Impact-induced amino acid formation on Hadean Earth and Noachian Mars

Yuto Takeuchi,Takeshi Kakegawa,Yoshihiro Furukawa,Toshimori Sekine,Takamichi Kobayashi,Naoki Terada

doi:10.1038/s41598-020-66112-8

Abstract

Abiotic synthesis of biomolecules is an essential step for the chemical origin of life. Many attempts have succeeded in synthesizing biomolecules, including amino acids and nucleobases (e.g., via spark discharge, impact shock, and hydrothermal heating), from reduced compounds that may have been limited in their availabilities on Hadean Earth and Noachian Mars. On the other hand, formation of amino-acids and nucleobases from CO2 and N2 (i.e., the most abundant C and N sources on Earth during the Hadean) has been limited via spark discharge. Here, we demonstrate the synthesis of amino acids by laboratory impact-induced reactions among simple inorganic mixtures: Fe, Ni, Mg2SiO4, H2O, CO2, and N2, by coupling the reduction of CO2, N2, and H2O with the oxidation of metallic Fe and Ni. These chemical processes simulated the possible reactions at impacts of Fe-bearing meteorites/asteroids on oceans with a CO2 and N2 atmosphere. The results indicate that hypervelocity impact was a source of amino acids on the Earth during the Hadean and potentially on Mars during the Noachian. Amino acids formed during such events could more readily polymerize in the next step of the chemical evolution, as impact events locally form amino acids at the impact sites.

Highlights

The composition of early Earth’s atmosphere has been a subject of discussion
Spark-discharge with carbonate buffer reported by Cleaves et al.[15] might have worked as a source of prebiotic amino acid, ascorbate hydrolysis used in the work was challenged by a subsequent spark discharge study as a source of amino acid contamination[16]
An experimentally-supported geological event that synthesizes amino acids is limited in spark discharge on neutral ocean

Summary

Introduction

The composition of early Earth’s atmosphere has been a subject of discussion. The atmosphere was once regarded as strongly reduced, composed mostly of CH4, NH3, and H21. Initiated by Miller’s 1953 experiment, the formation of amino acids and nucleobases by spark discharge from reduced reactants (e.g., CO, CH4, and H2) has long been investigated as a potential source of the building blocks of life[12,13]. For other methods, such as shock-heating of the atmosphere, photochemical reactions, and proton irradiation, studies have reported that the formation of amino acids were limited to experiments using reduced C and N sources[12,13,17,18,19,20,21,22].

Results

Conclusion