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Two dust particles from the Murchison meteorite which fell to Earth in Australia in 1969.  (Source: Argonne National Laboratory, Department of Energy)
New evidence suggests that basic life really may have come from the stars.

It has long been thought that the seeds for life came to a primordial Earth from solar system leftovers crashing into the planet. These meteorites, comets, or other unknowns may have contained vital components with which budding life on Earth either assimilated or used as a catalyst to create itself. Now, in a paper to be published in Earth and Planetary Science Letters, European scientists claim they have evidence to prove the theory may be correct.

The group, based at Imperial College London, found some of the base building blocks for life, nucleobases, in dust from the Murchison meteorite which fell to Earth in 1969. Nucleobases, in this case uracil and xanthine, are the components that make up two of the most important parts of any Earth-bound life form, DNA and RNA.

In order to confirm that these molecules weren't from simple contamination, the researchers analyzed the individual atoms of the nucleobases. They found the carbon contained within was a heavier breed that what forms naturally on Earth. The molecules must have come from space.

Professor Mark Sephton, a co-author of the paper states “Because meteorites represent left over materials from the formation of the solar system, the key components for life -- including nucleobases -- could be widespread in the cosmos. As more and more of life’s raw materials are discovered in objects from space, the possibility of life springing forth wherever the right chemistry is present becomes more likely.”

While giving insights on how higher life may have formed on Earth, the finding may also bolster the theory that life may have once existed on a warmer, wetter Mars or a cooler, clearer Venus. NASA hopes to find evidence for such theories by analyzing the ice contained in the soil of the red wasteland that the Mars Phoenix Lander touched down on.



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By geddarkstorm on 6/16/2008 12:52:34 PM , Rating: 2
Why yes, they discovered uracil (only one base out of 5), and xanthine (a precursor base to the purines adenine and guanine) in some meteor. Supposing such chemicals didn't react with anything else on early earth to destroy them once they were released from the meteor (these that were found were still locked in, hence why they still existed), what about the ribose sugar and diester phosphate needed to complete the DNA/RNA backbone? Where'd those come from? Nevermind that if life like reactions started by using these (and how would it convert xanthine to adenine and guanine anyways without already being alive and developed to that point before hand?), it still needed to learn to synthesize these nucleobase molecules which requires very complex multi step, multi protein reactions and tons of energy; very elaborate cofactors such as THF; and proteins to be catabolized as the base for the purine/pyrimidine ring structure.

Nucleobases are meaningless by themselves. Caffeine is a nucleobase derivative of xanthine too, for instance, and you don't see it in our DNA. This whole thing is old news, but utterly meaningless biology wise, as just throwing nucleobases at a pond of goo will do nothing. The only thing it could do is provide carbon and nitrogen in a nice little bundle for energy saving catabolism and base scavenging, but that's it; which could be quite helpful for life that already existed to flourish during its fragile stage.


By masher2 (blog) on 6/16/2008 2:40:24 PM , Rating: 2
> "still needed to learn to synthesize these nucleobase molecules which requires very complex multi step, multi protein reactions and tons of energy"

How do you believe these nucleobases wound up in the micrometeorites unless they were spontaneously synthesized in some manner?


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