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NASA Reproduces a Building Block of Life In the Lab
xp65 writes "NASA scientists studying the origin of life have reproduced uracil, a key component of our hereditary material, in the laboratory. They discovered that an ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions produces this essential ingredient of life. 'We have demonstrated for the first time that we can make uracil, a component of RNA, non-biologically in a laboratory under conditions found in space,' said Michel Nuevo, research scientist at NASA's Ames Research Center, Moffett Field, Calif. 'We are showing that these laboratory processes, which simulate occurrences in outer space, can make a fundamental building block used by living organisms on Earth.'"
I have a feeling that this will lead to the speculation that Earth was therefore seeded with fundamental biomolecules from space and this paved the way for life to begin on Earth. I hope people don't jump to this conclusion too quickly. Personally, I find it unlikely and think there is a more likely interpretation, which I will get to in a moment. The reason this is unlikely is that just having biomolecules is not enough to start life processes. Especially in the time frame when life is hypothesized to have originated (~3.8Gya), as the surface of the Earth was completely covered by ocean at that time, and any seeding of organic molecules from external sources runs into the concentration problem: the problem of getting enough of the right molecules in the right place with the right concentration and the right inputs of energy and raw materials for biochemistry to begin. Any such seeding from external sources would end up very dilute, and biomolecules would likely break down before they could be gathered in sufficient concentrations.
Personally, one possible interpretation which I prefer is that these findings (and similar ones of finding amino acids in comets and such) indicate that organic biomolecules are fairly common and will form anywhere you have C, O, H, N, S, etc and energy. Not only would this indicate that biomolecules could form fairly easily on Earth, but that they are common in the universe, and organic life may arise just about anywhere you have an input of energy and raw materials and a way of concentrating those molecules so they will react and form self-organizing and self-replicating biochemistry.
My current favorite hypothesis about the origins of life on Earth are those championed by Martin and Russell. They hypothesize that life on Earth began and alkaline hydrothermal vents in the ocean, around which porous rocks of iron and nickel sulfide would form semi-permeable cell-like compartments in which basic organic molecules formed by the geochemistry of the vent could concentrate and react with each other. Raw materials would be constantly input from the vent, and there would be a constant energy gradient in the form of heat, pH, and proton-motive force. This neatly solves several problems of many hypotheses of abiogenesis: the energy problems, the raw materials problem, and the concentration problem to name a few. They outline the overall picture of going from geochemistry to biochemistry to prokaryotes to eukaryotes in this 2003 paper:
On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells - Martin and Russell, Phil. Trans. R. Soc. Lond. B 29 January 2003 vol. 358 no. 1429 59-85
They further clarify the possible pathways for a shift from geochemistry to biochemistry in this 2006 paper:
On the origin of biochemistry at an alkaline hydrothermal vent - Martin and Russell, Phil. Trans. R. Soc. B 29 October 2007 vol. 362 no. 1486 1887-1926
A search for either of those followed by clicking on the "Cited By" link on Google Scholar will yield many papers, including some actual experiments supporting them, which expand and clarify these hypotheses. Definitely worth a read if you are interested in the possible origins of life on Earth, as well as perhaps some ideas of what to look for when looking for life elsewhere.
Anyway, point being, this is fantastic work by NASA, and an excellent example of showing that these molecules can form naturally. Just be careful about drawing any definite conclusions from them other than the simple conclusion that Uracil can form in these natural conditions, and possibly or probably others.
"Empathise with stupidity, and you're halfway to thinking like an idiot." - Iain M. Banks
Mods can have my karma if they want it, its still a purely religious assertion to say that life spontaneously arises.
There's no definitive reason why it couldn't have happened, we observe life on this planet, and there is no real competing hypothesis, so it seems a reasonable, though speculative, hypothesis to entertain. Not certainty like the "God did it" crowd seem to have, but a rational inference from the data :-)
It's unobserved and there's good reason to believe its impossible (e.g. the chirality problem).
I wasn't aware the chirality problem was evidence towards abiogenesis being impossible, more that it presents a very interesting and challenging question as to why one particular handedness become dominant.