Shock synthesis of amino acids from impacting cometary and icy planet surface analogues


Comets are known to harbour simple ices and the organic precursors of the building blocks of proteins—amino acids—that are essential to life. Indeed, glycine, the simplest amino acid, was recently confirmed to be present on comet 81P/Wild-2 from samples returned by NASA’s Stardust spacecraft. Impacts of icy bodies (such as comets) onto rocky surfaces, and, equally, impacts of rocky bodies onto icy surfaces (such as the jovian and saturnian satellites), could have been responsible for the manufacture of these complex organic molecules through a process of shock synthesis. Here we present laboratory experiments in which we shocked ice mixtures analogous to those found in a comet with a steel projectile fired at high velocities in a light gas gun to test whether amino acids could be produced. We found that the hypervelocity impact shock of a typical comet ice mixture produced several amino acids after hydrolysis. These include equal amounts of D- and L-alanine, and the non-protein amino acids α-aminoisobutyric acid and isovaline as well as their precursors. Our findings suggest a pathway for the synthetic production of the components of proteins within our Solar System, and thus a potential pathway towards life through icy impacts.

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Figure 1: Chromatogram of extracts from shocked ice sample no. 1.
Figure 2: Chromatogram of extracts from shocked ice sample no. 2.
Figure 3: Relative amino acid abundances (glycine = 1) versus increasing carbon number for the linear α-amino acids detected in the target ice sample no. 1 (grey) and target ice sample no. 2 (white).


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We acknowledge financial support from the Science and Technology Facilities Council (STFC). Z. Martins is financially supported by the Royal Society. Many thanks to M. Cole for his technical expertise and for firing the gun, and A. Kearsley and P. Wozniakiewicz for many useful and inspiring discussions.

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M.C.P. made the ice targets and performed the hypervelocity impact-shock experiments. Z.M. performed the amino acid analysis and interpretation. N.G. performed the hydrodynamic simulations of cometary impacts. M.C.P., N.G. and M.J.B. designed the experimental impact study. Z.M. and M.C.P. wrote the article and contributed equally to the study. M.J.B. and M.A.S. provided experimental facilities. All of the authors discussed the results and commented on the manuscript.

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Correspondence to Zita Martins or Mark C. Price.

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The authors declare no competing financial interests.

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Martins, Z., Price, M., Goldman, N. et al. Shock synthesis of amino acids from impacting cometary and icy planet surface analogues. Nature Geosci 6, 1045–1049 (2013).

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