Why do deep craters near the Moon's poles create conditions suitable for water ice survival?

The Sun hangs perpetually low on the horizon near the Moon's poles, meaning certain deep craters never receive direct sunlight.

The unique illumination conditions near the Moon's poles are responsible for creating the necessary cryogenic environment for water ice preservation. Due to the shallow angle at which the Sun strikes the terrain near the poles, the Sun appears to hang very low on the horizon, almost skimming the surface. This geometry ensures that certain deep craters cast permanent shadows where direct solar radiation never penetrates. These areas remain shielded from solar energy year-round, maintaining extreme cold that prevents volatile compounds like water ice from sublimating into space, thus allowing them to be trapped and preserved for potentially billions of years.