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Calibration of the MER α‐particle x‐ray spectrometer for detection of ‘invisible’ OH and H 2 O possibly present in Martian rocks and soils
Author(s) -
Mallett Christiane L.,
O'Meara Joanne M.,
Maxwell John A.,
Campbell John L.
Publication year - 2006
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.914
Subject(s) - martian , calibration , mars exploration program , spectrometer , physics , martian surface , mineralogy , analytical chemistry (journal) , materials science , optics , geology , chemistry , astrobiology , quantum mechanics , chromatography
An existing Monte Carlo code was modified and extended to predict the intensity ratio of elastically and inelastically scattered plutonium Lα x‐rays incident on rock samples in the Mars Exploration Rover's α‐particle x‐ray spectrometer (APXS) device. The systematics of the scatter ratio as a function of effective sample atomic number are explored. The simulated Rayleigh/Compton ratios (R/C) sim are compared with measured ratios (R/C) meas that are obtained by fitting APXS spectra of geochemical reference materials using an x‐ray fluorescence version of GUPIX. The quantity K = (R/C) meas /(R/C) sim is then plotted against the mean atomic number of the sample to provide a calibration for known samples. Departures of K values of unknown samples from this calibration may then be attributed to the presence of light, ‘invisible’ elements in the sample. This work is part of an ongoing project aimed at developing methods to quantify bound water in Martian rocks analyzed by the present and the next generation APXS instruments. Copyright © 2006 John Wiley & Sons, Ltd.