ICE CO-CKTAILS IN MOLECULAR CLOUD CORES

Spectra of the 4.67 mu m (2140 cm(-1)) solid-CO absorption feature are presented, towards embedded low mass Young Stellar Objects in nearby molecular cloud cores, mostly in Taurus. The likely composition of the CO-bearing ices is analysed by fitting the observations with laborato ry data and the statistical significance of the results is discussed. Excellent fits to the nonpolar component of the CO-ices along the obse rved lines of sight are produced with irradiated pure CO ices, as prev iously suggested by Palumbo & Strazzulla (1993). It does not seem to b e possible, however, to constrain the composition of the polar compone nt by analysis of the CO band only. The possible origin of the ion irr adiation is discussed. The implications of the non-uniqueness of the f it on the determination of the abundance ratio between nonpolar and po lar CO-ices are noted. Future observations are suggested to discrimina te between the different possibilities for the polar component. Predic tions are made for the abundance of CO2 and methanol in the mantles.