No, that's not true. An astronaut's mass remains the same whether they are on Earth, the Moon, or in space.

Here's why:

* Mass is the amount of matter in an object. It's a fundamental property and doesn't change with location.

* Weight, on the other hand, is the force of gravity acting on an object's mass.

Since the Moon has less gravity than Earth, an astronaut would weigh less on the Moon, but their mass would remain the same.