Postcards from Mars

On November 28, 1964, NASA launched Mariner 4 toward Mars. Seven and a half months later, on July 14, 1965, the spacecraft flew within 6,118 miles of the Martian surface and took 22 photographs. They were the first close-up images of another planet. What they showed was devastating: a barren, cratered landscape that looked more like the Moon than anything science fiction had imagined. The canals were a myth. The civilizations were fantasy. Mars was dead.

Mariner 4 was small -- about 575 pounds, carrying a television camera and six science instruments. The camera took pictures during a 25-minute window as the spacecraft sped past. The images were stored on a tape recorder and transmitted back to Earth over the following days using a signal so weak it took eight hours to send a single photograph. Engineers at JPL were so impatient they hand-colored the first image with pastels as the data strips came in, creating a paint-by-numbers version of Mars before the computers could process it.

The photographs showed craters, not canals. The atmosphere was thinner than expected, the surface pressure only about one percent of Earth's. There was no liquid water. The romantic Mars of Percival Lowell and H.G. Wells was replaced by something harsher and lonelier. But the mission also found geological hints that water might have once flowed on the surface, a clue that would shape every Mars mission that followed.

Mariner 4 cost about 83 million dollars and sent back 22 grainy photographs. That was enough to change humanity's image of its nearest neighbor. The mission proved that you don't need a perfect instrument to make a perfect point. Sometimes 22 photographs are all it takes to kill a myth and start a science.

engineers checking the mariner 4 spacecraft before its launch — the mission that sent back the first close-up photographs of mars. source: wikimedia commons