[X] My Assistant

[Michael Capobian...]

One of the latest Cassini press releases states: "The gas planet's subtle northward gradation from gold to azure is a striking visual effect that scientists don't fully understand. Current thinking says that it may be related to seasonal influences, tied to the cold temperatures in the northern (winter) hemisphere. Despite Cassini's revelations, Saturn remains a world of mystery."

I've been trying to get more information on this effect ever since one of the first Cassini color images showed it. I asked some folks who were doing a poster on Saturn's atmosphere at the LPSC last year, and they appeared to know nothing about it.

It seems to me as a layman that the cause is pretty clear: reduced insolation caused by the combination of Northern winter and the shadows of the rings lowers the temperature, which causes the cloud tops to be deeper in the atmosphere. This in turn means more Rayleigh scattering, which makes it blue.

So what's the mystery?

Michael

[deglr6328]

Could it have something to do with the simple fact that water is bluish? Even ice absorbs more at the red end of the spectrum due to the overtone of an OH bond stretch. The (predominantly) water ice particles in the rings are certainly small enough to be transparent...