It hints at the answer. Most amino acids on Earth occur in the L configuration because they are mostly synthesized through biologic activity. This is not to say there are no D amino acids in living organisms -- they're just uncommon. And abiotic processes tend to produce racemic mixtures, but these products are in the minority. Basically, amino acids found on Earth, even in the atmosphere, strongly favor the L configuration. Analyzing the fraction of L and D amino acids within the meteorite would yield clues as to their origin.