BTW. You may want to change the ‘BS’ to “Blind Squirrel’ there as the acronym BS can be mistaken as being rude. I’m okay with it & am just sayin’ in case you don’t know.

Gosh, I hadn’t noticed.

BS

Stevo R @ # 27 sez: “Hey, there’s always an exception that proves the rule!”

What does that mean?

What Jack Hagerty (39.) said. It was intended humerously.

BTW. You may want to change the ‘BS’ to “Blind Squirrel’ there as the acronym BS can be mistaken as being rude. I’m okay with it & am just sayin’ in case you don’t know.

Mmmmmmmm, chocolate!

He’s not dead, he’s pining for the fjords!

It’s a saying that is misused and misunderstood almost as much as “Money is the root of all evil” (instead of “love of money is the root of all evil”).

In this case “proves” was badly translated (I’m not sure the original language, I think it was French). In the original language it was closer to “tests.” This makes a lot more sense. Having a rule “proved” by its exception is like throwing out the outliers in a data set, it’s exactly the opposite of what it’s saying. Having the exception “test” the rule means that you have to think things through and make sure your theory is still valid.

- Jack

We really don’t know the color of the infalling material from the Phoebe Ring recently discovered by Spitzer, so “red matter” may be jumping the gun a bit. The thickness of the ring points to Phoebe, whose surface is most definitely *not* red but grey, as the source, and dynamical models tell us that the leading hemisphere of Iapetus is smacked “like bugs on a windshield” by small ring particles (while large ones stay resident in the ring).

Iapetus is not “sprinkled” by a gentle “rain” of ring particles either; impact velocities are on the order of 10 km/sec. So there must be some process by which the leading hemisphere of Iapetus reddens. Either Phoebe ring particles are grey and the surface of Iapetus reddens when ring particles mix with native Iapetus material or Phoebe ring particles redden as they make their way to Iapetus. Iapetus hasn’t given up all of its secrets yet!

@Bandsaw: Interesting question. The thermal migration model may indeed explain the distribution of dark material on Iapetus, but the ring dynamics tell us that dust impacts on Iapetus from the Phoebe Ring are still occurring.

in re:

http://blogs.discovermagazine.com/discoblog/2007/10/11/two-faced-moon-shows-its-true-colors/

Lol, they both used “Like bugs on a windshield” in their descriptives. Although I can see small differences between Bad Astronomy and Discoblog’s reports, they do appear to be essentially the same.

Hey, there’s always an exception that proves the rule!

What does that mean?

BS

EDIT: I don’t know if this is the same explanation from over two years ago, or a slightly different one, or maybe this was the explanation at a much earlier stage:
http://blogs.discovermagazine.com/discoblog/2007/10/11/two-faced-moon-shows-its-true-colors/

Not only a poor spraypainting job, but they also forgot to file the mold lines off. Shoddy workmanship on Iapetus all around.

And not a single fijord either!

Very poor job – all that ice and no fijords, poor workmanship indeed!

Don’t get me wrong, I thought the most recent Star trek was a good movie in many ways – great dialogue, good characterisation, fast paced and surprising twists, we finally got Uhura’s first name and so forth but that “red matter” gimmick had me thinking : “Oh Puh-leese that’s just dumb, coudn’t you have come up with something better!”

Also I thought that theory about dust and ice migration explaining Iapetus’es two-faced aspect had been around for a while? Wasn’t it one of a couple of theories proposed ages ago along with the dust shed by Phoebe and other moons idea? Not that I mind hearing about it again – any excuse to visit the Saturnian system is cool with me!

While I’m on being nit-picky and contrary :

Well, everything about Saturn and its moons is weird.

Not its chemical composition – being mostly hydrogen and a bit of helium is pretty much standard for gas giant planets – and stars, brown dwarfs and interstellar nebulous clouds too! Hey, there’s always an exception that proves the rule!

@ 7. ND Says: “That’s no moon” & 19. cardoso Says: “Because it´s not a moon, it´s a space station.”

I think you might be thinking of Mimas with its huge Herschel crater doing the “Death Star” impression instead!

See : http://en.wikipedia.org/wiki/Mimas_(moon)

Astronomers have supposed that there must be reddish dust or some other junk floating around Saturn, and the leading half of Iapetus slams into and accumulates it like bugs on a windshield. The thing is, the entire hemisphere is not coated! Plus, the boundary is complicated and sharply-defined, so clearly there must be something else going on.

At least that is what Dr. Plait said about it (emphasis mine).

I’m just curious to know how the whole process got started. Apart from a malfunction in the space station’s exhaust port, or course, which we all know is not much bigger than a womp rat.

I believe Mr Plait describes tidal locking of our moon in his bad Astronomy book… (IVAN3MAN AT LARGE…zip it!)

The equatorial ridge is really bizzare… (I’ve been trying to paint it for a couple of years now, but I still can’t quite find a composition that will do the feature justice.)