What the exploration of Mars tells us about Earth Available to Purchase

The success of the Viking missions has a special significance for the student of planetary evolution who considers such questions as: How did the atmosphere and oceans originate on Earth? What circumstances created the benign environments at the surface of Earth so that the first synthesis of living organisms could take place three to four billion years ago? What do continental drift, earthquakes, and other surface tectonic and volcanic activity indicate about the interior and its evolution? What stimulates a long‐term climatic change—such as an ice age? It is interesting that the experiments being performed by Viking touch on each of these questions and that data from Mars will contribute significantly to scientific progress in these fields. In essence we are trying to understand why Earth and Mars evolved so differently (see figure 1).