When Mariner 9 arrived at the red planet on November 13, 1971, Mars was engulfed in a furious global dust storm that obscured the surface. The craft beamed back image after frustrating image of an erased world.
When the storm finally relented, four strange protuberances began to appear, the tops it turned out, of colossal volcanoes. The summit of the largest volcano, Olympus Mons, rose fifteen miles into the sky -- three times higher than Mt. Everest -- and its base was as wide as Montana.
Southeast near the Martian equator appeared a gargantuan canyon that cut a jagged gash in the planet twenty-five hundred miles long and, in some places, five miles deep. It was a feature that could easily swallow the entire Grand Canyon in one of its larger tributaries. Scientists dubbed the scar the Valles Marineris for the probe that discovered it.
Mariner 9 images also revealed hundreds of miles of channels and grooves east and north of the Valles Marineris that looked like they had been formed by running water. Some were shaped like dried riverbeds on Earth, but many seemed to have sprung out of nowhere, their channels equally wide from beginning to end. Both types stunned scientists. Features like these made no sense on a world as dry and cold as Mars.
In 1964 Mariner 4 had suggested that Mars was, like our Moon, simply dead and frozen, but these new discoveries indicated that Mars was more than just a crimson Moon. Mariner 9 revelations sparked new inquiries and investigations into Martian topography and even the possibility of Martian life.
