The Soviet Union, later Russia, the United States, Europe, and Japan have been sending dozens of spacecraft to study one of Earth's closest neighbors in space since 1960. None of these space missions were manned, although president Bush announced plans for manned missions to Mars in January 2004 (but for now, putting people on Mars is still Science Fiction). As the name of this article implies, it's not about manned missions to Mars. Each month there will be an article focusing on one, or a few, unmanned missions to Mars. Those missions that actually made it to the red planet will be described in more details of course ;-)
Part 1: The 1960s
In the 1960s the first spacecraft were launched towards Mars. These probes had to fly past the planet or to enter orbit around Mars to take close-up photographs of the planet.
The Marsnik program
The Soviet Union's first attempt of interplanetary exploration was the Marsnik program, but both the Marsnik 1 (also known as Mars 1960A and Korabl 4, Launch Date: 10 October 1960), and the Marsnik 2 (Mars 1960B/Korabl 5, 14 October 1960) never reached Earth orbit after launch because the launcher didn't develop enough thrust. The spacecraft reached an altitude of 120 km before reentry.
The objectives of the mission were to investigate interplanetary space between Earth and Mars, to study Mars and return surface images from a flyby trajectory, and to study the effects of extended space flight on onboard instruments and provide radio communications from long distances.
Sputnik 22, Mars 1 & Sputnik 24
Sputnik 22 (also known as Mars 1962A and Korabl 11, 24 October 1962)was an attempted Mars flyby mission, presumably similar to the Mars 1 mission launched 8 days later. The Sputnik 22 broke into many pieces, some of which remained in Earth orbit for a few days. This occurred during the Cuban Missile Crisis and the debris was detected by the U.S. Ballistic Missile Early Warning System radar in Alaska and was for a while feared to be the start of a Soviet nuclear ICBM attack.
Mars 1 (also referenced as Sputnik 23, 1 November 1962) was an automatic interplanetary station launched in the direction of Mars, the first of the Soviet Mars probe program, with the intent of flying by the planet at a distance of about 11,000 km. It was designed to image the surface and send back data on cosmic radiation, micrometeoroid impacts and Mars' magnetic field, radiation environment, atmospheric structure, and possible organic compounds. After leaving Earth orbit, the spacecraft and the booster fourth stage separated and the solar panels were deployed. Early telemetry indicated that there was a leak in one of the gas valves in the orientation system so the spacecraft was transferred to gyroscopic stabilization. Sixty-one radio transmissions were held, initially at two
day intervals and later at 5 days in which a large amount of interplanetary data were collected. The probe recorded one micrometeorite strike every two minutes at altitudes ranging from 6000 to 40,000 km due to the Taurids meteor shower and also recorded similar densities at distances from 20 to 40 million km. Magnetic field intensities of 3-4 gammas with peaks as high as 6-9 gammas were measured in interplanetary space and the solar wind was detected. Measurements of cosmic rays showed that their intensity had almost doubled since 1959. The radiation zones around the Earth were detected and their magnitude confirmed. On 21 March 1963, when the spacecraft was at a distance of 106,760,000 km from Earth on its way to Mars communications ceased, probably due to failure of the spacecraft orientation system. Mars 1 closest approach to Mars occurred on June 19, 1963 at a distance of approximately 193,000 km, after which the spacecraft entered a heliocentric orbit.
Sputnik 24 (Mars 1962B/Korabl 13, 4 November 1962) was an attempted Mars lander mission. The booster/spacecraft complex broke up during the burn to transfer to Mars trajectory after it had reached Earth orbit successfully. Five large pieces were tracked by the U.S. Ballistic Missile Early Warning System. The geocentric orbit of the presumed booster decayed on 25 December 1962 and the Mars spacecraft orbit decayed and it re-entered Earth's atmosphere on January 19, 1963.
The Mariner program: Mariner 3 & 4
In 1964 NASA's Jet Propulsion Laboratory made two attempts at reaching Mars as well. Mariner 3 and Mariner 4 were identical spacecraft designed to carry out the first flybys of Mars. Mariner 3 was launched on 5 November 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly. Mariner 3 failed to reach Mars. Three weeks later, on 28 November 1964, Mariner 4 was launched successfully on an eight-month voyage to the red planet.
Mariner 4 flew past Mars on 14 July 1965, providing the first close-up photographs of another planet. The pictures, played back from a small tape recorder over a long period, showed lunar-type impact craters. Some of them seemed touched with frost in the chill Martian evening.
The Mariner program: Mariner 6 & 7
NASA continued the Mariner program with another pair of Mars flyby probes at the next launch window. In 1969, Mariner 6 and Mariner 7 completed the first dual mission to Mars, flying by over the equator and south polar regions and analyzing the Martian atmosphere and surface with remote sensors, as well as recording and relaying hundreds of pictures. By chance, both flew over cratered regions and missed both the giant northern volcanoes and the equatorial grand canyon that was discovered later. Their approach pictures did, however, show that the dark features on the surface long seen from Earth were not canals, as once decades before.
