On Nov. 13, 1971, Mariner 9 became the first spacecraft to orbit Mars. At the time, scientists didn’t know much about the Red Planet. 

NASA had several Mars flybys before Mariner 9. Those flybys showed that Mars had a cratered surface, so some scientists thought that Mars looked just like the moon. Then Mariner 9 blew their minds.   

The Mariner 9 spacecraft.

The Mariner 9 spacecraft became the first spacecraft to orbit Mars on Nov. 13, 1971. (Image credit: NASA)

When Mariner 9 got to Mars, it arrived in the middle of a dust storm. It saw some tall structures sticking through the clouds. When the dust settled, images from Mariner 9 revealed that these structures were the tops of huge volcanoes. 

One volcano, Olympus Mons, is the tallest in the solar system. Mariner 9 also spotted an enormous canyon called Valles Marineris. This canyon is five times longer than the Grand Canyon in Arizona. 

Mariner 9 worked for one year in orbit. When it ran out of gas, NASA shut it off. But the spacecraft remains one of the most famous Mars voyagers of all time.

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Hanneke Weitering is an editor at Space.com with 10 years of experience in science journalism. She has previously written for Scholastic Classroom Magazines, MedPage Today and The Joint Institute for Computational Sciences at Oak Ridge National Laboratory. After studying physics at the University of Tennessee in her hometown of Knoxville, she earned her graduate degree in Science, Health and Environmental Reporting (SHERP) from New York University. Hanneke joined the Space.com team in 2016 as a staff writer and producer, covering topics including spaceflight and astronomy. She currently lives in Seattle, home of the Space Needle, with her cat and two snakes. In her spare time, Hanneke enjoys exploring the Rocky Mountains, basking in nature and looking for dark skies to gaze at the cosmos. 

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