The Dry Ice 'Snowflakes' of Mars

astroengine writes "After collecting the vast quantities of data gathered by orbiting Mars spacecraft, MIT scientists have uncovered some rather interesting facts about Martian snow. For starters, as the majority of the Mars atmosphere is composed of carbon dioxide, the snowflakes are made from CO2 ice — basically tiny particles of 'dry ice.' Also, the snowflakes are very small — approximately the size of a red blood cell. 'These are very fine particles, not big flakes,' said MIT assistant professor Kerri Cahoy in a press release. If you saw these 'snowflakes' fall, 'you would probably see it as a fog, because they're so small,' she added."

Aerosol formation

[relikx]

I assume even with the smaller size the mechanics for formation are more or less the same as rain and snow here on earth. If so, it could be possible that microorganisms past, present, or imagined would play a part in the process at times to assist in precipitation. Of course for something to live at temps low enough to live through dry ice formation would be nothing like here on earth, but if they are capable of withstanding extreme conditions that could be a place to find them.

Re:Aerosol formation

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There is a place called the "Dry Valleys" high in the Antartic mountains that is considered the best terrestrial proxy for Martian conditions. There has been no rain or snowfall there for two million years and it can get cold enough for dry ice to form (whether it does or not I don't know). Of course it has a denser and different atmosphere, but like Mars the humidity is for all practical purposes zero.

From the oblig. WP article: "The unique conditions in the Dry Valleys are caused, in part, by katabatic winds; these occur when cold, dense air is pulled downhill by the force of gravity. The winds can reach speeds of 320 kilometres per hour (200 mph), heating as they descend, and evaporating all water, ice and snow." Note that it states the ice "evaporates", as with Mars, water ice normally sublimates directly into the atmosphere rather than running off as melt water. Despite having similar tempratures and moisture levels to those found on Mars the WP page lists two groups of bacteria that are native to the area. One group lives inside granite the other underneath a glacier that protrudes into one of the valleys.

Life is incredibly durable, once it takes hold of a planet I find it hard to believe that anything short of a Venutian style "runaway greenhouse" will erase it. If life did once take hold of Mars in the distant past then I think it follows that it is still there,most probably just below the surface.