Doug Haxton :

On 3 Sep 2003 23:02:36 GMT, (Ron Baalke)
wrote:


"These findings suggest that even under worst case scenarios, where wind
is
maximizing evaporation, evaporation rates on Mars are quite low," Sears
said.
This implies that surface water could indeed exist, or have existed
recently,
under the given conditions on Mars.

Waitaminute...the pressure of the Martian atmosphere is only about 1%
that of Earth's at sea level, right?

Wouldn't any surface water just boil away?

Doug

No, if the water is cold enough, also gravity affects the boiling rate as the
water pressure prevents the water further down from boiling right away. Thus
the boiling is a near surface affect only.

First see:
http://www.umsl.edu/~orglab/document...ation/dist.htm
http://www.chem.uidaho.edu/~honors/vaptemp.html
http://www.saharahenderson.com/types/tsld020.htm

If the water is very cold in the first place then it will have a very low
vapor pressure and will evaporate very slowly, it is also important to
remember that vaporization also will cool the water further lowering it's
vapor pressure further.

The weight of the water further down in a body of water prevents the all but
the first few meters from boiling, as the top level boils and cools it is
also possible for ice to form and cap over water and cut off most of the
water loss.

Earl Colby Pottinger

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