In the late 1970s, the Viking spacecraft sent back to Earth photographs and reports about the surface of which planet?

NASA's ambitious Viking program of the 1970s marked a monumental step in planetary exploration. The mission consisted of two identical spacecraft, Viking 1 and Viking 2, each composed of an orbiter and a lander. Both were sent to the Red Planet, with Viking 1's lander achieving the first successful, long-term mission on the Martian (Review) surface in July 1976, followed by the Viking 2 lander that September. This made them the first U.S. spacecraft to successfully land and operate there.

The Viking orbiters mapped the planet's surface in great detail, famously capturing an image of a rock formation in the Cydonia region that resembled a human face, sparking decades of speculation. This "Face on Mars" was later proven by higher-resolution images to be an optical illusion created by light and shadow. Meanwhile, the landers got to work on the ground, sending back stunning panoramic color photographs of the rocky, rust-colored landscape and conducting the first experiments designed to search for signs of microbial life in the alien soil.

While the biological experiments yielded ambiguous results that are still debated by scientists today, the Viking mission was a resounding success. It provided a wealth of data about Martian geology, atmosphere, and weather patterns that fundamentally reshaped our understanding of the planet. The mission's photographs gave humanity its first true look at the surface of Mars, paving the way for all future rovers and landers.