Coragyps

Dozens and dozens. Miller's group is still doing some of them, and publishing in PNAS, as best I remember. Wachtershalter (sp?) is another name to look for in that field.

Dr.GH

The problem can be broken down into several stages.

First is the question of what the early earth was like geochemically. The OOL period is from the accretion 4.5 Ga to well known fossils 3.5Ga.
sub stages: the initial (solar) atmosphere
hydrogen (and other gas) loss mechanisms
the geochemical reactions producing gases
meteor/comet contributions (including lunar)
mantle/crust mixing
ocean chemistry

Creationists like Jon Wells like to claim that the Hadean and early Archean oceans and atmosphere were not reducing and that this makes the abiotic formation of complex carbon compounds, such as amino acids, impossible. There are two approches, but the easiest is the following:

Holland, Heinrich D.
1999 “When did the Earth’s atmosphere become oxic? A Reply.” The Geochemical News #100: 20-22 (see Ohmoto 1997 )

which eliminated Ohmoto's argument for an early oxygenated earth.

Ohmoto, H.
1997 “When Did the Earth’s Atmosphere Become Oxic?” The Geochemical News, 93:12-13, 26-27. (see Holland 1999)

So we had a reduced earth, and who cares why. The alternate is to look further into why the earth was reduced. This approach leads to the happy result that even if the majority of the earth was even neutral, there would be significant "oasis" of hightly reduced gasses and fluids. This sets up the hydrothermal vent environments. There are a number of advantages to this scenario.

Hydrothermal vents can be production centers of complex carbon compounds.

Amend, J. P. , E. L. Shock
1998 “Energetics of Amino Acid Synthesis in Hydrothermal Ecosystems” Volume 281, number 5383, Issue of 11 Sep , pp. 1659-1662.

Blochl, Elisabeth, Martin Keller, Gunter Wächtershäuser , Karl Otto Stetter
1992 “Reactions depending on iron sulfide and linking geochemistry with biochemistry” PNAS-USA v.89: 8117-8120

BRANDES, JAY A., NABIL Z. BOCTOR, GEORGE D. CODY, BENJAMIN A. COOPER, ROBERT M. HAZEN & HATTEN S. YODER JR
1998 Abiotic nitrogen reduction on the early Earth Nature 395, 365 - 367

Cody, George D., Nabil Z. Boctor, Timothy R. Filley, Robert M. Hazen, James H. Scott, Anurag Sharma, Hatten S. Yoder Jr.
2000 “Primordial Carbonylated Iron-Sulfur Compounds and the Synthesis of Pyruvate” Science v.289 : 1337-1340

Horita, Juske, Michael E. Berndt
1999 Abiogenic Methane Formation and Isotropic Fractionization Under Hydrothermal Conditions. Science 285 (5430): 1055

Huber, Claudia, Gunter Wachtershauser
1997 “Activated Acetic Acid by Carbon Fixation on (Fe,Ni)S Under Primordial Conditions” Science v. 276: 245-247

Huber, Claudia, Gunter Wachtershauser
1998 “Peptides by Activation of Amino Acids with CO on (Ni,Fe)S Surfaces: Implications for the Origin of Life” Science v.281: 670-672

Imai, E., Honda, H., Hatori, K., Brack, A. and Matsuno, K.
1999 “Elongation of oligopeptides in a simulated submarine hydrothermal system“ Science 283(5403):831–833.

So now we have plenty of amino acids produced on earth. But there are also extraterrestrial sources:

BERNSTEIN, MP, JP DWORKIN, SA SANDFORD, GW COOPER &
LJ ALLAMANDOLA
2002 Racemic amino acids from the ultraviolet photolysis of interstellar ice analogues. Nature 416, 401 - 403 (2002)

Cooper, George, Novelle Kimmich, Warren Belisle, Josh Sarinana,
Katrina Brabham, Laurence Garrel
Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth. Nature 414, 879 - 883 (20 Dec 2001)

Dworkin, Jason P., David W. Deamer, Scott A. Sandford, and Louis J. Allamandola
2001 “Self-assembling amphiphilic molecules: Synthesis in simulated interstellar/precometary ices” PNAS 98: 815-819

Ehrenfreund, Pascale, Daniel P Glavin, Oliver Botta, George Cooper, Jeffrey L. Bada
2001 “Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of CI type cabonaceous chondrites” PNAS-USA v.98 no.5:2138-2141

Engel, M. H., S. A. Macko
1997 Isotopic evidence for extraterrestrial non- racemic amino acids in the Murchison meteorite. Nature 389, 265 - 268 (18 Sep)

MUÑOZ CARO, GM, 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

Pizzarello, Sandra, Yongsong Huang, Luann Becker, Robert J. Poreda, Ronald A. Nieman, George Cooper, Michael Williams
2001 “The Organic Content of the Tagish Lake Meteorite” Science, Vol. 293, Issue 5538, 2236-2239, September 21, 2001

Sephton, Mark A.
2001 Meteoritics: Life's sweet beginnings? Nature 414, 857 - 858 (20 Dec )

Whitby, J., R. Burgess, G. Turner, J. Gilmore, J. Bridges
2000 “Extinct I-291 in Halite from a Primitive Meteorite: Evidence for Evaporite Formation in the Early Solar System” Science 288: 1819-1821

So, plenty of amino acids all around, including the Miller/Urey mechanism. We still need sugars, and lipids (note that a few sugar sources were mentioned above). It turns out there are plenty of those as well, but I need to do a few other things just now.