Here's why:

* No internal light source: Mars, like all planets, doesn't produce its own light. It doesn't have a nuclear fusion reaction like stars.

* Sunlight reflection: The light we see from Mars is sunlight that's reflected off its surface. The reddish color of Mars comes from iron oxide (rust) in its soil.

* Weak light source: Mars is much dimmer than the moon, because it's farther away from the sun and its surface is less reflective.

So, while Mars may seem to "emit" light, it's actually just reflecting the sun's light.