Sol 22 and after, Digging in Wonderland Options

[fredk]

Snow White is looking really battered now...

Thanks for the colour frame, Stu. I'm impressed with the absolute positioning accuracy for the arm: They've put the new set of (16?) rasp holes almost perfectly between the first set of 16. That's sub-centimetre accuracy!

Teck - I've been watching and the sublimation rate at Dodo/Goldilocks has dramatically slowed from the early sols. Perhaps it's reaching an equilibrium, with sublimation matching frost depostion?

[hendric]

Do you want some sublimation?

Heck, you don't need an animated GIF, that last image clearly shows that the icy parts are deeper now than the non-icy. Check out the shadowing along the edge.

[fredk]

Here's two comparison blinks of Snow Queen, sol 21 - 44 taken from slightly different positions and angles... Some of the changes are clearly real like the moving sand grains... The rest are less clear...cracks, trails of rolling particles, or shadows?:
Snow Queen A
Snow Queen B

Well, this is pretty old news for us folk, but in this new update they discuss the changes between sols 21 and 44:

Cracks as long as 10 centimeters, or about four inches, have appeared. A seven-millimeter (less than one-third inch) pebble or clod not seen there before has popped up on the surface. And some smooth texture on Snow Queen has subtly roughened.

I'm a bit surprized by the cracks claim - my best guess was tracks left by pebbles - we can see some have moved between the frames.

[nprev]

Meanwhile, over in 2D land, poor Snow White is looking really battered now...

Sure is, and if my hypothesis is valid then so will every other dig in this area over time.

Hmm. Going out on a limb here. The North Polar region (Vastias Borealis) is very smooth and quite broad in terms of surface area, while the South Polar region really isn't, except at very high latitudes, and even then it ain't the same. Impact cratering rates would presumably be statistically equal for both regions. There does seem to be a mechanism for autosmoothing of terrain in the north, namely subsurface ice exposure/sublimation/mass repositioning. Does this mean that subsurface water ice is preferentially concentrated in the North Polar region....and, if so, why?

I understand that the Southern Hemisphere is orographically higher than the north, but does a difference of just a few millibars of atmospheric pressure at most make that much of a difference in the behavior of ice sublimation/deposition? The hemispheric dichotomy is puzzling, even considering surface topography. Is there a similar dichotomy in crustal composition between the poles?

[Juramike]

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)

[CosmicRocker]

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

Winkies & Quadlings

Nightengale

[JRehling]

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.

[remcook]

"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.

[stewjack]

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

[Stu]

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

[elakdawalla]

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