Nov. 11, 1982 was a bittersweet day on Earth. It was Veterans Day; the Vietnam Veterans Memorial in Washington would be dedicated that weekend. And at NASA's Jet Propulsion Laboratory in Pasadena, Calif., engineers made a mistake.
They were trying to nurse along the Viking 1 lander on Mars, which had touched down there in 1976 -- and surprised them by surviving in the eternal cold there for six years, three months, and 22 days. They transmitted new commands to the ship's computer so that its batteries would hold a charge better. By accident, they erased data that helped the lander aim its antenna to Earth. Viking 1 was never heard from again.
But its record for longevity has stood. Until now.
Today the Mars Exploration Rover Opportunity, which landed on Mars on Jan. 25, 2004, becomes the longest-lasting earthly visitor ever to the Martian surface. It is still going after 2,247 "sols," or Martian days. It was designed to last for 90.
"Remember, 90 days is when the warranty runs out," said Steve Squyres, the principal investigator for Opportunity and its twin rover, Spirit, after they landed three weeks apart. "It's not when the wheels fall off."
Opportunity's six wheels have occasionally gotten stuck, and one of them will no longer steer. Its circuit boards have had to withstand the subzero temperatures of Martian winters, and another is beginning. Its solar panels, at times, have been covered with fine red silt, which made them almost useless for gathering sunlight to make electricity. Life on Mars is tough.
But the solar panels have mercifully been blown clean every time by gusts of wind, much to the relief of NASA engineers. Careful maneuvering has gotten Opportunity out of the sand -- once after six weeks of trying. Today they celebrated Opportunity's record by doing what they've been doing since 2008 -- keeping the rover on a forced march to a large crater called Endeavour, now eight miles away on the horizon.
Spirit, on the opposite side of the planet, is not doing as well. Last year its wheels broke through some crusty soil and got stuck, and after eight months of trying to move it, mission managers decided in January the little explorer had reached its final resting place.
It's not the end of the world -- Viking, after all, was not designed to move -- but it may eventually be the end of Spirit's mission. The winter solstice, the shortest day of the year, was Wednesday, May 12 (much the equivalent of December 21 in the northern hemisphere here), and the solar panels don't generate much power unless the sun is fairly high in the sky. In past winters, engineers parked the rovers on sun-facing slopes for the winter and waited it out. Now, with Spirit, they don't have that option.
So they ordered the rover, last fall, to turn almost everything off -- including its radio transmitter -- if electricity ran too low, and they haven't heard from Spirit since March 22.
It is possible that, as the days get longer, Spirit will come back to life, in which case it will take over Opportunity's record, since it landed on Mars three weeks earlier. If not, they will at some point declare its mission over, and celebrate a life well lived.
But Opportunity keeps rolling. It has traveled more than 12 miles from its landing shell, inching along with computer-aided steering to stay away from obstacles.