Solving the mystery of Iapetus

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In summary: GarthIn summary, this paper discusses the mystery of Iapetus, a Saturnian satellite with a significantly darker leading hemisphere. The author proposes a model that explains this darkness and the presence of a large equatorial ridge, suggesting that it is the result of a collision with a primordial Saturnian ring. The paper also discusses the possibility of Saturn having had more rings in the past and the eroding effects on the current rings. The conversation also touches on the likelihood of Iapetus being tide-locked and its orbital inclination.
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wolram
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http://arxiv.org/PS_cache/astro-ph/pdf/0504/0504653.pdf

Title: Solving the mystery of Iapetus
Authors: Paulo C. C. Freire
Comments: Submitted to Journal of Geophysical Research - Planets

Since the discovery of Iapetus by G. D. Cassini, in 1672, it has been known that the leading hemisphere of this Saturnian satellite is one order of magnitude darker than the trailing hemisphere. Since the Cassini spacecraft entered the Saturnian orbit, several high-quality images of the dark hemisphere of Iapetus have been obtained, in particular during the Dec 31 2004 flyby of this satellite. These images revealed the presence of a large equatorial ridge in the dark hemisphere of Iapetus. We propose that this ridge and the dark coating of the hemisphere on which it lies are intimately interlinked and are the result of a collision with the edge of a primordial Saturnian ring, ultimately caused by a sudden change in the orbit of Iapetus. The model naturally explains all of the the unique features of this satellite; it is probably the solution to one of the oldest mysteries in solar system astronomy.

This paper discuses some of the possibilities for Iapetus orbit change
and its collision with saturns rings, but did saturn have more rings in one stage of its evolution?
 
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The rings of Saturn may not be permanent but erode through tidal, diffusion (collision) and Poynting-Robertson effects. Therefore the planet may well have had more rings in the past.

Garth
 
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  • #3
Garth said:
The rings of Saturn may not be permanent but erode through tidal, diffusion (collision) and Poynting-Robertson effects. Therefore the planet may well have had more rings in the past.

Garth

Thanks Garth, How long would it take for a ring large enough to cause
these effects to disappear?
 
  • #4
wolram said:
Thanks Garth, How long would it take for a ring large enough to cause
these effects to disappear?
How long is a piece of string? It depends on the perturbations that a ring suffers, in this case the most significant perturbation would be the collision with Iapetus!

Garth
 
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  • #5
Garth.
How long is a piece of string? It depends on the perturbations that a ring suffers, in this case the most significant perturbation would be the collision with Iapetus!

Yes silly question, It would have been an amazing sight though," if it were
observable from earth", and we were around.
 
  • #6
No not a silly question, just a rather ill determined one.

The default position would be to say the rings were formed as leftovers when the whole Saturnian (?) system was formed. They would therefore have a lifetime of greater than 5 billion years or so. However they are known to leak downwards into Saturn's atmosphere and outwards into the satellites' region.

It might be that we are seeing the system at an special time, say relatively soon after a satellite broke up through tidal forces, and normally the system looks like that of Uranus.

However it is normally assumed that that is not so and the rings are long lasting, but exactly how long is open to debate.

Garth
 
  • #7
You are very gracious Garth, the evolution of our solar system may be
a model, admittedly micro, but possibly macro, that demonstrates that
an almost insignificant event can alter the system.
 
  • #8
One-face moon

Moons interior to Iapetus' current position rotate. Iapetus is currently tide-locked. Why? The model requires four sequential unlikelihoods:

1) Iapetus was an interior moon for at least long enough for its rotation to synchronize with its revolution.

2) Its orbital inclination was 0 deg.

3) Something moved it into the path of the ring, or vice-versa, while maintaining Conditions 1 and 2, to provide the narrowly-defined ridge.

3) Something moved it outside tide-locking range while maintaining the tide-lock and shifting the orbital inclination by 7 deg.

I ain't buyin' it. Steve
 
  • #9
Moons interior to Iapetus' current position rotate. Iapetus is currently tide-locked.
Huh?

ALL Saturn's regular satellites (except Hyperion) are tide-locked!

(Or are you making a quite different point?)
 

1. What is Iapetus and why is it a mystery?

Iapetus is the third-largest moon of Saturn, and it is known for its unusually dark and light regions that create a "yin-yang" pattern on its surface. This moon is a mystery because its surface features are not fully understood and there are still questions about its formation and evolution.

2. What are the leading theories about the dark and light regions on Iapetus?

One theory suggests that the dark regions are made of organic compounds that have been brought to the surface by sublimation of ice from the moon's interior. Another theory proposes that the dark material is the result of geysers or cryovolcanism, while the light regions are made of water ice.

3. How has technology helped in solving the mystery of Iapetus?

Advancements in technology, such as space probes and telescopes, have allowed scientists to study Iapetus in more detail and collect data and images that help in understanding its features. This has also helped in developing and testing different theories about the moon's formation and evolution.

4. What is the current state of research on Iapetus?

Scientists continue to study Iapetus and analyze data from past missions, such as the Cassini spacecraft, which provided valuable insights into the moon's surface. There are also plans for future missions, such as the Europa Clipper, that will further our understanding of Iapetus and other moons in our solar system.

5. Why is it important to solve the mystery of Iapetus?

Understanding the formation and evolution of Iapetus can provide valuable information about the early history of our solar system. It can also help us better understand the processes that shape other celestial bodies, as well as provide insights into potential habitable environments beyond Earth.

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