No rainbow could be observed from the surface of moon by the astronauts. What could be thepossible reason ?

There is lack of atmosphere on Moon, this means that droplets of water will most likely not form around the surface of the Moon. These water droplets are required in order to reflect the light internally within them for a rainbow to get visible. Also, in the absence of atmosphere there is bending of light (Refraction) due to which different colors of light bend at different angles and rainbow is formed.