Global Elemental Maps of the Moon: The Lunar Prospector Gamma-Ray Spectrometer

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Science  04 Sep 1998:
Vol. 281, Issue 5382, pp. 1484-1489
DOI: 10.1126/science.281.5382.1484


  • Figure 1

    LP gamma-ray spectra plotted as number of counts per 32 s versus energy. The top panel shows an average of all 356,691 gamma-ray spectra collected during the first 5 months of the mission. Because more spectra have been taken at the lunar poles, the counts in the all-moon spectrum are weighted toward the poles. The bottom panel shows spectra taken for two different lunar regions. The plot for the Imbrium Region is the average of 2694 spectra taken from 30°W to 10°W and 20°N to 40°N within Mare Imbrium. This region is known for being rich in basalts and KREEP-rich material. The plot labeled Joule Region is the average of 2677 spectra taken from 150°W to 130°W and 15°N to 30°N. The Joule crater (located at 145°W, 25°N) is located in the lunar highlands which are mainly anorthositic.

  • Figure 2

    (top). Color-coded map of the log of the thorium counting rate as measured by the LP GRS. The bottom panel shows a Mercator projection for latitudes of 45°S to 45°N, and the top panel shows stereographic projections for latitudes of 45° to 90° at the north and south poles. The data are binned into equal area pixels that have a size of 5° latitude by 5° longitude at the equator. Contours of albedo data taken from Clementine data (11) are shown for latitudes between 70°S and 70°N.

  • Figure 4

    Lunar nearside and farside orthographic maps of the log of the thorium counting rate. The nearside map is centered on Mare Imbrium and the farside map is centered on the antipode to Mare Imbrium. The color scale and albedo contours are the same as Fig. 2. This projection shows that the farside thorium maximum is close to the antipode of the local minimum within Mare Imbrium.

  • Figure 5

    The highlands thorium distribution as a function of distance from the Imbrium impact point from the LP GRS data (closed circles) and the model curves of Haskin (14). The highlands regions for the LP data in this figure were selected using Clementine albedo data (11). The upper and lower model curves are based on the largest (485 km) and smallest (335 km) estimation of the Imbrium transient crater and are calculated as the percentage of primary material ejected from Imbrium. Because the LP data are counts and not absolute abundances, the data have been slightly scaled to fall between the Haskin curves in the range of less than 1500 km.

  • Figure 6

    Plot of potassium counting rate versus thorium counting rate as measured by the LP GRS.

  • Figure 7

    Plot of measured LP thorium counting rate versus derived soil abundances in parts per million (ppm) for various landing sites. The soil measurements are taken from the data set of Korotev (16) who tabulated extreme high and low values for each Apollo site (no ranges were given for the Luna data because the samples were all taken from a single core). Although the symbols are plotted at the midpoint values between the extremes, they do not necessarily represent the average value for the site. The LP measurements are taken from the 150 by 150 km pixel covering each landing site. The uncertainty of the LP measurements due to counting statistics is approximately the size of the plotting symbols. The symbols for the different landing sites are as follows: ×, Apollo 11; □, Apollo 12; •, Apollo 14; ♦, Apollo 15; ▴, Apollo 16; ○, Apollo 17; +, Luna 16; ⋄, Luna 20; ▪, Luna 24; ⊗, maximum LP thorium counting rate.

  • Figure 8

    Map of the iron counting rate as measured by the LP GRS. The projections and albedo contours are the same as forFigs. 2 and 3.

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