Mariner 4 passes within 9,846 km of Mars, capturing images with resolutions up to 1 km per pixel, for a total of 634 KB of data sent back to Earth. These are the first clear images of the planet. After the initial images and other scientific data, the disappointment is palpable: we hadn’t understood anything about the Red Planet: no water, a thin atmosphere, no magnetic field, no radiation belts. But rather than waning, interest is growing.
