The next step is to find information that will help you make up your mind. There are lots of places to look.
Books are one of the best places.
Your classroom may have a collection of books on the planets. Another place to look is in an electronic encyclopedia like World Book. You are sure to find lots of information about the planets there. You'll need a search strategy to find only the information that will help you make up your mind. Look at your categories and little questions in your table.