Comet NEOWISE in the skies of far northern California's Humboldt County, California. What is a comet, and why do we see it? Comets are made of ice, rock and dust, like a dirty snowball. The ice may comprise any of a number of gases, frozen into a solid state in the icy blackness of space. As comets approach the sun, the sun’s energy acts on the comet’s surface, causing molecules of the ice to sublimate, or become gas again without going through a liquid state. As this happens, some larger particles of dust and debris making up the comet nucleus, or solid center, are blown outward into the surrounding space. This combination of gasses and larger particles surrounding the nucleus makes the hazy head, and forms the tail(s).