[X] My Assistant

[Decepticon]

Here's what extrapolating the current SPICE kernels yields:

IAPETUS 2005 NOV 12 14:34:49 185078153 415,451 km arcmin=12.1
IAPETUS 2006 JAN 25 21:13:08 191495653 873,345 km arcmin=5.7

IAPETUS 2006 APR 11 17:16:28 198047853 602,419 km arcmin=8.3
IAPETUS 2007 SEP 10 12:31:28 242699553 1,259 km arcmin=2186.8

Posted by jmknapp

This time a little further out.

Jan. 2006 - 879,000 km - 5.3 km/pixel - eastern Cassini Region and transition zone, part ofthe "moat" posted by VP


If anyone has made a animation of the encounter please post it!

[Rob Pinnegar]

The notion posted above, regarding Hyperion's deep craters acting as crude "mirrors" that could focus sunlight on the dark spots, is a very interesting one.

We need to keep in mind that the crater walls are not smooth surfaces and this will of course decrease any such effects. Also, Hyperion's craters seem to have cone-like shapes, which suggests to me that they might preferentially reflect sunlight straight back into space (much like the laser reflectors left behind by Apollo).

I haven't looked at any shots of Hyperion recently -- are there any for which the Sun was almost directly "behind" Cassini when the picture was taken? If so, it might be interesting to look at the apparent brightness of the craters, to see if they are reflecting an inordinate amount of light back towards the Sun. If they aren't, this notion of ray-focussing on the dark crater floors might really have something to it.

I know this is a bit off topic for the Iapetus thread -- however, it's perhaps arguable that _anything_ regarding dark material on Saturn's icy moons, is at least partially on topic where Iapetus is concerned.

[ugordan]

It seems to me thermal conditions on Hyperion's dark stuff aren't that similar to those on Iapetus. While both have dark, heat-absorbing materials, keep in mind that Iapetus has a several times longer day and any material is going to be more efficiently "baked" than the stuff on the bottom of Hyperion's craters.

As far as the craters on Hyperion acting as crude mirrors, that idea reminds me somewhat of the chicken-and-the-egg problem. You'd need dark stuff so it melts through the craters, leaving them bowl-shaped. And yet, this idea suggests that their bowl-shaped appearance is responsible for the darkening in the first place. Lastly, I reckon the craters should be pretty steep not to reflect the majority of the diffuse light back into space.