Astroprecipitation

Astroprecipitation, also known colloquially as space rain, was a phenomenon where the hollow areas of the interiors of large asteroids contained enough condensation to actually rain (or, in the case of comets, snow). Above some dry worlds like Tatooine where there was too little surface water to provide the population with adequate water for consumption and agriculture, specialized space stations were designed to "farm" the water from asteroids that were known to encounter astroprecipitation. The majority of moisture found inside these asteroids were completely sterile, however in some the moisture was contaminated by astromicrobes (microbial life capable of thriving in the space environment).

This phenomenon was also common in large space stations where water moisture was in overabundance.