  We investigate the ability of high resolution X-ray spectroscopy to directly
probe the grain composition of the interstellar medium. Using iron K-edge
experimental data of likely ISM dust candidates taken at the National
Synchrotron Light Source at Brookhaven National Laboratory and the Advanced
Photon Source at Argonne National Laboratory, we explore the prospects for
determining the chemical composition of astrophysical dust and discuss a
technique for doing so. Focusing on the capabilities of the AstroE2 XRS
micro-calorimeters, we assess the limiting effects of spectral resolution and
noise for detecting significant X-ray absorption fine structure signal in
astrophysical environments containing dust. We find that given sufficient
signal, the resolution of the XRS will allow us to definitively distinguish gas
from dust phase absorption, and certain chemical compositions.
