As you read this, Sojourner, the Jet Propulsion Laboratory's pint-size Martian rover, is probably still circling the Pathfinder lander that brought it to the dusty badlands of Mars--that's what its software program tells it to do when it gets no signal from the lander. Alas, JPL officials now think it unlikely that Sojourner will ever get such a signal, for since Oct. 7 Pathfinder's transmitter has been out of commission. It was damaged, JPL believes, by temperatures 38 degrees colder than it was designed to tolerate and its demise has all but ended the Pathfinder mission.
Some might wonder why JPL engineers, who managed to protect the probes during a spectacularly tough landing on the Red Planet, couldn't have protected them from tough temperatures too. But only belatedly did JPL's engineers find that Martian temperatures can plummet to 15 degrees Fahrenheit just a few feet above the surface and fluctuate an amazing 40 degrees within a few minutes.
True to its name, the mission has found many paths to new scientific knowledge: from chemical signatures matching those in a Martian meteorite found near Earth's South Pole to remnants of once-swirling rivers and a hot iron Martian core, suggesting the planet may once have been warm and wet enough to foster life.