The horsemen from nowhere. Paradise without memory. Silver option

The horsemen from nowhere. Soviet polar explorers working in Antarctica first stumble upon an atypical ice cover, and then meet with their doubles disappearing after a while. Soon they find a fallen American plane. His pilot says that he was attacked by pink “clouds” - gaseous objects of a reddish shade, which are rapidly moving regardless of the wind. In order to resist these aliens, or, as they were called, “riders from nowhere”, all of humanity is united.
Paradise without memory. The heroes of the “riders from nowhere”, the Soviet polar explorer Yuri Anokhin and the American pilot Donald Martin, find themselves in a strange place where people do not have the experience of modern mankind. Remembering how pink “clouds” created copies of people and objects, Anokhin and Martin guess that where they got was not the Earth at all. But they find friends here and help them, including to find skills that their creators did not give.
Silver option. Anokhin and Martin again find themselves on “cloned land” and meet with their old acquaintances from “paradise without memory”, however, fifty years have already passed here. Their friends are now elderly and significant people, but they still need the help of earthlings.
The trilogy of Alexander and Sergey Abramovs - the highest level of science fiction, which combines the scientific reliability, the brightness of images, and the fascination of the plot