Program: GN-2010A-Q-83

We propose to take low resolution spectra from 1.9 to 2.49 microns along the line of sight toward 36 field stars behind the molecular clouds LDN 673 and Serpens. These new K-band observations are necessary to deduce the spectral type of the field stars (K or M giants), so that (sub)structure in the 3.0 micron water-ice band and the mid-infrared absorption features, associated with the molecular cloud dust in front of these field stars, can be confidently identified as being interstellar or circumstellar. Accurately spectral typing the field stars along lines of sight with little extinction will allow us to determine any contamination to the detected weak ice bands, thereby more tightly constraining the minimum extinction threshold at which ice starts to form in molecular clouds.