Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

Abstract

NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

Meteorite impacts on ancient oceans opened up multiple NH3 production pathways

“…We used a system consisting of a Fe 36 slab, 16 N 2 , and 38 H 2 O molecules (a total of 182 atoms; see Fig. 1(a)), which is the same one as in our previous study, 12 where the ratio of Fe atoms, N atoms, and H 2 O molecules nearly coincided with that in the experimental starting material. 10 This system represents the initial reactions when a meteorite (the Fe 36 slab) with adsorbed atmospheric N 2 collides with the sea surface while engulfing other atmospheric N 2 .…”

“…In contrast, the temperature rapidly increased at around 0.2 ps, and subsequently it gradually increased from around 2,450 to 3,180 K. This indicates that some exothermic reactions occur. For comparison, the values of the volume ratio, pressure, particle velocity, and temperature at 4 ps in the 5 km/s shock-wave simulation 12 were 0.58, 27.6 GPa, 2.30 km/s, and 2,100 K, respectively. Due to the higher compression ratio (V /V 0 = 0.50 < 0.58), P, U p , and T of the present simulation were greater than those of the previous one.…”

“…In our previous study, 12 a simple initial atomic configuration consisting of N 2 , H 2 O, and metallic iron was created with reference to the sample composition of the experiment, 10 imitating the early Earth's environment during the LHB period (see Fig. 1(a)).…”

Survival of Extremotolerant Bacteria from the Mukundpura Meteorite Impact Crater

“…A meteorite impact causes chemical interactions within the meteoritic material. Previous experimental and theoretical works have reported that these chemical interactions cause the production of volatiles, organic, and inorganic molecules in simulated impact conditions (Fegley et al, 1986;Mukhin et al, 1989;Sekine et al, 2003;Schaefer and Fegley, 2010;Furukawa et al, 2015;Shimamura et al, 2016). These impact events are the only known unique extraterrestrial event that disrupts an ecosystem in time and space (Cockell and Lee, 2007).…”

“…A meteorite impact on planetary surfaces causes a sudden increase in pressure and temperature and generates shock waves (Shimamura et al, 2016). A meteorite impact causes chemical interactions within the meteoritic material.…”