Origin-of-life Molecules in the Atmosphere after Big Impacts on the Early Earth

Abstract The origin of life on Earth would benefit from a prebiotic atmosphere that produced nitriles, like HCN, which enable ribonucleotide synthesis. However, geochemical evidence suggests Hadean air was relatively oxidizing with negligible photochemical production molecules. These paradoxes are resolved by iron-rich asteroid impacts transiently reduced the entire atmosphere, allowing nitriles to form in subsequent photochemistry. Here we investigate impact-generated reducing atmospheres using new time-dependent, coupled atmospheric chemistry and climate models account for gas-phase reactions surface catalysis. resulting H 2 -, CH 4 NH 3 -rich persist millions years, until hydrogen escapes space. HCN HCCCN rainout can reach 10 9 molecules cm −2 s −1 hazy mole ratio /CO > 0.1. Smaller ratios produce rates <10 5 HCCCN. minimum impactor mass creates 0.1 is × 20 –5 21 kg (570–1330 km diameter), depending how efficiently iron reacts steam extent equilibration an impact-induced melt pond, area nickel catalyzes production. Alternatively, if permeates deeply oxidizes crust, impactors ∼10 could be effective. Atmospheres copious have >360 K temperatures, perhaps posing challenge RNA longevity, although cloud albedo cooler climates. Regardless, postimpact cyanide stockpiled used schemes after has escaped