Stanley Miller's classic "primordial soup" experimental setup,
with a simulated ocean, lightning and broth
of hydrogen, methane, ammonia and water.
Posted on 04/08/2005 7:39:14 AM PDT by PatrickHenry
A new University of Colorado at Boulder study indicates Earth in its infancy probably had substantial quantities of hydrogen in its atmosphere, a surprising finding that may alter the way many scientists think about how life began on the planet.
Published in the April 7 issue of Science Express, the online edition of Science Magazine, the study concludes traditional models estimating hydrogen escape from Earth's atmosphere several billions of years ago are flawed. The new study indicates up to 40 percent of the early atmosphere was hydrogen, implying a more favorable climate for the production of pre-biotic organic compounds like amino acids, and ultimately, life.
The paper was authored by doctoral student Feng Tian, Professor Owen Toon and Research Associate Alexander Pavlov of CU-Boulder's Laboratory for Atmospheric and Space Physics with Hans De Sterk of the University of Waterloo. The study was supported by the NASA Institute of Astrobiology and NASA's Exobiology Program.
"I didn't expect this result when we began the study," said Tian, a doctoral student in CU-Boulder's Astrobiology Center at LASP and chief author of the paper. "If Earth's atmosphere was hydrogen-rich as we have shown, organic compounds could easily have been produced."
Scientists believe Earth was formed about 4.6 billion years ago, and geologic evidence indicates life may have begun on Earth roughly a billion years later.
"This study indicates that the carbon dioxide-rich, hydrogen-poor Mars and Venus-like model of Earth's early atmosphere that scientists have been working with for the last 25 years is incorrect," said Toon. In such atmospheres, organic molecules are not produced by photochemical reactions or electrical discharges.
Toon said the premise that early Earth had a CO2-dominated atmosphere long after its formation has caused many scientists to look for clues to the origin of life in hydrothermal vents in the sea, fresh-water hot springs or those delivered to Earth from space via meteorites or dust.
The team concluded that even if the atmospheric CO2 concentrations were large, the hydrogen concentrations would have been larger. "In that case, the production of organic compounds with the help of electrical discharge or photochemical reactions may have been efficient," said Toon.
Amino acids that likely formed from organic materials in the hydrogen-rich environment may have accumulated in the oceans or in bays, lakes and swamps, enhancing potential birthplaces for life, the team reported.
The new study indicates the escape of hydrogen from Earth's early atmosphere was probably two orders of magnitude slower than scientists previously believed, said Tian. The lower escape rate is based in part on the new estimates for past temperatures in the highest reaches of Earth's atmosphere some 5,000 miles in altitude where it meets the space environment.
While previous calculations assumed Earth's temperature at the top of the atmosphere to be well over 1,500 degrees F several billion years ago, the new mathematical models show temperatures would have been twice as cool back then. The new calculations involve supersonic flows of gas escaping from Earth's upper atmosphere as a planetary wind, according to the study.
"There seems to have been a blind assumption for years that atmospheric hydrogen was escaping from Earth three or four billion years ago as efficiently as it is today," said Pavlov. "We show the escape was limited considerably back then by low temperatures in the upper atmosphere and the supply of energy from the sun."
Despite somewhat higher ultraviolet radiation levels from the sun in Earth's infancy, the escape rate of hydrogen would have remained low, Tian said. The escaping hydrogen would have been balanced by hydrogen being vented by Earth's volcanoes several billion years ago, making it a major component of the atmosphere.
In 1953, University of Chicago graduate student Stanley Miller sent an electrical current through a chamber containing methane, ammonia, hydrogen and water, yielding amino acids, considered to be the building blocks of life. "I think this study makes the experiments by Miller and others relevant again," Toon said. "In this new scenario, organics can be produced efficiently in the early atmosphere, leading us back to the organic-rich soup-in-the-ocean concept."
In the new CU-Boulder scenario, it is a hydrogen and CO2-dominated atmosphere that leads to the production of organic molecules, not the methane and ammonia atmosphere used in Miller's experiment, Toon said.
Tian and other team members said the research effort will continue. The duration of the hydrogen-rich atmosphere on early Earth still is unknown, they said.
do you know of any attempt to "replicate the creation of the simplest form of life" involving a continuous 500,000,000 year trial period, uncountable yottajoules of electrical discharge, and zettatonnes of organic slurry, in a lab spanning 201,280,000 square miles?
No?
then sit down, and attempt to come up with an intelligent objection.
No, most everything living reproduces and every living thing on earth dies. But again, point me to the 50mer protein winner(self reproducing ... or any for that matter) that has been produced from scratch by abiogenetic processes.(living things produce proteins of hundreds of mers)
Such as trying to write a soap opera plot for all the combinations and permutations of the actors.
It's not necessarily easier to control things at lower temperatures. Some necessary reactions just may not occur. That's why seeds lie dormant in the winter.
I have suggested to some Concerned People that they could grow their cultures at higher temperatures to get a bit of a speedup. They were already doing so.
There is a range of temperatures for which things proceed. Most living things survive over a large range of temperature. Some are more fragile than others.
Actually, (and I'm not a biologist or biochemist so I may not be up to date on this) I think that scientists are still working on just the first step in such a process, namely the production of organic compounds from materials likely to be available on the early earth. I don't think that there's been a whole lot of serious research on the other intermediate steps that would be necessary to go from organic compounds to living cells.
Actually, a lot of work *has* been done -- and is still being done -- on the various stages between the simple production of organic compounds from "primal" compounds on the "low" end, and the realm of replication via DNA on the "high" end.
In the interests of time (mine), I'll just repeat part of an earlier post of mine:
And:The Path from the RNA World Anthony M. Poole, Daniel C. Jeffares, David Penny: Institute of Molecular Biosciences, Massey University
Abstract: We describe a sequential (step by step) Darwinian model for the evolution of life from the late stages of the RNA world through to the emergence of eukaryotes and prokaryotes. The starting point is our model, derived from current RNA activity, of the RNA world just prior to the advent of genetically-encoded protein synthesis. By focusing on the function of the protoribosome we develop a plausible model for the evolution of a protein-synthesizing ribosome from a high-fidelity RNA polymerase that incorporated triplets of oligonucleotides. With the standard assumption that during the evolution of enzymatic activity, catalysis is transferred from RNA M RNP M protein, the first proteins in the ``breakthrough organism'' (the first to have encoded protein synthesis) would be nonspecific chaperone-like proteins rather than catalytic. Moreover, because some RNA molecules that pre-date protein synthesis under this model now occur as introns in some of the very earliest proteins, the model predicts these particular introns are older than the exons surrounding them, the ``introns-first'' theory. Many features of the model for the genome organization in the final RNA world ribo-organism are more prevalent in the eukaryotic genome and we suggest that the prokaryotic genome organization (a single, circular genome with one center of replication) was derived from a ``eukaryotic-like'' genome organization (a fragmented linear genome with multiple centers of replication). The steps from the proposed ribo-organism RNA genome M eukaryotic-like DNA genome M prokaryotic-like DNA genome are all relatively straightforward, whereas the transition prokaryotic-like genome M eukaryotic-like genome appears impossible under a Darwinian mechanism of evolution, given the assumption of the transition RNA M RNP M protein. A likely molecular mechanism, ``plasmid transfer,'' is available for the origin of prokaryotic-type genomes from an eukaryotic-like architecture. Under this model prokaryotes are considered specialized and derived with reduced dependence on ssRNA biochemistry. A functional explanation is that prokaryote ancestors underwent selection for thermophily (high temperature) and/or for rapid reproduction (r selection) at least once in their history.
On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells William Martin and Michael J. RussellAnd:Abstract: All life is organized as cells. Physical compartmentation from the environment and self-organization of self-contained redox reactions are the most conserved attributes of living things, hence inorganic matter with such attributes would be life’s most likely forebear. We propose that life evolved in structured iron monosulphide precipitates in a seepage site hydrothermal mound at a redox, pH and temperature gradient between sulphide-rich hydrothermal fluid and iron(II)-containing waters of the Hadean ocean floor. The naturally arising, three-dimensional compartmentation observed within fossilized seepage-site metal sulphide precipitates indicates that these inorganic compartments were the precursors of cell walls and membranes found in free-living prokaryotes. The known capability of FeS and NiS to catalyse the synthesis of the acetyl-methylsulphide from carbon monoxide and methylsulphide, constituents of hydrothermal fluid, indicates that pre-biotic syntheses occurred at the inner surfaces of these metal-sulphide-walled compartments, which furthermore restrained reacted products from diffusion into the ocean, providing sufficient concentrations of reactants to forge the transition from geochemistry to biochemistry. The chemistry of what is known as the RNA-world could have taken place within these naturally forming, catalyticwalled compartments to give rise to replicating systems. Sufficient concentrations of precursors to support replication would have been synthesized in situ geochemically and biogeochemically, with FeS (and NiS) centres playing the central catalytic role. The universal ancestor we infer was not a free-living cell, but rather was confined to the naturally chemiosmotic, FeS compartments within which the synthesis of its constituents occurred. The first free-living cells are suggested to have been eubacterial and archaebacterial chemoautotrophs that emerged more than 3.8 Gyr ago from their inorganic confines. We propose that the emergence of these prokaryotic lineages from inorganic confines occurred independently, facilitated by the independent origins of membrane-lipid biosynthesis: isoprenoid ether membranes in the archaebacterial and fatty acid ester membranes in the eubacterial lineage. The eukaryotes, all of which are ancestrally heterotrophs and possess eubacterial lipids, are suggested to have arisen ca. 2 Gyr ago through symbiosis involving an autotrophic archaebacterial host and a heterotrophic eubacterial symbiont, the common ancestor of mitochondria and hydrogenosomes. The attributes shared by all prokaryotes are viewed as inheritances from their confined universal ancestor. The attributes that distinguish eubacteria and archaebacteria, yet are uniform within the groups, are viewed as relics of their phase of differentiation after divergence from the non-free-living universal ancestor and before the origin of the free-living chemoautotrophic lifestyle. The attributes shared by eukaryotes with eubacteria and archaebacteria, respectively, are viewed as inheritances via symbiosis. The attributes unique to eukaryotes are viewed as inventions specific to their lineage. The origin of the eukaryotic endomembrane system and nuclear membrane are suggested to be the fortuitous result of the expression of genes for eubacterial membrane lipid synthesis by an archaebacterial genetic apparatus in a compartment that was not fully prepared to accommodate such compounds, resulting in vesicles of eubacterial lipids that accumulated in the cytosol around their site of synthesis. Under these premises, the most ancient divide in the living world is that between eubacteria and archaebacteria, yet the steepest evolutionary grade is that between prokaryotes and eukaryotes.
The emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front M. J. RUSSELL & A. J. HALL: Department of Geology and Applied Geology, University of GlasgowAnd:Abstract: Here we argue that life emerged on Earth from a redox and pH front at c. 4.2 Ga. This front occurred where hot (c. 150)C), extremely reduced, alkaline, bisulphide-bearing, submarine seepage waters interfaced with the acid, warm (c. 90)C), iron-bearing Hadean ocean. The low pH of the ocean was imparted by the ten bars of CO2 considered to dominate the Hadean atmosphere/hydrosphere. Disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal FeS membrane. Iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites. Our hypothesis is that the FeS membrane, laced with nickel, acted as a semipermeable catalytic boundary between the two fluids, encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers. The ocean provided carbonate, phosphate, iron, nickel and protons; the hydrothermal solution was the source of ammonia, acetate, HS", H2 and tungsten, as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde. The mean redox potential (ÄEh) across the membrane, with the energy to drive synthesis, would have approximated to 300 millivolts. The generation of organic anions would have led to an increase in osmotic pressure within the FeS bubbles. Thus osmotic pressure could take over from hydraulic pressure as the driving force for distension, budding and reproduction of the bubbles. Condensation of the organic molecules to polymers, particularly organic sulphides, was driven by pyrophosphate hydrolysis. Regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the Hadean ocean. This was the first use by a metabolizing system of protonmotive force (driven by natural ÄpH) which also would have amounted to c. 300 millivolts. Protonmotive force is the universal energy transduction mechanism of life. Taken together with the redox potential across the membrane, the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt. The role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers. This organic take-over of the membrane material led to the miniaturization of the metabolizing system. Information systems to govern replication could have developed penecontemporaneously in this same milieu. But iron, sulphur and phosphate, inorganic components of earliest life, continued to be involved in metabolism.
Obcells as Proto-Organisms: Membrane Heredity, Lithophosphorylation, and the Origins of the Genetic Code, the First Cells, and Photosynthesis (Journal of Molecular Evolution, Volume 53 - Number 4/5, 2001)For a schematic overview of the scenario that's been indicated by the evidence and research, here are two different renderings of the same process:The universal ancestor was a thermophile or a hyperthermophile: tests and further evidence
On the RNA World: Evidence in Favor of an Early Ribonucleopeptide World
Inhibition of Ribozymes by Deoxyribonucleotides and the Origin of DNA
Genetic Code Origin: Are the Pathways of Type Glu-tRNAGln to Gln-tRNAGln Molecular Fossils or Not?
Johnston WK, Unrau PJ, Lawrence MS, Glasner ME, Bartel DP.RNA-catalyzed RNA polymerization: accurate and general RNA-templated primer extension. Science. 2001 May 18;292(5520):1319-25.
Ferris JP. (1999 Jun). Prebiotic synthesis on minerals: bridging the prebiotic and RNA worlds. Biol Bull , 196, 311-4.
Levy M, and Miller SL. (1999 Jun). The prebiotic synthesis of modified purines and their potential role in the RNA world. J Mol Evol , 48, 631-7.
Unrau PJ, and Bartel DP. (1998 Sep 17). RNA-catalysed nucleotide synthesis [see comments] Nature , 395, 260-3.
Roth A, and Breaker RR. (1998 May 26). An amino acid as a cofactor for a catalytic polynucleotide [In Process Citation] Proc Natl Acad Sci U S A , 95, 6027-31.
Jeffares DC, Poole AM, and Penny D. (1998 Jan). Relics from the RNA world. J Mol Evol , 46, 18-36.
Poole AM, Jeffares DC, and Penny D. (1998 Jan). The path from the RNA world. J Mol Evol , 46, 1-17.
Wiegand TW, Janssen RC, and Eaton BE. (1997 Sep). Selection of RNA amide synthases. Chem Biol , 4, 675-83.
Di Giulio M. (1997 Dec). On the RNA world: evidence in favor of an early ribonucleopeptide world. J Mol Evol , 45, 571-8.
Hager AJ, and Szostak JW. (1997 Aug). Isolation of novel ribozymes that ligate AMP-activated RNA substrates. Chem Biol , 4, 607-17.
James KD, and Ellington AD. (1997 Aug). Surprising fidelity of template-directed chemical ligation of oligonucleotides [In Process Citation] Chem Biol , 4, 595-605.
Lohse PA, and Szostak JW. (1996 May 30). Ribozyme-catalysed amino-acid transfer reactions. Nature , 381, 442-4.
Lazcano A, and Miller SL. (1996 Jun 14). The origin and early evolution of life: prebiotic chemistry, the pre- RNA world, and time. Cell , 85, 793-8.
Ertem G, and Ferris JP. (1996 Jan 18). Synthesis of RNA oligomers on heterogeneous templates. Nature , 379, 238-40.
Robertson MP, and Miller SL. (1995 May 5). Prebiotic synthesis of 5-substituted uracils: a bridge between the RNA world and the DNA-protein world [see comments] Science , 268, 702-5.
Robertson MP, and Miller SL. (1995 Jun 29). An efficient prebiotic synthesis of cytosine and uracil [published erratum appears in Nature 1995 Sep 21;377(6546):257] Nature , 375, 772-4.
Breaker RR, and Joyce GF. (1995 Jun). Self-incorporation of coenzymes by ribozymes. J Mol Evol , 40, 551-8.
James KD, and Ellington AD. (1995 Dec). The search for missing links between self-replicating nucleic acids and the RNA world. Orig Life Evol Biosph , 25, 515-30.
Bohler C, Nielsen PE, and Orgel LE. (1995 Aug 17). Template switching between PNA and RNA oligonucleotides [see comments] Nature , 376, 578-81.
Connell GJ, and Christian EL. (1993 Dec). Utilization of cofactors expands metabolism in a new RNA world. Orig Life Evol Biosph , 23, 291-7.
Nielsen PE. (1993 Dec). Peptide nucleic acid (PNA): a model structure for the primordial genetic material? Orig Life Evol Biosph , 23, 323-7.
Lahav N. (1991 Aug 21). Prebiotic co-evolution of self-replication and translation or RNA world? J Theor Biol , 151, 531-9.
Ekland EH, Szostak JW, and Bartel DP. (1995 Jul 21). Structurally complex and highly active RNA ligases derived from random RNA sequences. Science , 269, 364-70.
I did. It doesn't change what I wrote in my post.
There is a lot of discussion of reaction speeds, accuracy, etc. in several journals. (I don't have access to the titles right now.) The operations research people spend a lot of time trying to optimize things which have diverse criteria to be optimized; their journals might have some interesting ideas. The biology journals and a math journal "Journal of Evolutionary Equations" (I did remember one) also cover the subject.
1. a hypersonic round is more accurate within its range than a subsonic round of the same mass
2. in machining (turning or milling) there is a range of optimal speeds, feeds, and angles for each kind of material for removing the desired chip profile and producing the desired surface on the workpiece. Too slow is just as bad as too fast.
you'd be surprised how often non-bio chemists get confused by the (lack of) performance of enzymes outside of narrow temperature bands :)
Well, maybe because their particular behavior is a direct result of their respective properties?
If they showed a different behavior and other regularities in their interactions they'd have a different set of properties altogether.
Why do they act according to these laws? (and yes, I full well understand that you feel "law" is a misnomer)
As I said above, if they "acted" according to other laws (i.e. showed other regularities in their interactions) they'd have different properties. "Laws" are derived from these properties. Just why is this so hard to understand?
Now why does the universe and all that it contains has these properties and no others? Well, I don't know. Maybe our universe is just one out of many, each with a different set of properties or maybe this set of properties is the only one (or one of a few others) that produces stable universes. On the other hand our universe may also be a science project of a being from an other dimension who made it the way it is because other configurations didn't yield interesting results.
So maybe one of the above scenarios is true or maybe none of them but whatever the reasons for the properties of our universe are, they have no influence on it's behavior.
Whether these properties were intelligently designed or not doesn't matter. As long as they are the same you won't notice any difference and you'll observe the same regularities in each case.
Because, as I said above, I see no compelling reason to assume design in the first place if I don't know exactly how something "came about", especially if it doesn't resemble any artifacts made by designers that are known to us (e.g. humans) and it looks as if it is the product of some long and messy natural process such as evolution.
Complexity is not necessarily the result of intelligent design. Usually it is the other way around since an intelligent agent should design a system as simple as possible and not unnecessarily complex.
Of course you can always postulate a designer who, for mysterious reasons, inscrutable purposes and with unknown methods, made all living things to look as if they evolved from a common ancestor but such an hypothesis doesn't survive Occam's Razor.
If you accept such an hypothesis you can as well accept the one where the Designer made everything Last Thursday and be done with it.
If you're going where I think you are with this, I did not say I required a photograph; I said that was a type of evidence I would accept.
You got it BACKWARDS!!
Then a miracle happened, and females appeared.
Uh... I was asking GREAT minds to respond,
some thT MAY not HAVE BEEN AROUND TWO YEARS AGO........
Look out your window......
Is this something that's verboten here on FR?
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