Whether a planet has an atmosphere or not depends on a number of factors: mass, temperature, composition of the crust, volcanic activity, and complex evolutionary processes. Rank the planets according to how well they retain their atmospheres, using the following criteria: • The planet that still maintains its primary atmosphere, ranks first. • The planet that lost its primary atmosphere but retains a dense secondary atmosphere, ranks second. • The planet that lost its primary atmosphere and retains a tenuous secondary atmosphere, ranks third. • The planet that retained neither its primary nor secondary atmospheres, ranks last.