00:00 A Viking lander on Mars conducted biology experiments in '76, results of which remain debated.

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03:36 The Viking missions conducted groundbreaking biological experiments to search for life on Mars in the mid-1970s.

05:02 The Viking missions' experiments failed to detect Martian life, though they uncovered fluctuating gas levels and absorbed carbon isotopes in some tests.

06:29 Astrobiologists revisited Martian soil gas results from the Viking missions in light of subsequent evidence over two decades.

07:52 Astrobiologists reexamine Viking Mars data for life signs amid new findings.

09:16 Astrobiologists speculate that Martian life might be detectable through chirality preferences in organic molecules similar to evidence sought during Viking missions.