Understanding crust-atmosphere interactions on Venus is fundamentally important to interpretations of Venus' surface spectroscopic data. Olivine, in basaltic crust, is oxidized under a heated CO2 atmosphere. However, the oxidation rates, product assemblages and spectral characteristics of olivine samples with different Fa# values remain largely unclear. Herein, we investigated the oxidation of olivine with different Fa# values (Fa(09), Fa(29) and Fa(71)) under CO2 atmosphere at 470 degrees C and 900 degrees C and characterized the oxidation products (both microscopically and macroscopically), conversion rates and VNIR spectra. The results showed that the oxidation of olivine produced magnesioferrite, magnetite, laihunite, hematite and maghemite at 470 degrees C and hematite, magnetite, magnesioferrite and amorphous SiO2 at 900 degrees C. Both high temperature and high Fa# values accelerated the oxidation rates. The production of oxide coatings on olivine grains (74 mu m in size) was estimated to be completed within tens to hundreds of years at 470 degrees C in natural settings, with even shorter periods under higher temperatures. Thus, CO2 oxidation would quickly eliminate olivine spectral characteristics, and spectral parameters at 850 and 1020 nm, as well as other relevant spectral windows (considering shifts induced by the elevated temperature), could be used to trace olivine oxidation processes. This work presented a case study connecting microscopic features to spectral characteristics for Venus' surface-atmosphere interactions. Further studies considering more realistic Venus' surface-atmosphere conditions will be essential to better interpret the measured spectroscopic data and determine the origins of the high emissivity detected on elevated terrain on Venus.

View here for the details