Overrated. Hated the casualness of astronauts retuning to their lonely colleague from what was to them a relatively short stop but was in reality years of absence. How about food and oxygen for that lonely colleague? How did he survive? In short, you cannot be so literal in SF films without bumping into inconsistencies. There are more of course. Only Kubrick’s 2001 - A Space Odyssey managed to get around these by being not too explicit, keeping the mystery.