ISOCAM MAPPING OF THE RHO-OPHIUCHI MAIN CLOUD

We present preliminary results of the ISOCAM survey of the rho Ophiuch i main cloud L1688 (0.5 square degrees) conducted in the two broad-ban d filters LW2 (5-8.5 mu m) and LW3 (12-18 mu m). This letter focuses o n the properties of the extended emission. ISOCAM observations have re vealed several previously unknown characteristics of the mid-IR diffus e emission: the small scale filamentary structure (thickness similar t o 0.03 pc) of the emission at the illuminated edge of the molecular cl oud, the sharpness of color variations at cloud edges, the barely reso lved filamentary structure of the dust emission surrounding a bright e mbedded source, and several dense cores seen as sharp and deep absorpt ion structures against the diffuse cloud background.