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Murchison Meteorite Still Contentious
An anonymous reader writes "The well-known 1969 meteorite that fell 60 miles north of Melbourne, Australia, remains remarkably contentious today. The 100 kilogram carbon rock : a) contains pre-biotic proteins and 12% water; b) harbors 50 amino acids not found on Earth; c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses. While terrestrial contamination (even interior to the meteor) may discount this so-called 'Murchison meteor', its light isotopes of carbon and nitrogen suggest the left-handed amino acids not found elsewhere on Earth have the same ratios as the right-handed ones. This would not be the case if, say, bacteria was just making the left-handed ones after impact. Seems quite a controversy from down-under."
Guess the DNA spiral the other way just like the water in the toilet down under. ;)
And chunks of it are now on sale at Ned Flander's Leftorium.
Fan-diddly-tastic!
I m just a simple caveman, your fire scares me. These pre-biotic proteins you speak of are unfamiliar to me!
So if the big debate is whether these "rocks" from space contain the building blocks of life, but are being contaminated when they hit earth. Why don't we send up a robot (Or what have you) into space and collect some rocks that have not been on earth?
To me, if you collected about 20 or 30 of these things, it would answer the question rather quickly. Yes, I know that does mean we would get rocks with ammo acids, but sitting waiting for the rocks to come to us seems to be a waste of time.
Linux O Muerte!
How would organic material from earth make it into the center of an object like this? Can the force of the impact explain that some how? Just want to know : )
I am a viral sig. Please help me spread.
Perhaps even more interesting (especially if you're already familiar with the debate) is the fact that highlighting a word or phrase on that page causes a browser window to pop up with the results of a Google search on that word or phrase...
Not technically very difficult, but a cool idea...
.....compared to random or racemic mixtures found in test tubes on Earth. We have yet had no other "lab" from which to study life and it's building blocks (life as we know it: carbon based and mostly made of water). Therefore, the sudden appearence of such components from the stars might very well appear to be "based on dominant left-handed chirality" when compared to the billions-old formula we have here on our planet.
We also don't know how the environment of space will effect amino acids contained in the rock. Since these amino acids (and other material) are foreign, then how do we know that it isn't natural for them to be collected in such a manner?
Never forget the scientific method. You have to ask questions. After you're done asking questions, submit to your peers for them to ask questions.
It really isn't compelling at all. It's similar to how UFOlogists focus on half truths and anamolies that confirm their theories, while ignoring the evidence that shows how 90-95% of all sightings are reasonably explained (the tons of disconfirming evidence). They also turn their nose up to the community and the world, effectively becoming the closed-minded character that they try to call the real scientists: Real scientists submit their work to thousands of peers and accept feedback and analysis. Psuedoscientists do not, and yet they call the critical thinkers that reject their ideas closed-minded.
OK, rant over.
From the article: A curious aspect of Earth's life forms is that they contain (with few exceptions) only left-handed amino acids. In contrast, when scientists synthesize amino acids from nonchiral precursors, the result is always a "racemic" mixture - equal numbers of right- and left-handed forms. Scientists have been unable to perform any experiment that, when starting with conditions believed to emulate those of early Earth, results in a near-total dominance of left-handed amino acids, says George Cody, a geochemist at the Carnegie Institute of Washington.
In many cases, the levorotary forms are lower energy structures and would be favored during synthesis. The fact that many L based systems are almost exclusively so is dependant upon the larger structures that are based upon amino acids and other small molecules. Often a D form of a molecule will not be able to integrate into a L structure.
This is not to say that D forms cannot have biological activity however as there are many instances I can think of where racemic mixtures of molecules can have biological activity. For instance, the 2 chiral forms of carvone have completely different smells due to receptors in the olfactory epithelium being activated by each of the racemic forms.
Some instances of similarity of molecular structure but different chirality have also resulted in catastophies. One only has to think of MPTP poisoning the neurons of the substantia nigra or potentially thalidomide.
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here's a couple of reasons I can think off the top of my head:
1) we've got to get the ship someplace where there are "space rocks". a low-earth orbit really isn't going to accomplish that - you'd have to go to the asteroid belt for a ready supply. that's not easy. or, conversly, you land someplace where rocks may have accumulated (ie, the moon, mars).
2) if you send a ship to a place with lots of space rocks, the ship is going to get hit by a lot of space rocks. shielding becomes a problem.
3) if you land some place, you're stuck getting rocks next to where you land (like viking) or you've got to build a way to move around (like pathfinder)
4) building a reliable, completely automated assay for amino acids is not trivial. if it's mobile, that's going to be even less trivial.
"How many times will science have a victory over the church before we can finally kill God for good?"
What victory over the church? Science is good for proving that things exist, but it's not very useful for proving that things don't exist. If you're drawing the conclusion that God doesn't exist by what is or isn't on a meteorite, then you're not using science.
This is slashdot, so you're expecting to nod knowingly and pretend you understand it. Or do you really think all those people who discuss quantum mechanics at length really know what they're talking about?
Case closed and make mine a Foster's. G'day.
Sigs are bad for your health.
c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses.
If a molecule has a carbon with 4 different groups bonded to it then there are two different ways of making the same thing but with different physical layouts eg:
W
|
X -C- Y
|
Z
Or:
X
|
W -C- Y
|
Z
Basicaly these have a "non superimposable mirror image" (no matter how much you rotate them and you can never have all the x,y,x and z's lined up)
Generaly the left handed and right handed molcules have very quite different behaviours, for instance some drugs use only one of the versions, whilst the other version is a poision.
A racemic mixture is a mixture of 50-50 of the left handed and right handed molecules, and generaly chemical processes will produce a racemic mixture.
Fact: the meteorite contains ammino acids, and chirality that is not generally found in terrestrial organisms.
Fact: This meteroite is HEAVILY polluted with terrestrial organic matter.
Conclusion: While ammino acids are generated in space, they seem to mimic the compositions found when we try to synthesize them in the lab.
Aside: You can produce the same results with some methane gas, water vapor, and ionizing radiation.
Move along, no controvesy here.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
amino acids not found elsewhere on Earth
Read it again, slowly.
It doesn't say "amino acids that do not exist elsewhere on Earth."
Simply that they haven't been found elsewhere, including, I assume, on rocks near the impact crater.
Recent research suggests that there is an excess of L-amino acids (the specific enantiomer used in life-proteins) found in space, suggesting that the chiral specific process involving circular polarized light (mentioned in the article) could have lead to the amino acids that were found on the Murchison (and other meteorites).
...
From the article:
Recently it has been discovered that an excess of L-amino acids is present in the Murchison and Murray meteorites indicating that a preference for L-amino acids existed in solar system material before there was life on Earth. This supports an idea, first proposed by Rubenstein et al. (1983, Nature 306, 118), for an extraterrestrial origin for homochirality.
In this model the action of circular polarized light on interstellar chiral molecules introduced a left handed excess into molecules in the material from which the solar system formed.
If our own solar system formed in such a region of high circular polarization, it could have led to the excess of L-amino acids which we see in meteorites and to the homochirality of biological molecules. It is possible that without such a process operating it would not be possible for life to start. This may have implications for the frequency of occurrence of life in the universe.
otherwise they would be sitting in a detention centre right now appealing their refusal of refugee status by the Australian Gumment. Bloody alien queue jumpers will not be tolerated.