Hyakutake: Comet Atmosphere . ... STScI , and NASA Explanation: The atmosphere of a comet comes and goes . ... Immense but tenuous and fleeting, the inner atmosphere or inner "coma" of comet Hyakutake is seen in this false color picture . ... It is about 14,000 km across (comparable to Earth's diameter) and is a combination of images showing dust reflected light (red) and ultraviolet light scattered from Hydrogen atoms (blue). ... NASA Web Site Statements, Warnings, and Disclaimers . ...