Surface Water Possible Under Mars-Like Conditions

"Ron Baalke" wrote
in message ...

FAYETTEVILLE, Ark. -- A team of researchers from
the University of Arkansas has measured water evaporation
rates under Mars-like conditions, and their findings favor
the presence of surface water on the planet. Water on the
planet's surface makes the existence of past or present life
on Mars a little more likely, according to the group.

[snip]

The researchers have brought on-line a large planetary
environmental chamber in which temperature, pressure,
atmosphere, sunlight and soil conditions can be reproduced.

I take it that gravity on Mars being a mere 38% of that in the
experiment has little bearing on the evaporation rate?

-Jens

"Ron Baalke" wrote
in message ...

FAYETTEVILLE, Ark. -- A team of researchers from
the University of Arkansas has measured water evaporation
rates under Mars-like conditions, and their findings favor
the presence of surface water on the planet. Water on the
planet's surface makes the existence of past or present life
on Mars a little more likely, according to the group.

[snip]

The researchers have brought on-line a large planetary
environmental chamber in which temperature, pressure,
atmosphere, sunlight and soil conditions can be reproduced.

I take it that gravity on Mars being a mere 38% of that in the
experiment has little bearing on the evaporation rate?

-Jens

In article ,
Jens Kieffer-Olsen wrote:
The researchers have brought on-line a large planetary
environmental chamber in which temperature, pressure,
atmosphere, sunlight and soil conditions can be reproduced.

I take it that gravity on Mars being a mere 38% of that in the
experiment has little bearing on the evaporation rate?

Very little. And as a practical matter, it's virtually impossible to
reproduce that anyway...
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

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

Doug Haxton wrote:
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


Not necessarily...especially if the water is cold. At 70 deg F, you can
lower pressure slowly down to about 10 Torr before vigorous boiling
occurs. If you keep lowering below 4.5 Torr, suddenly you'll get a
rapid phase transition to ice because you're at the Triple Point of
water. So, if water is colder, you should be able to lower pressure
even further before you get boiling.

stmx3 wrote in message ...
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


Not necessarily...especially if the water is cold. At 70 deg F, you can
lower pressure slowly down to about 10 Torr before vigorous boiling
occurs. If you keep lowering below 4.5 Torr, suddenly you'll get a
rapid phase transition to ice because you're at the Triple Point of
water. So, if water is colder, you should be able to lower pressure
even further before you get boiling.

How much is 10 Torr in terms inches of mercury?

Doug

In article ,
Jens Kieffer-Olsen wrote:
I take it that gravity on Mars being a mere 38% of that in the
experiment has little bearing on the evaporation rate?
Very little. And as a practical matter, it's virtually impossible to
reproduce that anyway...

Airplanes in free fall are used to produce brief periods of zero
gravity, so why not let a slight trust emulate .38G?

No need for a slight thrust; emulating lunar or Martian gravity is just
a matter of flying a slightly shallower parabola. It's been done
occasionally. But the available time at reduced G is too short for
some things; I think it would be quite a trick to get measurements of
things like this in the time available.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

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

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

(Henry Spencer) writes:

In article ,
Jens Kieffer-Olsen wrote:
I take it that gravity on Mars being a mere 38% of that in the
experiment has little bearing on the evaporation rate?
Very little. And as a practical matter, it's virtually impossible to
reproduce that anyway...

Airplanes in free fall are used to produce brief periods of zero
gravity, so why not let a slight trust emulate .38G?

No need for a slight thrust; emulating lunar or Martian gravity is just
a matter of flying a slightly shallower parabola. It's been done
occasionally. But the available time at reduced G is too short for
some things; I think it would be quite a trick to get measurements of
things like this in the time available.

Moreover, there is ABSOLUTELY NO REASON to believe reduced gravity should
have any effect on the evaporation rate of water, any more than it would
affect the boiling point or freezing point of water.

Gravity is quite simply UTTERLY IRRELEVANT to any process governed by
microscale physics. Gravitation is only important when bodies are large
and/or all other accelerations are small --- neither of which are true
of individual molecules of water.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Doug Haxton) writes:

How much is 10 Torr in terms inches of mercury?

1 Torr == 1 mm Hg --- as you could have easily found using Google,
or even a good dictionary.

I leave the exercise of converting millimetres into inches to you...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'