Mercury: Determining Minerals And Their Abundances With Mid-IR Spectral Deconvolution III

Abstract

We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W longitude from five slit observations at regions in north-mid and north latitudes. The subtending slit sectors have central coordinates as follows: (1) 11 April 2006#89; 203°W, 13°N 205°W, 47°N (2) 7 April 2006#77; 210°W, 8°N 230°W, 25°N (3) 11 April 2006#96; 212°W, 15°N 219°W, 45°N (4) 11 April 2006#93; 225°W, 13°N 237°W, 45°N (5) 11 April 2006#109; 262°W, 8°N, 267°W, 25°N. Our results are obtained by modeling spectra obtained with the Mid-Infrared Spectrometer and Imager (MIRSI) at the Infrared Telescope Facility (IRTF) using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR). We have assembled several mineral libraries (JHU, Salisbury et al. 1991; JPL, http://speclib.jpl.nasa.gov; RELAB, http://www.planetary brown.edu/relab; ASU, http://speclib.asu.edu; BED, Maturilli et al. 2007, LPSC XXXVIII Abs.) consisting of a wide range of known mineral compositions with grain sizes ranging from the finest separates, 0 - 45 µm, incrementally increasing to 250 - 400 µm. Surface mineral deconvolutions are suggestive of albite, enstatite, clinopyroxene, labradorite, and sodalite, mineral phases that have been previously observed in the mid-infrared at Mercury (Sprague et al. 1994, 1998, Icarus). The deconvolution also identified pigeonite at more than one location. The same techniques and computer program have correctly fit the known compositions of the HED samples, and given a plausible fit to spectra from the Moon (both also presented at this meeting). This work was funded by NSF AST0406796.