Fig. 1: Wavelength-dependent isotopic fractionation of CO2 photolysis.
From: Synthesis of 13C-depleted organic matter from CO in a reducing early Martian atmosphere
Preferential dissociation of 12CO2 against 13CO2 is expected in a wavelength region from 170 nm to 200 nm, which is responsible for solar UV photolysis of CO2. a, Actinic UV spectra. Red: solar spectrum from ref. 43. Blue: calculated spectrum at 30 km altitude (alt.) of model early Mars (10 mbar CO2 at surface) (Methods). Black: measured UV spectrum of the high pressure Xe lamp used in the laboratory experiment (Methods). b, Calculated absorption cross sections of 12CO2 (black) and 13CO2 (orange) at 295 K from ref. 17. c, Calculated isotope effect (1,000 ln α1) as a function of wavelength for the 295 K absorption spectra. Results were averaged over a 1 nm (black) and 5 nm (red) windows. Oxygen isotopic fractionation and its implications for Mars atmosphere were given elsewhere17.
