Hydrogen cyanide in nitrogen-rich atmospheres of rocky exoplanets

• DOI: 10.1016/j.icarus.2019.02.020
• Publication Date: 2019-03-22T03:04:56Z
• Authors: P.B. Rimmer; S. Rugheimer
• Keywords: Hydrogen cyanide; Carbon fibers; Acetylene

Hydrogen cyanide (HCN) is a key feedstock molecule for the production of life's building blocks. The formation HCN in an N2-rich atmospheres requires first that triple bond between N≡N be severed, and then atomic nitrogen find carbon atom. These two tasks can accomplished via photochemistry, lightning, impacts, or volcanism. requirements producing appreciable amounts are free availability N2 local to oxygen ratio C/O ≥ 1. We discuss chemical mechanisms by which formed destroyed on rocky exoplanets with Earth-like content surface water inventories, varying oxidation state dominant carbon-containing atmospheric species. most readily produced atmosphere rich methane (CH4) acetylene (C2H2), but also significant (>1 ppm) within CO-dominated atmospheres. Methane not necessary HCN. show how destruction CO2-rich depends critically poorly-constrained energetic barrier reaction oxygen. implications our results detecting photochemically HCN, concentrating planet's surface, its importance prebiotic chemistry.