Fate of Amino Acids and Nucleobases under Impact Induced Shock - Discovery of Complex Macroscale Structures and Implications to the Origins of life

Impacts are ubiquitous in Solar System. Impacts induced shock creates high temperature and pressure which provides chemical pathways for large scale molecular synthesis. With evidence of impact history over Solar System bodies, impact induced shock could be a profound source for complex chemistry. Previous studies suggest that biomolecules such as amino acids can be synthesized by such a process. However, due to the experimental limitation, the impact-shock chemistry still not much explored. We present for the first time, experimental evidence of complex macroscale structure formation due to shock processing of amino acid and nucleobases, utilizing a 7-meter-long shock tube in the laboratory, over post-shock temperature range of 1500 to 8000 K for 2 ms. The SEM and TEM micrographs of shock processed residue suggest that amino acids and nucleobases polymerized to form structures of μm to mm size consisting of complex morphology such as threads, ribbons, and tubes, twisted and folded and with specific textures on it (as shown in figure). Well defined patterns resembling to bunch of petals, buds, and leaves were also observed. Starting with the simplest amino acid glycine, we analysed the different combination of the amino acid mixture with 2, 4, 18 and 20 amino acids and mixture of nucleobases. More complex patterns tend to appear as we increase the number of amino acids in the mixture.

The tendency of amino acid and nucleobases towards formation of complex macroscale structure provides a clear evidence for survivability and evolution of the building blocks of life under impact shock condition. These structures also provide a possible explanation of microstructures observe in meteorite samples, which were earlier argued to be fossilized life forms. Our experimental simulation will take us one step further towards our understanding of Origins of life.