Sagan the exobiologist is in his element talking about the atmospheres of other planets.
He covers too much stuff in one episode as usual.
Sagan starts off with the famous Tunguska event in Siberia. He explains how it might have been the result of a meteor crashing there.
Sagan talks about the hellish atmosphere of the planet Venus and how it got to be so. He elegantly extrapolates the lessons of that cosmic reality to the fate of our own planet Earth.
Great to see the prescient Sagan express concern about the man-made greenhouse effect on Earth at a time in the '70s when clearly environmental consciousness would not have been so commonplace as it is today.
A generation after the series was made of course, the unfortunate reality is that humans are still firmly set on their suicidal course.