Missions to Mars

Perhaps the most fascinating target for space probes has been the planet Mars. Often the closest planet to Earth, Mars has a thin cold, and dry atmosphere and a rocky, desertlike surface. The first mission to fly by Mars was Mariner 4, a U.S. project, in 1965. The pictures it took showed that the landscape of Mars also has many craters. There were none of the canals that some observers thought they saw from Earth, but it turned out that dust storms in the Martian atmosphere hid many interesting features from Mariner 4. A few years later, Mariner 9 was the first spaceship to orbit another planet, and it discovered both a canyon 2,500 miles (4,000 km) long on Mars and Olympus Mons, the largest mountain in the Solar System. There were also dry riverbeds that made it look like water had once flowed on Mars—but there was no sign of any water today.

Many of the projects devoted to Mars were twin spacecraft, one to land on the surface and the other to orbit the planet. None of the Soviet Union’s missions were completely successful. Neither was the Nozomi probe, sent by Japan, or the Beagle 2 lander from the European Space Agency (ESA). But NASA’s Viking 1 and Viking 2 twin probes in 1976 succeeded, returning a wealth of data about the atmosphere and the soil. In the 1990s, the United States also sent Sojourner, a lander, and Pathfinder, a small, wheeled robot that rolled away from Sojourner.
Even more amazing results have come from the two rovers, named Spirit and Opportunity, which made their way to Mars in January 2004. They traveled thousands of yards across the landscape and even discovered a meteorite lying on the surface! Inter- esting small rocks, nicknamed blueberries, were also discovered. They almost certainly prove there was once a lot of water on Mars. Although none of the spacecraft that landed on Mars have found any evidence of life there, finding out where the water went may yet reveal some wonderful secrets. Then, in 2005, ESA’s Mars Express orbiter took a lovely photograph showing a small lake in a crater—water—but frozen solid. A future mission will drill below the surface to look for water that might be frozen and mixed in with the soil.