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MichaelT
A publication accepted by JGR describes how the orbit of Mars around the sun could affect the deposition of water-ice at the Martian South Pole. Possibly, the buildup and erosion of water ice is coupled to the precession cycle of Mars. This was deduced from Mars Express observations and a model of the Martian climate.

It is also described that the erosion of water ice at the Martian South Pole was stopped by the formation of CO2-ice only about 1000 years ago. This CO2 now suits as a cold trap and enables the formation of water ice in a small area around the pole (south of 87S).

All the details can be found in this ESA press release:
http://www.esa.int/SPECIALS/Mars_Express/SEMKZRNSP3F_0.html

Michael


'On the origin of perennial water ice at the South Pole of Mars: a precession-controlled mechanism?', by F. Montmessin, R. M. Haberle, F. Forget, Y. Langevin, R. T. Clancy and J.-P. Bibring, accepted for publication in the JGR Planets journal, and presented at the 7th International Conference on Mars, Pasadena, California (9-13 July 2007)
MarsIsImportant
Did I read that correctly?

There is a 51k year water cycle on Mars. And the CO2 ice cap only started forming 1k years ago. That has drastic implications. The Martian atmosphere is much thinner because of that CO2 ice cap. Does this mean the Martian atmosphere was thicker in the recent past?
MichaelT
That's how I read it, too. And I was just as surprised.

QUOTE
Does this mean the Martian atmosphere was thicker in the recent past?

You could be right, if there was no CO2 ice at the North Pole of Mars before that time. Unfortunately, this is the first time that I read about these time frames and I don't have any other info on that topic.
Does anybody else?

Michael
MarsIsImportant
Here is a different article on the water cycle.

http://www.space.com/scienceastronomy/070713_mars_ice.html

It says the water cycle stopped. It also says that scientists don't know why it stopped. Yet, the start for this thread clearly suggests it was stopped by the deposition of CO2 on top of the water.

I wonder how accurate that 1000 year figure is for the start of the CO2 polar deposition. If it is accurate, then what created the conditions for the CO2 to start falling out of the atmosphere. Were there other episodes in the distant past where other gases started falling out of the atmosphere?
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