From technology editor Alexis Madrigal:
News of possible liquid salt water on Mars this week has inspired renewed speculation about the Red Planet. In this NASA film from 1982, Sagan describes the earliest evidence of water on Mars -- streambeds apparently carved by running water -- and why those streambeds are now empty.
The rest of the film can be seen at the Internet Archive.
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Kasia Cieplak-Mayr von Baldegg is the former executive producer and general manager of Atlantic Studios at The Atlantic.