Larry Evans

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X-ray fluorescence spectra obtained by the MESSENGER spacecraft orbiting Mercury indicate that the planet's surface differs in composition from those of other terrestrial planets. Relatively high Mg/Si and low Al/Si and Ca/Si ratios rule out a lunarlike feldspar-rich crust. The sulfur abundance is at least 10 times higher than that of the silicate portion(More)
The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 220 ± 60 parts per billion), and uranium (U, 90 ± 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent(More)
[1] A technique for converting gamma-ray count rates measured by the Gamma-Ray Spectrometer on the MESSENGER spacecraft to spatially resolved maps of the gamma-ray emission from the surface of Mercury is utilized to map the surface distributions of the elements Si, O, and K over the planet's northern hemisphere. Conversion of the K gamma-ray count rates to(More)
Our society is increasingly relying on symbolic and imaginal communication to augment written and spoken language (advertising graphics, logos and corporate I.D.s, satellite weather maps, international traffic, dashboard symbols, etc.). Nowhere are graphics and sophisticated imagery being more widely and innovatively used than in television production.(More)
The first map of variations in the abundances of thermal-neutron-absorbing elements across Mercury's surface has been derived from measurements made with the anti-coincidence shield on MESSENGER's Gamma-Ray Spectrometer (GRS). The results, which are limited to Mercury's northern hemisphere, permit the identification of four major geochemical terranes at the(More)
  • Robert G Varady, R G Varady, Modern Era Garfin, P Romero-Lankao, S B Megdal, S Eden +306 others
  • 2013
– Global and transboundary groundwater governance – Global water initiatives – Environment, natural-resources, climate, and water-management policy – U.S.-Mexico border environment, comparative border environmental policy and new: Changing paradigms in arid lands water management. In Water and Sustainability in Arid Regions, ed. A regional center for new(More)
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