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#1 2004-04-23 11:24:35

Bill White
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Registered: 2001-09-09
Posts: 2,114

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]See this article.[/color:post_uid0]

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#2 2004-04-23 14:09:10

atomoid
Member
From: Santa Cruz, CA
Registered: 2004-02-13
Posts: 252

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]Interesting article, but im still under the impression that all the inner planets pummelled by cometary bodies (where Earth got its water) early on in the history of the solar system? doesnt this imply that at the outset there was lots of water in similar amounts on all the planets including Mars?

So that amount of water had to play some major role on Mars at least until it was slowly secreted away by solar radiation (no appreciable magnetic field) splitting into H and O, and the lesser gravity accelerated the loss of water and atmosphere to space. Mercury is just too hot and small to hold onto any water (except in permanently shadowed pole craters). and Venus, too hot for liquid, but is there a lot of water vapor in the atmosphere? has it been chemicsally combined into other compounds? im not sure what the scario was there... anyone?[/color:post_uid0]


"I think it would be a good idea". - Mahatma Gandhi, when asked what he thought of Western civilization.

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#3 2004-04-23 19:42:59

Shaun Barrett
Member
From: Cairns, Queensland, Australia
Registered: 2001-12-28
Posts: 2,843

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid4]Yes, it is an interesting article. I'm not entirely clear on one or two points which were made and I think a few diagrams would have been helpful in this regard, but it is another new hypothesis and should be treated with respect until found wanting.
    While I think it's quite possible that the Wet Mars people (me included) are inclined to wax romantic about an ancient Mars with rivers and oceans, perhaps to the point of seeing what they want to see and disregarding the rest, I think it may be possible to do the opposite, too. I believe Peter Ravenscroft "doth protest too much" about water on Mars!
    He maintains that Wet Mars proponents see water everywhere, without justification. But I perceive in his work an almost evangelical zeal to exorcise water all together from the martian environment! My feeling is that he has built a house of cards, a bone-dry house, which tries to ignore evidence for water with just as much enthusiasm as Wet Marsers demonstrate in support of it.

    It seems to me that a compromise is in order here: I'm prepared to admit that aeolian erosion has played a significant role in the sculpting of the martian surface, as long as Peter Ravenscroft is prepared to entertain the increasingly mainstream (... ouch! ..) notion that water erosion has also been a major player.
    I could go on for hours about the extremely compelling evidence for water erosion on Mars, and Dr. Squyres' team at JPL would be bemused to find their definite identification of water-formed sediment at the Opportunity landing site is all just a mistake! And, when you combine this with the satellite data showing large quantities of water ice in the regolith and at the poles, it's difficult to understand Peter's dismissal of water in his brief geological history of Mars. To hear him tell it, there's hardly any water and there never has been! I find this to be a totally unsustainable viewpoint and the whole hypothesis smacks of dreaming up an exotic idea and then carefully constructing an unlikely argument to support it, ignoring any evidence along the way which undermines it.

    Most of us are prepared to include water and wind erosion in our picture of martian history - an eminently reasonable position in my opinion - but Peter Ravenscroft seems to be very pointedly overlooking the water for his own purposes.
    Could it be that both Ravenscroft and Hoffman have some reason to portray Mars as much more hostile than it actually is?
    Nahhh!! There goes my paranoia again.    :laugh:[/color:post_uid4]


The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

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#4 2004-05-18 12:43:26

REB
Member
From: Houston, Texas
Registered: 2004-04-07
Posts: 555
Website

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]More evidence of flowing water on Mars;

http://www.msss.com/moc_gallery/e01_e06 … 01423.html

If you go to the full size picture and go almost halfway down, you’ll see what looks like braided stream beds. Braded streams are usually caused by meandering water.[/color:post_uid0]


"Run for it? Running's not a plan! Running's what you do, once a plan fails!"  -Earl Bassett

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#5 2004-05-18 12:46:55

REB
Member
From: Houston, Texas
Registered: 2004-04-07
Posts: 555
Website

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]This MOC image shows some nice gullies;

http://www.msss.com/moc_gal....474.jpg

A couple of them have some nice meanders.

Usually, meanders means the liquid flowed for some time.[/color:post_uid0]


"Run for it? Running's not a plan! Running's what you do, once a plan fails!"  -Earl Bassett

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#6 2004-05-18 21:50:31

atomoid
Member
From: Santa Cruz, CA
Registered: 2004-02-13
Posts: 252

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000080:post_uid0]

This MOC image shows some nice gullies;

http://www.msss.com/moc_gal....474.jpg

A couple of them have some nice meanders.

Usually, meanders means the liquid flowed for some time.[/quote:post_uid0]
Thanks, truly some excellent shots of gullies!
first image you refer to looks like theres a lot of dust accumulation. i wonder if dust accumulates and avalanches downslope and if this type of erosion might create similar features as that shown in the image.

the second image of gullies however, is much clearer to see whats going on and begs a much different explanation. I'll bet ('hope' at least) that these gullies are actively forming even today. Heres a tentative albeit incomplete hypothesis (has anyone shot down this idea yet?):

Notice that theres a lot of frost accumulation in this area that is now almost gone this season.
1) The seasonal cycle deposits frost in varying concentrations depending upon the conditions in close proximity to the water vapor laden air.
2) The frost accumulates relatively thinly on the plains in contrast to the outcrops and overhangs which are colder since theyre likely to be out of sunlight more often. These colder areas, being a perfect heat sink, collect any water vapor from the air that passes over them since any water would tend to readily condense there.
3) The frost accumulates into realtively thick ice cakes over the season.
4) When the seasons comearound, the ice cakes might melt and drip out suddenly as warm air makes its way over them.
5) excruciatingly slow and gradual gully formation occurs over tens of thousands of years, as a repeated series of brief and relatively unproductive erosional sessions consisting of small amounts of slurry carving the gullies on their way downslope.[/color:post_uid0]


"I think it would be a good idea". - Mahatma Gandhi, when asked what he thought of Western civilization.

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#7 2004-05-19 06:00:39

REB
Member
From: Houston, Texas
Registered: 2004-04-07
Posts: 555
Website

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]That is a good theory.

Initially I thought the water making the gullies was coming from an aquifer near the top layers. If the source of the water was really under ground, wouldn’t is seep a little deeper before exiting. Wouldn’t it be seeping out near the bottom of these craters?

Perhaps the water is coming from the air. It is condensing as ice on the sides of these craters as ice before turning liquid. I believe that water could remain liquid for some time under Mars conditions if it had an ice layer over it.

I have seen some gullies on dunes (I’ll try to find a picture) that could not have had an underground water source.

I have noticed that most gullies on Mars are in the southern hemisphere.[/color:post_uid0]


"Run for it? Running's not a plan! Running's what you do, once a plan fails!"  -Earl Bassett

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#8 2004-05-19 09:34:00

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]For people that don't like to download the big files, I've made a cutout of the meandering...

[img:post_uid0]http://ibelgique.ifrance.com/RXKE/pics/ … cutout.jpg[/img:post_uid0]

EDIT: removed contrast/brightness boosted pic for unaltered  cutout from original.[/color:post_uid0]


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#9 2004-05-19 09:41:59

REB
Member
From: Houston, Texas
Registered: 2004-04-07
Posts: 555
Website

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]And I apologize about putting the link for the large picture. I meant to put the MOC page that link came from like I did with the previous picture. When Dealing with MOC pictures, I don't like to post the full size image.[/color:post_uid0]


"Run for it? Running's not a plan! Running's what you do, once a plan fails!"  -Earl Bassett

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#10 2004-05-19 11:17:00

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]Naah, no need to apologize! 'twas just me, playing around a bit on different pics, downloaded in the days before and then i thought this cutout could come in handy, for i myself didn't find it rightaway in the big (beautiful!) pic initially... big_smile[/color:post_uid0]


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#11 2004-05-19 11:43:33

REB
Member
From: Houston, Texas
Registered: 2004-04-07
Posts: 555
Website

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]Here is some good information on meanders;

http://www.oxbowriver.com/Web_Pag....al.html

Those meandering channels in that MOC picture look recent.[/color:post_uid0]


"Run for it? Running's not a plan! Running's what you do, once a plan fails!"  -Earl Bassett

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#12 2004-05-19 12:40:20

rgcarnes
Member
From: In the country near Rolla Miss
Registered: 2002-02-04
Posts: 111

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000000:post_uid0]If you wish to see some of the mathematics describing river meanders, see the March 1966 Scientific American article featured on the cover.[/color:post_uid0]


Rex G. Carnes

If the Meek Inherit the Earth, Where Do All the Bold Go?

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#13 2004-05-19 23:27:29

atomoid
Member
From: Santa Cruz, CA
Registered: 2004-02-13
Posts: 252

Re: .Wet Mars or Dry Mars? - Another spacedaily spoilsport

[color=#000F22:post_uid0][img:post_uid0]http://ibelgique.ifrance.com/RXKE/pics/ … cutout.jpg[/img:post_uid0]
on second thought, frost accumulation and subsequent warm-period meltouts i think would tend not to create such long and consistent channels as the ones we see here (in my off-hand non-hydrologist intuitive judgement at least).

The length and even width of these channels seem to require a *sustained* outflow, even if its sporadic. The idea of warm air dripping and melting the ice pack i think would only create small runs of channels that would concentrate at the alcove of the channel and not go very far before the water gets soaked up or evaporated or frozen. we just wouldnt see the long channels. There must be some other characteristic at work here to explain this mystery...

It cant be an aquifer source since the water source is in the crater rim and is above the surrounding terrain. there can be no water table this high in such a case.

...maybe the water freezes as it goes downhill and is insulated by a blanket of ice so it keeps running, but the probelm is then why would it melt in the first place if its cold enough to freeze it?

...maybe the water drips out and erodes some debris that is responsible for carving the channels as it runs down the slope. but are solid debris capable of forming such features? i thought no, anyone?

...maybe the Christensen hypotheis had a run here, in that there was once an insulating blanket of snow/ice over these channels that acted as a greenhouse, the sunlight being absorbed as deep as 15 centimeters and melting the subsurface snow and perhaps once it melts the water picks up some salts from the soil which melts still more ice, accelerating the process. this would allow the melt to run long and consistently enough to form these channels underneath the protective blanket of ice.

in this case, i guess the large part of these channels wouldnt be forming today (althought there might be some erosion due to frost build-up and melt), but they would still be young geologically speaking.[/color:post_uid0]


"I think it would be a good idea". - Mahatma Gandhi, when asked what he thought of Western civilization.

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