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Abiotic Ch4 On Mars Via A Photoreductive Process, and photoreductive generation of ammonia
silylene
post Nov 13 2005, 01:07 AM
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I thought this would be an interesting discussion subject, and appropriate for this fora given the renewed interest into possible sources of trace levels of methane (and ammonia) in the Martian atmosphere.

Part 1: Photoreductive generation of methane over metal oxide dusts
I want to repost a hypothesis which I think deserves serious consideration, and one which has not been published in the scientific literature yet. I first proposed this hypothesis on 7/19/2004 here: http://uplink.space.com/showthreaded.php?C...posts&Main=5980

Hopefully one day my job will give me the time to pursue some research in this area. Unfortunately, I don't see that happening in the next few years since I now hold a high position in research management, and am no longer a research fellow. Perhaps if someone reading this fora has the time to pursue this research direction, and they would include me as a coauthor. I would be happy to collaborate (I am a chemist, and have published papers involving photochemical mechanisms and applications.)

I first point out that the hard UV light is not filtered out of the Martian atmosphere by ozone. With this is mind, let's keep grounded by the fact that CO2 can be photoreduced to CH4 on suitable catalysts, such as metal oxides (which are common in the Martian soils). Dusts suspended inn the atmosphere and surface soils composed of metal oxides such as TiO2 and ZrO2 are examples of useful catalysts for the proposed photoreductive processes. With really DUV light (F2 laser = 157 nm), no catalysts are required.

I next note that the regions of Mars with the highest concentrations of methane in the atmosphere are the equitorial areas. If the mechanism of the formation of methane is a photoreductive process, this is exactly where you'd expect to find methane - over the surface areas with the highest leves of insolation.

I think we should pursue more research on abiotic generation of methane, specifically photoreductive processes. If we fully understand this area, we will also understand the limitations of whether abiotic methane chemistry is possible in the Martian environment.

Here are a few abstracts from the chemical literature on the photoreduction of CO2 to make methane:

vacuum-UV laser photolysis of CO2 systems. Nakashima, N.; Ojima, Y.; Kojima, M.; Izawa, Y.; Yamanaka, C.; Akano, T. Institute Laser Engineering, Osaka University, Suita, Japan. Energy Conversion and Management (1995), 36(6-9), 673-6. CODEN: ECMADL ISSN: 0196-8904. Journal written in English. CAN 123:270397 AN 1995:727451 CAPLUS

Abstract

Gaseous CO2 was photoreduced on irradn. with a vacuum-UV F2 laser (158 nm). The final products were formaldehyde, methane etc. for the case of a mixt. with hydrogen, and alc. for systems of hydrofluorocarbons.

+++++++++

Photoreduction of carbon dioxide and water into formaldehyde and methanol on semiconductor materials. Aurian-Blajeni, B.; Halmann, M.; Manassen, J. Weizmann Inst. Sci., Rehovot, Israel. Solar Energy (1980), 25(2), 165-70. CODEN: SRENA4 ISSN: 0038-092X. Journal written in English. CAN 94:124490 AN 1981:124490 CAPLUS

Abstract

Heterogeneous photoassisted redn. of aq. CO2 to produce MeOH [67-56-1], HCHO [50-00-0], and CH4 [74-82-8] was achieved by using semiconductor powders with either high-pressure Hg lamps or sunlight. The reaction was carried out either as a gas-solid process, by passing CO2 and H2O vapor over illuminated semiconductor surfaces or as a liq.-solid reaction, by illuminating aq. suspensions of semiconductor powders through which CO2 was bubbled. Best results, under illumination by Hg lamps, were obtained with aq. suspensions of SrTiO3, WO3, and TiO2, resulting in absorbed energy conversion efficiencies of 6, 5.9, and 1.2%, resp.

++++++++

Reaction mechanism in the photoreduction of CO2 with CH4 over ZrO2. Kohno, Yoshiumi; Tanaka, Tsunehiro; Funabiki, Takuzo; Yoshida, Satohiro. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Japan. Physical Chemistry Chemical Physics (2000), 2(22), 5302-5307. CODEN: PPCPFQ ISSN: 1463-9076. Journal written in English. CAN 134:185804 AN 2000:788525 CAPLUS

Abstract

The surface species produced during photoredn. of carbon dioxide with methane over zirconium oxide were obsd. by IR spectroscopy. One of them was a reaction intermediate and decompd. to CO at .apprx.623 K, and the other did not decompd. even at 673 K was called a carbonaceous residue. IR spectral features allowed to identify the latter as the surface acetate. Several properties of the former species were quite similar to those of the surface formate ion, which was a reaction intermediate in photoredn. of CO2 by H2 over ZrO2. The former species was assigned to the surface formate, which was also supposed to be an intermediate of photoreaction between CO2 and CH4. The existence of another carbonaceous residue different that the surface acetate was suggested. The EPR spectrum indicated the photoexcitation of adsorbed CO2 to the CO2- anion radical, and the interaction of the CO2- radical with CH4 in the dark. On the basis of these results, a possible reaction mechanism in this reaction was proposed.

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I think we should pursue more research on abiotic generation of methane, specifically photoreductive processes. If we fully understand this area, we will also understand the limitations of whether abiotic methane chemistry is possible in the Martian environment.

@@@@@@@@@@@@@@@@@

Part 2: Generation of trace NH3 in the Martian atmosphere via photoreduction from N2

Finally I wish to also point out that there photoreductive processes to produce NH3 from N2. I first posted this hypothesis on 7/15/2004: http://uplink.space.com/showthreaded.php?C...posts&Main=3562

Photoreduction of nitrogen and water on montmorillonite clays loaded with hydrous ferric oxide.
O.A Ileperuma, W.C.B Kiridena and W.D.D.P Dissanayake. J. Photochem. And Photobiol. A: Chem., Vol.59, 1991, 191.

Endoh, E., Bard, AJ. "HETEROGENEOUS PHOTOREDUCTION OF NITROGEN TO AMMONIA ON CATALYST-LOADED
TIO2 POWDERS." New Journal of Chemistry 11 217 - 219, 1987

E. Endoh, JK Leland, AJ Bard, "Heterogeneous Photoreduction of Nitrogen
to Ammonia on Tungsten Oxide," J. Phys. Chem., 90, 6223 (1986).
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deglr6328
post Nov 13 2005, 05:34 AM
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Nice. Occam strikes again. biggrin.gif

It should therefore stand to reason then, that since the highest concentrations of CH4 are seen at the equator (presumably as a result of higher UV flux), then the reaction site for the H2O + CO2 + hv = CH4 is not occuring on water ice frost on the ground (too warm) and it cannot be occurring underground since all UV is blocked within the first cm of the surface, it must be happening predominantly in the thin water ice clouds (which are also plentiful only in the equatorial region) seen seasonally by both rovers. The extremely dusty nature of the atmosphere and the very small size of cirrus cloud ice crystals (mars clouds are said to be "cirrus-like") would provide a phenomenally huge surface area for reactions to take place. How hard would it be to do an investigation involving a correlation between simultaneous cloud cover observations and Planetary Fourier Spectrometer CH4 concentration readings? Not very, I should think. I like this idea a LOT.
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Guest_Myran_*
post Nov 13 2005, 06:54 AM
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QUOTE
deglr6328 said: Nice. Occam strikes again.

Yes I did tell Occam to sharpen the knife the other day, didnt I? tongue.gif

Serious now, yes I have to say that you seem to be onto something here silylene.
Im not a scientist in any which way, but im fully aware of the H2O + CO2 catalyst/cracking => CH4 from the suggestion of a means for providing fuel for a sample return or even a human mission.

In Part 2: You make a reference to "Photoreduction of nitrogen and water on montmorillonite clays"
To my knowledge no clays have been found on Mars as of yet.

But the rest might very well be valid, and no hot subsurface lava needed for the very small levels of methane and possibly for ammonia.
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silylene
post Nov 13 2005, 01:59 PM
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QUOTE (Myran @ Nov 13 2005, 06:54 AM)
In Part 2: You make a reference to "Photoreduction of nitrogen and water on montmorillonite clays"
To my knowledge no clays have been found on Mars as of yet.


Yes, I know. I dno't think wet clays were required.

Anyways, montmorillonite is (Na, Ca)(Al, Mg)6(Si4O10)3(OH)6 - nH2O, a rather typical clay. I think the key to this catalyst is the very fine particle size, and the presence of metal oxides - CaO, Al2O3 or MgO. Those oxides should be common on Mars whether or not they are in a clay.
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Guest_Richard Trigaux_*
post Nov 13 2005, 04:58 PM
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QUOTE (silylene @ Nov 13 2005, 01:59 PM)
Yes, I know.  I dno't think wet clays were required.

Anyways, montmorillonite is (Na, Ca)(Al, Mg)6(Si4O10)3(OH)6 - nH2O, a rather typical clay.  I think the key to this catalyst is the very fine particle size, and the presence of metal oxides - CaO, Al2O3 or MgO.  Those oxides should be common on Mars whether or not they are in a clay.
*


Seems thak clays are remarkably absent of Mars, even in Gussev where Spirit found none. What I think is that it is because the Gussev filling occured into a short catastrophic way, when clay needs a longer time in water to form. I even though it forms by a slow chemical process, for instance when water attacks rocks such as granite, basalt, etc.
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Guest_Richard Trigaux_*
post Nov 13 2005, 05:13 PM
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Hi silylene, I think it is an interesting search. The stake of it is obviously to eventually rule out the formation of methane by a bacteria life in Mars underground water layers. (Recently methane was found and expected to be produced by underground bacteria.)

Searching life on Mars was a really frustrating process, from the beginning where everybody was really optimistic (because of Schaparelli's "channels"). After the channels were found inexistant, hope clung on seasonal colour changes, which could have been formed by lichen-like plants. Now we are to the point of searching life underground, the only place where it still could hide. So we may prepare to the idea that Mars has no life, and that it never had.

But maybe tens of years will be necessary to completelly rule out any underground life. This is important, because of course of the philosophical implications of finding extraterrestrial life, but also because, so long we do not know, we shall have to take drastic precautions against a possible cross-contamination (which could lead to a catastrophe on Earth)

With my opinion the best test we can do about underground life, would be to find some thermal spring, active or recent. If not, we may do with a recent mud flow. We land here, dig deep enough to escape the radiations, and examine samples with a microscope, reactives and all. Eventually this is the best guess for a sample return mission.
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Guest_RGClark_*
post Dec 17 2005, 06:19 PM
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QUOTE (Myran @ Nov 13 2005, 06:54 AM)
Serious now, yes I have to say that you seem to be onto something here silylene.
Im not a scientist in any which way, but im fully aware of the H2O + CO2 catalyst/cracking => CH4 from the suggestion of a means for providing fuel for a sample return or even a human mission.
In Part 2: You make a reference to "Photoreduction of nitrogen and water on montmorillonite clays"
To my knowledge no clays have been found on Mars as of yet.
...
*


Actually clays have been detected by Mars Express:

Where there's clay, there's water
Mars Express instrument discovers evidence of past water on Red Planet.
Bruce Moomaw
December 14, 2005
http://www.astronomy.com/asy/default.aspx?c=a&id=3782

(Nice article Bruce!)

Old rocks the key to life on Mars
By Jonathan Amos
BBC News science reporter, San Francisco
Tuesday, 6 December 2005, 07:02 GMT
"Jean-Pierre Bibring says the instruments on ExoMars should be equipped to look for large carbon molecules in amongst the clays of Marwth Vallis as a possible signature of past life."
http://news.bbc.co.uk/2/hi/science/nature/4502018.stm


And clay has found been in a rock by Spirit in Gusev:

Evidence of Phyllosilicate in Wooly Patch - an Altered Rock
Encountered on the Spirit Rover Traverse [#2327].
Wang A. Haskin L. A. Korotev R. L. Jolliff B. L. de Souza P. A. Jr.
Kusack A. G. Athena Team.
"Rock Wooly Patch on West Spur has several specific physical and
chemical features. Based on our analyses, phyllosilicates of kaolinite,
serpentine, and chlorite types, plus some feldspar and pyroxene are
prime candidates to constitute this rock."
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2327.pdf

Kaolinite is a type of clay.


- Bob Clark
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tty
post Dec 17 2005, 10:25 PM
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Also note that clay minerals are known to facilitate the synthesis of complex organic molecules, though the mechanism is not well understood. The presence of clay minerals on Mars back in the Noachian therefore improves the chance that life could have developed.

tty
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post Dec 18 2005, 03:32 AM
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Thaks for the compliment, R.G. Unfortunately, "Astronomy" eliminated everything I wrote on the MARSIS results (and there WAS some major new news there, which I will be free to report shortly at this site).

Moreover, I'm currently engaged in an exchange with Brian Hynek, who in turn got into quite a lively fight with the MER team at the AGU meeting as to whether the Meridiani deposits really are due to acidified groundwater, or whether their layering structure and chemical makeup has been misinterpreted and they're really repeated falls of volcanic ash mixed with acidified steam. Until I hear a response from him to my latest message, I had better not elaborate right now.

What does seem clear is that the clay deposits are a much better place to look for biological evidence than the sulfate deposits, whether the latter are Noachian or Hesperian (and they seem to have occurred in both eras, suggesting that during the Noachian the degree of acidification of Mars' surface water may have varied greatly from place to place). Indeed, as my article does mention, James Greenwood points out that the very large quantity of phosphorus in Mars' sulfate salts -- thousands of times more, proportionally, than the P/S ratio in Earth's ocean water -- suggests that there was NOT a biota in Mars' acidic water, since the shortage of P in Earth's ocean is almost entirely due to it being removed by organisms. Had we followed John Rehling's icky advice of a little while back and jumped immediately to preparing the first sample-return mission for a Meridiani landing, we would very likely have regretted it later.

One other thing that "Astronomy" cut out of my article, but which is mentioned in one abstract and elaborated on in the talk there: Nili Fossae is a particularly dramatic example of molten olivine being overlaid on top of an older deposit of clays -- the olivine apparently having been dug up and melted by the Isidis impact and then splashed over the older hydrated Noachian terrain. This seems to confirm further what was already indicated by the unmodified olivine deposits that MGS and Odyssey had already seen sprinkled elsewhere across Mars' surface: Mars' days of having any large amounts of non-acid surface liquid water are very, very long gone -- it's been an extremely nasty place, at least on its surface, for at least the last 3.5 billion years, and in fact it seems not to have had even any large amounts of highly acidic water on its surface for the last 3 billion years or so.

http://www.agu.org/cgi-bin/SFgate/SFgate?&...t;P14A-01"
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post Dec 18 2005, 05:53 AM
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QUOTE (RGClark @ Dec 17 2005, 10:19 AM)
Actually clays have been detected by Mars Express:

And also this new one (apparent montmorillonite clays on Husband Hill):

http://www.agu.org/cgi-bin/SFgate/SFgate?&...&=%22P12A-04%22

I had previously linked to reports of the clays being found as well.

This is why the Mars Express findings, combined with Spirit's also in particular now, are so important. I'm glad you are reporting on the phyllosilicates / clays, Bruce, because it still seems a lot of the other science media have left this out of their reports (but hyping the highly acidic sulphates in Meridiani results)...?? It's a shame too that Astronomy magazine cut out so much of your report. Interested in the new MARSIS update you have, also, look forward to it!
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dvandorn
post Dec 18 2005, 06:15 AM
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QUOTE (paulanderson @ Dec 17 2005, 11:53 PM)
...apparent montmorillonite clays on Husband Hill...

http://www.agu.org/cgi-bin/SFgate/SFgate?&...&=%22P12A-04%22
*

Hmmm... perhaps these clays are lacustrine in origin, at least at the Gusev site? Especially if they are derived from a deep underlying layer...

smile.gif

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Guest_BruceMoomaw_*
post Dec 18 2005, 08:37 AM
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That's another puzzle I'm trying to get clarified right now: one thing OMEGA has NOT detected anywhere so far is iron hydroxides, even in small deposits. This may perhaps be because the instrument is less sensitive to them -- after all, most of the West Spur of the Columbia Hills has turned out to be "Clovis"-type rock, which is rich in goethite -- or it may be that there really is less Fe hydroxide left on Mars now than there are phyllosilicates, which might tell us something else important about Mars' history that I don't yet understand.

One thing that must be understood -- and I'm not sure the "Astronomy" article makes it entirely clear, although it mentions it -- is that the evidence from all the SNC meteorites is that the H2SO4 produced on Mars' surface by atmospheric effects apparently did NOT penetrate very deeply underground. The water to which those basalt meteorites have been exposed during their history seems not to have been acidic -- which is why it left significant amounts of carbonates in them. This suggests, again, that if life managed to evolve on Mars' surface during the warmer and wetter but intensely bombarded Noachian, it just might have been able to survive for a much longer period in the deep subsurface liquid-water table. But that is a very big "if": the Noachian wasn't a very friendly time for life itself.
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Guest_RGClark_*
post Dec 18 2005, 06:04 PM
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QUOTE (paulanderson @ Dec 18 2005, 05:53 AM)
And also this new one (apparent montmorillonite clays on Husband Hill):

http://www.agu.org/cgi-bin/SFgate/SFgate?&...&=%22P12A-04%22

I had previously linked to reports of the clays being found as well.

This is why the Mars Express findings, combined with Spirit's also in particular now, are so important. I'm glad you are reporting on the phyllosilicates / clays, Bruce, because it still seems a lot of the other science media have left this out of their reports (but hyping the highly acidic sulphates in Meridiani results)...?? It's a shame too that Astronomy magazine cut out so much of your report. Interested in the new MARSIS update you have, also, look forward to it!
*



Thanks for the link. I hadn't seen that.
Steve Squyres had mentioned that Independence rock, among those that appear to contain clay, was very unusual:

Mars rovers keep breaking new ground
Opportunity traverses sandy ‘maze’; Spirit studies strange bedrock.
By Leonard David
Updated: 8:56 p.m. ET July 19, 2005
"During its ascent of Husband Hill within the Columbia Hills, the robot came across a “very cool outcrop” of layered bedrock that has been tagged as Independence Rock, Squyres said.
“We’ve thoroughly worked it over with all of the arm instruments now, and it’s very strange stuff,” Squyres reported. He said it was one of the oddest things seen at Gusev.
“I’m not ready to go into much detail here about the chemistry and mineralogy yet, since we’re still chugging through the data,” Squyres noted. The rock is clearly highly altered, sporting an unusually low iron content, he said, “which isn’t something we’ve seen much of before.”
http://msnbc.msn.com/id/8634311/




- Bob Clark
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scalbers
post Dec 18 2005, 06:52 PM
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QUOTE (BruceMoomaw @ Dec 18 2005, 03:32 AM)
Thaks for the compliment, R.G.  Unfortunately, "Astronomy" eliminated everything I wrote on the MARSIS results (and there WAS some major new news there, which I will be free to report shortly at this site).

Moreover, I'm currently engaged in an exchange with Brian Hynek, who in turn got into quite a lively fight with the MER team at the AGU meeting as to whether the Meridiani deposits really are due to acidified groundwater, or whether their layering structure and chemical makeup has been misinterpreted and they're really repeated falls of volcanic ash mixed with acidified steam.  Until I hear a response from him to my latest message, I had better not elaborate right now.


Yes that was quite a debate at the end of that session. Haven't seen such a passionate exchange at a conference before. They did seem to leave some points hanging, so it will be interesting to see if some resolution can be achieved on these differing points of view.


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Guest_Myran_*
post Dec 18 2005, 09:49 PM
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Thank you for the correction about clays RGClark.

These findings could change at least my view on Mars somewhat just as BruceMoomaw pointed out, that clay deposits would be interesting targets to have a closer look at possible interesting chemistry in the past. Yes delibaretely stated in a diplomatic manner there. wink.gif
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