Within the universe of the Hyperion Cantos, the Solmev Scale is an ancient system aimed at measuring how Earth-like a planet or moon is. It seems to range from 0 to 10, with 10 being the most Earth-like. Worlds ranging from 7.9 through 10 were considered the most Earthlike. For instance, all Labyrinthine Worlds were at least 7.9 on the scale. Mars received a 2.5 on the scale prior to terraforming.
Often called the old Solmev Scale on the books, its origins seem to be lay in the Hegira as humans sought other worlds to colonize. Even worlds considered high on the Solmev Scale underwent some degree of Terraforming.