On 28 October 1964, the Mariner 4 probe was launched from Cape Canaveral, the one that would become the first to successfully reach Mars, following five failed Soviet and one US attempt in previous years. Mariner 4’s mission would also be the first to send a close-up image of another planet back to Earth, in a pre-technological era (at least with respect to photographic and digital products) that celebrated the first colour TV broadcast as a major technological achievement that year.
However, the story of the first close-up image of Mars has a complex history, involving art and a box of Rembrandt coloured crayons.
NASA’s probe was the first to have the necessary photographic instrumentation on board to take images by collecting signals from space, since Mariner 2, whose mission was the exploration of Venus, was not equipped with any camera.
On 15 July 1965, 42 minutes into the flight from the maximum approach point to the planet (13,000 km), the crew activated the camera, which took 21 images in a 25-minute time span. The probe was soon taken out of orbit and it took eight hours for each image and more than ten days to transmit the data to Washington, repeating everything twice to avoid transmission errors. These transmission difficulties led scientist Richard Grumm to choose a faster method of interpreting the binary signals detected by the probe. Grumm thus bought a box of Rembrandt coloured crayons and assigned each pulse a colour shade on the red-yellow-orange scale. He stuck several strips of tape next to each other and coloured in each code according to the colour legend.
By placing all the colours side by side in this way, it was then possible to reconstruct the variations in the terrain of Mars, with the choice of tones being random, chosen from the most practical to show the variations in tone.
NASA did not want to show the result at that point, preferring to broadcast the photograph and not the drawing on TV. Despite the opposition, the drawing was broadcast by the media, thus becoming the first image of Mars on TV.
One of the most important astronomical discoveries in history was thus popularised thanks to what is to all intents and purposes an abstract pastel illustration, which like few other works of art has succeeded in imagining a new world, full of mystery and poetry. On the NASA website, there is still Dan Goods’ blog where explanations of the mission and the development in the construction of the image are available.