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Betsy3491
2004-Mar-02, 09:29 PM
Sounds to me like they're pretty sure the water was there long enough that microscopic life is a real possibility. One of the NASA scientists used the word "habitable." I'm really thrilled by this! I'm the author of an award-winning children's book called LOOKING FOR LIFE IN THE UNIVERSE--if anyone is interested.

Drakheim
2004-Mar-02, 09:31 PM
And hopefully still is :wink:

Grand_Lunar
2004-Mar-02, 09:43 PM
I wonder though what changed it all? Too small? Too cold? Too far away from the sun? An ice age it never recovered from? Seems what we learn on Mars can most definately be used on Earth; such as making sure the same thing doesn't happen here. Of course, we don't want to be another Venus either!

Dancar
2004-Mar-02, 10:16 PM
I was surpised by the reluctance of the scientist to conclude that standing liquid water existed on the surface. I thought that was a given with the apparent riverbeds seen from orbit.

Are there alternative explanations for the apparent river beds and other erosional features that appear to be from running water? Or was he only referring to the Meridian Plain?

Dancar

Grand_Lunar
2004-Mar-02, 11:08 PM
Good question. I've wondered that. My guess has been that there's more to the mission that just evidence for water. The dried up river beds could easly be made by a big flood. The question then I guess is whether or not Mars may have been watery like Earth; lakes, oceans, ect. I belive that's what's been found by Oppurtunity. Indications of a large body of standing water. So Mars was once warmer and more hospitible. The real question is, what happened?

JohnOwens
2004-Mar-02, 11:56 PM
I wonder though what changed it all? Too small? Too cold? Too far away from the sun? An ice age it never recovered from? Seems what we learn on Mars can most definately be used on Earth; such as making sure the same thing doesn't happen here. Of course, we don't want to be another Venus either!

Little-known fact: A.C. Clarke's monoliths were made of hydrogen. Hence, the way they gobbled up Jupiter in 2010. Then, at some point in Mars' past, the water (which happens to be made of hydrogen and oxygen, of course) went away. At some time in Earth's past, a monolith was produced and sent here, and then to the Moon (or were they the same one?). Where do you suppose they got the materials from? :wink:

You do the math.

Alternate hypothesis: Anyone else read Niven's Rainbow Mars yet? What's the score look like for that one so far?

mike alexander
2004-Mar-03, 12:37 AM
Read it.

The Hangtree is Coming!

Grand_Lunar
2004-Mar-03, 12:57 AM
The monoliths (monoli?) were made of hydrogen? Guess I missed that part in 3001.
Far as I know, the Tycho monolith and the Terran monolith are two different entities. That part I DID read in 3001.
But this conversation belongs in the sci-fi sector, wherever that might be.
Meanwhile, our rovers dig on!

JohnOwens
2004-Mar-03, 01:06 AM
The monoliths (monoli?) were made of hydrogen? Guess I missed that part in 3001.
Far as I know, the Tycho monolith and the Terran monolith are two different entities. That part I DID read in 3001.
But this conversation belongs in the sci-fi sector, wherever that might be.
Meanwhile, our rovers dig on!

It's never stated in the books, see, because, umm... because Arthur Clarke is part of the conspiracy! Yeah, that's it.

Seriously, I only read 3001 once so far, too long ago, and I was afraid it might have contradicted some of what I was spinning up there, but I decided to go with it anyway. And the 2010 event does support the hypothesis that they can be made from hydrogen, although I tended to assume that they had some super-duper transubstantiation/transmogrification technology that let them make them out of just about any material.

Swift
2004-Mar-03, 03:08 PM
I was surpised by the reluctance of the scientist to conclude that standing liquid water existed on the surface. I thought that was a given with the apparent riverbeds seen from orbit.

Are there alternative explanations for the apparent river beds and other erosional features that appear to be from running water? Or was he only referring to the Meridian Plain?

Dancar
I believe that one possible explanation is that the apparent river beds were made from running water, but that does not mean that the water was around for a long time. For example, imagine a mass of water locked up as ice or in rock formations. There is an event (volcano, meteor) that heats up the water. The water flows for a brief period of time, cuts the channel, then evaporates away. You get that in deserts on Earth.

There are differences between saying that liquid water existed for brief periods of time on Mars or flowed through ground water, and saying there was an ocean or lake. I suspect NASA won't make those claims until there is evidence to support them.

eburacum45
2004-Mar-03, 03:13 PM
Here is a very good PDF about Mars' early atmosphere, and the mechanisms by which it was lost;

http://www.atmos.washington.edu/~davidc/papers_mine/Catling-2004-MarsAtmos.pdf


it seems that liquid water may have been present ocasionally, even after the bulk of the atmosphere was lost; so it is all very complex...

Espritch
2004-Mar-04, 01:05 AM
I believe that one possible explanation is that the apparent river beds were made from running water, but that does not mean that the water was around for a long time. For example, imagine a mass of water locked up as ice or in rock formations. There is an event (volcano, meteor) that heats up the water. The water flows for a brief period of time, cuts the channel, then evaporates away. You get that in deserts on Earth.

Now if they found river beds that showed clear signs of meanders, that would be a whole other story. Meanders are created by slow moving rivers over long periods of time. So, has anyone seen anything on Mars that looks like a meander?

nebularain
2004-Mar-04, 01:10 AM
Guess I missed that part in 3001.

That's OK - I missed 3001 entirely! :o

When did he jump a century?
#-o

JohnOwens
2004-Mar-04, 07:09 AM
Guess I missed that part in 3001.

That's OK - I missed 3001 entirely! :o

When did he jump a century?
#-o

Millennium

Written in the mid '90s, I'd say, from what I remember of where I lived when I read it. Or, I'm sure you could check on Amazon and it would tell you.

ToSeek
2004-Mar-04, 02:48 PM
Now if they found river beds that showed clear signs of meanders, that would be a whole other story. Meanders are created by slow moving rivers over long periods of time. So, has anyone seen anything on Mars that looks like a meander?

How about this (http://www.cosmographica.com/gallery/portfolio/portfolio001/pages/042-%20MarsVerticalView.htm) or this (http://astro.nmsu.edu/~aklypin/ast110/WebSite/canyon1.jpg)?

Espritch
2004-Mar-05, 03:12 AM
Yes. Those do look rather meanderish. Thanks.

I wonder how long it's been since water flowed in them?

PeteB
2004-Mar-05, 04:31 AM
Here's a recent MGS image of a deltaic deposit with meanders:
http://www.msss.com/mars_images/moc/2003/11/13/

Anthrage
2004-Mar-05, 10:12 AM
3001 was completed in late 96, and published/printed in '97.

The meanders are very interesting not only for what they are, but what they reveal - in that in some cases, we see evidence of what had to be a long 'wet' period, with overlaps and crossings plainly visible...

We know mars was wet. We know it was wet for a considerable amount of time. What we need to establish, is just when that period was, and if there was sufficient time for life to develop during it. I feel sorry sometimes for some of the scientists out there who must be going absolutely mad looking at some of these images and just knowing that if they could be down there, on the ground, with even a modest lab, they could be answering some incredible important and fundamental questions. #-o

eburacum45
2004-Mar-05, 11:31 AM
I wonder if I might post this essay about water loss from Mars on this board, (mostly using this paper (http://www.atmos.washington.edu/~davidc/papers_mine/Catling-2004-MarsAtmos.pdf) as a source)- please put me right if I have got it wrong anywhere...

Water loss from Mars

It certainly seems likely that Mars had a lot of water at some point; if I may, I would like to give a little prehistory of Mars, given the evidence available before the Spirit and Opportunity landings. Any or all of this essay could be shown to be wide of the truth depending on the results of the current investigations, so don’t take it too seriously…
Mars formed from the material in the solar nebula and reached its present size by 4.6 billion years ago (gigayears ago; Gya) ; the amount of water on the early planet is unknown, but there are two main options; either Mars had a similar amount of primeval water to the Earth, or it may have had somewhat less; much of the early waterin this region had become bound into bodies known as planetary embryos, and if Mars encountered fewer of these objects it may have started out significantly drier.

The evidence from Spirit and Opportunity seems to indicate that water was relatively plentiful in the early period, so we now have to consider where this water has gone.
The first age of Martian history, from 4.6 Gya to 3.8 Gya has been labelled the Noachian period; the atmosphere, mostly CO2 and nitrogen was perhaps six times as thick as that on Earth today. Liquid water was possible in these conditions, despite the fact that the early Sun was as much as 30% less bright. So there may have been seas, and there are many water-associated features in Noachian period terrain. The core of Mars was still hot enough for a magnetic field at that time, so the effects of solar wind and hard UV on the atmosphere were lessened.

However there were many impacts during the Noachian; 200+ craters larger than 5km per million km^2; this was one reason for atmosphere (and water) loss- impact erosion.
Because of Mars’ lower gravity, the effect of large impacts was to expel volatiles into outer space; the fraction that exceeded escape velocity never returned. (This will have to be accounted for in any terraforming project which involves volatiles crash-landing on Mars- if the impacts are too energetic, the volatiles will escape to a greater or lesser extent).

A second mechanism for Martian atmosphere loss was hydrodynamic escape; the early planet still contained a lot of the primeval hydrogen from the solar nebula; this will have been expelled by volcanic outgassing as it rose through the semimolten interior; a lot of hydrogen in the atmosphere would make it less dense, so the whole atmosphere would swell, and gases of all kinds would be driven off at the top of the swollen atmosphere; another way of looking at it is that hydrogen quickly boils off, but drags some of the other atmospheric components with it.

By the end of the Noachian, when impacts became less frequent and the magnetic field disappeared as the core cooled down, the atmosphere was down from 6 atmospheres to 0.06 atmospheres; liquid water would no longer have been possible.
Now the magnetic field had gone, the solar wind could rip away at the top of the atmosphere; this very variable effect is sometimes known as sputtering.
Additionally the hard UV from the early Sun (although the sun was less bright, it was smaller and hotter- so more UV) could strip water in the atmosphere into oxygen and hydrogen by photolysis; the hydrogen would escape, dragging other gases with it; the oxygen would combine readily with the rocks of Mars, forming sulphates, haematite, perhaps carbonates.

By these processes, impact erosion, hydrodynamic loss, sputtering and photolysis, the atmosphere of Mars eventually reached its current level of 0.006 x Earth’s. However the water loss will have been drastically reduced once the atmosphere was no longer thick enough to produce a greenhouse effect; when it got too cold the water will have turned to ice, which is much less volatile. In fact is is quite possible that much of Mars’ water is still there; as ice it would be incorporated into the rock as part of the solid matrix, or far underground as liquid water; the surface is freeze dried, and evidently very salty, though chorine seems to be scarce- the salts are mostly sulphates… but the loss of water to surface sinks seems to have been a major mechanism of water loss from the surface. One estimate says that half of the water left at the end of the Noachian is still there.

In other words, much of the water may still be there, buried deeply. During the later Martian periods, the Hesperian and Amazonian, it seems that combinations of orbital cycles and axial tilt have periodically brought liquid water to the surface; it may be possible to achieve this by artificial means, particularly using positive feedback mechanisms, and bring Martian water to the surface again.

nebularain
2004-Mar-05, 05:20 PM
A question that has been in the back of my mind, which I am not sure if it has been addressed before or not, is why haven't the meanders been covered over by the dust storms and wind and sand erosion? Does it have something to do with where we see them (ie. steep hills or whatever)? Or what?