Viking 1

Viking was the largest and most expensive thing NASA had ever sent to another planet: two orbiters and two landers, about 1.06 billion dollars in 1970s money, built around a question that Mariner 4 had made look naive in 1965 and Mariner 9 had made respectable again in 1971. Is there life on Mars? NASA's Langley Research Center managed the project, the Jet Propulsion Laboratory built the orbiters from the Mariner 9 design and flew the mission, and Martin Marietta built the landers. Each orbiter-lander pair weighed 3,527 kg fully fuelled, the heaviest planetary spacecraft the United States had launched. Because the landers were going to test Martian soil for life, they had to arrive sterile: each was sealed inside a pressurised bioshield and baked in nitrogen at 232 degrees Fahrenheit, about 111 Celsius, for forty hours, and engineers spent years screening more than 40,000 parts in 232 types of material for ones that would survive the oven. The launch campaign was less orderly than the hardware. The first attempt, on 11 August 1975, was scrubbed when a thrust vector control valve on the Titan IIIE-Centaur misbehaved in tests. The second, on 14 August, was called off when the orbiter's batteries read 9 volts instead of 37. Rather than lose more of the launch window, managers swapped the two vehicles. The spacecraft built as Viking B flew as Viking 1 on 20 August 1975 at 21:22 UT, and the one built as Viking A became Viking 2. NSSDCA's catalogue still carries "Viking-B Lander" among Viking 1's alternate names.

Viking 1 reached Mars orbit on 19 June 1976 after a 304-day cruise, and then did something no Mars mission had done before: it looked before it leapt. The landing had been aimed at 4 July 1976, the American bicentennial, but the orbiter's own pictures of the chosen ground in Chryse Planitia showed terrain far rougher than Earth-based radar had suggested. The site certification effort, written up afterwards in Science by Harold Masursky and Norman Crabill, was drastically lengthened while a survivable site was hunted for, and the landing slipped by more than two weeks. On 20 July 1976, by coincidence the seventh anniversary of Apollo 11, the lander separated at 08:51 UT and fell through the thin air behind an aeroshell, then under a 16 metre parachute deployed at about 6 km, then on three throttleable hydrazine engines lit at 1.5 km. Each engine sprayed its exhaust through eighteen small nozzles, a showerhead arrangement chosen so that the landing would not cook the soil the biology package was about to sample. Touchdown came at 11:53:06 UT spacecraft time, about 28 km from the aim point, on a plain of rocks and drifted dust. Mars was then roughly 340 million km away, so the confirmation did not reach Earth until 12:12 UT, twelve minutes past eight in the morning on the United States east coast and twelve minutes past five in the morning in Pasadena. Twenty five seconds after landing, camera 2 began scanning the first picture: the ground beside a footpad, sharp, sunlit, on another planet, and still there when the scan finished.

What the landers found was a world that was chemically busy and biologically ambiguous. Instruments on the aeroshell gave the first in-place measurement of Martian air, about 95.3 per cent carbon dioxide, 2.7 per cent nitrogen and 1.6 per cent argon, and the meteorology booms recorded a surface pressure that rose and fell by roughly a third across the year as carbon dioxide froze onto one polar cap and came back off the other. Then there was the biology package. Three experiments, gas exchange, labeled release and pyrolytic release, went looking for metabolism. Labeled release returned exactly the signal a biologist would want: add nutrient tagged with carbon-14 to Martian soil, get tagged gas back. But the gas chromatograph mass spectrometer, the instrument meant to find the organic molecules any life would have to be made of, found essentially none. Most of the team concluded that a powerful chemical oxidant was eating the nutrient, and that nothing living was involved. That reading held for thirty years and then got sharper. NASA's Phoenix lander found perchlorate in Martian soil in 2008, and Rafael Navarro-Gonzalez and colleagues showed in 2010 that perchlorate heated in a Viking-style oven would burn organics and generate precisely the chlorinated compounds Viking had reported. A 2025 Icarus paper by Chris McKay, Richard Quinn and Carol Stoker lays out the current mainstream position: perchlorate chemistry accounts for both the missing organics and the reactive soil. It is not unanimous. Steven Benner and colleagues argued in Astrobiology in February 2026 that the field has been misreading Viking for fifty years.

Viking 1 was built for 90 days on Mars and worked for more than six years. Its orbiter went first. Running low on the nitrogen that held its attitude, it spent July 1980 on a series of four propulsion-system test burns, on the 15th, 17th, 18th and 31st, which raised its orbit far enough that, under planetary quarantine rules, it would not fall on Mars and contaminate the ground before 2019, and on 7 August 1980 at 20:15 GMT the Deep Space Station at Madrid commanded its transmitters off, on revolution 1489, after 1,488 orbits and 36,622 pictures. The lander carried on alone as the Viking Lander Monitor Mission, waking about once a week to dump stored weather and imaging data, its stored program set to keep the high-gain antenna tracking Earth until December 1994. Jim Tillman's group at the University of Washington rebuilt enough of JPL's mission operations computing to keep the data flowing, work that Tillman credits with stretching the lander mission from about sol 1,000 to sol 2,245. By 1982 three of its four nickel-cadmium batteries were badly degraded, and after an expert review in August JPL prepared a new charging strategy. The command sequence that implemented it was written into the memory locations occupied by the high-gain antenna pointing parameters, on which both the uplink and the downlink depended. Canberra sent it on 19 November 1982. On 20 November the expected downlink did not appear and the project declared a spacecraft emergency; on 26 November engineers worked out what had happened. Four months of manual commanding at 80 kilowatts followed, aimed at a dish that was no longer pointed at Earth. Nothing answered.

Nobody laid eyes on the lander again until 22 November 2006, when the HiRISE camera on Mars Reconnaissance Orbiter resolved a roughly three metre object at 22.273 N, 312.054 E in western Chryse and confirmed it by overlaying contours derived from the lander's own panoramas, along with likely positions for the heat shield, backshell and parachute. Its 2,245-sol surface record had by then stood for twenty-four years, and it stood another three and a half, until Opportunity passed it on 19 May 2010. In January 1981 the lander had been renamed the Thomas A. Mutch Memorial Station for the imaging team leader who disappeared climbing in the Himalayas in 1980, and a stainless steel plaque was cast to be fixed to it by whoever gets there first. On 18 May 1984 NASA administrator James M. Beggs handed that plaque to the National Air and Space Museum and, in the same letter, transferred ownership of the lander on Mars to the museum, which is how a Smithsonian annual report came to describe itself as interplanetary. The plaque is still in Washington. The lander is still in Chryse, its dish aimed at a patch of sky that is not Earth, with four decades of dust on it, and its fiftieth landing anniversary passed on 20 July 2026.