[X] My Assistant

[jsheff]

The January PSG meeting is now in progress and the tour for extended mission is scheduled to be chosen on Thursday (Feb 1). There are 13 tours being considered OF4a, PF-3, PF-4, PF-6, PF-6h9, PF-7, PF-8, PF-9, PF-10, PF-11, PF-12 & PF-13 --plus 'tweaks' on these tours e.g. there is a PF-8a, PF-9a

S-S-So ... has anybody heard anything?

- John Sheff
Cambridge, MA

[john_s]

The winner is (drum roll please) PF6h9. Officially adopted on Thursday. I haven't sifted through all the details yet, but from my parochial point of view, I know it includes seven close Enceladus flybys, so that's good. Most of the science groups (Titan, Rings, Magnetosphere, Saturn, and Icy Satellites) were pretty happy with this choice- it packs in an amazing number of science opportunities.

John.

[tasp]

So, we seem to be at the point of saying dark dust deposited on Cassini Regio from Phoebe will look a certain way.

And eruptions of light colored materials onto a dark surface will look a certain way.

And a gaseous, thermoreactive darkening substance, introduced into the Iapetan environment during passage through the Saturnian magnetotail and either totally dissipated or totally used up in much less than the ~80 day period of Iapetus will look in a certain way.


And Cassini orbiter will get us the definitive pictures in September . . . .

[JRehling]

So, we seem to be at the point of saying dark dust deposited on Cassini Regio from Phoebe will look a certain way.

And eruptions of light colored materials onto a dark surface will look a certain way.

And a gaseous, thermoreactive darkening substance, introduced into the Iapetan environment during passage through the Saturnian magnetotail and either totally dissipated or totally used up in much less than the ~80 day period of Iapetus will look in a certain way.
And Cassini orbiter will get us the definitive pictures in September . . . .

I think there's a pretty good chance of that.

They can take a stab wound and determine where the assailant was relative to the victim. Or a bloodstain and determine the geometry of a gory deed.

The interaction between topography and the dark-light pattern is going to tell us a lot we don't know already.

We already know a lot, and it seems to thwart a lot of simple models. Particularly, the Snowman craters give us some trouble. But we've mainly seen the eastern border of Cassini Regio. The September flyby will give us a great look at the western border. That alone will tell us if CR was emplaced from east to west, west to east, or from inside out. Or none of the above, also a real possibillity.

I'm reminded of the pre-Apollo situation with three theories about the origin of the Moon. It turned out that a combination of two of them best explained the data. Maybe Cassini Regio had a single catastrophic event as its origin, but it has had a continuing evolution since then.

Callisto may offer a useful analogue in terms of the interaction of dark surface with brighter, more volatile ice. Iapetus must be a little more complex than that, but that may partly explain things.