Mariner 6

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Mariner 6 was launched February 2, 1969 on an Atlas-Centaur rocket. Its closest to Mars was 3431 Km on July 31, 1969.[1] [2] Mariner 6 and 7 were twin spacecraft. They were identical, but they took pictures of mostly different parts of Mars. The spacecraft was 3.35 m high and had 17,472 solar cells which provided 800 W of power near Earth and 449 W at Mars. It used a 1200 W-hr rechargeable silver-zinc battery. Mariner found its way around by tracking the sun and the star Canopus.[3] Canopus is a brightest star in the constellation Carina (the old ship Argo). Carina is visible in the southern hemisphere and is near the Small Cloud of Magellan.[4]

Scientific instruments

Ultraviolet spectroscope Infrared spectroscope Infrared Radiometer Wide-angle television camera Narrow-angle television camera[5]


The best resolution of the cameras was about 900 feet. This compares to the best resolution from Earth at the time of about 100 miles. Mariner IV pictures taken in 1965 had a resolution of two miles.[6] Images were converted to 704 lines with 935 pixels per line for a total of 658,240 pixels per image. At the time, regular television used 400 pixels per line and 525 lines. The brightness for each pixel was measured in 256 brightness levels. Camera A, the wide-angle camera, had a 52 millimeter vocal length. It covered an area with sides 10 times larger than Camera B. Camera B, the close-up camera, had a focal length of 508 millimeters, and covered an area measuring 72 by 84 km. It was able to resolve craters as small as 300 meters in diameter. Pictures were first recorded on two tape recorders. The sending of the whole set of pictures took over eight hours.[7]


Mariner 6 returned 49 pictures from a distance and 26 close encounter images. The mission showed that Mars was different than what was seen in the previous Mariner 4 mission which showed Mars to resemble the moon. A new type of surface was discovered, called “chaotic terrain.” Because of its irregular, jumbled topography, it reminded scientists of landslides on Earth.

The south polar cap was found to be made up of mostly frozen carbon dioxide (dry ice). The atmospheric pressure was measured to be between 6 and 7 mb.[8] That was very low as compared to roughly 1000 mb on the Earth. So, the air pressure on Mars is similar to that of the Earth at 100000 to 115 000 ft above sea level on the Earth. The Infrared radiometer found temperatures in the daytime hemisphere close to those expected from Earth-based studies--about 62 ° F at noon at the equator and -45 ° F at the polar-cap edge. But temperatures as low as -100 ° F were detected at night at the equator.[9] The 24 wide-angle and narrow-angle pictures from Mariner 6 crossed zones near the equator and about 20 degrees south. Images included many known light and dark features. Both Mariner 6 and Mariner 7 took pictures across the dark area of Meridiani Sinus, but at different times of the day. Nix Olympica, later named Olympus Mons, was clearly visible in the far encounter pictures.[10] [11] At the time of this mission, some still wondered about the famous “canals” observed by some from ground-based telescopes. Images of some places that should have displayed canals instead had semi-alignments of dark patches including craters with dark floors.[12]

Rocket collapse

Ten days before the launch date, the Atlas rocket began to collapse because pressure was released by a faulty switch. The mission was saved by two ground crewmen who activated pumps to prevent the complete collapse of the booster. They were later awarded Exceptional Bravery Medals from NASA.[13]


See Also

External links