Revisiting HCN formation in Earth's early atmosphere

Feng Tian, J. F. Kasting, K. Zahnle

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Using a new photochemical model, the HCN chemistry in Earth's early atmosphere is revisited. We find that HCN production in a CH4-rich early atmosphere could have been efficient, similar to the results of a previous study (Zahnle, 1986). For an assumed CH4 mixing ratio of 1000ppmv, HCN surface deposition increases from 2×109cm-2s-1 at fCO2=3% to more than 1×1010cm-2s-1 (30Tg/yr) at fCO2=0.3% and 1%. These conditions may well have applied throughout much of the Archean eon, 3.8-2.5Ga. Prior to the origin of life and the advent of methanogens, HCN production rates would likely have been at 1×107cm-2s-1 or lower, thereby providing a modest source of HCN for prebiotic synthesis.

Original languageEnglish (US)
Pages (from-to)417-423
Number of pages7
JournalEarth and Planetary Science Letters
Issue number3-4
StatePublished - Aug 15 2011

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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