National Geographic : 1977 Jan
Setting foot on Mars, the Viking 1 lander rests one leg on solid, rocky ground (below), but another sinks to its "ankle" in powdery dirt (bottom). The happy accident gave scientists a close up look at two varieties of soil. Oddly enough, Like dust devils gone mad, giant dust storms rage when the orbit of Mars brings it nearest the sun. As seen in these 1973 pictures supplied by Lowell Observatory (right), such storms can envelop the planet. Scientists eagerly await a new storm expected this spring so that they can monitor it with Viking's instruments. they observed many dust-size particles here and elsewhere at the site, but no sand-size particles. One geologist speculated that grains of sand, whipped by winds up to 250 miles an hour, may be pulverized by colliding with rocks. Such windblown particles may have eroded rocks (right) at Chryse Planitia and scoured out the depression around the big rock at cen ter. When the lander touched down, small sur face fragments scattered and pitted the soil.