Good question! If I had to guess...we have a planet that evaporates/sublimes CO2 ice and H2O ice at the summer pole, and condenses/freezes those molecules at the winter pole. The atmospheric pressure is well below the partial pressures of those vaporizing reservoirs. Am I over-simplifying the cycle? I am guessing (with fingers crossed), that the poles exchange condensibles.

We've had discussions here regarding frost. I don't have much to say about that, but I did notice the word "frost" appear in association with some sol 60 SSI images. They were described as "SSI Frost Spot of Snow White16AB," "SSI Frost Spot of Winkies & Quadlings16AC," and ""SSI Frost Spot of Nightengale16AD."

There were RGB filters available for these 3 "target" images. Here are the raw jpg RGB composites, with no subjective color balancing applied.

Snow White
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Winkies & Quadlings
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Nightengale
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I think the scales are so utterly different as to bear no relationship:

The smooth/rough impression comes from MOLA maps, which emphasize difference on the scale of hundreds of meters or more. The soil overlying the ice is centimeters -- we're talking about several orders of magnitude difference.

My take is that the smooth/rough difference between the poles is about a single catastrophic flow event that buried the lower elevations planet-wide in slurry and paved over the cratered highlands.

The subsurface ice at these latitudes is probably something that would seep back in in a whisper of geological time if you removed it and let it emplace itself anew, but not on a scale to erase massive craters and canyons in the ancient highlands.

"I'll add another question: how much mass transfer of moisture is there between the poles?

Does Mars have a global circulation or could the water be hemispherically locked somehow?
(i.e. The North has it's water vapor, the South has it's water vapor, and never the two shall mix)"

According to Read and Lewis (The Martian Climate Revisited) there is a net transport of water from the north to the south. During northern summer some of the water ice of the cap melts and gets into the atmosphere as vapour. this then gets transported to the south where it freezes onto the polar cap. During southern summer water ice in the southern cap does not get exposed (the south is much higher) and so there's not so much water vapour coming back.

But these kinds of theories can change with more data.

Reminder

Phoenix News Conference
Tomorrow: July 31, Thursday
2 p.m. EDT = 6 p.m. GMT/UTC

According to the NASA TV web site - it's still on

NASA TV Schedule

July 31, Thursday
2 p.m. - Phoenix Mars Lander News Conference - Tucson/JPL (Public and Media Channels)

Jack

Poor "Alice" really got her face pushed down into the dirt by that robot arm, didn't she...

Click to view attachment

Seems like it's time for a new thread; carry on with the discussion over here
http://www.unmannedspaceflight.com/index.php?showtopic=5359

--Emily