[X] My Assistant

[SFJCody]

Seems to be a lot of dispute on this subject... I think it's ice from the interior, but what does everyone else think?

Edit:

This world seems very complex so the question could perhaps be phrased as 'which of these options is most responsible for the Iapetan dichotomy?'

[tasp]

I would pick transparent material everywhere, keyed to orbital position relative to Saturn, that only darkens upon exposure to sufficient heat/light from sun.

[David]

I would pick transparent material everywhere, keyed to orbital position relative to Saturn, that only darkens upon exposure to sufficient heat/light from sun.

I don't think this is possible; where black and white regions are adjacent, the white regions appear to be definitely higher in relief than the black (in some places high enough to cast shadows).

Now, that in itself doesn't decide white on black or black on white, because it could be produced either by icy material condensing and/or flowing over a dark background, or by a dark material heating up and causing the ice beneath it to sublimate until it ends up lower than the surrounding lighter regions.

However, it's not consistent with the same material merely undergoing a color change -- then you'd expect continuity in relief (and probably not such sharp boundarie, too).

Are we going to get information about the chemical composition of the surface materials from this pass?