Tuesday, August 7, 2007

Mariner 4

Credit: NASA

The early 1960s saw a considerable amount of activity - and failure - in the first attempts to send a spacecraft to Mars. In October 1960, the Soviet Union launched two spacecraft, Marsnik 1 and 2, both of which failed when their third stage pumps failed to develop enough thrust to start ignition. The two spacecraft reached an altitude of about 120 km before re-entering the Earth's atmosphere. In 1962, the USSR launched three spacecraft, Sputnik 22, Mars 1 and Sputnik 24, all of which also failed, although Mars 1 was able to transmit some data back to earth for a little over 4.5 months before going silent.

In 1964, the USSR launched Zond 1964A and the US sent their first Mars mission, Mariner 3, both of which also failed. (Mariner 1 and Mariner 2 were missions to Venus, not to Mars.) Twenty-three days after Mariner 3 was launched, Mariner 4 lifted off.

Like Mariner 3, Mariner 4's mission was to fly past Mars and send back scientific observations back to Earth. In addition to a TV camera, Mariner 4 also carried a number of other instruments, including a helium magnetometer, dust detector, and a cosmic-ray telescope. It was the TV camera, however, which caused the biggest stir. The camera took a total of 22 pictures (21 complete pictures and one partial picture made up of 21 lines). The camera showed a barren, cratered landscape, driving home the last nail in the coffin for the fantasy of intelligent life on Mars.

The above image is the 11th photograph of the 22 taken by Mariner 4, and is considered to be one of the best images from that spacecraft. The crater was named "Mariner," after the Mariner 4 probe. Mariner has a diameter of 151 km, and is located at 35 South, 164 West. Running from the lower left corner of the frame through the bottom of the crater is a linear ridge which is part of Sirenum Fossae. The image was taken from 12,600 km and covers 250 km by 254 km. North is up.

Mariner 4 was not expected to survive much longer than the eight months it took to reach Mars; however, the spacecraft actually lasted about three years in solar orbit, continuing long-term studies of the solar wind environment and making coordinated measurements with Mariner 5, a sister ship launched to Venus in 1967.

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