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50 years after Viking 1's historic Mars landing, NASA is looking to the Red Planet's skies
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- DeepHorus
Fifty years after the historic Viking 1 Mars landing, NASA is now turning its attention to exploring the Red Planet's skies. On July 20, 1976, the Viking 1 lander touched down on Chryse Planitia, marking the first successful Mars landing by the United States. This milestone, along with the Viking 2 landing on September 3, 1976, initiated the first fully successful surface mission on Mars, following the Soviet Union's Mars 3 probe, which survived only seconds after touchdown in 1971.
The Viking missions were primarily designed to search for signs of life on Mars, each carrying an orbiter and a lander equipped with three life-detection experiments. Two experiments returned negative results, but the third, called Labeled Release (LR), detected a steady stream of carbon dioxide from soil samples after nutrients were introducedāa potential indicator of microbial metabolism. However, most scientists attributed this to abiotic chemical reactions, concluding that the Viking data suggested a lifeless planet.
The ambiguous results from Viking underscored the complexity of searching for extraterrestrial life and led to a two-decade hiatus in NASA's Mars surface missions. This pause was also driven by the high cost of the Viking program and shifting priorities toward the space shuttle program. The dry spell ended in July 1997 with the Pathfinder lander, which landed about 530 miles from Viking 1 in Chryse Planitia. Pathfinder's primary goals were to demonstrate a cheaper, faster exploration method and deploy the Sojourner rover, which discovered rounded pebbles indicating past exposure to flowing water.
This discovery reshaped NASA's Mars exploration strategy, shifting from a direct life search to a "follow the water" approach. Subsequent roversāSpirit and Opportunity (landed 2004), Curiosity (2012), and Perseverance (2021)āeach found evidence of ancient aqueous environments. Curiosity and Perseverance, with advanced instruments, have detected complex organic molecules that could be remnants of past life.
Looking ahead, Perseverance is collecting Mars samples that NASA plans to return to Earth for detailed analysis, as the Viking experience highlighted the need for rigorous scrutiny to confirm life. However, the original sample-return plan was deemed too expensive, and NASA is now exploring a revised strategy to bring these samples home. The legacy of Viking endures, informing current efforts to explore Mars not only on its surface but also in its skies, as NASA seeks to answer one of humanity's oldest questions.
