Comets are type of objects orbiting in star systems, it can be seen in Space stage.
In the full final version of Spore, it has now been shown that while comets are observable in the solar system zoom in the Space Stage, they cannot be interacted with. It was theorized during game development that players would be able to colonize comets.
It can be summoned a comet down onto a planet with terraforming tools. Summoning an Ice Comet onto a planet will increase atmosphere levels and also decrease the temperature, and Meteor Shower will increase the temperature. Each use will cost Sporebucks in certain of empires, it can be given for free in terraforming quest.