Distribution maps of the coma can be made from infrared scans. These HRI-IR maps of the near nucleus coma in the left panels, acquired during closest approach to the nucleus of Hartley 2, show an enhancement of carbon dioxide emanating from the sunward facing small lobe of the nucleus. The water vapor, however, has a different distribution implying a different source region and process. A half a rotation later, when the small lobe is pointing away from the Sun and the nucleus is no longer resolved in the HRI telescope (right panels), the carbon dioxide is still concentrated around the small lobe, and thus enhanced in the anti-sunward direction. In this larger field of view, the water is also enhanced away from the Sun, suggesting that water ice dragged out by the carbon dioxide is pushed away from the Sun by its radiation pressure and eventually sublimes. The Sun is to the right for all panels and the pixels in which the nucleus is located are black. Credit: L. Feaga et al.
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