Fifty-one years ago, on July 14, 1965, Mariner 4 flew by Mars and snapped the first close-up pictures ever taken of another planet. They were captured with a bulky television camera mounted onto the bottom of the probe, and encoded into a series of numerical values that were transmitted back to Earth. There, the message was fed through a data translator for processing—a lengthy process that could take several hours.
Impatient to behold Mars up-close for the first time, scientists at NASA's Jet Propulsion Laboratory (JPL) decided to literally take the pictures into their own hands. As soon as their probe sent along its image codes, they recreated the image with a pastel set by assigning colors to various number ranges.
And so, it turned out that the first close-up picture of another planet ever produced by humans was this handmade, paint-by-numbers sketch.
Here's a closer view of the painting, displaying the underlying numbers used to recreate it.
The image depicts a swath of Mars near its equator. From a certain vantage point, it looks like it could be an image of the Red Planet taken from the surface, with a sunrise breaking out over dusty Martian hills. But the diagonal slope in the middle of the frame actually represents the curved edge of the planet. Here's what the black-and-white digital picture looked like after it was finally processed.
Mariner 4 went on to take 21 complete pictures of Mars, along with one incomplete snapshot, as it zipped by the planet from July 14 to 15. Much like the first flybys and images of Venus, this intimate glimpse of Mars revealed a world that dashed prevailing science fiction theories about thriving alien civilizations.
Buoyed on by claims made by Victorian astronomers Giovanni Schiaparelli and Percival Lowell, who believed they had observed artificial canals on Mars' surface, the public was riveted at the idea that the planet might host intelligent life. In fact, a 1962 map of Mars made by the Air Force still included the canals as a geological feature.
Mariner 4 instead revealed Mars to be a dry, frozen planet, riddled with cosmic radiation. There were no discernable signs of any high-level extraterrestrial society, which could be viewed as either a plus or a minus, depending on which science fiction writer you choose to consult. Those who feared bloodthirsty Martians, as depicted in H.G. Wells' The War of the Worlds, may have let out a sigh of relief, while fans of Edgar Rice Burroughs' Barsoom space operas might have been disappointed to find Mars bereft of drama and romance.
In either case, Mariner 4 demystified the Red Planet by bringing it into focus for the first time.
Now, just over a half-century later, it's truly mind-boggling to consider how far the photographic exploration of Mars has come. High-resolution orbital imagery has enabled projects like Google Mars and other online Martian atlases to flourish, while Mars' many landers and rovers have sent back astonishing travel pictures from the surface of the planet.
Mariner 4 kickstarted the effort to provide close-up visuals of the major worlds of our solar system with the help of flybys and orbiters. In fact, the Mariner 4 flyby shares an anniversary with the New Horizons probe's flyby of Pluto, which went down one year ago on Thursday.
It seems fitting that exactly 50 years after a paint-by-numbers recreation yielded the first look at another planet, New Horizons' was sending high resolution images of the famous dwarf planet at the cusp of the Kuiper Belt. The pace at which spacecraft and camera technologies are being developed and refined shows no signs of slowing down, so it will be exciting to see what new vistas will be revealed by planetary photography another half-century down the line.