  We present mid-infrared spectro-imaging (5 - 16 microns) observations of the
infrared luminous interacting system Arp 299 (=Mrk171 =IC694+NGC3690) obtained
with the ISOCAM instrument aboard ISO. Our observations show that nearly 40% of
the total emission at 7 and 15 microns is diffuse, originating from the
interacting disks of the galaxies. Moreover, they indicate the presence of
large amounts of hot dust in the main infrared sources of the system and large
extinctions toward the nuclei. While the observed spectra have an overall
similar shape, mainly composed of Unidentified Infrared Bands (UIB) in the
short wavelength domain, a strong continuum at ~ 13 microns and a deep silicate
absorption band at 10 microns, their differences reveal the varying physical
conditions of each component. For each source, the spectral energy distribution
(SED) can be reproduced by a linear combination of a UIB "canonical" spectral
template and a hot dust continuum due to a 230-300 K black body, after
independently applying an extinction correction to both of them. We find that
the UIB extinction does not vary much throughout the system (A_V ~ 5 mag)
suggesting that most UIBs originate from less enshrouded regions. IC694 appears
to dominate the infrared emission of the system and our observations support
the interpretation of a deeply embedded nuclear starburst located behind an
absorption of about 40 mag. The central region of NGC3690 displays a hard
radiation field characterized by a [NeIII]/[NeII] ratio > 1.8. It also hosts a
strong continuum from 5 to 16 microns which can be explained as thermal
emission from a deeply embedded (A_V ~ 60 mag) compact source, consistent with
the mid-infrared signature of an active galactic nucleus (AGN), and in
agreement with recent X-ray findings.
