I have been searching for the name of a short sci-fi film for decades. The story is about a team of scientists who figured out a way to terraform Venus by sending algae plants there in a rocket which changes the atmosphere so that humans can live there. At the end, it works, but the first people that arrive on Venus discover that the algae has killed the native Venusians, a race of worm-like creatures. The final shot (as I remember it) is of an astronaut finding a half-sphere with writing on it, and he says “it wasn't much, but it showed that they were intelligent…”
I saw it on TV in probably the late seventies or early eighties, possible as an HBO short take that they would show to fill time in between movies. Does this sound familiar to anyone?