On November 14, 1971, U.S. spacecraft Mariner 9 was the first spacecraft to orbit another planet – only narrowly beating the Soviets’s Mars 2 and Mars 3, which both arrived within a month. After months of dust storms it managed to send back clear pictures of Mars’ surface.
Mariner 9 was designed to continue the atmospheric studies and map over 70% of the Martian surface from the lowest altitude of 1500 kilometers and at the highest resolutions of any previous Mars missions. With the help of an infrared radiometer, Mariner 9 was supposed to detect heat sources in search of evidence of volcanic activity in order to study temporal changes in the Martian atmosphere and surface.
Mariner 9 was the first spacecraft to orbit another planet and carried a large instrument payload. When the unmanned space probe arrived at Mars the scientists were suprised with a thick atmosphere and “a planet-wide robe of dust, the largest storm ever observed.” They re-programmed Mariner to delay imagine of the surface for a couple of months until the dust settled. Mariner 9 was able to significantly contribute to the collection of Mars science, including understanding of the existence of several huge high-altitude volcanoes of the Tharsis Bulge that gradually became visible as the dust storm abated. After 349 days in orbit, Mariner 9 had transmitted 7.329 images, covering 85% of Mars’ surface, whereas previous flyby missions had returned less than one thousand images covering only a small portion of the planetary surface. The delivered images revealed river beds large crater as well as massive volcanoes including Olympus Mons, the largest known volcano in our Solar System.
The enormous Valles Marineris canyon system is named after Mariner 9 in honor of its achievements. After depleting its supply of attitude control gas, the spacecraft was turned off on October 27, 1972. Mariner 9 remains a derelict satellite in Mars orbit. Mariner 9 is expected to remain in orbit until approximately 2022, when the spacecraft is projected to enter the Martian atmosphere and either burn up or crash into the planet’s surface.
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