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D.C. Boice (Southwest Research Institute), Daniel T. Britt (University of Tennessee), Bill R. Sandel (University of Arizona), L.A. Soderblom (Astrogeology Branch, USGS), Nicolas Thomas (Max-Planck-Institut fuer Aeronomie), Roger V. Yelle (Northern Arizona University)
High-resolution images of the near-nucleus region of Comet 19P/Borrelly were returned by the MICAS imaging system onboard NASA's Deep Space One spacecraft during its successful flyby on 22 September 2001. Jet-like dust features are seen in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature is consistent with an area around the rotation pole that is constantly illuminated by the Sun during the encounter. In the near-nucleus region (within a few nucleus radii), entrained dust is rapidly accelerated and geometrical effects caused from extended source regions are present. These effects are evident in radial intensity profiles centered on the jet features that show an increase in source strength I*R with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. An initial interpretation of the dust distribution in the near-nucleus region surrounding Borrelly is provided. Qualitative comparisons with theoretical models are made where possible.
We are grateful to the NASA Deep Space One Mission for providing funds for this study.