[Evgeniy Podolskiy]

Evgeniy Podolskiy  asked the Naked Scientists:
   
Is there any CO2-snow falling out of the air at the South Pole during extremely cold air temperatures? It is known that lowest temperature ever measured on Earth was -89,4 °C (1974, Vostok);

I guess that to crystallize CO2 we need to lower the temperature to minus 78 °C (hope this assumption is correct).

Should this mean that some CO2-snow should start falling out of the clear dry polar sky like on Mars? It is known how tiny the proportion of this gas in the air, but anyway.

We talked about this with one scientist who has spent few seasons at the Vostok - and he told me that he has no idea about the answer.

What do you think?

[Bored chemist]

CO2 solidifies at -78C and 1 atmosphere pressure, but there's only about 300 ppm of CO2 in the air so it's nowhere near freezing.