NASA’s Viking program launched in 1975 with two orbiter-lander pairs, a roughly $1 billion budget (about $6 billion today), and one overriding goal: find life on Mars. This deep dive traces the full lifecycle of these machines, from plutonium-238 RTG power and 40-hour bioshield baking at 111 degrees Celsius to the parachute-then-freefall landing sequence with 18 purified-hydrazine nozzles designed to avoid contaminating the very soil they came to test. Along the way, the orbiters photographed branching stream networks, chaotic terrain, and craters like Arandas that revealed a once-wet Mars with floods estimated at 10,000 times the flow of the Mississippi.

The heart of the story is the biology experiments led by Gerald Soffen. The labeled release experiment lit up as if microbes were breathing, but the gas chromatograph mass spectrometer found no organics, so Mars was declared sterile for over 30 years. Then the 2008 Phoenix lander discovered perchlorates, and the chloromethane and dichloromethane Viking dismissed as cleaning solvents turned out to match exactly what heated perchlorates produce when they destroy organics. The episode follows each spacecraft to its end, including the Viking 1 lander’s death in November 1982 from a faulty software command that pointed its antenna away from Earth.

• How radioisotope thermoelectric generators turn plutonium decay heat into steady power without solar panels
• Why the Viking camera scanned five lines per second and how engineers outran it to appear twice in one photo
• What chaotic terrain and mud-like crater ejecta revealed about subterranean ice on ancient Mars
• The labeled release versus GCMS contradiction and why perchlorates may have burned the evidence
• The 2012 and 2018 reanalyses that keep the question of Martian microbial life alive today