ashibaka

Now they've polluted a perfectly good name for a science! We'll have to call investigations into the heterotroph hypothesis "beginning-of-life science" or something like that. Who said Creationists don't hurt the scientific community?

Coragyps

It wouldn't, but there has been some work on the effect of circularly polarized light on inducing handedness in such. I'll try to dig up a citation, but probably not 'till late this week - I'll be off for a couple of days.
Just speculating, it might be just as simple to posit selective destruction of one enantiomer as selective formation of the other. Also, the handedness of the, say, amino acids produced from hydrogen cyanide doesn't arise until the initial product reacts with water. If that reaction were in a dissymetric environment, you could get dissymetric product.
And here I am, acidizing oil wells when I coulda been in astrobiology.......

lpetrich

As to the molecule-handedness problem, I think that which handedness was "chosen" is purely accidental, though the "choice" may have been a result of some molecular asymmetry being more efficient than complete molecular symmetry.

This is because (1) the electromagnetic interaction makes no distinction and (2) while the weak interaction does, there is not enough of it to make much of a difference.

Direct weak interactions would be by way of electrons and nuclei interacting by way of the Z particle in addition to its electromagnetic interaction. The strength of this effect is approximately (me*alpha/mZ)^2 or 10^-16 of typical atomic-electron energies.

Indirect weak interactions would be by way of beta decay, which emits polarized electrons; their spin is along their direction of motion. However, this is a rather inefficient mechanism for producing handedness, causing something like a few percent difference. Also, the beta decays have to take place within close proximity of the Primordial Soup in order to affect it.

The average heating of the Earth about 4 billion years ago was around 10^-13 watts/cm^3, or about 1 decay/cm^3 (assuming ~ 1 MeV/decay). However, 1 cm^3 of water contains about 3.3*10^22 water molecules!

Having handled fundamental physics, I now turn to some purported observations.

The next question is what accounts for molecular asymmetries in meteorites. I think that that is the result of contamination by stray Earth bacteria and consumption of some of the organic material by them.

Contamination by Earth bacteria is a real possibility. Carl Sagan noted in Intelligent Life in the Universe, IIRC, that among the bacteria found in one meterorite was a facultative anaerobe -- one that could utilize oxygen in its metabolism. That meant Earthly contamination to him, since in all the Solar System only the Earth has a big supply of free oxygen.

[ June 09, 2002: Message edited by: lpetrich ]</p>

madmike

Heres your first problem, Stanley Miller. Great man, bad experiment. What you don't see is his many failed attempts at creating amino acids. It wasn't until he correcly callculated the necessary chemicals to create such amino acids, that he got the results he was "looking" for. These experiments were pre-determine to have a certain outcome.

Second problem

Sidney fox's experiments were extremely different from Miller's. Millers were in a "soup", fox's were in a hot dry place. This is contradictory to Millers experiments. Amino acids break apart easily in liquid, Cell Biology 101!

"Some Gases", not the way it works. The correct amount of gases and conditions. Miller predetermined what chemicals were needed for his experiment.

Hayden

Yeah, okay, but he still proved that amino acids can be created from non-organic materials. Whether or not he waited around for the correct combination of gases to occur is immaterial, isn't it?

(I'm a layman in this field)

Just to pre-empt any probability discussions, please bear in mind that if the chances of the correct combination of gases appearing naturally over a given period of time (e.g. a year) is 1:1000000, then in 1000000 units (a million years) it actually becomes quite likely.

Just my thoughts.
HR

madmike

HR

The problem lies in the fact that amino acids and proteins are formed in completely different conditions. Amino acids don't group together just because there amino acids. A new set of conditions would have to arise very shortly after amino acids appeared. This doesnt agree with darwinian evolution of slight modification. All these conditions happening at the same to produce a protein is just about zero. Then there are about 14 proteins needed to make one living cell, which a cell has many features that are irreducibly complex meaning all the parts have to be present at one time for the system to work.

This leads me to believe that proteins or cells couldn't just arise out of a primordial soup, or whatever you want to call the beginning.

Hayden

So, not zero. Therefore, not impossible. Extremely improbable, yes, but over an infinite period of time extremely improbable events are quite probable.

HR

lpetrich

Madmike, why do you think that Harold Clayton Urey and Stanley Miller had rigged their pioneering prebiotic-chemistry experiments?

Be specific. Point to specific, documented actions that these gentlemen had performed.

beausoleil

Of course the researchers thought of this. The amino acids in question include some not used by life on earth, as I recollect. I don't know any seroius researcher who believes bacteria found in meteorites are anything but terrestrial comtamination - it's the organics that are in question. Some of them are clearly non-terrestrial, based on their isotopes.

There was a hoohah back in the 60s about so-called bacteria found in a carbonaceous chondrite, but it turned out to be pollen, I think.

Coragyps:

I've seen various theories to account for an enantiomeric excess in astrochemical organics; circularly polarised radiation from a passing neutron star or polarisation of stellar light by aligned dust grains. Both of them struck me as a little ad hoc, but maybe that's inevitable. I was curious if you had anything more convincing.

Don't be too cut up about missing a vocation. At least there is oil - astrobiology presently seems to be a field without anything to study!

RufusAtticus

Be more specific. My Organic Chemistry, 3E by Wade gives four methods to make amino acids: reductive amination, amination of an alpha-halo acid, Gabriel-Malonic ester synthesis, and Strecker Synthesis. Most of these appear to be used in industry, but they show that there is more than one way to make an amino acid.

The formation of a peptide bond is nothing special. It's just a condensation reaction that produces an extra water molecule.

Since when is evolution a part of the equation? You appear to be the only one entertaining that the chemical reactions of peptide synthesis are under the processes of "Darwinian evolution."

Please show your calculations.

Only creationists claim that a fully formed cell should be the product of abiogenesis. There are also many ways for evolutionary process and other things to produce irreducible complexes. Thus your complaints are ignorable.

It appears that you have been convinced that a straw man is not possible. Good. How about what science actually says? The significance of the Urey-Miller experiment was not that it showed how life originated, but that it showed that amino acids can be produced without the aid of cellular machinery.

Since we are discussing origins, how much do you know about the RNA world?

~~RvFvS~~

[ June 10, 2002: Message edited by: RufusAtticus ]</p>