Evidence for sodium-rich alkaline water in the Tagish Lake parent body and implications for amino acid synthesis and racemization

Understanding the timing and mechanisms of amino acid synthesis and racemization on asteroidal parent bodies is key to demonstrating how amino acids evolved to be mostly left-handed in living organisms on Earth. It has been postulated that racemization can occur rapidly dependent on several factors,...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-05, Vol.117 (21), p.11217-11219
Main Authors: White, Lee F., Tait, Kimberly T., Langelier, Brian, Lymer, Elizabeth A., aCernok, Ana, Kizovski, Tanya V., Ma, Chi, Tschauner, Oliver, Nicklin, Richard I.
Format: Article
Language:English
Subjects:
Alkaline water
Amino acids
Aqueous solutions
BRIEF REPORTS
Carbonaceous chondrites
Grain sub boundaries
Handedness
Lakes
Magnetite
Meteorite parent bodies
Physical Sciences
Racemization
Sodium
Surface charge
Synthesis
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Summary:Understanding the timing and mechanisms of amino acid synthesis and racemization on asteroidal parent bodies is key to demonstrating how amino acids evolved to be mostly left-handed in living organisms on Earth. It has been postulated that racemization can occur rapidly dependent on several factors, including the pH of the aqueous solution. Here, we conduct nanoscale geochemical analysis of a framboidal magnetite grain within the Tagish Lake carbonaceous chondrite to demonstrate that the interlocking crystal arrangement formed within a sodium-rich, alkaline fluid environment. Notably, we report on the discovery of Na-enriched subgrain boundaries and nanometer-scale Ca and Mg layers surrounding individual framboids. These interstitial coatings would yield a surface charge state of zero in more-alkaline fluids and prevent assimilation of the individual framboids into a single grain. This basic solution would support rapid synthesis and racemization rates on the order of years, suggesting that the low abundances of amino acids in Tagish Lake cannot be ascribed to fluid chemistry.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2003276117