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 fallin
g inside the magnetite stability field, Mossbauer spectroscopy shows t
hat hematite and Fe3+ in pyroxene are produced in the oxidized basalt,
The results suggest that the red color observed at several Venera lan
ding sites is due to sub-aerial oxidation of Fe2+-bearing basalt on th
e surface of Venus, and that hematite, instead of magnetite, is presen
t on the surface of Venus. (C) 1995 Academic Press, Inc.