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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."
The first Apollo mission found the moon to be sterile, but later Apollo missions found strep bacteria from previous missions.
That's a little misleading. Apollo 12 found microbes inside the camera of Surveyor 3 (which landed three years before). Its not like the strep bacteria are colonizing the moon -- I'm pretty sure that the lunar environment is still sterile.
"The dinosaurs died because they didn't have a space program." - Niven
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.