{"id":15424,"date":"2018-06-26T17:08:23","date_gmt":"2018-06-26T15:08:23","guid":{"rendered":"http:\/\/karmaka.de\/?p=15424"},"modified":"2018-06-26T17:28:15","modified_gmt":"2018-06-26T15:28:15","slug":"compositional-variability-on-the-surface-of-1-ceres-revealed-through-grand-measurements-of-high%e2%80%90energy-gamma-rays","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=15424","title":{"rendered":"Compositional variability on the surface of 1 Ceres revealed through GRaND measurements of high\u2010energy gamma rays<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"<p>Lawrence, D. J., Peplowski, P. N., Beck, A. W., Feldman, W. C., Prettyman, T. H., Russell, C. T., Toplis, M. J., Wilson, J. T., Ammannito, E. , Castillo\u2010Rogez, J. C., DeSanctis, M. C., Mest, S. C. and Neesemann, A.<\/p>\n<p>Meteorit Planet Sci.<br \/>\ndoi:10.1111\/maps.13124<\/p>\n<p><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1111\/maps.13124\" target=\"_blank\"><strong>LINK (OPEN ACCESS)<\/strong><\/a><br \/>\n<a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/epdf\/10.1111\/maps.13124\"_blank\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n<p>&#8220;High\u2010energy gamma rays (HEGRs) from Ceres\u2019s surface were measured using Dawn&#8217;s Gamma Ray and Neutron Detector (GRaND). Models of cosmic\u2010ray\u2010initiated gamma ray production predict that the HEGR flux will inversely vary with single\u2010layer hydrogen concentrations for Ceres\u2010like compositions. The measured data confirm this prediction. The hydrogen\u2010induced variations in HEGR rates were decoupled from the measurements by detrending the HEGR data with Ceres single\u2010layer hydrogen concentrations determined by GRaND neutron measurements. Models indicate that hydrogen\u2010detrended HEGR counting rates correlate with water\u2010free average atomic mass, which is denoted as A*. HEGR variations across Ceres\u2019s surface are consistent with A* variations of \u00b10.5 atomic mass units. Chemical variations in the CM and CI chondrites, our closest analogs to Ceres\u2019s surface, suggest that A* variations on Ceres are primarily driven by variations in the concentration of Fe, although other elements such as Mg and S could contribute. Dawn observations have shown that Ceres\u2019s interior structure and surface composition have been modified by some combination of physical (i.e., ice\u2010rock fractionation) and\/or chemical (i.e., alteration) processes that has led to variations in bulk surface chemistry. Locations of the highest inferred A* values, and thus possibly the highest Fe and least altered materials, tend to be younger, less cratered surfaces that are broadly associated with the impact ejecta of Ceres\u2019s largest craters. &#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Lawrence, D. J., Peplowski, P. N., Beck, A. W., Feldman, W. C., Prettyman, T. H., Russell, C. T., Toplis, M. J., Wilson, J. T., Ammannito, E. , Castillo\u2010Rogez, J. C., DeSanctis, M. C., Mest, S&#8230;.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[167,10,18,360,181],"tags":[1868,1809,105,1880],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/15424"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15424"}],"version-history":[{"count":7,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/15424\/revisions"}],"predecessor-version":[{"id":15431,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/15424\/revisions\/15431"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15424"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15424"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15424"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}