NASA's second Mars rover, Opportunity, successfully landed on the Red Planet early today, shortly after mission managers announced they had homed in on the problems that had waylaid its twin, Spirit, days into its mission to search for evidence Mars once could have supported life.
"We're on Mars, everybody," Rob Manning, manager of the entry, descent and landing portion of the Mars mission, shouted as fellow scientists at NASA's Jet Propulsion Laboratory burst into wild applause upon Opportunity's landing.
The unmanned, six-wheeled rover landed at 12:05 a.m. in Meridiani Planum, NASA said. The smooth, flat plain lies 6,600 miles and halfway around the planet from where Spirit set down Jan. 3.
Meanwhile, engineers communicating with Spirit traced its troubles to part of its computer memory. Peter Theisinger, the project manager, expressed confidence that Spirit would be able to resume its scientific exploration, but said it would still take some time for the problem to be fully diagnosed and for the engineers to devise procedures to work around it.
"I think we're probably like three weeks away from driving," he said.
Managers brought stability to the six-wheeled vehicle by disabling its flash memory, which is similar to the memory digital cameras use to store pictures, said Orlando Figueroa, director of NASA's Mars exploration program.
The rovers were sent to search for vestiges of a watery past. Mars, now cold and dry, has long offered hints of a much different climate. Giant canyons slice through parts of its landscape. Elsewhere, some scientists see geological features reminiscent of shorelines.
If Mars was once a warm, wet world, as some suspect, then perhaps it could have given rise to life, and if so, then perhaps some simple microbes might yet survive deep underground where both warmth and liquid water exist.
In addition to its two rovers, NASA has the Global Surveyor and the Odyssey, and the European Space Agency has the Mars Express all in orbit around the planet. Dr. James Garvin, NASA's lead scientist for Mars exploration, said the fleet of spacecraft exploring Mars is trying to answer questions like: Where was the water? How long was it there? What has happened to it?
Spirit landed in Gusev crater, which once may have been a lake bed. Its troubles began Wednesday, as controllers were testing one of its instruments. The rover's computer crashed, and over the next two days, a cycle of rebooting and crashing repeated more than 60 times. The rover also did not shut down at night.
The rover uses both random access memory, or RAM, which loses data when power is lost, and flash memory, which retains data without power. RAM is the type of memory used in personal computers, and flash memory is what is used to store photographs in digital cameras.
Suspecting that the problem might be with the rover's flash memory, flight controllers radioed instructions for the rover to start up in what Theisinger called the "cripple mode," using only the RAM and not the flash memory. For the first time since Wednesday, the rover's software did not crash. "That communication session happened as planned," Theisinger said.
After nearly an hour talking with the rover, controllers sent a command to the rover to shut down to allow it to recharge its batteries.
Like parents checking that a child has indeed gone to bed, the controllers sent a couple of more simple commands to the rover. Unlike the day before, the rover did not answer back, "confirming that the vehicle, to the best of our ability to determine, is now sleeping," Theisinger said.
Theisinger said engineers still needed to figure out what exactly was malfunctioning, whether it is the flash memory or the software talking to the flash memory.
The Odyssey spacecraft has, from its orbital perch, detected a deposit of iron oxide the size of Oklahoma at Meridiani Planum.
What particularly interests scientists is that this type of iron oxide, hematite, usually forms in the presence of water, at least on Earth.
This image taken by the Global Surveyor spacecraft as it orbits Mars details the history of Spirit's descent and landing on Jan. 3. The two dots in the upper left are the spacecraft's backshell and parachute. To the far right, a dark streak is believed to be where the heat shield made impact. A trail of bounce marks made by the airbags as Spirit bounced to a stop can be seen in the center of the image. The white dot near the bottom is the lander. Beside it is a dot marked "surface feature localization," showing the location of the lander estimated by using sight lines to landmarks in the lander's panoramic images.
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