The Us Missions to Mars

Three weeks after the failure of Mariner 3, Mariner 4 was successfully launched on November 28, 1964. For its time, Mariner 4 was an amazing piece of equipment. Its basic structure was an eight-sided magnesium framework with seven electronics compartments. Four solar panels were attached to the top or sunward side of the octagon, which collected sunlight for electrical power. It contained a television camera and six other instruments, which were hoped to be used to measure conditions in space and near Mars. The instruments included radiometers, spectrometers, magnetometers, and a cosmic dust collector. The mission of Mariner 4 was to perform a simple flyby of Mars, instead of going into a complicated insertion orbit around the planet. On July 14, 1965 Mariner 4 flew over Mars at a distance of about 6,118 miles. The probe radioed back to Earth 22 television images covering approximately one percent of Mars’ surface. The blurry black-and-white images caused a stir among NASA scientists and astronomers. The surface of Mars was not at all what they expected it to be. They were expecting vegetation and water; instead they were greeted with a wasteland filled with craters, which had a great resemblance to our Moon. Mariner 4 did not detect a magnetic field surrounding Mars, which meant it did not have a big metallic core like Earth. This meant bad news for future human astronauts since cosmic radiation would be about 100 times greater than on Earth. Mariner 4’s instruments also provided scientists with the information that the atmospheric pressure on Mars is only between one and two percent that of Earth. The little atmosphere there is on Mars was detected to be mostly carbon dioxide. Liquid water could almost certainly not exist on Mars since it would quickly evaporate in the thin Marian air. Mariner 4 lasted about three years in solar orbit, much longer then was expected of the probe. Scientists were a little let down by what Mariner 4 showed them: There was no vegetation, changes in color seen by Earth-based telescopes were most likely caused by wind-blown dust storms, no canals on Mars which meant no advanced civilizations. Mars seemed to be a dead planet. But there were still many surprises to be found about Mars, which astronomers would soon discover.

Mariners 6 and 7 were next in line to travel to Mars; Mariner 5 went to Venus. Mariner 6 blasted off from Cape Canaveral on February 24, 1969 followed by Mariner 7 on March 27 of that same year. The two probes would arrive at Mars only four days apart due to the way Earth and Mars aligned. Both probes were designed from the Mariner 4 spacecraft and were boosted into space by a more powerful rocket. They carried fully automatic instrument packs that included two television cameras. They also included infrared and ultraviolet spectrometers. On July 31, 1969, Mariner 6 began the main part of its mission as it flew within 2,175 miles of Mars. Mariners 4, 6, and 7 were all flyby missions, which meant the probes would approach Mars, take their photographs and measurements, and then slip back into deep space. Mariner 6 recorded 25 close-ups of Mars’ surface which were mostly of the area around the planet’s equator, along with fifty long distance photos during the probe’s approach. Four days later, 126 photos were recorded which concentrated on the Southern Hemisphere of the planet including the South Polar Region. Mariners 6 and 7 combined to cover nearly ten percent of the planet’s surface, a big improvement from Mariner 4’s one percent of the planet. Due to better equipment and closer flybys to the surface, the photos that were sent back were clearer than Mariner 4’s. The two probes confirmed most of what Mariner 4 had revealed; that the atmosphere was very thin and that there was no trace of a magnetic field. Mariner 7 recorded the surface temperature of the South Pole at -190 degrees Fahrenheit, which led scientists to believe that Mars’ polar caps were made of sheets of frozen carbon dioxide. The photos from Mariners 6 and 7 showed many craters dotting a desert-like surface in the Southern Hemisphere of the planet. The approach pictures that were taken confirmed that the dark features on the surface seen from Earth were not canals. Just when astronomers thought they had Mars figured out, they discovered Heles, which is a large circular basin about 808 miles across. This low-lying area was surprisingly smooth with very few craters. There should have been craters in the Heles region if Mars really had been a dead planet for billions of years. Astronomers began to believe that there must have been some kind of erosion going on on the Martian surface. But what had caused the erosion? NASA realized that in order to solve this question, they would need an orbiting satellite. Two years later, this was realized.

Mariners 8 and 9 were the final pair of NASA’s