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It was just after 4 p.m. when the images began to appear on mission control monitors. They were, by any measure, astounding: scrub plains without the scrub, prairie land without the prairie grass. The eye, schooled to scout such familiar terrain for equally familiar landmarks, scanned briefly for cactus until common sense reminded the viewer that there would be none. "The little engine that could," said Manning after the first clutch of pictures appeared, "did." Added Muirhead: "We've scored a major home run here."
That home run turned into a grand slam a few hours later when the Pathfinder team convened a press conference to unveil the panoramic color images the ship had beamed home. The pictures revealed the Marsscape with a richness and resolution the black-and-white shots couldn't. But it also revealed the problem of the obstructing airbag. It was bad enough luck that one of the mounds of fabric was bunched up in front of a petal; far worse that it was the one petal that was supposed to allow the rover egress. "The great galactic ghoul had to get us somewhere," said Donna Shirley, J.P.L.'s Mars program manager and Sojourner's designer, "and apparently the ghoul has decided to pick on the rover."
Happily, this was a problem NASA had foreseen. In J.P.L.'s so-called sandbox, a roomful of Mars-like rock and soil with a mock-up lander and rover, the engineers had rehearsed a fairly straightforward maneuver that called for Pathfinder to raise one petal, tilting the entire craft 45[degrees], retract the deflated bag further and then lower the petal. The signal to execute the maneuver was sent up shortly before Earth set over the Martian horizon, breaking the communications link until dawn; just before the connection was actually severed, a picture came back confirming that the command had been executed. Though a portion of the bag still blocked part of the petal, there was probably enough room for Sojourner to slip by.
The communication glitch between the lander and the rover took longer to resolve, but by late Saturday engineers believed they had synchronized the two systems and were cautiously declaring that that problem too was licked. Simply because Sojourner was now able to take to the Martian plains, however, did not mean that the going would be anything but painstakingly slow. For all its anthropomorphic sweetness, the plucky rover is a rather dimwitted machine. Its route from rock to rock will be programmed for it by a controller at a J.P.L. console, those instructions will be relayed to it through the Pathfinder lander and only then, if all looks safe, will the car be allowed to push off. Since even signals traveling at the speed of light take 11 minutes to cover the 119 million miles between Earth and Mars, it's impossible for controllers to stop Sojourner from running into an obstacle or over a cliff. The car thus moves excruciatingly slowly--just 2 ft. per minute--reducing the likelihood that it will stumble into trouble. Built-in gyroscopes serve as a sort of on-board vestibular system, helping the rover feel for bumps and potholes; a tracery of five laser beams helps it feel for obstructions. In addition, when Sojourner ventures out it will transmit a regular, pulselike signal back to the lander, which will serve as a sort of vehicular EKG, constantly confirming that all is well.