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 fou ...