Revisiting HCN formation in Earth's early atmosphere
Abstract
Using a new photochemical model, the HCN chemistry in Earth's early atmosphere is revisited. We find that HCN production in a CH 4-rich early atmosphere could have been efficient, similar to the results of a previous study (Zahnle, 1986). For an assumed CH 4 mixing ratio of 1000 ppmv, HCN surface deposition increases from 2 × 10 9 cm -2 s -1 at fCO 2 = 3% to more than 1 × 10 10 cm -2 s -1 (30 Tg/yr) at fCO 2 = 0.3% and 1%. These conditions may well have applied throughout much of the Archean eon, 3.8-2.5 Ga. Prior to the origin of life and the advent of methanogens, HCN production rates would likely have been at 1 × 10 7 cm -2 s -1 or lower, thereby providing a modest source of HCN for prebiotic synthesis.
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- August 2011
- DOI:
- 10.1016/j.epsl.2011.06.011
- Bibcode:
- 2011E&PSL.308..417T
- Keywords:
-
- early earth;
- HCN;
- photochemistry;
- ammonia