Fred was right. There is snow on Mars.

[link]

Not only is there snow on Mars, but the landscapes we see at Victoria and Gusev Craters might be covered in snow during high axial obliquity episodes. This is just one more unknown that might explain some of the chemical and physical details or maybe not.

Discusses it in more detail. It states the snow evaporates before reaching the ground:

NASA Mars Lander Sees Falling Snow, Soil Data Suggest Liquid Past.
September 29, 2008 --- NASA's Phoenix Mars Lander has detected snow falling from Martian clouds. Spacecraft soil experiments also have provided evidence of past interaction between minerals and liquid water, processes that occur on Earth.
A laser instrument designed to gather knowledge of how the atmosphere and surface interact on Mars has detected snow from clouds about 4 kilometers (2.5 miles) above the spacecraft's landing site. Data show the snow vaporizing before reaching the ground.
"Nothing like this view has ever been seen on Mars," said Jim Whiteway, of York University, Toronto, lead scientist for the Canadian-supplied Meteorological Station on Phoenix. "We'll be looking for signs that the snow may even reach the ground."
...
http://phoenix.lpl.arizona.edu/09_29_pr.php

Perhaps the snow can reach the ground as the temperatures drop.

Bob Clark

I did not see this thread and addressed this issue in the polar storms thread. I will expand here in response to Robert Clark.

Temperature is important but relative humidity is the prime concern for precipitation aloft vs. precip on the ground.

On Earth we see no low level clouds associated with virga. That is because the process that causes this is dry air at the surface.

We have seen low clouds at night and during max heating. We have seen frost in the trench, per NASA. This is not consistent with dry surface conditions. A dry tongue or low level inversion could exist on Mars to preclude the snow from reaching the ground but to reach this conclusion is speculation and not aligned with the visible data.

Robert remember, I look at all of the Purdy pictures.

Fred

Once you let the camel's nose under the tent ...

Since it is now known that precipitation can fall from Martian clouds at north polar locations and perhaps reach the ground, perhaps it will be accepted the same can happen at other locations:

Adsorption water driven processes on Mars.
D. Möhlmann
http://sci.esa.int/science-e/www/object/doc.cfm?fobjectid=36779

See also:

Reflectance of fog in Valles Marineris.
A. Inada
http://sci.esa.int/science-e/www/object/doc.cfm?fobjectid=36724

Bob Clark

Excellent. Maybe we can put this image in context. Fog for sure. No visible clouds.
No cumuliform or convective element. Looks like frost and fog to me.

Now tell me more about that Camel, Bob.

Fred

And more here from the BBC and the Pheonix findings on the Martian snow

link

http://news.bbc.co.uk/1/hi/sci/tech/7644125.stm