Orbiters:

Mariner 8 & 9 are the last pair of NASA’s Mariner Series and also the first ever orbiter marking a transition in our exploration of the red planet from flying by the planet to spending time in orbit around it. Unfortunately Mariner 8 failed in the launching stage. But Mariner 9 was launched successfully on May 30, 1971, and became the first artificial satellite of Mars when it went into orbit and functioned in Martian orbit for nearly a year. It completed its final transmission on October 27, 1972.

Mariner 9 went on to reveal a very different planet than expected. A planet with gigantic volcanoes and a grand canyon stretching 4,800 kilometers across its surface. More surprisingly, the relics of ancient riverbeds were carved in the landscape of this seemingly dry and dusty planet. Mariner 9 exceeded all primary photographic requirements by photo-mapping 100 percent of the planet's surface. The spacecraft also provided the first close-up pictures of the two small, irregular Martian moons: Phobos and Deimos.

This is a major discovery which led the world to research about presence of water on the planet. NASA in 2016 is set to launch ExoMars Orbiter. Viking 1-2, Mars Observer, Mars Climate Orbiter, 2001 Mars Odyssey, are some of the Orbiters whose objective was to find presence of life through biological experiments.

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