The Search for Life on Mars - and Earth: A Call for Objectivity.

[A.DIM]

G. Levin recently published this paper in the notorious Journal of Cosmology.

Abstract: The primary focus of NASA's Mars and other planetary exploration programs, such as Titan, Enceladus, and Europa, “is to determine if life is or was present.” The author suggests that NASA's stated primary focus should, therefore, include a re-examination of the data from the 1976 Viking Mission Labeled Release (LR) life detection experiment. That experiment obtained repetitive strong positive signals supported by a variety of controls, altogether signifying the detection of microbial metabolism in the top few centimeters of the surface of Mars. The data fall well within those obtained from hundreds of terrestrial LR tests of soils and microbial cultures that made up the response library assembled for the Viking LR experiment. No physico-chemical theory or experiment of the many attempted over the years has duplicated or explained away the Viking LR results as indicative of life. Together with pertinent findings on Mars and Earth since Viking, the possibility of microbial life on Mars has become a singular scientific issue warranting the herein requested re-examination of the Viking LR data.
An elaboration of the Viking LR could seek to confirm the Viking results. The experiment would probe the active agent on Mars for a chiral preference in reacting with the LR nutrients. Chiral preferences are a strong characteristic of all known life, but play no role in chemical reactions. A finding of chiral metabolism would unambiguously prove the existence of extant life, even to the most critical observers. Moreover, were a chirality found that was different to that now known for terrestrial life, the finding would be strong evidence for an independent origin of that life form, even if it were found on Earth.

[R.A.F.]

How can G Levin maintain objectivity, when it is the conclusions of his Viking experiment that are in dispute??

How much personal "hubris" is involved here? Is this just about "being first" to discover other worldly life?

I mean, what's the rush?? The Mars Science Laboratory launches in 24 days, and will "soon" arrive on Mars. Why not simply await the results of more conclusive experiments??

[A.DIM]

How can G Levin maintain objectivity, when it is the conclusions of his Viking experiment that are in dispute??

To me it sounds as if he's merely requesting a renewed analysis of the Viking LR results.

Here's another perspective:
The Viking Labeled Release Experiment Controversy: Why Does It Exist And When Will It End?

I mean, what's the rush?? The Mars Science Laboratory launches in 24 days, and will "soon" arrive on Mars. Why not simply await the results of more conclusive experiments??

Except that MSL is not a life detection experiment. There hasn't been one since Viking.

[R.A.F.]

To me it sounds as if he's merely requesting a renewed analysis of the Viking LR results.

To me, it sounds like he wasn't "satisfied" with the results of his Viking experiments and wants a "do over".

Even with a "do over", there is no reason to assume that he would be "satisfied" with anything less than detection of life.

"If" the "do over" resulted in the detection of life, Levin would instantly become the most famous scientist since Einstein...so he has nothing to lose and everything to gain...

I just don't see how ANYONE could maintain objectivity in a situation like that...

Here's another perspective...

Can you show that to be a completely unbiased "perspective"?

Except that MSL is not a life detection experiment. There hasn't been one since Viking.

Right about the latter, but not the former.


So I'll repeat my query...what's the rush?

[A.DIM]

...
Right about the latter, but not the former.

That abstract doesn't describe a life detection experiment, RAF. There is no such experiment on MSL.

From the Mission Overview: Mars Science Laboratory will study Mars' habitability

To find out, the rover will carry the biggest, most advanced suite of instruments for scientific studies ever sent to the martian surface. The rover will analyze dozens of samples scooped from the soil and drilled from rocks. The record of the planet's climate and geology is essentially "written in the rocks and soil" -- in their formation, structure, and chemical composition. The rover's onboard laboratory will study rocks, soils, and the local geologic setting in order to detect chemical building blocks of life (e.g., forms of carbon) on Mars and will assess what the martian environment was like in the past.

So I'll repeat my query...what's the rush?

Eh? What "rush" are you talking about? Obviously there hasn't been any rush to confirm the Viking LR results; MSL won't do it either.

[R.A.F.]

From the Mission Overview: [i]Mars Science Laboratory will study Mars' habitability.

From that same link...

Mars Science Laboratory is a rover that will assess whether Mars ever was, or is still today, an environment able to support microbial life. In other words, its mission is to determine the planet's "habitability."

"If" they determine that it isn't an environment that could support life, then it won't matter what Levin thinks.

What "rush" are you talking about?

The rush to find life....if it is there (or elsewhere), it's not going anywhere...so why place such "importance" on 35 year old disputed findings?

Obviously there hasn't been any rush to confirm the Viking LR results...

Because there are problems with the interpretation that the LR experiment indicated life...and the fact that the LR experiment scientist disputes those problems makes me real leery about his motives for wanting a "re do".

This just looks like a prime example of "conflict of interest".


Anyway...that's all I have to say on the subject...cheers..

[A.DIM]

As I said, there has been no life detection experiment since Viking; there's been no "rush" to find life on Mars.

But there is good reason to revisit the LR results, considering what we've learned about Mars' environments and extremophile life.
We already know some extremophiles could survive the conditions on Mars.
Why do you suppose they're only investigating "habitability" rather than something like a chiral LR experiment, something designed specifically to test for life?

[Substantia Innominata]

Why do you suppose they're only investigating "habitability" rather than something like a chiral LR experiment, something designed specifically to test for life?

Okay, question wasn't directed at me, but R.A.F. may have backed out and here's just one more opinion anyway. What R.A.F. probably was hinting at--I think, rightly so--is that the MSL in this matter rather intends to kill two birds with one stone.. so to speak. Since if an investigation of Mars' habitability, whether present or past, proves negative: What kind of life (or even just its traces) would you still expect to be possible there and nonetheless? Perhaps excluding extremophiles for the moment: Is not the crucial, fundamental question of habitability the very basis clearly necessary for any life (at least as we know it) to enter the scene in the first place? Unfortunately there's a rub with this 'at least as we know..' too, because I just cannot see how exactly you'd go about when it comes to the detection of potential life so odd, that it wouldn't even be reliant on, and hence fit into, a/the concept of habitability as we currently understand it.

You also mentioned extremophiles. A case that is somewhat different and, to my mind, really falls outside that entire habitability-affair, for the obvious reason of their habitability-zone apparently hardly determined, or determinable, by anything. Something of that sort you might just find about anywhere.. and do you see the problem now? Some kind of extremophilic organism may (for instance!) thrive a whole kilometer underneath the Martian surface. Surely I wouldn't deny the mere possibility. Only, you will hardly ever be capable of finding it there. Hopeless. So, why not just begin with the basics instead? Habitability is as basic as it gets, and as I understand this really is all MSL can accomplish and is intended for with respect to astrobiological questions. Not a bad thing at all in my eyes, if nothing else because in this way we at least know what we're looking for, and that is something clearly definable at the outset: present or past habitability. Only from there can you go further. Or, not?

[Colin Robinson]

As I said, there has been no life detection experiment since Viking; there's been no "rush" to find life on Mars.

But there is good reason to revisit the LR results, considering what we've learned about Mars' environments and extremophile life.
We already know some extremophiles could survive the conditions on Mars.

Do we know this? And by "survive", do you mean "survive in a dormant state" or do you mean "grow, reproduce and maintain a population"?

Why do you suppose they're only investigating "habitability" rather than something like a chiral LR experiment, something designed specifically to test for life?

Interesting point.

A refinement of the LR experiment (e.g a chiral version) might, conceivably, resolve the debate about the Viking results and about life on Mars.

Then again, it might not...

One problem with Viking-type experiments to test directly for life is this...

* If you get a clear positive result, then you've won the jackpot...
* BUT if the result is negative or ambiguous, what do you have?

A negative (or not clearly positive) result is consistent with the hypothesis that Mars has no life on it, and never did have any; but equally consistent with the hypothesis that Mars used to have life, but now does not; equally consistent with the hypothesis that life on Mars exists today in a few favored regions, and you tested in the wrong place.

The alternative -- first trying to establish past and present habitability -- may not offer the chance of a quick jackpot win. But whatever results you get, it will help to establish directions for future research: e.g. where (if anywhere) tests for living organisms are most likely to be fruitful, where (if anywhere) a search for past life is most likely to produce results...

[Colin Robinson]

You also mentioned extremophiles. A case that is somewhat different and, to my mind, really falls outside that entire habitability-affair, for the obvious reason of their habitability-zone apparently hardly determined, or determinable, by anything.

Extremophiles do have limits, actually. For instance, they can live in springs of very hot, pressurized water, or in water too salty for other organisms; nonetheless they do need liquid water in some form to grow and reproduce. That is one reason there is so much interest in whether liquid water ever occurs on Mars, and in whether it has existed there in the past.

Is not the crucial, fundamental question of habitability the very basis clearly necessary for any life (at least as we know it) to enter the scene in the first place? Unfortunately there's a rub with this 'at least as we know..' too, because I just cannot see how exactly you'd go about when it comes to the detection of potential life so odd, that it wouldn't even be reliant on, and hence fit into, a/the concept of habitability as we currently understand it.

It is possible to discuss possible habitats for quite different forms of life, on the basis of known principles of chemistry and physics, and a definition of life, e.g. as "a chemical system capable of Darwinian evolution".

On that basis, it is possible, for instance to conceive of a life-form which does its chemistry using a liquid other than water as the solvent: e.g. ammonia, or sulfuric acid. However, it is difficult to conceive of such a chemical system with no solvent at all. This issues were discussed a few years ago by a committee of the American National Research Council in the publication The Limits of Organic Life in Planetary Systems, which is accessible without charge online.

[Van Rijn]

G. Levin recently published this paper in the notorious Journal of Cosmology.

Quite notorious - he might as well be publishing in the National Enquirer. No thanks.

To me it sounds as if he's merely requesting a renewed analysis of the Viking LR results.

What is left to reexamine? My understanding is that the data has been examined to the extent that it was possible. What will change by doing it again?

[Van Rijn]

A refinement of the LR experiment (e.g a chiral version) might, conceivably, resolve the debate about the Viking results and about life on Mars.

Then again, it might not...

One problem with Viking-type experiments to test directly for life is this...

* If you get a clear positive result, then you've won the jackpot...
* BUT if the result is negative or ambiguous, what do you have?

Right, so to spend the resources to send a new, specific experiment you want to be pretty sure you'll win the bet. You don't want a repeat of Viking, with decades of "well maybes" even if it fails per the conditions established for the experiment. (My recollection was that there were conditions set for the evaluation of the Viking results specifically to keep it objective, to avoid the trap of reading into the results what we would like to believe - but that happens anyway.)

[A.DIM]

Okay, question wasn't directed at me, but R.A.F. may have backed out and here's just one more opinion anyway. What R.A.F. probably was hinting at--I think, rightly so--is that the MSL in this matter rather intends to kill two birds with one stone.. so to speak. Since if an investigation of Mars' habitability, whether present or past, proves negative: What kind of life (or even just its traces) would you still expect to be possible there and nonetheless? Perhaps excluding extremophiles for the moment: Is not the crucial, fundamental question of habitability the very basis clearly necessary for any life (at least as we know it) to enter the scene in the first place? Unfortunately there's a rub with this 'at least as we know..' too, because I just cannot see how exactly you'd go about when it comes to the detection of potential life so odd, that it wouldn't even be reliant on, and hence fit into, a/the concept of habitability as we currently understand it.

You also mentioned extremophiles. A case that is somewhat different and, to my mind, really falls outside that entire habitability-affair, for the obvious reason of their habitability-zone apparently hardly determined, or determinable, by anything. Something of that sort you might just find about anywhere.. and do you see the problem now? Some kind of extremophilic organism may (for instance!) thrive a whole kilometer underneath the Martian surface. Surely I wouldn't deny the mere possibility. Only, you will hardly ever be capable of finding it there. Hopeless. So, why not just begin with the basics instead? Habitability is as basic as it gets, and as I understand this really is all MSL can accomplish and is intended for with respect to astrobiological questions. Not a bad thing at all in my eyes, if nothing else because in this way we at least know what we're looking for, and that is something clearly definable at the outset: present or past habitability. Only from there can you go further. Or, not?

Please don't misunderstand; I’m not saying what the MSL is designed to accomplish is a bad thing in any way, I’m simply pointing out that there’s been no real follow up on the Viking LR results. What follow up there has been, IIRC, has instead strengthened the biogenic position.
And “the rub” as I see it, is that had we known then what we know now about Mars’ climate, its water, methane etc. coupled with our understanding of the hardiness of extremophiles, results like the LR would likely be taken as clear indicators of extant life. Thus there’d be a concerted effort to test for certain on follow up missions.

[A.DIM]

Do we know this? And by "survive", do you mean "survive in a dormant state" or do you mean "grow, reproduce and maintain a population"?

I suppose we don’t really know this because our understanding is based on what we think are analogs for Mars soils and environments, and the extremophiles which survive them (eg. Antarctica, Atacama, articifical). There’s a good bit in the literature which deals with this.

Interesting point.

A refinement of the LR experiment (e.g a chiral version) might, conceivably, resolve the debate about the Viking results and about life on Mars.

Then again, it might not...

One problem with Viking-type experiments to test directly for life is this...

* If you get a clear positive result, then you've won the jackpot...
* BUT if the result is negative or ambiguous, what do you have?

A negative (or not clearly positive) result is consistent with the hypothesis that Mars has no life on it, and never did have any; but equally consistent with the hypothesis that Mars used to have life, but now does not; equally consistent with the hypothesis that life on Mars exists today in a few favored regions, and you tested in the wrong place.

The alternative -- first trying to establish past and present habitability -- may not offer the chance of a quick jackpot win. But whatever results you get, it will help to establish directions for future research: e.g. where (if anywhere) tests for living organisms are most likely to be fruitful, where (if anywhere) a search for past life is most likely to produce results...

I can understand the cautious reasoning, to a degree, but I think we could devise an experiment which would give unambiguous results, either falsifying the Viking LR results or confirming them.

[A.DIM]

Extremophiles do have limits, actually. For instance, they can live in springs of very hot, pressurized water, or in water too salty for other organisms; nonetheless they do need liquid water in some form to grow and reproduce. That is one reason there is so much interest in whether liquid water ever occurs on Mars, and in whether it has existed there in the past.

It is possible to discuss possible habitats for quite different forms of life, on the basis of known principles of chemistry and physics, and a definition of life, e.g. as "a chemical system capable of Darwinian evolution".

On that basis, it is possible, for instance to conceive of a life-form which does its chemistry using a liquid other than water as the solvent: e.g. ammonia, or sulfuric acid. However, it is difficult to conceive of such a chemical system with no solvent at all. This issues were discussed a few years ago by a committee of the American National Research Council in the publication The Limits of Organic Life in Planetary Systems, which is accessible without charge online.

Thanks for that. I'll check it out.
Here's another paper you might find interesting: A Possible Biogenic Origin for Hydrogen Peroxide on Mars: the Viking Results Reinterpreted (although this only gives the abstract).

And then there was this: The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results which says this particular experiment could've been blind to low levels of organics and lessens the preference for a chemcial interpretation of the results.

[Van Rijn]

And “the rub” as I see it, is that had we known then what we know now about Mars’ climate, its water, methane etc. coupled with our understanding of the hardiness of extremophiles, results like the LR would likely be taken as clear indicators of extant life.

No. The results were not clear indicators of extant life. What we know now about the Martian climate, the water, etc. has no bearing on the results of the experiment.

[A.DIM]

No. The results were not clear indicators of extant life. What we know now about the Martian climate, the water, etc. has no bearing on the results of the experiment.

I disagree.
The “Wolf Trap” life detection experiment was left off Viking, due to funding, but also because it assumed the presence of water, which at the time was considered unlikely. We now think otherwise. I wonder what results we might’ve seen had it flown to Mars.
Along with this we now know the GCMS, which served as arbiter for the experiments, would not have detected organic activity to begin with (it was not sensitive enough, or it killed it), and so the preference for a chemical explanation for the LR and PR results is barely on equal footing with a biological explanation.
Did you know that three years before Viking flew, Horowitz (a principle investigator with the Pyrolytic Release experiment) published a paper proclaiming, after 5 years in the Dry Valleys of Antarctica looking for microbes, that it was the “only truly sterile soil on Earth?” We now know otherwise but curiously, it was Wolf Vishniac (the “wolf trap” scientist) who discovered microbial life in the Dry Valleys. This was before Viking flew yet for some reason Vishniac’s experiment was deemed less likely to find evidence of life than Horowitz’s PR.
In my opinion, if we knew then what we know now, the assumptions about life on Mars would’ve been different, and the Viking results could’ve just as likely been taken as signs of extant life.

[Van Rijn]

I disagree.

That's not being objective. The results of the LR experiment don't change just because you'd like them to.

The “Wolf Trap” life detection experiment was left off Viking, due to funding, but also because it assumed the presence of water, which at the time was considered unlikely. We now think otherwise. I wonder what results we might’ve seen had it flown to Mars.

What do such hypotheticals have to do with the actual, real-world LR experiment results?

In my opinion, if we knew then what we know now, the assumptions about life on Mars would’ve been different, and the Viking results could’ve just as likely been taken as signs of extant life.

With what we know now, the results remain inconclusive. There simply isn't enough information available from the LR experiment to determine whether or not the results were due to life.

[A.DIM]

That's not being objective. The results of the LR experiment don't change just because you'd like them to.

Objectively, and without invoking some exotic chemistry, the LR results indicate organic activity, (some PR results too); I wouldn’t change anything. Take into account the GCMS results and the subjective preference for an unknown chemistry arises. Is NASA even looking for the oxidant on Mars which would satisfy the preference for a chemical interpretation of the LR results?

What do such hypotheticals have to do with the actual, real-world LR experiment results?

The point was that assumptions we make about Mars dictate how we go about exploring. Assume no water (even while frost was found at both Viking sites) and don't send an experiment which involves it.

But I might ask the same thing about hypotheticals: Why hypothesize some unknown chemistry when there are indicators of organic activity?

With what we know now, the results remain inconclusive. There simply isn't enough information available from the LR experiment to determine whether or not the results were due to life.

And yet there’s been no attempt at reconciling them, has there? With what we know now, an organic explanation is just as likely yet the preference for some unknown chemistry is the “official” position. To objectively consider the LR results would be to design an experiment specifically to test against them, on Mars, and or design an experiment which could identify the powerful oxidant needed to satisfy a chemical explanation.

[Van Rijn]

Objectively, and without invoking some exotic chemistry, the LR results indicate organic activity, (some PR results too); I wouldn’t change anything.

There is indication of organic (carbon based) chemistry, but there isn't enough information to say whether the cause is life or a non-life chemical process.

But I might ask the same thing about hypotheticals: Why hypothesize some unknown chemistry when there are indicators of organic activity?

And this, A.DIM, is a great example of why I think people here get frustrated trying to talk with you.

The discussion was about the LR results. I pointed out that the LR results haven't changed. Out of left field you brought up a hypothetical question, what if we'd sent another experiment, having nothing to do with the LR experiment? My question was, and still is:

What do such hypotheticals have to do with the actual, real-world LR experiment results?


Look: The LR results are what they are. If there is life on Mars, we'll learn it through future experiments, not endless repeats of discussions about an experiment that simply doesn't give enough information to decide between "chemistry" or "life."

To objectively consider the LR results would be to design an experiment specifically to test against them, on Mars, and or design an experiment which could identify the powerful oxidant needed to satisfy a chemical explanation.

Those would be new experiments, not reexamination of the LR results.

[Colin Robinson]

Objectively, and without invoking some exotic chemistry, the LR results indicate organic activity, (some PR results too); I wouldn’t change anything. Take into account the GCMS results and the subjective preference for an unknown chemistry arises. Is NASA even looking for the oxidant on Mars which would satisfy the preference for a chemical interpretation of the LR results?

Since Viking, NASA has found a powerful oxidant on Mars -- perchlorate salts.

This has lead to a reassessment of the GCMS test for organic compounds (carbon chain compounds) -- a NASA study last year showed that the way the GMCS worked, the perchlorate would have turned organics in a substance very like cleaning fluid when the sample was processed. And traces of "cleaning fluid" were indeed noticed in Viking's GCMS results.

I don't know whether perchlorate chemistry fully explains the rest of the Viking results or not. But it's certainly a factor to consider...

[iquestor]

I agree the LR Results are inconclusive. They were not definately positive or negative when taken as a whole.

however why not make a chiral version of the LR Test? If the reactions showed that a chiral preference existed then that would seem to be to be very strongly indicative of the life explanation, and rule out the chemical one.

I understand about determining habitability, and logical progression, but I really don't get why MSL didnt include any direct method of finding life other than if the cameras pick up an approaching polar bear or fossil embedded in a cliff. How much would a chiral version of LR be anyway? Is this a political thing at NASA???

[Githyanki]

He released this paper at this time for political-reasons; he wants to get the scientific community more interested in finding life on Mars.

After Viking's tests' were negative or inconclusive, I think the majority of the scientific community, upon learning just how barren Mars is who grew up reading science-fiction of a lush Mars, gave up hope and concluded no life is there. Now, with greater understanding of extremephiles, life is once again possible on Mars.

[A.DIM]

There is indication of organic (carbon based) chemistry, but there isn't enough information to say whether the cause is life or a non-life chemical process.

This is exactly why there should’ve been a mission designed to resolve the question, no? LR results were positive for organic activity. Favoring a chemical interpretation you have some unknown chemistry involved. Both are good reason for focused research.

And this, A.DIM, is a great example of why I think people here get frustrated trying to talk with you.

The discussion was about the LR results. I pointed out that the LR results haven't changed. Out of left field you brought up a hypothetical question, what if we'd sent another experiment, having nothing to do with the LR experiment? My question was, and still is:

What do such hypotheticals have to do with the actual, real-world LR experiment results?

Look: The LR results are what they are. If there is life on Mars, we'll learn it through future experiments, not endless repeats of discussions about an experiment that simply doesn't give enough information to decide between "chemistry" or "life."

Those would be new experiments, not reexamination of the LR results.

Sorry to frustrate you Van Rijn, but I understand. I feel much the same way when people would preferentially hypothesize some unknown chemistry instead.

But to answer your question: nothing, the results stand on their own, which indicate organic activity.

Look, it’s necessary to revisit and reexamine (have endless repeats of discussions about) the LR results. They were the only life detection experiment ever sent to Mars, and considering how our thinking has changed about Mars’ habitability, the LR results should be front and center in determining future experiments and missions.
Likely the MSL will further our understanding, although I fear that if results indicate organics that still won't be enough to keep skeptics from hypothesizing unknown or exotic chemistries as "simpler" explanations.

[A.DIM]

Since Viking, NASA has found a powerful oxidant on Mars -- perchlorate salts.

This has lead to a reassessment of the GCMS test for organic compounds (carbon chain compounds) -- a NASA study last year showed that the way the GMCS worked, the perchlorate would have turned organics in a substance very like cleaning fluid when the sample was processed. And traces of "cleaning fluid" were indeed noticed in Viking's GCMS results.

I don't know whether perchlorate chemistry fully explains the rest of the Viking results or not. But it's certainly a factor to consider...

Indeed.
Here's a paper which discusses the perchlorate findings: Organics on Mars?

Abstract:
Organics are expected to exist on Mars based on meteorite infall, in situ production, and any possible biological
sources. Yet they have not been detected on the martian surface; are they there, or are we not capable enough to
detect them? The Viking gas chromatograph–mass spectrometer did not detect organics in the headspace of
heated soil samples with a detection limit of parts per billion. This null result strongly influenced the interpretation
of the reactivity seen in the Viking biology experiments and led to the conclusion that life was not
present and, instead, that there was some chemical reactivity in the soil. The detection of perchlorates in the
martian soil by instruments on the Phoenix lander and the reports of methane in the martian atmosphere suggest
that it may be time to reconsider the question of organics. The high-temperature oxidizing properties of perchlorate
will promote combustion of organics in pyrolytic experiments and may have affected the ability of both
Phoenix’s organic analysis experiment and the Viking mass spectrometer experiments to detect organics. So the
question of organics on Mars remains open. A primary focus of the upcoming Mars Science Laboratory will be
the detection and identification of organic molecules by means of thermal volatilization, followed by gas
chromatography–mass spectrometry—as was done on Viking. However, to enhance organic detectability, some
of the samples will be processed with liquid derivatization agents that will dissolve organics from the soil before
pyrolysis, which may separate them from the soil perchlorates. Nonetheless, the problem of organics on Mars is
not solved, and for future missions other organic detection techniques should therefore be considered as well.

[A.DIM]

He released this paper at this time for political-reasons; he wants to get the scientific community more interested in finding life on Mars.

After Viking's tests' were negative or inconclusive, I think the majority of the scientific community, upon learning just how barren Mars is who grew up reading science-fiction of a lush Mars, gave up hope and concluded no life is there. Now, with greater understanding of extremephiles, life is once again possible on Mars.

“At this time for political reasons” - what "time" and to what end?
I mean, the explosive growth of astrobiology in the last ten years would indicate there’s already extreme interest in finding life on Mars (and elsewhere in the system).

[Colin Robinson]

Indeed.
Here's a paper which discusses the perchlorate findings: Organics on Mars?

The interesting paper you've quoted is largely about how perchlorate may have affected Vikings GCMS test for organics, and may affect other tests for organics in the future: certainly an important issue!

On the other hand, it is possible that highly oxidizing substances related to perchlorate were responsible for the results of Levin's LR experiment and for the release of oxygen in another of the Viking experiments.

I've just been looking at a paper about Martian soil perchlorates from the 42nd Lunar and Planetary Science Conference (2011).

Our experiments indicate that on
Mars ionizing radiation will decompose soil perchlo-
rates to form reactive oxyhalide and oxygen species.
These species likely play a role in the alteration of soil
organics in situ and are likely responsible for the re-
lease of O2 in the Viking GEx experiment and the de-
composition of organics in the Viking LR experiment.

[archibald]

Could the Wolf Trap have detected extremophiles on Mars ? What consequences ?
The more I look through it, the more the twin tragedies - loss of Wol Trap, loss of Vishniac himself - seems to have affected the program.

[kamaz]

There is a new paper reanalizing the LR data and claiming that it indeed detected life: http://news.discovery.com/space/mars...mkcpgn=rssnws1

The paper itself (PDF): http://ijass.org/On_line/admin/files...026)11-030.pdf

[Selfsim]

There is a new paper reanalizing the LR data and claiming that it indeed detected life: http://news.discovery.com/space/mars...mkcpgn=rssnws1

The paper itself (PDF): http://ijass.org/On_line/admin/files...026)11-030.pdf

Hi kamaz ! Thanks for the 'heads-up' !

So AIUI, some clever complexity-based statistical analysis has been applied to the original Viking LR data, in order to see whether the original data displays the same statistical characteristics, as a modern-day terrestrial control sample.

The results ? ..

the cluster analysis indicated that the active LR experiments were more similar to the terrestrial biological time series and the control LR experiments were more similar to the non-biological terrestrial time series.

In mathematical terms, the Euclidean distance between the centroids of the two clusters was significantly larger than the intra-cluster distances between any members of either cluster. It is reasonable to infer from this analysis that the Martian active LR experiments were more likely detecting a biological process, whereas the Martian control LR experiments were more likely detecting a non-biological process.

Thus, we have shown that complexity variables distinguish active LR experiments (Martian and terrestrial samples) from control LR experiments.

They finally conclude:

We believe that these results provide considerable support for the conclusion that the Viking LR experiments did, indeed, detect extant microbial life on Mars.

Lots of weasel words there (see underlines).

So, my question which remains is: "Well, so what now ?"
I also note the key phrase: "reasonable to infer" ...
Where does inference take us in the present day, on test data obtained in 1976?

This paper seems to me, to be pointing out a new way to analyse test data for microbial life, rather than saying anything about the presence, or absence, of microbial life on Mars. So, I would've expected extensive demonstrations of its successul application on terrestrial samples, here on Earth, in order to demonstrate its effectiveness and precision. But, alas, this doesn't seem to be what they've done !

Overall, I think I'm more interested to see what MSL/Curiosity has to say about the Gale crater environment ...

Regards