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T. A. Bida (Lowell Observatory), R. Killen, T. H. Morgan (Southwest Research Institute)
We present measurements of Ca radiance, abundance, LOS velocity, and inferred temperature in Mercury's atmosphere made on six successive evenings in June 2000. Utilizing the HIRES echelle spectrograph on the Keck-1 telescope, multiple high-resolution spectra were taken each day that yield the first maps of the Ca distribution around Mercury. The observations extend spatially and temporally the first measurements of Ca in Mercury's atmosphere (Bida, Killen, and Morgan, Nature 404, 159, 2000). The Ca exosphere exhibits localization of the brightest emission (at 500 R) near Mercury's poles, and apparant extreme temperature (12000 K). Simultaneous measurements of and comparison to Mercury's Na corona will also be presented.