Nucleus of Comet Halley

Nucleus of Comet Halley

. A composite image of the nucleus of Comet Halley (right) obtained using images taken in March 1986 with the camera on board the Giotto spacecraft, from a distance of 6.5 million meters before comet dust destroyed the camera. It is compared with a schematic drawing (left) that highlights the major features recognizable in the photograph. The nucleus is about 16 kilometers long and 8 kilometers wide. Dust and gas geyser out of narrow jets from the sunlit side of the nucleus, but about 90 percent of the surface is inactive. The gas is mainly water vapor sublimed from ice in the nucleus, while a significant fraction of the dust may be dark carbon-rich matter. A dark surface crust, which insulates most of the underlying ice, is blacker than coal, reflecting about 4 percent of the incident sunlight. “Mountains” rise about 500 meters above the surrounding terrain, while a broad “crater” is depressed about 100 meters. (Image courtesy of Harold Reitsema of the Ball Aerospace Corporation and Horst Uwe Keller.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University