Prebiotic NH3 Formation: Insights from Simulations.

Area of Science:

• Astrochemistry
• Geochemistry
• Origin of Life Studies

Background:

• Prebiotic synthesis of ammonia (NH₃) is crucial for the origin of life.
• Pyrite (FeS₂) and hydrothermal conditions are proposed environments for early Earth chemistry.
• Nitrate (NO₃⁻) and nitrite (NO₂⁻) are potential nitrogen sources.

Purpose of the Study:

• To simulate and elucidate the reaction mechanism of prebiotic ammonia synthesis.
• To investigate the role of pyrite surfaces and hydrothermal conditions in NH₃ formation.
• To provide mechanistic support for the iron-sulfur-world hypothesis.

Main Methods:

• Ab initio metadynamics simulations were employed.
• Exploration of the full reaction pathway for NH₃ synthesis.
• Analysis of stepwise single atom transfer mechanisms.

Main Results:

• A detailed reaction mechanism for NH₃ formation from NO₃⁻ and NO₂⁻ on pyrite was elucidated.
• Simulations successfully reproduced and explained experimental observations.
• The roles of hot-pressurized water and pyrite surfaces were clarified.

Conclusions:

• The proposed reaction mechanism involves stepwise single atom transfers.
• These pathways are compatible with plausible prebiotic timescales.
• The findings strengthen the chemoautotrophic origin of life theory within the iron-sulfur-world scenario.