[X] My Assistant

[dvandorn]

As I recall, the ambiguous results of the Viking landers' life detection experiments were explained at the time by postulating that the surface soils are highly enriched with extremely oxidized clays (I seem to recall descriptions of clays enriched with peroxides).

Nearly identical results were seen at both V1 and V2 sites, so, assuming that the results are explained by what was called "exotic soil chemistry," this chemistry would have to be widespread on Mars.

We now have some very good elemental analyses of the Martian soils, both from orbit and ground-truth from the MER rovers. In these analyses, clays seem not at all widespread, only appearing in very, very old outcrops that were presumably laid down during a very short geological timeframe during which non-acidic water was common on the Martian surface.

Soils in the Viking landing sites would appear, from the more advanced sensors we've flown since Viking, to be basaltic with admixtures of ferrous sulphates. Not exactly the exotic chemistry required to explain the Viking results.

So, the million-dollar question seems to be: if the Viking experiments can only be explained by *either* biotic processes that do not involve what we always considered the pre-requisite organic molecules, *or* by ubiquitous exotic chemistry in the soils that we're simply not seeing with more advanced instruments, which theory are we forced to accept as fact?

If neither, then what theory *does* account for the Viking results?

-the other Doug

[mcaplinger]

We now have some very good elemental analyses of the Martian soils, both from orbit and ground-truth from the MER rovers.

No, we don't. We have some really crude elemental abundances from orbit and some slightly better ones from the ground. But I don't think elemental abundances tell you much if anything about either clays or peroxides, you need instruments that can look at molecular properties, not just elemental abundances. Phoenix is the first mission that will be able to do that, and then MSL.

[ElkGroveDan]

So, the million-dollar question seems to be: if the Viking experiments can only be explained by *either* biotic processes that do not involve what we always considered the pre-requisite organic molecules, *or* by ubiquitous exotic chemistry in the soils that we're simply not seeing with more advanced instruments, which theory are we forced to accept as fact?

If neither, then what theory *does* account for the Viking results?

-the other Doug

Good question.

No, we don't. We have some really crude elemental abundances from orbit and some slightly better ones from the ground. But I don't think elemental abundances tell you much if anything about either clays or peroxides, you need instruments that can look at molecular properties, not just elemental abundances. Phoenix is the first mission that will be able to do that, and then MSL.

Good answer.

Wouldn't it be true though that firm knowledge of even just the elemental abundances would narrow the infinite possibilities of possible reactions that we were facing at the time of Viking?

[Guest_BruceMoomaw_*]

Not really -- the main element involved is oxygen, in combination with either hydrogen or a wide variety of metals already known to exist in Martian minerals. (That's not counting Albert Yen's alternate theory, which simply calls for unusually shaped and electrically charged microscopic surfaces on ordinary Martian mineral crystals.) Nailing down the Oxidant Mystery is likely to be the major contribution of Phoenix's wet chemistry experiment.

[Guest_paulanderson_*]

I would note also that some in the anti-life camp still use the lack of organics found by Viking as an argument, despite the fact that it was later shown that the detector used on Viking was not able to verify the smaller traces of organics in testing done in the Antarctic (I think that's where it was done), which were in the soil and confirmed by better instruments. If similar trace amounts of organics had been in the Martian soil, Viking could or would have easily missed them completely.

I've also seen other later papers which now dispute the idea that the Martian soil is so highly oxidizing, yet that is also still used as a primary anti-life argument and has been widely accepted as fact, but again there is no real firm consensus or agreement on that.

[Guest_BruceMoomaw_*]

There are certainly SOME major oxidants in the soil -- the fact that Mars' soil retained much of its oxidizing power even after being roasted at several hundred degrees proves that. Any germs capable of withstanding that must hail from the planet Krypton. This, in turn, makes it a suspicious coincidence that the results from the Labeled Release experiment could be due to actual germs living in the same highly oxidizing environment -- and more likely that the LR results are just from another type of nonliving oxidant which does break down under heating.

In this connection, the new LPSC had an abstract connected with the recent studies of the very powerful (and bacteria-destroying) oxidants which have been discovered in the Atacama Desert's soil, produced by regular Earth sunshine: http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1778.pdf . It claims that "hydrogen peroxide together with hematite reproduces the kinetics of the LR experiment", and indeed the reaction does follow the time curve of the Viking results very closely -- but the study didn't test whether this reaction ceases when the soil is heated. (There are a number of LPSC abstracts dealing with Atacama soil, and I haven't yet read all of them -- I'll see whether any of them mentions temperature-dependent effects.)

[Guest_BruceMoomaw_*]

Well, there are no LPSC abstracts this year dealing with the thermally "labile" (unstable) oxidant suggested by the Viking LR experiment, although there are four other interesting papers dealing with the overall question of the surface destruction of Martian organics: # 2098, 2162, 2262 and 2397.

[JRehling]

Wouldn't it be true though that firm knowledge of even just the elemental abundances would narrow the infinite possibilities of possible reactions that we were facing at the time of Viking?

I'll add to Mike's and Bruce's answers by drawing an analogy: Knowing the elemental abundances when you're wondering about the chemistry is a little like knowing how many As, Bs, Cs, etc., are in a paragraph when you're wondering what the paragraph means. The way you put the little parts together matters -- a LOT.

[edstrick]

Plausible post-Viking studies interpreted the weathered component of the soils as being dominated by "palagonite", which is a mineraloid -- not a mineral -- derived by hydration and weathering of volcanic glass, without well defined mineral content or well-crystalized phases. This goes with the lack of well defined oxide or oxy-hydroxide mineral spectral signatures for a lot of the reddish iron color in the global dust and reddish soils. Added to these dust coponents in the soils were assumed to be basaltic and related sand minerals, sulfates and other water soluble salts and oxidizing compounds, possibly metal peroxides.

One thing Gil Levin doesn't seem to want to talk about much is the glaring LACK of one finding from his experiment. While he found a sterlization-destroyable release of carbon-bearing gas from his radioactive "soup", the reactions were "one-shot" events that happened immediately upon addition of the soup, and there was no growth signature, no delay and increase in gas output whatever. This behaviour is consistent with a rapidly reacting chemical in the sample and not growing organisms. Abundant metabolizing organisms that progressively die off is consistant with the observations, but I don't know to what extent he modeled the plausible biomass required for the prompt gas evolution rates.

[djellison]

And to add to this - the APXS's on MER can't detect hydrogen, and if your trying to find peroxides........

To carry on JR's analogy - It's like knowing how many of every letter EXCEPT E there are in a paragraph, and wondering what it means.

Doug

[chris]

And to add to this - the APXS's on MER can't detect hydrogen, and if your trying to find peroxides........

To carry on JR's analogy - It's like knowing how many of every letter EXCEPT E there are in a paragraph, and wondering what it means.

Doug

To put Doug's post another way:

T:17 N:17 A:17 R:15 O:15 I:11 D:11 Y:7 S:7 H:7 G:7 P:5 W:4 C:4 X:3 M:3 L:3 F:3 U:2 K:2 V:1 J:1

Chris

[ljk4-1]

Silly Question of the Day: When they designed Viking to look for
life on the Martian surface, why didn't they include instruments to
fully analyze the materials to separate and detect the inorganic
elements?

Didn't they want to know what the Martian surface was made of
outside of the life issue? I am still amazed at how much of the
results were left to guesswork.

[Guest_BruceMoomaw_*]

Actually, the one instrument for inorganic analysis of the surface -- the X-ray spectrometer -- was itself a last-minute addition to the payload, put on only in 1971 after a growing number of scientists raised a stink about the lack of any such instrument whatsoever. Viking was explicitly designed as a biological mission, becuase that was by far the highest-priority scientific question about it -- and it was assumed at the time that more Mars missions would soon follow to do other research. (Which, of course, they would have done had the Shuttle not eaten up all the space-science funding in the 1980s.)

[The Messenger]

Actually, the one instrument for inorganic analysis of the surface -- the X-ray spectrometer -- was itself a last-minute addition to the payload, put on only in 1971 after a growing number of scientists raised a stink about the lack of any such instrument whatsoever. Viking was explicitly designed as a biological mission, becuase that was by far the highest-priority scientific question about it -- and it was assumed at the time that more Mars missions would soon follow to do other research. (Which, of course, they would have done had the Shuttle not eaten up all the space-science funding in the 1980s.)

Without the inertial of the shuttle, would there have been any funding for any space programs in the 1980's? The Reagan White House operated with a slash-and-burn mentality.

[Guest_BruceMoomaw_*]

This brings us back yet again to that interminable debate: if the manned program (in this case the Shuttle) was removed, would the total funding for the unmanned program increase or decrease? I still see absolutely no logical argument that it would have decreased. The Space Pork Congressmen, without a manned program to supply their districts with that pork, would have supported a compensatory bigger unmanned program; and the public seems quite interested in some spects of unmanned space exploration -- what they want to see is something new and interesting, and they don't much care whether it's Buzz Lightyear or Robbie the Robot holding the camera. TOTAL space spending would certainly have decreased (explaining by itself NASA's frantic support for Shuttle and Station by any means necessary, up to and including regularly committing perjury before Congress), but that's an entirely different matter.

As for the Reagan Administration having a "slash and burn" mentality: if they really had had one, they wouldn't have inflated the budget deficit to the size of the Crab Nebula. David Stockman -- the one member of the Administration who seriously favored zapping the hell out of the unmanned space program -- later wrote a bitter book on how Reagan had deceived him by falsely saying that he DID favor big spending cuts.