When NASA’s Viking 1 spacecraft touched down on Mars on July 20, 1976, it made history as the first mission to land successfully on the Red Planet and transmit images of its surface, offering humanity its first up-close look at the world.
Viking 1 landed in Chryse Planitia—Greek for “Golden Plain”—a broad, flat region near the Martian equator. Just six weeks later, Viking 2 followed suit, touching down in Utopia Planitia, a massive impact basin farther north. Together, the two landers captured over 4,000 images of the surface while their orbiters returned more than 52,000 images and mapped 97 percent of Mars’ surface at a resolution of about 300 meters (980 feet), according to NASA.
The first images the twin spacecraft sent back revealed a stark rust-colored landscape strewn with rocks eerily reminiscent of deserts on Earth. But these spacecraft were far more than robotic photographers: they were also humanity’s first attempt to directly detect life beyond Earth.
Each Viking lander carried a suite of biology experiments designed to identify signs of microbial metabolism in Martian soil—tests that became prototypes for future astrobiological missions.
“They were the first missions on Mars that included experiments specifically designed to search for life,” says Michaela Musilova, an astrobiologist who studies life in extreme environments on Earth.
Both missions were only designed to work for 90 days but survived on Mars for more than six years. “It took several decades for NASA to resume life-detection research on Mars after the Viking Mars Lander missions,” Musilova says.
A half-century later, the Viking program remains a landmark in planetary science. Here’s a look back at some of its most iconic images—and what they revealed and failed to reveal about the possibility of life on Mars.
