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Highlights of Early Mars Missions

In the early 1960s, both the United States and the Soviet Union began trying to get up close and personal with the red planet. NASA's Mariner 4 accomplished the first successful flyby in 1965 and sent back long-anticipated images of the martian surface. The images showed a cratered terrain reminiscent of the moon—greatly surprising those who expected to see canals built by intelligent life forms and lush vegetation. In 1969, Mariner 6 and Mariner 7 also achieved successful flybys. They returned images that showed a less moonlike surface, but a dry and barren one nonetheless.MORE »

Mariner 4

Mariner 4 image showing craters on Mars.
Image courtesy of NASA/JPL-Caltech

Flyby missions were soon replaced by orbiters and orbiter/landers. The early landers did not fare well, but orbiters including Mariner 9 and the Soviet Mars 2 and Mars 3, all launched in 1971, returned substantial data and images, showing, for example, that there were mountains almost 14 miles (22 km) high. That was astounding—in comparison, Mt. Everest is about 5.5 miles (9 km) above sea level.

The superstars of the orbiter/lander era, though, were NASA's Viking 1 and Viking 2, which arrived at Mars in 1976. The Viking orbiters imaged the entire surface of the planet, while the landers also transmitted images of the surface, analyzed surface samples for signs of life, and studied the composition of the atmosphere. Data from the Viking missions led to a good understanding of martian topography, from its huge volcanoes and deep canyons to its lava-covered plains. Although no signs of life were discovered, images from the orbiters indicated that water, a prerequisite for life as we know it, had once been present on the surface of Mars.

Another successful orbiter was the Mars Global Surveyor. Arriving at Mars in 1997, it beamed back data about the geology, magnetic field, weather and climate, and other aspects of the red planet for seven fruitful years.

The Mars Pathfinder began an exciting new chapter in Mars exploration. The landers that preceded this mission had to conduct all their experiments in just one place. But, along with a stationary lander, the Pathfinder mission introduced the first rover—the 23-pound (10-kg) Sojourner—which rolled onto the martian surface in early July 1997 and communicated with Earth until late that September. Admittedly, Sojourner couldn't rove very far—only about 30 feet (10 m)—because it had to stay in communication with the lander, the Carl Sagan Memorial Station. Yet this was a breakthrough achievement. In addition to scientific investigations of geology and the atmosphere, this mission tested the feasibility and capabilities of rover exploration, preparing the way for the much more sophisticated MER rovers Spirit and Opportunity and the mobile science laboratory rover Curiosity.

Detailed information about each of the more than 40 attempted missions to Mars can be found at NASA's Chronology of Mars Exploration.