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A Farside Geochemical Window into the Moon

Explore the Dewar anomaly on the farside of the Moon, characterized by high concentrations of thorium, iron oxide, samarium, and titanium dioxide. Discover its formation and its significance in understanding the evolution of the lunar crust.

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A Farside Geochemical Window into the Moon

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  1. A Farside Geochemical Window into the Moon Dewar area • Thorium concentrations are highest on the nearside (Procellarium KREEP Terrane) • Farside characterized by low Th and FeO abundances • Anomalously high Th was found and studied near Dewar crater on the farside • Th distribution vital for understanding the evolution of the lunar crust www.psrd.hawaii.edu/April08/Dewar-Th.html

  2. A Farside Geochemical Window into the Moon Dewar anomaly has enhanced Th, FeO, Sm, andTiO2values relative to surrounding highlands. www.psrd.hawaii.edu/April08/Dewar-Th.html

  3. A Farside Geochemical Window into the Moon • Reflectance spectrum from the Dewar anomaly (red line) similar to near-side mare basalt (cyan line) • - Mafic assemblage dominated by high-Ca pyroxene • - Dewar anomaly likely caused by the presence of variable amounts of Th-rich mare basalt fragments in the regolith • Surrounding highlands have typical anorthosite spectrum (white line) www.psrd.hawaii.edu/April08/Dewar-Th.html

  4. A Farside Geochemical Window into the Moon How did the Dewar anomaly form? Body of evidence does not support a deposit of mafic impact melt breccias or surface deposits of mare basalts or pyroclastics. The Dewar anomaly probably formed from material excavated from a buried mare basalt, or cryptomare, derived from a magma with enhanced thorium concentrations. www.psrd.hawaii.edu/April08/Dewar-Th.html

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