So, why are north facing slopes white, while south-facing slopes are dark?
It's not just craters... it's the mountains, too.
It's not just craters... it's the mountains, too.
If it's not just the lighting at the moment, perhaps the 'frost' on north-facing slopes hadn't had time to burn off.
Could be due to sublimation and/or condensation that varies with solar elevation angle (north and east facing slopes in hi-res images of Ganymede's north polar cap are bright due apparently to water ice frost that has been cold-trapped).
EDIT In this case this seems to be mostly or entirely due to the illumination geometry rather than variable albedo.
EDIT In this case this seems to be mostly or entirely due to the illumination geometry rather than variable albedo.
I do wonder. Contrast-stretching can do that sort of thing. But it sure looks like a real dichotomy.
My views on this are changing rather frequently ;-). Now I notice this nearby crater where only a part of the north-facing crater wall is bright - hardly an illumination effect:
Click to view attachment
Click to view attachment
Trying to keep up with all that is coming in now A quick thought is that a similar crater wall effect happens on Iapetus.
My read is that Tombaugh Regio was created in an explosion and the blast coated away-from-Tombaugh slopes white and that north-vs-south is a red herring. Of course, that may be wrong.
Doesn't look radial to me. Before these global mosaics I was thinking it looked like a wind of white deposition could blow out the SSW from Tombaugh Regio, but now it just looks more like Iapetus, as s.c.albers said...
With plenty of local exceptions, the trend in the southern hemisphere is South facing dark, North facing white, and the clincher is that it's not just crater slopes, but also mountain slopes.
With plenty of local exceptions, the trend in the southern hemisphere is South facing dark, North facing white, and the clincher is that it's not just crater slopes, but also mountain slopes.
Another possibility I would like to add is deposition of frost or snow on the windward slopes of topographical features. With the the sub-solar latitude in the northern hemisphere and the north pole in constant sunlight the sublimation will be in the north and freeze-out primarily in the south with the wind blowing roughly north to south with some trend to the west due to the Coriolis effect.
I wonder how the Pluto-Charon barycenter being outside Pluto affects the Coriolis effect.