Methane implies Biology ??

[Widdekind]

On Earth, Methane is primarily produced by Biological processes*. So strong is that link, that Methane in Mars' atmosphere strongly suggests the presence of sub-surface Methanogen micro-organisms:

• Methane is a product of Biology. For Methane to be in Mars' atmosphere, there has to be a replenishable source... The most obvious source of Methane is organisms. So if you find Methane in an atmosphere, you can suspect there is Life**.

And, Methane is commonly observed across the Cosmos.

• * Martin Ince. [Rough Guides] Earth, pp. 256-257.
  **

http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/4243321/Mars-methane-discovery-hints-at-presence-of-life.html; cf. http://news.nationalgeographic.com/news/2004/10/1007_041007_mars_methane.html, http://dsc.discovery.com/news/2009/01/15/mars-methane-life.html; Volcanoes ruled out for Martian Methane, see: http://www.newscientist.com/article/dn8256-volcanoes-ruled-out-for-martian-methane.html

 

CONCLUSION (?):

 

If all Methane comes from Biological processes, and if Methane is common across the Cosmos, then perhaps Biology is common across the Cosmos.

[D H]

Methane is a product of Biology.

The implication here is that methane can only result from biological sources. That is not true.

 

 

So if you find Methane in an atmosphere, you can suspect there is Life.

You can suspect that, but you cannot conclude that. There are known abiotic mechanisms for production of methane even on the Earth. Volcanos, for example, spew methane. Titan's atmosphere has a significant portion of methane. That does not necessarily mean Titan harbors life.

 

 

And, Methane is commonly observed across the Cosmos.

That is intellectually dishonest. The vast majority of methane observed away from Earth is in the molecular clouds that form the interstellar medium. Are you truly claiming that this interstellar methane results from life?

 

 

CONCLUSION (?):

 

If all Methane comes from Biological processes, and if Methane is common across the Cosmos, then perhaps Biology is common across the Cosmos.

That all is a mighty big if, and it is demonstrably false.

 

 

===========================

 

As an aside, Widdekind, your use of multiple fonts and colors makes your posts look very similar to posts made crackpots. You might want to rethink your posting style.

[John Cuthber]

"On Earth, Methane is primarily produced by Biological processes*. So strong is that link, that Methane in Mars' atmosphere strongly suggests the presence of sub-surface Methanogen micro-organisms:"

 

 

On Earth, iron is primarily produced by blast furnaces. So strong is that link, that iron in meteorites strongly suggests the presence of blast furnaces in space.

 

Discuss.

[Moontanman]

very cool reply John

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I think maybe the lack of volcanoes on mars might indicate a biological source for methane. The percentage of methane on the earth is more than can be accounted for by volcanoes. But i like the way you think, Even the methane on Titan would seem to be more than non biological sources can completely account for. The giant planets have non biological conditions that can easily account for their methane. it is plausible we don't know of all non biological processes that can produce methane. But we know biology is a primary contributor under the conditions on the earth

[lucaspa]

The implication here is that methane can only result from biological sources. That is not true.

 

The articles did not say that. Did you read them? In particular, look at this one:

http://dsc.discovery.com/news/2009/01/15/mars-methane-life.html

 

"Whatever the source [biological or geological], methane on Mars should stick around for about 300 years, all things being equal. Instead, Mumma and his team, who published their findings in this week's issue of Science, found that over parts of Mars the methane is disappearing in a span of time as short as one year.

 

""We really can't tell if it's biological or geochemical at this time," Mumma added. "On Earth, it can be produced by either mechanism."

 

"The definitive way to determine the methane's origins is to analyze its isotopes. Methane produced from biological sources on Earth has distinctively different isotopic ratios than methane generated by geochemical processes."

 

" A new effort is underway to search for other gases that, like methane, are tied to biological processes on Earth. Targeted compounds include ethane, propane and hydrocarbons. "

 

Basically, this science news article has the required tentativeness. The continued influx of methane to Mar's atmosphere may indicate life. Right now, there are no observable geochemical processes -- like volcanoes -- that can account for the methane.

[D H]

The implication here is that methane can only result from biological sources. That is not true.[/quote']The articles did not say that. Did you read them?

I wasn't referring to the articles. I was referring to Wddikind's mischaracterization / oversimplification of the articles.

[CaptainPanic]

If Mars had an atmosphere full of oxygen, and methane was still present, then I'd tend to agree that something is going on... possibly something biological.

 

Since Mars has an atmosphere full of CO2, which isn't going to react with methane, the stability of methane is understandable.

 

Methane is produced biologically over here, because a lot of reactions to form methane from other hydrocarbons and/or other organic components have a negative Gibbs energy of reaction: meaning that they will proceed under the right circumstances.

 

That also means that it can be formed somewhere else...

 

I like the comparison that John made a few posts back, about the iron and blast furnaces. Perhaps a better comparison is sugar to CO2 and water. Most sugar on earth is consumed by biological processes and turned into CO2 and water. However, this reaction will work in total absence of anything living. You can just burn sugar.

[John Cuthber]

If you look at the earth's atmosphere there are lots of things that are a long way from equilibrium. The presence of oxygen, nitrogen and water (rather than dilute nitric acid) is one of the reall biggies.

Any of the 3 components on their own doesn't tell you a lot, but the mixture certainly indicates something very odd is happening.

 

If someone analyses the atmosphere of a distant planet and tells me that there is, for example, oxygen and methane or oxygen nitrogen and water present they have got more than half way to convincing me that there's life there but just finding methane doesn't prove anything.

[Martin]

Just wanted to say thanks to Widdekind for starting this thread! It has stimulated quite a bit of thought and discussion.

 

Maybe the key thing which we can learn from this is a Chem concept---the difference between an oxidizing and a reducing atmosphere, or other environment.

 

Thanks to everybody who has contributed. I assume, from all the question marks ?? that Widdekind was intentionally making questionable statements to serve as discussion-starters. Things he didn't believe or wasn't sure about like his "Conclusion (?) " were decorated with interrogation. This simple strategy seems to have been successful.

 

Lucaspa pointed out that some of the articles linked to are interesting. And is certainly better qualified to define the difference between reducing and oxidizing environment.

 

Unless somebody does the general theory here (electron-donors dominate versus where electron grabbers dominate) I will give it a try. In a reducing environment, methane and ammonia are the default, the natural way for C and H and N to exist. Earth has an oxidizing environment, Mars too, and methane is not the default---so on Mars and Earth, methane and ammonia are not the default. C likes to be CO2, H likes to be H2O, and all that. Somebody want to discuss?

 

EDIT: OK nobody handy who wants to discuss. One sign of life is chemicals that dont belong. So if you have an oxidizing environment and you see ammonia that might be a sign. But in a reducing environment where the basic default is stuff like methane and ammonia, then maybe some other chemical would be the one out of place. Maybe in that kind of environment (I'm just speculating) it would be oxygen or co2 that didn't belong. And then THEY would be a sign of life or some other departure from equilibrium.

 

Anyone who wants to correct or comment would be very welcome. The general topic of what chemicals are signs of life, in what different environments, is interesting.

Edited June 3, 2009 by Martin

[Widdekind]

I would like to point out, that iron is not a product of blast furnaces. Smelting only extracts previously existing Iron from rocks.

 

An apt, and accurate, analogy would be:

 

Iron is produced by

Big Stars

, and distributed by

Supernovae

. The presence of Iron implies the past presence of

Big Stars

, and

Supernovae

.

 

I'm sure, however, that there are Industrial Byproducts specific to Smelting & Blast Furnaces. And, the presence of those specific "Smelting signature compounds" (as it were) would, in fact, imply the presence of Heavy Industry on our hypothetical planet, yes?

 

I am glad everybody found this discussion stimulating. Logically, the link between Methane & Biology, coupled with the ubiquity of the former, suggests the possible ubiquity of the latter.

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...

Unless somebody does the general theory here (electron-donors dominate versus where electron grabbers dominate) I will give it a try. In a reducing environment, methane and ammonia are the default, the natural way for C and H and N to exist. Earth has an oxidizing environment, Mars too, and methane is not the default---so on Mars and Earth, methane and ammonia are not the default. C likes to be CO2, H likes to be H2O, and all that. Somebody want to discuss?

 

Are Molecular Clouds, where most Methane is apparently observed, Reducing Environments ?

Edited June 3, 2009 by Widdekind
Consecutive posts merged.

[Martin]

I am glad everybody found this discussion stimulating. Logically, the link between Methane & Biology, coupled with the ubiquity of the former, suggests the possible ubiquity of the latter.

 

Come on Widdekind. Be a gentleman and don't overdo it. It does not suggest the possible ubiquity of biology to me, for the reason I mentioned. It may suggest the possible ubiquity of biology to you. Fine But please don't keep insisting. Good discussion.

 

You make a valid point. Seeing iron is a sign that there were supernovas. I agree.

 

 

 

Are Molecular Clouds, where most Methane is apparently observed, Reducing Environments ?

 

Well I'm not an expert but I would say definitely. I hear about ammonia in those clouds, and methane, and molecular hydrogen H2, and atomic H----all those are reducing species. I also hear about carbon monoxide in those clouds, which again is reducing.

 

I would say that a reducing gascloud is the natural fart of stars. They blow off that kind of mix. It is their destiny. The nuclear fusion sequence and the periodic table of elements is just set up that way. In a different universe with different elements and chemistry and fusion reactions maybe it would be different. It would, yes, be different.

 

But in our universe seeing a big cloud of methane is a sign that stars have been there.

 

Just my non-expert opinion. We all need to be modest:D

[John Cuthber]

I would like to point out, that iron is not a product of blast furnaces. Smelting only extracts previously existing Iron from rocks.

 

An apt, and accurate, analogy would be:

 

Iron is produced by

Big Stars

, and distributed by

Supernovae

. The presence of Iron implies the past presence of

Big Stars

, and

Supernovae

.

 

I'm sure, however, that there are Industrial Byproducts specific to Smelting & Blast Furnaces. And, the presence of those specific "Smelting signature compounds" (as it were) would, in fact, imply the presence of Heavy Industry on our hypothetical planet, yes?

 

I am glad everybody found this discussion stimulating. Logically, the link between Methane & Biology, coupled with the ubiquity of the former, suggests the possible ubiquity of the latter.

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Consecutive posts merged

 

 

Are Molecular Clouds, where most Methane is apparently observed, Reducing Environments ?

 

Ho hum.

I guess I should have made it clear that I was talking about metalic iron rather than the iron nucleus (without reguard for oxidations state).

Oh! hang on a minute, I did. Unless you think that blast furnaces are nuclear reactors.

If it helps to destroy the strawman please insert the word "metalic" in front of the word iron wherever it apears in my original post.

[rpf_81]

Methane is a colorless, odorless gas. It is the main component of natural gas, used as heating fuel here on Earth, and is largely formed from the decay of plant life. Most of the natural methane in the earth's atmosphere comes from swamps and bogs. It is also produced as animals, from cattle to the smallest microbes, digest their food.

 

Methane is abundant in the atmospheres of the large outer planets in the solar system -- Jupiter, Uranus and Neptune -- but those worlds do not have the earthlike characteristics that make Mars interesting to many biologists.

[Widdekind]

OBSERVATION: The Biomass of various living species decreases w/ increasing species Complexity & Intelligence. For example, on Earth, there is one Civilized species (H. sapiens), several reasonably intelligent species (Chimpanzees, Dolphins, Octopuses, Squid), many cunning species (Wolves, Crows, Ravens, Elephants, Lions, etc.), and so on, until ultimately there is more Biomass in microbes than all other Earth Life-forms combined. And, surely (?), there is more mass in non-living Organic Chemicals, than Organic Chemicals in living creatures.

 

CONCLUSION: If we lived in a very fertile Universe, supporting Life across the Cosmos, the most basic observable "footprint" of that fact, apparent even to our present primitive detection capacities, would be copious quantities of Organic Chemicals distributed liberally & ubiquitously across the Cosmos.

 

This is exactly what we observe.

 

Thus, although, at present, our data is very limited -- Complex Life is known on 1 of 1 intensely studied planets*, and basic Organic Chemicals are blatantly apparent across the Cosmos -- everything we know is consistent with our Universe being very fertile, supporting an abundance of Life.

*

Venus may still support microbes up in its

Sulphuric Acid

clouds, as survivors from its long-evaporated oceans

(T. Haines & C. Riley. (

BBC

)

Space Odyssey: Voyage to the Planets

; National Geographic Channel

Naked Science -- Deadliest Planets

(TV))

. And, on Earth, there is more

Biomass

of microbes in the deep subsurface, than

Biomass

of all

Life

on the surface

(Discovery Channel

Inside the Earth

(TV))

, implying that Mars, too, may indeed still support primitive microbial-type

Life

-forms in its deeper, and warmer, subsurface, as survivors from its warmer & wetter past.

[Ophiolite]

The abundance of organic chemicals on Earth is the cause of life, not its consequence. The abundance of organic chemicals in the interstellar medium points to the potential for life elsewhere, but not to its necessity. We do not yet know what environmental conditions and events must act upon the organic chemicals in order to generate life. Therefore, any conclusions we reach based upon our 1 of 1 intensely studied planet must be reclassified as speculations.

Edited June 10, 2009 by Ophiolite
Correct annoying typographical errors.

[D H]

Therefore, any conclusions we reach based upon our 1 of 1 intensely studied planet must be recalssified as speculations.

That is a very key point. Extrapolation is always a dangerous thing to do in science, even when there is a strong theoretical basis. Case in point: Newtonian mechanics. 19^th century physicists had a quarter of millennium of accumulated evidence of the validity of Newtonian mechanics. Yet they started seeing big problems when they extrapolated what they thought they knew to be true to the realms of the very small, the very large, and the very fast. They had anything but a sample size of one on which to base these extrapolations, they had a very strong theoretical basis for thinking the extrapolations were correct, and yet the extrapolations didn't agree with observations.

 

Extrapolating from a sample size of one is just ludicrous. Extrapolating from a sample size of one for which we do not have a theoretical basis (we do not yet have a cogent theory that describes how life arose) is beyond ludicrous. Doing so might, for example, lead one to believe that space is chock full of blast furnaces. Or life.

 

The bottom line is, we do not know yet.

[John Cuthber]

By analogy with Widdekind's post;

On the basis of one extensively studied case*, everyone is a 43 year old bloke with a beard.

 

*That's me, by the way, and I have checked.

 

Some of the ideas put forward here are really so funny there should be a comedy section.

[VedekPako]

We're walking on a fallacious minefield here. We first need to figure out if there's another way methane is produced other than biological processes.

[Ophiolite]

We first need to figure out if there's another way methane is produced other than biological processes.

There are lots.

 

The two obvious ones are volcanic activity and cometary impact. Volcanoes release variable amounts of methane. Has there been recent volcanic activity on Mars? Quite possibly.(1,2,3)

Remember also that volcanic activity includes gaseous releases from hot springs. (4) These would not be as readily detectable as a full blown eruption. (A proper eruption would be difficult to miss.)

 

Comets obviously contain the necessary components for the production of methane and there are plausible mechanisms which would generate it following impact. (5)

 

While the first of these would produce variable amounts of methane, the second would obviously be a single hit with subsequent decline. Two further methods offer a mechanism for variable methane production that does not involve life, while a third mechanism could cause seasonal variations in atmospheric methane.

 

First is the possibility that methane could be generated through the thermal decomposition of clathrates.(6) Secondly is its generation from atmospheric hydrolosis of carbon monoxide.(7) The third is temperature controlled adsorption of methane in the Martian regolith. (8)

 

This is only the briefest of explorations of a complex and debated topic. Mechanisms I have not provided references for include impact by iron meteorite, serpentinisation, and degradation of ancient biogenic material.

 

My opinion is that there is life on Mars. However, the methane evidence to date certainly does not prove this and so far is readily explained by non-biological processes.

 

References:

 

1. NASA’s Observation of the Week Recent Lava Flows on Mars, Feb 3, 1999.

 

2. Vaucher, J., et al, LAVA RHEOLOGY IN RECENT VOLCANOTECTONIC ACTIVITY AT CERBERUS, MARS

 

3. Neukum, et al, "Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera" 2004 Nature 432, .

 

4. Socki, R.A., et al, Carbon Isotope Equilibrium Between Methane and Carbon Dioxide in two Continental Hydrothermal Systems: Implications for Methane Production on Mars, American Geophysical Union, Fall Meeting 2008, abstract #P51A-1392

5. M.E.Kress, C.P.McKay Formation of methane in comet impacts: implications for Earth, Mars, and Titan, 2004 Icarus, Volume 168, Issue 2, p. 475-483

 

6. McMenamin, D.S., McGill, G.E., Thermal Anomalies Suggest that Ongoing Clathrate Dissociation in Icy Sediment Contributes to Martian Atmospheric Methane, 2009 40th Lunar and Planetary Science Conference

 

7. Bar-Nun, A. Dimitrov, V. Methane on Mars: A product of H2O photolysis in the presence of CO 2006. Icarus 181, 320 322

 

8. Gough, R.V. et al, Methane Adsorption on Martian Soil Analogs: A Possible Abiogenic Explanation for Methane Variability.2009 40th Lunar and Planetary Science Conference

[Martin]

My opinion is that there is life on Mars...

 

that is interesting, Ophi. In my life i have never suspected there might be life (currently alive life anyway) on Mars. But my past experience of you is knowledgeable and rational, so maybe I will adjust my subjective probabilities by a percentage point or so.

[Widdekind]

By analogy with Widdekind's post;

On the basis of one extensively studied case*, everyone is a 43 year old bloke with a beard.

 

*That's me, by the way, and I have checked.

 

Some of the ideas put forward here are really so funny there should be a comedy section.

 

That's not fair -- we can actually observe 6 billion humans, in enough detail, to disprove that claim.

 

The fact is this -- everywhere we've looked, to the maximum of the detail our primitive detectors, we have observed Life (Earth), possible Life (Mars), and the necessary pre-cursors to Life (ISM, GMCs).

 

A better revision of your "beard analogy" would be this:

You're near-sighted, 20/400...

You know you've got a beard...

And everywhere you look around your room, your blurry vision sees dark splotchy shadows on peoples' faces precisely where beards

would

be if they wore them.

Does that guarantee that everybody in that room has a beard? No. But it's perfectly consistent w/ that possibility -- that possibility, that everybody there has beards, is not flagrantly false.

 

And, here's a counter-example -- "The Moon is made of Cheese". The obvious rebuttle is, "The Moon's density is completely incompatible w/ that". That is a fair & balanced example, of something, that is completely & blatantly & flagrantly false.

 

But, that is absolutely dis-similar from a "Blurry Vision & Beards" situation, which is what Mankind currently faces, w/ his primitive detection equipment, & limited lack of data.

 

We've excavated 1% of the archaeological site... and, so far, all the data is consistent w/ a really big building.

 

"

The jury's still out, but it looks promising

" --

fair & balanced summary of situation

[Ophiolite]

Wieddekind, how do you address the several abiogenic mechanisms for generating the observed methane on Mars? The simplest explanation is the non-biological one. Unless you can find substantive fault in each alternative mechanism the biological source for the methane must be rejected.

 

Martin, I have serious reservations about the process by which the Viking data was interpreted as failing to reveal life. This incident is certainly not conclusive, but the approach was sloppy science at best and leaves serious question marks. While I should not be at all surprised if we established conclusively there was no life on Mars, I should nod knowingly (and somewhat smugly) if we ever confirm its presence.

[John Cuthber]

We're walking on a fallacious minefield here. We first need to figure out if there's another way methane is produced other than biological processes.

 

The reaction of hot iron (like a meteor) with carbonates will generate iron carbides. Reaction of these with water will generate a truly awful yeild of methane.

Other metals might well give a better yield but I don't care. I only have to make a bit of methane abiotically to prove the point.

 

If you generate carbon in the super hot conditions of a star thenn let the star cool that carbon will react with leftover hydrogen to produce methane.

That's another possible, reasonable, explanation.

Of course, it might be that the gas board laid a really long pipeline out into the distant universe in a bid to sell gas to ET, but that's a bit speculative.

 

Also I can only presume that widdekind is deliberatlely missing the point again.

I was pointing out that extrapolating from one local observation to the whole universe is so bizarely unscientific as to be funny.

[Widdekind]

Also I can only presume that widdekind is deliberatlely missing the point again. I was pointing out that extrapolating from one local observation to the whole universe is so bizarely unscientific as to be funny.

 

I deny the accuracy of that assertion.

We can do better than merely "one local observation"... albeit, barely better.

 

For, we can see Life on Earth...

possible Life on Mars...

and copious quantities of Organic Chemicals across the Galaxy.

 

CONCLUSION: I would agree, that a "completely primitive" Cave Man, looking out across Ice Age Europe, and saying, "Man, I'm convinced there's Life across the Cosmos", actually would be "extrapolating from one local observation to the whole Universe". But I deny that that is what Mankind is doing today, having, as we do, partial information, from across the Cosmos, all of which could be construed as completely consistent, with Life being abundant across the Cosmos.

 

Present data is doesn't settle the issue, but it hints & suggests more strongly for frequent Life, as for its miraculous rarity (which would, incidentally, violate the Copernican Principal).

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Wieddekind, how do you address the several abiogenic mechanisms for generating the observed methane on Mars? The simplest explanation is the non-biological one. Unless you can find substantive fault in each alternative mechanism the biological source for the methane must be rejected.

 

Martin, I have serious reservations about the process by which the Viking data was interpreted as failing to reveal life. This incident is certainly not conclusive, but the approach was sloppy science at best and leaves serious question marks. While I should not be at all surprised if we established conclusively there was no life on Mars, I should nod knowingly (and somewhat smugly) if we ever confirm its presence.

 

According to NASA,

Living systems produce more than 90 per cent of Earth's atmospheric methane; the balance is of geochemical origin.

Thus, brashly applying these statistics to Mars, all its Methane could quite conceivably come from Life.

 

Why is the "simplest" explanation a non-Biological one? What is so "complicated" about "hey, man, Martian microbes make Methane" ? Is not there some sort of preconceived "Life-phobia" in such assertions ?

 

W/o being flippant, I see it, as an assumption, that admittedly more complex Bio-Chemical Processes must be more rare. For, as afore-cited, on Earth, the exact converse is true -- the more complex Bio-Chemical Processes produce most of the Methane.

 

Therefore, from my current understanding, I deny the assumed equivalence of "Complexity <=> Rarity".

[Ophiolite]

I deny the accuracy of that assertion. (That in postulating the probability of life in the universe we are extrapolating from one local observation.)

Deny away. Your denial is an opinion, not a scientifically based observation. You base the validity of your denial on a tripod of observations.

For, we can see Life on Earth...

possible Life on Mars...

and copious quantities of Organic Chemicals across the Galaxy.

Yes, we see life on Earth.

 

There is the possibility of life on Mars, yes. However, you have implicitly engaged a cyclical argument that we should view the methane as good evidence of life on Mars because life is probably abundant in the universe.

 

The abundance of organic chemicals is irrelevant. Sure, they demonstrate that the raw materials for life are abundant, but until we understand the mechanism of abiogenesis in detail we cannot know whether its origin is inevitable, or unique.

 

So we are left with one thing. The observation of life on Earth. That is what you are extrapolating from. Your denial is the expression of an opinion, nothing more.

 

My opinion is that life is an inevitable consequence of the nature of the universe. My opinion is that life arises readily in many places and is abundant throughout the universe. But these are only opinions. Opinions have no scientific validity. They provide a basis from which to explore possibilities and explanations, but even more than hypotheses or theories they are subject to immediate change when new evidence is presented.

 

Present data is doesn't settle the issue, but it hints & suggests more strongly for frequent Life, as for its miraculous rarity (which would, incidentally, violate the Copernican Principal).

The Copernican Principle is a philosophical convenience, not a physical absolute. (Principle, by the way, not principal.)

 

Thus, brashly applying these statistics to Mars, all its Methane could quite conceivably come from Life.

We are reasonably confident that there are not large herds of bovines roaming the Argyre desert. We see no vast tropical forests swathing the slopes of Mareneris Valles. The substantial biosphere responsible for the major generation of Earth's methane is very obviously absent from Mars.

 

It might just be remotely possible that all the methane on Mars could be derived from biological sources. It is very, very unlikely, given the diverse range of alternative means of generating it abiogenically.

 

Note that we are disgreeing over the level of probability. There is no justification for asserting that Martian methane is probably biogenic. (Note it is my opinion that it is, but we have already established the low value of opinions.)

Why is the "simplest" explanation a non-Biological one? What is so "complicated" about "hey, man, Martian microbes make Methane" ? Is not there some sort of preconceived "Life-phobia" in such assertions ?

Since it is my opinion that life is widespread throughout the universe; since it is my opinion that there is life on Mars; since it is my opinion that the methane we are detecting has been produced by life; for all of these reasons I do not see how you can reasonably accuse me of harbouring a preconceived "Life phobia".

 

The simplest explantion is the non-biological one because it involves the fewest presumptions. We have several non-biological explanations for the Martian methane, some of which we know for certain do occur, others of which are highly likely. The alternative is an unquantifiable possibility of life. Thus the non-biological explanations wins hands down and that is not an opinion.