On This Day – July 14th

The Mariner 4 spacecraft flew by Mars on July 14th 1965. Its closest approach was 9,846 km from the Martian surface at 8:00:57 p.m. (EST) at a distance from Earth of 216 Gigametres (216 billion metres) at a speed of 7 km/s (relative to Mars).

The fourth in a series of spacecraft intended for planetary exploration in a flyby mode, it was designed to conduct closeup scientific observations of Mars and to transmit these observations to Earth.

It consisted of an octagonal magnesium frame, 127 cm across a diagonal and 45.7 cm high. Four solar panels were attached to the top of the frame with an end-to-end span of 6.88 meters, including solar pressure vanes which extended from the ends. A 116.8 cm diameter high-gain parabolic antenna was mounted at the top of the frame as well. An omni-directional low-gain antenna was mounted on a seven-foot, four inch (223.5 cm) tall mast next to the high-gain antenna. The overall height of the spacecraft was 2.89 meters.

A television camera was mounted on a scan platform at the bottom of the spacecraft to obtain closeup pictures of the surface of Mars.

Images of craters and measurements of a thin atmosphere – much thinner than expected – indicating a relatively inactive planet exposed to the harshness of space, generally dissipated hopes of finding intelligent life on Mars. Life on Mars had been the subject of speculation and science fiction for centuries. If there was life on Mars, after Mariner 4 most concluded it would probably be smaller, simpler forms. The overall consensus was that, based on the 22 photographs taken by Mariner 4, one could not conclude there was no intelligent life on Mars.

In transmitting these 22 photographs and other measurement information by Mariner 4, what was the total amount of data sent back to Earth?

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