14 DAY TRIAL // Since May 6, the rover Spirit has been trapped on the surface of the Red Planet in a patch of loose soil known as Troy. The exploration robot, which has been driving backwards on only five wheels for the last three years, was climbing a 12-degree slope when its wheels got buried in the sand up to their hubcaps. After unsuccessfully trying to extract the old machine from its trap, the mission controllers at the NASA Jet Propulsion Laboratory (JPL), in Pasadena, California, decided to quit all attempts of moving it, and went on to simulate Spirit's predicament in a sandbox at the Caltech laboratory.
For five months, a test rover and a patch of sand were used to simulate Spirit and Troy, and engineers attempted all possible maneuvers to move the robot without making it further sink into the sand. Spirit's situation is actually worse on Mars, because it lies directly on top of a stone. If its underbelly were to touch the stone, then its wheels would lose all adherence to the soil, and the rover would, for all accounts and purposes, remain permanently stuck. The conclusions drawn from the simulations have been recently analyzed by an independent review panel, which recommends that it be moved as soon as possible, Nature News reports.
As the Martian winter nears Spirit's location, sunlight reaches the rover in ever-smaller quantities. At this point, the machine has energy to spare, thanks to gusts of wind that have cleared its solar panels. But, in a couple of months, that will no longer be the case. “The coming winter could pose a risk to the rover,” the Mars Exploration Rover (MER) Project Manager, JPL expert John Callas, says.
He reveals that the plan mission controllers have for Spirit is very complex and long. “It's likely that this process will take months and we don't even know if we'll be successful,” he adds. The maneuvers to extract the robot may begin as soon as November 11.
What the team plans to do is move the rover out of Troy back the way it came. Other options are not really feasible, Going forward would only sink it even further in the sand, experts believe, while allowing gravity to assist the movement downwards and to the left would take the rover “to a point of no return, deeper into a treacherous place,” Callas reveals. As it will begin its movements, it will travel about one-two centimeters per day, so that the team can make sure Spirit is not getting itself into trouble again. Safe land is about two meters (five-six feet) away, so the entire process could take months.
It may seem a bit redundant that so much effort is put into such a small machine, but the rover has become very popular over the years with both the public and its controllers. Originally scheduled to roam the surface of Mars for three months, it has endured adversities on the Red Planet since 2004, recently celebrating its 2,000th sol (Martian day) on the planet. The public has followed the evolution of the resilient rover and of its twin Opportunity with great interest, as evidenced by the stir that the JPL announcement concerning them causes even now.