[EClark1894]

There are three sources of light in the scene, Not just the one.

Forgive my pedantic nature, but the sun is indeed the only source of light in this scene (ignoring other stars). The rest is reflected light, as you say.

The bright object reflected in his visor, immediately above his own shadow but below the horizon, is an object on the moon surface fully lit by the sun - maybe the other astronaut with a camera, or the giant moon rabbit, or god....

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)