Publication Date:
2019-08-28
Description:
We present experimental results showing that basalt is oxidized in CO-CO2 gas mixtures having CO number densities close to those (approximately 2 times higher) at the surface of Venus. The results suggest that the red color observed by Pieters et al at the Venera 9 and 10 landing sites is due to subaerial oxidation of Fe(2+)-bearing basalt on the surface of Venus, and that hematite, instead of magnetite, is present on the surface of Venus. Well-characterized basalt powder was iosthermally heated in 1000 ppm CO-CO2 gas mixtures at atmospheric pressure for several days. The starting material and reacted samples were analyzed by Mossbauer spectroscopy to determine the amount of Fe(2+) and Fe(3+) in the samples. X-ray diffraction and optical microscopy were also used to characterize samples. The basalt oxidation occurs because the CO and CO2 do not equilibrate in the gas mixture at the low temperatures used. Thus, the basalt reacts with the more abundant CO2 and is oxidized. We propose that the red color of the surface of Venus is due to failure of CO and CO2 to equilibrate with one another in the near-surface atmosphere of Venus, leading to subaerial oxidation of erupted Fe(2+)-bearing basalts. Our interpretation is supported by our studies of magnetite oxidation, which show that synthetic magnetite powders are oxidized to hematite in CO-CO2 gas mixtures inside the magnetite stability field, by our studies of pyrite decomposition, and by independent work on CO-CO2 equilibration in furnace gases.
Keywords:
LUNAR AND PLANETARY EXPLORATION
Type:
Meteoritics (ISSN 0026-1114); 29; 4; p. 465-466
Format:
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