Not if the meteoritic dust is composed of ice itself. Why do you assume that meteoritic dust in the vicinity of Saturn is the same as meteoritic dust in the vicinity of the Earth?

This stuff has been observed, as I noted earlier. It’s definitely dark (even ice dust would be reddened pretty heavily from high-energy particle alteration), and it’s falling on the Saturnian system. We don’t know the rate precisely, that’s a far criticism. (Cassini tried to measure it during cruise, but that didn’t work out.) But to claim we don’t know that it’s dark or that we have no idea of what the infall rate is seems insulting to the researchers who have actually made strides toward just that.

I seem to recall an article on the NASA Cassini site where they found evidence that the rings are 4.5 billion years old. That seems to contradict a lot of the young ring claims.

You’re quoting the exact same researcher that Phil’s original post was about. That’s not really supporting your case any more than before. Also, read the article. Larry hasn’t shown that the rings are older. All he has shown is at the space-weathering evidence may not be reliable. That’s a rather different thing (media hype aside).

Sad thing is, this rings-researcher actually does think that the rings are old. But I do have to at least acknowledge the legitimacy of the data that suggests the opposite. That’s science rather than ideology.

Not if the meteoritic dust is composed of ice itself. Why do you assume that meteoritic dust in the vicinity of Saturn is the same as meteoritic dust in the vicinity of the Earth?

“Also, remember that that’s one out of two lines of evidence for the young ring model.”

I seem to recall an article on the NASA Cassini site where they found evidence that the rings are 4.5 billion years old. That seems to contradict a lot of the young ring claims.

http://www.nasa.gov/mission_pages/cassini/media/cassini20071212.html

Saturn’s Rings May be Old Timers
12.12.07
SAN FRANCISCO, Calif. – New observations by NASA’s Cassini spacecraft indicate the rings of Saturn, once thought to have formed during the age of the dinosaurs, instead may have been created roughly 4.5 billion years ago, when the solar system was still under construction.

Larry Esposito, principal investigator for Cassini’s Ultraviolet Imaging Spectrograph at the University of Colorado, Boulder, said data from NASA’s Voyager spacecraft in the 1970s, and later from NASA’s Hubble Space Telescope, led scientists to believe Saturn’s rings were relatively youthful and likely created by a comet that shattered a large moon, perhaps 100 million years ago.

But ring features seen by instruments on Cassini — which arrived at Saturn in 2004 — indicate the rings were not formed by a single cataclysmic event. The ages of the different rings appear to vary significantly, and the ring material is continually being recycled, Esposito said.

“The evidence is consistent with the picture that Saturn has had rings all through its history,” said Esposito of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons.”

Esposito and colleague Miodrag Sremcevic, also with the University of Colorado, are presenting these findings today in a news briefing at the meeting of the American Geophysical Union in San Francisco.

“We have discovered that the rings probably were not created just yesterday in cosmic time, and in this scenario, it is not just luck that we are seeing planetary rings now,” said Esposito. “They probably were always around but continually changing, and they will be around for many billions of years.”

Scientists had previously believed rings as old as Saturn itself should be darker due to ongoing pollution by the “infall” of meteoric dust, leaving telltale spectral signatures, Esposito said. But the new Cassini observations indicate the churning mass of ice and rock within Saturn’s gigantic ring system is likely much larger than previously estimated. This helps explain why the rings overall appear relatively bright to ground-based telescopes and spacecraft.

“The more mass there is in the rings, the more raw material there is for recycling, which essentially spreads this cosmic pollution around,” he said. “If this pollution is being shared by a much larger volume of ring material, it becomes diluted and helps explain why the rings appear brighter and more pristine than we expected.”

Esposito, who discovered Saturn’s faint F ring in 1979 using data from NASA’s Pioneer 11 spacecraft, said a paper by him and his colleagues appearing in an upcoming issue of the journal Icarus supports the theory that Saturn’s ring material is being continually recycled. Observing the flickering of starlight passing through the rings in a process known as stellar occultation, the researchers discovered 13 objects in the F ring ranging in size from 27 meters to 10 kilometers (30 yards to six miles) across.

Since most of the objects were translucent — indicating at least some starlight was passing through them — the researchers concluded they probably are temporary clumps of icy boulders that are continually collecting and disbanding due to the competing processes of shattering and coming together again. The team tagged the clumpy moonlets with cat names like “Mittens” and “Fluffy” because they appear to come and go unexpectedly over time and have multiple lives, said Esposito.

Esposito stressed that Saturn’s rings of the future won’t be the same rings we see today, likening them to great cities around the world like San Francisco, Berlin or Beijing. “While the cities themselves will go on for centuries or millennia, the faces of people on the streets will always be changing due to continual birth and aging of new citizens.”

I haven’t heard that this fact is making astronomers “uncomfortable”.

I have, as a matter of fact. A fellow astronomer (non-dynamicist) once asked me about that exact issue.

1.) The albedo of the meteoroids in the vicinity of Saturn (if this value is high then even highly reflective rings can be very old)

Eh, what the meteroitic dust does to the color isn’t that poorly known. The range of possible albedoes is so small compared to the difference between pure ice and dust that it shouldn’t matter much.

2.) The density of meteoroids in the vicinity of Saturn (this affects how many impacts with ring objects occur over some period of time)

This is a bigger unknown (although you can estimate the rate from surfaces whose ages are based on crater-counts). Still, you’re probably talking a factor of 10 in uncertainty, which still doesn’t include the age of the solar system.

Also, remember that that’s one out of two lines of evidence for the young ring model. The other, dynamics of spreading, is based on totally different physics.

http://en.wikipedia.org/wiki/Phobos_(moon)#Future_destruction

“Phobos’ low orbit means that it will eventually be destroyed: tidal forces are lowering its orbit, currently at the rate of about 20 meters per century, and in 11 million years it will either impact the surface of Mars or (more likely) break up into a planetary ring.”

11 million years out of 4.5 billion is 408 to 1 odds against. The odds that we exist at a time when we can see Phobos are 408 to 1 against. I haven’t heard that this fact is making astronomers “uncomfortable”.

1.) The albedo of the meteoroids in the vicinity of Saturn (if this value is high then even highly reflective rings can be very old)

2.) The density of meteoroids in the vicinity of Saturn (this affects how many impacts with ring objects occur over some period of time)

So without direct sampling of nuclear decay in the ring particles estimating their ages seems a bit chancy with the poor data we have at the moment.

2. The coincidence of all the giant planets having rings isn’t quite as stringent, because current theory considers them each to be of different age. Saturn’s, at 100M years, is the youngest. The other ring systems are substantially older, making it that much more probably for all four giant planets to have ring at present.

3. Even if ring systems are ephemeral and Saturn’s very young, it doesn’t constitute that great a coincidence that we observe them. Since there is nothing particularly special about the mechanisms believed to be responsible for forming rings, there is nothing to prevent ring systems from forming repeatedly. Even if individual rings only last for a short period of time, in the lifetime of the solar system, a planet like Saturn may have had rings hundreds of different times.

4. If Saturn’s rings generate unease because of their seemingly remarkable coincidence, then does the current temporal-spatial coincidence that makes the moon and sun appear to be the same size in the sky, generating that eclipse image some religious wackos try to equate to the eye of god, cause similar unease, and are there astronomers out there developing theories to more elegantly explain that observation?

OK, I’m going to get brave.

I’ve had an idea for about 12 years. Haven’t discussed it. It came up, when I learned that some gas giants in M52 do not orbit stars in the nebula.

Statement: there are not enough debris in the asteroid belt, for the asteroids to have resulted from a planet.

Speculation: gas giant floats out of M52, through interstellar space and through our solar system. On the way through, it’s near by passage to Aster breaks up the planet; most of the pieces follow the rouge gas giant. As it passes Jupiter and Saturn and Neptune, these gas giants pull some of the debris from Aster to themselves, from the rouge. The rouge floats on out of the solar system, taking the rest of the debris from Aster with it.

This scenario may be placed at any frame of time. If 100M year ago, it would explain the youth of the rings on all our gas giants.