The images sent back to Earth as the probe flew by Mars eight months later provided our first detailed glimpse of the surface of an alien planet. And the data collected by Mariner 4 provided key information about how to safely deliver future missions to the Martian surface.
But, in the short-term, Mariner 4 was a PR disaster for NASA. The grainy, black-and-white images revealed a barren planet pockmarked with craters. It looked no different than the moon.
Nobody had seriously expected images of lush vegetation growing along the banks of water-filled canals. But Mars had captivated the public imagination for centuries. The bleak Mariner 4 images could only disappoint.
“Mars, it now appears, is a desolate world,” declared a July 30, New York Times editorial titled “Dead Planet.” “Its surface bathed in deadly radiation from outer space, it has very little atmosphere and has probably never had large bodies of water such as those in which life developed on this planet.”
The Times added that these findings refuted a draft report—published three months earlier by the National Academy of Sciences—which had stated, “Given all the evidence presently available, we believe it entirely reasonable that Mars is inhabited with living organisms and that life independently originated there."
Others piled on, including skeptics within the scientific community. Physicist Philip Abelson said that Mariner 4 provided evidence that it is “unlikely that organic chemicals are being formed on Mars or have been synthesized there in the past.” Even President Lyndon B. Johnson weighed in, saying that “life as we know it with its humanity is more unique than many have thought.”
But for scientists who endorsed the exploration of Mars, the Mariner 4 had been a tremendous success—and they bristled at the premature conclusions drawn from the initial images of the red planet.
Although the National Academy of Sciences had said it was reasonable for Mars to host living organisms, it also cautioned that those life-forms would almost certainly be microbes, which would be impossible to detect without landing on the surface.
And, as the NASA History Office explains, “The spacecraft had, after all, imaged only 1 percent of Mars at resolution so low that, had it photographed Earth, scientists examining its pictures would likely have missed all signs of terrestrial life.”
Still, NASA had been selling the public on the idea that exploring Mars promised the possibility of finding the first evidence of extraterrestrial life. The initial, bleak images of the red planet made that a harder sell. In 1967, the U.S. Congress—already frustrated by the escalating costs of the Apollo program and the Vietnam War—cut $30 million from the program to land a spacecraft on Mars.
The cuts, though, didn’t end the program. Other Mariner spacecraft would be sent to Mars over the next few years. And, in 1976, NASA finally landed the Viking spacecraft on the red planet’s surface. But, the apparent failure of the lander to detect even microbes was another deep blow to public enthusiasm for exploring the red planet.
“Since Mars offered by far the most promising habitat for extraterrestrial life in the solar system, it is now virtually certain that the Earth is the only life-bearing planet in our region of the galaxy,” said Norman Horowitz, one of Viking’s principal scientists. “We have awakened from a dream.”
But the search for life on Mars and other worlds would regain its place in the public’s imagination 20 years later. On August 7, 1996, NASA geologists held a press conference to announce the discovery of microscopic fossils in a meteorite that had originated from Mars. The widely published electron microscopic imagery of the meteorite revealed wormlike shapes that looked organic, even if scientists later concluded otherwise.
And, a week after the Mars meteorite press conference, NASA released stunning new images of Jupiter’s moon Europa taken by the Galileo spacecraft, indicating that liquid water existed beneath its cracked icy crust.
It was a testament to the power of imagery. Three decades earlier, the dull black-and-white images taken by the Mariner 4 spacecraft had prompted the New York Times to write off Mars as a “dead planet.” Now, high-resolution images of Europa and the Mars meteorite offered the tantalizing prospect of finding life on other worlds—prompting media outlets such as the New York Times to announce that the U.S. was on the verge of “A Revived Hunt for Otherworldly Organisms.”
And it was all made possible by the initial success of the Mariner 4.
Happy Red Planet Day.