<span>Mass is how much matter you are made of, so unless you eat a lot of junk food or somehow lose an arm on the way to the moon it will remain the same. Your weight is the combination of your mass and the pull of gravity and can vary greatly. Remember, the moon has about 1/6 the gravity of earth, so you'd weigh about 11.6 Kg on the moon.</span>
and Methane 
