Re: Organic carbon detected in Bright Angel rock formation on Mars

"Jim Wilkins"  wrote in message news:[email protected]...

> https://en.wikipedia.org/wiki/Carbonaceous_chondrite

"Shortly after its fall and recovery in Australia in 1969, the Murchison 
meteorite was found to host five protein amino acids (glycine, alanine, 
valine, proline, and glutamic acid) in addition to 12 non-proteinogenic 
amino acids including α-aminoisobutyric acid and isovaline, which are rare 
on Earth.[27] Since then, the number of characterised amino acids in the 
Murchison meteorite has risen to 96, including 12 of the 20 common 
biological amino acids, along with hundreds more that have been detected, 
but remain uncharacterised."

"Amino acids may be structurally chiral, meaning that they have two possible 
non-superimposable mirror image structures, termed enantiomers. 
Conventionally, these are referred to as left-handed (L) and right-handed 
(D) by analogy with glyceraldehyde. Living beings use L-amino acids, 
although there is no apparent reason why one enantiomer is favoured over the 
other as they behave equivalently in biological systems. In contrast with 
terrestrial biology, early laboratory studies, including the famous 
Miller-Urey Experiment, have shown that amino acids may form under a range 
of possible abiotic conditions with equal (racemic) mixtures of D- and 
L-enantiomers. Thus, the ratios between enantiomers for a given amino acid 
may discriminate between biotic and abiotic formation mechanisms. In the 
first characterisation of amino acids in Murchison, all chiral examples were 
present in racemic mixtures indicating an abiotic origin."

This means that these organic amino acids (protein building blocks) have a 
signature indicating they were not created all identically under the 
guidance of biology, instead by random processes, with an equal chance of 
being assembled in either of two possible configurations, like a mix of 
right and left hand threaded screws.