Mariner 9 Enters Orbit Around Mars
On November 13, 1971, NASA's Mariner 9 fired its engine and entered orbit around Mars. It was the first spacecraft to orbit another planet, and it arrived while a global dust storm covered the surface.
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A Mission Rebuilt After a Failure
NASA planned two Mariner spacecraft for Mars in 1971. Mariner 8 failed shortly after launch in May 1971, when its upper stage did not work properly, and the spacecraft fell into the Atlantic Ocean. The mission plan was changed so that Mariner 9, launched on May 30, 1971, on an Atlas-Centaur rocket, would carry out the tasks planned for both, mapping the surface from orbit.
Arrival
Mariner 9 arrived at Mars in November 1971. On November 13, Pacific time, its main engine burned for about 15 minutes and slowed the spacecraft so that Mars's gravity could capture it. The spacecraft weighed about 1,000 kilograms at launch, including fuel, and was controlled from the Jet Propulsion Laboratory in Pasadena, California. It became the first spacecraft to go into orbit around another planet. Two Soviet spacecraft, Mars 2 and Mars 3, arrived later in the same month. Mars 3 landed on December 2, but it stopped sending data after about twenty seconds.
The Dust Storm
A dust storm had begun in the southern hemisphere of Mars in late September and had spread across the planet. When Mariner 9's cameras started to work, they showed an almost featureless surface, with only the summits of four volcanoes above the dust. Controllers waited, and the dust began to clear in December 1971 and by January 1972 the surface was mostly visible. The mission then went on to map the planet.
Results
Mariner 9 sent back 7,329 images before the mission ended on October 27, 1972, when its control gas ran out. It mapped about 85 percent of the surface at a resolution of between one and two kilometers. The spacecraft carried two television cameras, an ultraviolet spectrometer, an infrared spectrometer and an infrared radiometer. It showed the volcano now called Olympus Mons, the tallest known volcano in the solar system, and a canyon system more than 4,000 kilometers long, now called Valles Marineris in honor of the spacecraft. It also photographed channels that looked like dry riverbeds and the small moons Phobos and Deimos.
Mars 2 and Later Missions
Mars 2 arrived on November 27, 1971, and its landing capsule crashed on the surface, which makes it the first human-made object to reach Mars. Mariner 9's maps were used in selecting the landing sites for the two Viking landers, which reached Mars in 1976. NASA states that Mariner 9 is expected to remain in orbit around Mars for at least fifty years from the end of its mission.
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