The Wet, Oxidizing Crust of Mars
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چکیده
Written by G. Jeffrey Taylor Hawai'i Institute of Geophysics and Planetology Studies have inferred that the oxidation state of Martian basaltic meteorites (the shergottites) is correlated with diagnostic geochemical parameters. For example, Meenakshi Wadhwa (Field Museum, Chicago) showed that as the ratio of triply-charged europium to doubly-charged europium (Eu3+/Eu2+) increases in a group of shergotties, the ratio of strontium-87 to strontium-86 (87Sr/86Sr) also increases, and neodynmium-143 to neodynmium-144 (143Nd/144Nd) decreases. [See PSRD article: Gullies and Canyons, Rocks and Experiments: The Mystery of Water on Mars]. Eu3+/Eu2+ is a measure of the oxidation state and can be used to infer the availability of oxygen to react chemically, a property called the oxygen fugacity. Christopher Herd, Lars Borg, and Jim Papike (University of New Mexico) and John Jones (Johnson Space Center) decided to measure the oxygen fugacity more directly by making very careful and painstaking analyses of oxide minerals in Martian meteorites.
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