Mass is the amount of matter in any object. This remains constant no matter where you take the object. Thus if Aya's mass is 37 kg on earth it will be 37 kg anywhere else in the universe.
Don't confuse mass and weight. Weight is a force which is the result of a gravitational acceleration acting on an object's mass. So everytime the value of the acceleration of gravity changes, the object's weight will also change. This is even true on earth. If you move farther from the center of the earth (by climbing a mountain) your weight will be slightly less.
Mass characterizes the number of atomic components that an object is made of. Mass is invariant with gravity. This means that on earth or the moon, an objects mass does not change. The objects percieved weight in a gravitaitonal field can change, however.
So if Aya's mass is 37 kg on earth, it is also 37 kg on the moon.
Mass is a measure of matter contained in any object. The mass of an object may be differentiated from its weight, which is related to the pull exerted upon the object due to force of gravity. Since the force of gravity is almost same anywhere on surface of the earth, we often us the measure of weight as a measure of mass also. However, the force of gravity on earth and moon are substantially different. The force of gravity on moon is much less than that on earth. As a result for the same mass the weight of an object will be less on moon than on the earth. However, please note that the mass of the object does not change with change in gravitational force. Therefore, Aya's mass will continue to be the same on earth and moon.
Though we use the same names like kilogram for units of mass and unit of weight, these are two different variables.
The mass is not changing from place to place in the universe. Mass is relating to the content of matter of a rigid body. What changes from place to place is the weight of an object which is due to the property of the gravitational attraction between any two bodies in the universe. The gravitational attraction depends on the mass of two bodies and the distance between the centre of masses of the bodies.
The gravitational attraction on a planet is thus the main force between an object considering prediminant huge mass of the planet compared to any other surrounding relatively smaller objects.
g = 9.81 m/s^2 is gravitational acceleration on the surface of earth approximately .
g' = 1.62m/s on the surface of the moon.
Weight force = m*gravitational acceleration.
So on earth Aya weighs = Aya' mass*g = 37*9.81N. So Aya has the force of weight of 362.97 Newton on earth.
On moon she weighs 37*1.62 N= 59.94N.Therefore Aya weighs 5.94 N on moon which is roughly 1/6 th of the weight on earth.