One of the building blocks of life has been found on a comet hurtling through the solar system, adding evidence to the theory that earthly biology began when comets and meteors bombarded our young planet and seeded it with the precursors of life. The amino acid, glycine, was found in a sample returned by the space probe Stardust that buzzed by the comet Wild 2 in 2004. The probe swept up particles fizzing off the object’s surface as it passed some 240km (149 miles) from the comet’s core, or nucleus. These tiny grains, just a few thousandths or a millimetre in size, were then returned to Earth in 2006 in a sealed capsule [BBC News].
Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons – a process that can take place on Earth or in space [New Scientist].
The findings, which the researchers announced at an American Chemical Society meeting, also suggest that extraterrestrial life may be a common occurrence. “If you’re seeing amino acids in comets, then that really gives credence to the idea that the basic components of life are going to be widespread throughout the universe,” said planetary biologist Max Bernstein of the NASA Astrobiology Institute, who was not involved in the research. “It’s one thing for me to do it in the lab and say it should be so, but it’s another thing for somebody to actually measure it” [Wired.com].
In 2008, scientists declared that they’d found amino acids in the sample returned from Wild 2, but couldn’t say for sure that they weren’t a result of earthly contamination. It took more than a year to determine the origin of glycine, the simplest amino acid in the sample. With only about 100 billionths of a gram of glycine to study, the researchers were able to measure the relative abundance of its carbon isotopes. It contained more carbon-13 than that found in glycine that forms on Earth, proving that Stardust’s glycine originated in space [New Scientist]. A formal report will be published in the journal Meteoritics & Planetary Science.
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Image: NASA/JPL
August 20th, 2009 at 11:41 am
Does that mean that the devil could still have planted all of those dinosaur bones to deceive us?
August 20th, 2009 at 3:16 pm
Yep, that devil is sure a pesky fellow…more than likely it was g.o.d. who made it look like the entire universe is only 10,000 years old, probably much younger, after all he can do anything, and we are just too stupid to know better…
August 20th, 2009 at 3:17 pm
Yep…juuuust to dang stupid.
August 20th, 2009 at 4:16 pm
Hey, have respect for different opinions, don’t call other persons like that because you show who you’re. Be open minded and accept free speech even you’re disagreed. Don’t be the person you call me!!!!!……..
August 20th, 2009 at 4:25 pm
God is the only Creator. He created everything, it was not the devil who put the threes in the eden garden, it was God. But the creator is not less than its creatiopn, so HE can’t sin. I don’t believe in the devil, it is each one of us. The sin and all those who like to commit sin, just because God put it there for you and I to decide.
Good luck understanding this, open minded friend……..
August 20th, 2009 at 4:27 pm
You are and will be what ever you have in your mind, my fellow internet user……
August 20th, 2009 at 7:52 pm
For biogenesis to occur all amino acids of living protoplasm must have laevorotary chirality – this is an absolute necessity. Dextrorotary amino acids do not fit into the metabolism of living organisms. If even very small amounts of amino acid molecules of the dextrorotary type are present, proteins of a different 3-D structure are formed; these proteins are not capable of supporting life, and often can be fatal to life.
What was the chirality ratio of the glycine amino acid molecules found in a sample returned by the space probe? Was it 100% laevorotary (as required by living organisms), or a 50:50 mix, as occurs with lab experiments on Earth?
September 29th, 2009 at 12:15 pm
Glycine is the only proteinogenic amino acid that is achiral–it doesn’t not possess chirality. This is because its alpha-carbon has two hydrogens (the same functional group) attached to it, and therefore it can be superimposed on its mirror image.
Also, your understanding of chirality is confused. The D-form and L-form notation of amino acids does not refer to the direction in which they rotate a plane of polarized light, but to their structural similarity to the optically active enantiomer of glyceraldehyde which does. For example, an amino acid may technically rotate a plane of polarized light to the right [and be dextrorotary, more properly notated (+)] BUT still be the L-form if it is structurally similar to levorotary (-) glyceraldehyde that rotates a plane of polarized light counter-clockwise, to the left.
I would also like to point out that the existence of naturally-occurring racemic mixes (50:50) of amino acids would not prove anything. To the best of my knowledge, it is believed that once L-amino acids began to be used biologically, everything else after that could only work with that, and so it did. It could have just as easily been the other way around. The fact that the overwhelming disparity exists rather than different phyla or whatever using their own form is actually very good evidence for common descent (i.e., evolution). This statement
“If even very small amounts of amino acid molecules of the dextrorotary
type are present, proteins of a different 3-D structure are formed; these
proteins are not capable of supporting life, and often can be fatal to life.”
is simply not true. The incorrect enantiomer would not be incorporated into a protein at all–most likely it would harnlessly excreted–or it may in fact be switched to the “correct” form by a racemase enzyme.
And finally, D-forms of amino acids are not necessarily not physiologically active. D-amino acids are incorporated into peptidoglycan in some bacterial cell walls. A more relevant example: D-serine formed by serine racemase activates NDMA receptors in the brain and is being investigated as an important neurotransmitter.