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We present high angular resolution Submillimeter Array observations oftheoutbursting Jupiter family comet 17P/Holmes on 2007 October 26-29, achieving aspatial resolution of 2.5", or ~3000 km at the comet distance. The observationsresulted in detections of the rotational lines CO 3-2, HCN 4-3, H$^{13}$CN 4-3,CS 7-6, H$_2$CO 3$_{1,2}$-2$_{1,1}$, H$_2$S 2$_{2,0}$-2$_{1,1}$, and multipleCH$_3$OH lines, along with the associated dust continuum at 221 and 349 GHz.The continuum has a spectral index of 2.7$\pm$0.3, slightly steeper thanblackbody emission from large dust particles. From the imaging data, weidentify two components in the molecular emission. One component ischaracterized by a relatively broad line width (~1 km s$^{-1}$ FWHM) exhibitinga symmetric outgassing pattern with respect to the nucleus position. The secondcomponent has a narrower line width (<0.5 km s$^{-1}$ FWHM) with the linecenter red-shifted by 0.1-0.2 km s$^{-1}$ (cometocentric frame), and shows avelocity shift across the nucleus position with the position angle graduallychanging from 66 to 30 degrees within the four days of observations. Wedetermine distinctly different CO/HCN ratios for each of the components. Forthe broad-line component we find CO/HCN <7, while in the narrow-line component,CO/HCN = 40$\pm$5. We hypothesize that the narrow-line component originatesfrom the ice grain halo found in near-nucleus photometry, believed to becreated by sublimating recently released ice grains around the nucleus duringthe outburst. In this interpretation, the high CO/HCN ratio of this componentreflects the more pristine volatile composition of nucleus material released inthe outburst.

Peculiar Near-Nucleus Outgassing of Comet 17P/Holmes During Its 2007 Outburst