This page is a periodic description of current events or topics that concern the Nightly Observing Program held at the Kitt Peak Visitor Center. Imagine a comet. First, there aren't many snowballs ten kilometers across. Second, snow is frozen water.
Comets also have frozen carbon dioxide, methane, ammonia, and a few other chemicals.
Third, snow is too dense. Comets are delicate, gossamer objects. Cometary material makes snow look like lead. These things are saturated with carbon and silicates, making them as black as tar. Cometary material is a little like that.