FOR five months the little spacecraft sped through the interplanetary void.
Last week, on the 157th day of an arcing, 242-million-mile journey across the solar system Mariner 6 reached its destination. In the closest approach to Mars ever achieved by a man-made object, the U.S. spacecraft flew within 2,130 miles of earth's planetary neighbor.
On command from its computer, Mariner 6's electronic gear poured out an endless stream of data from the red planet—information about the density and composition of its atmosphere and its varying surface temperatures. On board the ungainly, 850-lb. ship, whose...