Science: Racing Toward Mars

For more than five months, the three unmanned spacecraft have been racing almost neck and neck through the cold blackness of the interplanetary void. Now, as the target looms ever larger ahead of the ships, there is a growing air of anticipation in control rooms back on earth. For the three robot voyagers—one American, two Russian —should this week begin giving man his closest and most penetrating look yet at the planet Mars.

At 7:16 p.m.. E.S.T., on Saturday, Nov. 13, the U.S. entry in the Martian sweepstakes—a 1,300-lb. windmill-shaped instrument package called Mariner 9—will begin a series of crucial maneuvers. Acting...