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Mars (space program)
I INTRODUCTION
Mars (space program), series of spacecraft that the former Union of Soviet Socialist Republics (USSR) launched toward the planet Mars in the 1960s and 1970s. The Mars program spacecraft included fly-by spacecraft, orbiters, and landers. The USSR hoped to use human fascination with Mars to win highly visible victories in the Cold War space race with the United States. Soviet engineers tried for the first close-up photographs of Mars and the first non-crash landing on Mars; although the Mars spacecraft failed to meet these goals, they did manage the first Mars flyby, the first Martian orbit, and the first Mars surface impact.
II SPACECRAFT
The Mars program started quickly, in part because of Soviet leader Nikita Khrushchev's 1960 demand for a new achievement in space. Mars 1 was actually a probe from the early Venera program and was originally designed to go to the planet Venus. It was a drum-shaped, 894-kg (1970-lb) spacecraft with an onboard camera and film-processing equipment.
Mars 2 through Mars 7 were specifically designed for the Mars program. All had the same basic spacecraft body, with different instruments or smaller spacecraft attached for different missions. Each main spacecraft weighed about 4300 kg (about 9500 lb) and was dumbbell-shaped, with two solar panels and a radio dish antenna attached to the narrower middle section. The solar panels generated electricity for the spacecraft and its instruments from sunlight (see Solar Energy). The antenna allowed the spacecraft to communicate with controllers on Earth.
Mars 2, 3, 6, and 7 carried landers. These spherical 450-kg (990-lb) spacecraft were attached to one end of the Mars spacecraft underneath a shallow, cone-shaped heat shield. The lander detached from its parent spacecraft as the main Mars craft reached the planet. The lander dropped toward Mars, protected against friction with the thin Martian atmosphere by the heat shield. Near the surface, parachutes deployed to slow the lander and the heat shield dropped away. Just above the surface, rockets slowed the lander even more and sent the parachute away from the lander. When the lander reached the surface, petal-like flaps on its top opened to reveal a camera, weather equipment, and instruments to measure the atmosphere and the Martian soil. The Mars 2 and 3 landers also carried tiny roving vehicles attached to the lander by cables. This lander system was similar to the earlier USSR Luna 9 and Luna 13 moon landers ( see Luna (space program)). The 1997 U.S. Mars Pathfinder lander also used a similar landing system.
III MISSIONS
Mars 1 left Earth in November 1962. It stopped communicating with Earth in March 1963, 100 million km (60 million mi) from Earth. The dead spacecraft became the first to fly past Mars, passing 195,000 km (121,000 mi) from the planet in June 1963. Mars 2 and Mars 3, launched in May 1971, entered Mars orbit on November 27 and December 2, 1971, respectively. They arrived at the height of the largest Martian dust storm on record; the storm probably contributed to failure of their landers. The lander of Mars 2 crashed, becoming the first human-made object on Mars. The Mars 3 lander touched down and began to transmit the first image from the Martian surface, but failed after 20 seconds. The sliver of image that the lander returned reveals no surface details. The main spacecraft from Mars 2 and Mars 3 went into orbit around Mars and photographed the planet, but the dust storms obscured most of Mars's surface.
Twenty-six months later, in 1973, the USSR attempted to upstage the U.S. Viking probes to Mars planned for 1976 by launching four spacecraft toward Mars. Mars 4 and 5 left Earth in July 1973 and Mars 6 and 7 launched the following month. They all reached Mars between February 10 and March 12, 1974. Mars 4 failed to enter an orbit around Mars. The Mars 6 and 7 spacecraft released landers and flew past the planet as planned. Mars 5 went into orbit and relayed data from the Mars 6 and 7 landers. The Mars 6 lander crashed, while the Mars 7 lander missed Mars. Unable to compete with the successful Viking spacecraft, the USSR switched emphasis to the planet Venus, where they performed many successful Venera missions.
Contributed By:
David S. F. Portree
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Mars
The most detailed information available about Mars has come from unpiloted spacecraft sent to the planet by the United States between 1964 and 1976. From this data, scientists have determined that the planet's atmosphere consists primarily of carbon dioxide, with small amounts of nitrogen, oxygen, water vapor, and other gases. Because the atmosphere is extremely thin, daily temperatures can vary as much as 100 Celsius degrees (190 Fahrenheit degrees). In general, surface temperatures are too cold and surface pressures too low for water to exist in a liquid state on Mars. The planet resembles a cold, high-altitude desert.
NASA
