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."

Comments

Relevance?

[Vardan]

You'd think that after they found what appears to be microscopic life (fossilized, rather) on Mars, it wouldn't be that big of a stretch.

However, it is fairly interesting that that many amino acids are left-handed. Organic molecules tend to form in pretty much the same way in any given environment, so I'd think that if those aminos ARE from Earth, they'd be from someplace strange, like a hydrothermal vent. How they would've gotten onto a meteor from there, who knows.

Re:Relevance?

[stratjakt]

Except that the 'fossilized microbes' on the martian meteor can be completely dismissed by natural (non-organic) processes.

I dont know enough about blingblongology to elaborate, I can merely regurgitate what I've learned watching 'UFO week' on the history channel.

(Rant: WTF do UFOs, Loch Ness monster, bigfoot or Ghosthunting have to do with history?!)

Re:Relevance?

[kavau]

so I'd think that if those aminos ARE from Earth, they'd be from someplace strange, like a hydrothermal vent. How they would've gotten onto a meteor from there, who knows.

How about this: 10 billion years ago a gigantic asteroid hits earth, sending countless fragments of terran rock into space, many of them harbouring life in its early stages. Now, billions of years later, one of those galactic pieces of rubble happens to cross earth's path again. Hence the amino acids we found might be from earth's own past...

Just a thought...

Re:Relevance?

[joethebastard]

Meteoritics is a messy science, because measurements are never conclusive and explanations are always at least partially guesses. To analyze the chirality of the amino acids, you measure how much light it absorbs of different polarizations (circular dichroistic spectroscopy). To measure absorption, you must cut a thinsection; cutting something open always introduces contaminants. Explaining the chirality, once measured, is just as tricky- most scientists would just look at the excess of left-handed acids as proof of contamination.

Isotopic data is even worse- it's easy to show some difference in a sample, as isotopes on this planet tend to be extremely isotropic, but proving anything with that is difficult. Amino acids make up a small percent of the sample of a chondrite, so the number of particle counts representing (from a secondary ion mass spectrometer, or similar device) them will be fairly low; this makes the relative error very high. Every bit of processing done on the sample introduces terrestrial atoms, and a spectrometer calibrated to look at specific atom masses won't know the difference between nitrogen from a meteorite's amino acid or from a hamster. How do you attach the isotopic excesses to the left-handed chiral amino acids?

All this just to say: take meteoritics with a grain of salt. Every time I work in a meteorite lab, I take their claims a bit less seriously. It's a really cool, wonderfully hard area of science, but you have to deal with largely destructive and oft imprecise analytical techniques on a limited number of samples, all of which have been partially processed or contaminated.... with never enough funding. This group is doing a good job, but rarely in this field is any result ever conclusive.

Let me ask this...

[Mullen]

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.

Re:Let me ask this...

[odyrithm]

but sitting waiting for the rocks to come to us seems to be a waste of time.

erm... how exactly do we catch them would you suggest? pretty nippy little fuckers when there streaking at about 100k miles a second through space..

never heard of this....

[morgajel]

wow, this is really interesting... I've never heard of this meteor before, however I find this really cool.
I wonder why this was never mentioned in any of my chemistry, physics, geology, or biology classes in high school or college (last 10 years)?

on a side note... is anyone else creeped out by the picutre of the guy halfway down the page?
*shudder*

Don't get too excited yet.

[Sheetrock]

Earth bourne bacteria could express pre-biotic proteins similar to those discovered in the presence of the right catalysts. Chirality studies can be misleading; nearly 50% of a random sampling of biotic material will confirm the existence of left-handed biotes without revealing anything at all about the total material. Additionally, I'd disagree with the position that the presence of light isotopes in the left-handed chiratic samples in and of itself discounts the possibility that the amino acids were created by Earth bacteria.

The point is simply that you cannot infer any biochemical 'facts' about extraterrestrial compounds once they've been exposed to Earth's lifeforms.

Just want to ask..

[Visaris]

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 : )

Auto-Google

[jjjefff]

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...

Re:reason why not

[davebo]

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.

Hold on a sec!

[FreeLinux]

amino acids not found elsewhere on Earth

Every time I hear this I get rather angry. Are these people really so arrogant as to be absolutely certain that we have already found and identified ALL amino acids, presently on earth? Is there no chance at all, that these same amino acids could be present somewhere (bacteria in deep sea vents, perhaps) and we simply haven't found them yet?

I'm not trying to suggest that, the amino acids found on the meteor are not extra terrestrial. But, I just get angry at these people who seem to feel that they have seen everything that there is to see on terra firma.

Re:Only on earth...

[NaugaHunter]

The seems abundantly presumptuous. If it broke off of somewhere 4 billion years ago, or even 100 million years ago, it's entirely possible wherever it came from has evolved life and hasn't yet failed.

In fact, it seems odd to me that no one has yet suggested it originally came from Earth. Think about it. As I understand it, there wasn't much of an atmosphere before life, so it's feasible that for one reason or another a hunk flew off. I'm not about to calculate the path it would have flown, or even argue the likelihood, but I don't think it's impossible.

For reference, the nearest star is Proxima Centauri, at ~25,000,000,000,000 miles. I looked a number of places and found no consensus on the speed of the meteorite, but the larger number I saw was 20,000 mph. At that speed it would have taken ~150,000 years to get here. Since that is assuming a straight line among other things I feel it is reasonable to conclude wherever it came from it took longer than that, if it was near a star we know about.
(That really doesn't have anything to do with my point. But I did the research and math so I figured I might as well share it.)

Re:Left-handed?

[benzapp]

However, in many cases only dextro varieties of pharmaceuticals are active.

D-methamphetamine is used as an illicit stimulant. L-methamphetamine is used in those Vicks inhalers and is nearly inert in humans.

Dexedrine is pure dextroamphetamine, where as levoamphetamine is not even sold. It is however part of the Adderall mixture.

Re:How many times...

[Surt]

Victory over the church hardly seems relevant to the question of god's existence.

Agreed... but...

[joshuaos]

All your reasons why collecting asteroids would be quite difficult are valid. I also think that it would be an interesting, and likely fruitful, way to answer this rathering important question. More importantly however, I think that we have lots and lots of other reasons to go get us some ansteroids. There's a big asteroid belt out there with a lot of useful minerals, where we don't have a pesky ecosystem to worry about destroying, we can do all the damn mining we want on any unocupied asteroids we should find out there.

Although of course this would be an imense venture, probably requiring a permanent base on the moon and who knows where else, but it would remove the dependency of technology on earth from our fragile ecosystem, and let's face it, we've taken a lot of the easy metals out of the ground, and it's only going to get harder and harder to find. Another important point to remember is that although going up is expensive, going down is dirt cheap. ;)

My two cents. Joshua

evidence of extraterrestrial life?

[g4dget]

So, we have meteorites that contain molecules and chiral mixtures that are indicative of life. On the other hand, those mixtures do not correspond to anything terrestrial life forms would be expected to produce.

One logical conclusion seems to be that the meteorite contained extraterrestrial life, or perhaps a complex network of biochemical reactions that isn't quite life but a precursor. Those may have existed briefly in space and ceased long ago, or it may have been destroyed when the rock fell to earth, or we may simply not recognize it. I mean, if it doesn't have distinct membranes or other structural features, we wouldn't easily recognize life or close precursors of life at all with our current technology.

Re:How many times...

[fermion]

Science pretty much only shows that something probably doesn't exist. For instance, we are pretty certain an aether is not necessary for the conduction of EM radiation.

OTOH, science does provide a mechanism to show that a given explanation is consistent enough with all known data so that we may use that explanation to do useful things within a given domain. Science also provides mechanism to test predication resulting from the explanation against nature. The process generally leads to the simplest explanations, as those tend to be easiest to test and exploit.

In this case, if the organic material in the rock can be adequately explained with terrestrial sources, then we must accept the terrestrial explanation until such a time that we might get more data necessitating the complication of extraterrestrial life. By prematurely assuming extraterrestrial life, one runs the risk of contaminating the process.

Putting all this together, if we limit our 'truth' to a minimal set of useful and testable explanations, such as which we might get with the strict adherence to Occam's razor, god is unnecessary. After all, we turn on a light by completed a path for electrons, not praying. We insure our food supply by cross breeding plant and the application of chemical fertilizer, not by ritualistic acts of sex. We know the earth has an eccentric orbit, so see no need to dance to entice it's return on the winter solstice.

Re:Blah, Blah Blah....

[mikerich]

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.

The most famous example being thalidomide. The early production methods produced both versions of the compound. One isomer relieved morning sickness, the other was teratogenic and affected the unborn child.

Nowadays, thalidomide can be produced in the pure form and it shows promise against Hansen's Syndrome (leprosy) and some forms of cancer.

Best wishes,
Mike.