Comet Borrelly's Nucleus.

What does a comet nucleus look like? To answer this question, NASA controllers drove an aging probe through the hostile environs of a distant comet, expecting that even if comet fragments disabled the spacecraft, it would be worth the risk. The probe, Deep Space 1 , survived. Pictured above is the most detailed image ever taken of a comet nucleus, obtained Saturday by Deep Space 1 and released yesterday by NASA . Comet Borrelly 's nucleus is seen to be about 8 kilometers long with mountains , faults , grooves , smooth rolling plains , and materials of vastly different reflectance . Light colored regions are present near the center and seem to give rise to dust jets seen in Borrelly's coma , visible in distant images of the comet. Previously, the best image of a comet nucleus came from the Giotto mission to Comet Halley in 1986. Deep Space 1 images of Borrelly add welcomed bedrock to understanding Solar System history and to the accurate prediction of future brightness changes of notoriously fickle comet s.