The mass of an astronaut is 70 kg on the Moon. What is the mass of the astronaut on Earth?
70 kg! Mass is a measure of the particles that make up an object and the composition of the object does not change on the moon. However the object's weight will change on the moon, just as it appears to change on an elevator.
The acceleration due to gravity on the earth is approximately 9.8 m/s^2, depending upon where an object is located. On the moon, the acceleration due to the moon's gravity is 1.6 m/s^2, which is approximately 1/6 that on the earth. Sine an object's weight is dependent upon the pull of gravity, the object's weight will change with the pull of gravity. Since the moon does not pull as strongly on the object as on the earth, the object would weigh approximately 6 times more on the earth than on the moon. But the mass doesn't change. Thus a 70-kg object on the moon is still a 70-kg object on the earth!