You're right to think about this! Here's the breakdown:

* Mass is the amount of matter in an object. It's a fundamental property and doesn't change based on location. So, the astronaut's mass remains the same on the Moon as it was on Earth.

* Weight is the force of gravity acting on an object's mass. Since the Moon's gravity is about 1/6th that of Earth's, the astronaut will weigh less on the Moon.

In summary:

* Mass stays the same.

* Weight decreases.