Silicate emission in Orion

We present mid-infrared spectro-imagery and high- resolution spectroscopy of the Orion bar and of a region in the Orion nebula. These observations have been obtained in the Guaranteed Time with the Circular Variable Filters of the ISO camera (CAM-CVF) and with the Short Wavelength Spectrom- eter (SWS), on board the European Infrared Space Observatory (ISO). Our data shows emission from amorphous silicate grains from the entire Hii region and around the isolated O9.5V star 2 Ori A. The observed spectra can be reproduced by a mixture of interstellar silicate and carbon grains heated by the radia- tion of the hot stars present in the region. Crystalline silicates are also observed in the Orion nebula and suspected around 2 Ori A. They are probably of interstellar origin. The ioniza- tion structure and the distribution of the carriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on the basis of the ISO observations.