The Viking landers’ discoveries

The Viking program was the first truly successful mission to Mars, providing NASA with the first real data concerning the existence of water on the Red Planet. Photographs showed large areas of erosion, channels and grooves in rocks, as well as river valleys. These were likely caused by massive amounts of water. Each Viking lander also carried four different types of experiments to test for signs of life on Mars, which included testing for carbon and gas concentrations in the soil. The results of three of the tests proved negative, while one was ultimately inconclusive.

This panoramic image was taken by Viking 1. It reveals large rocks and sand dunes on the surface of Mars, as well as a layer of clouds below the horizon