Mariner 8 failed at launch, but Mariner 9 did make it to Mars. This spacecraft carried a similar instrument payload to Mariners 6 and 7, but it had a markedly more powerful propulsion system. When it reached Mars on November 14, 1971, it used that system to slow its velocity, becoming the first spacecraft to go into orbit around the planet. After 349 days, Mariner 9 had sent back 7,329 images covering more than 80% of Mars' surface. The mission revealed river beds, craters, extinct volcanoes, and canyons, including the massive Valles Marineris that dwarfs the Grand Canyon, and showed clear evidence that wind, water erosion, and weather had physically shaped Mars in its past. These results from Mariner 9 ultimately narrowed down the landing site for Vikings 1 and 2, the first two probes that reached the surface in 1976.