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Origin of life: Time to end speculation about a reducing atmosphere for the early Earth

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says physicist David Tyler at Access Research Network:

It is universally claimed that the early Earth had a reducing atmosphere. Models have been proposed for the gases to have accumulated after outgassing of volatiles from volcanism. This reducing atmosphere was originally thought to have been dominant throughout the Precambrian, but signs of oxygenation have pushed it back earlier than the earliest rocks that researchers have discovered. The earlier claims for a reducing atmosphere have other explanations, such as resulting from the action of hydrodynamic fluids. This has put severe constraints on theories of abiogenesis, because the proposed mechanisms typically presuppose a reducing atmosphere. By the earliest Archaean, the atmosphere was at least neutral – so abiogenesis is inferred to have occurred even earlier. But moving back earlier brings us to the Late Heavy Bombardment which is generally deemed to have obliterated all traces of any life that may have been present. So there is a little window in the Hadean that is deemed to have offered a reducing atmosphere free from the destructive bombardment.

The evidence for a Hadean reducing atmosphere has been entirely theoretical. It does not rest on empirical evidence because there has been so little to work with. However, a new study of zircon crystals has reported some fascinating results that allow speculation about the Hadean black box to be replaced by empirical evidence. Zircons have been identified that carry signatures identifying them with the Hadean – and zircons are remarkably stable once formed. Using zircons dated to almost 4.4 Ga, the researchers have analysed their redox state (a measure of the degree of oxygenation of the mineral). This gives a handle on the type of gases that would have been outgassed by the magmas, and so, according to these models of Earth history, the type of atmosphere that would have been formed.

It is important to realise what was predicted by prevailing theories: the redox state of the magmas with which the zircons were associated was expected to be strongly reducing. This prediction is a necessary part of the Earth having a reducing atmosphere in the Hadean. The research findings did not confirm the prediction.


Nice Article Dr. Tyler. a few notes:
Late Heavy Bombardment - graph http://www.reasons.org/files/clip_image008_0000.jpg Life - Its Sudden Origin and Extreme Complexity - Dr. Fazale Rana - video http://www.metacafe.com/watch/4287513 When Did Life First Appear on Earth? - Fazale Rana - December 2010 Excerpt: The primary evidence for 3.8 billion-year-old life consists of carbonaceous deposits, such as graphite, found in rock formations in western Greenland. These deposits display an enrichment of the carbon-12 isotope. Other chemical signatures from these formations that have been interpreted as biological remnants include uranium/thorium fractionation and banded iron formations. Recently, a team from Australia argued that the dolomite in these formations also reflects biological activity, specifically that of sulfate-reducing bacteria. http://www.reasons.org/when-did-life-first-appear-earth Dr. Hugh Ross - Origin Of Life Paradox - video http://www.metacafe.com/watch/4012696
Ah, of course. A "localized reducing environment." That allows us to keep the idea of a reducing environment, while not contradicting the growing evidence that, globally, there was not a reducing atmosphere. Interesting. I note he says "environment" not "atmosphere," as usually discussed. Does a "reducing environment" mean a liquid environment, or does he propose a localized atmospheric environment that is constantly resupplied by the volcanic plume in order to avoid dilution? I presume the latter. In any event, a localized environment would theoretically allow us to pursue the idea of a reducing environment, but it would presumably reduce by several orders of magnitude the available physical resources for producing the organic compounds needed for the origin of life. Now we cannot include in the calculation all the elements available on the Earth, but instead, can include only the resources available in a small number of small locales. Sounds like they've kept the reducing environment idea alive -- albeit at the expense of the probabilities. We'll have to stay tuned. Eric Anderson
Eric asked: "Do most researchers agree with Miller that a reducing atmosphere is needed, or have they discarded the idea?" It appears to me that all ideas are kept in the melting pot - nothing is discarded (in the interest of keeping all options open). Jeffrey Bada continues to champion the Miller experiments. This is from a commentary in 2003: "Contemporary geoscientists tend to doubt that the primitive atmosphere had the highly reducing composition used by Miller in 1953. Many have suggested that the organic compounds needed for the origin of life may have originated from extraterrestrial sources such as meteorites. However, there is evidence that amino acids and other biochemical monomers found in meteorites were synthesized in parent bodies by reactions similar to those in the Miller experiment. Localized reducing environments may have existed on primitive Earth, especially near volcanic plumes, where electric discharges may have driven prebiotic synthesis." Prebiotic Soup - Revisiting the Miller Experiment, by Jeffrey L. Bada and Antonio Lazcano (Science, 300, May 2 2003: 745-746) David Tyler
Whether you believe in the bibles account of creation or not, you have to ask yourself, why did the the writers of that time, tell us the atmosphere would have to worked on. They knew nothing about other planets, and the bad atmospheres found there. They walked around in unpolluted environments herding sheep and goats. They would not have had any preconceived idea, on how the earth was made. For all they knew , presto here was earth. So thousands of years ago , we were already told that the atmosphere had to be prepared. Are not the scientists fighting over that same topic today? So to speed up the process, why not look at it like, an intelligence was preparing it. Would not that speed up the process, exceedingly? If you look at it from the wrong angle, you are not going anywhere. That is why after 150 years, main stream scientists still don't know. I think I want my money back that went into all this research. Even by the amount of paper used alone , I could live very well. MrDunsapy
I should add, to provide a bit more context, that in an earlier interview (1996) Miller gave some additional explanation:
"We really don't know what the Earth was like three or four billion years ago. So there are all sorts of theories and speculations. The major uncertainty concerns what the atmosphere was like. This is [a] major area of dispute. In early 1950's, Harold Urey suggested that the Earth had a reducing atmosphere, since all of the outer planets in our solar system- Jupiter, Saturn, Uranus and Neptune- have this kind of atmosphere. A reducing atmosphere contains methane, ammonia, hydrogen and water. The Earth is clearly special in this respect, in that it contains an oxygen atmosphere which is clearly of biological origin. Although there is a dispute over the composition of the primitive atmosphere, we've shown that either you have a reducing atmosphere or you are not going to have the organic compounds required for life. If you don't make them on Earth, you have to bring them in on comets, meteorites or dust. Certainly some material did come from these sources. In my opinion the amount from these sources would have been too small to effectively contribute to the origin of life."
As he says, there is a dispute in the field, so no doubt some researchers think they can get around the need for a reducing atmosphere. It would be interesting to know if anyone has surveyed the literature recently for an up-to-date take on the question. Do most researchers agree with Miller that a reducing atmosphere is needed, or have they discarded the idea? Eric Anderson
In a 2003 interview with Stanley Miller (50th anniversary of the Miller-Urey experiment), Miller was asked about whether a reducing atmosphere was necessary for a (naturalistic) formation of life scenario:
"Astrobiology Magazine: What is your current opinion on the need for a primitive reducing atmosphere for pre-biotic life to take hold 3.5 to 3.8 billion years ago? Stanley Miller: I have not found an alternative to disprove the need for a primitive reducing atmosphere."
If, as Tyler suggests abive, the existence of a reducing atmosphere is growing ever more tenuous, it makes a naturalistic origin of life that much more difficult and speculative. Eric Anderson
It is a shame that people interested in science even have to talk about 'evolution'. As though it is real, anything other than a myth. Scientists that use million and billions of years, as though that is a creative process in itself,have failed to realize how time is also destructive. What is scientific about throwing years at something? If I want a loaf of bread, do I say if I wait long enough that loaf will just show for lunch. 'Evolution' as some scientists are promoting, is an impossibility. It is a failure of the theory itself because it can not explain the origins of life.So another theory has to be dreamed up. So what they have is one theory 'evolution' that demands another theory 'abiogenesis', that has to support the first theory. That is circular thinking, and not scientific. So you don't have think that 'evolution' is even remotely possible. There is no evidence at all for that. It is a myth. No different, than some remote tribe that makes up some God. So time periods and assumptions, do not bring about life. What the main stream scientist have done, is created "The Greatest Snow Job on Earth". You know, a blizzard of little bits of info. that bury the truth, about life. But in time, this will melt away, because of no evidence. So to them, do you see how destructive time can be? MrDunsapy
Even if there was a reducing atmosphere for the small window of time they envision, how in the world can they expect life to have emerged in such a short time. Most people think there were billions of years available for life to evolve on earth which is obviously not true. Millions of years is probably not even available. How then can time be an ally of evolution? It cannot. It is an enemy. Available time has been shrinking, not only for life to have evolved, but for organisms to have evolved after that. More and more fossils are pushing back the earliest finds for various organisms scrunching the time available for them to have evolved to that state to unrealistic numbers. I'm not sure how viable evolution would be even if unlimited time was available, but it is not. tjguy

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