Mars Rovers Still Roving After All These Years

By Linda Orlando

The two golf cart-sized vehicles that set down on the surface of Mars nearly two years ago have set all sorts of records since they began their journey, and they have achieved unprecedented success far beyond the hopes of NASA and stargazers everywhere. Their biggest achievement was finding geological evidence that water once flowed on the planet.

The first rover, Spirit, landed on Mars on January 3, 2004. The second rover, Opportunity, arrived three weeks later on January 24. The two were expected to last for just a few months, but they are still roving along after traveling a total of seven miles for the past two years. To put that seemingly miniscule distance in perspective, try driving your car for seven minutes on Mars, where the average temperature in 67 degrees below zero and winds of engine-choking dust can reach 100 mph. Researchers were pleasantly surprised to discover that instead of the whirling dust devils causing problems, they actually helped by blowing away dust particles covering the rovers’ solar panels, thereby keeping their electricity fully charged.

Steven Squyres of Cornell University is the Mars mission’s principal researcher. "These rovers are living on borrowed time," he said. "We’re so past warranty on them. You try to push them hard every day because we’re living day-to-day." The rovers are six-wheeled vehicles about the size of golf carts, with robotic arms and cameras, and each has its own foibles and quirks just like cars on Earth. The first rover, Spirit, became the first robot to scale a hill on another planet, climbing up to the top of Husband Hill, an outcropping as tall as the Statue of Liberty. Opportunity rose to the challenge and outperformed its predecessor by making the first exciting discovery of their mission—finding evidence of water having existed on the planet eons ago.

This journey of these two rovers is the fourth mission to land on the surface of Mars. The stationary robot Viking 1 had the longest run, operating from 1976 to 1982. NASA’s Sojourner was the first rover to be sent on a mission, but it stayed close to the lander it arrived on. The mission of Spirit and Opportunity is the first time any probe has traveled extensively around the Martian landscape, which is very rocky and not inviting to man-made vehicles. But in the two years they have traveled, Spirit has traveled over three miles and beamed back over 70,000 images, including self-portraits and panoramic images of the surface of Mars. Opportunity has transmitted over 58,000 images during its four-mile trek.

The journey of the rovers hasn’t been without its roadblocks; Spirit had a problem with a cantankerous front wheel and Opportunity got stuck in the sand for several weeks before NASA engineers were able to free it. In November the robotic arm on Opportunity failed while it attempted to extend to examine a rocky outcropping, and it took engineers two weeks to fix it. But despite small technical stalls from time to time, the rovers have been an unqualified success and NASA has extended their mission three times, spending more than $900 million on the mission.

Spirit is now descending Husband Hill, headed for a basin that researchers believe might hold more clues to the red planet’s geological past. Opportunity is on its way to Victoria Crater, a huge depression in the planet’s surface that might hold even more exciting secrets to discover. John Grotzinger, a science team member from MIT, is one of the many researchers whose excitement about the project has continued to increase with each new discovery. "Rock layers are the barcode of Mars history," Grotzinger said. "Every time we encounter new layers, it’s another piece of the puzzle."