* Distance from the Sun: Callisto is a moon of Jupiter, which orbits much farther from the Sun than Earth does. This means it receives significantly less sunlight.

* Jupiter's shadow: Callisto spends a portion of its time in Jupiter's shadow, further reducing the amount of sunlight it receives.

* Callisto's surface: Callisto's surface is dark and heavily cratered, reflecting very little light.

To put it into perspective:

* Callisto receives about 1/25th the amount of sunlight that Earth does.

* The intensity of sunlight on Callisto is similar to the intensity of twilight on Earth.

Imagine standing on Callisto's surface. The sun would appear as a very bright star in the sky, but the overall lighting would be very dim and shadowy. It would be difficult to see anything clearly without artificial light sources.