OBSERVATION OF A MASS-INDEPENDENT OXYGEN ISOTOPIC COMPOSITION IN TERRESTRIAL STRATOSPHERIC CO2, THE LINK TO OZONE CHEMISTRY, AND THE POSSIBLE OCCURRENCE IN THE MARTIAN ATMOSPHERE

Multi-isotope (delta(17)O and delta(18)O) measurements of stratospheri c CO2 and (CO)-C-14 are reported. Samples were acquired from altitudes in excess of 11.5 km from Christchurch, New Zealand to the South Pole . A mass independent isotopic variation is observed in CO2, the magnit ude of which correlates well with (CO)-C-14 concentration, indicating a stratospheric source of the effect. The component arises from isotop ic exchange between the product of O-3 photolysis, O(D-1) and CO2, thu s providing a unique measure of ozone photolysis and turnover. A simil ar process may occur in the Martian atmosphere, as suggested by water isotopic measurements from SNC meteorites.