Mars Exploration Rovers Update: Opportunity Wraps 2016, Heads into 2017 Toward 13th Anniversary

As 2016 came to an end and 2017 rang in, Opportunity was working the first leg of the ascent up the rugged western rim of Endeavour Crater on her way to an ancient gully, the next scientific tour de force down the road, and the Mars Exploration Rovers (MER) mission was closing in on its 13^thanniversary of surface operations coming up in the New Year.

The veteran robot field geologist has been making her way across and up the rocky slopes of the crater rim at Cape Tribulation since leaving Spirit Mound in November. The objective is to get to the other side of the rim and onto the flatter terrain of the Meridiani Plains that surround Endeavour’s rim. From there, the rover can cruise south to Cape Byron and enter the gully from the top, right where the MER scientists want to begin their research.

Facing steep, slippery slopes and boulder fields, Opportunity navigated through some of the most challenging terrain she has ever attempted in December, demonstrating her right robot stuff every rove of the way. “Getting up the rim is difficult stuff,” said MER Principal Investigator Steve Squyres, of Cornell University. “This is the toughest sustained climb Opportunity's ever done in nearly 13 years on Mars.”

The MER scientists believe that the gully, which is the centerpiece of Opportunity’s tenth mission extension science campaign, was carved by water during the Noachian Period some 3.7 to 4 billion years ago. This is the epoch when many planetary scientists believe Mars was more like Earth, with lakes, rivers, and perhaps even an ocean. Research at this site will mark the first time any surface mission has studied an ancient Martian gully this old up close. Whatever the rover finds, it will make history. But the first order of business is getting up and over the rim.

“We're driving to the southwest, going up hill, moving as fast as we can and not doing much else other than imaging,” said MER Deputy Principal Investigator, Ray Arvidson, of Washington University St. Louis. “We pretty much have blinders on to get up the rim and out onto the Meridiani Plains to boogey on south.”

As Opportunity clawed her way uphill, the year wound down. Using her Panoramic Camera (Pancam) and Navigation Camera (Navcam), the rover dutifully documented her surroundings along the way. Of course these images open the window on Mars for all Earthlings, but at the same time they function as science tools, the visuals on which the team now relies to confirm the rover’s locations and to chart the course ahead.

The going was tough, sometimes painfully slow, but the tough little rover kept going, putting 15, 20, or 30 meters at a time in the rear view mirror. “The rover has entered really rugged terrain and she's often near the limits of what she can do, yet she soldiers on,” said Chief of MER Engineering Bill Nelson, of the Jet Propulsion Laboratory (JPL), home to all NASA’s Mars rovers. of JPL.

Most of Opportunity’s drives in December took the rover up in elevation, but she had to juggle a number of challenges, as she will until she reaches the rim top. “The slopes are steep, anywhere from 15 to 25 degrees, and in some places the terrain has not been as firm as we might like and the rover has slid on loose rock and regolith,” said MER Project Scientist Matt Golombek, of JPL.

Then there’s the issue of power. While Opportunity’s energy levels are good enough to meet her drive and science objectives, the rover’s solar power production should be higher this time of year. “There are two issues,” said Arvidson. “The tilt of the rover as it climbs is away from the Sun makes for reduced solar radiation for the solar panels, and so we don't have as much energy as we'd like. The other issue is the crater’s rim to the west of where we are. It masks part of the sky, which is bad for power and bad for communication with Odyssey, which impacts our ability to downlink data.”

And there are the rover’s own handicaps, the “physiological” hits Opportunity has taken and adapted to since landing in 2004. Just after waking up on Mars for the first time, the robot suffered a stuck "on" heater that forces her to shut down every night. And over the years and across the miles, her right front steering actuator "froze," locking up that wheel, and her shoulder joint broke, forcing her to drive with it partially deployed. In recent years, Opportunity lost her long-term or Flash memory.

No big deals though, at least for the rover. “Aside from all that" said Nelson, “Opportunity has been performing much the same as when we took her out of the box.”

True to her MER mettle, Opportunity pressed ever onward in December, skillfully avoiding the dangers as she scaled terrain much too treacherous for her bigger, more scientifically sophisticated cousin, Curiosity, to even consider.

With the summer Sun shining on Endeavour, although not always on the rover’s solar arrays, Opportunity managed to make it through Bitterroot Valley and to the edges of Willamette Valley, “the next valley on the upward trend to get out of the crater,” as Arvidson put it. There, the mission checked off another good year, although, as Golombek noted, this mission has “never really had a bad year.”