Joined: Oct. 2015
|Quote (Dr.GH @ Nov. 18 2015,18:53)|
|Quote (Otangelo @ Nov. 18 2015,10:54)|
|Quote (NoName @ Nov. 18 2015,12:23)|
|Why is abiogenesis impossible?|
There are many reasons. I will post a small list to begin with:
1. In Miller’s experiment he was careful to make sure there was no oxygen present. If oxygen was present, then the amino acids would not form. However, if oxygen was absent from the earth, then there would be no ozone layer, and if there was no ozone layer the ultraviolet radiation would penetrate the atmosphere and would destroy the amino acids as soon as they were formed. So the dilemma can be summed up this way: amino acids would not form in an atmosphere with oxygen and amino acids would be destroyed in an atmosphere without oxygen.
Miller was using the atmospheres of the other Solar System planets known by spectrographic analysis. This was his professor Harold Urey's hypothesis. Charles Darwin's idea was that the origin of life was in a reducing environment because the decomposition products of tissues were reduced. He was incorrect, Urey was correct.
You clearly have no experience in chemistry.
Matthew A. Pasek, Jelte P. Harnmeijer, Roger Buick, Maheen Gull, and Zachary Atlas
2013 "Evidence for reactive reduced phosphorus species in the early Archean ocean" PNAS 2013 ; published ahead of print June 3, 2013, doi:10.1073/pnas.1303904110
Colin Goldblatt, Timothy M. Lenton and Andrew J. Watson
2006 "Bistability of atmospheric oxygen and the Great Oxidation" Nature 443, 683-686 (12 October 2006) | doi:10.1038/nature05169
Manfred Schidlowski, Peter W. U. Appel, Rudolf Eichmann and Christian E. Junge
1979 "Carbon isotope geochemistry of the 3.7 × 109-yr-old Isua sediments, West Greenland: implications for the Archaean carbon and oxygen cycles" Geochim. Cosmochim. Acta 43, 189-199
Zahnle, Kevin, Laura Schaefer and Bruce Fegley
2010 “Earth's Earliest Atmospheres” Cold Spring Harbor Perspectives in Biology
Ozone with a reducing atmosphere;
Noll KS, Roush TL, Cruikshank DP, Johnson RE, Pendleton YJ.
1997 “Detection of ozone on Saturn's satellites Rhea and Dione. “ Nature 1997 Jul 3;388(6637):45-7
Additionally, UV shielding would only be needed in continental terrains;
Sagan, Carl, Christopher Chyba
1997 “The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases” Science v. 276 (5316): 1217-1221
E. T. Wolf and O. B. Toon
2010 “Fractal Organic Hazes Provided an Ultraviolet Shield for Early Earth” Science 4 June 328: 1266-1268 [DOI: 10.1126/science.1183260]
Watanabe, Y., Martini, J.E.J., Ohmoto, H.
2000 “Geochemical evidence for terrestrial ecosystems 2.6 billion years ago.” letters, Nature, 408, 574-578 (2000). (terrestrial bio by 2.6 to 2.7 Ga implies sufficient O2 for an biogenic Ozone UV shield)
But, an even better UV shield is ice. And, Ice is an excellent location for several key chemical steps;
Cleaves, H. James, Stanley L. Miller
1998 “Oceanic protection of prebiotic organic compounds from UV radiation” PNAS-USA v. 95, issue 13: 7260-7263
Bada, Jeffrey. L., C. Bigham, Stanley L. Miller
1994 “Impact melting of frozen oceans on the early Earth: Implications for the origin of life” PNAS-USA v.91: 1248-1250
BERNSTEIN, MP, JP DWORKIN, SA SANDFORD, GW COOPER &
2002 "Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues" Nature 416, 401 - 403 (2002)
Attwater, J., Wochner, A., & Holliger, P.
2013 "In-ice evolution of RNA polymerase ribozyme activity" Nature chemistry, 5(12), 1011-1018.
Bernstein, M. P. et al.
1999 "UV irradiation of polycyclic aromatic hydrocarbons in ices: Production of alcohols, quinones, and ethers" Science 283, 1135–1138
Blank, J.G., Gregory H. Miller, Michael J. Ahrens, Randall E. Winans
2001 “Experimental shock chemistry of aqueous amino acid solutions and the cometary delivery of prebiotic compounds” Origins of Life and Evolution of the Biosphere 31(1-2):
GM MUÑOZ CARO, UJ MEIERHENRICH, WA SCHUTTE, B BARBIER, A ARCONES SEGOVIA, H ROSENBAUER, WHP THIEMANN, A BRACK & JM GREENBERG
2002 "Amino acids from ultraviolet irradiation of interstellar ice analogues" Nature 416, 403 - 406 (2002)
Miyakawa S, Cleaves HJ, Miller SL.
2002 "The cold origin of life: B. Implications based on pyrimidines and purines produced from frozen ammonium cyanide solutions" Orig Life Evol Biosph. 2002 Jun;32(3):209-18
Cleaves HJ, Nelson KE, Miller SL.
2006 "The prebiotic synthesis of pyrimidines in frozen solution" Naturwissenschaften. 2006 Mar 22
And, the final nail in this particular creationist fraud is that abiotic amino acid synthesis can happen in the presence of oxygen;
Cleaves, H. James, John H. Chalmers, Antonio Lazcano, Stanley L. Miller, Jeffrey L. Bada
2008 “A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres” Orig Life Evol Biosph (2008) 38:105–115
So, to review; the Miller/Urey hypothesis was confirmed; the UV "problem" was not a problem.
|The early earth had a reduced atmosphere. We know this in several ways. The most significant is geological data.|
I don't think so.
Even at ca 3.2 Ga, thick and widespread kerogenous shales are consistent with aerobic photoautrophic marine plankton, and U–Pb data from ca 3.8 Ga metasediments suggest that this metabolism could have arisen by the start of the geological record. Hence, the hypothesis that oxygenic photosynthesis evolved well before the atmosphere became permanently oxygenated seems well supported.
"Ominously, for believers in the traditional organic soup scenario, there is no clear geochemical evidence to exclude the possibility that oxygen was present in the Earth's atmosphere soon after the formation of its crust."
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.
Harry Clemmey and Nick Badham, “Oxygen in the Precambrian Atmosphere: An Evaluation of the Geological Evidence,” Geology, 10, no. 3, (March 1982): 141.