[X] My Assistant

[Gsnorgathon]

A few new ones:

Do I see the central peak of a crater casting a shadow? And the bright traces of the crater's ruined rim at upper right? Since Hyperion's 1,543,330 km away, these "features" are near the limit of resolution - which makes them all the more fun to speculate about!

There's also a much closer one, from "only" 768,869 km. My putative Hyperion-sized crater is, conveniently enough, not visible in this view.

[Phil Stooke]

Gsnorgathon, yes, you do see a central peak. Compare this with the Voyager image sequence - at, for instance,

http://www.ssc.uwo.ca/geography/spacemap/hyindex1.htm

- and you can see a hill in the centre of that circular region, and its northern rim which is called Bond-Lassell Dorsum. The rest of the rim is not very clearly defined.

Also compare the 'much closer view' with the best Voyager images. The limb shape is the same but reversed left to right - this bew view is of the opposite side.

Phil

[Gsnorgathon]

Drat! And here I thought I'd made a Great Discovery. So much for Gsnorgathon Mons... I really liked the ring of that. :@(

Phil - as a cartographer, you must know a thing or two about nomenclature; is Bond-Lasell Dorsum likely to become just plain old Bond-Lasell (since craters don't seem to get "Crater" appended to their names)? And do you suppose that big crater was created on Hyperion before or after Hyperion got smacked by whatever smacked it into its current eccentric orbit and chaotic rotation? (Or did Hyperion get smacked?)

[Phil Stooke]

Hi - I don't think the name has to change. The crater itself does not have a name (it wasn't recognized as a crater when the few names were assigned). This is similar to many lunar mountain ranges, with individual names.

[Guest_Sunspot_*]

A few new Images of Hyperion:

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=47478

I noticed that Cassini passes fairly close to Hyperion today , at around 15:00 UT, see link below.

http://space.jpl.nasa.gov/cgi-bin/wspace?t...orbs=1&showsc=1

[Phil Stooke]

Here is a composite view of the images taken during the August flyby of Hyperion.



It is lower resolution than the June flyby (I also posted a composite of those images), but still better than Voyager resolution. It very conveniently fills the gap in Hyperion rotation that was missing in June.

The most prominent feature is the long curving scarp, Bond-Lassell Dorsum. Since it has a mound at its center I interpret it as the remains of a crater with a diameter about 80% of the long axis of Hyperion. Some people doubt that such large craters can be formed without destroying the target, but this is, I think, based on a misunderstanding of the physics of the cratering process. The crater is excavated by an expanding hemispherical shock wave, which loses energy as (i) some is used to eject debris, and (ii) it is spread out over a larger surface. By the time it gets to full crater size it has lost much of its disruptive power (or it wouldn't be at full crater size...) Only if the shock wave is still capable of digging a crater after it has fully traversed the target does the target get blown apart completely.

Deimos and Vesta both have craters this size, relative to their mean diameters, at their south poles. (Rapid rotators would preferentially reorient to place a giant crater at a pole).

Phil

[Palomar]

Spelunker's paradise?

*One of the best Hyperion images yet, IMO. I wish they would/could create a "movie" of Hyperion; if not entirely from all angles (which might be impossible, considering flight path, schedules, etc.) then from as many as possible. Hyperion can look so very different from pic to pic.

[Rob Pinnegar]

What is the approximate timescale of Hyperion's chaotic rotation? Would it actually change rapidly enough to make spacecraft landings hazardous, as suggested in Anderson's short story? Are we talking weeks, years, centuries or what?

If it really _does_ change rapidly, one advantage of the chaotic rotation is that we will be able to get maps of the whole moon a lot sooner than will be the case for the other major moons (due to their polar regions being in the dark).

On an unrelated note, I kind of enjoyed the discussion in this thread regarding the ranking of the moons with regard to how interesting they are. This of course raises the question of which major moon is LEAST interesting (leaving out the tiny rocks since they are already at a disadvantage).

My vote would be for Rhea, but even Rhea has a "dark area" and those two adjacent basins. It sure isn't in the same league as Umbriel or anything like that. (Yeah. A white crater. Ya-hoo.)

[Phil Stooke]

The idea that Hyperion rotates chaotically comes up so often that it really does need correcting. Back in the 80s Hyperion was said to be in chaotic rotation, and a google search today turns up lots of references to those statements. But look at this paper:

Thomas, P.C., Black, G.J. and Nicholson, P.D., "Hyperion: Rotation,
Shape and Geology from Voyager Images", ICARUS 117: 128-148, 1995.

and you will see the current view. The rotation is not chaotic, it is the same type of rotation experienced by Halley's nucleus, asteroid Toutatis and (no doubt) lots of other slow rotators: a "slow long axis" mode, rotating about the long axis instead of the short one, but with rapid precession about a steeply inclined angular momentum axis. This will undoubtedly be refined with Cassini data, but if you look at the motion of the terminator in both the June and August flybys, they are quite consistent with rotation about the long axis.

Phil

[Palomar]

*I've most often seen Hyperion's motion referred to as "tumbling." As we know, it does have a "long, looping" orbit.

Hyperion Hoopla

Is one of my favorites regarding this moon from the NASA/JPL Cassini site.

Another, rather amusing:

Does look like a face...particularly the Pringles Potato Crisps "guy."

P.S.: Saturn's most intriguing moons? Titan and Enceladus.

[Rob Pinnegar]

Thanks for the reference, Phil. Our library's web server is down for repairs right now, but I'll check it out come Monday. Sounds interesting.

And...the "Face on Hyperion"? Geez, don't anybody let Richard Hoaxland find out about it!!! He'll find some crazy way to connect it with his Super-Sixty-Sided Iapetus Death Star theory for sure. (Can someone please take away that guy's JPEG compressor before he hurts himself with it?)

[Long after the fact edit: Altered Hoaxland's name to keep Googling kooks away, here and in other posts.]

[Bob Shaw]

Thanks for the reference, Phil. Our library's web server is down for repairs right now, but I'll check it out come Monday. Sounds interesting.

And...the "Face on Hyperion"? Geez, don't anybody let Richard Hoagland find out about it!!! He'll find some crazy way to connect it with his Super-Sixty-Sided Iapetus Death Star theory for sure. (Can someone please take away that guy's JPEG compressor before he hurts himself with it?)

Rob:

No, give him a BIGGER one, with sharpened ends!

Bob Shaw

[Phil Stooke]

Hyperion has a face? I'll bet it's not as convincing as the Nose of Prometheus! Yes indeedy, check out the best Voyager image of Prometheus, and there at the north pole is a gigantic sculpture of a nose. It must be 50 km long at least. And not just any nose... it's Elvis's for sure. But the north pole is in shadow at this season, so Cassini can't check it out. Coincidence? I think not!

Phil

[mike]

Yeah, we all know that Cassini himself was never a fan of Elvis - he even went so far as to call him 'nothing more than a pelvis-shaking titillater of horny loser broads'. How Cassini could argue with the life-affirming melodic declaration that is JAILHOUSE ROCK, I'll never know! DON'T STEP ON MY BLUE SUEDE SHOES, YOU AIN'T NOTHIN' BUT A HOUND DOG, A MOTHER CRIES... IN THE GHETTO

[Rob Pinnegar]

Hmm. I was not aware that a giant replica of Elvis' nose had been found on Prometheus. You learn something new every day in this forum.

This raises the question of where the rest of him has gone. Is it possible that his sideburns ended up draping over Iapetus? Could Telesto and Calypso be his detached ears? Is Hyperion a giant replica of the last cheeseburger he wolfed down? We can only wonder.

On the whole, this revelation would probably be of great interest to the Hoaxlandites, for two reasons. First, the Voyager photo of Prometheus is fuzzy enough to make JPEG tampering unnecessary, which would save them a lot of time and effort. Second, any discovery of a giant nose immediately raises the prospect of some outlandishly contrived connection with Easter Island, the details of which would likely keep them occupied for some time to come. (Everyone needs a hobby.)

Did Elvis ever visit Easter Island, perhaps during his time in the Army? If not, it should be possible to make something up. A "transdimensional gateway" would probably suffice.

Maybe I'll write this up, and submit it for peer review at the Weekly World News.