Program: GS-2009A-Q-26

We propose to conduct a detailed chemical abundance analysis of 9 bright red giant stars in the globular cluster M22 using Phoenix. M22 has long been suspected of harbouring a metallicity spread like that observed in Omega Centauri. However there is still no consensus on the metallicity spread of M22 due, in part, to the presence of variable extinction which may affect the results. We will use high excitation infrared iron lines (which are almost insensitive to temperature, i.e. to reddening) in order to draw firm conclusions on the metallicity spread of this cluster. Furthermore we will obtain abundances of C, N, O, Na, and F that will provide strong constraints on the issue of abundance anomalies in globular clusters.