NASA’s Spirit Rover: Six Years on Mars, But Could the End Be Near?

NASA/JPL-CALTECH

By Craig Taylor

Published in the Winter 2009 issue of MyTekLife Magazine

The Mars exploration rovers have seen their share of dust storms, terrain challenges and mechanical troubles during their six years on the “red planet.” During what began as a three-month mission, Spirit and its twin, Opportunity, have exceeded NASA’s wildest expectations. But could Spirit have met its match?

“It’s gratifying how well these machines keep performing,” said Chris Voorhees, a mechanical systems engineer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “These rovers are tough. They faced dusty winds, power starvation and other challenges—and survived.” Alan Stern, associate administrator of NASA’s Science Mission Directorate in Washington, D.C., agreed. “These spacecraft are amazing,” Stern said.

Spirit has gathered strong evidence that ancient Mars was wetter than the planet is now. Liquid or gas flowed through cracks penetrating underground rock on the surface. These fluids may have produced conditions to support possible habitats for microbial life. “The engineering efforts that have enabled the rovers’ longevity have tremendously magnified the science return,” said Steve Squyres of Cornell University in Ithaca, N.Y. Squyres is the principal investigator for the rovers’ science payload. “All of Spirit’s most important findings, such as evidence for hot springs or steam vents, came after the prime mission,” he noted.

A typical storm on Mars can generate winds in excess of 300 mph, so whenever the rovers encounter one, it raises serious concerns among NASA’s Jet Propulsion Laboratory team members. Solar arrays on the rovers collect sunlight used to charge the rovers’ batteries, which provide electricity. Over the past several months, the solar panels have not been able to generate as much electricity as they normally would because dust storms have been interfering with the amount of sunlight that reaches the solar arrays. The storms also leave a coat of dust on the arrays that reduces the rovers’ ability to generate electricity even when the sky is clear.

Spirit has experienced “amnesia-like” symptoms five times in the last year. When this happens, the rover fails to record data from the day’s activities on its flash memory, when the rover powers down. “We still don’t have information about what causes these amnesia events,” said John Callas, project manager of the Mars Exploration Rover project at the Jet Propulsion Laboratory. “If they are intermittent and infrequent, they’re a nuisance that would set us back a day or two when they occur. If the condition becomes persistent or frequent, we will need to go to an alternate strategy that avoids depending on flash memory. We would only get data collected the same day, and any unsent data from an earlier day would be lost.”

Perhaps the toughest challenge for Spirit came last April, when the rover became embedded in soft soil at a site called Troy. The rover team suspended all driving attempts and began performing test scenarios on Earth to free the robot from its sand trap. After months of tests, the space agency began transmitting commands to the rover last November, but it does not expect the escape efforts to be quick or easy. Spirit has only five wheels working, after one stopped functioning in 2006. NASA said the task could last well into February, when an annual review of the program is scheduled. If the rover’s extraction is not successful, scientists may instead choose to leave it at its current location and continue conducting scientific readings until it dies.

Opportunity is still knocking. The twin rover continues rolling along and making groundbreaking discoveries on the other side of Mars. Luckily, it has not experienced as many challenges as Spirit.

Spirit’s survival is remarkable, considering that two thirds of previous Mars missions have failed. For scientists, working daily with these rovers can seem like a train wreck waiting to happen. They know that these rovers are on borrowed time, and it’s just a matter of time before they expire. Regardless, the anticipation of a possible breakthrough discovery must overshadow any worries they have.