Question

A 65 kilogram astronaut weighs 638 newtons at the surface of earth what is the mass of the astronaut at the surface of the moon, where the acceleration due to gravity is 1.62 meters per second squared

Answer 1

Mass doesn't depend on anything else that's around you, but weight does.

The astronaut's mass is still 65 kilograms, on the moon or wherever else
she may go.

But on the moon, her weight is only 105 newtons.

Answer 2

The mass of the astronaut is still 65 kilograms. Mass is constant or doesn't change no matter where you are.