Final answer:
The aerial (or atmospheric) perspective, which relies on Earth's atmospheric conditions, would be absent on the moon. Other depth cues like linear perspective, interposition, and texture gradient would still be present, albeit with potential differences due to the lunar environment.
Step-by-step explanation:
The depth cue that would be unavailable to an astronaut walking on the moon's surface is aerial perspective. This perspective is also known as atmospheric perspective, and it is based on the principle that objects further away appear smaller, grayer, and less distinct, often due to water vapor and other elements in Earth's atmosphere creating a haze. Since the moon lacks an atmosphere, it would not provide this particular depth cue. Linear perspective, interposition, and texture gradient would still be available as depth cues on the moon. However, the texture gradient may differ from Earth's due to the moon's unique surface composition and lighting conditions.