image: View of the western Grand Canyon and the Colorado River from the canyon bottom. This image relates to a paper that appeared in the Nov. 29, 2012, issue of Science Express, published by AAAS. The paper, by Rebecca Flowers at University of Colorado at Boulder in Boulder, Colo., and colleagues was titled, "Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon." view more
Credit: Image courtesy of Rebecca Flowers