The 45 micron H2O ice band in the Kleinmann-Low Nebula

The spectrum of the Kleinmann-Low Nebula has been measured from 105 to 365 (95-27 μm) with ∼6 cm⁻¹ resolution using NASA's Kuiper Airborne Observatory. The data show a broad absorption with a maximum depth of ∼5% at 240 cm⁻¹ (42 μm) relative to the adjacent continuum. The feature is probably real, since a featureless spectrum of Mars was obtained on one of the same flights. The spectrum is well fitted by a model consisting of an absorbing layer of silicate water-ice grains obscuring an 87 K slab with optical depth varying smoothly with frequency. This model also shows a water-ice feature at 3.1 μm which is consistent with the strength of the 3.1 m absorption observed in the spectrum of the Becklin-Neugebauer source.