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Sensitive 5-38 um Spitzer Space Telescope (SST) and ground based 3-5 umspectra of the embedded low mass protostars B5 IRS1 and HH46 IRS show deep iceabsorption bands superposed on steeply rising mid-infrared continua. The iceslikely originate in the circumstellar envelopes. The CO2 bending mode at 15 umis a particularly powerful tracer of the ice composition and processinghistory. Toward these protostars, this band shows little evidence for thermalprocessing at temperatures above 50 K. Signatures of lower temperatureprocessing are present in the CO and OCN- bands, however. The observed CO2profile indicates an intimate mixture with H2O, but not necessarily with CH3OH,in contrast to some high mass protostars. This is consistent with the low CH3OHabundance derived from the ground based L band spectra. The CO2/H2O columndensity ratios are high in both B5 IRS1 and HH46 IRS (~35%). Clearly, the SSTspectra are essential to study ice evolution in low mass protostellarenvironments, and to eventually determine the relation between interstellar andsolar system ices.Comment: Scheduled for publication in ApJS Sept. 2004, v154 [Spitzer Special  issue]. 5 pages, 1 b&w figure, 1 color figur

Spitzer Space Telescope Spectroscopy of Ices toward Low‐Mass Embedded Protostars