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RGClark
2004-Dec-14, 04:07 PM
From the Mars rover press release:

December 13, 2004
Mars Rovers Spot Water-Clue Mineral, Frost, Clouds
"A portion of Mars' water vapor is moving from the north pole toward the south pole during the current northern-summer and southern-winter period. The transient increase in atmospheric water at Meridiani, just south of the equator, plus low temperatures near the surface, contribute to appearance of the clouds and frost, Wolff said. Frost shows up some mornings on the rover itself. The possibility that it has a clumping effect on the accumulated dust on solar panels is under consideration as a factor in unexpected boosts of electric output from the panels."
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20041213a.html

Rover scientists had speculated that some of this frost may melt to liquid to contribute to the clumping. Note that actual SURFACE temperatures can exceed 0 C when the air temperature is below freezing, when the surface is exposed to direct sunlight (it's southern winter at the landing sites now.) This would be especially true of a dark surface like the solar panels specifically designed to absorb sunlight.
What is the expected temperatures of the solar panels during the hottest portion of the day? Do the cameras actually observe the frost on solar panels? If so then we may actually be able to observe the transition to liquid during late morning to early afternoon.
Note that the accumulation of this frost confirms visually what has been found by the Mars Odyssey HEND hydrogen mapper that water accumulates on Mars in near equatorial locations during northern and southern Summer:

Further evidence for current liquid water near the equator on Mars.
Posted by Robert Clark on 11/25/2004 12:39:16 AM
http://habitablezone.com/space/messages/358773.html

This visual evidence from the rovers further supports the suggestion by the authors of the HEND report that this increase is due to atmospheric deposition. Of the various explanations offered by the authors, it supports the suggestion the water is in free form, not bound in sulfate or other evaporite:

47 - EVIDENCE OF THE SEASONAL REDISTRIBUTION OF WATER IN THE SURFICIAL MARTIAN REGOLITH BASED ON ANALYSIS OF THE HEND MAPPING DATA.
R.O. Kuzmin, E.V. Zabalueva, I.G. Mitrofanov, M.L.Litvak, A.V. Parshukov, V.Yu.Grin'kov, W. Boynton, R.S. Saunders.
http://www.geokhi.ru/~planetology/theses/47_kuzmin_et_al.pdf

The authors suggest frost or ice. My opinion is that during warm *surface* temperatures this frost can melt to liquid, particularly for low albedo (dark), low thermal inertia (easy to heat up) materials, such as the solar panels.


Bob Clark

RGClark
2004-Dec-14, 04:18 PM
I found this link that gives the current Mars temperatures. But it doesn't give a legend to interpret the color coded maps?
Anyone know what is the high temperature in the maps?

http://tes.asu.edu/dust/



Bob Clark

frogesque
2004-Dec-14, 05:40 PM
Same site, try this page (http://tes.asu.edu/daily.html) Current max temp is about -5C from the top plot dated Tues 14th Dec 04

Edit: Best guess from the bottom surface temp colour map supports that figure (I got -7C by estimating colour against the chart which runs from -125C to +15C - Not very accurate using a rule on a 15" monitor!)

2nd. edit:
Pure liquid water from frost? No! I think the frost thickness would be insufficient for an isolating layer of ice to develop a local contact 'greenhouse' and also prevent evaporation/sublimation. It's a close call though but there is very little room to play with at 7-10mb. Too cold = ice, too warm = boiling.

Liquid strong saline solution films on the surface for very short periods? Possibly!

My view is that if liquid water is there in any real quantity it will be under ground where the overburden of the regolith can maintain a reasonable pressure (>1000mb) and some vestige of vulcanisim maintaining a subterranian temperature above 0C

However, much better brains than I have are pondering all these issues and I do find the prospect of finding any surface pools of liquid exciting regardless of how unlikely that is, based on current knowedge.

RGClark
2004-Dec-15, 02:15 AM
...
Pure liquid water from frost? No! I think the frost thickness would be insufficient for an isolating layer of ice to develop a local contact 'greenhouse' and also prevent evaporation/sublimation. It's a close call though but there is very little room to play with at 7-10mb. Too cold = ice, too warm = boiling.

Liquid strong saline solution films on the surface for very short periods? Possibly!

My view is that if liquid water is there in any real quantity it will be under ground where the overburden of the regolith can maintain a reasonable pressure (>1000mb) and some vestige of vulcanisim maintaining a subterranian temperature above 0C

However, much better brains than I have are pondering all these issues and I do find the prospect of finding any surface pools of liquid exciting regardless of how unlikely that is, based on current knowedge.

A microbe would only require a micron thick liquid film to survive. We could easily imagine sunlight penetrating the frost and melting it directly next to the surface before the top surface frost sublimates.


Bob Clark

frogesque
2004-Dec-15, 03:51 AM
RGClark wrote:


....A microbe would only require a micron thick liquid film to survive. We could easily imagine sunlight penetrating the frost and melting it directly next to the surface before the top surface frost sublimates.


It wouln't even need a film, interstitial fluid within the ice crystal could do it, especially if it were an eutectic saline solution. Microbes would also have to survive long winter periods below -100C. Could they utilise CO2 as an antifreeze - Haven't a Scooby :lol:

At the moment I'm in enough hot water (if you'll excuse the pun) about conditions for water remaining on the surface of Mars (something I do know a little about) without speculating about an unknown like Martian biology (something I know nothing about) so I'm going to duck that one if I may 8)

RGClark
2004-Dec-25, 08:53 PM
Imaging at the Opportunity rover landing site in Meridiani Planum confirms observations using the HEND instrument on Mars Odyssey that water/ice is deposited near the equator seasonally on Mars:

Space Sciences
Whoa! Frost on the solar panels?
Posted by Robert Clark on 12/14/2004 7:32:38 AM
In Reply to: Sabkha or playa, take your pick... posted by Nick Hoffman on 12/13/2004 6:23:08 PM
http://habitablezone.com/space/messages/360805.html

However, the HEND instrument shows the greatest amount is deposited during southern Summer:

47 - EVIDENCE OF THE SEASONAL REDISTRIBUTION OF WATER IN THE SURFICIAL MARTIAN REGOLITH BASED ON ANALYSIS OF THE HEND MAPPING DATA.
R.O. Kuzmin, E.V. Zabalueva, I.G. Mitrofanov, M.L.Litvak, A.V. Parshukov,
V.Yu.Grin'kov, W. Boynton, R.S. Saunders.
"As it well seen from fig.1b,c,d, two distinctive “hollows” of neutrons flux reduction have been appeared in the northern hemisphere during northern summer at Ls=130°-170° and in first half of northern winter at Ls=270°-330°, being extended from high to low latitudes. At that, later “hollow” (Ls=270°-330°) is characterized by much stronger reduction of the neutrons flux and it traces from northern polar region up to low latitudes in the southern hemisphere. The first “hollow” is related with periods of the northern middle summer, while the second one – with of the southern middle summer. In both case the residual polar caps serve as main source of the water in the Martian atmosphere."
p. 2
http://www.geokhi.ru/~planetology/theses/47_kuzmin_et_al.pdf

Opportunity landed just barely after this time in southern Summer at about LS 340° (LS stands for solar longitude and indicates Mars position in its orbit.)
However, it is notable that Spirit did land near the end of the time period of Ls=270°-330°. Spirit is closer to the southern pole and this may explain how could experience deposition during this period while apparently not during the current northern Summer. Then the controversial indications of mud at the Spirit landing site early in the mission may indeed have been indications of this summer-time water deposition.
Opportunity has observed clouds during the current water deposition period and since the amount of atmospherically deposited water is greater during southern Summer, we would expect the cloud density to be even greater then. Indeed it could be of sufficient density to allow precipitation which could reach the ground as rain.
The next Ls=270°-330° period begins in August, 2005.

Come on Opportunity!


Bob Clark

frogesque
2004-Dec-25, 11:46 PM
RGClark wrote:


The next Ls=270°-330° period begins in August, 2005.

Come on Opportunity!


I'll certainly agree to that sentiment!

For the rest; I would love to see it rain on Mars (why should we get all the bad weather :lol: ) but I'm still not convinced. I think any cloud cover would block too much sunlight and the lower atmosphere and ground temperatures would be below freezing. Snow might just be a possible though if there is sufficient atmospheric pressure build up due to increase in water vapour during summer. We'll have to wait and see.

Have a great festive season RG and all Mars watchers everywhere.

RGClark
2004-Dec-28, 04:48 PM
Imaging at the Opportunity rover landing site in Meridiani Planum confirms observations using the HEND instrument on Mars Observer that water/ice is deposited near the equator seasonally on Mars:

Space Sciences
Whoa! Frost on the solar panels?
Posted by Robert Clark on 12/14/2004 7:32:38 AM
In Reply to: Sabkha or playa, take your pick... posted by Nick Hoffman on 12/13/2004 6:23:08 PM
http://habitablezone.com/space/messages/360805.html

However, the HEND instrument shows the greatest amount is deposited during southern Summer:

47 - EVIDENCE OF THE SEASONAL REDISTRIBUTION OF WATER IN THE SURFICIAL MARTIAN REGOLITH BASED ON ANALYSIS OF THE HEND MAPPING DATA.
R.O. Kuzmin, E.V. Zabalueva, I.G. Mitrofanov, M.L.Litvak, A.V. Parshukov,
V.Yu.Grin'kov, W. Boynton, R.S. Saunders.
"As it well seen from fig.1b,c,d, two distinctive “hollows” of neutrons flux reduction have been appeared in the northern hemisphere during northern summer at Ls=130°-170° and in first half of northern winter at Ls=270°-330°, being extended from high to low latitudes. At that, later “hollow” (Ls=270°-330°) is characterized by much stronger reduction of the neutrons flux and it traces from northern polar region up to low latitudes in the southern hemisphere. The first “hollow” is related with periods of the northern middle summer, while the second one – with of the southern middle summer. In both case the residual polar caps serve as main source of the water in the Martian atmosphere."
p. 2
http://www.geokhi.ru/~planetology/theses/47_kuzmin_et_al.pdf

Opportunity landed just barely after this time in southern Summer at about LS 340° (LS stands for solar longitude and indicates Mars position in its orbit.)
However, it is notable that Spirit did land near the end of the time period of Ls=270°-330°. Spirit is closer to the southern pole and this may explain how could experience deposition during this period while apparently not during the current northern Summer. Then the controversial indications of mud at the Spirit landing site early in the mission may indeed have been indications of this summer-time water deposition.
Opportunity has observed clouds during the current water deposition period and since the amount of atmospherically deposited water is greater during southern Summer, we would expect the cloud density to be even greater then. Indeed it could be of sufficient density to allow precipitation which could reach the ground as rain.
The next Ls=270°-330° period begins in August, 2005.

Come on Opportunity!


Bob Clark


Note also that evaporates (sulfate or carbonate) seen on *top* of rocks in Gusev also supports the idea of atmospheric deposition of liquid water in Gusev:

========================================
Newsgroups: sci.astro,alt.sci.planetary,sci.geo.geology,sci.ge o.mineralogy
From: rgregorycl...@yahoo.com (Robert Clark) Date: 2 Jul 2004 04:57:20 -0700
Local: Fri, Jul 2 2004 4:57 am
Subject: Evidence for atmospheric liquid water in Gusev?


In the badastronomy.com forum Daniel Crotty presents an image (below)
showing white colored material on *top* of rocks. This would argue
against the interpretation suggested by Steve Squyres that the
sulfates seen in Gusev might stem from water percolating up from the
subsurface. Instead it would suggest sulfates formed from liquid water
precipitation(rain) or liquid water droplets in a humid atmosphere.
I wondered whether white material on the rocks could be due to the
dust kicked up by a RATTing but Crotty gives other images with no
ratting nearby that also shows white rocks:


Dusty, bright material around Spirit, Sol 165
http://badastronomy.com/phpBB/viewtopic.php?t=14573&sid=7f6b82d247999...


Bob Clark


Uncalibrated color image by Daniel Crotty.
http://www.lyle.org/~markoff/collections/spiritsol165_L257.jpg


Bob Clark
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