From the surface of Mars--where the sky is salmon and Earth is a blue morning star--you probably would have noticed the spaceship coming. It may have been the noise the thing made that caught your attention; although the Martian atmosphere is spent and shredded, it's not too tenuous to carry sound. And it's certainly not too tenuous to make anything that tries to punch through it pay the price, causing the interloper to glow like a meteor as it plunged toward a touchdown somewhere on the ancient world. That you couldn't have missed.
There was, of course, no one in Mars' Ares Vallis floodplain to mark the moment when NASA's 3-ft.-tall Pathfinder spacecraft dropped into the soil of the long-dry valley. But there was a planet more than 100 million miles away filled with people who were paying heed when it landed, appropriately enough, on July 4. For the first time in 21 years, a machine shot from Earth once again stirred up the Martian dust. More important, for the first time ever, it was going to be able to keep stirring it up well after it landed. Curled up inside Pathfinder like a mechanical kangaroo joey was Sojourner, a 1-ft.-tall, 2-ft.-long robot car, known as a rover, designed to trundle away from the lander and investigate rocks all over the desert-like site.
The touchdown was not without problems. Early pictures revealed that one of the airbags that cushioned the craft during its descent had bunched up in a way that hindered the rover from leaving the lander. In addition, the computer aboard Sojourner and the one aboard Pathfinder were having trouble communicating with each other, which prevented the rover from getting the information it needed to rove beyond the immediate vicinity of the lander. But these problems, which engineers promptly set about fixing, did little to dampen the excitement when Pathfinder sent back its stunning panoramas of the eerie orange site where it had landed.
Across the U.S. and much of the world, the ship's successful arrival was greeted with the most attention accorded an otherworldly landing since, perhaps, Apollo 11 touched down on the moon 28 years ago. At the Pasadena convention center, near NASA's Jet Propulsion Laboratory, where the Pathfinder mission was being run, a standing-room-only crowd of more than 2,000 people whooped and wept as the pictures from Pathfinder streamed onto a 25-ft. screen. On the Internet, NASA sites that promised to post the pictures as soon as they became available recorded a staggering 100 million hits on Friday alone. The landing capped off a busy week in which space exploration once again energized the world: Russia launched a cargo ship carrying repair equipment for the beleaguered crew of the space station Mir, and NASA's shuttle Columbia successfully took off for a long-delayed mission.
At J.P.L., the scientists did what scientists do in such signal moments, responding with both exultant overstatement and near-surreal understatement. "This is a spectacular day," said mission manager Richard Cook. Rover scientist Henry Moore agreed, after a fashion. "Nobody," he said, without a trace of obvious irony, "has ever driven a car on Mars before."