  We have performed the first detailed spatially resolved spectroscopy of Cas A
in the 1.6-10 keV energy range, using data taken with the MECS spectrometer on
board the BeppoSAX Observatory. We performed a spatial deconvolution of the
data and eventually generated a set of spectra, covering a region of about 3
arcmin radius around the centre of Cas A. The results obtained by fitting these
spectra using a non-equilibrium ionisation plasma model and a power law, are:
(i) a single thermal component is sufficient to fit all the spectra; (ii) kT is
rather uniformly distributed with a minimum in the east and a maximum in the
west, and no evidence is found for high kT expected from the interaction of the
main shock with the ISM; (iii) from the distribution of the values of the
ionisation parameter n_et we infer the presence of two distinct components: the
first (a) in the range 1-10 cm^(-3), the second (b) with values ten times
higher; if we associate component a to the CSM and component b to the ejecta,
the mass ratio M(a)/M(b)<= 1/10 indicates a progenitor star that lost only a
small fraction of the envelope during its pre-SN life. In this hypothesis the
distribution of component b across the remnant suggests that the explosion was
not spherically symmetric; (iv) the distribution of abundances indicates that
we are detecting a CSM component with almost solar composition, and an ejecta
component enriched in heavier elements. Abundances found for alpha-elements are
consistent with the current view that Cas A was produced by the explosion of a
massive star.
