From this article alone I don't see a compelling case that this is not merely contamination. It is an oft repeated error to say that:
Life on Earth uses left-handed amino acids, and they are never mixed with right-handed ones, but the amino acids found in the meteorite had equal amounts of the left and right-handed varieties.
And once again reflects the hopeless bias towards eukaryotes that these astrobiologists always tend to display.
D-Amino acids are absurdly common
in the peptidoglycan of most bacteria (for the simple reason that most bacteria-bacteria conflict and bacteria-eukaryote conflict is mediated through the use of proteases and the post translational modification of membrane amino-acids to D is a profitable survival mechanism). If L/D ratio is their sole criteria for disproving contamination, they have not sufficiently demonstrated their premise.