THE VIKING plan to explore Mars was not simple. Two spacecraft were dispatched at different times in the launch window, and put into different orbits about the planet. After they scouted landing sites, some of which were rejected as too risky, two soft-landers were detached and both- incredibly- managed safe entry and set about making detailed surface measurements and returning dramatic, close-in photographs of another world. Meanwhile the two Orbiters continued to encircle Mars, sending photographic coverage of almost the entire planet. In concept, Viking was ambitious to the edge of audacity.
It was amazingly successful. The Landers revealed a desolate, rocky world, provided fascinating chemical information about the surface, and served as weather stations emplaced tens of millions of miles from Earth. The 0rbiters have given us more than 46 000 images so far of the planetary surface, in all seasons, lighting, and weather. In a way Viking still continues even though the major mission has ended, for one of the radioisotope-powered Landers still checks in, and at this writing one Orbiter still has enough attitude control gas on board to continue working.
This volume presents a selection from the orbital images provide by one of the longest-running successes in the history of space exploration. They show Mars as an extremely diverse planet. As you study them, it is difficult to avoid the conclusion that, though Viking contributed immeasurably to breaking the code of the Martian enigma, we do not yet confidently understand its dramatic and turbulent past.
May 9, 1980