L. A. Soderblom,^1* T. L. Becker,¹ G. Bennett,¹ D. C. Boice,² D. T. Britt,³ R. H. Brown,⁴ B. J. Buratti,⁵ C. Isbell,¹ B. Giese,⁶ T. Hare,¹ M. D. Hicks,⁵ E. Howington-Kraus,¹ R. L. Kirk,¹ M. Lee,⁵ R. M. Nelson,⁵ J. Oberst,⁶ T. C. Owen,⁷ M. D. Rayman,⁵ B. R. Sandel,⁴ S. A. Stern,⁸ N. Thomas,⁹ R. V. Yelle⁴

The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (345 kelvin, with no trace of water ice or hydrated minerals), consistent with ~10% or less of the surface actively sublimating. Borrelly's coma exhibits two types of dust features: fans and highly collimated jets. At encounter, the near-nucleus coma was dominated by a prominent dust jet that resolved into at least three smaller jets emanating from a broad basin in the middle of the nucleus. Because the major dust jet remained fixed in orientation, it is evidently aligned near the rotation axis of the nucleus.

¹ United States Geological Survey, 2255 North Gemini Drive, Flagstaff, AZ 86001, USA.
² Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238, USA.
³ Department of Geological Sciences, University of Tennessee, 306 Geological Sciences Building, Knoxville, TN 37996, USA.
⁴ Department of Planetary Science, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
⁵ Jet Propulsion Laboratory (JPL), California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
⁶ DLR Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse, 2D-12489 Berlin, Germany.
⁷ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA.
⁸ Department of Space Studies, Southwest Research Institute, 1050 Walnut Street No. 426, Boulder, CO 80302, USA.
⁹ Max-Planck-Institut für Aeronomie, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau, Germany.
^*   To whom correspondence should be addressed. E-mail: lsoderblom{at}usgs.gov