Yesss we do, there are three geological periods, how we subdivide time is something I am very interested in. However Mars chronology is in its infancy. Just like how Earth once started out with just four time periods (Cenozoic, Mesozoic, Palaeozoic and Precambrian) that were then subdivided greatly as we learnt more and more, I expect that 40 years from now the number of Mars geological periods will have doubled or more.