Murchison Meteor Questions

Hi Rob,
You are certainly correct that the implication of the discovery of adenine in meteorites can be overstated. Carbonaceous chondrites are a fairly poor source of organic compounds on the surface of the early Earth. See, for instance,
http://www.springerlink.com/content/d0013w72562v0214/?p=5...
which is a just-published article in Origins of Life and Evolution of Biospheres, and is definitely a paper I have a vested interest in (seeing as I'm the first author ). The abstract should be publicly available, at the very least. Unfortunately, I can't quite give out .pdfs as there are copyright issues.However, as RAZD has explained in part, the extraction of adenine by formic acid and water from Murchison is not equivalent to the formation of adenine in an artificial laboratory setup. Consider the following:Adenine is sparingly soluble in water. In life, adenine is made a factor of 100-1000 times more soluble by the addition of ribose and phosphate. This increases the solubility of adenine as an adenosine nucleotide substantially. Thus water extracts of this material are already fighting an up hill solubility battle.Next, insoluble organic matter/tar is the major carrier of carbon in the Murchison meteorite. This material is quite similar chemically and structurally to adenine, and is bound to mineral particles. Adenine is highly "soluble" in this material. Hence, trying to force it from the insoluble matter into the aqueous phase (e.g., from something it likes being in to something it doesn't like being in) is very difficult. The difficulty in solubility has been compounded by the chemical extraction procedures. Here's a statement from Glavin et al. 2006: However, these results are not equivalent to experiments critiqued by Shapiro and Behe. Formic acid solutions were employed to extract adenine since adenine is a nucleobase, and an acid solution is necessary to fight the compounded difficulty of insolubility in water and solubility in the insoluble organic matter. Adenine is by my quick estimate, a factor of 10^6 more soluble in the formic acid solution than in water alone. It's no wonder that it's hard to spot in the water extracts.Note that the work done on carbonaceous chondrites only proves one thing: That organic compounds of biologic relevance are formed through abiotic processes. These organic compounds are clearly formed through abiotic processes as 1) they have D/H, C13/C12, and N15/N14 ratios consistent with extraterrestrial material and not consistent with terrestrial material, 2) there is not a major handedness to these molecules (both forms are produced in ratios ~50:50, or at most 40:60), and 3) there is a host of decidedly non-biologic organic compounds also detected in extracts.Some origins of life researchers sloppily conclude that meteorites were the ultimate source of these organic compounds. They are wrong. Other extraterrestrial material (interplanetary dust particles, comets) may be a better source, but they've been much less studied, mainly due to lower amounts of samples. The implications from these meteorite studies are primarily that biologic organics can be formed from non-biologic processes. Placed in the greater context of this work, meteorites confirm some of the potentially prebiotic experiments, at least in part.