Acidic water or volcanoes / impacts? The debate is on! I kind of like this actually, for my birthday today (39 now, getting old)....

Updates regarding this today from Nature, CU and Space.com:

The Waters Ran Shallow
http://www.nature.com/nature/journal/v438/...e051222-10.html

Mars Region Probably Less Watery In Past Than Thought, Says Study
http://www.colorado.edu/news/releases/2005/470.html

New Studies Question Mars Water Assumptions
http://www.space.com/scienceastronomy/051221_mars_dry.html

Regardless though of whether they are correct or not regarding the acidic sulphate deposits in these scenarios, the earlier clays are still another matter...!

The Space.com article includes comments from Squyres (who it says was not contacted prior to the article being published):

"Squyres said a deeper understanding of the situation came when Opportunity examined Endurance Crater, where observations were made of 25 vertical feet of rock outcrops. Those results were published just a month ago, after the two Nature papers had been submitted. Knauth, McCollom and Hynek "hadn't seen that stuff when they wrote their papers," Squyres said. The nature of the layering and grain sizes deeper inside Endurance Crater "is absolutely incompatible with a volcanic or impact origin," Squyres said. It is "completely compatible" with the idea of windblown material, and the upper meter or so "shows evidence for deposition of water. The chemistry varies with depth in a way that requires that subsurface liquid water interacted with the rocks after they were deposited." Squyres emphasized that his team has always thought the water was mostly underground, occasionally creating small surface lakes that evaporated quickly. Squyres also stressed that nobody has done anything other than good science with the data available. "It's always good to have alternative hypotheses," he said. "In the end, the best ideas win. It forces everybody to go back and sharpen their arguments. All of this is a good thing."

Volcanic ash layers I might believe in. But they would have to be very altered to lock like the Meridiani rocks.

An impact origin is ridiculous. The only way an impact can result in a thin layer of fine materials is through distant fallout of fines ejected from the crater. Having tens of meters of such thin layers but no thicker layers with coarse material requires that there were lots and lots of impacts far away but not a single one near Meridiani. And all those impacts would have to be both BIG and very far away since the laminae are thicker than e. g. the Chicxulub impact layer.

tty

Odd that people are still wondering if there was ever flowing water on Mars. I would think that that one orbital image of the interleaved "fossilized" channels in a clear outflow delta would leave no doubt.

And once you concede that there was water on Mars at one time in some places, water action becomes the simplest explanation for much of what we have seen in Meridiani. Other explanations seem contrived at best.

Scott

I've been engaged in an E-mail exchange with Brian Hynek for some time -- and I'm still trying to get a straight answer out of him as to why he thinks that the sulfuric acid to which the original Meridiani ash or sand was exposed had to be in the form of steam rather than cool liquid. More news when I get it.

AlexBlackwell started a similar thread in the Mars topic, but this is where the action seems to be.

I couldn't believe the hype on these new Nature articles that exploded in the news media today. When I checked my web page collage of science news this morning I found three or four links to various articles from normally trustworthy sources claiming that the Mars scientists had screwed up, and that liquid water was not needed to explain the observations of the rovers.

I am waiting for someone to send me copies of those articles, but in the mean time I have been making a mental list of observations that would support one or the other of the various hypotheses (surface water/groundwater and wind, volcanics, or impacts), and I have a difficult time buying into the new hypotheses.

You folks have already pointed out a lot of the problems with the new hypotheses, and we can elaborate on them later. But I agree, they do appear to be "contrived," or at least based on limited data. Yeah, I can imagine some special conditions like a "ground-hugging turbulent flow of rock fragments, salts, sulfides, brines and ice, leaving deposits that were later weathered by small amounts of water embedded in the grains." But is that the most simple explanation of the MER observations? Does it make sense to imagine such things when images of the planet's surface from orbiters show so many examples of fluid flow shaping the geomorphology of Mars? I think not.

As usual, I think SS said it best in that space.com article. The observations seem clear, but debate is healthy for good science. This will be a fun debate to follow...

I agree that it's both interesting and positive for alternative hypotheses to be considered, precisely because such debate forces everyone to re-examine both the evidence and their own assumptions.

For example, SRAnderson points out the numerous eroded (apparent! ) outflow deltas. Given their generally presumed age of 3.5By or so, is this consistent with any erosional models that might have been developed based on the results of MGS and subsequent missions? Surely we must have some basic feel for at least the steady-state wind erosion rate on Mars by now; in fact, it seems that latitiude and topologically-induced micro-climates may play at least as significant role in local surface conditions as they do on Earth.

The point of that thought is that this comparison might provide some constraints on what are essentially catastrophic formation theories for Martian sedimentary deposits. In my opinion, the highly structured (low entropy?) appearance of the Meridiani formations combined with the very regular layer spacing strongly suggests a periodic series of climatogical variations rather than ad hoc eruptions as the mechanism responsible for the terrain's formation. Whether the medium responsible for deposition was wind or water is still an open question, although it's probably a bit of both...

...and on that last note, what do you think of periods of high local humidity followed by dust storms that cause layers of thin mud to s-l-o-w-l-y build up at Meridiani? Actual standing surface water may not have been necessary; I wonder just how much relative humidity in that atmosphere would be enough to cause all that exceedingly fine dust to stick together...

Contrived is a good word for it. I was glad to see Space.com at least update their original story to include Squyres' comments.

Jon Clarke has provided a good listing of features more consistent with groundwater / salt lakes than volcanoes or impacts (hope you don't mind the link, Jon):

http://uplink.space.com/showthreaded.php?C...d&sb=5&o=0&vc=1

Take a look at spacetoday.net, this new theory is popping up everywhere in the press and being taken as fact now.

The sulfate enriched and altered rocks and the sulfate cemented sandstone at Gusev are the sorts of things I'd expect from the impact scenario. The volcanism scenario utterly lacks a volcano or volcanos that would have deposited massive layered deposits over an area bigger than Oklahoma. I consider both hypotheses dead-in-the-water.

http://www.spaceflightnow.com/news/n0512/21marswater/

Is the dream of a shallow sea finally over?

There has been a definite "movement" out there, ever since 1971 and the Mariner 9 testament, of some people who want to find some way (ANY way) to explain the obvious fluvial features in such a way that does not require there to have ever been liquid water on the surface of Mars.

Why? Mostly, I think, because liquid water cannot exist there *now*. To accept the validity of the features as fluvial, you *must* accept the concept of a severe climate change having occurred on Mars.

Whereas, to accept them as non-fluvial, you *must* accept that some Mars-specific process creates features that *look* fluvial, but thata ctually are not.

That's why some people keep barking up the no-water alley. Because, either way you look at it, you have to accept the postulate that something happened on Mars that we cannot easily explain, or understand.

I'm still in the early-water camp, because there are established and understandable mechanisms by which Mars' climate could have evolved from a higher-air-pressure, much wetter environment to its current low-pressure, bone-dry existence. The "contrived" mechanisms that have been proposed to explain relatively small-scale fluvial-appearing features fail (for me) on a number of levels, including the fact that they don't account for how widespread the fluvial and other water-related features (such as the Meridiani sulfate-rich sedimentary deposits) actually are.

So, for me, "Blue Mars" works better than "White Mars." But YMMV.

-the other Doug

Ah, the side-road of the brine-splat speculation.

Although alternate theories can be stretched to fit the observed data on Mars, the most comfortable fit is the warmer, wetter Mars. Maybe not to the extent of vast tepid inland seas, but certainly more so than the high arctic desert we see today.

--Bill

I knew this would happen... and most do not even bother to get Squyres' input. I'm glad Space.com did though. And I like Squyres' comments in today's Rocky Mountain News:

"But the lead scientist on the Mars Exploration Rover (MER) mission dismissed the CU idea as misguided and uninformed. Cornell University's Steve Squyres said the Boulder scientists did not have access to reams of recent Opportunity data, all of which "really solidify the case that water was involved in a very substantial way at this place."

http://www.rockymountainnews.com/drmn/loca...4334345,00.html

I just got the publications today, but I haven't had a chance to read them yet. But it really is nuts how the press has picked up this ball and ran with it. They have no idea what they are talking about, but it's controversial, and it might sell a few more papers.

I'm with you and hoping but are we letting our judgement be clouded by wishful thinking?

My recollection is that Gusev Crater was supposed to be one of these places "with widespread fluvial and other water-related features". So far only an ocean of basalt sponged over with a wet rag is all we have seen.

It is worth remembering that the early Mars "could have evolved from a higher-air-pressure, much wetter environment" but 4billion years ago the solar output may well have been 40% less than today and Mars may have in fact have been colder than today. Brief events of volcanically heated water before it all froze solid may be the best we get.
The global distribution of pyroxene and olivine is difficult to reconcile with a wet past

On that note, let's not forget about the Tharsis uplift and the atmospheric effects of long-term episodic vulcanism. Periodic atmospheric pressure increases from heavy outgassing (the effluent presumably would also include water vapor) might have not only allowed liquid water to exist on the surface for prolonged periods, but also facilitated melting of permafrost and subsurface ice from greenhouse warming. After the volcanoes shut off for awhile, the atmosphere thins out again, the water freezes out, and another layer at Meridiani is formed...?

A little more on the post-volcanic freeze-out scenario: After the atmospheric pressure falls down to near present levels, ice at equatorial locations sublimes into vapor during the summer and eventually ends up in the polar/subarctic regions. The cycle repeats and redistributes water globally when the volcanoes get froggy again.

The very thin layers observed in the Meridiani sediments might lend credence to this theory. The warm periods might not last very long at all, and in the meantime the dust keeps on a-blowin' (in fact, probably with considerably more vigor), and thus offer a counterbalance to the greenhouse effect by increasing the planet's albedo during global storms. Once the storms subside, things warm up again and the dust settles where it will. Meridiani would look like a giant mud pit during these periods as the dust gums up nascent puddles.

Well, Spirit has found evidence for water alteration, although not as "exciting" as Opportunity. But again, as noted previously, it has also found evidence for clay deposits on Husband Hill and traces of carbonates. There is also (again) the global distribution of clays, albeit isolated patches so far (although widespread), found by Mars Express.

I don't know how this reconciles with the olivine, but it can't be just ignored, either. The clays in particular, as currently understood, would have required less acidic and longer-lasting water to form (although still limited to very early in Mars' history apparently). This has also been mostly ignored in the flurry of news reports the last couple days re the new CU Meridiani "revelations" which started this thread...

It must be a frustrating position to be in to produce new papers using the complete Mars data set as released by the MER team knowing the MER team has a great deal more recent data that only they have access to which might contradict the outsiders' papers.

True - but the MER team does deserve to have the first crack at things and they have an obligation to make sure that the data is fully validated before opening it up for everyone. After all they are the ones who put the long term effort in to get the mission and its instruments up there in the first place.
And no-one forced the UC team to publish without the additional data - they could choose to wait to see if it would reinforce or contradict their paper but getting it out early might well be more important and that's not an uncommon dilemma even for the main scientific teams.
The bad reporting on this is a bit disappointing but overall it seems to be generating good healthy discussions on the science.

Imagine that all Earth's water froze out at the poles just 200 million years ago. Something like 75% of Earths surface would be covered by fresh, unaltered volcanics by now (=all ocean bottoms, Deccan, Ethiopia, Snake River/Columbia plateaus, Iceland, Ontong Java plateau, Kerguelen plateau, CAMP etc etc).
This despite the fact that most of the Earth's surface would have been covered by water, and all of it modified by water for the first 95% of its history.

If there was water on Mars only pre-3,5 bya I think the odd thing is that so many traces still remain.

tty

I received an interesting e-mail this morning from Tom McCollom at Colorado University, one of the authors of one of the new research papers in question. Quote:

"First, we considered in our our article all of the chemical compositional data that have been published to date. The chemical compositions on which the more recent interpretations mentioned by Steve Squyres are based have not been published, and the MER team refused us access to these data when we requested. However, based on what we have seen in recent publications and information presented at conferences, there is nothing in these new data that would be inconsistent with our volcanic scenario, contrary to the claims that Squyres has made in the mass media. We intend to demonstrate this as soon as the data are made available to the broader scientific community."

This will be a long debate...

More articles also:

ASU geologists suggest Mars feature linked to meteorites, not evaporated lakes
http://www.asu.edu/news/stories/200512/200..._meteorites.htm

Mars Not so Wet After All?
http://www.nature.com/news/2005/051219/full/051219-10.html

And a new phyllosilicates abstract:

Phyllosilicates on Mars and implications for early martian climate
http://www.nature.com/nature/journal/v438/...ature04274.html

These ASU people are positively dotty:



Impact base surges form meandering rivers, oxbow lakes, deltas with distributaries and inverted valleys?

tty

Looking at this data on a day-to-day basis we (here at UMSF) tend to kick around some strange explanations of what we are seeing on Mars. But this is normal brain-storming; with this normal winnowing process the chaff is blown away and we end up with a reasonable description. But if you devise odd alternative explanations it's not always wise to etch these in stone in case they are mis-proclamations. Some of what they are claiming is, uh, almost, uh, culinary...

--Bill

The "patchy" nature of Mars' surface with respect to evidence of hydrological alteration argues for comparatively brief, somewhat localized wet periods, but not as brief as impact-induced events; Meridiani's geology alone provides ample evidence of that. Regional vulcanism augmented by the greenhouse/dust-storm loop I mentioned in a previous post seems to offer a little more flexibility for both duration and location.

One fundamental attribution error that may be occurring right now in this debate is the assumption of extremes: Mars either had to be globally "wet" or globally dry. There are undoubtedly a number of situational contingencies yet to be considered that, when understood systemically, explain the observations. Mars may be a dynamically simple place in comparison to Earth, but we've already seen a bewildering variety of local variation in landforms that hints at underlying complexity in the planet's geological and climatological histories.


EDIT: corrected HTML tag errors.

I'm trying to keep an open mind, but it sure seems difficult to explain _all_ of the evidence for water on Mars with these basal surges, even if they can make thin layers with sedimentary structures. But it is true that only the MER team has all of the MER data. What they have released has been pretty convincing for me, though.

But the people who wrote these new papers are good scientists, too. I can't imagine they would risk making fools of themselves unless they thought they had a good story to tell. They did manage to publish in Nature, and that is still one of _the_ premier places to have your paper published. This is the scientific process taking place, regardless of the fact that the various news media are distorting the story.

Steve Squyres has another brief update up today, and among other interesting things, he has a comment on this debate.

http://athena1.cornell.edu/news/mubss/

It's interesting also that the new phyllosilicates abstract from the OMEGA team that I linked to in post #23 is in Nature as well, which gives it seemingly good credibility. In his e-mail today, McCollom also dismissed those same phyllosilicates findings... he did make a good point though, that clays can also form in hydrothermal environments, even acidic. But don't they usually form in less harsh conditions (as OMEGA has stated)? Can any of the geologists here elaborate on this a bit? I'm not a geologist, but I am a serious researcher (I was doing astronomy / space talks as early as grade 4 even - weird kid...).

Oh man, I'm way behind on the clay stuff. Thanks for the reminder. Gotta get that paper and add it to the pile.

The important thing to keep in mind is that ALL the chemical evidence of exposure to non-acid liquid water goes all the way back to the Noachian, which is a long, long time ago -- 3.8 billion years at the latest. Since then, there were occasional gigantic surface discharges of non-acid water during the Hesperian, and there are occasional fair-sized ones (mostly driven by local volcanic heating) to this day -- but they all freeze into solid ice, and then sublimate directly away into the thin atmosphere, so fast that they don't have time to chemically modify the silicate lava rocks which they come into contact with. The OMEGA team has emphasized exactly this in its reports.

Frankly, I'm starting to think that MER-A's studies in the Columbia Hills may end up being more scientifically valuable on balance than MER-B's studies of Meridiani. The latter was a single unusual, highly specialized phenomenon, of a type whose environment was likely to be unfriendly to life (or at least to its initial creation) -- but what we're seeing in the Hills seems to be a smorgasbord of surface materials from all sorts of different places on Noachian Mars, all thrown into the Hills by giant impacts and, as a total, far more representative than Meridiani of what Noachian Mars was actually like. (Including those probable clays in the "Independence" outcrops, which may are likely to have been created at the Hills themselves by exposure to regular water.)

If you REALLY like irony: the landing site picked for the stationary 2001 lander before it was switched to Meridiani was the Libya Montes on the southern rim of Isidis -- which OMEGA has now shown to alternate large amounts of Noachian clays with bands of more recent olivine melted by the giant Isidis impact and then splashed over parts of the clay area. What would the 2001 Lander (which had a precision landing guidance system) have seen if it had landed on top of one of those clay deposits and examined it with its MECA microscopes (and for that matter its wet-chemical analyzer)?

Absolutely!
The problem I have and what I assume that most others in this thread have, are not the findings of a sulfate dominated hydrology that might be ground-water only / or even simply fog that have reacted with volcanic minerals.

Whats so odd about that? Its from a late time and so almost what to be expected to see on the surface judging from the conditions we see today.

Sorry for stating the obvious: What we see here have to be from a rather late chapter of the Martian history for the simple reason its found on the top!
And more or less judging the entire history of the site only from looking at what you can see from the surface can only be misleading indeed.
(Yes I know you guys in the USA got dinosaur bones near the surface in some areas but thats due to erosion and only 65+ millions year in any case, even the Cambrian Period of ~540 mya are too recent for what we are looking for here.)

The problem that I have are how those who are supposed to bring the news out to the less scientifically inclined masses, have turned facts into a UFO story.
But yes that must have been the case, the regular staff went on christmas leave and they brought in replacaments from National Enq.......

.....but yes, Merry Christmas to all of you!

Note that from the Mariner 9 discovery of outflow channels and the dendritic highland channels, that there was a continuous chorus of alternating viewpoints that the features were eolian in origin, or alternately involved cold fluidized erosive flows driven by CO2/Water clathrate ice releases. Most of these theories have faded, but their supporting team's efforts at pushing those alternatives to water erosion lasted well into the 90's.

One -- but only one -- of the articles on MER-B's findings in the 11-30-05 "Earth & Planetary Science Letters" is now available for free at http://www.geol.umd.edu/~kaufman/ppt/G436/...ry/Knoll_05.pdf :
"An Astrobiological Perspective on Meridiani Planum" by Andrew Knoll et al.

A very interesting piece, confirming that it would be a difficult place for life to have evolved out of prebiotic organics -- but also listing several reasons why it might be harder for even already-existing microbes to survive in than similar acid environments are on Earth (mainly because they have a larger supply of various highly useful chemicals coming in from outside). We have GOT to get a good look at one of those non-acidic clay deposits.

Gotta get to Victoria folks.

Craters are to Martian geology as road cuts and canyons are to Earth geology.

Scott

Yep. We have got to see more of the section. There's no debate there. But this is a really interesting place. It's too bad Opportunity has been immobilized for so long. There are targets all around it that would fill in some of the details.

There seems to be quite a fight brewing in this Great Meridiani Debate. It's quite interesting to watch. My best guess at this point is that they are arguing about a location for a sample return mission. Anyone have any other ideas?

I think debate might have some impact on the sample return mission and where to send the Mars Science Rover in 2009 but no decision will be made until the MRO has arrived and done it's thing.
There is so much to see and find out about.
Eos Chasma looks good and I understand they have detected granite in a part of Tharsis!

Reckless

We do need to see more of the section, but this is a good exposure and we need to look closely at "C" on this A-B-C-D roadtrip. Oppy does need to get moving to the next target, but evidently there are concerns about the unstowable IDD.

We'll get on the road "eventually".

--Bill

I'm not sure if anyone has posted anything new on this or not but, for those without access to EPSL, I'll note that two more papers from this issue are now freely available on the web: Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars by McLennan et al. and Chemistry and mineralogy of outcrops at Meridiani Planum by Clark et al.

I have access to EPSL, at the SOEST library, but appreciate the heads-up anyway.

So do I. And you're welcome However, I'm pretty sure the vast majority here don't have access, and there seemed to be some interest in these papers.

I been wondering for some time now if we could see a sample return collector rover enter say endurance crater,that exact crater.We know what's there. If you send the sample return rover to some other part of the planet or some other part of Meridiani Planum you don't know exactly what you would find. Would you want to take the risk of sending it to location that your not definitely sure of because you haven't been there on the ground and may not get the sample your after. Of course we don't know what MSL is going to find that you might want to bring back to Earth.that could change this equation.
That would be strange to see a return sample rover entering Victoria crater and seeing a broken down oppy or a oppy that has taken a suicide plunge into the crater.

Could a scenario like this take place ? In 6-10 years could we obtain this degree of accuracy in a landing site ?

Heck, yeah! Why not? If I read the latest bumpf on sample return correctly, there is likely to be a Rover robot (Rovers are the flavor of the year, in case you haven't noticed! ) which runs around collecting a bunch of samples, then brings them back to a stationary ascent/return stage, loads them aboard, and the latter blasts off back to earth! Sweet, huh? If Oppy finds something exciting enough at Victoria - like maybe a stratigraphic history of watery phases at Meridiani - The engineers might design a specific Victoria Probe , with a telescoping sampler arm to reach up across the whole exposure and sample the whole history. (That's a freebie, JPL, run with it!) Maybe there'd even be room to bring back Oppy's cold little form for a respectful burial on his home planet. (insert emoticon for choking sobs)

yes I had also read that a rover would be part of a sample return mission,I wonder if after the rover collected the samples and were on their way back to earth if the rover would be made to continue on with a full blown mission of it's own.
About oppys return,I've always thought that some day hundreds and hundreds of years from now that one or both of the rovers could/would be returned to earth and to a museum.

Shoot, yeah! Y'can't kill the little beggars!


Won't take that long. The problem will be the fierce bun-fight between the earthlings and the martians over right of possession! The earthlings will say, Hey, we made the #&%* thing! The martians will say, Bells!, It landed on our turf, and is an integral part of our history and culture!
Who do you think will win?

I'd rather Spirit and Opportunity stayed over there. Gusev and Meridiani are home for them. They should stay there, wherever they stop working, and then people should be able to, a hundred years from now, visit them and wonder at the little rovers that taught us so much.

The wheel tracks will be long gone, but in my minds eye - I've often walked along Spirits route, looking at old rat holes, scraping out the dust with a gloved finger, and sat upon the rim of Endurance crater.

Doug

I've been daydreaming along the same lines, that someday my great-grandchildren might hike the Spirit Interpretive Trail in Gusev Planetary Park. Hopefully they'll be able to keep the tacky tourist shops to a minimum. Though if I'm still alive, I wouldn't mind getting a "My Grandkids went to Gusev and all I got was this lousy T-Shirt" shirt