earth is a kind of planet & earth is greater in mass than mars & mars is a kind of planet ->  earth is a planet that has a greater mass than the planet mars  earth is a planet that has a greater mass than the planet mars & as mass of a planet / of a celestial body increases , the force of gravity on that planet will increase ->  the force of gravity on earth will be greater than on mars  the force of gravity on earth will be greater than on mars & as the force of gravity decreases , the weight of the object will decrease ->  objects will weigh less on mars than on earth because the force of gravity is less on mars  the force of gravity on earth will be greater than on mars & the gravitational force of a planet does not change the mass of an object on that planet or celestial body & gravitational force is similar to force of gravity ->  objects will have the same mass on earth and on mars  objects will weigh less on mars than on earth because the force of gravity is less on mars & objects will have the same mass on earth and on mars ->  objects will weigh less and have the same mass on mars than on earth  objects will weigh less and have the same mass on mars than on earth & a robot is a kind of object -> the robot will weigh less on mars than earth but will have the same mass