Data Set Information
DATA_SET_NAME LUNAR PROSPECTOR GRS ELEMENTAL ABUNDANCE V1.0
DATA_SET_ID LP-L-GRS-5-ELEM-ABUNDANCE-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : These tables provide maps of weight fractions and terms of the error matrix for major oxides and K, Th, and U for the Moon from Lunar Prospector Gamma Ray and Neutron Spectrometer data acquired at high altitude (100 km) and binned on 2, 5, and 20 degree equal area pixels. The tables contain the original elemental abundances reported by PRETTYMANETAL2006. The abundances were determined by gamma ray spectral unmixing. The data were acquired during the high altitude (approximately 100 km) phase (HIGH1) with a northward orientation for Lunar Prospector's spin axis. At this altitude, the spatial resolution of the gamma ray spectrometer was about 5 degrees of arc length on the surface (PRETTYMANETAL2006). Parameters : Each row of the table provides composition information for a single pixel. The format for each row is '(i10,4(f7.1),57(1x,e14.4))'. East longitude convention is used (-180 to 180 degrees). The column description follows: 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 AM (E14.4) Average atomic mass g/mol 6 NEUTRON_DEN (E14.4) Neutron number density g/cm3 7 W_MGO (E14.4) Weight fraction MgO g/g 8 W_AL2O3 (E14.4) Weight fraction Al2O3 g/g 9 W_SIO2 (E14.4) Weight fraction SiO2 g/g 10 W_CAO (E14.4) Weight fraction CaO g/g 11 W_TIO2 (E14.4) Weight fraction TiO2 g/g 12 W_FEO (E14.4) Weight fraction FeO g/g 13 W_K (E14.4) Weight fraction K ppm 14 W_TH (E14.4) Weight fraction Th ppm 15 W_U (E14.4) Weight fraction U (tied U:0.27Th) ppm The following columns are elements of the error matrix that contains covariance terms used to estimate errors in parameters and derived quantities. The square root of the diagonal of the error matrix gives the propogated uncertainty in the oxides and elemental abundances. Example usage of the error matrix is given by PRETTYMANETAL2006 (Eqs. 9 and 10). In this data set description, the components of the error matrix are denoted E[I,J], where I and J are the row and column index of the component, respectively. The indices refer to major oxides and elements as follows: (0 - MgO, 1 - Al2O3, 2 - SiO2, 3 - CaO, 4 - TiO2, 5 - FeO, 6 - K, 7 - Th, 8 - U) COLUMN NAME FORMAT DESCRIPTION 16 E[0,0] (E14.4) Error matrix component 17 E[0,1] (E14.4) Error matrix component 18 E[0,2] (E14.4) Error matrix component 19 E[0,3] (E14.4) Error matrix component 20 E[0,4] (E14.4) Error matrix component 21 E[0,5] (E14.4) Error matrix component 22 E[0,6] (E14.4) Error matrix component 23 E[0,7] (E14.4) Error matrix component 24 E[0,8] (E14.4) Error matrix component 25 E[1,1] (E14.4) Error matrix component 26 E[1,2] (E14.4) Error matrix component 27 E[1,3] (E14.4) Error matrix component 28 E[1,4] (E14.4) Error matrix component 29 E[1,5] (E14.4) Error matrix component 30 E[1,6] (E14.4) Error matrix component 31 E[1,7] (E14.4) Error matrix component 32 E[1,8] (E14.4) Error matrix component 33 E[2,2] (E14.4) Error matrix component 34 E[2,3] (E14.4) Error matrix component 35 E[2,4] (E14.4) Error matrix component 36 E[2,5] (E14.4) Error matrix component 37 E[2,6] (E14.4) Error matrix component 38 E[2,7] (E14.4) Error matrix component 39 E[2,8] (E14.4) Error matrix component 40 E[3,3] (E14.4) Error matrix component 41 E[3,4] (E14.4) Error matrix component 42 E[3,5] (E14.4) Error matrix component 43 E[3,6] (E14.4) Error matrix component 44 E[3,7] (E14.4) Error matrix component 45 E[3,8] (E14.4) Error matrix component 46 E[4,4] (E14.4) Error matrix component 47 E[4,5] (E14.4) Error matrix component 48 E[4,6] (E14.4) Error matrix component 49 E[4,7] (E14.4) Error matrix component 50 E[4,8] (E14.4) Error matrix component 51 E[5,5] (E14.4) Error matrix component 52 E[5,6] (E14.4) Error matrix component 53 E[5,7] (E14.4) Error matrix component 54 E[5,8] (E14.4) Error matrix component 55 E[6,6] (E14.4) Error matrix component 56 E[6,7] (E14.4) Error matrix component 57 E[6,8] (E14.4) Error matrix component 58 E[7,7] (E14.4) Error matrix component 59 E[7,8] (E14.4) Error matrix component 60 E[8,8] (E14.4) Error matrix component
DATA_SET_RELEASE_DATE 2012-10-24T00:00:00.000Z
START_TIME 1998-01-17T12:00:00.000Z
STOP_TIME 1998-10-07T12:00:00.000Z
MISSION_NAME LUNAR PROSPECTOR
MISSION_START_DATE 1995-01-01T12:00:00.000Z
MISSION_STOP_DATE 1999-07-31T12:00:00.000Z
TARGET_NAME MOON
TARGET_TYPE SATELLITE
INSTRUMENT_HOST_ID LP
INSTRUMENT_NAME GAMMA RAY SPECTROMETER
INSTRUMENT_ID GRS
INSTRUMENT_TYPE SPECTROMETER
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : The data set is a high order data product derived from gamma ray and neutron spectra measured by Lunar Prospector as described by PRETTYMANETAL2006. The gamma ray spectral data set from which elemental abundances were determined is described in LAWRENCEETAL2004. Neutron data products used in the analysis are described by MAURICEETAL2004. Review : This data set has passed a Planetary Data System peer review. Data Coverage and Quality : The data set contains a complete, global map of the lunar surface for major oxides and K, Th, and U. Oxides and elemental abundances are compared with lunar sample and meteorite compositional data by PRETTYMANETAL2006. The data set was further validated by a pixel-by-pixel comparison of 2200 m/s neutron macroscopic absorption cross sections (Sigma_a_GRS) determined from the 5-degree elemental abundance data of PRETTYMANETAL2006 to those determined by the Lunar Prospector Neutron Spectrometer (Sigma_a_NS). The Neutron Spectrometer absorption cross section was determined using a correlation derived from LAWRENCEETAL2006. Namely, Sigma_a_NS (cm**2/g) : 5.0x10E-3 (C_epi/C_therm) - 3.4x10E-4, where C_epi and C_therm were the measured epithermal and thermal neutron counting rates, respectively, for the target pixel. For each pixel, the macroscopic cross section was determined from the elemental abundances by the following sum: Sigma_a_GRS : SUM_i ( 0.0662 * sigma{i} * w{i} / A{i} ), where SUM_i denotes the sum over all elements, i is the element index, sigma{i} is the microscopic absorption cross section at 2200 m/s in barns (10E-24 cm**2), w{i} is the weight fraction of element i, and A{i} is the atomic mass of element i. Gd and Sm were not determined by PRETTYMANETAL2006. Abundances for these elements were determined by correlation with Th [ELPHICETAL2000]. The range of absorption cross sections over the lunar surface was found to be approximately 3 to 12 (E-3 cm**2/g). Sigma_a_GRS and Sigma_a_NS were linearly correlated with a Pearson coeffient of r:0.9885. The best fit line was Sigma_a_GRS : 1.135 Sigma_a_NS - 0.732. The percentage difference between the derived quantities was then %Diff : 100 (Sigma_a_GRS - Sigma_a_NS)/Sigma_a_NS : 13.5 - 73.2/Sigma_a_NS, which gives -10.9% for the low end and 7.4% difference for the high end of the range of values for the macroscopic absorption cross section. For the feldspathic highlands terrane (FHT), Sigma_a_NS was approximately 3.8E-3 cm2/g, correponding to a difference of -5.8%. The NS analysis was carried out without recourse to lunar ground truth, relying only on the physical description of the detector (validated by laboratory calibration experiments) to determine the response function of the 3He sensors and models of the lunar leakage flux for typical lunar compositions. The validity of the leakage model was demonstrated by MCKINNEYETAL2006. That the neutron and spectral unmixing analyses give similar results for macroscopic absorption supports the spectral unmixing calibration assumption. Namely, the composition of the highlands is adequately represented by the composition of the feldspathic lunar meteorites. A similar comparison was made for average atomic masses determined from the elemental data (A_GRS) and from the analysis of fast neutron data (A_NS) by GASNAULTETAL2001 for 5-degree equal area maps. The range of values for the average atomic mass was 21.4 to 23.9 amu. A_GRS and A_NS were linearly correlated with a Pearson coefficient of r:0.944. The best fit line was A_GRS : 1.174 A_NS - 3.81 and the percentage difference was %Diff : 100 (A_GRS - A_NS)/A_NS : 17.4 - 381/A_NS, which gives -0.4% for the low end and 1.5% difference for the high end of the range of values for average atomic mass. Limitations : The unmixing algorithm tied the weight fraction of U (w_U) to the weight fraction of Th (w_Th), such that w_U : 0.27 x w_Th. Small deviations from this trend in the tabulated U and Th abundances, typically much less than a percent, were introduced by the optimization algorithm used to solve the least squares spectral unmixing problem. Additional analysis assumptions and sources of error are described by PRETTYMANETAL2006. The gamma ray spectrometer is not sensitive to minor components of the lunar regolith, such as CrO2, MnO, Na2O, P2O5, and ZrO2. For lunar soils, regolith breccias, and meteorites (PRETTYMANETAL2006), these sum to about 1% (g/g) on average and at most to 2%. An analysis of oxide sums determined by spectral unmixing was reported by PRETTYMANETAL2006. The analysis shows that accumulated systematic errors in the elemental abundances determined by gamma ray spectroscopy are larger than can be accounted for by neglecting these minor components. Maps of FeO, TiO2, K, and Th, binned on 2-degree equal area pixels, were evaluated by PRETTYMANETAL2006. For completeness, the other oxides determined by spectral unmixing (MgO, Al2O3, SiO2, CaO) are included in the 2-degree data set in this distribution. These have not been thoroughly evaluated and have relatively poor precision in comparison to the 5- and 20-degree data. Consequently, caution is recommended in using 2-degree elemental abundances other than FeO, TiO2, K, and Th.
CITATION_DESCRIPTION Prettyman, T.H., Lunar Prospector GRS Elemental Abundance, LP-L-GRS-5-ELEM-ABUNDANCE-V1.0, NASA Planetary Data System, 2012.
ABSTRACT_TEXT This data set provides tables of weight fractions and terms of the error matrix for major oxides and K, Th, and U for the Moon from Lunar Prospector Gamma Ray and Neutron Spectrometer data acquired at high altitude (100 km) and binned on 2, 5, or 20 degree equal area pixels. The table contains the original elemental abundances reported by PRETTYMANETAL2006. The abundances were determined by gamma ray spectral unmixing.
PRODUCER_FULL_NAME THOMAS H. PRETTYMAN
SEARCH/ACCESS DATA
  • Geosciences Web Service
  • Geosciences Online Archives
    		•