Temperature dependence of the quadrupole splitting of olivine and pyroxene from the Plains of Gusev Crater on Mars

摘要

In the present work, we report application of simultaneous fitting procedures to Moessbauer data acquired on the Plains of Gusev Crater by the MIMOS Ⅱ spectrometer on board the Mars Exploration Rover Spirit. Based on a quantitative measure of spectrum quality, the 34 best of the ～126 spectra acquired on the Plains are grouped together for a single simultaneous fit with a common least-squares criterion. Fitted values for the quadrupole splitting (QS) of olivine (Ol) from 200 K to 260 K are shown to lie between reported trend lines for Fo50 and Fo30 olivine, with a temperature gradient of (-11.2 ± 1.2) × 10~(-4) mm/s/K, a nearly five-fold improvement in precision over the previously reported value, enabling extrapolation to QS(Ol) = (2.93 ± 0.01) mm/s at 295 K. QS of pyroxene fit as a single doublet exhibits a temperature gradient of (-7.3 ± 2.3) × 10~(-4) mm/s/K.