Basalt oxidation and the formation of hematite on the surface of Venus

We present experimental results showing that basalt is oxidized in gas mixtures with CO number densities approximately equal to those at the surface of Venus. Although the gas mixtures have CO/CO2 ratios falling inside the magnetite stability field, Mossbauer spectroscopy shows that hematite and Fe3+ in pyroxene are produced in the oxidized basalt, The results suggest that the red color observed at several Venera landing sites is due to sub-aerial oxidation of Fe2+-bearing basalt on the surface of Venus, and that hematite, instead of magnetite, is present on the surface of Venus. (C) 1995 Academic Press, Inc.