Why is Saturn's moon Iapetus shaped like a walnut?

An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually. If
it's below that line, then it'll eventually fall in.

Yousuf Khan

***
Boffins crack walnut-shaped Iapetus moon mystery • The Register
"Space boffins studying the puzzling mystery of Iapetus, the
walnut-shaped moon of Saturn, believe they may have discovered how the
strange body's unique equatorial ridge was formed. The mighty ridge at
some places stands 12 miles above the surface average – more than twice
as high as Mount Everest's summit is above sea level.

According to William McKinnon and Andrew Dombard, space-sciences profs
in America, the curious ridge results from the long-ago breakup of a
satellite body in orbit about Iapetus – a moon of a moon."
http://www.theregister.co.uk/2010/12...ridge_cracked/

"Yousuf Khan" wrote in message
...
| An interesting theory they proposed is that if a satellite is higher
| than the geosynchronous orbit line, it'll escape its host eventually. If
| it's below that line, then it'll eventually fall in.
|
| Yousuf Khan

Then Moon's been around for long time.
How long do we have to wait for "eventually"?

Yousuf Khan wrote:

An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually.

That theory implies that the height of a stable orbit would be
dependant on the rotational speed of the moon being orbited.

That doesn't seem right to me.

--
pete

On 12/13/10 10:19 AM, Yousuf Khan wrote:
An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually. If
it's below that line, then it'll eventually fall in.

Yousuf Khan

There is nothing magic about geosynchronous--What is a geosynchronous
orbit strictly depend on the rotation rate of the parent body.

Androcles wrote:
"Yousuf Khan" wrote in message
...
| An interesting theory they proposed is that if a satellite is higher
| than the geosynchronous orbit line, it'll escape its host eventually. If
| it's below that line, then it'll eventually fall in.
|
| Yousuf Khan

Then Moon's been around for long time.
How long do we have to wait for "eventually"?



The moon is receding SLOWLY from earth, like inches/year.
As it has been doing for a few billion years.

In message , Sjouke Burry wrote:

The moon is receding SLOWLY from earth, like inches/year.
As it has been doing for a few billion years.

Yeah, but when was the Moon ever in gravitational capture by the Earth?

In sci.astro message , Mon, 13 Dec 2010
11:19:05, Yousuf Khan posted:

An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually.
If it's below that line, then it'll eventually fall in.

It is not an interesting theory, because it is a thoroughly-understood
consequence of basic physical laws.

If the primary and secondary were to be a perfectly rigid bodies,
dissipating no tidal energy (which is impossible), there would be no
effect. One must think more about the case of only one or the other
being rigid.

If a "below" satellite is not strong enough for its size, *it* will not
fall *in*, since *it* will first become a *them*.

--
(c) John Stockton, near London.
Web http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, and links.
Correct = 4-line sig. separator as above, a line precisely "-- " (RFC5536/7)
Do not Mail News to me. Before a reply, quote with "" or " " (RFC5536/7)

On 12/14/2010 5:34 PM, Dr J R Stockton wrote:
In sci.astro , Mon, 13 Dec 2010
11:19:05, Yousuf posted:

An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually.
If it's below that line, then it'll eventually fall in.

It is not an interesting theory, because it is a thoroughly-understood
consequence of basic physical laws.

If the primary and secondary were to be a perfectly rigid bodies,
dissipating no tidal energy (which is impossible), there would be no
effect. One must think more about the case of only one or the other
being rigid.

If a "below" satellite is not strong enough for its size, *it* will not
fall *in*, since *it* will first become a *them*.

It's interesting because it doesn't seem to be an official law, like the
Roche Limit, but somewhat related to it. It could possibly be an
extension to that limit.

Yousuf Khan

On 13 Gru, 17:19, Yousuf Khan wrote:
An interesting theory they proposed is that if a satellite is higher
than the geosynchronous orbit line, it'll escape its host eventually. If
it's below that line, then it'll eventually fall in.

* * * * Yousuf Khan

***
Boffins crack walnut-shaped Iapetus moon mystery The Register
"Space boffins studying the puzzling mystery of Iapetus, the
walnut-shaped moon of Saturn, believe they may have discovered how the
strange body's unique equatorial ridge was formed. The mighty ridge at
some places stands 12 miles above the surface average more than twice
as high as Mount Everest's summit is above sea level.

According to William McKinnon and Andrew Dombard, space-sciences profs
in America, the curious ridge results from the long-ago breakup of a
satellite body in orbit about Iapetus a moon of a moon."http://www.theregister.co.uk/2010/12/13/iapetus_ridge_cracked/

Let a sphereical hot magnetic liquid spinn a near a strong magnet, it
probably will stretch out like a walnut and if it slowly chill off
there probably will be a ridge left. There is clear evidence of three
distinct parallel ridges on Iapetus, it really gives a appearance of
almost an artificial object. But probably it is stretches around same
equatorial line, where the magma breaken up again and again.

This lead me to beleive that Saturn finaly will have ridges just as
well, when it cooles of enough. And Saturn show at least 9 signs of
shredding mass around the equatorial lines. Probably living around the
equatorial lines is not that favorable it seems like there is most
forces there, i can bet that earths crust is thinner around the
equatorial lines then at the poles,

JT

Dear JT:

On Dec 15, 1:22*am, JT wrote:
....
i can bet that earths crust is thinner around the
equatorial lines then at the poles,

No, don't draw parallels to Earth. The crust is thicker under the
contenents, and thinner under the oceans.

The Moon however has a thinner crust on the side facing the Earth.

David A. Smith