar in age to our Sun were also spinning slowly. I was unable to
find anything definitive about younger stars and their faster spins,
though. Perhaps you could provide a link as a pointer? To be clear,
I was unable to find any published material about observations of
differently aged stars and their associated spin rates.

I'll need time to give you the references, but if you go to the ADS and look
for astrophysics papers by decade, with title or abstract words such as
rotation solar type stars you should find some. If you want me to do this
work for you, you will have to wait until after the holidays as I have a
busy schedule.


One aspect that I read has to do with the Solar wind idea. This may
explain how the Sun lost a good deal of its angular momentum; however,
it fails to explain the second part of the angular momentum problem,
which is the extremely high angular momentum, compared with the Sun's
angular momentum, of all the bodies in the Solar system that orbit the
Sun. If the condensation theory is correct, then how did all the
material in the accretion disk take on so much angular momentum? I
don't see how the Solar wind in and of itself could have imparted to
all the orbiting bodies such a relatively high level of angular
momentum. Do you?

No, the condensing cloud had a lot of angular momentum to start with.
Possibly at early stages the rapidly rotating and highly magnetic protostar
could have transferred some angular momentum to the cloud from the central
object.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

On Mon, 19 Dec 2011 22:06:58 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Mon, 19 Dec 2011 05:58:14 -0500, Painius
wrote:

On Sun, 18 Dec 2011 22:54:07 -0000, "Mike Dworetsky"
wrote:

Painius wrote:
On Sat, 17 Dec 2011 10:06:37 -0000, "Mike Dworetsky"
wrote:


It isn't clear if the small moons of Mars are the result of
captures or of processes similar to that proposed for Earth's Moon.

It's difficult to conceive of a capture scenario that would place
both of Mars' moons in near-circular orbits almost dead-on Mars'
equatorial plane.

I have already read "in the literature" that the fact that the
Sun's angular momentum is so much lower than the rest of the Solar
system's total angular momentum is considered a "flaw" in the
presently held condensation theory. So what you say here is
evidently still at

That was a view held in the 1940s or 50s. What literature still
says it is a problem? Since then the reason for the Sun's slow
rotation has been found (and I already explained this). The Sun's
equatorial rotational velocity is currently 1.2 km/sec
approximately. Typical rotational velocities for very young solar
type stars are around 30 km/s or more. If the Sun is a typical
star, then it started with about the same amount of angular
momentum as the planets (mainly Jupiter) and gradually lost it as
the result of a strong stellar wind (which is stronger for rapid
rotators).

I doubt very much that current opinion says that this is a flaw.

Okay then, I stand corrected. I did read it recently, but I cannot
confirm the age of the paper. If I find it, I can expect to find
that you're correct.

Well, it appears that your doubt is actually realized. There are
recent publications that still list the Solar system's "angular
momentum problem" as having yet to be solved. I did read where the
idea about the Solar wind as having whisked away much of the Sun's
angular momentum is strongly credible. I read where other stars
similar in age to our Sun were also spinning slowly. I was unable to
find anything definitive about younger stars and their faster spins,
though. Perhaps you could provide a link as a pointer? To be clear,
I was unable to find any published material about observations of
differently aged stars and their associated spin rates.

I'll need time to give you the references, but if you go to the ADS and look
for astrophysics papers by decade, with title or abstract words such as
rotation solar type stars you should find some. If you want me to do this
work for you, you will have to wait until after the holidays as I have a
busy schedule.

Please don't put yourself out. As I said, I did a pretty extensive
search and was unable to turn up anything. Since it's a pretty
important issue with those who study the early Solar system, one would
think that I would have come across *some* little tidbit, but there
was nothing that I could find.

One aspect that I read has to do with the Solar wind idea. This may
explain how the Sun lost a good deal of its angular momentum; however,
it fails to explain the second part of the angular momentum problem,
which is the extremely high angular momentum, compared with the Sun's
angular momentum, of all the bodies in the Solar system that orbit the
Sun. If the condensation theory is correct, then how did all the
material in the accretion disk take on so much angular momentum? I
don't see how the Solar wind in and of itself could have imparted to
all the orbiting bodies such a relatively high level of angular
momentum. Do you?

No, the condensing cloud had a lot of angular momentum to start with.
Possibly at early stages the rapidly rotating and highly magnetic protostar
could have transferred some angular momentum to the cloud from the central
object.

That seems odd. It was the cloud that was condensing. The material,
in accordance with the condensation hypothesis, that was to comprise
the planets was in an accretion disk outside the cloud, a disk that
had somehow managed to form itself into a flattened area of dusty
material. How was it that the cloud was supposed to have transferred
angular momentum to this disk? How was it that, as this material
began to accrete into all the objects that orbit the Sun, it also took
on a tremendous amount of angular momentum? Yes, it must have come
from the central cloud, and I have set forth a manner in which this
could have happened. If you disagree with me, then how do *you* think
that it took place?

--
Happy Holidays!
and Warm Wishes for the New Year!
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
"There is a great warrior within all of us. What wakes yours up?"

Painius set the following eddies spiralling through the space-time
continuum:

Planet Mars rotates today at about the same spin rate as Earth,
actually a little slower than Earth. So if Earth had the Moon to slow
its spin rate, then what slowed the spin rate of Mars? Mars' two
little satellites, Phobos and Deimos, are hardly the likely
candidates to suck away Mars' angular momentum, because they are so
small.

Phobos is unique in the solar system in orbiting *inside* its planet's
stationary orbit distance. The stationary orbit is an unstable equilibrium
once tidal effects are taken into account, and since Phobos is the other
side of that equilibrium compared to Deimos (and any other moon of any
other planet, or any planet around the Sun) any tidal effect it has on Mars
would work the other way. Phobos is doomed to spiral in towards Mars and
eventually crash, with Mars' spin being ever so slightly speeded up in the
process.
--
ξ Proud to be curly - the entity formerly known as Prai Jei.

Interchange the alphabetic letter groups to reply

On Sun, 25 Dec 2011 11:22:49 +0000, Curlytop
wrote:

Painius set the following eddies spiralling through the space-time
continuum:

Planet Mars rotates today at about the same spin rate as Earth,
actually a little slower than Earth. So if Earth had the Moon to slow
its spin rate, then what slowed the spin rate of Mars? Mars' two
little satellites, Phobos and Deimos, are hardly the likely
candidates to suck away Mars' angular momentum, because they are so
small.

Phobos is unique in the solar system in orbiting *inside* its planet's
stationary orbit distance. The stationary orbit is an unstable equilibrium
once tidal effects are taken into account, and since Phobos is the other
side of that equilibrium compared to Deimos (and any other moon of any
other planet, or any planet around the Sun) any tidal effect it has on Mars
would work the other way. Phobos is doomed to spiral in towards Mars and
eventually crash, with Mars' spin being ever so slightly speeded up in the
process.

Yes, I read that, too, Curlytop. And I wondered... since Phobos is
inside Mars' Roche limit, why wouldn't it just break up into a
planetary ring rather than crash into Mars? I kept reading and found
that astronomers say that either one might happen.

--
Happy Holidays!
and Warm Wishes for the New Year!
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
"There is a great warrior within all of us. What wakes yours up?"

Dear Painius:

On Dec 25, 9:15*am, Painius wrote:
On Sun, 25 Dec 2011 11:22:49 +0000, Curlytop
....
Phobos is unique in the solar system in orbiting *inside*
its planet's stationary orbit distance. The stationary orbit
is an unstable equilibrium once tidal effects are taken
into account, and since Phobos is the other side of that
equilibrium compared to Deimos (and any other moon of
any other planet, or any planet around the Sun) any tidal
effect it has on Mars would work the other way. Phobos
is doomed to spiral in towards Mars and eventually crash,
with Mars' spin being ever so slightly speeded up in the
process.

Yes, I read that, too, Curlytop. *And I wondered... since
Phobos is inside Mars' Roche limit,

Is it?

why wouldn't it just break up into a planetary ring rather
than crash into Mars? *I kept reading and found
that astronomers say that either one might happen.

If it is one fused mass, then it is not internally gravitationally
bound. So it could not "disperse".

David A. Smith

Painius wrote:
On Sun, 25 Dec 2011 11:22:49 +0000, Curlytop
wrote:

Painius set the following eddies spiralling through the space-time
continuum:

Planet Mars rotates today at about the same spin rate as Earth,
actually a little slower than Earth. So if Earth had the Moon
to slow its spin rate, then what slowed the spin rate of Mars?
Mars' two little satellites, Phobos and Deimos, are hardly the
likely candidates to suck away Mars' angular momentum, because
they are so small.

Phobos is unique in the solar system in orbiting *inside* its
planet's stationary orbit distance. The stationary orbit is an
unstable equilibrium once tidal effects are taken into account, and
since Phobos is the other side of that equilibrium compared to
Deimos (and any other moon of any other planet, or any planet around
the Sun) any tidal effect it has on Mars would work the other way.
Phobos is doomed to spiral in towards Mars and eventually crash,
with Mars' spin being ever so slightly speeded up in the process.

Yes, I read that, too, Curlytop. And I wondered... since Phobos is
inside Mars' Roche limit, why wouldn't it just break up into a
planetary ring rather than crash into Mars? I kept reading and found
that astronomers say that either one might happen.

The Roche Limit applies to satellites large enough to be pulled into a
spherical shape by gravity (i.e., behaving like a liquid drop). Phobos is
small and decidedly non-spherical, so it is held together by
chemical/electrostatic bonds rather than by internal gravity. Thus it is
more resistant to tides than a larger moon of spherical shape.

It is just outside the Roche Limit rather than being inside it. But as it
descends through the limit, depending on exactly what forces hold it
together, at some point it will probably break up into a ring.

--
Mike Dworetsky

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