The Secret History of Marxist Alien Hunters:

Trotsky’s followers declared a Fourth International that continued to push for the communist future envisioned by the early Bolsheviks. The handful of Ufologists among them took Tsiokolvsky’s assessment that “Time must pass until the average level of humankind’s development is sufficient for nonearthly dwellers to visit us” as a messianic prediction. The aliens, like communism, linger in the air, waiting for us to make the world ready for them.