Eli Dwek 1, R. G. Arendt 2, & S. H. Moseley 1
1 NASA/Goddard Space Flight Center
2 Raytheon, STX
Spectroscopic observations at 2.4 - 45 
of the
young supernova remnant Cas A with the
ISO Short Wavelengths Spectrometer (SWS) reveal strong emission
lines of O, Ne, Si, S, and Ar.
These lines are observed at high velocities (several 103 km s-1),
and thus associated with the
supernova ejecta known as the fast-moving knots (FMKs). Continuum emission from
dust is also seen in the Cas A spectrum. The continuum strength is spatially
well correlated with the O and Ar line strengths,
indicating that the dust emission
also arises from the FMKs. The dust continuum has a
peak at 
22
which
cannot be fit by typical astronomical silicates, but can be
fit with a particular class of silicate minerals.
This suggests that the dust in Cas A is silicate material that has freshly
condensed from the Cas A ejecta into a mineral form that is uncharacteristic
of typical ISM dust grains.