a) Spitzer IRS spectrum of the Class 0 protostar Serpens SMM1 using the Hi Res modules and a 7′′  ×  7′′ aperture. b) Continuum-subtracted spectra with main narrow lines identified in the LH module (λ  ≥  19.5 μm) and c) with the SH module (λ  ≤  19.5 μm). Note the lack of bright molecular line emission (H₂O, OH, etc.).