The moon is one of our celestial objects. It is our Earth's moon. It is the reason for many gravity related events, such as tidal waves, tsunamis, and etc. The moon has it's own gravity! There is no atmosphere on the moon.
It would be major for the astronauts on the moon. It wouldn't be as major for the moon itself and the people down on earth. There wouldn't be any atmosphere to interfere with the explosion, so there would be no mushroom cloud and instant just the fireball growing. The fireball would eventually become exhausted, and disappear. Astronauts close enough to look at it would be fried! It would be visible from our Earth, with a visible and beautiful glow.
It's simple. It provides time-telling, light, and tides. Animals depend on the moon when migrating. It gives light to the night. Certain ancient people used the moon to tell time.