Data Set Overview  :   A global map of the concentration of hydrogen, with units of weight  percent water equivalent hydrogen (WEH), within the regolith of  1 Ceres is provided as an ASCII table. The map data are given for  twenty-degree, quasi-equal-area pixels.   The data reduction and analysis methods are presented in the Supplement  of PRETTYMANETAL2017. Thermal+epithermal counting rates measured in  Dawn'scircular, polar, low-altitude mapping orbit (LAMO), at a mean  distance of about 385 km from Ceres' surface were corrected for  variations in the flux of galactic cosmic rays (GCR) and measurement  geometry. The corrected epithermal counting data were  globally mapped on 20-deg equal-area pixels. Hydrogen concentration  was determined from the counting data using calculated trends  for compositional models [PRETTYMANETAL2017, Supplement]. The map gives  a lower bound on the concentration of hydrogen on Ceres.   The reported uncertainties give the systematic error in the spatial  distribution of hydrogen due to assumptions regarding model composition.  Contributions from statistical variations in counts are small in  comparison. Consequently, the reported uncertainties represent the  total error in the spatial distribution of hydrogen.   Parameters  :   Each row of the table gives the concentration of hydrogen for a  single rectangular pixel.   The format for each row is '(I10,4(F7.1),2(E14.4))'.   East longitude convention is used (-180 to 180 degrees).   Each pixel spans a separate and unique portion of Vesta's surface, and  together, the pixels provide full global coverage. The BROWSE directory  displays the data as a global map. The column descriptions follow:   COLUMN NAME FORMAT DESCRIPTION UNITS  0 PIXEL_INDEX (I10) N/A  1 MIN_LAT (F7.1) Pixel latitude lower boundary deg  2 MAX_LAT (F7.1) Pixel latitude upper boundary deg  3 MIN_LON (F7.1) Pixel longitude lower boundary deg  4 MAX_LON (F7.1) Pixel longitude upper boundary deg  5 HYDROGEN_CONCENTRATION  (F8.1) Hydrogen concentration [a] wt.% WEH  6 SIG_HYDROGEN_CONCENTRATION  (F8.1) Uncertainty wt.% WEH   [a] The concentratation of hydrogen is expressed as weight percent (wt.%) Water Equivalent Hydrogen (WEH) The concentration of hydrogen can be  determined by dividing wt.% WEH by 9.

Confidence Level Overview  :   The data set is a high order data product derived from thermal + epithermal  neutron counting data acquired by GRaND in LAMO as described by  PRETTYMANETAL2017.   Review  :   This data set is in review by NASA Planetary Data System.   Data Coverage and Quality  :   The data set contains a global map of the concentration of hydrogen within  Ceres' regolith. There are no gaps in coverage. The depth sampled  by thermal+epithermal neutrons from which hydrogen abundances are provided  is a few decimeters (for example, see PRETTYMANETAL2011).   Coordinate System  :   The prime meridian is anchored by a small crater called Kait at 2 degrees  South [RUSSELLETAL2016]. East longitude convention is used.   Limitations  :   Assumptions underlying the analysis of hydrogen on Ceres and are presented  by PRETTYMANETAL2017 (Supplement).   Hydrogen concentrations reported in water equivalent hydrogen units  do not represent the concentration of molecular water within Ceres'  regolith. GRaND is sensitive to all forms of elemental hydrogen, independent of molecular form. For example, hydrogen may be present in Ceres' regolith  in the form of water ice, minerals of hydration, organic matter, and other  hydrogen bearing mineral phases.   The analysis assumes the composition of Ceres' regolith is uniform  with depth. This assumption is valid near the equator, where water ice  is thought to be at depths greater than sensed by GRaND, and at high  latitudes, where ice is very close to the surface. The assumption  may not be valid at mid-latitudes where the ice table is within  depths sensed by GRaND.