Mars - The Mariner Program

The Mariner program included a series of spacecraft launched by NASA between 1962 and 1973 to explore the inner solar system (Mercury, Venus, and Mars). These were relatively low-cost missions conducted with small spacecraft launched atop Atlas-type rockets. Each spacecraft weighed between 400 and 2,200 pounds. They were designed to operate for several years and collect specific scientific data about Earth's nearest planetary neighbors.

Six of the Mariner spacecraft were scheduled for Martian missions. Two of these missions failed. In 1964 Mariner 3 malfunctioned after take-off and never made it to Mars. In 1971 Mariner 8 failed during launch. This left four successful Mars Mariner missions: Mariner 4, 6, 7, and 9.

Mariner 4

In July 1965 Mariner 4 was launched into a solar orbit and achieved the first successful flyby of Mars. A planetary flyby mission is one in which a spacecraft is put on a trajectory that takes it near enough to a planet for detailed observation, but not close enough to be pulled in by the planet's gravity.

During its flyby, Mariner 4 took nearly two dozen photos, the first close-ups ever obtained of Mars. They showed a world pock-marked with craters, probably from meteor strikes.

Mariner 6 and 7

In 1969 Mariner 6 and Mariner 7 conducted a dual mission to Mars. Both spacecraft flew by the planet, and together sent back more than 200 photos. These photos revealed that the features once thought to be canals were not canals after all. Instead, it appears that a number of small features or shadows on Mars only looked like they were aligned when viewed through telescopes from Earth. The illusion was perpetuated by a human tendency to see order in a random collection of shapes. The mystery of the canali had finally been solved.

Mariner 9

Mariner 9 turned out to be the most fruitful of the Mariner missions. In November 1971 the spacecraft went into orbit around Mars after a five and a half month flight from Earth. It was the first artificial satellite ever to be placed in orbit around the planet.

When it first arrived Mariner 9 found the entire planet engulfed in a massive dust storm. The spacecraft remained in orbit for nearly a year and returned more than 7,000 photos of the planet's surface. For the first time scientists got a good look at Mar's surface features, such as volcanoes and valleys. Mariner 9 showed geological features that looked like dry flood channels. It also captured the first close-up photos of the Martian moons Phobos and Deimos.

Scientists learned from Mariner data that Mars had virtually no magnetic field and was bombarded with ultra-violet radiation. Earth's extensive magnetic field (or magnetosphere) helps protect our planet from dangerous electromagnetic radiation traveling through space. Scientists knew that lack of such protection on Mars would make it exceedingly difficult for life to exist on the planet.