Liquid CO(2) is not going to just materialize

Posted by
Amaranth Rose on Mar 20, 2002 at 19:35

Re: Now Where did all that CO2 come from? (Mike Kremer)

I'm having a little trouble with the idea of liquid carbon dioxide existing anywhere on Mars or Earth long enough to flow anywhere. Perhaps there's something I'm missing, or maybe the laws of Physics have changed since I was a young sprout.

Liquid carbon dioxide is used in the preparation of biological samples for electron microscopy. In order to produce it in liquid form for laboratory uses one must compress it to greater than 5.1 atmospheres (don't know what that would be in Pascals, sorry) in a pressure chamber. You don't want to touch the walls of the pressure cylinder, either; they get extremely cold, something like -50 to -60 deg. F. The pressure cylinders are double-walled, as I recall, both for insulation and so that in case the inner cylinder should shatter, the shrapnel is (hopefully) contained. Laboratory science is not always the safest occupation.

As the attached diagram will show, Liquid carbon dioxide doesn't exist at temperatures and pressures found anywhere on Earth, excepting perhaps at the very extreme depths in the oceans.

Carbon Dioxide Phase Diagram

Mars, being a smaller planet with even less gravity, would have less atmospheric pressure, I would think. This was the topic of a NASA "Thursday's Classroom" (q.v.) a few months ago.

Given that liquid carbon dioxide does not seem able to exist below 5.1 atmospheres of pressure, and Mars can barely be said to even have an atmosphere, I am having a hard time seeing any rational basis for the idea of liquid carbon dioxide even existing on Mars for even a few milliseconds, let alone lasting long enough to flow anywhere or move anything.

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