New Iapetian image series Options

[TritonAntares]

Hi,
nice pic Phil - I didn't notice the 2 originals on the JPL/NASA page at all.
It'll may help to measure the depth of Snowman A and the hight of its central peak...

Have you tried to combine some of the Nov.27th images, probably getting some colored ones?

Bye.

[TritonAntares]

Hallo,
one probably better resolved and enlarged pic of the last far-encounter is on the JPL/NASA page.

Date: 2006-11-27
Distance: ~2 mio km
Resolution: 12 km/pixel

Sadly no color composite...

Bye.

[ugordan]

Sadly no color composite...

Me, I've stopped expecting color composites altogether. It's as though they're taboo for the team. That said, they do manage to pull off a good sharpening/deconvolution job on the grayscales.

[Ian R]

Colour composite with Lightness channel consisting of 10 stacked images:

[Rob Pinnegar]

Is Roland the prominent crater at the 11 o'clock position?

[Ant103]

My version made from one RVB picture (saturation at 200%) and 10 b&w stacked and added pictures. 200% approx. size.

Attached thumbnail(s)

 

[ugordan]

Pink Iapetus, now that's something you don't see every day!

[TritonAntares]

Is Roland the prominent crater at the 11 o'clock position?

Iapetus northern hemisphere:



Seems to be Roland due to its position and the large central peak.
But be careful, there are 4 prominent craters in this region - one at the bright-dark border ...

Bye.

[Michael Capobian...]

Is Roland the prominent crater at the 11 o'clock position?

Yes. Here's the Voyager-based map showing the Saturn-facing hemisphere of Iapetus, which closely matches this image. Roland is at the top.

Michael

[Phil Stooke]

ugordan: "Pink Iapetus, now that's something you don't see every day!"


It's a Valentine!

Phil

[JRehling]

Pink Iapetus, now that's something you don't see every day!

This could turn into a drug-related discussion...

[ugordan]

This could turn into a drug-related discussion...

You mean something like: "There are no bad drugs. Just bad trips." ?

[nprev]

Huh...that "yin-yang" aspect makes Iapetus look like one of the hemispherical views of Fritz Leiber's The Wanderer...art imitating life in yet another subtle way, albeit decades in advance.

Just struck me also how deep & pronounced all these craters are in comparison to those on the inner large icy moons. Is this difference perhaps due to fallout from Enceladus on the latter, as discussed on another thread, or are we seeing evidence of a thicker crust on Iapetus?

[JRehling]

Huh...that "yin-yang" aspect makes Iapetus look like one of the hemispherical views of Fritz Leiber's The Wanderer...art imitating life in yet another subtle way, albeit decades in advance.

Just struck me also how deep & pronounced all these craters are in comparison to those on the inner large icy moons. Is this difference perhaps due to fallout from Enceladus on the latter, as discussed on another thread, or are we seeing evidence of a thicker crust on Iapetus?

Remembering that Iapetus is a startling outlier (literally and figuratively) in terms of its distance from its primary (only likely captured asteroids rival it among the natural satellites in the solar system), I suggest that its distance is the prime causative factor.

Look at the crusts of Mercury and the Moon and the Moon's maria. They are all three "old". The oldest crust there is not much more than 25% older than the youngest. But the rate of cratering is profoundly different: The cratering rate changed so sharply around 4 GYA that relatively minor differences in age led to tremendous differences in the preserved-for-all-time proportions of craters left behind.

I think the difference between Iapetus on the one hand and Rhea on the other (virtually identical size and distance from the Sun) is that the heat of proto-Saturn kept Rhea slushy just a bit longer, letting its primordial lumps from coalescing round out and its largest proto-impacts to fade into the slush. Iapetus cooled faster and has kept its original lumps in a way that no body outside the asteroid belt could have because all the planets are too large and all the other midsize satellites are too close to their primaries.

As a result, Ceres and Iapetus are less spherical than Rhea, Titania, and Oberon, and even some of the smaller icy satellites of Saturn and Uranus.

The large craters are just another manifestation of the big, early impacts having been left untouched by any general crustal slushiness during that period.

[tasp]

or are we seeing evidence of a thicker crust on Iapetus?

To extend this discussion, consider Iapetus accreting from the primordial chaos. Iapetus (or more accurately, the proto-Iapetus) pokes along in its' orbit at 5000 KPH (or was it MPH? no matter) and takes ~80 days to loop around Saturn. Its' accretion process took much longer than any other 'big time' satellite in the solar system. During this longer coalescense, the Al27 in the incoming materials had longer to radiate its' heat to space, and Iapetus had longer to radiate the collisional heating from impacts that formed it. Iapetus will be the satellite most accurately we can describe as cold formed. The crust will have enormous bearing strength. As we saw in the Cassini pix, the lumpy, facety surface of Iapetus exists to this day. The 'cat scratch' feature (IIRC, SW of 'landslide crater') might record an extremely deep penetration into the solid body of Iapetus by the impactor that made the 'landslide basin'.

Assuming a formation via external agency of the equatorial ridge structure long after Iapetus accreted, the structure rests on the surface, is 20 km high (60,000+ feet high!!!), and to date, in the Cassini photos, we see no faulting parallel to the ridge.

Additionally, to date, we see no signs of volcanism, past or present, no geysers, plumes, mud pots or warm spots. Internal heat sources have been inoperative at 'softening' the crust for a very long time.

Something else reducing the heating to the interior of Iapetus ids it's distance from Saturn. Granted, Iapetus is tide locked to Saturn today, but of all the major satellites in the solar system, tidal braking of Iapetus was uniquely slow. Any power dissipated this way had ample time to radiate away in the cryogenic environment, to no or little effect.