[X] My Assistant

[angel1801]

I have observed on the solar system simulator that Cassini will get within 338,000km of Hyperion on Frbraury 4, 2007. Since close encounters with Hyperion are rare, will Hyperion be imaged on this encounter?

[ugordan]

With the phase angle being so high and the encounter being not so close, I wouldn't expect many images.

[ugordan]

Turns out that instead of February 4, there was a much better encounter on the 17th, distance ~220 000 km.

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=102835
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=102793

That moon looks different every time.

[tasp]

Wow, look at all those crater chains.

Kind of like a Phobos tribute moon . . . .

[stevesliva]

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=102793

Is the lower-right sun-facing limb in this photo the huge basin that is centered in the awesome earlier closeup?

[Phil Stooke]

Yes, it is. And this view gives us, I think, the best view yet of the north polar region of Hyperion.

Phil

[nprev]

God, but that's a weird-looking object...surely nothing else we've seen in the Solar System is as battered.

Sorry; Hyperion is just so striking in some ways that it's difficult to express a reaction, much less an analysis.

[tasp]

A request for picture analysis:

If anyone feels inclined (and has more image processing savy than me), I would be interested in comparing the color(s) of the dark crater bottoms of Hyperion to Cassini Regio on Iapetus.

I suspect (but am always open to suggestion) that comparing the data values (is this possible in a JPEG image?) through as many filters as possible might be quite informative.

For instance, an image of Cassini Regio, taken, let's say through a blue filter, and a specific exposure time, let's find a nice image of Hyperion, same filter and exposure time, and compare the data values of the dark areas.

Now, let's further analyze pairs of pictures, taken through other filters and compare. Just because a dark spot on Hyperion has the same value as Cassini Regio seen through the blue filter, doesn't mean the values (and mutual ratios) will be the same for the other filters. But if they are . . .

Additionally, I assume the angle of the spacecraft camera to the sun is important and makes this much more complicated than I imagine. You're on your own figuring out that part.


Where I am headed with this is, if the dark crater bottom material of Hyperion is indistinguishable from the dark stuff on Cassini Regio, perhaps we need to consider a common external origin for the dark material in both places. Like leakage from Titan's atmosphere. Having additional samples of (apparently processed) Titanian materials to examine could be crucial to understanding Titan.

If we can learn more about Titan by looking over Hyperion and Iapetus a little more closely, then perhaps we might wish to revisit them in the extended-extended mission.

[ugordan]

I did a similar comparison a while ago. I used an average of portions of Iapetus' and Hyperion's discs and the results are very similar. Cassini Regio itself has color variations in stretched color similar to the difference between the two colors seen here. Note I haven't looked at dark craters on Hyperion specifically, but I do believe they are almost the same color as the rest of the moon, only darker. One also has to account for phase angle here and that's a major factor affecting UV reflectivity used in the stretched color views.

[tasp]

Thanks.

Awesome good work on that. If I saw that posting before it's significance escaped me at the time.

Somewhere here it seems someone posted the Cassini Regio color varies from west to east too, and I think you alluded to that by mentioning Cassini Regio has variations comparable to the difference between Cassini Regio's average and Hyperion.

To sort out the possibilities:

* Cassini Regio 'stuff' was dislodged from Iapetus and coated Hyperion-

well, if the material was solid or liquid (?) during the transfer to Hyperion, how do we preferentially get it in the Hyperion crater bottoms (but not the one that breaches the big cliff)?? What mechanism gets you from Iapetus to Hyperion?


* Dark stuff from 1 or more outie moons spirals in and coats Iapetus and Hyperion-

same problems as above and explaining the gradation of color across Cassini Regio gets tricky. Also, the 'Voyager' equatorial dots might be tough to explain this way


* some tarry 'proto' object broke up and fragments collided with Hyperion and Iapetus during their formation, and later was transported to their respective surfaces-

tough getting internal dark stuff from inside either object onto the surface in the observed patterns


* dark stuff, particular to Hyperion, makes it way to Iapetus-

quantity of material, and efficiency and existence of a process seem to be very difficult to reconcile


*a common origin for the dark material on both objects, from a source interior to either's orbit-

Bingo! We have an extremely massive orangey cloud, weakly gravitiationally bound to Titan. Evidence (from Miller/Urey experiment) that the orangey cloud can tholinize into brownish goo, and a possible transport mechanism, Saturnian magnetosphere/magnetotail transport. Additionally, transport from Titan will cause specific areal coverage patterns on Hyperion and Iapetus, that we do see. Since in Iapetus case, we have an object tide locked to Saturn encountering the discolorant in a specific segment of it's orbital arc, and the discolorant is dissipated or used up in less than the ~80 days between reapplications of the discolorant, we see a specific longitudinal expanse of the stain, modified north and south by decreased insolation, and by local slope and elevation differences. In Hyperion's cases, Hyperion can be in any orientation during passage through the discolorant, we see the dark crater floors everywhere, (except in the crater with the breached wall and floor higher than the adjacent terrain). Further, darkening only occurs on the crater floors as the sloping bowl of the crater concentrates the solar flux that catalyzes the reaction only on the crater floors.


Closer study of the 'dark' stuff on Iapetus and Hyperion would seem to be warranted to support and extend our efforts to understand Titan. We seem to have samples of Titan atmosphere preserved (apparently over eons) and we may be able to ascertain long term variations in the Titanian atmosphere by studying these materials.

This could be crucial information . . . . .

[elakdawalla]

An early Christmas present from the Cassini folks, with the January 1 PDS release already out. Here's a couple Hyperion images, IR3-GRN-UV3 combos, from rev 39, blown up to 200%. The images were calibrated with IMG2PNG but because the UV3 channel always comes out so dark I wound up fiddling with the colors anyway, so they're not strongly related to reality.



--Emily

[ugordan]

An early Christmas present from the Cassini folks, with the January 1 PDS release already out.

W00t, w00t! Thanks for the heads up, Emily!

[elakdawalla]

Bjorn told me The database additions will be posted some time soon.

--Emily

[ugordan]

I wound up fiddling with the colors anyway, so they're not strongly related to reality.

Actually, the second image looks pretty realistic natural-color-wise, based on my experience. It captures the overall hue of the moon very well, with only a slight enhancement of the bluer rim on that huge crater. Let's call it "enhanced natural color" for the sake of inventing names.