Andrew Knoll, Fisher Professor of Natural History, Harvard University, Department of Earth and Planetary Sciences

Yeah, I sure do wonder if that Andy Knoll guy checked the literature before he started offering his opinion...

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Again, there is the evidence from Mars Express for a more benign (less acidic/salty) environment predating the harsher (more acidic/salty) one. But this crucial point still seems to get overlooked...

Paul

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The Meridiani Journal
a chronicle of planetary exploration
web.mac.com/meridianijournal

Also evidence that the acidity is a result of later weathering and not original deposition.

Jon

To echo what Paul said, I found these articles:

Martian Clay.
"Although both sulfates and clays form in the presence of water, they form under different conditions. Clays form when silicate rocks - quartz and feldspar, for example - are exposed to water, lots of water. They form in neutral or basic environments, not highly acidic ones. And they form under temperate conditions. The process is not a quick one. Clay formation can take hundreds of thousands, sometimes millions, of years. It can occur on the surface, but it "more typically occurs in the shallow subsurface, a few hundreds of meters below the surface," says Mustard.
"Sulfates, in contrast, can form relatively quickly. And they are the product of evaporation. They form as water leaves an environment, not when it hangs around for millennia. Mars's sulfates are believed to have formed under highly acidic conditions."
http://euro.astrobio.net/news/article1937.html


MEETING: AMERICAN GEOPHYSICAL UNION:
An Early, Muddy Mars Just Right for Life.
Richard A. Kerr
"SAN FRANCISCO, CALIFORNIA-- When the Opportunity rover found the salty sedimentary remains of standing water on Mars, the prospects for early life on another planet brightened considerably. Although acid-laden, those early waters were nothing that martian life couldn't have adapted to. It's harder to imagine life originating under such conditions, however. Now, by analyzing the infrared "colors" of the martian surface, planetary scientists have identified clayey rocks that mark an even earlier warm and wet era, one more persistently wet and blessedly less acidic. The origin of martian life now looks brighter too.
"Key to refining the water history of Mars was the powerful OMEGA spectrometer aboard the orbiting Mars Express spacecraft. OMEGA can probe the ground in enough detail and in the right range of infrared wavelengths to identify the distinctive absorption peaks of clays and sulfate salts (Science, 6 August 2004, p. 770).
"Since announcing the first firm detection of martian clay last March, OMEGA team members have formed a clearer picture of how clays fit in the geologic history of Mars, reported OMEGA team leader Jean-Pierre Bibring of the University of Paris South in Orsay. Clays and the sulfate salts that mark the Opportunity deposits do not generally occur together, they found. And clays seem to have formed in a time before martian acid was corroding rock to produce the sulfate salts. In the Nili Fossae region, for example, clays appear beneath-- and therefore were deposited earlier than--fresh, unweathered rock rich in olivine. They may even have formed before the early giant Isidis impact of some 4 billion years ago. All in all, clays appear to have formed within hundreds of millions of years after the planet did, and before the sulfates formed, said Bibring, about the time life could have been appearing on Earth.
"That timing--first clay, then sulfate--boosts the prospects for life on Mars by providing it with a possible birthplace other than the later acid bath. "The kind of chemical reactions we think were important to giving rise to life on Earth simply could not have happened" under the conditions Opportunity found, says paleontologist Andrew Knoll of Harvard University, a rover team member. The pH 1 sulfuric acid that leached rock to produce Opportunity's sulfates would have worked against the evolution of increasingly complex organic compounds that could lead to life. And it wasn't even always wet. The Opportunity landing site wasn't a "shallow sea," as initially assumed, but a salty sand sea with intermittent puddles between the dunes, team members write in a set of papers in the 30 November issue of Earth and Planetary Science Letters.
"Clay, on the other hand, connotes a more hospitable environment, Bibring noted. The earlier clay era was "probably most favorable to have hosted the emergence of life," he said, "and could still host biorelics." On Earth, the smectite clays identified by OMEGA form under the mild, more continuously wet, and far less acidic conditions of the midlatitudes. OMEGA data are "pretty good evidence" of "more Earthlike conditions" on earliest Mars, agrees planetary geologist James Head of Brown University. Now planetary scientists must decide where to send their next, far more capable rover: to the well-characterized and safe Opportunity site, one of the newly enticing but poorly understood clay sites, or somewhere else found by the upcoming Mars Reconnaissance Orbiter?"
Science 23 December 2005: Vol. 310. no. 5756, pp. 1898 - 1899
http://www.sciencemag.org/cgi/conten...310/5756/1898b


Bob Clark

In the news releases Knoll doesn't say which types of organisms he is referring to that can survive in salty environments but is notable that certain types of fungi can also survive in high levels of salinity, and at below freezing temperatures. This is interesting because fungi have a nucleus, unlike simple bacteria, and are therefore considered to be a more advanced life form than bacteria. In fact they are sometimes regarded by biologists as being more closely related to animals than to plant-life.

Life Sci Space Res. 1979;17:95-8.
Growth of fungi in NaCl-MgSO4 brines.
Siegel SM, Siegel BZ.
Department of Botany and Pacific Biomedical Research Center, University of Hawaii, Honolulu, Hawaii 96822, USA.
"Long-term studies have shown that common fungi of the Penicillium-Aspergillus group can be grown in a variety of brines or on moist salt crystals, simulating a range of natural terrestrial habitats such as salt flats, or special water-bodies such as the Dead Sea. In general, salt media rich in KCl are favored over other alkali halides; the media become more selective as the salt concentration rises and nutrient requirements become more complex. We here demonstrate that media which resemble the Dead Sea salt mix can support the growth of selected fungal strains, even in the absence of reduced organic nutrients other than glucose. Such media may serve as models for localized microhabitats on Mars."
http://www.ncbi.nlm.nih.gov/pubmed/12296355

Life Sci Space Res. 1976;14:351-4.
Performance of fungi in low temperature and hypersaline environments.
Siegel SM, Speitel TW.
Department of Botany, University of Hawaii, Honolulu, Hawaii, USA.
"During the past ten years we have observed a broad array of stress capabilities in common fungi including ability to grow in aqueous ammonia and other alkaline solutions, in acids, in the presence of heavy metals, and in various salt media at low temperature. This report is concerned primarily with (a) the performance of Aspergillaceae in a variety of saturated salts, (b) distinctive roles for K+ and Rb+ ions, and (c) the lowest temperatures at which growth in nutrient brines has been observed, namely 267 degrees K in as little as 14 days. We also describe a novel solid medium based upon gelatin, glycerol and water in which fungal cultures growing at 248 degrees K can be directly examined under oil-immersion magnification. The performance capabilities of the fungi show that tolerance or adaptability to harsh and extreme physical-chemical environments cannot be considered a unique feature of prokaryotic life forms. Salt flats, brine pools and other natural hypersaline environments have long been recognized as real ecological niches harboring a range of biota from pseudomonad bacteria and green algae to specialized crustaceans. A notable omission in this ecological record is the fungi, although the group is known to include marine forms."
http://www.ncbi.nlm.nih.gov/pubmed/12678120

Bob Clark

Along those same lines: Lichens in spa-a-a-a-ace!

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Just saw this link on the Markcarey.com/mars forum:

http://en.wikipedia.org/wiki/Haloarchaea

Interestingly it says they can survive in salt concentrations up to saturation. This means physically as much salt that can possibly be dissolved in water. So the Meridiani concentrations couldn't be any higher than this, yet life was still able to survive under such conditions.


Bob Clark

Further refs on life surviving at or nearly at saturation levels of salts:

Brine organisms and the question of habitat-specific adaptation.
Origins of Life and Evolution of Biospheres.
Volume 14, Numbers 1-4 / December, 1984
"Abstract Among the well-known ultrasaline terrestrial habitats, the Dead Sea in the Jordan Rift Valley and Don Juan Pond in the Upper Wright Valley represent two of the most extreme. The former is a saturated sodium chloride-magnesium sulfate brine in a hot desert, the latter a saturated calcium chloride brine in an Antarctic desert. Both Dead Sea and Don Juan water bodies themselves are limited in microflora, but the saline Don Juan algal mat and muds contain abundant nutrients and a rich and varied microbiota, includingOscillatoria,Gleocapsa,Chlorella, diatoms,Penicillium and bacteria.
In such environments, the existence of an array of specific adaptations is a common, and highly reasonable, presumption, at least with respect to habitat-obligate forms. Nevertheless, many years of ongoing study in our laboratory have demonstrated that lichens (e.g.Cladonia), algae (e.g.Nostoc) and fungi (e.g.Penicillium,Aspergillus) from the humid tropics can sustain metabolism down to –40°C and growth down to –10°C in simulated Dead Sea or Don Juan (or similar) media without benefit of selection or gradual acclimation. Non-selection is suggested in fungi by higher growth rates from vegetative inocula than spores. The importance of nutrient parameters was also evident in responses to potassium and reduced nitrogen compounds.
In view of the saline performance of tropicalNostoc, and its presence in the Antarctic dry valley soils, its complete absence in our Don Juan mat samples was and remains a puzzle.
We suggest that adaptive capability is already resident in many terrestrial life forms not currently in extreme habitats, a possible reflection of evolutionary selection for wide spectrum environmental adaptability."
http://www.springerlink.com/content/r0565304t64835nv/

Reports
The Enigma of Prokaryotic Life in Deep Hypersaline Anoxic Basins.
"Evidence that microbial life is possible at 5 M MgCl2 widens the picture of microbial adaptation to salinity. It has been suggested that primordial life on earth started in hyper-saline water (28, 29); furthermore, extra-terrestrial objects are known to contain brines exposed to evaporation, which results in an increase of divalent cations (30, 31). Our results indicate that microbial metabolism can proceed at significant levels in some of the most extreme terrestrial hyper-saline environments and lend further support to the possibility of extraterrestrial life."
Science 7 January 2005: Vol. 307. no. 5706, pp. 121 - 123.
http://www.sciencemag.org/cgi/content/full/307/5706/121


Bob Clark

Since I became interested in this subject I've heard a lot of arguments for both sides, but seen precious little evidence that isn't hotly disputed. IMO there are two parts to the 'life' question: 1: can life survive and reproduce on mars and 2: if yes then does it? Answering the second part is likely to take a long time, perhaps many decades, but it seems to me that to answer the first is much more do-able, we just need to contaminate a spot on mars with a broad spectrum of microorganisms such as those mentioned above and see if any manage to survive and reproduce. I know many will will be horrified at the idea of deliberately contaminating mars, but unsterilized space craft have already been there, and if humans make the trip avoiding contamination will be almost impossible. Why not accept that and do it in a controlled way that will teach us something?


Edit: A brief search shows the error of posting without forethought: of all the listed polyextremophiles I cant find any that combine resistance to extreme cold and dessication with halophilic properties. I've also remebered a report on 'special zones' by nasa finding that there were no sites on mars with both enough water and enough heat to sustain reproduction by any terrestrial microrganism. I'd still like to see such an experiment though, I bet there is something hiding in the mcmurdo valleys somewhere that could make it through at least a few cycles of cell division if landed in the right spot.....

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I think it's likely that early Mars produced some simple microbes. It didn't take long for life on Earth to get started and the early conditions on Earth were not as nice as they are now. As conditions for life on Mars got worse, these simple lifeforms probably died out long ago on most of the planet. If we do extensive digging where the water once was, and use microscopic imagers, we will probably find some evidence of extinct microbial life. I think our best chance of finding life that is alive now, is under the ice at the poles. I would be surprised if we don't find any simple life living under the ice.

BTW, I like your screen name.

What is also interesting about that "The Enigma of Prokaryotic Life in Deep Hypersaline Anoxic Basins" report in Science is that it also gives references that argue that in fact Earth life may have started in hypersaline environments, in constrast to the Knoll view that it could not have started there.


Bob Clark

Thanks Bob,

Isaac Asimov is my favorite science fiction author. I remember reading "The Foundation Trilogy" when I was 12 years old. After that, I read many other works by Asimov, fiction as well as non-fiction. He was a true master in the art of writing. One the great thinkers of our time.

As for life under the Martian Polar Caps; I think that if early life spread to that those areas before it was wiped out elsewhere, it should still be there - alive and well. Microbes are very adaptable little buggers. Once they get a foothold, they are very difficult to kill off entirely, and that ice may offer a nice protected area for them to continue living. I would love to see some type of rover that can travel on the ice and be able to take core samples to a fairly deep level. I'm skeptical of any lander that searches for life by digging a shallow trench, but one can still hope for success. Of course the best way to conduct a search for life would be for humans to go there themselves.

Miles below the Earth, there are mircobes living. On Mars, any mircobes there would be under the soil. Mars is still geologically active and there my be some heat for the mircobes to survive.

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Fields of Space

LOGIC, n.
The art of thinking and reasoning in strict accordance with the limitations and incapacities of the human misunderstanding.

In the Year 2525.

"One small step for (a) man. One giant leap for mankind".

If an astronaut doesn't need good grammar, niether does you.

Host of Seraphim

I agree that there may be microbes deep under the soil. I think that the ice caps possibly offer a better environment for some sort of an ecosystem because of the amount of frozen water present there. The best case would be if Mars had a geologically active area under the ice, there might be a liquid water lake deep under the ice. Even if all water at the poles is frozen, there is still a good chance that life still exists there, as there are many types of simple life that live under the permanent ice caps here on Earth. Life on Mars would have probably adapted to harsher living conditions.

Mars does have a perminate perma-frost layer all over it's surface. Even at the equator. Though, there is more water in the ice caps, Mars was and is a water rich world. It even has/had(?), a greater water ratio than Earth does!!!

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Fields of Space

LOGIC, n.
The art of thinking and reasoning in strict accordance with the limitations and incapacities of the human misunderstanding.

In the Year 2525.

"One small step for (a) man. One giant leap for mankind".

If an astronaut doesn't need good grammar, niether does you.

Host of Seraphim

We have no evidence that's true.

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