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Fraser
2005-May-09, 04:34 PM
SUMMARY: Saturn's moon Phoebe might have arrived at the planet after a long journey from the outer Solar System, according to new research from NASA. When Cassini analyzed the heavily cratered moon in June 2004, it found that it was ice rich, but covered with a thin layer of darker material. This is a similar composition to Pluto and the Kuiper Belt Objects. Phoebe likely started further out, but then was redirected towards the inner solar system through interactions with other objects. Finally, it was captured by Saturn into a stable orbit.

View full article (http://www.universetoday.com/am/publish/phoebe_outer_solar_system.html)

What do you think about this story? Post your comments below.

om@umr.edu
2005-May-09, 10:23 PM
An interesting story.

I doubt if there is a single measurement that will tell us whether or not Phoebe formed as part of the solar system.

In the past we might have imagined that isotope analyses would tell us whether or not an object formed as part of the solar system.

But analyses showed that isotopes and elements were not uniformily mixed in material that formed the sun and its planets.

For example, researchers at the University of Chicago reported in 1976 that the amount of mono-isotopic O-16 steadily increased in these classes of meteorites and planets:

L & LL Ordinary Chondrites < H Ordinary Chondrites < Earth, Moon & Differentiated Meteorites < Ureilites < Hydrous Matrix of Carbonaceous Chondrites < Anhydrous Phases of Carbonaceous Chondrites.

And a recent issue of Nature [volume 434 (2005) pages 619-622] shows that oxygen in the Sun itself may contain more mono-isotopic O-16 than the Hydrous Matrix of Carbonaceous Chondrites, but perhaps less mono-isotopic O-16 than the Anhydrous Phases of Carbonaceous Chondrites.

Levels of Xe-136 also seem to be higher in carbonaceous chondrites and in Jupiter than in the Sun, which contains more Xe-136 than the Earth.

With kind regards,

Oliver
http://www.umr.edu/~om

Guest
2005-May-10, 01:30 AM
I heard one writer once specualte that Perhaps this rogue body came from another solar system, like a stray body flug away from a different type Oort cloud, but they gave little info

This Universe Today article is very good to read

Greg
2005-May-10, 06:08 AM
It looks like a KBO by its composition, and its orbital characteristics suggest it was captured by Saturn from somewhere. The obvoius conclusion is that it is a KBO. IT is nice that there is one so relatively close to us for us to study in moer detail. Looks like it it pretty beat up, suggesting a rough journey into the solar system.

Greg
2005-May-10, 06:12 AM
As far as objects that could be from beyond the solar system, the more inclined the orbit from the equatorial plane of the solar system, the more likely it has been captured from beyond the solar system. In this regard, Pluto/Charon would be more likely to be extra-solar in orgin than Phoebe or Triton. Almost undoubtedly, all of the above are from our own system as Pluto really is not wildly off axis.

lswinford
2005-May-10, 02:44 PM
Now in a "stable orbit" around Saturn after traveling so far and so obviously suffering so much. I&#39;m glad its now got a good home. :D

Wouldn&#39;t it be interesting if some enterprising soul at NASA decided that a simple lander on Phoebe would tell us all we needed to know about Pluto, closing the book on it as we so enjoy doing with simple answers, and do it more cheaply than sending something to Pluto? Then maybe a century or two from now somebody goes or sends something to Pluto and discovers that it is entirely different. I doubt I would live so long so as to smirk over that one. :rolleyes:

wstevenbrown
2005-May-10, 03:33 PM
Stable, eccentric, retrograde orbit, if memory serves. Check me on this. S&T&#39;s satellite listing does not give rotation periods or orbital character. S

antoniseb
2005-May-10, 03:37 PM
Originally posted by lswinford@May 10 2005, 02:44 PM
I doubt I would live so long so as to smirk over that one.
The Pluto fly-by mission launches this winter coming up, and should get good detailed images and other data about Pluto in July 2015. If you eat your vegetables, exercise, and cut back on sugar and fat (or if medicine produces the right new miracles) you should be alive to at least get a hint of it.

The Ion-drive based missions could possibly have landers at both places within twenty years if we don&#39;t squander our resources trying to get men to Mars too early.

Nereid
2005-May-15, 02:29 AM
Originally posted by wstevenbrown@May 10 2005, 03:33 PM
Stable, eccentric, retrograde orbit, if memory serves. Check me on this. S&T&#39;s satellite listing does not give rotation periods or orbital character. S
Much mystery about how the irregulars got their present orbits (http://www.ifa.hawaii.edu/~jewitt/capture.html). Divorce S&T, start dating Nine Planets (http://www.nineplanets.org/phoebe.html).

wstevenbrown
2005-May-15, 03:22 AM
Nice link, with focus shifted to history. They didn&#39;t give orbital inclination or eccentricity. Am I asking too much? S

Nereid
2005-May-15, 03:54 AM
Originally posted by wstevenbrown@May 15 2005, 03:22 AM
Nice link, with focus shifted to history. They didn&#39;t give orbital inclination or eccentricity. Am I asking too much? S
No; try solar views (http://www.solarviews.com/eng/phoebe.htm), or JPL&#39;s SSD (http://ssd.jpl.nasa.gov/sat_elem.html), or JPL&#39;s HORIZONS (http://ssd.jpl.nasa.gov/horizons.html).

wrt the last link, isn&#39;t there a Chinese curse, be careful what you ask for ...?

Planetwatcher
2005-May-15, 10:31 PM
I think that is a good conclusion to draw considering the evidence at hand, and that Phoebe is Saturn&#39;s most distant known moon.

Nereid
2005-May-16, 12:12 AM
that Phoebe is Saturn&#39;s most distant known moon.
Actually, it&#39;s not ... as the link in my previous (02:29 AM, 15 May) post attests - 12 new, more distant than Phoebe satellites of Saturn were discovered earlier this year.

Planetwatcher
2005-May-16, 02:02 AM
That&#39;s why I specified known. Because I didn&#39;t know if any newly discovered moons off the bat were more distant then Phobe.

Nereid just said that 12 more discovered earlier this year are all more distant.

So now does that bring Saturn up to 42 total known moons, or am I still behind the times?

wstevenbrown
2005-May-16, 04:11 AM
49. 23 of which are exterior to Phoebe, subject to change without notice. ;) S