No More Roving, Spirit Gets New Job as Stationary Science Platform

In a media teleconference held today, NASA announced that after several failed attempts to extricate the Mars rover Spirit from its Martian “sand trap,” the rover will become a stationary platform for further science exploration. The Mars rover team is now preparing to reposition Spirit to give it the best chance to survive the upcoming Martian winter.

“This is not a day to mourn Spirit. This is not a day of loss” said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters. Despite the fact that “its driving days are over,” the six-year-old rover will continue to make contributions to understanding Mars. As a reminder, he said that the rover program consists of two rovers, Spirit and Opportunity, and the latter is still mobile and positioned to make further discoveries in its trek between the Victoria and Endeavor craters.

John Callas, project manager of the Mars Exploration Rovers at NASA’s Jet Propulsion Laboratory (JPL), explained that the loss of functionality in Spirit’s right rear wheel represented “yet another setback” and efforts now are focused on repositioning the tilted rover towards the north in order to survive the fast-approaching Martian winter. The rover is powered by solar arrays and the Sun is in the northern sky on Mars during the winter. In the past, rover managers have adjusted to decreasing solar energy levels by pointing the rovers so their solar arrays face the Sun, but Spirit’s current position – tilted 9 south – means that decreasing solar energy levels may prompt the rover to assume a “low-power fault mode,” essentially putting it into hibernation. Callas explained that until the batteries are charged, the rover may wake up periodically, but will fall back into this inactive posture “like a polar bear hibernating.”

NASA also is concerned that the rover’s internal parts may not stay warm enough to survive harsh winter temperatures. When new, a Mars rover is designed to withstand temperatures of about -45 C. Unfortunately, Spirit finds itself in a situation where “there is no good guarantee that the rover will be able to survive.” To increase its chances, Ashley Stroupe, a rover driver at JPL, said that the focus is on maneuvering the rover to improve energy levels, increase its internal temperature, and thus reduce the time it will be in hibernation.

Meanwhile, Spirit can continue to study Mars from a stationary position as long as it has sufficient power. Steve Squyres of Cornell University, who is considered the “father” of the rovers, said that the current situation relaxes the “imperative to drive and allows us to do some science that we can’t do from a moving platform.” The three scientific initiatives he discussed are:

• Determining the internal structure of Mars’ core (either solid or liquid) by tracking the radio signal from Spirit and studying the way the planet “wobbles” on its axis;
• Characterizing the interaction between the Martian atmosphere and surface by having the rover stir up soil and watch how the surface around it changes; and
• Characterizing the swell in the vicinity of the rover and the “strange soil” that surrounds it that is particularly high in sulfates.

The possibility of this “groundbreaking” science convinces Dr. Squyres that “we got stuck here for a reason.” Welcoming the new phase of the rover’s mission, he said that “we’ve squeezed every last bit of science out of these rovers,” a strategy they hope to continue. To date, the missions have generated 91 papers in peer-reviewed journals and 407 abstracts at professional conferences.

With an average yearly cost of $20 million, the question remains whether an upcoming NASA “Senior Review” in February will recommend continued operations for the now stationary rover. Senior Reviews assess whether operating missions are producing sufficient scientific results to warrant their continuing costs. Considering their popularity, it seems unlikely that the agency would decide to terminate either Spirit or Opportunity if there is any chance of scientific return. In the meantime, the Mars rover team will try to take advantage of the next three weeks to ready Spirit for the winter, which begins between March and April. If Spirit survives the winter, it will resume its scientific studies in the Martian spring between August and September.