tgamble

ICR (which as everyone knows ia highly respected scientific organization ) has (predictably) a few things to say on the famous Miller/urey experiment. I was just wondering how accurate their claims were. Specifically their comments on

[QUOTE]But while oxygen is essential for life's continuance, oxygen destroys non-living organic molecules (the building blocks of life) at a much faster rate than they could possibly form. Thus, it is assumed in origin-of-life scenarios, that Earth's early atmosphere was a "reducing" atmosphere with no free oxygen ("oxidizing").

In 1953, University of Chicago graduate student, Stanley Miller, working with Nobel Prize Laureate Harold Urey, simulated what they proposed was the make-up of the early atmosphere in a brilliantly conceived laboratory experiment. This "reducing" atmosphere contained hydrogen (H), methane (H+C), ammonia (H+N), and water vapor (H+O), but no free oxygen. By sending an electric spark (simulating lightning) through the mixture they succeeded in producing some simple amino acids, the building blocks of life and other organic compounds, and claimed a great triumph for evolution. This concept continues to be propagated today in "every" textbook and is used in support of the evolutionary, naturalistic way of thinking.
[QUOTE]

as well as his comments on what the experiment produced.
@@@.icr.org/pubs/btg-b/btg-152b.htm

thanks!

MrDarwin

I'm no expert in the field, but I believe that part quoted is more or less accurate. Assuming that earth's early atmosphere had little or no free oxygen was a good assumption, since virtually all the free oxygen in the atmosphere today comes from biological sources, i.e., photosynthesis. But when they go on to say

it's a bit misleading, because (a) the early atmosphere certainly had far less free oxygen than the modern atmosphere; (b) just because there is some free oxygen doesn't mean the atmosphere can't be reducing, it just won't be strongly reducing; (c) there may have been oxygen "sinks" (e.g., iron) that rapidly pulled any free oxygen out of the atmosphere as soon as it appeared; and (d) the atmosphere may well have had free oxygen, but there may have been localized earthly environments (e.g., ocean depths) that had little or none.

Quetzal

More than a "bit misleading". Although I can't find the damn citation right now, there is geological evidence that the O2 content of the early atmosphere was limited based on the presence of ferrous iron (non-oxidized) in the earliest basement rocks from Greenland (I think). If Patrick's around, maybe he remembers the reference.

[Edited to add: And besides, Urey-Miller isn't the only abiogenesis scenario. I can think of at least two others that don't even CARE how much O2 was in the early atmosphere.]

[ April 17, 2002: Message edited by: Morpho ]</p>

Dr.GH

From your web link:

Starting conditions:

The last living, fully employed scientist who argues for an early oxic atmosphere is Hiroshi Ohmoto. His best argument is presented here:

Ohmoto, H.
1997 “When Did the Earth’s Atmosphere Become Oxic?” The Geochemical News, 93:12-13, 26-27.

It was strongly answered by

Holland, Heinrich D.
1999 “When did the Earth’s atmosphere become oxic? A Reply.” The Geochemical News #100: 20-22

After that, Ohmoto and his students have backed off to a 3.5 Ga oxic environment. This is still a bit early in my opinion, but allows ample time for prebiotic synthesis of organic compounds and the origin of life. Sheesh, one billion years? Come on. 1,000,000,000 years!

My origins bibliography is over 10 pages now. I have no idea when I'll finish the review. I think I'll go fishing Thursday, and work at the museum Friday through next Tuesday.

Later you all.