Huge water ice reservoirs found on Mars!

Josh Cryer · 2003-06-12 07:42:26

Hmm, I thought that the concensus was that Ganges Chasma was a tectonic rift (if that's the right term for it- maybe fault is what I'm looking for?), not carved by water? If this is the case, why can't it be possible that the water had frozen into the regolith before the rift occured?

I wasn't under the impression that there was liquid surface water recently (in the presumbable northern ocean), but I'm convinced it did happen ?some long time ago.?

dickbill · 2003-06-12 09:05:08

Hmm, I thought that the concensus was that Ganges Chasma was a tectonic rift (if that's the right term for it- maybe fault is what I'm looking for?), not carved by water? If this is the case, why can't it be possible that the water had frozen into the regolith before the rift occured?
I wasn't under the impression that there was liquid surface water recently (in the presumbable northern ocean), but I'm convinced it did happen ?some long time ago.?

That might be that, a tectonic activity causing a fault, after the floods took place. I've heard the same for Valles Marineris, it's a tectonic fault rather than a canyon carved by flood. It has to be much much later after the flood, because Shaun argument still stands, if you have a massive flood 2 km above your head it's difficult to imagine how the flood and the ice later, doesn't get down and destroy all the olivine.
By the way, in the abstract included in my last post, the author say that Olivine is also attacked in presence of ice (H2O frost) at minus 22 degre C. I also think that it is a reasonable to presume that water vapor was more abundant in that early martian atmosphere because of these floods and that would be enough also, to degrade the olivine.

But if Ganges Chasma was formed much later after the flood, and the olivines never saw the water, the ice and the steam, then the problem seems resolved. Do we know the age of formation of Tiu Vallis and Ares Vallis versus Ganges Chasma ?

Free Spirit · 2003-06-12 20:21:01

Is it possible that the catastrophic floods were too short to dissolve all the olivines ? or alternatively that the floods actually carved Ganges Chasma, dissolving all olivines present, but also revealing new layers of rocks containing olivine as the flood carved more and more the canyon ?

Is there a possibility that the olivines might have been layed down through volcanic activity or some other geological process after the canyons had been carved out and went dry?

rgcarnes · 2003-06-12 20:32:38

Those of you who have been on the tour of the island of Hawaii may remember that there are black sand beaches and green sand beaches, the green sand being olivine crystals weathered from the volcanic materials which make up the island itself.

Why are we putting such emphasis on the presence of olivine as the proof of no water, when, on Hawaii, it's the Pacific Ocean action which separates and concentrates the olivine crystals and makes them readily visually observable? Seems like a tenuous position, to me.

dickbill · 2003-06-12 21:00:17

Is there a possibility that the olivines might have been layed down through volcanic activity or some other geological process after the canyons had been carved out and went dry?

I havn't seen the original article, but from the abstract that Shaun has posted, the themis data say the olivines are in a layer close to the bottom, so they are not late volcanic deposits. By the way, what kind of layers are below and above the olivine layer, do they say that in the article ?

Shaun Barrett · 2003-06-13 01:27:52

Rex writes:-

Why are we putting such emphasis on the presence of olivine as the proof of no water ... ?

When you say "we", Rex, do you mean us here at New Mars or Christensen, NASA, and the American scientific establishment?
Speaking for myself, I have taken Christensen at his word when he implies that olivine is 'delicate' stuff which quickly decomposes on contact with water. I have never actually looked up any data on mineralogy to satisfy myself that it's true.
Am I right to infer from your post that olivine is not so easily broken down by water, at least when it's salty water? ???
I can imagine a scenario whereby water already carrying a substantial burden of solutes (e.g. NaCl) might not dissolve olivine as readily. But I hasten to add this is pure supposition on my part.

In response to Josh's point, I agree that Ganges is part of the Mariner Valley rift, which appears to have resulted from the Tharsis uplift event. (It's always interested me that the Hellas Basin is almost exactly diametrically opposite the Tharsis Bulge - cause and effect? ) I don't believe anyone has suggested Ganges resulted from water erosion, though some have suggested water may have played a part in producing what looks like sedimentary layers in the Mariner Valley in general.
Dating any feature on Mars is problematic and depends on counting craters. The crater counting is only useful if you are reasonably certain of the sequence and timing of the major cratering events. But there are assumptions involved in laying down such a timetable and, recently, serious doubts have been expressed as to the accuracy of the assumptions made for Mars. In addition, unlike the situation for our Moon, we have no samples of the crust which we can date and classify. However, I think the current consensus of opinion is that Tharsis and the Mariner Valley are old features while many of the water channels nearby appear to be considerably younger.
What I'm saying here is that it seems unlikely that during the very long time Ganges has existed (and its floor is around 4000 metres below datum, remember! ) it could have avoided getting any water or water ice into it. Having said that, I must add that since so much of Martian geological history is still a closed book, it's not prudent to be dogmatic about these things.
Since all my instincts are telling me there must have been water and/or water ice in Ganges, and hence in the bedrock under Ganges too, the olivine data must somehow be wrong.

This brings me back to Rex's comments. If Christensen's olivine is really there (i.e. it's not some instrument glitch), is there any way it could have been submerged in salty water for long periods without decomposing? Is there more than one type of this mineral and could THEMIS be confusing them?
???

This whole topic has got me quite concerned. I don't want to have to defect to the Nick Hoffman "White Mars" camp!! What a depressing drag that would be.

rgcarnes · 2003-06-13 06:26:20

I've got to plead some ignorance of the decomposition rates of olivine in the presence of water. By it's presence in water (the Pacific Ocean has been shown to contain water) on the green sand beaches of Hawaii where it is weathered from the volcanic material there, I'd say it's not as soluble as sugar, or salt. Whether the salts in the water have any significant influence or not, I don't know.

The "we" I was using in my last post was not necessarily meant to be any less inclusive than the human race. It was just a figure of speach.

rgcarnes · 2003-06-13 06:36:58

By the way, Shaun, I tend to side with you on the origin of the Valles Marinaris. If one had a lump of something like clay (without very great tensile strength or great plasticity) and hit it with a projectile the relative size of the object that caused Hellas Basin, where it added both energy and volume, I think you'd see a surface crack or two. Of course, this does not rule out things like surface/subsurface water running into such a crack later. We haven't found how to keep gravity from making it run down hill yet.

Shaun Barrett · 2003-06-13 18:58:40

Good to have your input here, Rex.

I especially liked these pearls of wisdom:-

".. the Pacific Ocean has been shown to contain water .."

"We haven't found how to keep gravity from making it [water] run down hill yet."
:laugh:

I do so enjoy a touch of humour - it cheered me up considerably!

If you, Rex, or anyone else out there can solve the riddle of the Ganges olivine, I'm all ears.

Free Spirit · 2003-06-13 21:07:59

I googled olivine and it does appear that there are different strains of it. It appears there are a number of minerals that are in the "olivine" family according to this site.

According to this site Olivine doesn't fare well when it's exposed to the elements as its usually transformed into serpentine in the presence of water. If we can find a lot of serpentine on Mars would that be an indication that water had come in contact with olivine?

rgcarnes · 2003-06-13 22:15:25

Surely, the olivine question depends on the meaning of the sentence: Olivine is unstable in the presence of water geologically speaking. I could point out that our lives may be unstable geologically speaking. Can someone out there be more quantative for olivine than geologically speaking?

I too did a brief search this morning and found out basically that olivine is one of the classical examples of transformation and decomposition of a mineral, eventually, into soil, but how long does it really take?

Shaun Barrett · 2003-06-24 20:12:25

Thanks Free Spirit, Rex, and everyone for the useful comments.
My own browsing seems to show that olivine is indeed relatively fragile and one of the first minerals to decay (react) in the presence of water - which doesn't help me in my plight!

Then I came across a recent article called "Landers to Probe Mars' Waterworks".

Part of the article suggests that Ganges may in fact be a more recent feature than other parts of the Mariner canyon complex. As a result, the appearance of olivine in its depths might not be the show-stopper for Oceanus Borealis that I feared it was.
At the very least, there is room for manoeuvre because the case is far from closed.

Christensen undoubtedly feels he has a strong case against a former Martian ocean and that damned olivine certainly backs up his arguments! The vehemence of his beliefs is demonstrated by this excerpt:-

"I'm an enemy of the idea of oceans on Mars", Christensen told Wired News. "I don't believe Mars was ever a warm and wet tropical place with beaches and palm trees. But I don't argue that there isn't water. There's more ice and snow than you can possibly imagine."

Personally, I think the words he used betray more than a little annoyance with the whole notion of Oceanus Borealis; he sounds sick and tired of it all! But at least his comment about the amount of frozen water is encouraging.

The part I liked most was Timothy Parker's contribution:-

"As data comes in it seems more, not less, apparent to me that there were not only oceans but massive oceans in early Martian history", said Timothy Parker, a geologist at NASA's Jet Propulsion Laboratory working on the Mars rovers.
'My research has always been based in geomorphic comparisons, not on mineralogy", Parker said. "Geomorphic comparisons use landscapes and rock shapes. The ancient northern plains of Mars are bounded by what appear to be former shorelines", Parker said. "The Ganges Chasma, on the other hand, appears to be a newer feature."
"It's deep and a very fresh-looking canyon carved relatively recently in Mars' history", he said. "This being Mars, mind you, 'recent' can mean a couple of billion years."
"The olivine is freshly exposed", he said. "Water never had a chance to act on the olivine that may be at the bottom of the canyon."

Notice that he said "the olvine that may be at the bottom of the canyon"? This almost sounds like he's not completely convinced it's there!
But overall, he sounds like a man who is convinced there was a large ocean in the northern plains.
I think I like that man!!

Palomar · 2003-06-28 10:19:28

This is happy news

--Cindy

Shaun Barrett · 2003-06-28 22:40:19

Thanks, Cindy, for the happy news!
It will be interesting to see just how deep the ice goes, so we can calculate the volume of water still present in Mars' inventory of volatiles.
Then, if only we can find hitherto undetected stores of nitrogen, preferably in enormous quantities, we'll be laughing! Terraforming here we come!!

Incidentally, I like your new avatar.

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Re: Huge water ice reservoirs found on Mars!

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Re: Huge water ice reservoirs found on Mars!

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